@conference {
	title = {Cooperative Hypothesis Testing by Two Observers with Asymmetric Information},
	author = {Raghavan, Aneesh., Baras, John S.},
	year = {2019},
	month = {07/2019},
	address = {Akko, Israel},
	booktitle = {27th Mediterranean Conference on Control \& Automation}
}
@conference {
	title = {Trust is the Cure to Distributed Consensus with Adversaries},
	author = { Liu, Xiangyang},
	year = {2019},
	month = {07/2019},
	address = {Akko, Israel},
	booktitle = {27th Mediterranean Conference on Control \& Automation}
}
@conference {
	title = {Patient prioritization in cardiac catheterization labs},
	author = {Apergi, Lida A., Baras, John S.},
	year = {2019},
	month = {06/2019},
	address = {Dublin ,Ireland},
	booktitle = {30th EUROPEAN CONFERENCE ON OPERATIONAL RESEARCH}
}
@conference {
	title = {Trust-Aware Service Chain Embedding},
	author = {Torkzaban, Nariman, Papagianni, Chrysa. , Baras, John S.},
	year = {2019},
	month = {06/2019},
	address = {Rome, Italy},
	booktitle = {The Third IEEE International Workshop on Software Defined Networks and Network Function Virtualization}
}
@conference {
	title = {Multi-Appointment Outpatient Scheduling in Cardiology},
	author = {Apergi, Lida A., Baras, John S., Golden, Bruce L., Wood, Kenneth.},
	year = {2019},
	month = {05/2019},
	address = {Orlando, Florida, USA},
	booktitle = {IISE Annual Conference and Expo 2019}
}
@conference {
	title = {Planning and Runtime Monitoring of Robotic Manipulator using Metric Interval Temporal Logic},
	author = {Zhenyu Lin},
	year = {2019},
	month = {04/2019},
	address = {Miami Beach, Florida},
	booktitle = {2019 Annual IEEE International Systems Conference (SysCon)}
}
@conference {
	title = {Event-triggered Feedback Control for Signal Temporal Logic Tasks},
	author = {Lindemann, Lars., Maity, Dipankar., Baras, John S., Dimarogonas,Dimos.},
	year = {2018},
	month = {12/2018},
	address = {Miami, Florida},
	booktitle = { Conference on Decision and Control (CDC)2018}
}
@conference {
	title = {"State-dependent Data Queuing in Shared-resource Networked Control Systems"},
	author = {Mamduhi, Mohammad H., Baras, John S., Johansson, Karl Henrik., Hirche, Sandra.},
	year = {2018},
	month = {12/2018},
	abstract = {In the design of shared resource networked control systems (NCSs), resource managers play an important role to
appropriately allocate limited resources across the distributedsystem. They are often used to fairly distribute the limited bandwidth among the medium-sharing entities at the expense of delaying or discarding unnecessary data samples. Considering the rapidly growing volume of information that need to be exchanged, a relevant scenario for efficient resource management is state-dependent data buffering through network queues. In this paper, we propose state-dependent data buffering for shared-resource NCSs, such that both buffer input and output can be adjusted depending on the real-time conditions of the control systems and the communication network. We consider that the transmission decisions at the sensor side are taken by event-based schedulers, and that those data eventually sent for transmission are queued and processed, depending on the available communication resource. To improve the buffer service, we propose a state-dependent buffer discharge method, based on real-time feedback from the communication network. We derive sufficient stability conditions under which the overall NCS with the proposed cross-layer transmission scheme is stable in mean-square sense. Moreover, we show performance improvements resulting from our proposed design in comparison with its state-independent counterpart.},
	address = {Miami Beach, Florida},
	booktitle = {Conference on Decision and Control (CDC)2018}
}
@conference {
	title = {Non-Commutative Probability Models in Human Decision Making: Binary Hypothesis Testing},
	author = {Raghavan, Aneesh., Baras, John S.},
	year = {2018},
	month = {12/2018},
	abstract = {In this paper, we consider the binary hypothesis testing problem, as the simplest human
decision making problem, using a von-Neumann non-commutative probability framework.
We present two approaches to this decision making problem. In the rst approach, we represent
the available data as coming from measurements modeled via projection valued measures (PVM)
and retrieve the results of the underlying detection problem solved using classical probability
models. In the second approach, we represent the measurements using positive operator valued
measures (POVM). We prove that the minimum probability of error achieved in the second
approach is the same as in the rst approach.},
	address = {Miami, Florida},
	booktitle = {2nd IFAc Conference on Cyber-Physical \& Human-Systems (CPHS)2018}
}
@conference {
	title = {Optimal Decision Fusion Under Order Effects},
	author = {Ehsan Nekouei, Wei, Jieqiang., John S. Baras, Mikael Skoglund, Johansson, Karl Henrik.},
	year = {2018},
	month = {12/2018},
	abstract = {This paper studies an optimal decision fusion problem with a group of human decision makers when an order effect is present. The order effect refers to situations wherein the process of decision making by a human is affected by the order of decisions. In our set-up, all human decision makers, called observers, receive the same data which is generated by a common but unknown hypothesis. Then, each observer independently generates a sequence of decisions which are modeled by employing noncommutative probabilistic models of the data and their relation to the unknown hypothesis. The use of non-commutative probability models is motivated by recent psychological studies which indicate that these non-commutative probability models are more suitable for capturing the order effect in human decision making, compared with the classical probability model. A central decision maker (CDM) receives (possibly a subset of) the observers{\textquoteright} decisions and decides on the true hypothesis. The considered problem becomes an optimal decision fusion problem with observations modeled using a non-commutative (Von Neumann) probability model. The structure of the optimal decision rule at the CDM is studied under two scenarios. In the first scenario, the CDM receives the entire history of the observers{\textquoteright} decisions whereas in the second scenario, the CDM receives only the last decision of each observer. The perfromance of the optimal fusion rule is numerically evaluated and compared with the optimal fusion rule derived when using a classical probability model.},
	address = {Miami, Florida},
	booktitle = {2nd IFAc Conference on Cyber-Physical \& Human-Systems (CPHS)2018}
}
@conference {
	title = {Towards Reduced-State Service Chaining with Source Routing},
	author = {Papagianni, Chrysa. , Panagiotis, Papadimitriou., John S. Baras},
	year = {2018},
	month = {11/2018},
	abstract = {The widespread adoption of Network Function Virtualizatio~ (NFV) poses significant dataplane scalability limitations in datacenters (DC), as switches will be required to maintain a large amount of forwarding state for service chaining. This problem is exacerbated by the small Forwarding Information Base (FIB) of commodity switches, which are typically deployed in NFV infrastructures.
To mitigate this problem, we present a routing fabric that combines source routing with pathlet switching in order to (i) achieve state reduction and (ii) provide support for longer paths, hence, meeting the increased hop-count requirement of service chains. Coupling the proposed source routing fabric with a service chain embedding method, we achieve significant gains in terms of FIB consumption, request acceptance, and revenue generation.},
	address = {Rome, Italy},
	booktitle = {14th International Conference on Network and Service Management (NSM)2018}
}
@conference {
	title = {SysML Executable Model of an Energy-Efficient House and Trade-Off Analysis},
	author = {Cawasji, Kersasp., Baras, John S.},
	year = {2018},
	month = {10/2018},
	abstract = {With the growing complexity of energy efficient buildings, the methods of modeling and simulating such structures must account for monitoring several thousand design parameters across multiple diverse domains. As a result, modeling tools are now very specific to their respective domains and are growing more and more incongruous with each other. This calls for a way to integrate multiple modeling tools in the effort to create a single, large model capable of encapsulating data from multiple, different models. Thus, in this paper, different methods to perform an integration with Systems Modeling Language (SysML) and a simulation tool were identified, described and evaluated. Then, a new method was developed and discussed. Finally, the new method was demonstrated by developing a SysML executable model of a simple two-room house. Using the Functional Mock-up Interface (FMI) standard, the SysML model is integrated with a Modelica model, and a simulation is run in Simulink. Finally, a tradeoff analysis was performed for the purpose of design space exploration.},
	address = {Rome, Italy},
	booktitle = {2018 IEEE International Systems Engineering Symposium (ISSE)}
}
@conference {
	title = {Model-Based Systems Engineering Applied to the Trajectory Planning for Autonomous Vehicles},
	author = {Bansal,Siddharth., Alimardani, Fatemeh., Baras, John S.},
	year = {2018},
	month = {10/2018},
	abstract = {Passing maneuver is a complex driving maneuver critical to success of autonomous vehicles. It becomes more challenging in two-way roads. In this study, a passing scenario with three vehicles is considered where car 1, an autonomous vehicle (AV), is moving behind car 2 (human-driven) in the same lane and car 3 (human-driven) is part of the oncoming traffic in the adjacent lane. The primary goal is to develop a framework to analyze measurement-based decision-making strategies for the AV satisfying driving safety constraints and while considering collaboration amongst drivers. The problem is structured using SysML to build a modular architecture with clearly defined interfaces and allocated behaviors. Mathematical models have been modeled in MATLAB. The integrated model of the car passing problem was then executed in MATLAB to study the effect of collaboration on safety of car 1 if car 1 decides to pass. It was observed that the controller of car 1 made the correct decision whether to execute the passing maneuver or not, based on the feasibility of the maneuver. When car 1 decided to pass, the collaboration between the autonomous vehicle and the humandriven vehicles reduced the crashes if car 1{\textquoteright}s decision was erroneous due to measurement noise. The work demonstrates how a Model-Based Systems Engineering approach can be used in the context of the car passing problem to manage complexity, developing virtual prototypes for analysis and deriving design requirements for autonomous vehicles.},
	address = {Rome, Italy},
	booktitle = {2018 IEEE International Systems Engineering Symposium (ISSE)}
}
@conference {
	title = {A Stochastic programming approach for multi-appointment outpatient scheduling in cardiology},
	author = {Apergi, Lida A., Baras, John S., Wood, Kenneth., Golden, Bruce L.},
	year = {2018},
	month = {07/2018},
	abstract = {This research tackles the problem of multi-appointment scheduling in a healthcare environment with limited resources. Considering elective outpatient procedures in the cardiology department of a large medical center, where patients have to visit the hospital on multiple occasions to go through the required tests and treatments, a model is designed and developed towards optimizing the allocation of the available resources to the patients. The objective is to minimize the weighted combination of the number of visits that the patients have to make to the hospital until the completion of the program they are going through and the time that the outpatients spend in the hospital while waiting in between appointments. Constraints taken into account include the availability of the patients and the required resources, the sequencing of the procedures, and the recovery time that should be provided to patients between procedures. Stochastic programming techniques are applied to optimize the scheduling decisions over time.},
	address = {Valencia, Spain},
	booktitle = {29th European Conference on Operational Research}
}
@conference {
	title = {Event-Triggered Controller Synthesis for Dynamical Systems withTemporal Logic Constraints},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2018},
	month = {06/2018},
	abstract = {In this work, we propose an event-triggered control framework for dynamical systems with temporal logical constraints. Event-triggered control methodologies have proven to be very efficient in reducing sensing, communication and computation costs. When a continuous feedback control is replaced with an event-triggered strategy, the corresponding state trajectories also differ. In a system with logical constraints, such small deviation in the trajectory might lead to unsatisfiability of the logical constraints. In this work, we develop an approach where we ensure that the event-triggered state trajectory is confined within an ~tube of the ideal trajectory associated with the continuous state feedback. At the same time, we will ensure satisfiability of the logical constraints as well. Furthermore, we show that the proposed method works for delayed systems as long as the delay is bounded by a certain quantity.},
	address = {Milwaukee USA},
	booktitle = {2018 American Control Conference},
	pages = {pg. 1134-1138}
}
@conference {
	title = {Covariance-Based Transmission Power Control for Estimation over Wireless Sensor Networks},
	author = {Soleymani, Touraj., Zoppi, Samuel, Vilgelm, Mikhail, Hirche, Sandra., kellerer, Wolfgang, John S. Baras},
	year = {2018},
	month = {06/2018},
	abstract = {In this study, we would like to design a transmission power control mechanism for minimizing the transmit power of a wireless sensor node subject to a constraint on the quality of estimation at a remote estimator. In particular, we measure the estimation distortion by a mean square error function, and model the transmit power as a function of the packet success rate using the IEEE 802.15.4 standard which was formed for the specification of low-data-rate and low-power wireless communication. We formulate the problem with an infinite horizon discounted cost function. We show that there is a separation between the designs of the optimal estimator and optimal transmit power policy. Then, we use dynamic programming to characterize the optimal transmit power policy in terms of the estimation error covariance. Finally, we propose approximate value iteration as an approximation algorithm to calculate a near-optimal transmit power policy.},
	address = {Limassol, Cyprus},
	booktitle = {European Control Conference 2018},
	pages = {pp. 857-862}
}
@conference {
	title = {Stochastic Control Formulation of The Car Overtake Problem},
	author = {Raghavan, Aneesh., Wei, Jieqiang., Baras, John S., Johansson, Karl Henrik.},
	year = {2018},
	month = {06/2018},
	abstract = {~In this paper, we consider the classic car overtake problem. There are three cars, two moving along the same direction in the same lane while the third car moves in the direction opposite to that of the first two cars in the adjacent lane. The objective of the trailing car is to overtake the car in front of it avoiding collision with the other cars in the scenario. The information available to the trailing car is the relative position, relative velocities with respect to other cars and its position and past actions. The relative position and relative velocity information is corrupted by noise. Given this information, the car needs to make a decision as to whether it wants to overtake or not. We present a control algorithm for the car which minimizes the probability of collision with both the cars. We also present the results obtained by simulating the above scenario with the control algorithm. Through simulations we study the effect of the variance of the measurement noise and the time at which the decision is made on the probability of collision.},
	address = {Savona, Italy},
	booktitle = {15th IFAC Symposium on Control in Transportation Systems},
	pages = {pp. 124-129}
}
@conference {
	title = {LQG Control via Wireless sensor Networks with Minimal Transmission Power},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2018},
	month = {05/2018},
	abstract = {This study concerns control of dynamical systems via wireless sensor nodes with minimal transmission power. In particular, we jointly design a controller and a transmission power control mechanism that adjusts the transmit power of a wireless sensor node. We develop a framework for achieving the minimum expected transmit power required for a specific level of the LQG control performance.We model the communication channel between the wireless sensor node and the controller by an AWGN channel compatible with the IEEE 802.15.4 standard, which was formed for the specification of low-data-rate and low-power wireless communication. We use dynamic programming to characterize the optimal policies, and show that there exists a separation between the designs of the optimal estimator, optimal controller, and optimal transmission power control mechanism.},
	address = {Sorrento Coast, Italy},
	booktitle = {14th Workshop on Discrete Event systems(WODES 2018)},
	pages = {pp. 62-67}
}
@conference {
	title = {Rethinking Service Chain Embedding for Cellular Network Slicing},
	author = {Papagianni, Chrysa. , Panagiotis, Papadimitriou., Baras, John S.},
	year = {2018},
	month = {05/2018},
	abstract = {5G is set out to address the business contexts of 2020 and beyond, by enabling new network and service capabilities. The industry consensus is that 5G will facilitate ubiquitous connectivity seamlessly integrating wireless technologies and complementary communication networks while operators will be capable of providing networks on a need-for-service basis. Furthermore, there is a need for operators to exploit new revenue sources and break the traditional business model of a single network infrastructure ownership, by supporting multi-tenancy. Network slicing can provide a solution towards this end; it is considered a key for meeting 5G{\textquoteright}s diverse requirements, including future-proof scalability and flexibility.

Provisioning and management of network slices in the transition from Long Term Evolution (LTE) to the emerging 5G systems poses the need for the mapping of service chains that express traffic and processing requirements of LTE slices. In this respect, we follow a different approach to the service chain mapping problem, promoting virtualized network function (NF) sharing among multiple service chains that are associated with a certain network slice. Using mixed-integer linear programming formulations, we show that our approach leads to reduced NF State and management overhead, compared to the common resource allocation practice in virtualized Radio Access Networks.},
	address = {Zurich, Switzerland},
	booktitle = {IFIP Networking 2018},
	pages = {253-261}
}
@conference {
	title = {Linear Quadratic Games with Costly Measurements},
	author = {Maity, Dipankar., Anastasopoulos, Achilleas. , Baras, John S.},
	year = {2017},
	month = {12/2017},
	abstract = {In this work we consider a stochastic linear quadratic two-player game.The state measurements are observed through a switched noiseless communication link. Each player incurs a finite cost every time the link is established to get measurements. Along with the usual control action, each player is equipped with a switching action to control the communication link. The measurements help to improve the estimate and hence reduce the quadratic cost, but at the same time the cost is increased due to switching. We study the subgame perfect equilibrium control and switching strategies for the players. We show that the problem can be solved in a two-step process by solving two dynamic programming problems. The first step corresponds to solving a dynamic programming for the control strategy and the second step involves solving another dynamic programming for the switching strategy.},
	address = {Melbourne, Australia},
	booktitle = {56th IEEE Conference on Decision and Control (CDC 2017)},
	pages = {pp. 6223-6228}
}
@conference {
	title = {Event-Triggered Output-Feedback H$\infty$ Control with Minimum Directed Information},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2017},
	month = {12/2017},
	abstract = {In this paper, the H$\infty$ control problem with minimum information exchange between a plant and a remote controller is considered. For transmission of the measured outputs, an event-triggering mechanism is proposed. We measure the transferred information satisfying the causality condition by the directed information, and measure the H$\infty$ control performance by the L2-gain. We achieve the minimum directed information required for a guaranteed level of control performance. In particular, corresponding to the worst case disturbances, we develop a filter with a recursive variable, and show that the optimal control policy is a linear function of this recursive variable. Finally, we define the value of information, and determine the structure of the optimal sampling policy based on the value of information.
~},
	address = {Melbourne, Australia},
	booktitle = {56th IEEE Conference on Decision and Control (CDC 2017)},
	pages = {pp. 6088-6094}
}
@conference {
	title = {Algebraic-Graphical Approach for Signed Dynamical Networks},
	author = {Shi, Guodong., Altafini, Claudio., Baras, John S.},
	year = {2017},
	month = {12/2017},
	abstract = {A signed network is a network with each link associated with a positive or negative sign. Models for nodes interacting over such signed networks, where two types of interactions are defined along the positive and negative links, respectively, arise from various biological, social, political, and economical systems. Starting from standard consensus dynamics, there are two basic types of negative interactions along negative links, namely state flipping or relative-state flipping. In this paper, we provide an algebraic-graphical method serving as a systematic tool of studying these dynamics over signed networks. Utilizing generalized Perron-Frobenius theory, graph theory, and elementary algebraic recursions, we show this method is useful to establish a series of basic convergence results for dynamics over signed networks.
~},
	address = {Melbourne, Australia},
	booktitle = {56th IEEE Conference on Decision and Control (CDC 2017)},
	pages = {pp. 2009-2014}
}
@conference {
	title = {Collaborative Sequential Detection of Gaussian Models from Observed Data and The Value of Information Exchanged},
	author = {Raghavan, Aneesh., Baras, John S.},
	year = {2017},
	month = {12/2017},
	abstract = {We consider the problem of detecting which Gaussian model generates an observed time series data. We consider as possible generative models two linear systems driven by white Gaussian noise with Gaussian initial conditions. We also consider two collaborating observers. The observers observe a function of the state of the systems. Using these observations, the aim is to find which one of the two Gaussian models has generated the observations. For each observer we formulate a sequential hypothesis testing problem. Each observer computes its own likelihood ratio based on its own observations.Using the likelihood ratio, each observer performs sequential probability ratio test (SPRT) to arrive at its decision on the hypothesis. Taking into account the random and asymmetric stopping times of the two observers, we present a consensus algorithm which guarantees asymptotic convergence to the true hypothesis. The consensus algorithm involves exchange of information, i.e., the decision of the observers. Through simulations, the {\textquotedblleft}value{\textquotedblright} of the information exchanged, probability of error and average time to consensus are computed.~},
	address = {Melbourne, Australia},
	booktitle = {56th IEEE Conference on Decision and Control (CDC 2017)},
	pages = {pp. 15-20}
}
@conference {
	title = {Networked H$\infty$ Control with Minimum Directed Information},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2017},
	month = {12/2017},
	address = {Melbourne, Australia},
	booktitle = {56th IEEE Conference on Decision and Control (CDC 2017)}
}
@conference {
	title = {Crowdsourcing with Multi-Dimensional Trust and Active Learning},
	author = {Liu, Xiangyang., Baras, John S.},
	year = {2017},
	month = {12/2017},
	abstract = {We consider a typical crowdsourcing task that aggregates input from multiple workers as a problem in information fusion. To cope with the issue of noisy and sometimes malicious input from users, trust is used to model workers expertise. We propose a probabilistic model to jointly infer multi-dimensional trust of workers, multi-domain properties of questions,and true labels of questions.Our model is flexible and extensible to incorporate metadata associated with questions. To show that, we further propose two extended models, one of which handles input tasks with real-valued features and the other handles tasks with text features by incorporating topic models. In order to decrease entropies and reduce error rates more quickly with fewer annotations from workers, we further propose strategies for selecting which questions to ask and which workers to assign the questions to based on multidimension characteristics of questions and workers trust values in those dimensions. We evaluate our models and algorithms on real-world data sets. These results can be applied for fusion of information from multiple data sources like sensors, human input, machine learning results, or a hybrid of them.~},
	address = {Melbourne, Australia},
	booktitle = {56th IEEE Conference on Decision and Control (CDC 2017)},
	pages = {pp. 3224-3231}
}
@conference {
	title = {An Approximate Dynamic Programming Approach for Patient and Process Prioritization in A Hospital Environment},
	author = {Apergi, Lida A., Baras, John S., Golden, Bruce L., Wood, Kenneth.},
	year = {2017},
	month = {10/2017},
	abstract = {This research tackles the problem of patient and process prioritization in a healthcare environment with limited resources. Considering the medical cardiology department of a large medical center, a holistic model is designed and developed towards optimizing the decisions of allocating the available resources to the patients in order to minimize patients{\textquoteright} waiting costs. Approximate Dynamic Programming techniques are applied to optimize the aforementioned decisions over time, as well as capture the heterogeneity of the patients.},
	address = {Houston Texas},
	booktitle = {INFORMS Annual Meeting 2017}
}
@conference {
	title = {IoT and 5G as enablers for Networked Human-Cyber-Physical Systems},
	author = {Baras, John S., Papagianni, Chrysa. },
	year = {2017},
	month = {08/2017},
	abstract = {Cyber-Physical Systems (CPS) are transformative technologies for managing interconnected systems between a system{\textquoteright}s physical assets and computational capabilities. Several novel opportunities and research challenges emerge in CPS from the core domains of CPS, the physical and the cyber world and their interdependencies, as well as other domains such as networking and distributed systems. Specifically, CPS are frequently distributed and often they are either large-scale or require elasticity of scale as utilization fluctuates. Most of CPS are networked, typically via the Internet or the cloud, or via special logical or physical networks, leading s to networked CPS (Net-CPS). Examples include modern factories, modern enterprises, heterogeneous wireless networks, heterogeneous wireless sensor networks, social networks over the Internet, the Industrial Internet Consortium (IIC), the Internet of Things (IoT). Furthermore, we now live and work in a networked immersed world. That is humans are now important components of these networked systems. We call the resulting systems networked human-cyber- physical systems (Net-HCPS). The main thesis of the presentation is that the emerging technologies of IoT and 5G are indispensable enablers of both Net-CPS and Net-HCPS. We illustrate with several ubiquitous examples. The requirements for Net-HCPS design and performance evaluation suggest that a promising idea is to make the communication networks linking the components in Net-CPS, both programmable and flexible to changing operating conditions. This is precisely where Software Defined Networks (SDN) offers exciting new opportunities. SDN is a new paradigm that provides unprecedented flexibility via dynamic, programmatic (re) configuration of network resources using open standard interfaces. Neither 5G or IoT can be efficiently and predictably implemented without Software Defined Wireless Networks (SDWN) and Network Function Virtualization (NFV). We describe how these interdependencies lead us to a Software-Defined Architecture for Net-CPS and Net-HCPS. We describe critical implications of this work for the Industrial Internet and Industrie 4.0. Our work is in line with major shifts and R\&amp;amp;D interests in major communication companies (including Nokia Bell labs, Qualcomm, Ericsson, AT\&amp;amp;T). Finally, it has huge implications on smart cities viewed as Net-HCPS.},
	address = {Reston, VA},
	booktitle = {IEEE 5G Summit}
}
@conference {
	title = {Detection of Markov Chain Models from Observed Data Using Binary Hypothesis Testing and Consensus:},
	author = {Raghavan, Aneesh., Baras, John S.},
	year = {2017},
	month = {07/2017},
	abstract = {In this paper, we consider the problem of detecting which Markov chain model generates observed time series data. We consider two Markov chains. The state of the Markov chain cannot be observed directly, only a function of the state can be observed. Using these observations, the aim is to find which of the two Markov chains has generated the observations. We consider two observers. Each observer observes a function of the state of the Markov chains. We formulate a binary hypothesis testing problem for each observer. Each observer makes a decision on the hypothesis based on its observations. Then Observer 1 communicates its decision to Observer 2 and vice-versa. If the decisions are the same, then a consensus has been achieved. If their decisions are different then the binary hypothesis testing problem is continued. This process is repeated until consensus has been achieved. We solve the binary hypothesis testing problem and prove the convergence of the consensus algorithm. The {\textquotedblleft}value{\textquotedblright} of the information gained through 1-bit communication is discussed along with simulation results.},
	address = {Toulouse, France},
	booktitle = {IFAC 2017 World Conference},
	pages = {pp. 3944-3949}
}
@conference {
	title = {Value of Information in Minimum-Rate LQG Control},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2017},
	month = {07/2017},
	abstract = {This study concerns fundamental limitations in control of mobile cyber-physical systems. In these systems, communication between a node and its base station due to limited power of the node is asymmetrical in terms of bandwidth and signal-to-noise ratio. The framework we develop in this paper is for partially observed linear quadratic Gaussian (LQG) control over communication networks in which the forward channel transporting measurements is modeled by a zero-delay packet-deletion channel and the feedback channel transporting control inputs is assumed ideal. Making use of dynamic programming, we characterize the optimal control and the optimal sampling policies that achieve the minimum data rate required for a guaranteed level of control performance. In particular, we prove that in the presence of event driven sampling the adopted filter is optimal and the separation principle between control and estimation holds. We show that the optimal control policy is a certainty equivalent policy and the optimal sampling policy is a threshold policy expressed in terms of the value of information. Furthermore, we prove that the value of information is a quadratic function of the innovation.},
	address = {Toulouse, France},
	booktitle = {IFAC 2017 World Conference}
}
@conference {
	title = {Linear Quadratic Stochastic Differential Games under Asymmetric Value of Information},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2017},
	month = {07/2017},
	abstract = {This paper considers a variant of two-player linear quadratic stochastic differential games. In this framework, none of the players have access to the state observations for all the time, which restricts the possibility of continuous feedback strategies. However, they can observe the state intermittently at discrete time instances by paying some finite cost. Having on demand costly measurements ensure that open-loop strategy is not the only strategy for this game. The individual cost functions for each player explicitly incorporate the value of information and the asymmetry that comes along with different costs of state observation for different players. We study the structural properties of the Nash equilibrium for this particular class of problems when the cost of observation is finite and positive. We show that the game problem simplifies into two decoupled game problems: one for deciding the control strategies, and the other for deciding the observation acquisition times. The study also reveals that under two extreme cases -cost of observation being 0 or $\infty$- the strategies coincide with feedback and open-loop strategies respectively.},
	address = {Toulouse, France},
	booktitle = {IFAC 2017 World Conference},
	pages = {pp. 9287-9292}
}
@conference {
	title = {Asymptotic Policies for Stochastic Differential Linear Quadratic Games with Intermittent State Feedback},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2017},
	month = {07/2017},
	abstract = {In this paper, we consider infinite horizon linear quadratic stochastic differential games where the games are neither open-loop nor closed-loop. The state of the game dynamics is measured only when a certain switch is closed. The switch requires unanimous operation by the players, and continuum state measurements are not possible. There is an upper bound on the number of times the switch can be closed. Each player is given a quadratic cost function and the objective of each player is to design a switching strategy and a control strategy in order to optimize their respective cost function. We investigate the Nash control strategy and optimal switching policy for this game with two different cost structures: discounted cost and average-time cost.},
	address = {Valletta, Malta},
	booktitle = {25th Mediterranean Conference on Control and Automation (MED 2017)},
	pages = {pp. 117-122}
}
@conference {
	title = {Optimization and Resource Management in NOMA Wireless Networks Supporting Real and Non-real Time Service Bundling},
	author = {Vamvakas, Panagiotis, Tsiropoulou, Eirini Eleni., Papavassiliou, Symeon., Baras, John S.},
	year = {2017},
	month = {07/2017},
	abstract = {In this paper, the problem of joint users{\textquoteright} uplink transmission power and rate allocation in NOMA wireless networks is studied, under the scenario that each user is simultaneously requesting multiple services. Each user is associated with a twovariable utility function that represents his satisfaction from his allocated resources (i.e., power and rate). In order to appropriately reflect the combined needs of the user for bundling different types of services under the same common umbrella, user{\textquoteright}s utility function consists of two parts while different percentages are adopted by each user for each part in order to express his need for real and nonreal-time services. The joint resource allocation problem is directly confronted as a two-variable optimization problem and formulated as a non-cooperative game. The theory of S-modular multivariable games is adopted towards determining the Nash equilibrium point of the game. A distributed, iterative and low complexity algorithm for computing game{\textquoteright}s Nash equilibrium is introduced, while updating user{\textquoteright}s uplink transmission power and rate at the same step. Detailed numerical results exhibit the ability of the proposed framework to simultaneously satisfy diverse multiple services requested by the same user.},
	address = {Crete, Greece},
	booktitle = {22nd IEEE Symposium on Computers and Communication (ISCC 2017)},
	pages = {pp. 699-705}
}
@conference {
	title = {Fast Task-Specific Target Detection via Graph Based Constraints Representation and Checking},
	author = {Luan, Wentao., Yang, Yezhou., Fermuller, Cornelia., Baras, John S.},
	year = {2017},
	month = {05/2017},
	abstract = {We present a framework for fast target detection in real-world robotics applications. Considering that an intelligent agent attends to a task-specific object target during execution, our goal is to detect the object efficiently. We propose the concept of early recognition, which influences the candidate proposal process to achieve fast and reliable detection performance. To check the target constraints efficiently, we put forward a novel policy which generates a sub-optimal checking order, and we prove that it has bounded time cost compared to the optimal checking sequence, which is not achievable in polynomial time. Experiments on two different scenarios: 1) rigid object and 2) non-rigid body part detection validate our pipeline. To show that our method is widely applicable, we further present a human-robot interaction system based on our non-rigid body part detection.},
	address = {Singapore},
	booktitle = {2017 IEEE International Conference on Robotics and Automation},
	pages = {pp.  3984-3991},
	organization = {Marina Bay Sands Convection Center}
}
@conference {
	title = {Stochastic Differential Linear-Quadratic Games with Intermittent Asymmetric Observations},
	author = {Maity, Dipankar., Raghavan, Aneesh., Baras, John S.},
	year = {2017},
	month = {05/2017},
	abstract = {In this paper, we consider a two-players stochastic linear quadratic game framework. The game is partially observed and each player has their own private observation. The challenge is that none of the players has access to the continuum observations, rather they can access their respective observations at discrete time instances by operating a switch unanimously. The operation of the switch is costly and hence the gathering of the observations are costly. Each player is equipped with finite memory and she can only use the latest observation to construct the control strategy. The private observations of the players lead to a source of asymmetry in this game. Moreover, the players have different costs for operating the switch, which is another source of asymmetry. We study the structural properties of the Nash equilibrium for this particular class of problems and then we finally show that the switching problem simplifies to a bi-objective optimization problem.},
	address = {Seattle, WA},
	booktitle = {2017 American Control Conference},
	pages = {pp. 3670-3675},
	organization = {Sheraton Seattle Hotel}
}
@conference {
	title = {Reachability Analysis for Linear Hybrid Set-Dynamics Driven by Random Convex Compact Sets},
	author = {Matei, Ion., Baras, John S.},
	year = {2017},
	month = {05/2017},
	abstract = {This paper studies linear set-dynamics driven by random convex compact sets (RCCSs), where the parameter matrix evolves according to an underlying Markovian random process taking values in a finite set. We derive dynamics of the expectations of the associated reach sets. We establish that such expectations evolve according to coupled deterministic set{\textendash}dynamics. We provide sufficient conditions for the convergence of the reach sets expectations. We also give conditions under which the reach sets remain asymptotically bounded with probability one. As an illustrative example, we apply our results to evaluate the expectations of the reach sets associated to the position of a quadrotor},
	address = {Seattle, WA},
	booktitle = {2017 American Control Conference},
	pages = {pp.  1765-1770},
	organization = {Sheraton Seattle Hotel}
}
@conference {
	title = {Autonomous Relocation Strategies for Cells on Wheels in Environments with Prohibited Areas},
	author = {Rabieekenari, Ladan., Sayrafian, Kamran., Baras, John S.},
	year = {2017},
	month = {05/2017},
	abstract = {Public safety organizations increasingly rely on wireless technology for their mission critical communication during disaster response operations. In such situations, a communication network could face much higher traffic demands compared to its normal operation. Given the limited capacity of base stations in the network, such peak traffic scenarios could lead to high blocking probability or equivalently service interruptions during critical communications. At the same time, networking infrastructure can breakdown during a disaster. Proper deployment of mobile cells - Cells on Wheels - can help to enhance the network coverage or accommodate excess traffic in areas with high concentration of users. In addition, an intelligent relocation strategy can be used to efficiently adapt the cell locations to match variations in the spatial distribution of the traffic. In practical scenarios, these mobile base stations may not be able to relocate to all positions within the target field. Such prohibited areas introduce additional constraints on designing an intelligent relocation strategy. In this paper, we propose a decentralized relocation algorithm that enables mobile cells to adapt their positions in response to potentially changing traffic patterns in a field with prohibited areas. Extensive simulations show considerable improvement in supporting spatially variable traffic throughout the target field.},
	address = {Paris, France},
	booktitle = {IEEE International Conference on Communications (ICC 2017)},
	pages = {pp.1-6}
}
@conference {
	title = {Interest, Energy and Physical-Aware Coalition Formation and Resource Allocation in Smart IoT Applications},
	author = {Tsiropoulou, Eirini Eleni., Paruchuri, S.T, Baras, John S.},
	year = {2017},
	month = {03/2017},
	abstract = {In this paper, the problem of coalition formation among Machine-to-Machine (M2M) communication type devices and the resource management problem is addressed. Each M2M device is characterized by its energy availability, as well as by differentiated interests to communicate with other devices based on the Internet of Things (IoT) application that they jointly serve. Physical ties among devices also exist based on their physical distance proximity and communication channel quality. Those three factors: energy availability, interest, and physical ties, are considered into the coalition formation process and the coalition-head selection. Each M2M device is associated with a holistic utility function, which appropriately represents its degree of satisfaction with respect to Quality of Service (QoS) pre requisites fulfillment. Given the created coalitions among the M2M devices, a distributed power control framework is proposed towards determining each M2M device{\textquoteright}s optimal transmission power in order to fulfill its QoS prerequisites. The performance of the proposed approach is evaluated via modeling and simulation and its superiority compared to other state of the art approaches is illustrated.},
	address = {Baltimore, MD},
	booktitle = {The 51st Conference on Information Sciences and Systems (CISS 2017)},
	pages = {pp. 1-6},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Autonomous Relocation Strategies for Cells on Wheels in Public Safety Networks},
	author = {Rabieekenari, Ladan., Sayrafian, Kamran., Baras, John S.},
	year = {2017},
	month = {01/2017},
	abstract = {Lack of network availability or limited access to~communication services are among the challenges that public~safety officials and first responders could face during disasters~or emergency scenarios. Networking infrastructure can partially~(or sometimes fully) breakdown during a catastrophe. At the~same time, unusual peaks in traffic load could lead to much~higher blocking probability or service interruptions for critical~communication. Lack of adequate communication among emergency~responders or public safety personnel could put many~lives at risks. A possible solution to deal with such scenarios~is through the use of mobile/portable infrastructures commonly~referred to as Cells on Wheels (COW) or Cells on Light~Trucks (COLT). These mobile cells can effectively complement~the existing undamaged infrastructure or enable a temporary~emergency network by themselves. Given the limited capacity of~each cell, variable and spatially non-uniform traffic across the~disaster area can make a big impact on the network performance.~Not only judicious deployment of the cells can help to meet~the coverage and capacity demands across the area, but also~intelligent relocation strategies can optimally match the network~resources to potentially changing traffic demands. Assuming that~each cell can autonomously change its location, in this paper, we~propose a decentralized relocation algorithm that adapts network~coverage in order to increase the supported users traffic. Our~simulations show an average improvement of approximately 35\%~in the supported traffic compared to static uniform deployment.},
	address = {Las Vegas, Nevada},
	booktitle = {The 14th Annual IEEE Consumer Communications \& Networking Conference (CCNC 2017)},
	pages = {pp. 41-44}
}
@conference {
	title = {Network Function Placement on Virtualized Cellular Cores},
	author = {Dietrich, David., Papagianni, Chrysa. , Panagiotis, Papadimitriou., Baras, John S.},
	year = {2017},
	month = {01/2017},
	abstract = {The proliferation of mobiles devices, application sprawl, and the ever-increasing data volume generates significant~stress on cellular networks and particularly on the cellular~core, also known as the Evolved Packet Core (EPC). This is~further exacerbated by the deployment of hardware appliances~for the implementation of a wide range of network functions~(e.g., gateways, mobility management, firewalls, network address~translation), hindering any opportunity for elastic provisioning,~and eventually leading to high operational costs and a significant~degree of load imbalance across the EPC.~Network Function Virtualization (NFV) has been seen a ~promising solution in order to enable elasticity in the cellular core. Applying NFV to the EPC raises the need for network~function (NF) placement, which in turn entails significant challenges,~due to the stringent delay budgets among cellular core components and the coexistence of communicating data and~control plane elements. To address these challenges, we present a~linear programming (LP) formulation for the computation of NF~placements that strikes a balance between optimality and time
complexity. Our evaluation results show that the LP achieves~significantly better load balancing, request acceptance rate,~and resource utilization compared to a greedy algorithm that~performs NF placement inline with carriers{\textquoteright} common practice~today.~},
	address = {Bengaluru, India},
	booktitle = {9th International Conference on COMmunication Systems \& NETworkS (COMSNETS 2017)},
	pages = {pp. 259-266}
}
@conference {
	title = {Optimal Stationary Self-Triggered Sampling for Estimation},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2016},
	month = {12/2016},
	abstract = {In this paper, we study optimal stationary sampling~for transmission of measurements of a stochastic process~from a source encoder to a source decoder through a costly communication~channel. We measure information transferred over~a time interval by the change in the decoder{\textquoteright}s entropy regarding~the state of the process given the transmitted measurements.~In our setting, the encoder employs a sampler to control the~information flow in the channel. The problem is casted as a~discounted infinite horizon optimization problem that takes into~account the transferred information and the paid price. We~derive the optimal stationary sampling policy, and propose two~computational methods with convergence guarantees by using~techniques from approximate dynamic programing. In addition,~we introduce two triggering mechanisms based on the value of~information and on the covariance threshold that can generate~the optimal policy. Finally, we present some numerical and~simulation results.},
	address = {Las Vegas, Nevada},
	booktitle = {55th IEEE Conference on Decision and Control },
	pages = {pp. 3084-3089}
}
@conference {
	title = {Distributed hybrid consensus of second order dynamics over proximity nets*},
	author = {Liu, Zhixin., Wang, L., Baras, John S.},
	year = {2016},
	month = {12/2016},
	abstract = {In this paper, we consider the distributed consensus~problem of the second-order multi-agent system where the~agents are connected via distance-dependent networks. For the~feasibility of information processing, we introduce dwell times~which may be different at different sampling time instants. Each~agent can only receive the information and update its control~laws at discrete sampling time instants, which in combination~with the continuous-time dynamics yields the hybrid closed-loop~dynamics. By analyzing the discrete-time system at the sampling~instants and the continuous-time system between the sampling~instants, we establish the sufficient condition for consensus of~the hybrid second-order multi-agents system, without relying~on the properties of the dynamics of the neighbor graphs.},
	address = {Las Vegas, Nevada},
	booktitle = {55th IEEE Conference on Decision and Control },
	pages = {pp. 4273-4277}
}
@conference {
	title = {Optimal strategies for linear quadratic differential games with costly information},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2016},
	month = {12/2016},
	abstract = {A two players stochastic differential game is considered~with a given cost function. The players engage in a~non-cooperative game where one tries to minimize the cost and~the other tries to maximize the same. The players are given a~dynamical system and their actions serve as the control inputs~to the dynamical system. Their job is to control the state of~this dynamical system to optimize the given objective function.~We use the term {\textquotedblleft}state of the game{\textquotedblright} to describe the state of~this dynamical system. The challenge being that none of the~players has access to the state of the game for all time, rather~they can access the state intermittently and only after paying~some information cost. Thus the cost structure is non-classical~for a linear-quadratic game and it incorporates the value of~information. We provide the Nash equilibrium strategy for the~players under full state information access at no cost, as well~as costly state information access. The optimal instances for~accessing the state information are also provided for the players.},
	address = {Las Vegas, Nevada},
	booktitle = {55th IEEE Conference on Decision and Control },
	pages = {pp. 276-282}
}
@conference {
	title = {Time varying Control set design for UAV Collision Avoidance Using Reachable Tubes},
	author = {Zhou, Yuchen., Raghavan, Aneesh., Baras, John S.},
	year = {2016},
	month = {12/2016},
	abstract = {In this paper, we propose a reachable set based~collision avoidance algorithm for unmanned aerial vehicles (UAVs). UAVs have been deployed for agriculture research and~management, surveillance and sensor coverage for threat detection~and disaster search and rescue operations. It is essential for~the aircraft to have on-board collision avoidance capability to~guarantee safety. Instead of the traditional approach of collision~avoidance between trajectories, we propose a collision avoidance~scheme based on reachable sets and tubes. We then formulate~the problem as a convex optimization problem seeking time~varying control sets for ego aircraft giving predicted intruder~reachable tube. We have applied the approach on a case study~of two quadrotors collision avoidance scenario.},
	address = {Las Vegas, Nevada},
	booktitle = {55th IEEE Conference on Decision and Control },
	pages = {pp. 6857-6862}
}
@conference {
	title = {Systems Engineering and Healthcare},
	author = {Baras, John S.},
	year = {2016},
	month = {11/2016},
	address = {Baltimore, MD},
	organization = {Center for Critical Care and Trauma Education}
}
@conference {
	title = {Co-Active Learning to Adapt Humanoid Movement for Manipulation.},
	author = {Mao, Ren., Baras, John S., Yang, Yezhou., Fermuller, Cornelia.},
	year = {2016},
	month = {11/2016},
	abstract = {In this paper, we address the problem of interactive~robot movement adaptation under various environmental~constraints. A common approach is to adopt motion primitives~to generate target motions from demonstrations. However,~their generalization capability is weak for novel environments.
Additionally, traditional motion generation methods do not~consider versatile constraints from different users, tasks, and~environments. In this work, we propose a co-active learning~framework for learning to adapt the movement of robot end~effectors for manipulation tasks. It is designed to adapt the~original imitation trajectories, which are learned from demonstrations to novel situations with different constraints. The~framework also considers user feedback towards the adapted~trajectories, and it learns to adapt movement through human in-the-loop interactions. Experiments on a humanoid platform~validate the e effectiveness of our approach.},
	address = {The Westin Resort \& Spa},
	booktitle = {2016 IEEE-RAS International Conference on Humanoid Robots (Humanoids 2016)},
	pages = {pp. 372-378},
	organization = {Cancun, Mexico.}
}
@conference {
	title = {On the Mitigation of Interference Imposed by Intruders in Passive RFID Networks},
	author = {Tsiropoulou, Eirini Eleni., Baras, John S., Papavassiliou, Symeon., Qu, G.},
	year = {2016},
	month = {11/2016},
	abstract = {RFID networks are becoming an integral part of the emerging Internet of Things (IoT) era. Within this paradigm passive RFID networks have emerged as low cost energy-efficient alternatives that find applicability in a wide range of applications. However, such RFID networks and devices, due to their limited capabilities, can easily become vulnerable to several intrusive actions. In this paper, the problem of proactively protecting a passive RFID network from security threats imposed by intruders that introduce high interference to the system resulting in the possible disruption of the network{\textquoteright}s proper operation is investigated. Passive RFID tags are associated with a well-designed utility function reflecting on one hand their goal to have their signal properly demodulated by the reader, and on the other hand their risk level of participating in the network, stemming from their hardware characteristics among others, thus characterizing them as normal or intruder tags. An interference mitigation risk aware (IMRA) problem is introduced aiming at maximizing each tag{\textquoteright}s utility function, thus implicitly enforcing tags to conform to a more social behavior. Due to its nature, the proposed problem is formulated as a non-cooperative game among all the tags (normal and intruders) and its Nash equilibrium point is determined via adopting the theory of supermodular games. Convergence of the game to its Nash equilibrium is also shown. A distributed iterative and low-complexity algorithm is proposed in order to obtain the Nash equilibrium point and the operational effectiveness of the proposed approach is evaluated through modeling and simulation.},
	address = {New York, NY},
	booktitle = {Conference on Decision and Game Theory for Security (GameSec 2016)}
}
@conference {
	title = {Reliable Attribute-Based Object Recognition Using High Predictive Value Classifiers},
	author = {Luan, Wentao., Yang, Yezhou., Fermuller, Cornelia., Baras, John S.},
	year = {2016},
	month = {10/2016},
	abstract = {We consider the problem of object recognition in 3D using an ensemble of attribute-based classifiers. We propose two new concepts to improve classification in practical situations, and show their implementation in an approach implemented for recognition from point-cloud data. First, the viewing conditions can have a strong influence on classification performance. We study the impact of the distance between the camera and the object and propose an approach to fusing multiple attribute classifiers, which incorporates distance into the decision making. Second, lack of representative training samples often makes it difficult to learn the optimal threshold value for best positive and negative detection rate. We address this issue, by setting in our attribute classifiers instead of just one threshold value, two threshold values to distinguish a positive, a negative and an uncertainty class, and we prove the theoretical correctness of this approach. Empirical studies demonstrate the effectiveness and feasibility of the proposed concepts.},
	address = {Amsterdam, Netherlands},
	booktitle = {4th European Conference on Computer Vision},
	pages = {pp. 801-815}
}
@conference {
	title = {On the Mitigation of Interference Imposed by Intruders in Passive RFID Networks},
	author = {Tsiropoulou, Eirini Eleni., Baras, John S., Papavassiliou, Symeon., Qu, G.},
	year = {2016},
	month = {09/2016},
	address = {Garching, Munich},
	booktitle = {International Symposium on Networked Cyber-Physical Systems (NetCPS)}
}
@conference {
	title = {Noncommutative Probability Models for Net-CPS and Net-CPSS},
	author = {Baras, John S., Raghavan, Aneesh.},
	year = {2016},
	month = {09/2016},
	address = {Garching, Munich},
	booktitle = {International Symposium on Networked Cyber-Physical Systems (NetCPS)}
}
@conference {
	title = {A Reputation based Trust Management System for the Internet of Things},
	author = {Papagianni, Chrysa. , Baras, John S., Papavassiliou, Symeon.},
	year = {2016},
	month = {09/2016},
	address = {Garching, Munich},
	booktitle = {International Symposium on Networked Cyber-Physical Systems (NetCPS)}
}
@conference {
	title = {Optimal Mission Planning under Logical Constraints with Safety Gaurantees: An Application for Robotic CPSs},
	author = {Maity, Dipankar., Zhou, Yuchen., Baras, John S.},
	year = {2016},
	month = {09/2016},
	address = {Garching, Munich},
	booktitle = {International Symposium on Networked Cyber-Physical Systems (NetCPS)}
}
@conference {
	title = {STAR : Semiring Trust Inference for Trust - Aware Social recommenders},
	author = {Gao, Peixin., Miao, Hui., Baras, John S., Golbeck, Jennifer.},
	year = {2016},
	month = {09/2016},
	abstract = {Social recommendation takes advantage of the influence of social relationships in decision making and the ready availability of social data through social networking systems. Trust relationships in particular can be exploited in such systems for rating prediction and recommendation, which has been shown to have the potential for improving the quality of the recommender and alleviating the issue of data sparsity, cold start, and adversarial attacks. An appropriate trust inference mechanism is necessary in extending the knowledge base of trust opinions and tackling the issue of limited trust information due to connection sparsity of social networks. In this work, we offer a new solution to trust inference in social networks to provide a better knowledge base for trust-aware recommender systems. We propose using a semiring framework as a nonlinear way to combine trust evidences for inferring trust, where trust relationships are represented by 2-D vectors. The trust propagation and aggregation rules, as the building blocks of our trust inference scheme, are based upon the properties of trust relationships. In our approach, both trust and distrust (i.e., positive and negative trust) are considered, and opinion conflict resolution is supported. We evaluate the proposed approach on real-world datasets, and show that our trust inference framework has high accuracy, and is capable of handling trust relationship in large networks. The inferred trust relationships can enlarge the knowledge base for trust information and improve the quality of trust-aware recommendation.},
	address = {Boston, Massachusetts},
	booktitle = {10th ACM Conference on Recommender Systems},
	pages = {pp. 301-308}
}
@conference {
	title = {Optimal Information Control in Cyber-Physical Systems},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2016},
	month = {09/2016},
	abstract = {In this paper, we address optimal information control in cyber-physical systems. In~particular, we study optimal closed-loop policies for transmission of measurements of a stochastic~dynamical system through a communication channel given estimation and communication~costs. We develop a framework for optimizing an aggregate cost function that incorporates~the estimation and the communication costs over a finite time horizon. We obtain the optimal~closed-loop policy, and show that it can be expressed directly in terms of the value of information.~In addition, we propose an approximation algorithm that yields a suboptimal closed-loop policy.~Numerical and simulation results are presented for a simple system.},
	address = {Tokyo, Japan},
	booktitle = {6th IFAC Workshop on Distributed Estimation and Control in Networked Systems},
	pages = {pp. 1-6}
}
@conference {
	title = {The Next Wonder -  MBSE/MBE: From Ideas to "Making Products and Services"},
	author = {Baras, John S.},
	year = {2016},
	month = {09/2016},
	abstract = {Advances in Information Technology have enabled the design of complex engineerd systems, with large number of heterogeneous components and capable of multiple complex functions, leading to the ubiquitious cyber-physical systems (CPS). These advances have at the same time increased the capabilities of such systems and have increased their complexity ~to such an extent that systematic design towards predictable performance is extremely ~challenging, if not infeasible with the current methodologies and tools. We first describe a rigorous framework we are developing for model-based systems engineering (MBSE), s system level deisgn methodology that addresses these challenges, which also incorporates manufacturing, operation and life cylce considerations. We describe the three fundemental components for MBSE within our framework: (a) An integrated systems modeling hub built around SysML, employing meta-modeling and tools; (b) Linking this modelling hub with tradeoff analysis tools for design space exploration, employing linkage with the parametric and requirements ~diagram of SysML, and integrated methods and tools from multi-criteria ~mixed ( integer and numerical variables and metrics) optimization and constrained based reasoning; (c) Representation and management of requirements, employing initial efforts towards an integration of methods ~and tools from model checking, contract based ~design and automatic theorem proving, and including finite time temporal logic ~specifications for system behaviour. We describe ~our results for conquering and managing the complexity of queries in design, manufacturing and operational space exploration. We provide a short description ~of such complex systems, a subject of rapindly increasing importance in view paradigms. We next describe applications of the framework to~several important ~current ~technological problems ( several major domains of CPS): power grids, automotive, aerospcae, energy efficient buildings, sensor and communication networks, smart manufacturing, robotics and UAV, health care, cyber-security. We close with a description of what is still lacking , research challenges and future promising research directions.},
	address = {Berlin, Germany},
	booktitle = {21st IEEE International Conference on Emerging Technologies and Factory Automation}
}
@conference {
	title = {Joint Optimization for Social Content Dissemination in Wireless Networks},
	author = {Weng, Xiangnan., Baras, John S.},
	year = {2016},
	month = {09/2016},
	abstract = {Over the last decade, success of social networks~has significantly reshaped how information disseminate among ~users in terms of scale, intensity and speed. Much effort, both~academic and industrial, has been dedicated to learning the~patterns of content dissemination to further facilitate it. ~However,~as users become dominantly mobile in this process, little is done~to consider the impact of the wireless environment, in particular,~how to optimize the system, in the presence of capacity shortage,~to better disseminate the contents. In this paper, we propose ~a novel method, utilizing: 1) hybrid systems to handle active~disseminating requests; and 2) predictions of dissemination dynamics~from the social network applications. This method could~mitigate the performance degradation for content dissemination~due to wireless delivery delay. Results indicate that predictions of
dissemination at social layer, even coarse ones, benefit the social dissemination, by improving scheduling at wireless layer, which~in turn improves the accuracy of the predictions with feedback.},
	address = {Valencia, Spain},
	booktitle = {2016 IEEE 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)},
	pages = {pp. 1-7}
}
@conference {
	title = {Multi-Agent Collaborative Decision Making: Constrained Event Algebras, New Logics and Their Game Theoretic Semantics},
	author = {Baras, John S.},
	year = {2016},
	month = {07/2016},
	address = {Ann Arbor, MI},
	booktitle = {Workshop on Information, Decisions and Networks, in honor of D. Teneketzis{\textquoteright} 65th Birthday}
}
@conference {
	title = {Networked Cyber-Physical Systems (Net-CPS)},
	author = {Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {We describe recent results on foundational aspects of modeling, architecture and performance of networked~cyber-physical systems. These include: multi-layer multigraph models, constrained coalitional games, analysis of trust and~mistrust in collaboration, dynamics of signed graphs, distributed consensus with adversaries, new concepts of value of~information and event-driven inference and decision making, non-commutative probability models. We conclude with directions~for future research.},
	address = {Chengdu ,China},
	booktitle = {35th Chinese Control Conference}
}
@conference {
	title = {Attitude synchronisation of multiple rigid in SE(3) over proximity networks},
	author = {Deng, Juan., Wang, L., Liu, Z., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {This paper investigates the attitude synchronization of a group of moving rigid bodies whose states including positions and rotation matrices evolve in the Lie group SE(3). The commonly used circular neighborhood is adopted, and the neighbor graphs are described by proximity networks. In order to avoid introducing discussions on the abrupt changes of neighbor graphs, a dwell time is introduced. The distributed sampled-data control law for the angular velocity is designed. Under the assumptions on the initial states, we provide sufficient conditions for the attitude synchronization of multiple rigid body system. Compared with the existing results, our condition depends only on the neighborhood radius, the moving velocity and the dwell time.},
	address = {Chengdu ,China},
	booktitle = {35th Chinese Control Conference},
	pages = {pp 8275-8280}
}
@conference {
	title = {Synchronization and Collision Avoidance in Non-Linear Flocking Networks of Autonomous Agents},
	author = {Somarakis, Christoforos., Paraskevas, Evripidis., Baras, John S., Motee, Nader.},
	year = {2016},
	month = {07/2016},
	abstract = {We introduce and discuss two novel second-order consensus networks with state-dependent couplings of CuckerSmale type. The first scheme models flocking to synchronization over a network of agents where the alignment of the agent{\textquoteright}s states occurs over a non-trivial limit orbit that is generated by the internal dynamics of each individual agent. The second scheme models the speed alignment of a group of agents which avoid approaching each other closer than a prescribed distance. While seemingly different, both of these systems can be analyzed using the same mathematical methods. We rigorously analyze both examples and reveal their striking similarities. We arrive at sufficient conditions that relate the initial configurations and the systems{\textquoteright} parameters that give rise to a collective common behavior. Simulation examples are presented to support our theoretical conclusions},
	address = {Athens, Greece},
	booktitle = {24th Mediterranean Conference on Control and Automation},
	pages = {pp. 1089-1094}
}
@conference {
	title = {Combining Greedy Hyperbolic Routing with Back - pressure Scheduling for Better Network Performance},
	author = {Rabieekenari, Ladan., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {The back-pressure algorithm (BP) has received~much attention for jointly routing and scheduling over multihop~networks. The back-pressure algorithm is throughput optimal,~but it has poor delay performance. This is due to~selection of unnecessarily long paths and routing loops, as the~algorithm operates without accounting for the network topology.~In this paper, we propose a throughput-optimal routing~and scheduling algorithm that improves delay performance~by greedy embedding of the network in hyperbolic space. We~improve delay performance by solving an optimization problem,
which aims to send packets mostly to greedy neighbors, subject~to throughput-optimality constraints. The algorithm that solves~this optimization problem has a design parameter M. We study~the effect of M on delay performance analytically. We validate~our theoretical results via simulations and demonstrate that the~proposed algorithm improves the delay performance.},
	address = {Minneapolis, Minnesota},
	booktitle = {22nd International Symposium on Mathematical Theory of Networks and Systems},
	pages = {pp.698-705}
}
@conference {
	title = {Consensus and Synchronized Periodicity in Nonlinear Delayed Networks},
	author = {Somarakis, Christoforos., Baras, John S., Motee, Nader.},
	year = {2016},
	month = {07/2016},
	abstract = {In this paper, we investigate stability and convergence properties of a class of nonlinear delayed consensus networks. Using tools and techniques from functional differential equations, sufficient stability conditions with respect to a common state as well as estimates on the convergence rate are derived. We characterize the limit (consensus) state for time-invariant sub-classes of these networks. More importantly, we specify under what conditions a delayed network exhibits periodic synchronized solutions. We provide sufficient conditions for existence, uniqueness and stability of this interesting phenomenon that we illustrate with a simulation example.},
	address = {Minneapolis, Minnesota},
	booktitle = {22nd International Symposium on Mathematical Theory of Networks and Systems},
	pages = {pp. 823-829}
}
@conference {
	title = {Dynamic, Optimal Sensor Scheduling and Value of Information},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {In this paper, we present a method for the optimal state estimation of a linear system, observed by various dynamically schedulable and distributed sensors. We consider this problem to be a problem of information fusion, where the information is obtained from the sensors in exchange of scheduling and sensor operational costs. Sensors over a distributed network can work together efficiently in order to maximize the overall network performance. We consider several costs related to sensor scheduling such as the continuous cost for keeping the sensor on, and sensor switching cost for turning a sensor on from off state and vice versa. Our goal is to estimate the state as closely as possible while minimizing the scheduling cost. We incorporate the error in estimation as a cost in the optimization function. The resultant problem is then converted into an optimal control problem, where optimal scheduling is obtained by pointwise maximizing the Hamiltonian of the system.},
	address = {Washington DC},
	booktitle = {International Conference on Information Fusion (FUSION 2015)},
	pages = {pp. 239-244}
}
@conference {
	title = {The Effect of Delays in the Economic Dispatch Problem for Smart Grid Architectures},
	author = {Somarakis, Christoforos., Maity, Dipankar., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {We consider the Economic Dispatch Problem~(EDP) in power systems for a smart-grid friendly environment.~We develop a consensus based decentralized optimization algorithm~that evolves in a time-varying communication network~that suffers from multiple propagation time-dependent delays.
This paper, being an improvisation of an earlier work of~ours, addresses the effects of time dependent delays in a fully~decentralized network. We show analytically and by simulation~that propagation delays may not only affect the performance~of the dynamic algorithm that solves the EDP but can ~also~destabilize the system.},
	address = {Boston, Massachusetts},
	booktitle = {2016 American Control Conference},
	pages = {pp. 3533-3538}
}
@conference {
	title = {Distributed Energy-Aware Mobile Sensor Coverage Game with Inter-Agent Communication},
	author = {Paraskevas, Evripidis., Maity, Dipankar., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {Mobile Sensor Networks (MSN) are used to monitor large areas and collect measurements, e.g. temperature, humidity, or pressure data. Mobile sensors try to optimize their benefit from sensing a particular area, while keeping their energy consumption at the lowest possible level. We formulate this energy-aware sensor coverage problem as a potential game, where the mobile sensor nodes are considered as agents. The utility function of the game captures the trade-off between the benefit from coverage and the energy consumption. We also propose a distributed learning strategy for this potential game. The algorithm enables a bit-valued information exchange between the agents. Finally, it is proved that the learning rule converges to a Nash Equilibrium.},
	address = {Boston, Massachusetts},
	booktitle = {2016 American Control Conference},
	pages = {pp. 6259-6264}
}
@conference {
	title = {Active sampling exploiting detector response pattern for efficient target detection},
	author = {Luan, Wentao., Mao, Ren., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {Detecting targets in an image is a fundamental task in computer vision and robotic system. When only a trained detector (binary classifier) is at hand, the target detection problem becomes localizing the correct windows containing targets in the image and can be considered as a sampling problem. Exhaustive sliding window method is a common approach, but it is usually computationally expensive especially when the detection algorithm is time-consuming. In this work, we observe that detector{\textquoteright}s response scores of sampling windows fade gradually from the peak response window in the detection area and we approximate this scoring pattern with an exponential decay function. By exploiting this property, we propose an active sampling method for efficient target detection to avoid exhaustively searching all the window space. The method estimates the probability of windows containing the target by fusing information from sampled windows and their detector{\textquoteright}s scores and then decides the next window to be observed. Experiments have shown that our proposed method improves efficiency in human detection applications as it requires fewer windows to achieve similar performance compared to sliding windows and multi-stage particle window (MS-PW) method.},
	address = {Heidelberg , Germany},
	booktitle = {19th Intenation Conference on Information Fusion},
	pages = {pp. 1916-1922}
}
@conference {
	title = {Maximization of Information in Energy Limited Directed Communication},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2016},
	month = {06/2016},
	abstract = {This study is concerned with an observer who~desires to inform optimally a distant agent regarding a physical~stochastic process in the environment. We consider that the~observer has a constraint on the energy resource for the directed~communication to the agent. The information we are interested~in is the change in the knowledge possessed by the agent about~the state of the process. We find the maximum information~that can be transferred from the observer to the agent over~a finite horizon subject to a bound on the total energy of the~observer.We show that the maximum information is the optimal~value of a mixed-integer nonlinear optimization problem. We~obtain lower and upper bounds on the maximum information~and also a suboptimal admissible solution based on a semidefinite~programming. Moreover, we propose an optimized~event-triggering mechanism based on a linear matrix inequality~which yields event-driven sampling. Numerical and simulation~results are presented for simple stable and unstable systems.},
	address = {Aalborg, DK},
	booktitle = {European Control Conference (ECC16)},
	pages = {pp. 1001-1006}
}
@conference {
	title = {Timed Automata Approach for Motion Planning Using Metric Interval Temporal Logic},
	author = {Zhou, Yuchen., Maity, Dipankar., Baras, John S.},
	year = {2016},
	month = {06/2016},
	abstract = {In this paper, we consider the robot motion (or~task) planning problem under some given bounded time high-level specifications. We use metric interval temporal logic~(MITL), a member of the temporal logic family, to represent~the task specification and then we provide a constructive way to~generate a timed automaton and methods to look for accepting~runs on the automaton to find a feasible motion (or path)~sequence for the robot to complete the task.~},
	address = {Aalborg, DK},
	booktitle = {European Control Conference (ECC16)},
	pages = {pp. 690-695}
}
@conference {
	title = {Dynamics of Collectives with Opinionated Agents: The Case of Scrambling Connectivity},
	author = {Somarakis, Christoforos., Hadadi, R., Baras, John S.},
	year = {2016},
	month = {06/2016},
	abstract = {We investigate the problem of social/opinion networks of autonomous agents, each of which has a personal view that follows an independent dynamic behavior and it communicates with their neighbors under a cooperative algorithm. We apply mathematics from non-negative matrix theory. We investigate agents with identical and non-identical views and we establish sufficient conditions for stability and convergence to a common synchronized opinion.},
	address = {Aalborg, DK},
	booktitle = {European Control Conference (ECC16)},
	pages = {pp. 1445-1450}
}
@conference {
	title = {Trust-Aware Network Utility Optimization in Multihop Wireless Networks with Delay Constraints},
	author = {Paraskevas, Evripidis., Jiang, Tao., Purkayastha, Punyaslok., Baras, John S.},
	year = {2016},
	month = {06/2016},
	abstract = {Many resource allocation problems can be formulated as a constrained maximization of a utility function. Network Utility Maximization (NUM) applies optimization techniques to achieve decomposition by duality or the primal dual method. Several important problems, for example, joint source rate control, routing, and scheduling design, can be optimized by using this framework. In this work, we introduce an important network security concept, {\textquotedblleft}trust{\textquotedblright}, into the NUM formulation and we integrate nodes{\textquoteright} trust values in the optimization framework. These trust values are based on the interaction history between network entities and community-based monitoring. Our objective is to avoid routing packets through paths with large percentage of malicious nodes. We also add end-to-end delay constraints for each of the traffic flows. The delay constraints are introduced to capture the imposed quality of service (QoS) requirements for each traffic flow.},
	address = {Athens, Greece},
	booktitle = {24th Mediterranean Conference on Control and Automation},
	pages = {pp. 593-598}
}
@conference {
	title = {Strategies for Two-Player Differential Games with Costly Information},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2016},
	month = {05/2016},
	abstract = {In this work, a two players nonzero-sum differential game is considered, where one player tries to minimize some predefined cost and the other tries to maximize the same. The game is described by a stochastic differential system and the actions of the players serve as the control inputs to the dynamical system. The cost being a function of the actions chosen by the players and the state of the dynamical system, the players aim to control the state in order to optimize the cost functional. However in this problem, the players do not have the access to the states for every time, rather the states are available at discrete time instances after some finite costs are paid by the players. The inclusion of the information-cost makes the structure of the cost functional non-classical. The work presents the strategies for the players under no-cost information access as well as under costly information access. Explicit time instances for the information access are also derived by solving certain finite dimensional optimization problems.},
	address = {Xi{\textquoteright}an, China},
	booktitle = {13th International Workshop on Discrete Event Systems },
	pages = {pp . 211-216}
}
@conference {
	title = {Optimal Self-Driven Sampling for Estimation Based on Value of Information},
	author = {Soleymani, Touraj., Hirche, Sandra., Baras, John S.},
	year = {2016},
	month = {05/2016},
	abstract = {Consider an observer (reporter) who desires to inform optimally a distant agent regarding a physical stochastic process in the environment while the directed communication of the observer to the agent has a price. We define a metric, from a task-oriented perspective, for the information transferred from the observer to the agent. We develop a framework for optimizing an augmented cost function which is a convex combination of the transferred information and the paid price over a finite horizon. We suppose that the decision making takes place inside a source encoder, and that the sampling schedule is the decision variable. Moreover, we assume that no measurement at the current time is available to the observer for the decision making. We derive the optimal self-driven sampling policy using dynamic programming, and we show that this policy corresponds to a self-driven sampling policy based on a quantity that is, in fact, the value of information at each time instant. In addition, we use a semi-definite programming relaxation to provide a suboptimal sampling policy. Numerical and simulation results are presented for a simple unstable system},
	address = {Xi{\textquoteright}an, China},
	booktitle = {13th International Workshop on Discrete Event Systems },
	pages = {pp.183-188}
}
@conference {
	title = {Joint Optimization for Social Content Delivery in Wireless Networks},
	author = {Weng, Xiangnan., Baras, John S.},
	year = {2016},
	month = {05/2016},
	abstract = {Over the past decade, success of social networks has significantly reshaped how people consume information. Recommendation of contents based on user profiles is wellreceived. However, as users become dominantly mobile in content consumption, little is done to consider the optimization regarding the wireless environment. In this paper, we investigate a centralized wireless content delivery system with heterogeneous base stations, aiming to optimize overall user rewards given the capacity constraints of the wireless networks. We propose a scalable two-phase scheduling framework, consisting of: 1) distributed delivery decisions by each base station, and 2) resource consolidation by the system. Results indicate this novel joint optimization approach is both efficient and scalable},
	address = {Kuala lumpur, Malaysia},
	booktitle = {IEEE International Conference on Communications (ICC 2016)}
}
@conference {
	title = {Joint Optimization for Social Content Delivery in Heterogeneous Wireless Networks},
	author = {Weng, Xiangnan., Baras, John S.},
	year = {2016},
	month = {05/2016},
	abstract = {Over the past decade, success of social networks has significantly reshaped how people consume information. Recommendation of contents based on user profiles is well received. However, as users become dominantly mobile in content consumption, little is done to consider the optimization regarding the wireless environment. In this paper, we investigate a centralized wireless content delivery system with heterogeneous base stations, aiming to optimize overall user rewards given the capacity constraints of the wireless networks. We propose a scalable two-phase scheduling framework, consisting of: 1) distributed delivery decisions by each base station, and 2) resource consolidation by the system. Results indicate this novel joint optimization approach is both efficient and scalable.},
	address = {Tempe, Arizona},
	booktitle = {14th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks},
	pages = {pp. 155 - 162}
}
@conference {
	title = {Learning Through Direct and Indirect Communications for Distributed Control in Networked Systems},
	author = {Baras, John S.},
	year = {2016},
	month = {02/2016},
	address = {Zurich, Switzerland},
	organization = {Department of Automatic Control, ETH}
}
@conference {
	title = {Distributed Solution of the Economic Dispatch Problem in Smart Grid Power Systems Framework with Delay},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {12/2015},
	abstract = {We consider the Economic Dispatch Problem in~power systems in a smart-grid architecture friendly environment.~The problem is tackled with the use of multiple decentralized~controllers that execute parallel distributed consensus~algorithms. The scenario takes into account the presence of~multiple time-varying communication delays.},
	address = {Osaka, Japan},
	booktitle = {54th Conference on Control (CDC 2015)},
	pages = {pp. 6577-6582}
}
@conference {
	title = {Distributed Nonlinear Programming Methods for Optimization Problems with Inequality Constraints},
	author = {Matei, Ion., Baras, John S.},
	year = {2015},
	month = {12/2015},
	abstract = {In this paper, we consider a distributed optimization problem, where a set of agents interacting and cooperating locally have as common goal the minimization of a function expressed as a sum of (possibly non-convex) differentiable functions. Each function in the sum is associated with an agent and each agent has assigned an inequality constraint, therefore generating an optimization problem with inequality constraints. In this paper, we present a distributed algorithm for solving such a problem~and give local convergence results. Our approach is based on solving (in a centralized manner) an equivalent augmented optimization problem with mixed constraints. The structure of this augmented problem ensures that the resulting algorithm is distributed. The main challenge in proving the convergence results comes from the fact that the local minimizers are no longer regular due to the distributed formulation. We present also an extension of this algorithm that solves a constrained optimization problem, where each agent has both equality and inequality constraints.},
	address = {Osaka, Japan},
	booktitle = {54th Conference on Control (CDC 2015)},
	pages = {pp. 2649-2654}
}
@conference {
	title = {Trust-Aware Crowdsourcing with Domain Knowledge},
	author = {Liu, Xiangyang., Baras, John S.},
	year = {2015},
	month = {12/2015},
	abstract = {The rise of social network and crowdsourcing platforms~makes it convenient to take advantage of the collective~intelligence to estimate true labels of questions of interest.~However, input from workers is often noisy and even malicious.~Trust is used to model workers in order to better~estimate true labels of questions. We observe that questions~are often not independent in real life applications. Instead,~there are logical relations between them. Similarly, workers~that provide answers are not independent of each other~either. Answers given by workers with similar attributes~tend to be correlated. Therefore, we propose a novel unified~graphical model consisting of two layers. The top layer~encodes domain knowledge which allows users to express~logical relations using first-order logic rules and the bottom~layer encodes a traditional crowdsourcing graphical model.~Our model can be seen as a generalized probabilistic soft~logic framework that encodes both logical relations and~probabilistic dependencies. To solve the collective inference~problem efficiently, we have devised a scalable joint inference~algorithm based on the alternating direction method~of multipliers. Finally, we demonstrate that our model is~superior to state-of-the-art by testing it on multiple real-world~datasets.},
	address = {Osaka, Japan},
	booktitle = {54th Conference on Control (CDC 2015)},
	pages = {pp. 2913-2918}
}
@conference {
	title = {Event Based Control for Control Affine Nonlinear Systems: A Lyapunov Function Based Approach},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2015},
	month = {12/2015},
	abstract = {In this paper, we propose an event based control~strategy for control affine nonlinear systems. The proposed~method ensures sufficient reduction in communication by only~invoking a communication when some event has occurred. The~error between the continuous state feedback nonlinear system~and the event based system can be bounded in an invariant~set. The upper bound of this error is derived which can be~controlled by appropriately choosing the parameters for the~event triggering function. This method is then applied to a~networked nonlinear system of inverted pendulum and a nonlinearizable~nonlinear system.},
	address = {Osaka, Japan},
	booktitle = {54th Conference on Control (CDC 2015)},
	pages = {pp. 3767-3772}
}
@conference {
	title = {Reachable Set Approach to Collision Avoidance for UAVs},
	author = {Zhou, Yuchen., Baras, John S.},
	year = {2015},
	month = {12/2015},
	abstract = {In this paper, we propose a reachable set based~collision avoidance algorithm for unmanned aerial vehicles~(UAVs). UAVs have been deployed for agriculture research and~management, surveillance and sensor coverage for threat detection~and disaster search and rescue operations. It is essential for~the aircraft to have on-board collision avoidance capability to~guarantee safety. Instead of the traditional approach of collision~avoidance between trajectories, we propose a collision avoidance~scheme based on reachable sets and tubes. We then formulate~the problem as a convex optimization problem seeking suitable~control constraint sets for participating aircraft. We have~applied the approach on a case study of two quadrotors collision~avoidance scenario.},
	address = {Osaka, Japan},
	booktitle = {54th Conference on Control (CDC 2015)},
	pages = {pp. 5947-5952}
}
@conference {
	title = {Bipartite Consensus for Global Trust in Social Network Services},
	author = {Gao, Peixin., Liu, Zhixin., Baras, John S.},
	year = {2015},
	month = {12/2015},
	abstract = {As social network services (SNS) are gaining popularity, establishing trust relationships among users in SNS is necessary for user interaction and decision making. However, the evaluation of global trust values (i.e. reputation) of users suffers from the curse of opinion divergence in the network. In this paper, we consider the scenario of opinion divergence within social networks, and propose a method to reach different global trust values between groups of users with controversial opinions in the network. We model the global trust opinion formation in discrete-time dynamics and introduce bipartite consensus as the approach to establish global trust in such circumstances. Such approach works upon the property of structural balance, and can be extended to more general situations where eventual positivity applies. Via our approach, non-trivial global trust can be reached within the network, which can guide users{\textquoteright} social behaviors, and support many SNS-based applications.},
	address = {San Diego, California},
	booktitle = {IEEE Global Communications Conference (Globecom 2015)}
}
@conference {
	title = {QoS Aware Component-Based Routing in Resource-Constrained Wireless Multi-Hop Networks},
	author = {Paraskevas, Evripidis., Baras, John S.},
	year = {2015},
	month = {11/2015},
	abstract = {With an increasing number of wireless devices available, there is a tremendous need for designing new efficient protocols, which take into account resource constraints and at the same time provide adequate Quality of Service (QoS) performance guarantees (e.g. throughput, latency etc.). Most wireless protocols currently used perform well under specific environmental conditions or in particular applications. In this work, we propose a novel methodology for designing routing protocols for resource-constrained wireless multi-hop networks by separating the protocol into distinct components, which specify particular functionalities. Different QoS requirements can be guaranteed by configuring the different components without the need to modify or develop the protocol from scratch. An initial study for energy-constrained environments indicated that our approach is effective. In our ongoing work we consider adversarial environments and we develop techniques to mitigate network-layer attacks. Finally, we are investigating the design of a decision-theoretic module for dynamic protocol configuration. Keywords- QoS performance, Routing, multi-hop networks},
	address = {San Fransisco, CA},
	booktitle = {23rd IEEE International Conference on Network Protocols (ICNP - PhD Forum )},
	pages = {pp. 476-478}
}
@conference {
	title = {A Rigorous Framework for MBSE and Applications to IoT, WSN and MEMS},
	author = {Baras, John S.},
	year = {2015},
	month = {11/2015},
	address = {Chantilly, Virginia},
	booktitle = {IBM Continuing Education for the Internet of Things Conference}
}
@conference {
	title = {Security and Trust for Networked Cyber Physical Systems (Net-CPS)},
	author = {Baras, John S.},
	year = {2015},
	month = {10/2015},
	address = {Stockholm, Sweden},
	booktitle = {2015 Cyber-Security and Privacy Winter School (2015 CySeP)}
}
@conference {
	title = {Reasoning and Decision Making in Health Care Management of Diabetes Mellitus using as Framework Model Based Systems Engineering},
	author = {Katsipis, Iakovos M., Baras, John S.},
	year = {2015},
	month = {10/2015},
	address = {Washington DC},
	booktitle = {White 2015, The 6th Annual Workshop on Health IT and Economics}
}
@conference {
	title = {Dynamic Co-evolving Sociotechnical Networks},
	author = {Baras, John S.},
	year = {2015},
	month = {10/2015},
	address = {Saudi Arabia},
	booktitle = {KAUST Conference on Human-Machine Networks and Intelligent Infrastructure},
	organization = {King Abdullah University (KAUST)}
}
@conference {
	title = {Security and Trust for Networked Control and Sensor Systems},
	author = {Baras, John S.},
	year = {2015},
	month = {09/2015},
	abstract = {The tremendous explosion of wireless devices and services have created unprecedented advances and are impacting every aspect of life and work. However, many of these advances and resulting expanding markets are critically endangered by weaknesses in security, integrity and trust. We first describe several of these emerging systems and markets including aerospace, automotive, industrial control, factories, power grids and SCADA,~ healthcare, e-commerce, e-payments, social networks over the Web. We then describe various physical layer (e.g. hardware and signal processing) techniques that can be successfully utilized to significantly strengthen the security of wireless devices and networked systems.~ We argue for the need of a {\textquotedblleft}trusted core{\textquotedblright} in wireless networks and for the allocation of part of the security functionality to the physical layer. We next turn into the subject of trust in networked systems and describe a new framework using multiple partially ordered semirings for analyzing reputation and trust dynamics and composite trust. Next we describe our work based on constrained coalitional games towards understanding the role of trust in collaboration and social networks. We describe several specific applications of these methods in securing distributed inference systems, SCADA sensor networks for power grids, wireless network routing protocols, LTE paging systems, wireless handheld devices for healthcare and e-payment systems. We close by describing the need for rigorous frameworks and theories for composable security and outline future research challenges and directions.},
	address = {Ingolstadt, Germany},
	booktitle = {3rd International Symposium for ICS \& SCADA Cyber Security Research 2015}
}
@conference {
	title = {HyperCubeMap: Optimal Social Network Ad Allocation Using Hyperbolic Embedding },
	author = {Miao, Hui., Gao, Peixin., Hajiaghayi, MohammadTaghi., Baras, John S.},
	year = {2015},
	month = {08/2015},
	abstract = {Advertising activity on SNS has grown rapidly and is now a billion dollar business. In the SNS advertising model, the SNS serves as the advertising agent, and takes the advantage of network diffusion to attract advertisers and charges for the cascading impressions. The optimal ad allocation task is to choose the ad allocation plan that maximizes the revenue. Each user has different diffusion ability, limited daily impressions and the advertisers have various bidding prices and budget concerns. A feasible plan that obeys the constraints is difficult to find. The solution of this problem lies in the space of N |Ads|{\texttimes}|User| 0 , which makes direct optimization unattractive. In this paper, we study SNS advertising business models, formulate the SNS ad allocation problem and show their connections with hyperbolic embedding. We develop a new embedding algorithm HYPERCUBEMAP that allows for dimension reduction. Our proposed method reduces the dimensionality of the original problem significantly, runs two to four orders of magnitude faster, and reaches 95\% of the optimum},
	address = {Paris, France},
	booktitle = {The 2015 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining (ASONAM 2015)},
	pages = {pp. 357-362}
}
@conference {
	title = {A Modeling, Health IT, Analytics Framework for Healthcare Management and Application to Diabetes II},
	author = {Katsipis, Iakovos M., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {We develop a framework using modern Model-Based System Engineering methodologies and apply it to Diabetes 2. We include a Controlled Hidden Markov Chain model for diabetes, three diagnostic tests, ten interventions, three types of patients. We develop three methods for computing tradeoffs between cost and health care quality. One is an exhaustive Monte Carlo simulation and the other two use multi-criteria optimization with full and partial state information. The latter obtain similar results at a fraction of the time of the first. We demonstrate the powerful capabilities of such a framework.},
	address = {Nashville, TN},
	booktitle = {INFORMS Healthcare Conference}
}
@conference {
	title = {Non-Linear Flocking Networks with Collision Avoidance},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {We consider a second order non-linear consensus (flocking) network of a finite population of autonomous agents and~prove that the long-term behavior of its solution is towards a common value while the flock remains connected. We elevate the~analysis to a collision avoidance type flocking after taking into consideration repelling forces between agents.},
	address = {Hangzhou, China},
	booktitle = {34th Chinese Control Conference (CCC2015)},
	pages = {pp. 7633-7638}
}
@conference {
	title = {Pose Synchronization of Rigid body Networks with Switching Topologies},
	author = {Deng, Juan., Song, Wenjun., Liu, Zhixin., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {Coordination control of multiple rigid bodies attracts much attention of researchers due to its wide applications. This~paper presents the pose synchronization problem of the moving rigid bodies whose dynamics is described by the group SE(3).~The case of undirected neighbor graphs with switching interconnection topologies is considered. We design a distributed control~law based on relative rotation matrices and relative positions between the neighboring rigid bodies, and show that the SE(3)~reaches pose synchronization if and only if the neighbor graphs are infinitely jointly connected, which relaxes the theoretical~results in the existing literature.},
	address = {Hangzhou, China},
	booktitle = {34th Chinese Control Conference (CCC2015)},
	pages = {pp. 7639-7644}
}
@conference {
	title = {A Simple Proof of the Continuous Time Linear Consensus Problem with Applications in Non-Linear Flocking Networks},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {We revisit the linear distributed consensus problem~in continuous time, to provide a simple and elegant proof~under very mild assumptions. Our approach is based on a novel~extension of the contraction coefficient that can be adapted to~the continuous time version of the model. We apply our results~in non-linear second order consensus networks of Cucker-Smale type and we obtain new initial conditions for asymptotic~flocking.},
	address = {Linz, Austria},
	booktitle = {European Control Conference (ECC15)},
	pages = {pp. 1546-1553}
}
@conference {
	title = {Optimal Mission Planner with Timed Temporal Logic Constraints},
	author = {Zhou, Yuchen., Maity, Dipankar., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {In this paper, we present an optimization-based~method for path planning of a mobile robot subject to time~bounded temporal constraints, in a dynamic environment.~Temporal logic (TL) can address very complex task specification~such as safety, coverage, motion sequencing etc. We use metric temporal logic (MTL) to encode the task specifications with timing constraints.We then translate the MTL formulae into mixed~integer linear constraints and solve the associated optimization~problem using a mixed integer linear program solver. This~approach is different from the automata-based methods which generate a finite abstraction of the environment and dynamics,~and use an automata-theoretic approach to formally generate~a path that satisfies the TL specifications. We have applied~our approach on several case studies in complex dynamical~environments subjected to timed temporal specifications.},
	address = {Linz, Austria},
	booktitle = {European Control Conference (ECC15)},
	pages = {pp. 759-764}
}
@conference {
	title = {Security and Trust in a Networked Immersed World: From Components to Systems and Beyond},
	author = {Baras, John S.},
	year = {2015},
	month = {07/2015},
	address = {Oxford, UK},
	organization = {Department of Engineering Science, University of Oxford}
}
@conference {
	title = {Trust in Networks and Networked Systems},
	author = {Baras, John S.},
	year = {2015},
	month = {07/2015},
	address = {Cambridge, UK},
	organization = {Computer Science Department, University of Cambridge}
}
@conference {
	title = {New Results on Stochastic Consensus Networks},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {We revisit the general linear consensus problem and provide new conditions for asymptotic consensus on two types of stochastic versions of the algorithm, in discrete and continuous time. We show that our method unifies a number of proposed models in the literature as well as it extends and generalizes existing results.},
	address = {Maison de la Mutualite, Paris, France},
	booktitle = {2015 SIAM Conference on Control and Its Applications},
	pages = {pp. 115-122}
}
@conference {
	title = {Crowdsourcing with Multi-Dimensional Trust},
	author = {Liu, Xiangyang., He, He., Baras, John S.},
	year = {2015},
	month = {07/2015},
	abstract = {We consider a typical crowdsourcing task that aggregates input from multiple workers as a problem in information fusion. To cope with the issue of noisy and sometimes malicious input from workers, trust is used to model workers{\textquoteright} expertise. In a multi-domain knowledge learning task, however, using scalar-valued trust to model a worker{\textquoteright}s performance is not sufficient to reflect the worker{\textquoteright}s trustworthiness in each of the domains. To address this issue, we propose a probabilistic model to jointly infer multi-dimensional trust of workers, multi-domain properties of questions, and true labels of questions. Our model is very flexible and extensible to incorporate metadata associated with questions. To show that, we further propose two extended models, one of which handles input tasks with real-valued features and the other handles tasks with text features by incorporating topic models. Finally, we evaluate our model on real-world datasets and demonstrate that our model is superior to state-of-the-art and the two extended models have even better performance. In addition, our models can effectively recover trust vectors of workers, which can be very useful in task assignment adaptive to workers{\textquoteright} trust in the future. These results can be applied for fusion of information from multiple data sources like sensors, human input, machine learning results, or a hybrid of them.},
	address = {Washington DC},
	booktitle = {International Conference on Information Fusion (FUSION 2015)},
	pages = {pp. 574-581}
}
@conference {
	title = {Semiring-Based Trust Evaluation for Information Fusion in Social Network Services},
	author = {Gao, Peixin., Baras, John S., Golbeck, Jennifer.},
	year = {2015},
	month = {07/2015},
	abstract = {As online social network services (SNS) are booming~and gaining tremendous popularity, there is a sharply increasing~amount of information exchange and interactions among SNS~users. Taking this advantage, users in SNS make decisions via~collecting and combining information from different sources~(i.e. other users). However, there exists a large variance of~trustworthiness among SNS populations, which is threatening the~quality of the information fusion process. In such circumstances,~trust relationships among users in SNS are very important in~decision making as well as for the success of many SNS-based applications, e.g. recommender systems and ad targeting. An~appropriate trust inference mechanism for trust evaluation is~necessary in extending the knowledge base of trust opinions and~tackle the issue of limited trust information due to link sparsity~in social networks. In this work, we model the trust relationship~among users in SNS as a 2-dimensional vector, and propose a semiring-based model for trust propagation and fusion as the~building block of our trust inference framework. Specifically, in~our approach, both trust and distrust (i.e., positive and negative~trust) are both considered, and opinion conflict resolution is supported by our framework of trust inference.},
	address = {Washington DC},
	booktitle = {International Conference on Information Fusion (FUSION 2015)},
	pages = {pp. 590-596}
}
@conference {
	title = {Simple Distributed Control of Networked Systems: Learning, Direct and Indirect Communications},
	author = {Baras, John S.},
	year = {2015},
	month = {07/2015},
	address = {Paris, France},
	booktitle = {SIAM Conference on Control and its Applications}
}
@conference {
	title = {Delay-independent convergence for Linear Consensus Networks with Applications to Non-linear Flocking Systems},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {06/2015},
	abstract = {This work studies a class of linear first order and non-linear second order static distributed consensus networks with time-varying multiple propagation delays, in continuous~time. We provide conditions for convergence of to a common constant value, under an increased~connectivity condition. The results are delay-independent in the sense that they hold for~arbitrary bounded delays. Our approach makes use of fundamental concepts from the Non-Negative Matrix Theory in a fairly elementary way.},
	address = {Ann Arbor, MI},
	booktitle = {12th IFAC Workshop on Time Delay Systems (TDS 2015)},
	pages = {pp. 159-164}
}
@conference {
	title = {Event Based Control of Linear Systems with Stochastic Perturbations},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2015},
	month = {06/2015},
	abstract = {In this paper, an event-based control strategy for~linear systems under disturbances is presented where the control~input generator generates a control which tries to mimic a state~feedback control between two successive events. The control input~is generated in such a way that the error between the state of~this system and the continuous state feedback system is bounded.~The event generator triggers an event based on this error and the~control input generator modifies its control function in such a way~that it makes sure that the error generated up to this triggering~instance is reduced to zero and thus it does not have any effect on~the future value of the state regardless of the stability of the plant.~It is also shown that under this event triggering mechanism, the~control input generator generates the control in such a way that~this error bound could be made arbitrarily small.~},
	address = {Krakow, Poland},
	booktitle = {1st IEEE International Conference on Event-Based Control, Communication, and Signal Processing (EBCCSP 2015)}
}
@conference {
	title = {Event Based Distributed Collaborative Control and the Value of Information},
	author = {Baras, John S.},
	year = {2015},
	month = {06/2015},
	address = {Krakow, Poland},
	booktitle = {First International Conference on Event-Based Control, Communication and Signal Processing}
}
@conference {
	title = {Distributed Learning for Collaborative Inference and Decision Making in Multi-Agent Systems},
	author = {Baras, John S.},
	year = {2015},
	month = {06/2015},
	address = {Stuttgart, Germany},
	organization = {Institute for Systems Theory and Automatic Control, University of Stuttgart}
}
@conference {
	title = {Motion Planning in Dynamic Environment with Bounded Time Temporal Logic Specifications},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2015},
	month = {06/2015},
	abstract = {In this paper, we consider the problem of robotic~motion planning that satisfies some bounded time high-level~specifications. Although temporal logic can efficiently express~high-level specifications such as coverage, obstacle avoidance,~temporal ordering of tasks etc., it fails to address~problems~with explicit timing constraints. The inherent limitations of~Linear Temporal Logic (LTL) to address problems with explicit timing constraints have been overcome by translating the~planning problem from the workspace of the robot to a~higher dimensional space called spacetime where the existing~LTL semantics and grammar are sufficient to mathematically~formulate the bounded time high-level specifications. A discrete~path will be generated, that will meet the specifications with all~timing constraints and, at the same time, it will optimize some~cost function. A continuous trajectory satisfying the continuous~dynamics of the robot will be generated from the discrete path~using proper control laws.},
	address = {Torremolinos, Spain},
	booktitle = {23rd Mediterranean Conference on Control and Automoation (MED 2015)},
	pages = {pp. 973-979}
}
@conference {
	title = {Distributed Consensus Networks of Neutral Type},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {06/2015},
	abstract = {We propose and study a network of autonomous agents which evolve their state under a distributed consensus algorithm of non-linear neutral type. We provide sufficient conditions for convergence to a common consensus point, by means of a stability in variation argument and fixed point theory. Our approach provides both an estimation on the rate of convergence and an implicit expression for the consensus point.},
	address = {Torremolinos, Spain},
	booktitle = {23rd Mediterranean Conference on Control and Automoation (MED 2015)},
	pages = {pp. 1087-1092}
}
@conference {
	title = {Trust-Aware Optimal Crowdsourcing With Budget Contraint},
	author = {Liu, Xiangyang., He, He., Baras, John S.},
	year = {2015},
	month = {06/2015},
	abstract = {Crowdsourcing has been extensively used for aggregating data from a large pool of workers. In a real crowdsourcing market, each answer obtained from a worker incurs cost. The cost is associated with both the level of trustworthiness of workers and the difficulty of tasks. Typically, access to expert-level (more trustworthy) workers is more expensive than to average crowd and completion of a challenging task is more costly than a click-away question. In this paper, we address the problem of optimal assignment of heterogeneous tasks to workers of varying trust levels with budget constraint. Specifically, we design a trust-aware task allocation algorithm that takes as inputs the estimated trust of workers and pre-set budget and outputs the optimal assignment of tasks to workers. We derive the bound of total error probability that relates to budget, trustworthiness of crowds, and costs of obtaining labels from crowds naturally. Higher budget, more trustworthy crowds, and less costly jobs result in lower theoretical bound. Our allocation scheme does not depend on the specific design of the trust evaluation component. Therefore, it can be combined with generic trust evaluation algorithms. Our algorithm outperforms state-of-the-art by up to 30\% on real data.},
	address = {London, UK},
	booktitle = {IEEE International Conference on Communications (ICC 2015)},
	pages = {pp. 1176-1181}
}
@conference {
	title = {Modeling the Alzheimer{\textquoteright}s Disease Network},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2015},
	month = {06/2015},
	address = {Antibes - Juan les Pins France},
	booktitle = {1st International Conference on Mathematical NeuroScience (ICMNS 2015)}
}
@conference {
	title = {A Model-Based System Engineering Framework for Healthcare Management with Application to Diabetes Mellitus},
	author = {Katsipis, Iakovos M., Baras, John S.},
	year = {2015},
	month = {05/2015},
	abstract = {We describe a framework for Health Care Management Systems using modern Model-Based Systems Engineering methodologies and apply it to Diabetes Mellitus. We describe the desired architecture of such systems. We include a Controlled Hidden Markov Chain model for diabetes disease progression with three states, three diagnostic tests, ten interventions, three types of patients. We develop three methods for computing tradeoffs between health care cost and health care quality. One is an exhaustive Monte Carlo simulation and the other two use multi-criteria optimization with full and partial disease state information. The latter obtain similar results at a fraction of the time of the first. We demonstrate the powerful capabilities of such a framework via examples and problems of practical healthcare significance.},
	address = {Telecom ParsTech, Paris},
	booktitle = {26th International Conference on Software \& Systems Engineering and their Applications}
}
@conference {
	title = {Health Care Management System for Diabetes Mellitus: A Model-Based Systems Engineering Framework},
	author = {Katsipis, Iakovos M., Baras, John S.},
	year = {2015},
	month = {05/2015},
	address = {Boston, Massachusetts},
	booktitle = {Medical Informatics World Conference}
}
@conference {
	title = {Model-Based Systems Engineering for Networked CPS Research and Education},
	author = {Baras, John S.},
	year = {2015},
	month = {04/2015},
	address = {Seattle, WA},
	booktitle = {2015 CPS Summit}
}
@conference {
	title = {A Systems Approach to Model a Micro-Grid Cyber-Physical System in Urban Cities},
	author = {A. I. Yasser, Baras, John S.},
	year = {2015},
	month = {03/2015},
	address = {Pittsburgh, PA},
	booktitle = {10th Carnegie Mellon Conference on the Electricity Industry, Testbeds for Smart Grids and Smart Cities: Means of Learning}
}
@conference {
	title = {Component Based Modeling of Routing Protocols for Mobile Ad Hoc Networks},
	author = {Paraskevas, Evripidis., Baras, John S.},
	year = {2015},
	month = {03/2015},
	abstract = {Routing protocols perform several functionalities and can be considered as complex software systems. The design and performance analysis of these protocols is difficult and complex and most of them are not adaptable to changes of the environment. In this paper, we present a component based methodology for modeling mobile ad hoc routing protocols. Componentization is used for modeling and analysis of complex systems, because it introduces modularity in protocol design and reusability of designed components across protocols of the same class. We define the fundamental components of the routing protocols based on their functionalities and investigate their interactions. More specifically, we present an initial investigation of the influence of the separate components on the performance metrics of the protocol, such as delay, packet delivery ratio and routing overhead. Proactive routing protocols are being examined and we consider OLSR and DSDV as use cases for our methodology. In addition, we propose an adaptive reusable modification in the Routing Metrics component of OLSR that lead to better overall performance in energy constrained environments.},
	address = {Baltimore, MD},
	booktitle = {49th Annual Conference on Information Sciences and Systems}
}
@conference {
	title = {"Privacy Preserving Node Selection: A Physical Layer Approach (Summary)},
	author = {Jain, Shalabh., Baras, John S.},
	year = {2015},
	month = {03/2015},
	abstract = {Distributed monitoring and sensing networks are~ubiquitous in current technological systems. Security and efficiency~of the data aggregation and fusion process are key~determinants in the adoption of these systems. The principal~thesis investigated in this paper is the role of privacy in providing security guarantees for such networks. We demonstrate that two level~hierarchy (or partition) in information fusion networks~can be used to ensure security in several adversarial scenarios.~We propose a privacy preserving physical layer framework to~generate such a hierarchical structure. We illustrate the security~of this framework and its application to low power sensor~networks.},
	address = {Baltimore, MD},
	booktitle = {49th Annual Conference on Information Sciences and Systems},
	pages = {pp. 1-6}
}
@conference {
	title = {Smart Grid Integrated Modeling Hubs Linked to Tradeoff Analysis and Validation},
	author = {Baras, John S.},
	year = {2015},
	month = {03/2015},
	address = {Pittsburgh, PA},
	booktitle = {10th CMU Electricity Conference},
	organization = {Carnegie Mellon University}
}
@conference {
	title = {Trust-Aware Social Recommended System Design},
	author = {Gao, Peixin., Baras, John S., Golbeck, Jennifer.},
	year = {2015},
	month = {02/2015},
	address = {ESEOM Angers, Loire Valley, France},
	booktitle = {1st International Conference on Information Systems Security and Privacy},
	pages = {pp. 19-28}
}
@conference {
	title = {A Framework for Model-Based Systems Engineering for CPS with Emphasis on Design Space Exploration Methods and Tools},
	author = {Baras, John S.},
	year = {2015},
	month = {02/2015},
	address = {Link{\"o}ping, Sweden},
	booktitle = {2015 MODPROD Workshop},
	organization = {Link{\"o}ping University}
}
@conference {
	title = {Distributed Coordination in Heterogeneous Power Grids: A Fresh Model-Based Approach},
	author = {Baras, John S.},
	year = {2015},
	month = {02/2015},
	address = {Pittsburgh, PA},
	booktitle = {9th CMU Electricity Conference},
	organization = {Carnegie Mellon University}
}
@conference {
	title = {Physical Layer Methods for Privacy Provision in Distributed Control and Inference},
	author = {Jain, Shalabh., Ta, Tuan., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {Distributed control, decision and inference schemes are ubiquitous in many current technological systems ranging from sensor networks, collaborative teams of humans and robots, and information retrieval systems. Privacy, both location and identity, is critical for many of these systems and applications. The principal thesis investigated in this paper is that the utilization of physical layer methods and implementation techniques substantially strengthens privacy in the associated algorithms and systems. In fact it is argued that without the utilization of such physical layer methods it may be expensive to have provable levels of security in these systems. We analyze the performance of such physical layer techniques. We then utilize these techniques to provide provable privacy in distributed control, decision and inference algorithms. We demonstrate the results in context of distributed Kalman filtering. We develop useful metrics to measure privacy in these distributed systems. We investigate quantitatively the effects of privacy loss on the performance of the systems.},
	address = {Los Angeles, California},
	booktitle = {53rd IEEE Conference on Decision and Control},
	pages = {pp. 1383-1388}
}
@conference {
	title = {Collaborative Extremum Seeking for Welfare Optimization},
	author = {Menon, Anup., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {This paper addresses a distributed, model-free optimization problem in the context of multi-agent systems.The set-up comprises of a fixed number of agents, each of which can pick an action and receive/measure a private utility function that can depend on the collective actions taken by all agents. The exact functional form (or model) of the agent utility functions is unknown, and an agent can only measure the numeric value of its utility. The objective of the multi agent system is to optimize the welfare function (i.e. sum of the individual utility functions). A model-free, distributed, on-line learning algorithm is developed that achieves this objective. The proposed solution requires information exchange between the agents over an undirected, connected communication graph,and is based on ideas from extremum seeking control. A result on local convergence of the proposed algorithm to an arbitrarily small neighborhood of a local minimizer of the welfare function is proved. Application of the solution to distributed control of wind turbines for maximizing wind farm-level power capture is explored via numerical simulations. Also included is a novel analysis of a dynamic average consensus algorithm that maybe of independent interest.},
	address = {Los Angeles, California},
	booktitle = {53rd IEEE Conference on Decision and Control},
	pages = {pp. 346-351}
}
@conference {
	title = {An Extension of the Method of Multipliers for Distributed Nonlinear Programming},
	author = {Matei, Ion., Baras, John S., Nabi, Marzieh., Kurtoglu, Tolga.},
	year = {2014},
	month = {12/2014},
	abstract = {In this paper we consider a distributed optimization problem, where a set of agents interacting through a communication graph have as common goal the minimization of a function expressed as a sum of (possibly non-convex) differentiable functions. Each function in the sum corresponds to an agent and each agent has associated an equality constraint. In this paper we investigate how the standard method of multipliers can be used to solve an optimization problem with equality constraints in a distributed manner. The method of multipliers is applied to a lifted optimization problem whose solution embeds the solution of the original problem. We modify the standard convergence results to deal with the fact the (local) minimizers of the lifted optimization problem are not regular, as a results of the distributed formulation},
	booktitle = {53rd IEEE Conference on Decision and Control},
	pages = {pp. 6951-6956},
	organization = {Los Angeles, California, USA.}
}
@conference {
	title = {Social Network Ad Allocation via Hyperbolic Embedding},
	author = {Gao, Peixin., Miao, Hui., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {With the increasing popularity and ubiquity of online social networks (SNS), many advertisers choose to post their advertisements (Ads) within SNS. As a central problem for Ad platforms, Ad allocation is to maximize its revenue without overcharging advertisers, and it has received increasing attention from both industry and academia. The offline approach is a high dimensional integer programming problem with constraints incorporating potential allocation requirements from advertisers. In this paper we investigate the SNS Ad allocation problem in a single target group setting, study the connection of SNS advertising and hyperbolic geometry, and propose an approximation using hyperbolic embedding, which not only reduces the dimensionality of SNS Ad allocation problem significantly, but also provides a general framework for designing allocation strategies incorporating business rules. We evaluate the optimality and efficiency of our approach.},
	booktitle = {53rd IEEE Conference on Decision and Control},
	pages = {pp. 4875-4880},
	organization = {Los Angeles, California, USA.}
}
@conference {
	title = {Load Balancing with Almost Blank Subframe Control in Heterogeneous Cellular Networks},
	author = {Sung, Doo-hyun., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {In heterogeneous cellular networks, the network capacity can be significantly enhanced via user offloading between macro-- and Pico-tier. Due to the strong cross-tier interference from macrocells to picocells in co-channel deployment, the user offloading needs to be jointly optimized with macrocells{\textquoteright} transmit power nulling, i.e., almost blank subframes (ABSs) in 3GPP LTEAsystems. In this paper, we discuss the network-wide utility maximization problem where the cell association and the number of ABSs are jointly optimized. Due to the NP-hardness of the formulated problem, an online heuristic algorithm is proposed where (i) user load is re-distributed based on users{\textquoteright} expected data rate by handover for the current number of ABSs, and (ii)the current number of ABSs is changed (increased or decreased)by estimating the possible users to be offload based on users{\textquoteright} expected data rate by handover and ABS change in a gradient descent manner. Through simulations, we demonstrate that the proposed algorithm not only improves the average data rate of users, but also achieves better fairness among users.},
	address = {Austin, Texas},
	booktitle = {IEEE Globecom 2014 - Wireless Communication Symposium},
	pages = {pp. 4125-4131}
}
@conference {
	title = {Utility-based Almost Blank Subframe Optimization in Heterogeneous Cellular Networks},
	author = {Sung, Doo-hyun., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {Heterogeneous cellular networks are expected to provide capacity enhancement and user offloading with cell range expansion. Under this circumstance, downlink cross-tier interference from macro base stations to pico mobile stations especially in the expanded range is a challenging problem. To mitigated this problem, the use of almost blank subframes (ABSs)has been proposed in 3GPP LTE-A systems. The issues are how many ABSs are configured, and how pico base stations schedule their pico mobile stations to configured ABSs. In this paper,we study the optimal number of ABSs along with pico mobile station scheduling in ABSs by formulating a utility maximization problem with constraints of minimum required data rate of picomobile stations in the expanded range. To solve the optimization problem, we first propose an algorithm for each pico base station to schedule pico mobile stations onto ABSs and non-ABSs, in away that if their local utility is maximized for a given number of ABSs, then the optimal number of ABSs is obtained by maximizing the network-wide utility. Through simulations, we demonstrated that the proposed scheme not only can improve the network-wide utility, can also provide fairness among mobile stations.},
	address = {Austin, Texas},
	booktitle = {IEEE Globecom 2014 - Wireless Communication Symposium},
	pages = {pp. 4132-4137}
}
@conference {
	title = {Hardware Software Co-design for Automotive CPS using Architecture Analysis and Design Language},
	author = {Zhou, Yuchen., Baras, John S., Wang, Shige.},
	year = {2014},
	month = {12/2014},
	abstract = {Modern cyber-physical system (CPS) has a close relationship between software and physical system. Automotive embedded system is a typical CPS, as physical chips, sensors and actuators are physical components and software embedded within are the cyber components. The current stage of embedded systems is highly complex in architecture design for both software and hardware. It is common in industrial practice that high level control algorithm development and low level code implementation on hardware platforms are developed separately with limited shared information.However, software code and hardware architecture become closely related with the increasing complexity.Correlated requirements and dependencies between hardware end software are emerging problems of industrial practice. We demonstrate in this paper a method to link model based system design with real-time simulations and analysis of the architecture model. This allows hardware software co-design and thus early selection of hardware architecture.},
	address = {Rome, Italy},
	booktitle = {5th Analytic Virtual Integration of Cyber-Physical Systems Workshop (AVICPS 2014)}
}
@conference {
	title = {Learning Hand Movements from Markerless Demonstrations for Humanoid Tasks},
	author = {Mao, Ren., Yang, Yezhou., Fermuller, Cornelia., Aloimones, Yiannis., Baras, John S.},
	year = {2014},
	month = {11/2014},
	abstract = {We present a framework for generating trajectories of the hand movement during manipulation actions from demonstrations so the robot can perform similar actions in new situations. Our contribution is threefold: 1) we extract and transform hand movement trajectories using a state-of-the-art markerles full hand model tracker from Kinect sensor data; 2)we develop a new bio-inspired trajectory segmentation method that automatically segments complex movements into action units, and 3) we develop a generative method to learn task specific control using Dynamic Movement Primitives (DMPs).Experiments conducted both on synthetic data and real data using the Baxter research robot platform validate our approach.},
	address = {Madrid, Spain},
	booktitle = {2014 IEEE-RAS International Conference on Humanoid Robots (Humanoids 2014)},
	pages = {pp. 938-943}
}
@conference {
	title = {Maximizing Output Power of a CFPG Micro Energy-Harvester for Wearable Medical Sensors},
	author = {Dadfarnia, Mehdi., Sayrafian, Kamran., Mitcheson, Paul., Baras, John S.},
	year = {2014},
	month = {11/2014},
	abstract = {Energy Harvesting refers to the process ofcapturing and storing energy from the ambientenvironment. Kinetic energy harvested from the human bodymotion seems to be one of the most convenient and attractivesolutions for wearable wireless sensors in healthcareapplications. Due to their small size, such sensors are oftenpowered by small batteries which might necessitate frequentrecharge or even sensor replacement. Energy harvesting canprolong the battery lifetime of these sensors. This could directlyimpact their everyday use and significantly help theircommercial applications such as remote monitoring. In thispaper, our aim is to develop a Simulink model of the CFPGdevice that can be used to study temporal behavior of thegenerated power. Having such a dynamic model, not only helpsto have a more accurate estimation of the amount of powergenerated from various human movements, but also allows us tofurther optimize the design parameters of the micro-harvester(e.g. size/dimension, electrostatic holding force, etc.) with thecharacteristics of the input acceleration (i.e. human activity).},
	address = {Athens, Greece},
	booktitle = {4th International Conference on Wireless Mobile Communication and Healthcare},
	pages = {pp. 218-221}
}
@conference {
	title = {A System Engineering Framework for Multi-Criteria Performance Evaluation of Healthcare Process and Systems},
	author = {Katsipis, Iakovos M., Baras, John S.},
	year = {2014},
	month = {10/2014},
	abstract = {Extended Abstract: Health expenditures for diabetes and its complications totals 376 billion dollar (USD) and is expected to exceed 490 USD billion by 2030. Developed world countries count for 80\% and US for 52\% of these total health expenditures. Type 2 diabetes is a chronic disease with long term complications as blindness, renal failure and increased risk for stroke and myocardial infraction. There are several studies related to prediction of diabetes type 2. Most famous models and widely used are the IRIC, QDScore, DESIR. All models seek to be aligned with age, BMI and waist circumference as variables, however, the performance of each model varies between countries, age, sex, and adiposity. One of the methods that have been used in the past to define the risks and performance of several treatments for diabetes type 2, is Markov chain models constructed for a heterogeneous subscriber population, and used to examine the long-run effects of particular utilization patterns on disease functioning.


Systems Engineering (SE) is an approach combining the advantage of model-based systems descriptions, based on modular components, integrated with sophisticated tradeoff analysis and design space exploration, to design and analyze the performance of complex systems in many domains, ranging from engineering, to economics, to enterprises, and most recently to healthcare systems and processes [17]. In fact, the recent PCAST report [17] recommends SE as a critical methodology for accelerating improvements in healthcare systems towards higher quality and lower costs. However, there are very few studies using this modern and interdisciplinary approach to healthcare. The present paper describes our research towards developing such a framework for the case of diabetes type 2, that will allow all stakeholders of healthcare to assess the benefits of specific policies, technologies, treatments etc., with~respect to several metrics, including economic metrics. Further we propose that modern SE methodologies are uniquely capable to evaluate the interrelationships between healthcare, information technology and economics. We offer the present study as a prototypical example.


The purpose of the present study is to classify population groups based on diabetic risk, formulate models of structure and behavior, set requirements for treatment performance and construct states (for various relevant processes, including the disease, patients, treatments, technologies). Every state will have different probabilities of disease progression, cost function and health performance. Finally, the results of every state will be used to construct and validate the Markov chain model. From the Markov chain model, for every step, outputs of the model will be total cost, risk, health performance. Also every state will generate a different sum total of cost, health performance and risk. Every state shows different progression of the disease that will need different cost function (combination of treatment and medicine), health function (Qaly). Each step represents the evolution (progression) of the model through time.},
	address = {Washington DC},
	booktitle = {White 2014, The 5th Annual Workshop on Health IT and Economics}
}
@conference {
	title = {Multi-Metric Energy Efficient Routing in Mobile Ad-Hoc Networks},
	author = {Paraskevas, Evripidis., Manousakis, Kyriakos., Das, Subir., Baras, John S.},
	year = {2014},
	month = {10/2014},
	abstract = {Increasing network lifetime by reducing energy consumption across the network is one of the major concerns while designing routing protocols for Mobile Ad-Hoc Networks. In this paper, we investigate the main reasons that lead to energy depletion and we introduce appropriate routing metrics in the routing decision scheme to mitigate their effect and increase the network lifetime. For our routing scheme, we take into consideration multiple layer parameters, such as MAC queue utilization, node degree and residual energy. We integrate our multi-metric routing scheme into OLSR, a standard MANET proactive routing protocol. We evaluate via simulations in NS3 the protocol modifications under a range of different static and mobile scenarios. The main observations are that in static and low mobility scenarios our modified routing protocol leads to a significant increase (5\%-20\%) in network lifetime compared to standard OLSR and slightly better performance in terms of Packet Delivery Ratio (PDR).},
	address = {Baltimore, Maryland},
	booktitle = {Military Communications Conference (MILCOM 2014)},
	pages = {pp. 1146-1151}
}
@conference {
	title = {On the Meaning and Implications of {\textquotedblleft}N{\textquotedblright} in {\textquotedblleft}CNS"},
	author = {Baras, John S.},
	year = {2014},
	month = {10/2014},
	address = {Boston, Massachusetts},
	booktitle = {First Symposium on the Control of Network Systems (SCONES)},
	organization = {Boston University}
}
@conference {
	title = {Security and Trust in a Networked Immersed World: From Components to Systems and Beyond},
	author = {Baras, John S.},
	year = {2014},
	month = {09/2014},
	address = {Crete, Greece},
	organization = {FORTH Institute for Computer Sscience (ICS)}
}
@conference {
	title = {Using Trust in Distributed Consensus with Adversaries in Sensor and Other Networks},
	author = {Liu, Xiangyang., Baras, John S.},
	year = {2014},
	month = {07/2014},
	abstract = {Extensive research efforts have been devoted to distributed consensus with adversaries. Many diverse applications drive this increased interest in this area including distributed collaborative sensor networks, sensor fusion and distributed collaborative control. We consider the problem of detecting Byzantine adversaries in a network of agents with the goal of reaching consensus. We propose a novel trust model that establishes both local trust based on local evidences and global trust based on local exchange of local trust values. We describe a trust-aware consensus algorithm that integrates the trust evaluation mechanism into the traditional consensus algorithm and propose various local decision rules based on local evidence. To further enhance the robustness of trust evaluation itself, we also provide a trust propagation scheme in order to take into account evidences of other nodes in the network. Then we show by simulation that the trust-aware consensus algorithm can effectively detect Byzantine adversaries and excluding them from consensus iterations even in sparse networks with connectivity less than 2f + 1, where f is the number of adversaries. These results can be applied for fusion of trust evidences as well as for sensor fusion when malicious sensors are present like for example in power grid sensing and monitoring.},
	address = {Salamanca, Spain},
	booktitle = {17th International Conference on Information Fusion (Fusion 2014)}
}
@conference {
	title = {Improving Smartphone Battery Life Utilizing Device-to-device Cooperative Relays Underlaying LTE Networks},
	author = {Ta, Tuan., Baras, John S., Zhu, Chenxi.},
	year = {2014},
	month = {06/2014},
	abstract = {The utility of smartphones has been limited to a great extent by their short battery life. In this work, we propose a new approach to prolonging smartphone battery life. We introduce the notions of valueless and valued battery, as being the available battery when the user does or does not have access to a power source, respectively. We propose a cooperative system where users with high battery level help carry the traffic of users with low battery level. Our scheme helps increase the amount of valued battery in the network, thus it reduces the chance of users running out of battery early. Our system can be realized in the form of a proximity service (ProSe) which utilizes a device-to-device (D2D) communication architecture underlaying LTE. We show through simulations that our system reduces the probability of cellular users running out of battery before their target usage time (probability of outage). Our simulator source code is made available to the public.},
	address = {Sydney, Australia},
	booktitle = {Proceedings of the IEEE ICC 2014 - Wireless Communications Symposium,},
	pages = {pp. 5264-5268}
}
@conference {
	title = {Security and Trust in a Networked Immersed World: From Components to Systems and Beyond},
	author = {Baras, John S.},
	year = {2014},
	month = {06/2014},
	address = {Athens, Greece},
	booktitle = {2nd Hellenic Forum for Science, Innovation and Technology},
	organization = {NCSR Demokritos}
}
@conference {
	title = {The Next Wonder: Using Models for {\textquotedblleft}Making{\textquotedblright} Products and Services},
	author = {Baras, John S.},
	year = {2014},
	month = {05/2014},
	address = {Stockholm, Sweden},
	booktitle = {Tage Erlander Guest Professorship Inaugural Lecture},
	organization = {KTH, Royal Institute of Technology}
}
@conference {
	title = {Network Tomography: New Rigorous Approaches for Discrete and Continuous Problems},
	author = {Baras, John S.},
	year = {2014},
	month = {05/2014},
	abstract = {We consider several rigorously defined network tomography problems from applications ranging from communication networks, to social networks. The universal abstraction we develop involves the inference of various network structural and parametric properties form observations of certain {\textquotedblleft}probing{\textquotedblright} processes from a subset of network nodes which we call the boundary nodes of the network. We show that these problems lead to mathematical problems of {\textquotedblleft}deconvolution{\textquotedblright} over unconventional semirings, inversion of integrals over trees of the underlying graph, Radon transform over symmetric spaces, and completion of sparse matrices albeit in non-conventional semirings. We illustrate applications in several applied problems.Some of the problem formulations and solutions are inspired by generalizations of {\textquotedblleft}electric impedance problems{\textquotedblright} in various non-nonconventional spaces. Some of the solutions have a variational interpretation.},
	address = {Athens, Greece},
	booktitle = {2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP 2014)},
	pages = {pp. 611-614}
}
@conference {
	title = {A Fresh Look at Network Science: Interdependent Multigraphs Models Inspired from Statistical Physics},
	author = {Baras, John S.},
	year = {2014},
	month = {05/2014},
	abstract = {We consider several challenging problems in complex networks(communication, control, social, economic, biological, hybrid) as problems in cooperative multi-agent systems. We describe a general model for cooperative multi-agent systems that involves several interacting dynamic multigraphs and identify three fundamental research challenges underlying these systems from a network science perspective. We show that the framework of constrained coalitional network games captures in a fundamental way the basic tradeoff of benefits vs. cost of collaboration, in multi-agent systems, and demonstrate that it can explain network formation and the emergence or not of collaboration. Multi-metric problems in such networks are analyzed via a novel multiple partially ordered semirings approach. We investigate the interrelationship between the collaboration and communication multigraphs in cooperative swarms and the role of the communication topology, among the collaborating agents, in improving the performance of distributed task execution. Expander graphs emerge as efficient communication topologies for collaborative control. We relate these models and approaches to statistical physics.},
	address = {Athens, Greece},
	booktitle = {2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP 2014)},
	pages = {pp. 497-500}
}
@conference {
	title = {Distributed Learning in Collaborative Control and Decision Making},
	author = {Baras, John S.},
	year = {2014},
	month = {05/2014},
	address = {Thessaloniki, Greece},
	organization = {Aristotle University of Thessaloniki}
}
@conference {
	title = {Hyperbolic Embedding in Communication and Social Networks},
	author = {Baras, John S.},
	year = {2014},
	month = {05/2014},
	address = {Volos, Greece},
	organization = {University of Thessaly}
}
@conference {
	title = {Simple Distributed Control of Networked CPS: Indirect and Direct Communications},
	author = {Baras, John S.},
	year = {2014},
	month = {04/2014},
	abstract = {We consider a system of N agents, each picking actions from a finite set and receiving a payoff depending on the actions of all agents. The exact form of the payoffs is unknown and only their values can be measured by the respective agents. A decentralized algorithm was recently proposed by Young et al and in the author{\textquoteright}s earlier work, that, in this setting, leads to the agents picking welfare optimizing actions under some restrictive assumptions on the payoff structure. We have very recently improved the algorithm to incorporate exchange of certain bit-valued information between the agents over a directed communication graph. An interaction graph is introduced to encode known interactions in the system. Restrictions on the payoff structure are eliminated and conditions that guarantee convergence to welfare minimizing actions w.p. 1 are derived under the assumption that the union of the interaction and communication graphs is strongly connected. We next consider the continuous time and continuous state space version of the problem based on ideas from extremum seeking control. A result of local convergence of the proposed algorithm to an arbitrarily small neighborhood of a local minimizer of the welfare function is proved. We include a novel analysis of a dynamic consensus algorithm that may be of independent interest. Stochastic methods are employed throughout in the proofs. Our results show how indirect communications (signaling between the agents via their interactions through the system) and direct communications (direct messages sent between the agents) can complement each other and lead to simple distributed control algorithms with remarkably good performance. There are many applications including management of wind farms, coverage problems in sensor networks, robotic swarm formation control. We close by describing current and future research directions.},
	address = {University of Minnesota , Minneapolis},
	booktitle = {MnDRIVE Seminar Series in Control and Robotics},
	organization = {College of Science and Engineering}
}
@conference {
	title = {Hyperbolic Embedding to the Rescue in Communication and Social Networks},
	author = {Baras, John S.},
	year = {2014},
	month = {04/2014},
	abstract = {We consider the following problems where this embedding provides high performance and efficient solutions. First, we develop greedy backpressure routing algorithms for both static and dynamic wireless networks that result in much better, and even controllable, trade-off between throughput and delay. The solution involves a new combination of greedy hyperbolic routing and backpressure scheduling. Second, we develop a context-aware routing scheme for social networks that aims to increase the relevance of messages shared across a social network. It achieves this by forwarding each message to the most relevant nodes, taking into account both user preferences and the network structure. Again greedy hyperbolic embedding is utilized and a new relevance metric is constructed that incorporates a context similarity measure and network structure, the latter represented by the hyperbolic distance between nodes. Third, we consider the advertisement allocation problem for large social networks. We show how hyperbolic embedding can be utilized again to formulate the underlying optimization problem in a continuum that not only reduces dramatically the dimensionality of the advertisement allocation problem from that of the associated integer programming formulation but also provides a general framework for designing allocation strategies incorporating business rules. Fourth, we consider network tomography problems, whereby properties of internal nodes and links of the network are dynamically inferred from iterated adaptive measurements on a subset of nodes, called boundary nodes. Again using hyperbolic embedding we demonstrate that these tomography problems can be formulated as true tomography problems in hyperbolic space, involving inversion of Radon transforms on symmetric spaces; the tomographic "integrals" are now over paths of the graph},
	address = {University of Minnesota , Minneapolis},
	organization = {College of Science and Engineering}
}
@conference {
	title = {The glymphatic system and Alzheimer{\textquoteright}s disease: possible connection?},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2014},
	month = {04/2014},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is the most common cause of dementia in the elderly, accounting for 60-80\% of all dementias. Symptoms of AD include memory loss (initially short term, later on long term as well), changes in mood and sun-downing. Magnetic resonance imaging (MRI) shows diffuse cortical atrophy and enlargement of the lateral ventricles due to neuronal cell loss. At the cellular level, neuroinflammation, activation of microglia, deposition of beta amyloid (Aβ) in the brain parenchyma and cerebral vasculature, and increases in the permeability of the bloodbrain barrier (BBB) have all been observed as well. A newly developed theory purports that the glymphatic system of the brain may play a significant role in AD pathogenesis. This paper presents an initial mathematical model of the glymphatic system and studies how changes of transporter density and deposition of Aβ at the BBB changes clearance of Aβ. Changes in local neuronal cell density were also modeled. This represents one of the first attempts to computationally study the role of the glymphatic system in AD.},
	address = {Chamonix, France},
	booktitle = {Biotechno 2014},
	pages = {pp. 15-19}
}
@conference {
	title = {A Rigorous Framework for Model-Based Systems Engineering and Applications},
	author = {Baras, John S.},
	year = {2014},
	month = {04/2014},
	address = {Gaithersburg, Maryland},
	booktitle = {NIST-wide},
	organization = {NIST}
}
@conference {
	title = {A Systems Engineering Approach to Collaborative Coordination of UAS in the NAS with Safety Guarantees},
	author = {Moschler, Jacob., Zhou, Yuchen., Baras, John S., Joh, Jungwoo.},
	year = {2014},
	month = {04/2014},
	abstract = {We develop new fundamental methodologies for high performance and provably safe autonomous and collaborative control and operation of autonomous unmanned aerial systems (UAS) in the national airspace (NAS), where both UAS and manned aircraft fly. The proposed framework is model-based, and emphasizes multiple scales in time and space as well as hybrid systems mathematics to capture both the analog and logical components of control functionalities. We develop on-line control laws that allow for multiple UAS agents to reconfigure to different formations with proofs of safety and convergence while navigating in integrated airspace with piloted air vehicles. We demonstrate our results in simulated scenaria with both cooperative and uncooperative air vehicles.},
	address = {Herndon, Virginia},
	booktitle = {Proceedings of the 2014 Integrated Communications Navigation and Surveillance (ICNS) Conference},
	pages = {pp. U1-1 -U1-12}
}
@conference {
	title = {A System Engineering Approach to Collaborative Coordination of UASV{\textquoteright}s in the NAS with Safety Guarantees},
	author = {Moschler, Jacob., Zhou, R. Yuchen, Baras, John S.},
	year = {2014},
	month = {04/2014},
	abstract = {We develop new fundamental methodologies for high performance and provably safe autonomous unmanned aerial systems (UAS) in the national airspace (NAS), where both UAS and manned aircraft fly. The proposed framework is model-based, and emphasizes multiple scales in time and space as well as hybrid systems mathematics to capture both the analog and logical components of control functionalities. We develop on-line control laws that allow for multiple UAS agents to reconfigure to different formations with proofs of safety and convergence while navigating in integrated airspace with piloted air vehicles. We demonstrate our results in simulated scenaria with both cooperative and uncooperative air vehicles.},
	address = {Herndon, VA},
	booktitle = {Integrated Communications Navigation and Surveillance Conference (ICNS)},
	pages = {pp. U1-1 - U1-12}
}
@conference {
	title = {Simple Distributed Control of Networked CPS: Indirect and Direct Communications},
	author = {Baras, John S.},
	year = {2014},
	month = {04/2014},
	address = {Notre Dame, Indiana},
	organization = {University of Notre Dame}
}
@conference {
	title = {A Distributed Algorithm with Bit-valued Communications for Multi-agent Welfare Optimization},
	author = {Baras, John S.},
	year = {2014},
	month = {03/2014},
	abstract = {We consider a system of N agents, each picking actions from a finite set and receiving a payoff depending on the actions of all agents. The exact form of the payoffs is unknown and only their values can be measured by the respective agents. A decentralized algorithm was recently proposed by Young et al and in the authors{\textquoteright} earlier work, that, in this setting, leads to the agents picking welfare optimizing actions under some restrictive assumptions on the payoff structure. We have very recently improved the algorithm to incorporate exchange of certain bit-valued information between the agents over a directed communication graph. An interaction graph is introduced to encode known interactions in the system. Restrictions on the payoff structure are eliminated and conditions that guarantee convergence to welfare minimizing actions w.p. 1 are derived under the assumption that the union of the interaction and communication graphs is strongly connected. Our results show how indirect communications (signaling between the agents via their interactions through the system) and direct communications (direct messages sent between the agents) can complement each other and lead to simple distributed control algorithms with remarkably good performance. There are many applications including management of wind farms, coverage problems in sensor networks, robotic swarm formation control. We close by describing current and future research directions.},
	booktitle = {Information Systems Laboratory},
	organization = {Stanford University}
}
@conference {
	title = {Trust in Networks and Networked Systems},
	author = {Baras, John S.},
	year = {2014},
	month = {03/2014},
	address = {Berkeley, CA},
	booktitle = {TRUST Seminar},
	organization = {University of California}
}
@conference {
	title = {A Rigorous Framework for Model-Based Systems Engineering and Applications},
	author = {Baras, John S.},
	year = {2014},
	month = {03/2014},
	address = {Palo Alto, CA},
	organization = {Xerox PARC}
}
@conference {
	title = {General CPS Architecture Concepts},
	author = {Baras, John S.},
	year = {2014},
	month = {03/2014},
	address = {Arlington, VA},
	booktitle = {2014 NSF CPS Reference Architectures Workshop}
}
@conference {
	title = {A Rigorous Framework for Model-Based Systems Engineering and Applications},
	author = {Baras, John S.},
	year = {2014},
	month = {01/2014},
	address = {East Hartford, CT},
	organization = {United Technologies Research Center (UTRC)}
}
@conference {
	title = {Increasing Recommendation Accuracy and Diversity via Social Networks Hyperbolic Embedding},
	author = {Pouli, Vasiliki., Baras, John S., Arvanitis, Anastasios.},
	year = {2014},
	month = {01/2014},
	abstract = {Several applications are built around sharing information by leveraging social network connections. For example, in social buying sites like Groupon, a deal is usually forwarded to interested recipients through their social graph. A primary goal is to improve user satisfaction by maximizing the relevance of the shared message to the target audience. The more personalized products or offers you promote to the users the greater is the chance to attract them and increase your revenues. To create more personalized products, one should consider not only offering accurate recommendations but also diverse, since diversity plays an important factor and should not be disregarded. In this work, we address this problem by proposing a social network hyperbolic embedding that exploits both social connections and user preferences aiming at enhancing the relevance of recommendations and increasing their diversity and accuracy by ensuring that each message will be delivered to the most interested users.},
	address = {Las Vegas, Nevada},
	booktitle = {IEEE Consumer Communications and Networking Conference 2014},
	pages = {pp. 225-232}
}
@conference {
	title = {Security and Trust in a Networked Immersed World: From Components to Systems and Beyond},
	author = {Baras, John S.},
	year = {2014},
	month = {01/2014},
	address = {East Hartford, CT},
	organization = {United Technologies Research Center (UTRC)}
}
@conference {
	title = {Per-se Privacy Preserving Solution Methods Based on Optimization},
	author = {Weeraddana, P. C., Athanasiou, G., Fischione, Carlo., Baras, John S.},
	year = {2013},
	month = {12/2013},
	abstract = {Ensuring privacy is an essential requirement in various contexts, such as social networks, healthcare data, ecommerce, banks, and government services. Here, different entities coordinate to address specific problems where the sensitive problem data are distributed among the involved entities and no entity wants to publish its data during the solution procedure. Existing privacy preserving solution methods are mostly based on cryptographic procedures and thus have the drawback of substantial computational complexity. Surprisingly, little attention has been devoted thus far to exploit mathematical optimization techniques and their inherent properties for preserving privacy. Yet, optimization based approaches to privacy require much less computational effort compared to cryptographic variants, which is certainly desirable in practice. In this paper, a unified framework for transformation based optimization methods that ensure privacy is developed. A general definition for the privacy in the context of transformation methods is proposed. A number of examples are provided to illustrate the ideas. It is concluded that the theory is still in its infancy and that huge benefits can be achieved by a substantial development.},
	address = {Florence, Italy},
	booktitle = {52nd IEEE Conference on Decision and Control},
	pages = {pp. 206-211}
}
@conference {
	title = {Distributed Algorithms for Optimization Problems with Equality Constraints},
	author = {Matei, Ion., Baras, John S.},
	year = {2013},
	month = {12/2013},
	abstract = {In this paper we introduce two discrete-time, distributed optimization algorithms executed by a set of agents whose interactions are subject to a communication graph. The algorithms can be applied to optimization problems where the cost function is expressed as a sum of functions, and where each function is associated to an agent. In addition, the agents can have equality constraints as well. The algorithms are not consensus-based and can be applied to non-convex optimization problems with equality constraints. We demonstrate that the first distributed algorithm results naturally from applying a first order method to solve the first order necessary conditions for a lifted optimization problem with equality constraints; the solution of our original problem is embedded in the solution of this lifted optimization problem. Using an augmented Lagrangian idea, we derive a second distributed algorithm that requires weaker conditions for local convergence compared to the first algorithm. For both algorithms we address the local convergence properties.},
	address = {Florence, Italy},
	booktitle = {52nd IEEE Conference on Decision and Control},
	pages = {pp. 2352-2357}
}
@conference {
	title = {Asymptotic Consensus Solutions in Non-Linear Delayed Distributed Algorithms Under Deterministic \& Stochastic Perturbations},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {12/2013},
	abstract = {We consider a multi-agent non-linear delayed model which sustains consensus type of solutions. We use fixed point theory arguments to establish sufficient conditions for existence and uniqueness of solutions that converge exponentially fast to a common value with prescribed rate. The conditions depend on the communication topology, the nonlinearity of the model as well as the delay in the propagation of information. Furthermore we test the robustness of our results in the presence of independent time varying perturbations both deterministic and stochastic.},
	address = {Florence, Italy},
	booktitle = {52nd IEEE Conference on Decision and Control},
	pages = {pp. 7821-7826}
}
@conference {
	title = {A Distributed Learning Algorithm with Bit-valued Communications for Multi-agent Welfare Optimization},
	author = {Menon, Anup., Baras, John S.},
	year = {2013},
	month = {12/2013},
	abstract = {A multi-agent system comprising N agents, each picking actions from a finite set and receiving a payoff that depends on the action of the whole, is considered. The exact form of the payoffs are unknown and only their values can be measured by the respective agents. A decentralized algorithm was proposed by Marden et al. and in the authors{\textquoteright} earlier work that, in this setting, leads to the agents picking welfare optimizing actions under some restrictive assumptions on the payoff structure. This algorithm is modified in this paper to incorporate exchange of certain bit-valued information between the agents over a directed communication graph. The notion of an interaction graph is then introduced to encode known interaction in the system. Restrictions on the payoff structure are eliminated and conditions that guarantee convergence to welfare minimizing actions w.p. 1 are derived under the assumption that the union of the interaction graph and communication graph is strongly connected.},
	address = {Florence, Italy},
	booktitle = {Proceedings of the 52nd IEEE Conference on Decision and Control,},
	pages = {pp. 2406-2411}
}
@conference {
	title = {Coordinated Scheduling and Power Control for Downlink Cross-tier Interference Mitigation in Heterogeneous Cellular Networks},
	author = {Sung, Doo-hyun., Baras, John S., Zhu, Chenxi.},
	year = {2013},
	month = {12/2013},
	abstract = {In heterogeneous cellular networks, the deployment~of low-powered picocells provides user offloading and capacity~enhancement. The expansion of a picocell{\textquoteright}s coverage by adding~a positive bias for cell association can maximize these effects.~Under this circumstance, downlink cross-tier interference from~a macro base station to pico mobile stations in the expanded~picocell range deteriorates those pico mobile stations{\textquoteright} performance~significantly. In this paper, a coordinated scheduling~and power control algorithm is proposed, whereby the macro~base station reduces its transmission power for those victim~pico mobile stations in the expanded picocell range only on a~set of resource blocks to minimize performance degradation at~the macro base station. First, the transmission power level is~calculated based on the mobile stations{\textquoteright} channel condition and
QoS requirements. Then, a set of resource blocks is determined~by solving a binary integer programming to minimize the sum~of transmission power reduction subject to victim pico mobile~stations{\textquoteright} QoS constraints. To reduce computational complexity,~we utilize a heuristic algorithm, i.e., max-min greedy method,~to solve the problem. Through system level simulations, we~show that average and 5\%-ile throughputs of victim pico mobile~stations are significantly improved.},
	address = {Atlanta, Georgia},
	booktitle = {IEEE Globecom 2013},
	pages = {pp. 3914-3918}
}
@conference {
	title = {Distributed Trust Based Routing in Mobile Ad-Hoc Networks},
	author = {Jain, Shalabh., Baras, John S.},
	year = {2013},
	month = {11/2013},
	abstract = {Establishing trust and security in ad-hoc networkshas been a long studied problem. Several methods have beenproposed for evaluation and dissemination of trust in suchnetworks, with the goal of providing secure data paths. Wepropose a mechanism to utilize trust metrics derived from variousmethods for secure routing. Our scheme can be used in withexiting on-demand routing protocols with minimal modification.We highlight scenarios that establish the need for associating trustwith a link, rather than just a node. Our scheme incorporatesboth link and node trust to avoid adversarial paths in adistributed manner. We validate via simulation, the securityproperties of our scheme in an ad-hoc network.},
	address = {San Diego, California},
	booktitle = {2013 Military Communications Conference (MILCOM 2013)},
	pages = {pp. 1801-1807}
}
@conference {
	title = {Cerebral vasculature, Alzheimer{\textquoteright}s disease and cerebral amyloid angiopathy: What is the Connection:  A Mathematical Model},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2013},
	month = {11/2013},
	address = {San Diego, CA},
	booktitle = {6th International IEEE EMBS Conference on Neural Engineering}
}
@conference {
	title = {HybridSim: A Modeling and Co-simulation Toolchain for Cyber-Physical Systems},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {10/2013},
	abstract = {Cyber-physical systems (CPS) involve communication networks, computation algorithms, control systems and physical systems. Many CPS, such as Smart Buildings, are subject to very expensive deployment costs and complex network interactions. Thus comprehensive modeling and simulation of such systems are crucial to ensure that they function as intended before deployment. Given the multi-domain nature of CPS, it is more appropriate to use a heterogeneous simulation environment to study system dynamics. In this paper, we design and implement an integrated modeling and co-simulation toolchain, called HybridSim, for the design and simulation of CPS. Firstly, HybridSim can transform and import existing system components from multi-domains into SysML, which enables systems engineers to design CPS with only these imported SysML blocks. Secondly, HybridSim can generate Functional Mock-up Units (FMUs) and configuration scripts directly from SysML designs. Finally, HybridSim can co-simulate these FMUs according to the Functional Mock-up Interface standard to synchronize their corresponding simulators and exchange information between them. We demonstrate the convenience and efficiency of HybridSim using a comprehensive hydronic heating system model for Smart Buildings as the case study to investigate the impact of packet loss and sampling rate introduced by the communication network.},
	address = {Delft, Netherlands},
	booktitle = {Proceedings of 17th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications},
	pages = {pp. 33-40}
}
@conference {
	title = {Distributed Consensus with Byzantine Adversaries},
	author = {Liu, Xiangyang., Gao, Peixin., Baras, John S.},
	year = {2013},
	month = {10/2013},
	abstract = {The problem of distributed consensus algorithms in the presence of Byzantine adversaries has been increasingly important in both distributed computing scenaria and cyber-physical systems. Yet a satisfactory solution to the problem is still being sought due to the fact that Byzantine adversaries can output arbitrary wrong states and even collude to cause worse damages. We aim to solve the problem via detecting adversaries. Related works in multi-party computation in computer science are addressing this type of problem relying on the assumption that adversaries cannot lie about their input values. Works in the control theoretic literature rely on strict and hardly verifiable network robustness conditions. Both lines of research just consider guaranteeing the consensus in the face of adversaries yet neither of them considers detecting adversaries. In this paper a method is proposed to investigate this problem based on the detection of adversaries in the execution of the consensus algorithm. We integrate a trust evaluation mechanism into the consensus algorithm, where trust can be established with the help of a special subset of nodes, namely headers. We propose a two-layer hierarchical framework, where the top layer is a super-step dealing with a vectorized consensus algorithm, and the bottom layer is a sub-step, executing our proposed parallel vectorized voting scheme. The parallel vectorized voting scheme uses the information received by the top layer as an initial trust opinion and then evolves to equilibrium trust opinions. The vectorized consensus algorithm in the top layer utilizes the trust evaluation results provided by the bottom layer to update confidence levels and states. We also derive an upper bound of the number of adversaries that our algorithm can resist in each super-step.},
	address = {Montecello, Illinois},
	booktitle = {Proceedings of 51st Annual Allerton Conference on Communication, Control and Computing}
}
@conference {
	title = {Hyperbolic Embedding to the Rescue in Communication and Social Networks},
	author = {Baras, John S.},
	year = {2013},
	month = {10/2013},
	address = {Murray Hill, NJ},
	booktitle = {2013 Bell Labs {\textendash} NIST Workshop on Large Scale Networks}
}
@conference {
	title = {The Role of Universities and Research Centers in Economic Development: Some Recommendations for Greece},
	author = {Baras, John S.},
	year = {2013},
	month = {10/2013},
	address = {Athens, Greece},
	booktitle = {1st Conference of the Hellenic Innovation Forum, Eugenides Foundation}
}
@conference {
	title = {A Rigorous Framework for Model-Based Systems Engineering and Applications},
	author = {Baras, John S.},
	year = {2013},
	month = {09/2013},
	address = {Niskayuna, NY},
	booktitle = {General Electric Global Controls Symposium}
}
@conference {
	title = {A Coalitional Game Based Approach for Multi-Metric Optimal Routing in Wireless Networks},
	author = {Stai, Eleni., Papavassiliou, Symeon., Baras, John S.},
	year = {2013},
	month = {09/2013},
	abstract = {Future communications consist of an increasing number of wireless parts, while simultaneously need to support the widespread multimedia applications imposed by social networks. These human-machine systems, driven by both real time social interactions and the challenges of the wireless networks{\textquoteright} design, call for efficient and easy to implement, distributed cross-layer algorithms for their operation. Performance metrics such as throughput, delay, trust, energy consumption, need to be improved and optimized aiming at high quality communications. We investigate the coveted throughput-delay trade-off in static wireless multihop networks based on a {\textquotedblleft}computer-aided{\textquotedblright} design of the backpressure scheduling/routing algorithm for networks embedded in hyperbolic space. Both routing and scheduling exploit the hyperbolic distances to orient the packets to the destination and prioritize the transmissions correspondingly. The proposed design provides us with the freedom of controlling its theoretical throughput optimality and of counterbalancing its practical performance through simulations, leading to significant improvements of the throughput-delay trade-off.},
	address = {London, UK},
	booktitle = {Proceedings of IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications: Mobile and Wireless Networks},
	pages = {pp. 1935-1939}
}
@conference {
	title = {On The Convergence Rate of Non-Linear Consensus Networks with Delays},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {09/2013},
	abstract = {We consider a generic non-linear consensus model and prove convergence results to a common value together with prescribed rate of convergence. Instead of a Lyapunov approach we consider a functional metric space and make a fixed point theory argument using contraction mappings. We are restricted to the case of static networks.},
	address = {Toulouse, France},
	booktitle = {9th IFAC Symposium on Nonlinear Control Systems,},
	pages = {pp. 705-710}
}
@conference {
	title = {On the connectivity of non-liner flocking models},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {08/2013},
	abstract = {The problem of collective behavior of autonomous agents is discussed. Based on state dependent communication graphs we analyze a family of nonlinear flocking models by establishing sufficient initial conditions so as connectivity and thus asymptotic flocking is ensured. We discuss models with non-linear uniformly bounded connection rates with and without delays.},
	address = {Mi{\k e}dzyzdroje, Poland},
	booktitle = {18th International Conference on Methods and Models is Automation and Robotics (MMAR 2013)},
	pages = {pp. 800-805}
}
@conference {
	title = {On the connectivity assumption of non-liner flocking models},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {08/2013},
	abstract = {The problem of collective behavior of autonomous agents is discussed. Based on state dependent communication graphs we analyze a family of nonlinear flocking models by establishing sufficient initial conditions so as connectivity and thus asymptotic flocking is ensured. We discuss models with non-linear uniformly bounded connection rates with and without delays.},
	address = {Mi{\k e}dzyzdroje, Poland},
	booktitle = {Proceedings of 8th International Conference on Methods and Models is Automation and Robotics (MMAR 2013)},
	pages = {pp. 800-805}
}
@conference {
	title = {The Promise and Challenges of {\textquotedblleft}Smart{\textquotedblright} Health Information Technology},
	author = {Baras, John S.},
	year = {2013},
	month = {08/2013},
	address = {Beijing, China},
	booktitle = {2nd International Workshop on Artificial Intelligence and Netmedicine (NetMed{\textquoteright}13), part of 23rd International Joint Conference on Artificial intelligence (IJCAI)}
}
@conference {
	title = {Fixed Point Theory Approach to Exponential Convergence in LTV Continuous Time Consensus Dynamics with Delays},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {07/2013},
	abstract = {The problem of continuous linear time varying consensus dynamics is addressed in the presence of constant communication delays. We make a Fixed Point Theory argument with the use of contraction mappings and we state sufficient conditions for exponential convergence to a consensus value with prescribed convergence rate.},
	address = {San Diego, CA},
	booktitle = {SIAM conference on Control and its Application 2013},
	pages = {pp. 129-136}
}
@conference {
	title = {Universities and Research Centers as Agents for Economic Development},
	author = {Baras, John S.},
	year = {2013},
	month = {07/2013},
	address = {Athens, Greece},
	booktitle = {1st Hellenic Forum for Science, Technology and Innovation},
	organization = {NCSR Demokritos}
}
@conference {
	title = {LTI Continuous Time Consensus Dynamics with Multiple and Distributed Delays},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {06/2013},
	abstract = {We study linear time invariant (LTI) continuous time consensus dynamics in the presence of bounded communication delays. Contrary to traditional Lyapunov based methods, we approach the problem using Fixed Point Theory. This method, allows us to create an appropriate complete functional metric space and through contraction mappings to establish the existence and uniqueness of a solution of this model. We explore the case of constant as well as distributed delays.},
	address = {Platanias-Chania, Crete - GREECE},
	booktitle = {21st Mediterranean Conference on Control and Automation},
	pages = {pp. 1495-1501}
}
@conference {
	title = {Impact of Protocols on Traffic Burstiness At Large Timescales in Wireless Multi-Hop Networks},
	author = {Jain, Kaustubh., Baras, John S.},
	year = {2013},
	month = {06/2013},
	abstract = {We investigate the impact of the protocol stack on traffic burstiness at large time-scales in wireless multi-hop network traffic. Origins of traffic burstiness at large scales (like its LRD nature) have been mostly attributed to the heavy-tails in traffic sources. In wired networks, protocol dynamics have little impact on large time-scale dynamics. However, given the nature wireless networks, the MAC and routing layers together can lead to route flapping or oscillations even in a static network.Hence, we explore whether these dynamics can lead to trafficburstiness and LRD. Using network simulations, we analyze traffic for two MANET routing protocols - OLSR and AODV. By varying the routing protocol parameters, we analyze their role in inducing or preventing route oscillations, and study their impact on traffic LRD. We find that, losses in OLSR control packets, due to congestion at the MAC, can lead to route oscillations and trafficburstiness at large timescales. By tuning the parameters, route oscillations and traffic LRD can be avoided. AODV dynamics show little evidence for traffic LRD, even though we cannot rule out this possibility. We also show that the route oscillations can have heavier body and tail than exponential distribution, and that the Markovian framework for route oscillations is inadequate to explain the observed traffic scaling. Lastly, we give a model that captures the MAC and OLSR routing protocol interactions and depending upon chosen protocol parameters and input load,correctly predicts the presence of traffic LRD. Thus, we use this model to design appropriate choice of protocol parameters to mitigate traffic burstiness at large-timescales.},
	address = {Corsica, France},
	booktitle = {IEEE 2013 The 12th Annual Mediterranean Ad Hoc Networking Workshop (Med-Hoc-Net)},
	pages = {pp. 61-68},
	organization = {Ajaccio}
}
@conference {
	title = {Convergence Guarantees for a Decentralized Algorithm Achieving Pareto Optimality},
	author = {Menon, Anup., Baras, John S.},
	year = {2013},
	month = {06/2013},
	abstract = {We consider N agents, each picking actions froma finite set and receiving a payoff according to its individualutility function that may depend on the actions picked byothers. An agent has no knowledge about the functional formof its utility and can only measure its instantaneous value.It is assumed that all agents pick actions and receive payoffssynchronously. For this setting, a fully decentralized iterativealgorithm for achieving Pareto optimality i.e. picking actionsthat maximize the sum of all utilities was proposed by Mardenet. al. in [1] that lacks convergence guarantees. By schedulinga certain noise parameter to go to zero along iterations of thisalgorithm, conditions that guarantee convergence in probabilityare derived in this paper.},
	address = {Washington DC},
	booktitle = {2013 American Control Conference},
	pages = {pp. 1935-1940}
}
@conference {
	title = {Correlating Photovoltaic Clear-Sky and Actual Output to Sky Cover Measurements},
	author = {Daily, David R., Holmberg, David G., Baras, John S.},
	year = {2013},
	month = {06/2013},
	abstract = {As distributed energy resources are added to building systems, and variable priced electricity tariffs are introduced, facility owners may profit from understanding the expected performance of their building systems. Hourly, forecast energy generation data from photovoltaic sources allows owners to manage energy storage and consumption for their optimal benefit. This paper documents an empirical method which uses publicly{\textendash}available sky cover observations to estimate the output of a photovoltaic (PV) array. Two functions are developed which together relate PV array output to sky cover observations reported by the National Oceanic and Atmospheric Administration{\textquoteright}s National Weather Service (NWS) for a nearby airport. Results are evaluated by comparison of estimated PV array output with actual output. Results show this approach can produce useful estimates of hourly and daily PV system output which may be applied to forecast weather data in order to manage PV array outputs. Although some large deviations are observed between forecast and actual PV output, the method presented uses data that would be available to a building owner with insufficient on-site instrumentation beyond a meter.},
	address = {Tampa, Florida},
	booktitle = {To appear in the proceedings of 39th IEEE Photovoltaic Specialists Conference}
}
@conference {
	title = {A Fresh Look at Network Science: Coevolving Multigraphs, Multiple Semirings and Coalitional Games},
	author = {Baras, John S.},
	year = {2013},
	month = {06/2013},
	address = {Budapest, Hungary},
	booktitle = {Networking Across Disciplines: Communication Networks,  Complex Systems and Statistical Physics (NETSTAT)  workshop}
}
@conference {
	title = {{\textquotedblleft}Hardware{\textquotedblright} {\textendash} Software Security},
	author = {Baras, John S.},
	year = {2013},
	month = {06/2013},
	address = {San Francisco, CA},
	booktitle = {2013 INTEL University Collaboration Symposium}
}
@conference {
	title = {Fundamental Challenges in Modeling and Design Space Exploration for CPS},
	author = {Baras, John S.},
	year = {2013},
	month = {05/2013},
	address = {Austin, Texas},
	booktitle = {2nd International Workshop on Analytics for Cyber-Physical Systems (ACS-2013)}
}
@conference {
	title = {An Approach to Model-Based Systems Engineering with Applications to Army Ground and Air Vehicles, Single or Collaborating},
	author = {Baras, John S.},
	year = {2013},
	month = {04/2013},
	address = {Aberdeen Proving Grounds, Maryland},
	booktitle = {RDECOM}
}
@conference {
	title = {Security and Trust in a Networked Immersed World: From Components to Systems and Beyond},
	author = {Baras, John S.},
	year = {2013},
	month = {04/2013},
	abstract = {The tremendous explosion of wireless devices and services have created unprecedented advances and are impacting every aspect of life and work. However, many of these advances and resulting expanding markets are critically endangered by weaknesses in security, integrity, and trust. We first describe several of these emerging systems and markets in areas ranging from aerospace and automotive to healthcare and e-commerce to social networks over the Web. We then describe various physical layer (e.g. hardware and signal processing) techniques that can be successfully utilized to significantly strengthen the security of wireless devices and networked systems. We argue for the need of a {\textquotedblleft}trusted core{\textquotedblright} in wireless networks and for the allocation of part of the security functionality to the physical layer. We next turn to the subject of trust in large networks and describe a new framework using multiple partially ordered semirings for analyzing reputation and trust dynamics and composite trust. Next, we describe our work based on constrained coalitional games towards understanding the role of trust in collaboration and social networks. We describe several specific applications of these methods in securing distributed inference systems, SCADA sensor networks for power grids, wireless network routing protocols, LTE paging systems, wireless handheld devices for healthcare and e-payment systems. We close by describing the need for rigorous frameworks and theories for composable security and outline how these physical layer techniques can provide the foundation for such developments.},
	address = {College Park, MD},
	booktitle = {Laboratory for Telecommunication Sciences (LTS)}
}
@conference {
	title = {Model-Based Systems Enginnering Approach to Energy Efficient Building Design},
	author = {Daily, David R., Baras, John S.},
	year = {2013},
	month = {04/2013},
	abstract = {PROJECT

During my senior year at the University of Maryland, I was challenged to develop and investigate a research question utilizing Systems Engineering methodologies and tools for my capstone project. My project uses Model-Based Systems Engineering to model and simulate a residential building{\textquoteright}s HVAC operational effect and perform trade-off analysis on the building parameters. I have since continued this research for my Masters of Science in Systems Engineering thesis.

PURPOSE

According to the U.S. Energy Information Administration{\textquoteright}s (EIA) {\textquotedblleft}Annual Energy Outlook 2012{\textquotedblright}, the residential and commercial sectors use a combined 28 percent of total U.S. energy consumption. With energy efficiency technology improvements and policy change, the EIA estimates that building energy consumption could be reduced by 10\%-18.5\% within these sectors by 2035. Reducing building energy demand is a necessary step in curbing the greenhouse gas issue and creates new requirements to meet these goals. Model-Based System Engineering allows for easy requirements verification and validation while creating a truly optimized system.

METHODOLOGY

I used Systems Modeling Language (SysML) to develop a model of the building, its components, and other inputs into the system (i.e. weather). I am able to create a robust model in the SysML program MagicDraw, including detailed parametric, activity, and sequence diagrams, along with significant requirements definitions. I made a basic thermodynamics simulation in MATLAB and linked the two programs. With this link established, I automated the parametric analysis of the building parameters. The resulting 846 iterations gave me performance data to perform trade-off analysis to optimize cost and energy efficiency.

RESULTS

When the setpoint temperature of the building is outside the allowable range, the HVAC system uses energy to condition the space, while thermal losses and gains vary the indoor temperature. The efficiency metric is defined as the period length between the activation of the HVAC system. A longer period indicates a more energy efficient system. Through trade-off analysis, I conclude that the parameter of insulation R-Value had the greatest cost-to-efficiency benefit while window U-Value had the second most impact.},
	address = {La Crosse, WI},
	booktitle = {National Conference on Undergradute Research (NCUR) 2013}
}
@conference {
	title = {Storage-centric Sensor Networks for Smart Buildings},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {04/2013},
	abstract = {In my thesis, I propose a model-based systems design framework, called WSNDesign, to facilitate the design and implementation of wireless sensor networks (WSNs). WSNDesign provides a hierarchy of model libraries to model various behaviors and structures of WSNs in the context of Smart Buildings, and introduces a system design flow to compose both continuous-time and event-triggered modules to develop applications with support for performance evaluation. In order to handle various sensor data efficiently, WSNDesign provides a distributed database system, called HybridDB, for data collection and retrieval. HybridDB enables sensors to store large-scale datasets in situ on local NAND ash using a novel resource-aware data storage system, and can process typical queries inWSNs extremely efficiently. In addition, HybridDB supports incremental -approximate querying that enables clients to retrieve a just-sufficient set of sensor data by issuing refinement and zoom-in sub-queries to search events and analyze sensor data efficiently. HybridDB can always return an approximate dataset with guaranteed L1-norm error bound.},
	address = {Philadelphia, PA},
	booktitle = {12th ACM/IEEE Conference on Information Processing in Sensor Networks IPSN 2013}
}
@conference {
	title = {Compositional Analysis of Dynamic Bayesian Networks and Applications to Complex Dynamic System Decomposition},
	author = {Yang, Shahan., Zhou, Yuchen., Baras, John S.},
	year = {2013},
	month = {03/2013},
	abstract = {Dynamic Bayesian networks (DBNs) can be effectively used to model various problems in complex dynamic systems. We perform an empirical investigation on compositional analysis of DBNs using abstraction. In static systems and hidden Markov models, computation of a metric called treewidth induces a tree decomposition that can be used to perform logical or probabilistic inference and max + optimizations in time exponential in treewidth and linear in overall system size. Intuitively, the linear scaling means that very large systems can be analyzed as long as they are sufficiently sparse and well structured. In these simple cases, summary propagation, which uses two operations, summation (projection) and product (composition), suffices to perform the inference or optimization. Here, we begin an extension of this to structured networks of communicating dynamic systems. We define generalizations of projection and composition operators that treat labeled Markov chains as primitive objects. The projection operation, corresponding to summation, is implemented as label deletion followed by exact state reduction for Markov chains, similar to Hopcroft{\textquoteright}s DFA minimization algorithm, with O(n log m) complexity. The composition operation is the product of state machines. We use canonical MDDs, similar to BDDs, to capture logical dependencies symbolically. Combining symbolic representations with Markov chain lumping algorithms is a novel contribution. Using this approach, we have created a tool leveraging model based systems engineering technologies. The communicating Markov chains are specified using UML Statecharts via Papyrus extended using an ANTLR parsed domain specific language (DSL). The tool reduces the number of states in networks of Markov chains by several orders of magnitude. In one example, a network having a product state space of more than 600 million states is reduced to about 500 states. A feature of this technique is that the state space is examined incrementally, meaning that the full state space is never explicitly represented, even as an input to the reduction algorithm. The primary reduction appears to come from symmetry which is surprising because the technique includes no explicit symmetry handling. We note that composition is efficient at least for systems with high symmetry. We describe applications to a hospital intensive care unit (ICU) from a systems engineering perspective.},
	address = {Atlanta, GA},
	booktitle = {Conference on Systems Engineering Research (CSER{\textquoteright}13),},
	pages = {pp. 167-176}
}
@conference {
	title = {Interactive Tree Decomposition Tool for Reducing System Analysis Complexity},
	author = {Yang, Shahan., Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {03/2013},
	abstract = {We present a graphical tool for the calculation of treewidth, a metric on the parametric structure of a system that is intimately tied to the complexity of system analysis. For many graphically describable systems, such as systems of parametric equations, as in a SysML Parametric diagram, or Bayesian networks or even mind maps and writing term papers, analysis of the system is exponential in treewidth and linear in system size. A tool facilitating comprehensive analysis can serve to bring competitive advantage to a systems engineering workflow by reducing costly unanticipated behaviors. Furthermore, a byproduct of computing treewidth is a framework for enumerating computationally compatible distributed algorithms. In this paper, we pose this NP-complete problem from the perspective of finding satisficing solutions, exposing choices that can influence the complexity of the resulting system to the designer. A designer can contribute two important things to the structure of the system: a visual intuition about the relationships between the underlying objects and the ability to change the relationships themselves at design time to reduce analysis complexity. Having a visual tool that provides instant feedback will help designers achieve an intuitive grasp of the relationship between design decisions and system complexity. As complexity is the root of almost every systems engineering problem, and also something not easily understood, incorporating complexity analysis into a design process should improve resulting system designs. The tool uses a randomized, anytime algorithm for interactive optimization of treewidth. It presents a sequence of choices to a designer and incrementally lowers an upper bound on system treewidth over time. This algorithm is novel, as few algorithms are targeted at interactivity with a human user. We present a number of simple examples for using the tool. We show how our tool helps to decompose some example systems, including a quadrotor optimization, a sensor network optimization, a Bayesian network, and a mind map.},
	address = {Atlanta, GA},
	booktitle = {Conference on Systems Engineering Research (CSER{\textquoteright}13),},
	pages = {pp. 138-147}
}
@conference {
	title = {Extending Design Capabilities of SysML with Trade-off Analysis: Electrical Microgrid Case Study},
	author = {Spyropoulos, Dimitrios., Baras, John S.},
	year = {2013},
	month = {03/2013},
	abstract = {Changes in technology, economy and society create challenges that force us to rethink the way we develop systems. Model- Based Systems Engineering is an approach that can prove catalytic in this new era of systems development. In this paper we introduce the idea of the {\textquotedblleft}modeling hub{\textquotedblright} in order to realize the vision of Model-Based Systems Engineering and especially we focus on the trade-off path of this hub. For that purpose the design capabilities of SysML are extended by integrating it with Consol-Optcad, a powerful multi-criteria optimization tool for trade-off analysis. The integration and its implementation is applied to analyze a multi-criteria optimization problem concerning power allocation and scheduling in a microgrid.},
	address = {Atlanta, GA},
	booktitle = {Conference on Systems Engineering Research (CSER{\textquoteright}13),},
	pages = {pp. 108-117}
}
@conference {
	title = {Studying the role of Apoe in Alzheimer{\textquoteright}s disease pathogenesis using a systems biology model},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2013},
	month = {03/2013},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is the most common form of dementia. Even with its well-known symptoms of memory loss and well-characterized pathology of beta amyloid (A) plaques and neurofibrillary tangles, the disease pathogenesis and initiating factors are still not well understood. To tackle this problem, a systems biology model has been developed and used to study the varying effects of variations in the ApoE allele present, as well as the effects of short term and periodic inflammation at low to moderate levels. Simulations showed a late onset peak of A in the ApoE4 case that lead to localized neuron loss which could be ameliorated in part by application of short-term pro-inflammatory mediators. The model that has been developed herein represents one of the first attempts to model AD from a systems approach to study physiologically relevant parameters that may prove useful to physicians in the future.},
	address = {Honolulu, Hawaii},
	booktitle = {5th International Conference on Bioinformatics and Computational Biology (BICoB)},
	pages = {pp. 1342003-1 -1342003-21}
}
@conference {
	title = {HybridStore: An Efficient DataManagement System for Hybrid Flash-based Sensor Devices},
	author = {Wang, Baobing., Baras, John S.},
	year = {2013},
	month = {02/2013},
	abstract = {In this paper, we propose HybridStore, a novel efficient resourceaware data management system for flash-based sensor devices to store and query sensor data streams. HybridStore has three key features. Firstly, it takes advantage of the on-board random-accessible NOR flash in current sensor platforms to guarantee that all NAND pages used by it are fully occupied and written in a purely sequential fashion, and expensive in-place updates and out-of-place writes to an existing NAND page are completely avoided. Thus, both raw NAND flash chips and FTL-equipped (Flash Translation Layer) flash packages can be supported efficiently. Secondly, HybridStore can process typical joint queries involving both time windows and key value ranges as selection predicate extremely efficiently, even on large-scale datasets. It organizes a data stream into segments and exploits a novel index structure that consists of the inter-segment skip list, and the in-segment β-Tree and Bloom filter of each segment. Finally, HybridStore can trivially support time-based data aging without any extra overhead because no garbage collection mechanism is needed. Our implementation and evaluation with a large-scale real-world dataset in TinyOS reveals that HybridStore can achieve remarkable performance at a small cost of constructing the index.},
	address = {Ghent, Belgium},
	booktitle = {10th European Conference on Wireless Sensor Networks},
	pages = {pp. 50-66}
}
@conference {
	title = {Security and Trust in a Networked Immersed World: from Components to Systems and Beyond},
	author = {Baras, John S.},
	year = {2013},
	month = {01/2013},
	address = {Stockholm, Sweden},
	booktitle = {3rd ACCESS Industry Workshop},
	organization = {KTH, Royal Institute of Technology}
}
@conference {
	title = {Hyperbolic Embedding to the Rescue in Communication Networks Control},
	author = {Baras, John S.},
	year = {2013},
	month = {01/2013},
	address = {Lund, Sweden},
	organization = {Lund University}
}
@conference {
	title = {Reachability Analysis for Linear Discrete Time Set{\textendash}Dynamics Driven by Random Convex Compact Sets},
	author = {Rakovic, Sasa V., Matei, Ion., Baras, John S.},
	year = {2012},
	month = {12/2012},
	abstract = {This paper studies linear set{\textendash}dynamics driven by random convex compact sets (RCCSs), and derives the set{\textendash}dynamics of the expectations of the associated reach sets as well as the dynamics of the corresponding covariance functions. It is established that the expectations of the reach sets evolve according to deterministic linear set{\textendash}dynamics while the associated dynamics of covariance functions evolves on the Banach space of continuous functions on the dual unit ball. The general framework is specialized to the case of Gaussian RCCSs, and it is shown that the Gaussian structure of random sets is preserved under linear set{\textendash}dynamics of random sets.},
	address = {Maui, Hawaii},
	booktitle = {51st IEEE Conference on Decision and Control},
	pages = {pp. 4751-4756}
}
@conference {
	title = {A Randomized Gossip Consensus Algorithm on Convex Metric Spaces},
	author = {Matei, Ion., Somarakis, Christoforos., Baras, John S.},
	year = {2012},
	month = {12/2012},
	abstract = {A consensus problem consists of a group of dynamic agents who seek to agree upon certain quantities of interest. This problem can be generalized in the context of convex metric spaces that extend the standard notion of convexity. In this paper we introduce and analyze a randomized gossip algorithm for solving the generalized consensus problem on convex metric spaces. We study the convergence properties of the algorithm using stochastic differential equations theory. We show that the dynamics of the distances between the states of the agents can be upper bounded by the dynamics of a stochastic differential equation driven by Poisson counters. In addition, we introduce instances of the generalized consensus algorithm for several examples of convex metric spaces.},
	address = {Maui, Hawaii},
	booktitle = {51st IEEE Conference on Decision and Control,},
	pages = {pp. 7425-7430}
}
@conference {
	title = {Social Networks over Wireless Networks},
	author = {Stai, Eleni., Baras, John S., Papavassiliou, Symeon.},
	year = {2012},
	month = {12/2012},
	abstract = {We consider the formation, operation and maintenance of dynamic social networks (among human users) supported by technological communication networks such as wireless networks, or hybrid wireline-wireless networks. The technological (physical) networks of interest display dynamic behavior in several dimensions, including variable connectivity, variable congestion, variable link characteristics. As broadband wireless devices and networks are becoming ubiquitous these human-machine systems, that combine the social aspects and behavioral activities of humans with the technological characteristics of the underlying physical networks, provide several important challenges in efforts to model them, evaluate their performance and dynamically control them so certain performance requirements are met. These include combinations of performance, trust, privacy, energy efficiency. In this paper we develop novel models for these complex human-machine systems that incorporate social network behavioral models and wireless network models that are inspired from statistical physics (hyperbolic graphs). We investigate the performance of wireless network protocols that support and respond to the constraints implied by the social network they support.},
	address = {Maui, Hawaii},
	booktitle = {51st IEEE Conference on Decision and Control},
	pages = {pp. 2696-2703}
}
@conference {
	title = {A Distributed Opportunistic Scheduling Protocol for Multi-Channel Wireless Ad-Hoc Networks},
	author = {Chen, Hua., Baras, John S.},
	year = {2012},
	month = {12/2012},
	abstract = {The topic of opportunistic scheduling for wireless ad-hoc networks has been studied for single-channel networks in several recent works. Since now many wireless systems provide multiple channels for data transmission, this problem is of practical interest for networks with multiple channels. In this paper, we study the problem of opportunistic scheduling for one type of ad-hoc networks where the wireless spectrum can be divided into multiple independent sub-channels for better efficiency. We start with a naive multi-channel protocol where the scheduling scheme is working independently from sub-channel to sub-channel.We show that the naive protocol can only marginally improve the system throughput. We then develop a protocol to jointly consider the opportunistic scheduling behavior across multiple sub-channels. We characterize the optimal stopping rule and present several bounds for the system throughput of the multi-channel protocol. We show that by joint optimization of the scheduling scheme across multiple sub-channels, the proposed protocol improves the system throughput considerably in contrast to that of single-channel systems.},
	address = {Anaheim, California},
	booktitle = {IEEE Globecom 2012},
	pages = {pp. 292-297}
}
@conference {
	title = {A Graph Theoretic Mathematical Model for Alzheimer{\textquoteright}s Disease},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2012},
	month = {11/2012},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is currently the most common form of dementia affecting the elderly, and its occurrence rate is only expected to increase over the next several decades. Though there is a vast array of knowledge about individual molecules and genetics involved with the disease, there is no clear understanding of the mechanism of pathogenesis. To help better understand the disease process, a graph theoretic model was developed that studies both the concentration of molecules thought to be involved in pathogenesis (Aβ, interleukin1, tumor necrosis factor alpha, cholesterol, ATP levels), as well as the cell number in a small location in the brain. Particular emphasis was put on the role of the inflammatory process in AD progression. This represents one of the first models that uses graph theory combined with a systems biology approach to study AD.},
	address = {Larnaca, Cyprus},
	booktitle = {12th IEEE International Conference on BioInformatics and BioEngineering},
	pages = {pp. 472-477}
}
@conference {
	title = {Minimizing Aggregation Latency under the Physical Interference Model in Wireless Sensor Networks},
	author = {Wang, Baobing., Baras, John S.},
	year = {2012},
	month = {11/2012},
	abstract = {Wireless Sensor Networks (WSNs) have been widely~recognized as a promising technology that can enhance various~aspects of today{\textquoteright}s electric power systems, making them a vital~component of the smart grid. Efficient aggregation of data~collected by sensors is crucial for a successful WSN-based smart~grid application. Existing works on the Minimum Latency Aggregation~Scheduling (MLAS) problem in WSNs usually adopt the~protocol interference model, which is a tremendous simplification~of the physical reality faced in wireless networks. In contrast,~the more realistic physical interference model has been proved~to have the potential to increase the network capacity. In this~paper, we propose a distributed algorithm to minimize the data~aggregation latency under the physical interference model, which~jointly considers routing, power assignment and transmission~scheduling.~},
	address = {Tainan City , Taiwan},
	booktitle = {Third International Conference on Smart Grid Communications (IEEE SmartGridComm 2012)},
	pages = {pp. 19-24}
}
@conference {
	title = {A Formal Framework for Joint Privacy and Security Modeling and Analysis in Data and Communication Networks},
	author = {Baras, John S.},
	year = {2012},
	month = {11/2012},
	abstract = {We develop a formal framework to model and analyze combined security and privacy requirements in data and communication networks. The network is modeled by two interacting multigraphs: one representing the logical (social, organizational) relationships between nodes (users, servers), and a second one representing the physical interconnections between nodes. Nodes and links in both multigraphs are annotated by weights (numerical, logical, rules) that represent security and privacy requirements. Our recent theory of multiple semiring optimization and tradeoff analysis in networks forms the foundation. Automatic theorem proving and satisfiability methodologies are also employed. Extensions to dynamic networks, privacy and security, are described.},
	address = {Pacific Grove, CA},
	booktitle = {46th Asilomar Conference on Signals, Systems and Computers}
}
@conference {
	title = {Model-Based Systems Enginnering Approach to Energy Efficient Building Design},
	author = {Daily, David R.},
	year = {2012},
	month = {11/2012},
	abstract = {Project

During my senior year at the University of Maryland, I was challenged to develop and investigate a research question utilizing Systems Engineering methodologies and tools for my capstone project.~ My project uses Model-Based Systems Engineering to model and simulate a residential building{\textquoteright}s HVAC operational effect and perform trade-off analysis on the building parameters.~ I have since continued this research for my Masters of Science in Systems Engineering thesis.

Purpose

According to the U.S. Energy Information Administration{\textquoteright}s {\textquotedblleft}Annual Energy Outlook 2012{\textquotedblright}, the residential and commercial sectors use a combined 28 percent of total U.S. energy consumption.~ With energy efficiency technology improvements and policy change, the EIA estimates that building energy consumption could be reduced by 10\%-18.5\% within these sectors by 2035.~ Reducing building energy demand is a necessary step in curbing the GHG issue and creates new requirements to meet these goals.~ Model-Based System Engineering allows for easy requirements verification and validation while creating a truly optimized system.

Methodology

I used SysML to develop a model of the building, its components, and other inputs into the system (i.e. weather).~ I am able to create a robust model in the SysML program MagicDraw, including detailed parametric, activity, and sequence diagrams, along with significant requirements definitions.~ I made a basic thermodynamics simulation in MATLAB and linked the two programs.~ With this link established, I automated the parametric analysis of the building parameters.~ The resulting 846 iterations gave me performance data to perform trade-off analysis to optimize cost and energy efficiency.

Results

When the setpoint temperature of the building is outside the allowable range, the HVAC system uses energy to condition the space, while thermal losses and gains vary the indoor temperature.~ The efficiency metric is defined as the period length between the activations of the HVAC system.~ A longer period indicates a more energy efficient system. Through trade-off analysis, I conclude that the parameter of insulation R-Value had the greatest cost-to-efficiency benefit while window U-Value had the second most impact.},
	address = {Toms River, New Jersey},
	booktitle = {The 2012 Mid-Atlantic Section Conference of the American Society for Engineering Education}
}
@conference {
	title = {A Class of Backpressure Algorithms for Networks Embedded in Hyperbolic Space with Controllable Delay-Throughput Trade-off},
	author = {Stai, Eleni., Baras, John S., Papavassiliou, Symeon.},
	year = {2012},
	month = {10/2012},
	abstract = {Future communications consist of an increasing number of wireless parts, while simultaneously need to support the widespread multimedia applications imposed by social networks. These human-machine systems, driven by both real time social interactions and the challenges of the wireless networks~design, call for efficient and easy to implement, distributed cross-layer algorithms for their operation. Performance metrics such as throughput, delay, trust, energy consumption, need to be improved and optimized aiming at high quality communications. We investigate the coveted throughput-delay trade-off in static wireless multihop net- works based on a {\textquotedblleft}computer-aided{\textquotedblright} design of the backpressure scheduling/routing algorithm for networks embedded in hyperbolic space. Both routing and scheduling exploit the hyperbolic distances to orient the packets to the destination and prioritize the transmissions correspondingly. The proposed design provides us with the freedom of controlling its theoretical throughput optimality and of counterbalancing its practical performance through simulations, leading to significant improvements of the throughput-delay trade-off.},
	address = {Paphos, Cyprus Island},
	booktitle = {15th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2012), pp. no. 15-22, Paphos, Cyprus Island},
	pages = {pp. 15-22}
}
@conference {
	title = {A Rigorous Framework for Model-based Systems Engineering and Applications},
	author = {Baras, John S.},
	year = {2012},
	month = {10/2012},
	address = {Laurel, MD},
	booktitle = {INCOSE Chesapeake Bay Chapter},
	organization = {Applied Physics Laboratory, Johns Hopkins University}
}
@conference {
	title = {Jubilee Panel 1: The Ecology of Communication,Control and Computing Research and Education},
	author = {Baras, John S.},
	year = {2012},
	month = {10/2012},
	booktitle = {50th Annual Allerton Conference on Communication, Control and Computing}
}
@conference {
	title = {Components, Compositionality and Architectures for Networked CPS},
	author = {Baras, John S.},
	year = {2012},
	month = {10/2012},
	address = {London, UK},
	booktitle = {London CPS Workshop}
}
@conference {
	title = {Performance Evaluation of Hybrid SAMA VSAT with FMCSA and Reservations},
	author = {Perumal, Senni., Baras, John S.},
	year = {2012},
	month = {09/2012},
	abstract = {In this paper, we describe our work on developing and evaluating detailed OPNET simulation models of an enhanced Very Small Aperture Terminal (VSAT) satellite Internet gateway and an enhanced satellite hub based on Cerona SkySPAN technology with capacity and latency optimizations in a hybrid random access and reservation based return channel so as to allow significantly higher number of users and a better user experience. The Cerona SkySPAN technology uses Digital Video Broadcast via Satellite 2nd standard (DVB-S2) in the forward channel and Spread Aloha Multiple Access (SAMA) protocol in the return channel. We augment the SAMA return channel protocol with a hybrid random access and reservation based Dynamic Channel Allocation (DCA) scheme. The overall goal of the DCA algorithm is to make the system behave like a random access system at low loads for small messages so as to provide low message delay and to behave like a MF-TDMA reservation based system at high loads as well as for real time traffic so as to provide high maximum throughput and a better user experience. The random access protocol used at low loads is SAMA enhanced with Fast Multi-channel Slotted Aloha (FMCSA) protocol. FMCSA combines Multi-Channel Slotted Aloha (MCSA) with packet level forward error correction for new messages and scheduled retransmissions for partially received messages. This protocol increases the maximum possible throughput of SAMA and reduces the delay of multi-slot short messages while providing more robust delay performance with respect to load fluctuations, thus resulting in a much better user experience at low loads. The system transitions into a reservation based system at higher loads and for real time traffic so to support higher maximum throughput and achieve good QoS for real time traffic. The satellite return channel is divided into multi-frequency periodic frames. Each frame has mini-slots used for sending reservation requests in contention mode and larger data-slots used for sending data in either contention mode (FMCSA) or reservation mode (where the HUB allocates data-slots based on requests). We show via OPNET simulations that the enhanced SAMA VSAT with the hybrid DCA algorithm improves the throughput, latency and robustness of the SkySPAN SAMA system. We also compare, via OPNET simulations, the enhanced system with a DVB-RCS system to show the improvements in user experience both in terms of delay and throughput.},
	address = {Ottawa, Canada},
	booktitle = {18th Ka and Broadband Communications, Navigation and Earth Observation Conference}
}
@conference {
	title = {A comparison between upper bounds on performance of two consensus-based distributed optimization algorithms},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {09/2012},
	abstract = {In this paper we address the problem of multi-agent optimization for convex functions expressible as sums of convex functions. Each agent has access to only one function in the sum and can use only local information to update its current estimate of the optimal solution. We consider two consensus-based iterative algorithms, based on a combination between a consensus step and a subgradient decent update. The main difference between the two algorithms is the order in which the consensus-step and the subgradient descent update are performed. We obtain upper bounds on performance metrics of the two algorithms. We show that updating first the current estimate in the direction of a subgradient and then executing the consensus step ensures a tighter upper bound compared with the case where the steps are executed in reversed order. In support of our analytical results, we give some numerical simulations of the algorithms as well.},
	address = {Santa Barbara, CA},
	booktitle = {3rd IFAC Workshop on Distributed Estimation and Control in Networked Systems(NecSys 2012), pp. 168-173, Santa Barbara, California},
	pages = {pp. 168-173}
}
@conference {
	title = {Expander Families as Information Patterns for Distributed Control of Vehicle Platoons},
	author = {Menon, Anup., Baras, John S.},
	year = {2012},
	month = {09/2012},
	abstract = {A state space formulation of the distributed control of a 1-D vehicle platoon is considered. The objective is to understand the effects of the underlying information exchange pattern between the vehicles on the control performance of the platoon. The symmetric control case is considered where each vehicle gives equal weight to all the information available to it in determining its control law. It is shown that expander families of graphs when used as information patterns result in stability margins decaying to zero at rate at most O(1/N); an improvement over the previously known O(1/N^2) decay with nearest neighbor type information patterns.},
	address = {Santa Barbara, CA},
	booktitle = {3rd IFAC Workshop on Distributed Estimation and Control in Networked Systems(NecSys 2012), pp. 288-293, Santa Barbara, California},
	pages = {pp. 288-293}
}
@conference {
	title = {Enhancing Privacy in LTE Paging System using Physical Layer Identification},
	author = {Ta, Tuan., Baras, John S.},
	year = {2012},
	month = {09/2012},
	abstract = {User location privacy is a growing concern in cellular networks.~It has been recently shown that the paging architecture in GSM~networks leaks user location information. In this paper, we first prove~theoretically that LTE networks also have the same vulnerability. We~then propose a solution making use of a novel signal processing technique,~physical layer identification. The idea is to embed users{\textquoteright} unique~tags onto the downlink paging signal waveforms so that the tags are ~stealthy and robust. We show that our scheme not only improves users{\textquoteright}~privacy, but also saves system bandwidth.},
	address = {Pisa, Italy},
	booktitle = {Proceedings of the Data Privacy Management 7th International Workshop co-located with ESORICS 2012},
	pages = {pp. no. 15-28}
}
@conference {
	title = {Inflammation and Cholesterol: Friend Or Foe in Alzheimer{\textquoteright}s Disease},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2012},
	month = {08/2012},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is the most common form of dementia affecting the elderly, leading to debilitating memory loss and significant cognitive decline. The exact mechanism of pathogenesis is not well understood. Here, we present an organ level model that studies the role of cholesterol metabolism and inflammation in the early stages of AD, demonstrating the importance of brain cholesterol on the expression of beta amyloid. The model has been further validated with experimental data.},
	address = {San Diego, California},
	booktitle = {SIAM Conference on the Life Sciences 2012}
}
@conference {
	title = {The Consensus Problem Under Vanishing Communication Weights},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2012},
	month = {07/2012},
	abstract = {We revisit the classical multi-agent distributed consensus problem under the dropping of the assumption that the existence of a connection between agent implies weights uniformly bounded away from zero. We formulate and study the problem by establishing global convergence results in discrete time, under fixed, switching and random topologies. We study the application of the results to flocking networks.},
	address = {Melbourne, Australia},
	booktitle = {20th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2012)},
	pages = {pp. 1-8}
}
@conference {
	title = {Flow Control in Time-Varying, Random Supply Chain Networks},
	author = {Matei, Ion., Gueye, Assane., Baras, John S.},
	year = {2012},
	month = {07/2012},
	abstract = {Todays supply chains are more and more complex. They depend on a network of independent, yet interconnected moving parts. They rely on critical infrastructures and experience a lot of time variability and randomness.Designing strategies that deal with such constantly changing supply chains is necessary in this increasingly globalized economy where supply chain disruptions have impacts that propagate not only locally but also globally.In this paper we propose a randomized flow control algorithm for a time varying, random supply chain network. We formulate a constrained stochastic optimization problem that maximizes the profit function in terms of the long-run,time-average rates of the flows in the supply chain. We show that our algorithm, which is based on queueing theory and stochastic analysis concepts, can get arbitrarily close to the solution of the aforementioned optimization problem.},
	address = {Melbourne, Australia},
	booktitle = {20th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2012)},
	pages = {pp. 1-4}
}
@conference {
	title = {Throughput-Delay Trade-off in Wireless Multi-hop Networks via Greedy Hyperbolic Embedding},
	author = {Stai, Eleni., Baras, John S., Papavassiliou, Symeon.},
	year = {2012},
	month = {07/2012},
	abstract = {Real time applications over wireless multihop networks, demand routing/scheduling algorithms that achieve desirable delay-throughput trade-offs, with high throughput and low end-to-end delay. The backpressure algorithm, has received much attention by the research community in the past few years, as it satisfies the throughput optimal requirement. The backpressure algorithm performs routing and scheduling based on congestion gradients, by allowing transmission to the links that maximize the differential backlog between neighboring nodes. However, by deploying routing without using any information about the position or distance to the destination, it explores all possible source-destination paths leading to undesirable high delays. In this paper, we propose a method of restricting the number of paths used by the backpressure algorithm, with the aid of the greedy embedding of a network in the hyperbolic space. We propose two algorithms, the {\textquotedblleft}Greedy{\textquotedblright} backpressure and the {\textquotedblleft}Greediest{\textquotedblright} backpressure for both static and dynamic networks, which consider the network embedded in the hyperbolic space and combine the greedy routing in hyperbolic coordinates with the backpressure scheduling. We prove analytically their throughput optimality and study through simulations the induced improvement in the delay-throughput trade-off compared with the backpressure algorithm.},
	address = {Melbourne, Australia},
	booktitle = {20th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2012)},
	pages = {pp. 1-8}
}
@conference {
	title = {Trust-Based Multi-Agent Filtering for Increased Smart Grid Security},
	author = {Matei, Ion., Baras, John S., Srinivasan, Vijay.},
	year = {2012},
	month = {07/2012},
	abstract = {We address the problem of state estimation of the power system for the Smart Grid. We assume that the monitoring of the electrical grid is done by a network of agents with both computing and communication capabilities. We propose a security mechanism aimed at protecting the state estimation process against false data injections originating from faulty equipment or cyber-attacks. Our approach is based on a multi-agent filtering scheme, where in addition to taking measurements, the agents are also computing local estimates based on their own measurements and on the estimates of the neighboring agents. We combine the multi-agent filtering scheme with a trust-based mechanism under which each agent associates a trust metric to each of its neighbors. These trust metrics are taken into account in the filtering scheme so that information transmitted from agents with low trust is disregarded. In addition, a mechanism for the trust metric update is also introduced, which ensures that agents that diverge considerably from their expected behavior have their trust values lowered.},
	address = {Barcelona, Spain},
	booktitle = {Proceedings of the 2012 Mediterranean Control Conference},
	pages = {pp. 716-721}
}
@conference {
	title = {Composite Trust in Networked Multi-Agent Systems},
	author = {Baras, John S., Jiang, Tao.},
	year = {2012},
	month = {06/2012},
	abstract = {Trust plays a crucial role in the analysis, synthesis and operation of the integrated system consisting of social-cognitive, information and communication networks. Multi-agent systems and associated coalition operations, which involve two or more organizations, further augment the diversity and complexity of network interactions. Trust and its derivative notions affect dramatically the networked coalition operations. A substantial part of the research challenge has to do with the multitude of meanings, interpretations, symbolisms and mathematical models used to represent and analyze trust. In this paper, we introduce value directed graphs with weighted nodes as our model for composite trust. We extend the value directed graph with weighted nodes composite trust model to include not only numerical weights, but also constraints. We show that the semiring-based constraint satisfaction problem (SCSPs) framework can serve as the unified model to investigate trust relation establishment.},
	address = {Montreal, Canada},
	booktitle = {2012 American Control Conference (ACC 2012),},
	pages = {pp. 3547-3552}
}
@conference {
	title = {Increasing Message Relevance in Social Networks via Context-based Routing},
	author = {Pouli, Vasiliki., Baras, John S., Arvanitis, Anastasios.},
	year = {2012},
	month = {06/2012},
	abstract = {Several applications are built around sharing information by leveraging social network connections. For example, in social buying sites like Groupon, a deal is usually forwarded to interested recipients through their social graph. A primary goal is to improve user satisfaction by maximizing the relevance of the shared message to the target audience. In this work, we address this problem by proposing a context- based routing approach that exploits both user preferences and the network structure aiming at enhancing the relevance of forwarded messages and ensuring that each message will be delivered to the most interested users.},
	address = {Milwaukee USA},
	booktitle = {3rd International Workshop on Modeling Social Media: Collective Intelligence in Social Media (MSM 2012)},
	pages = {pp. 21-24}
}
@conference {
	title = {Integrated Modeling and Simulation Framework for Wireless Sensor Networks},
	author = {Wang, Baobing., Baras, John S.},
	year = {2012},
	month = {06/2012},
	abstract = {Existing ad hoc system design methods for Wireless Sensor Networks (WSNs) suffer from lack of reusability. In addition, the interactions between the continuous-time physical environments and WSNs have not been well studied. In this paper, we propose a model-based systems design (MBSD) framework for WSNs, which is a systematic methodology applying systems engineering principles to enhance model reusability and collaborations among multiple modeling domains. Firstly, we describe a hierarchy of model libraries to model various behaviors and structures of WSNs, including physical environments, physical platforms, communication and computation components, system services and applications. Based on the MBSD framework, we introduce a system design flow to compose both continuoustime and event-triggered modules to develop applications with support for performance study by simulations. Next, we briefly describe the main modules for physical platforms, the Media Access Control (MAC) layer, wireless channels and physical environments, which are developed using the Systems Modeling Language (SysML), Simulink and Modelica. Finally, we use a building thermal control system as the case study to demonstrate the composability, reusability and flexibility of the proposed MBSD framework.},
	address = {Toulouse, France},
	booktitle = {21st IEEE International Conference on Collaboration Technologies and Infrastructures (WETICE 2012- CoMetS track)},
	pages = {pp. 268-273}
}
@conference {
	title = {Wormhole Detection Using Channel Characteristics},
	author = {Jain, Shalabh., Ta, Tuan., Baras, John S.},
	year = {2012},
	month = {06/2012},
	abstract = {The potential applications and pervasive nature of mobile ad-hoc networks (MANETs) has made them an attractive target for attackers. The wireless medium of communication coupled with constrained resources enable attacks which can be executed by a weak adversary. A wormhole is one such attack which poses considerable threat, particularly to routing protocols. In this paper, we devise a novel scheme for detecting a wormhole by utilizing the inherent symmetry of electromagnetic wave propagation in the wireless medium. We demonstrate the loss of this symmetry in case of a wormhole attack and propose a method to detect and flag the adversary. We modify the insecure neighborhood discovery to incorporate authentication. We further extend this scheme to a trust system with low overhead.},
	address = {Ottawa, Canada},
	booktitle = {First IEEE International Workshop on Security and Forensics in Communication Systems (SFCS 2012)},
	pages = {pp. 6699-6704}
}
@conference {
	title = {Complex Network Problems via Greedy Hyperbolic Embedding},
	author = {Baras, John S.},
	year = {2012},
	month = {06/2012},
	address = {Gaithersburg, Maryland},
	booktitle = {2nd NIST-Bell Labs Workshop on Large Complex Networks},
	organization = {NIST}
}
@conference {
	title = {Cooperative Multi-agent Systems and {\textquotedblleft}Magical{\textquotedblright} Graphs},
	author = {Baras, John S.},
	year = {2012},
	month = {05/2012},
	address = {Gothenborg, Sweden},
	organization = {Signal and Systems Department, Chalmers University}
}
@conference {
	title = {Preventing Wormhole Attacks using Physical Layer Authentication},
	author = {Jain, Shalabh., Baras, John S.},
	year = {2012},
	month = {04/2012},
	abstract = {Mobile ad-hoc networks (MANETs) are a key enabler of pervasive computing. Constrained resources in mobile stations make it critical for nodes to be able to cooperate to enhance communication and computation capabilities. However, the wireless and dynamic nature of the links presents easy attack vectors for adversaries. The ability to securely discover and identify neighboring nodes (secure ND) is a fundamental building block for such networks. Even a relatively weak adversarial relay has the capability of distorting the network view and diverting significant amount of traffic. This can cause significant performance degradation. In this paper, we utilize the physical layer authentication scheme introduced by Yu, Baras and Sadler [1] to secure neighborhood discovery against adversarial relays. The proposed method incurs little performance overhead and requires no additional hardware. We provide analytical and simulation based performance evaluation of the security of our scheme.},
	address = {Paris, France},
	booktitle = {2012 IEEE Wireless Communications and Networking Conference (WCNC 2012)},
	pages = {pp. 2739-2744}
}
@conference {
	title = {Understanding Alzheimer{\textquoteright}s disease with Network Biology},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2012},
	month = {03/2012},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is a complex disease showing dysregulation of several key pathways and an abnormal increase in levels of beta amyloid (Aβ) and hyperphosphorylated tau. Although AD is the most common type of memory loss among the elderly, its pathogenesis is not well understood. Mathematical modeling offers a unique opportunity to gain a better understanding of the AD disease process by combining the current knowledge within a quantitative framework. Using a network model for AD, we discuss how the transition from a normal, healthy brain to an AD brain network can be modeled using a Markov model.},
	address = {Philadelphia, PA},
	booktitle = {The 2012 Northeast Bioengineering Conference (NEBEC 2012)},
	pages = {pp. 67-68},
	organization = {Temple University}
}
@conference {
	title = {Deal Sites{\textquoteright} Characteristics},
	author = {Pouli, Vasiliki., Baras, John S.},
	year = {2012},
	month = {03/2012},
	abstract = {Deal sites like Groupon (www.groupon.com) , Travelzoo (www.travelzoo.com ), LivingSocial (www.livingsocial.com ) and others are social network sites that offer daily deals to users for discounted prices. The daily deals consist of trips, restaurants, gifts, theaters, and many others, in various countries across the world. Users by buying a deal create a link with the seller and follow him. Users can also refer friends and earn money. Groupon is the number one daily deal site and as of January 2011 it has more than 50 million subscribers, it has sold more than 22 million Groupon deals in North America and has saved in this way more than $980 millions only in North America. Our target is to examine deal sites with millions of users such as Groupon and compute various statistics. More specifically in this project we want to gather data from the Groupon deal site and compute statistical results like: what kind of deals are mostly sold out (e.g. trips, gifts, food?) and in which areas across USA and Canada. Also we want to find out the range of prices per category of deals that is more attractive to the users. One other thing of interest is the seasons (time periods) that most deals are sold out (for example Christmas, Valentines day etc). Last but not least, it is also worth seeing which companies offer more than one deals, which company had the most deals and in which category.The Groupon site gives you an API to request: deals for specific categories, information about the deals, how many deals were sold out, in which area, by which company etc. By the use of this API we can gather information on the deals and then via the use of Hadoop (http://hadoop.apache.org/ ) we can process all this information to compute the statistical results mentioned above and infer useful conclusions. The outcomes of this project can be useful for further improvements; development or extensions to these kinds of deal sites that can make both buyers and sellers even more satisfied and save people from lots of money.},
	address = {Redondo Beach, CA},
	booktitle = {The Social Network Big Data Hackathon at the INSNA Sunbelt Conference},
	pages = {pp. no. 2712-2717},
	organization = {Crowne Plaza Hotel}
}
@conference {
	title = {COMPASS: Component-based Architectures for Systems Synthesis},
	author = {Baras, John S.},
	year = {2012},
	month = {02/2012},
	address = {Link{\"o}ping, Sweden},
	booktitle = {MODPROD Conference},
	organization = {Link{\"o}ping University}
}
@conference {
	title = {Cooperative Swarms},
	author = {Baras, John S.},
	year = {2012},
	month = {01/2012},
	address = {Champaign, IL},
	booktitle = {7th Annual Coordinated Sciences Laboratory Student Conference},
	organization = {University of Illinois Urbana-Champaign}
}
@conference {
	title = {Multi-scale Analysis of Long Range Dependent Traffic for Anomaly Detection in Wireless Sensor Networks},
	author = {Zheng, Shanshan., Baras, John S.},
	year = {2011},
	month = {12/2011},
	abstract = {Anomaly detection is important for the correct functioning of wireless sensor networks. Recent studies have shown that node mobility along with spatial correlation of the monitored phenomenon in sensor networks can lead to observation data that have long range dependency, which could significantly increase the difficulty of anomaly detection. In this paper, we develop an anomaly detection scheme based on multiscale analysis of the long range dependent traffic to address this challenge. In this proposed detection scheme, discrete wavelet transform is used to approximately de-correlate the traffic data and capture data characteristics in different time scales. The remaining dependencies are then captured by a multi-level hidden Markov model in the wavelet domain. To estimate the model parameters, we propose an online discounting Expectation Maximization (EM) algorithm, which also tracks variations of the estimated models over time. Network anomalies are detected as abrupt changes in the tracked model variation scores. We evaluate our detection scheme numerically using typical long range dependent time series.},
	address = {Orlando USA},
	booktitle = {50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC 2011)},
	pages = {pp. 4060-4065}
}
@conference {
	title = {Learning Behaviors for Coordination in Networked Systems and a Generalized Consensus Protocol},
	author = {Hovareshti, Pedram., Baras, John S.},
	year = {2011},
	month = {12/2011},
	abstract = {We consider the problem of coordination for efficient joint decision making in networks of autonomous agents. When making a decision, an agent is influenced by its knowledge about others{\textquoteright} behaviors. Agents{\textquoteright} understanding of others{\textquoteright} behaviors is shaped through observing their actions over a long time. We have modeled the decision making on whether to cooperate in a group effort as a result of a series of two-person games between agents, where the payoff of each agent is computed as the sum of its payoffs from each of these games. The agents initially have different behaviors. In order to maximize their pay-off, they need to learn the others{\textquoteright} behavior and coordinate with them. We consider a behavior learning algorithm for a class of behavior functions and study its effects on the emergence of coordination in the network. The conditions under which the learning algorithm converges are studied. We show that for a class of linear functions the learning algorithm results in an extension of non-homogeneous consensus protocol to the more general case of block-stochastic matrices.},
	address = {Orlando, Florida},
	booktitle = {50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC 2011)},
	pages = {pp. 2447-2452}
}
@conference {
	title = {Power Allocation Policy for Distributed Estimation in Wireless Networks},
	author = {Matei, Ion., Baras, John S.},
	year = {2011},
	month = {12/2011},
	abstract = {We consider a sensor network monitoring a stochastic process. The sensors exchange information over wireless communication channels affected by noise. The goal of the sensors is to compute accurate estimates of the state of the stochastic process under limited energy available for communications. We introduce a distributed algorithm which computes a power allocation scheme aimed at ensuring accurate state estimates and at saving communication energy. The distributed algorithm arise from solving an approximate convex optimization problem with constraints. We present how the power allocation scheme can be used for performing distributed estimation in the case where measurements are shared between sensors.},
	address = {Orlando, FL},
	booktitle = {50th IEEE Conference on Decision and Control Conference (CDC-ECC 2011)},
	pages = {pp. 7275-7280}
}
@conference {
	title = {Distributed Medium Access and Opportunistic Scheduling for Ad-Hoc Networks: An Analysis of the Constant Access Time Problem},
	author = {Chen, Hua., Hovareshti, Pedram., Baras, John S.},
	year = {2011},
	month = {12/2011},
	abstract = {In this paper, we study the problem of medium access and distributed opportunistic scheduling to exploit channel fluctuations for wireless ad-hoc networks. This work focuses on the Constant Access Time (CAT) problem, where the total time duration of channel probing and data transmission is slotted into fixed block length. In particular, we consider the dependence between channel rates at different time instances during the channel probing phase and its impact on the overall system throughput. We first analyze the system performance of the CAT problem under independent channel rate assumption and compare our result to the existing work on the Constant Data Time (CDT) problem. We then propose a protocol to reduce the channel probing costs based on this analysis. We show analytical results of the proposed protocol for systems with a sufficiently large number of users. We compare the system performance of the proposed protocol with that of the original protocol under independent channel rate assumption. We mathematically prove that the proposed protocol improves the system performance.},
	address = {Houston Texas},
	booktitle = {IEEE Globecom 2011},
	pages = {pp. 1-6}
}
@conference {
	title = {Thoughts Towards {\textquotedblleft}Science of Fingerprints},
	author = {Baras, John S.},
	year = {2011},
	month = {11/2011},
	address = {Salt Lake City, Utah},
	booktitle = {ARO Workshop on Fingerprinting}
}
@conference {
	title = {Factor Join Trees in Systems Exploration},
	author = {Yang, Shahan., Baras, John S.},
	year = {2011},
	month = {11/2011},
	abstract = {The interaction of connected components creates complexity impeding the analysis of large systems. Thorough exploration, appearing as formal verification, optimization or constraint satisfaction typically has a complexity that is either a high order polynomial or an exponential function of system size. However, for a large class of systems the essential complexity is linear in system size and exponential in treewidth which makes the previous notion of exponential complexity in system size an accidental overestimate.

In this paper, we demonstrate how this reduced complexity can be achieved using summary propagation on factor graphs. We describe summary propagation in terms of operations belonging to a commutative semiring-weighted relational algebra. We show how by appropriate selection of the commutative semiring, the same solution applies to propositional satisfiability, inference on Bayesian networks and a mixed integer linear optimization problem motivated by the power restoration problem for distributed, autonomous networks. This solution leads to a non-iterative distributed algorithm that operates on local data.

While weighted relational algebraic operators are used as the basic means of calculation, the algorithm presented works only on factor graphs that are trees. This requires the calculation of a non-unique structure called a join tree, which can be trivially generated from a unique structure called a cliqueseparator graph, which can be computed in linear time from a SysML Parametric Diagram description of the system for chordal systems1 . Interesting artifacts arise from this structural analysis which may be interpreted as interfaces and components. The framework also contains mathematical artifacts that may be interpreted as hierarchy and abstraction. We develop a tool to assist in the structural analysis described and implementations of the described algorithms.},
	address = {Paris, France},
	booktitle = {23rd International Conference on Software and Systems Engineering and their Applications (ICSSEA 2011)},
	pages = {pp. 1-12}
}
@conference {
	title = {Performance Evaluation of Single Channel Virtual-Circuit Medium Access Protocols for MANETs},
	author = {Perumal, Senni., Baras, John S.},
	year = {2011},
	month = {11/2011},
	abstract = {In this paper, we develop and evaluate models for estimating various performance metrics for unicast traffic using a single frequency channel virtual-circuit Medium Access Control (MAC) protocol in mobile wireless ad-hoc networks. Time is divided into periodic frames with a portion reserved for control traffic and the rest divided into timeslots for data traffic. In order to avoid interference between neighboring links, the virtualcircuit MAC protocol uses a set of reservation rules to assign timeslots to links. One such virtual-circuit MAC protocol is the hard scheduling mode of the reservation based Unifying Slot Assignment Protocol (USAP) with the number of frequency channels in a frame set to one. USAP uses a set of generic reservation rules to avoid interference between neighboring links. We model the performance of a single frequency channel virtualcircuit MAC protocol using reduced load loss network models that couple the physical, MAC, and routing layers effects. The blocking probability of a call at a particular link is calculated by considering cliques of neighboring interfering links that cannot transmit simultaneously. These neighboring interfering links and the conflict graph are calculated using the virtualcircuit reservation rules. We compare our results with simulation and show good match for large networks across various offered loads.},
	address = {Baltimore, Maryland},
	booktitle = {Milcom 2011},
	pages = {pp. 926-931},
	organization = {Baltimore Convention Center}
}
@conference {
	title = {Communication Network Challenges for Collaborative Vehicles},
	author = {Chen, Hua., Hovareshti, Pedram., Baras, John S.},
	year = {2011},
	month = {11/2011},
	abstract = {Networked systems of autonomous mobile agents have emerged in a variety of applications such as collaborative robotics, unmanned aerial/ground vehicles, mobile sensor networks and disaster relief operations. These agents utilize wireless communications for distributed computing, control and decision-making. Due to their limitations on energy supply, design and implementation of efficient distributed algorithms are crucial for these systems. This paper reviews different design aspects of networks of collaborative vehicles. We survey existing methods of addressing physical (PHY) and medium access control (MAC) layer, routing, and geometric connectivity issues for such networks and show limitations of these designs that address only single layer issues. We argue that a system engineering framework is needed for the design of such systems.},
	address = {Pacific Grove CA},
	booktitle = {Asilomar Conference on Signals, Systems, and Computers},
	pages = {pp. 1472-1476}
}
@conference {
	title = {A Model Based Platform for Design and Optimization of Multi-hop 802.11 Wireless Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Jain, Kaustubh.},
	year = {2011},
	month = {10/2011},
	abstract = {We develop a loss model for multi-hop wireless networks based on IEEE 802.11 MAC. Given a multi-hop network topology, connection demands and routes, we model the working of 802.11 MAC in DCF mode to find good approximations to average MAC layer losses, service times and carried load. The model is defined as an implicit function amongst the variables in the model and solved using a fixed point approach. Further, using Automatic Differentiation (AD) on the implicit function , we perform sensitivity analysis and use it in an optimization framework. As an illustration of how this model can help in design and optimization of wireless networks, we optimize the network throughput by appropriate load splitting along multiple paths. We validate our models using network simulations.},
	address = {Miami Beach, Florida},
	booktitle = {8th ACM International Symposium on Performance Evaluation of Wireless Ad Hoc, Sensor and Ubiquitous Networks (PE-WANSUN 201},
	pages = {pp. 17-24}
}
@conference {
	title = {A Systems Biology Model Studying the Role of Cholesterol in Alzheimer{\textquoteright}s Disease Progression},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2011},
	month = {10/2011},
	abstract = {A simplified network describing the interactions between the cholesterol and beta amyloid (Aβ) synthesis pathways was generated using information available from literature and the KEGG database. A system of non-linear differential equations was developed and modeled using several different initial conditions. Rate constants were approximated using ratiometric data from the literature, or by fitting parameters to obtain a stable simulation within given biological constraints. Simulations demonstrated the importance of negative feedback control by cholesterol in the regulation of beta-amyloid levels. Additionally, the effect of reduced LRP-1 levels and oscillatory cholesterol generation was studied.},
	address = {Kos Island, Greece},
	booktitle = {10th IEEE International Workshop on Biomedical Engineering (10thBioEng)},
	pages = {pp. 1-7}
}
@conference {
	title = {Return Channel Performance Evaluation of Enhanced SAMA VSAT with FMCSA and ACM Capability},
	author = {Perumal, Senni., Baras, John S., Roy-Chowdhury, Ayan., Petluri, Hemant S., Robinson, Mitch.},
	year = {2011},
	month = {10/2011},
	abstract = {In this paper, we describe our work on developing and evaluating detailed OPNET simulation models of an enhanced Very Small Aperture Terminal (VSAT) satellite Internet gateway and an enhanced satellite hub based on Cerona SkySPAN technology with capacity and latency optimizations in the return channel so as to allow significantly higher number of users and a better user experience. The Cerona SkySPAN technology uses Digital Video Broadcast via Satellite 2nd standard (DVB-S2) in the forward channel and Spread Aloha Multiple Access (SAMA) protocol in the return channel. We augment the SAMA return channel protocol with Fast Multi-Channel Slotted Aloha (FMCSA) protocol and Adaptive Coding and Modulation (ACM). FMCSA combines Multi-Channel Slotted Aloha (MCSA) with packet level forward error correction (FEC) for new messages and scheduled retransmissions for partially received messages. This protocol increases the maximum possible throughput of SAMA, thus supporting higher number of users. FMCSA also reduces the delay of multi-slot short messages (e.g., HTTP requests) while providing more robust delay performance with respect to load fluctuations, thus resulting in a better user experience. We incorporate Adaptive Coding and Modulation in the return channel in order to automatically adapt the coding and modulation to changing channel conditions so as to ensure remote data service irrespective of the channel degradation due to interference, rain fade or other conditions. We show via OPNET simulations that the enhanced SAMA VSAT with FMCSA and ACM improves the throughput, latency and robustness of the SkySPAN SAMA system. We also compare, via OPNET simulations, the enhanced SAMA system (with FMCSA and ACM) with a DVBRCS system to show improvements in user experience.},
	address = {Palermo, Italy},
	booktitle = {17th Ka and Broadband Communications, Navigation and Earth Observation Conference},
	pages = {pp. 417-424}
}
@conference {
	title = {Wireless Information Infrastructures and the Future Internet:  Protocol Components, System Architectures, Security and Privacy},
	author = {Baras, John S.},
	year = {2011},
	month = {10/2011},
	abstract = {Broadband Communication Infrastructures are expanding rapidly and are becoming ubiquitous. They are affecting every aspect of life and work. They are shaping the architecture, protocols and operation of the evolving future Internet. In this tutorial we describe major recent advances, challenges and opportunities in this critical area, from an integrated systems perspective. Hardware and physical layer advances are making possible new programmable types of networks and services. In the wireless arena physical layer advances mitigate interference (OFDM, MIMO, etc.) and will provide energy and bandwidth efficient and reliable communications. Services over the Future Internet and associated architectures are rapidly expanding and are increasingly interacting and integrated.},
	address = {Brest, France},
	booktitle = {Wireless Personal Multimedia Communications Symposium (WPMC{\textquoteright}11)}
}
@conference {
	title = {Multi-layer Coalitional Games and Agent Communications},
	author = {Baras, John S.},
	year = {2011},
	month = {09/2011},
	address = {Montecello, Illinois},
	booktitle = {49th Annual Allerton Conference}
}
@conference {
	title = {Control Science and Engineering: Providing Foundations for the Emerging Model-Based Systems engineering Discipline},
	author = {Baras, John S.},
	year = {2011},
	month = {09/2011},
	address = {Niskayuna, NY},
	booktitle = {General Electric Research Controls Symposium}
}
@conference {
	title = {Convergence results for the agreement problem on Markovian random topologies},
	author = {Matei, Ion., Baras, John S.},
	year = {2011},
	month = {08/2011},
	abstract = {We study the linear distributed asymptotic agreement(consensus) problem for a network of dynamic agents whose communication network is modeled by a randomly switching graph. The switching is determined by a finite state, Markov process, each topology corresponding to a state of the process. We address both the cases where the dynamics of the agents is expressed in continuous and discrete time. We show that, if the consensus matrices are doubly stochastic, convergence to average consensus is achieved in the mean square and almost sure sense, if and only if the graph resulted from the union of graphs corresponding to the states of the Markov process is strongly connected. The aim of this paper is to show how techniques from the theory of Markovian jump linear systems, in conjunction with results inspired by matrix and graph theory, can be used to prove convergence results for stochastic consensus problems.},
	address = {Milano, Italy},
	booktitle = {2011 IFAC World Conference},
	pages = {pp. 8860-8865}
}
@conference {
	title = {A systems biology model studying the role of cholesterol in Alzheimer{\textquoteright}s disease progression},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2011},
	month = {08/2011},
	abstract = {A simplified network describing the interactions between the cholesterol and beta amyloid (Aβ) synthesis pathways was generated using information available from literature and the KEGG database.~ A system of non-linear differential equations was developed and modeled using several different initial conditions.~ Rate constants were approximated using ratio-metric data from the literature, or by fitting parameters to obtain a stable simulation within given biological constraints.~ Simulations demonstrated the importance of negative feedback control by cholesterol in the regulation of beta-amyloid levels.~ Additionally, the effect of reduced LRP-1 levels and oscillatory cholesterol generation was studied.~},
	address = {Chicago, Illinois},
	booktitle = {ACM Conference on Bioinformatics, Computational Biology and~Biomedicine 2011}
}
@conference {
	title = {Generalized, Multi-criteria, Shortest path Problems on graphs, Idempotent Semirings, Dualities and the Value of Information},
	author = {Baras, John S.},
	year = {2011},
	month = {07/2011},
	abstract = {We investigate generalized shortest path problems on graphs with multiple metrics, that are generalized functions of numerical or logical link "weights". We demonstrate that these problems can be formulated as "linear Optimization or tradeoff problems over partially ordered semirings. We establish conditions for the semirings that guarantee distributed solutions. Considering the information needed for these computations~leads to convexity and duality notions, that help quantify the value of information in these distributed optimization problems.},
	address = {Baltimore, Maryland},
	booktitle = {2011 SIAM Control Conference}
}
@conference {
	title = {Learning and resilience to information deception in adversarial networked systems: the necessity and structure of a trusted core},
	author = {Baras, John S.},
	year = {2011},
	month = {07/2011},
	abstract = {We investigate disturbed inference and learning problems in networked systems with adversaries. We Analyze the effects of adversarial attacks on the solutions and characterize the solution robustness and resiliency as functions of~network topology and adversary distribution. We demonstrate that existence of a small subnetwork of "trusted nodes" (trusted core) could provide substantial improvements to solution robustness and resilience. We characterize these improvements as~functions of the degree of trust, connectivities and location of trusted nodes.},
	address = {Baltimore, Maryland},
	booktitle = {2011 SIAM Control Conference}
}
@conference {
	title = {Cooperative Swarms: the Interplay Between the Collaboration and Communication Multigraphs},
	author = {Baras, John S.},
	year = {2011},
	month = {07/2011},
	address = {Budapest, Hungary},
	booktitle = {Workshop on Flocking, Swarming and Control of Distributed Systems, Foundations of Computational Mathematics (FoCM{\textquoteright}11)}
}
@conference {
	title = {Studying Alzeihmer{\textquoteright}s disease pathogenesis using a systems biology approach},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2011},
	month = {07/2011},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is the most common form of dementia among the elderly, affecting approximately 1 in 6 individuals over the age of 65. To help study the progression of AD, we have developed a mixed metabolic-lipidomic-proteomic network to represent the key interactions in pathways that have been linked to AD. We will present simulation results which study how robust feedback plays an important role in the disease process, as well as how varying cholesterol and LRP concentration levels affects the level of beta amyloid in the system, such as is seen in AD.},
	address = {Seattle, Washington},
	booktitle = {Systems Biology Symposium 2011 (ISB 2011)}
}
@conference {
	title = {The Geometry of a Probabilistic Consensus of Opinion Algorithm},
	author = {Matei, Ion., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {We consider the problem of a group of agents whose objective is to asymptotically reach agreement of opinion. The agents exchange information subject to a communication topology modeled by a time-varying graph. The agents use a probabilistic algorithm under which at each time instant an agent updates its state by probabilistically choosing from its current state/opinion and the ones of its neighbors. We show that under some minimal assumptions on the communication topology (infinitely often connectivity and bounded intercommunication time between agents), the agents reach agreement with probability one. We show that this algorithm has the same geometric properties as the linear consensus algorithm in Rn. More specifically, we show that the probabilistic update scheme of an agent is equivalent to choosing a point from the (generalized) convex hull of its current state and the states of its neighbors; convex hull defined on a particular convex metric space where the states of the agents live and for which a detailed description is given.},
	address = {San Francisco, CA},
	booktitle = {2011 American Control Conference},
	pages = {pp.  2198-2205}
}
@conference {
	title = {Selfish response to Epidemic Propagation},
	author = {Theodorakopoulos, George., Le Boudec, Jean-Yves., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {An epidemic spreading in a network calls for a decision on the part of the network members: They should decide whether to protect themselves or not. Their decision depends on the trade-off between their perceived risk of being infected and the cost of being protected. The network members can make decisions repeatedly, based on information that they receive about the changing infection level in the network. We study the equilibrium states reached by a network whose members increase (resp. decrease) their security deployment when learning that the network infection is higher (resp. lower). Our main result is that as the learning rate of the members increases, the equilibrium level of infection increases. We demonstrate this result both when members are strictly rational and when they are not. We characterize the domains of attraction of the equilibrium points.We validate our conclusions with simulations on human mobility traces.},
	address = {San Francisco, CA},
	booktitle = {2011 American Control Conference},
	pages = {pp. 4069-4074}
}
@conference {
	title = {Trust-Assisted Anomaly Detection and Localization in Wireless Sensor Networks},
	author = {Zheng, Shanshan., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {Fast anomaly detection and localization is critical to ensure effective functioning of wireless sensor networks. The low bandwidth and power constraints in wireless sensor networks are the main challenges for achieving this task, especially for large scale networks. In this paper, we propose a trust-assisted framework for detecting and localizing network anomalies in a hierarchical sensor network. The proposed method makes inference based on end-to-end measurements collected by a set of measurement nodes. Network heterogeneity is exploited for better bandwidth and energy efficiency. The trustworthiness of network links is utilized to design an efficient two-phase probing strategy that can achieve a flexible tradeoff between inference accuracy and probing overhead. We performed experiments with different network settings and demonstrated the effectiveness of our proposed algorithms.},
	address = {Salt Lake City, Utah},
	booktitle = {8th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON) 2011},
	pages = {pp.  386-394}
}
@conference {
	title = {On the complexity of a social behavior model},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {In this paper, we discuss a social behavior model in cellular automata. This model came as a result of research in dynamical structures of networks as these were constructed out of game theory and statistical physics. We define it a dynamical system on the planar grid and study its behavior by varying its parameters under different initial configurations.},
	address = {Quincy, MA},
	booktitle = {Eighth International Conference on Complex Systems (ICCS 2011)},
	pages = {pp.  1330-1344},
	organization = {Boston Marriott}
}
@conference {
	title = {Motif-based Topology Design for Effective Performance by Networks of Mobile Autonomous Vehicles},
	author = {Hovareshti, Pedram., Chen, Hua., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {To design efficient local connectivity patterns, we have used the idea of network motifs, which was first proposed in the context of biological networks. Network motifs are task specific local connectivity patterns, which exist with much higher frequency in real biological networks compared to those in random networks. These are sub-networks of a low number of nodes (usually 3-4) whose persistence in networks performing similar tasks in different contexts, imply their efficiency in the sense that they optimize certain performance metric in a local scale. We use a simulation test bed to find network motifs for local level communication structures in a collaborative vehicles framework. Here, the group mission consists of several tasks that the agents participate in. The tasks include search operation, data gathering/processing, target finding and leader-follower explorations. Each task gives rise to certain motifs that are specific to that task and the partial knowledge of the environment specifications that the agents operate in. In this way, given the subtasks that are necessary for the mission accomplishment, the most efficient task-specific local topologies are extracted. Switching suitable graphs when the mode of operation is changing can be handled by solving the resulting reachability problem using methods for symbolic planning such as graph grammars. Based on such switching, we also address the effects of split/merge operations on the spectral characteristics of the resulting connectivity graphs.},
	address = {Quincy, MA},
	booktitle = {Eighth International Conference on Complex Systems (ICCS 2011),},
	pages = {pp.  571-573}
}
@conference {
	title = {Cooperative networked systems: Multiple graphs, coalitional games, new probabilistics models},
	author = {Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {The consideration of cooperative networked systems has raised fundamental new questions and challenges. We consider networked systems from various domains including control, communications, sensing, sociology, economics, and biology. We first describe a general model for modeling such systems that involve several interacting dynamic multigraphs. These multigraphs evolve in at least three planes. At the higher plane (layer) we have the network of cognitive agents, where decisions are made and executed. At the intermediate plane (layer) we have the information network, where data, models, observations and signaling are represented. At the lower plane (layer) we have the communication network that supports the information and agent networks. There are several ways to capture these ideas and principles, and the one presented here is one of the simpler possible representations. The lower layer is more connected to the physical layer, while the middle and higher layer is more logical. The networks involve have links and nodes that are annotated by weights that can be scalar, vector or even policies and rules. Furthermore, the networks are dynamic. The resulting dynamic models are very complex and require a combination of methods from analysis, algebra, logic and optimization. The simplest possible model involves two interacting multigraphs: (a) the collaboration multigraph, which describes the time varying relation of collaboration between the agents; and (b) the communication multigraph, which describes the time-varying communications that occur between the agents. We link these concepts to ideas from distributed computing, distributed programs, and distributed computer hardware. We also link this representation to the behavior and structure models used in modern model-based-systems engineering. We describe a novel path-oriented characterization of these activities in networked dynamic systems. Next, we introduce three fundamental problems and challenges emerging from this framework. The first addresses the joint analysis of the collaboration and communication multigraphs and their impact on the performance of the networked system. The second fundamental problem addresses the development of a taxonomy of collaboration and communication multigraphs, from the perspective of system performance. The third fundamental problem addresses the need for different probability models for such cooperative networked systems. We relate the new framework, emerging from the results of the first and second problems, and its basic constructs, to information and control patterns, generalized information theory and entropy, and to distributed computing with local states. This new framework indicates the need for a new kind of probability over dynamical logical structures that is reminiscent of the axiomatic framework of quantum physics.},
	address = {Corfu Island, Greece},
	booktitle = {Control \&amp; Automation (MED), 2011 19th Mediterranean Conference},
	pages = {pp. no. 798-800}
}
@conference {
	title = {Sequential Anomaly Detection in Wireless Networks and Effects of Long Range Dependent Data},
	author = {Baras, John S., Zheng, Shanshan.},
	year = {2011},
	month = {06/2011},
	abstract = {Anomaly detection is an important but difficult task for wireless networks such as mobile ad hoc networks (MANET) and wireless sensor networks (WSN). We present various sequential detection schemes for anomaly detection in such networks including protocol violation, wormhole attacks, fraudulent data injection or algorithm modification. We present both parametric and non parametric algorithms, as well as centralized and distributed schemes. Recent studies have shown that node mobility along with spatial correlations of the monitored traffic in such wireless networks can lead to long range dependent (LRD) traffic, which could significantly increase the difficulty of anomaly detection. We next analyze the effects of LRD traffic on these sequential anomaly detection schemes. Various models of LRD traffic are considered. In the proposed schemes, wavelet transforms are used to approximately de-correlate the traffic data and capture data characteristics at different time scales. The remaining dependencies are then captured by a multilevel hidden Markov model in the wavelet domain. To estimate the model parameters, we proposed an online discounting Expectation Maximization (EM) algorithm, which also tracks variations of the estimated models over time. Network anomalies are then detected as abrupt changes in the tracked model variation scores. We develop statistical properties of these detection schemes as well as performance results, especially stemming from using incorrect short range dependent traffic models.},
	address = {Palo Alto, CA},
	booktitle = {International Workshop on Sequential Methodologies (IWSM 2011)},
	organization = {Stanford University}
}
@conference {
	title = {Challenges and Opportunities for Future Broadband Networks: From Physical to Services to Social},
	author = {Baras, John S.},
	year = {2011},
	month = {06/2011},
	booktitle = {Kick-off meeting of the new center of excellence Labex Comin Labs}
}
@conference {
	title = {Exploiting Trust Relations for Nash Equilibrium Efficiency in Ad Hoc Networks},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {Ad hoc networks rely on the mutual cooperation among individual nodes to achieve network-wide objectives. However, individual nodes may behave selfishly in order to maximize their own benefits without considering the global benefits of the network. One approach to incentivize nodes cooperation for better global benefits is to establish trust relations among nodes to guide their decision making. In this paper, we present a game theoretic analysis for the efficiency of establishing trust for improving node cooperation. The trust relations among nodes are modeled as a trust-weighted network, and we study a graphical game in this network where the nodes{\textquoteright} payoffs are affected by their trust relations. We characterize the Nash equilibrium and the social optimum of this game and show that the game efficiency has a close relationship to the Bonacich centralities of nodes in the trust-weighted network. Furthermore, we propose to improve game efficiency by introducing heterogeneous resources to nodes according to their centralities. We provide both experimental and theoretical analysis on the improvement of the game efficiency.},
	address = {Kyoto, Japan},
	booktitle = {IEEE International Conference on Communications (ICC 2011)},
	pages = {pp.1-5}
}
@conference {
	title = {Performance Analysis of Time-Critical Peer-to-Peer Communications in IEEE 802.15.4 Networks},
	author = {Wang, Baobing., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {Existing works on the performance analysis of IEEE 802.15.4 networks with peer-to-peer (P2P) topologies assume the non-beacon unslotted mode in the MAC layer, which is not suitable for time-critical communications required by many applications, such as control, actuation and monitoring applications. In this paper, we introduce an enhanced guaranteed timeslot (GTS) mechanism which can support time-critical P2P communications in wireless sensor networks (WSNs). A Markov chain that takes into account retransmission limits, acknowledgements, unsaturated traffic and packet delivery ratios of links is proposed to model P2P communications using this enhanced GTS mechanism. Based on this model, we analyze the expected reliability and energy consumptions under various traffic conditions. In addition, the impacts of MAC parameters on these performance indexes are analyzed. Monte Carlo simulations show that our theoretical analysis is quite accurate, and thus can be used as guidance for networks configuration in WSNs.},
	address = {Kyoto, Japan},
	booktitle = {IEEE International Conference on Communications (ICC 2011)},
	pages = {pp. 1-6}
}
@conference {
	title = {A Robust Collaborative Filtering Algorithm Using Ordered Logistic Regression},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2011},
	month = {06/2011},
	abstract = {The Internet offers tremendous opportunities for information sharing and content distribution. However, without proper filtering and selection, the large amount of information may likely swarm the users rather than benefit them. Collaborative filtering is a technique for extracting useful information from the large information pool generated by interconnected online communities. In this paper, we develop a probabilistic collaborative filtering algorithm, which is based on ordered logistic regression and takes into account both similarities among the users and similarities among the items. We make inference with maximum likelihood and Bayesian frameworks, and propose a Markov Chain Monte Carlo based Expectation Maximization algorithm to optimize model parameters. The power of our proposed algorithm is its extensibility. We show that it can incorporate content and contextual information. More importantly, it can be easily extended to include the trustworthiness of users, thus being more robust to malicious data manipulation. The experimental results on a real world data set show that our proposed algorithm with the trust extension is robust under different types of attacks in recommendation systems.},
	address = {Kyoto, Japan},
	booktitle = {IEEE International Conference on Communications (ICC 2011)},
	pages = {pp. 1-6}
}
@conference {
	title = {Chaos On A Simple Rational Planar Map},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2011},
	month = {05/2011},
	abstract = {The dynamics of a 2-D rational map are studied for various values of it{\textquoteright}s control parameters. Despite it{\textquoteright}s simple structure this model is very rich in non-linear phenomena such as, multi-scroll strange attractors, transitions to chaos via period doubling bifurcations, quasi-periodicity as well as intermittency, interior crisis, hyper-chaos etc. In this work, strange attractors, bifurcation diagrams, periodic indows, invariant characteristics are investigated both analytically and numerically.},
	address = {Crete, Greece},
	booktitle = {4th Chaotic Modeling and Simulation International Conference (CHAOS 2011)},
	pages = {pp. 1-9},
	organization = {Agios Nikolaos }
}
@conference {
	title = {AUTHENTICATION OF FINGERPRINT SCANNERS},
	author = {Ivanov, Vladimir I., Baras, John S.},
	year = {2011},
	month = {05/2011},
	abstract = {Fingerprint scanners have unique patterns that can be used to distinguish one scanner from another one. The pattern, which we call scanner pattern, stems from the variability of device characteristics at silicon level and is caused by imperfections of the conversion from the input to the scanner (i.e., the object applied to it) to its output (i.e., the digital image). The scanner pattern is a sufficiently unique and persistent intrinsic characteristic of the fingerprint scanners even to those of the same technology, manufacturer, and model. We propose a simple and extremely accurate algorithm that is able to distinguish the pattern of one scanner from the pattern of another scanner of exactly the same model by extracting the pattern from a single image, acquired with each scanner. In this way, the scanner pattern can be used to enhance the security of a biometric system by authenticating the scanner, used to acquire a particular fingerprint image, and thus detect attacks on the scanner. Combining the biometric authentication with a scanner authentication leads to a two-part authentication, which we call bipartite authentication, that verifies both the identity of the user and the {\textquotedblleft}identity{\textquotedblright} of the fingerprint scanner.},
	address = {Prague, Czech Republic},
	booktitle = {1993 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2011)},
	pages = {pp.  1912-1915}
}
@conference {
	title = {Physical Layer Security and Trust Mechanisms: Critical and Indispensable},
	author = {Baras, John S.},
	year = {2011},
	month = {04/2011},
	address = {Washington DC},
	booktitle = {2nd Army Research Office Special Workshop on Hardware Assurance}
}
@conference {
	title = {Network Science Principles and Cooperative Networked Systems},
	author = {Baras, John S.},
	year = {2011},
	month = {03/2011},
	address = {Beijing, China},
	booktitle = {The Institute of Systems Science (ISS) of the Chinese Academy of Mathematics and Systems Science (AMSS)}
}
@conference {
	title = {Studying Real-time Traffic in Multi-hop Networks Using the EMANE Emulator: Capabilities and Limitations},
	author = {Jain, Kaustubh., Roy-Chowdhury, Ayan., Somasundaram, Kiran K., Wang, Baobing., Baras, John S.},
	year = {2011},
	month = {03/2011},
	abstract = {In this paper, we provide an open-source software emulator setup for MANETs and study its fidelity in providing reliable performance estimates for real-time traffic. We emulate the IEEE 802.11 MAC/PHY (DCF) using the EMANE software emulator deployed on a cluster and run experiments for different multi-hop wireless scenarios. As an instance, we study the performance of real-time streaming media over a mesh network supported by OLSR. We also use the setup to analyze the impact of the wireless network on the self-similarity of the traffic.},
	address = {Barcelona, Spain},
	booktitle = {SIMUTools 2011- 4th International Conference on Simulation Tools and Techniques},
	pages = {pp. 93-95}
}
@conference {
	title = {Component-based Architectures for the Synthesis of Intelligent Networked Systems},
	author = {Baras, John S.},
	year = {2011},
	month = {03/2011},
	abstract = {Advances in Information Technology have enabled the design of complex networked systems, with large number of heterogeneous components and capable of multiple complex functions. These advances have at the same time increased the capabilities of such systems and have increased their complexity to such an extent that systematic design towards predictable performance is extremely difficult if not unfeasible today. This is especially manifested in the area of cyber-physical systems, of all scales, that have become ubiquitous. In addition, the need for systems that can rapidly adapt to new situations and change their structure and behavior accordingly has also increased dramatically. We present methodologies that show promise in addressing these challenges. They include model-based systems engineering, component-based synthesis and architectural design towards efficiency and adaptability. We demonstrate their effectiveness in various applications: collaborative robotics, collaborative heterogeneous sensor networks, cyber security of critical infrastructures, human-machine teams and organizations, and composite trust.},
	address = {Kunming, China},
	booktitle = {IEEE-CYBER 2011},
	pages = {pp. 10-11}
}
@conference {
	title = {Modeling Alzheimer{\textquoteright}s Disease Using A Systems Biology Approach},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2011},
	month = {03/2011},
	abstract = {Alzheimers disease (AD) is the most common form of dementia afflicting the elderly today and is believed to be caused by the buildup of the beta amyloid protein (A{\ss}) within the brain and cerebral vasculature. Although a vast amount of knowledge exists, there is currently no definitive understanding of the initiating factor and subsequent pathogenesis, partially due to the difficulty in directly studying or manipulating the brain experimentally. To overcome this problem, we have developed a systems-level network that encompasses metabolic, lipidomic, and proteomic network topologies, taking into account known feedback and regulation mechanisms. By studying the interactions between the different networks computationally, we have identified several nodes which may be key for initiating a change from a healthy network state to a disease state. We have also performed in vivo experiments in APP/Swe/PS1 transgenic mice to study the effect of simvastatin, a cholesterol inhibitor and potent anti-inflammatory, on the expression levels of A{\ss}, APP, LRP-1 and apoE. These experiments, in combination with our computational model, help to identify crucial feedback points and provide the first known attempt to model AD from a systems-level standpoint.},
	address = {Baltimore, MD},
	booktitle = {Proceedings of the 2011 Biophysical Society}
}
@conference {
	title = {Cooperative Networked Systems: Multiple Graphs and Games},
	author = {Baras, John S.},
	year = {2011},
	month = {02/2011},
	address = {Atlanta, Georgia},
	booktitle = {Decision and Control Laboratory Seminar},
	organization = {Georgia Institute of Technology}
}
@conference {
	title = {Path Optimization and Trusted Routing in MANET: An Interplay Between Ordered Semirings},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2010},
	month = {12/2010},
	abstract = {In this paper, we formulate the problem of trusted routing as a transaction of services over a complex networked environment. We present definitions from service-oriented environments that unambiguously capture the difference between trust and reputation relations. We show that the trustworthiness measures associated with these relations have a linear order embedded in them. Identifying this order structure permits us to treat the trusted routing problem as a bi-objective path optimization problem. We consider bottleneck trust and present polynomial time solutions to obtain the optimal routing paths in various bi-objective settings. In developing these algorithms, we identify an interesting decomposition principle for (min,+) and (min,max) semirings, which yields a distributed solution.},
	address = {Chennai, India},
	booktitle = {The Second International Conference on Networks \&amp; Communications (NetCoM - 2010)},
	pages = {pp. 1-11}
}
@conference {
	title = {Consensus-Based Linear Distributed Filtering},
	author = {Matei, Ion., Baras, John S.},
	year = {2010},
	month = {12/2010},
	abstract = {We address the consensus-based distributed linear filtering problem, where a discrete time, linear stochastic process is observed by a network of sensors. We assume that the consensus weights are known and we first provide sufficient conditions under which the stochastic process is detectable, i.e. for a specific choice of consensus weights there exists a set of filtering gains such that the dynamics of the estimation errors (without noise) is asymptotically stable. Next, we provide a distributed, sub-optimal filtering scheme based on minimizing an upper bound on a quadratic filtering cost. In the stationary case, we provide sufficient conditions under which this scheme converges; conditions expressed in terms of the convergence properties of a set of coupled Riccati equations. We continue with presenting a connection between the consensus based distributed linear filter and the optimal linear filter of a Markovian jump linear system, appropriately defined. More specifically, we show that if the Markovian jump linear system is (mean square) detectable, then the stochastic process is detectable under the consensus-based distributed linear filtering scheme. We also show that the optimal gains of a linear filter for estimating the state of a Markovian jump linear system appropriately defined can be used to approximate the optimal gains of the consensus-based linear filter.},
	address = {Atlanta, Georgia},
	booktitle = {49th IEEE Conference on Decision and Control (CDC 2010)},
	pages = {pp.  7009- 7014}
}
@conference {
	title = {Distributed Topology Control for Stable Path Routing in Multi-hop Wireless Networks},
	author = {Somasundaram, Kiran K., Baras, John S., Jain, Kaustubh., Tabatabaee, Vahid.},
	year = {2010},
	month = {12/2010},
	abstract = {In this paper, we introduce the stable path topology control problem for routing in mobile multi-hop networks. We formulate the topology control problem of selective linkstate broadcast as a graph pruning problem with restricted local neighborhood information. We develop a multi-agent optimization framework where the decision policies of each agent are restricted to local policies on incident edges and independent of the policies of the other agents. We show that under a condition called the positivity condition, these independent local policies preserve the stable routing paths globally. We then provide an efficient algorithm to compute an optimal local policy that yields a minimal pruned graph, which we call the Stable Path Topology Control (SPTC) algorithm. Using simulations, we demonstrate that this algorithm, when used with the popular ETX metric, outperforms topology control mechanisms commonly used for Mobile Ad Hoc Networks.},
	address = {Atlanta, Georgia},
	booktitle = {49th IEEE Conference on Decision and Control (CDC 2010)},
	pages = {pp.  2342-2347}
}
@conference {
	title = {Robust State Estimation Under False Data Injection in Distributed Sensor Networks},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2010},
	month = {12/2010},
	abstract = {Distributed sensor networks have been widely employed to monitor and protect critical infrastructure assets. The network status can be estimated by centralized state estimation using coordinated data aggregation or by distributed state estimation, where nodes only exchange information locally to achieve enhanced scalability and adaptivity to network dynamics. One important property of state estimation is robustness against false data injection from sensors compromised by attackers. Different from most existing works in the literature that focus on centralized state estimation, we propose two novel robust distributed state estimation algorithms against false data injection. They are built upon an existing distributed Kalman filtering algorithm. In the first algorithm, we use variational Bayesian learning to estimate attack parameters and achieve performance similar to a centralized majority voting rule, without causing extra communication overhead. In the second algorithm, we introduce heterogeneity into the network by utilizing a subset of pre-trusted nodes to achieve performance better than majority voting. We show that as long as there is a path connecting each node to some of the pre-trusted nodes, the attackers can not subvert the network. Experimental results demonstrate the effectiveness of our proposed schemes.},
	address = {Miami, Florida},
	booktitle = {IEEE Globecom 2010},
	pages = {pp.1-5}
}
@conference {
	title = {A systems biology model studying the role of cholesterol in Alzheimer{\textquoteright}s disease pathogenesis},
	author = {Kyrtsos, C Rose., Lee, Hey-Kyoung., Baras, John S.},
	year = {2010},
	month = {11/2010},
	abstract = {Objective: To develop a systems-level, metabolic network model to study the effect that alterations in the brain cholesterol concentration levels have on downstream or interconnected sub-networks in an Alzheimer{\textquoteright}s disease (AD) model.Methods: A simplified network encompassing both basic metabolic networks such as glucose and amino acid metabolism, as well as APP processing, cholesterol metabolism, and cholesterol-related metabolic pathways was generated using pathways described by either the KEGG database or in the literature. A differential equations model describing the distribution of molecules within the network over time was developed and simulated using Matlab. The model was initialized using healthy concentrations of all pertinent and known quantities. Individual molecules were represented by nodes in the topological mapping, while reactions between different molecules were designated by weighted links. The weights of the links were determined stoichiometrically, where possible, or statistically, if data was not available.Results: Our results are one of the first attempts to study Alzheimer{\textquoteright}s disease using a systems biology approach. This approach is unique in that it allows us to merge the creation of a systems-level quantitative model for the brain metabolic network with data obtained from in vivo experiments to generate the most accurate mathematical model using current knowledge. The topology of the initially-generated network showed crucial overlap between the APP clearance pathway and cholesterol distribution pathway in adults, specifically with the shared usage of apolipoprotein E (apoE) as a carrier for both beta amyloid (Aβ) cholesterol, and with the LDL receptor-related protein (LRP-1) as a necessary transport protein for Aβ out of the brain and cholesterol into neurons. Short run simulations of networks with decreased brain cholesterol synthesis showed slight increases in the concentration levels of Aβ.Conclusion: We have developed a systems-level, pseudo-metabolic network for the basic metabolic pathways in the brain that are pertinent to the development of AD. Analysis of the network structure revealed several important topological homologies between APP and cholesterol processing. Given our results and the important role that cholesterol plays in maintaining normal neuronal function, it is likely that decreased cholesterol will negatively affect functioning of neurons. Our future work will use an in vivo mouse model to study the effects of decreased brain cholesterol on AD pathology.},
	address = {San Diego, CA},
	booktitle = {40th Annual Meeting Neuroscience 2010}
}
@conference {
	title = {Opportunistic Communications for Networked Controlled Systems of Autonomous Vehicles},
	author = {Chen, Hua., Hovareshti, Pedram., Baras, John S.},
	year = {2010},
	month = {10/2010},
	abstract = {Situational awareness requires maintaining a reasonable level of communication connectivity in networks of autonomous vehicles. It is difficult to overcome deep fading from time-varying wireless channels in a dynamic and resource constrained environment. Moreover, other system constraints such as the energy consumption and total operation time make the design of communication protocols for such systems more challenging. In this paper, we consider the problem of efficient communications between a group of autonomous vehicles with energy consumption and total operation time constraints in an adversarial environment. We show that the policy of continuously attempting to communicate reliably over the course of the mission may lead to considerable system degradation. We propose an adaptive algorithm to make communication attempts opportunistically, based on the qualities of the wireless channels as the vehicles move throughout the terrain. We compare the proposed algorithm with a non-opportunistic algorithm in which the vehicles blindly attempt to communicate regularly throughout the course of the mission. We show that the proposed algorithm significantly improves the system performance, both in terms of operation time when the agents transmit only situational information and data throughput when additional data transmission is necessary.},
	address = {San Jose, CA},
	booktitle = {2010 Military Communications Conference (MILCOM 2010)},
	pages = {pp. 1306-1311}
}
@conference {
	title = {Modeling TDMA-Based USAP in JTRS MDL for Multicast and Unicast Traffic},
	author = {Perumal, Senni., Tabatabaee, Vahid., Baras, John S., Graff, Charles J., Yee, David G.},
	year = {2010},
	month = {10/2010},
	abstract = {In this paper, we develop loss network models for the hard scheduling mode (virtual circuit mode) of the reservation based USAP scheduling protocol as used in the Mobile Data Link (MDL) of the Joint Tactical Radio System (JTRS). These models are used to find performance metric estimates for both multicast and unicast traffic. USAP (Unifying Slot Assignment Protocol) is a dynamic distributed resource allocation protocol for mobile multihop wireless networks where the channel is partitioned in time and frequency. MDL creates a backbone sub-network and routes all traffic through this sub-network. For the backbone sub-network, we consider algorithms that form Connected Dominating Sets. We use loss network models that couple the physical, MAC, and routing layers effects. The effect of the MAC layer is modeled by approximating available capacity at a node. The available capacity to transmit is computed based on the USAP reservation rules and the node{\textquoteright}s 2-hop neighborhood traffic. For a given time varying scenario, we compute the performance metrics of blocking probability and throughput for both multicast and unicast traffic as a function of time. We compare the results of our model against simulation.},
	address = {San Jose, CA},
	booktitle = {2010 Military Communications Conference (MILCOM 2010)},
	pages = {pp. 1464-1469}
}
@conference {
	title = {VSAT return Channel Optimizations for Broadband Internet Support in 2-Way Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S., Robinson, Mitch.},
	year = {2010},
	month = {10/2010},
	abstract = {In this paper we describe our work on a Very Small Aperture Terminal (VSAT) satellite Internet gateway with capacity and latency optimizations in the return channel so as to allow significantly higher number of users, and a better user experience. The gateway is based on the Cerona SkySPAN technology which uses the Digital Video Broadcast via Satellite 2nd standard (DVB-S2) in the forward channel, and single-channel slotted Aloha protocol in the return channel. In this paper we describe the Spread Aloha Multiple Access (SAMA) protocol which we implement in the return channel. The SAMA protocol promises to deliver high speeds at a third of the latency compared to competing technologies like DVB-RCS (multi-frequency TDMA), while allowing the same number of users in 3MHz bandwidth as is possible in TDMA using 36MHz. We also describe the implementation of the Fast Multi-channel Slotted Aloha (FMCSA) protocol that will co-exist with SAMA in the return channel. FMCSA combines slotted Aloha random access with packet level forward error correction (FEC) for new messages and scheduled retransmissions for partially received messages. Due to the parity packets sent in FMCSA, more load is offered to the channel than in SAMA to achieve the same throughput. The delay performance of FMCSA is also much more robust to load fluctuations than SAMA. The combination of SAMA and FMCSA improves the robustness and throughput of the SkySPAN return channel and reduces the channel latency, while supporting significantly higher number of users, in comparison to the competition.},
	address = {Milan, Italy},
	booktitle = {16th Ka and Broadband Communications Conference},
	pages = {pp. 479-486}
}
@conference {
	title = {The Role of Cholesterol in Alzheimer{\textquoteright}s disease Pathogenesis: Preliminary Report},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2010},
	month = {10/2010},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is a devastating neurodegenerative disorder affecting 1 in 8 individual over the age of 65. A growing body of evidence is suggesting that cholesterol levels in both the brain and the plasma may play significant roles in AD pathogenesis; however, the exact nature of this role is currently not well understood. Building on previous experiments, we have approached this problem using two, complementary methods- a systems biology model for brain metabolic networks that is based on empirical data gathered from in vivo experiments. The main goal of this study was to determine the effect that decreased brain cholesterol had on the level of beta amyloid (the key protein implicated in AD pathogenesis) and the extent of neurodegeneration observed. To achieve this, APPSwe/PS1 double transgenic mice were treated twice daily with simvastatin (a cholesterol-lowering drug) for a period of 2 or 10 weeks. The effects of the decreased brain cholesterol levels on APP and beta amyloid processing, as well as apoE and LRP-1 expression levels was studied using Western blotting and immunohistochemistry techniques, respectively. The extent of neurodegeneration was determined via immunohistochemical staining of hippocampal slices for synaptic density and neuron viability. The weights between key nodes in the systems biology model were updated to account for the observed experimental results.},
	address = {Austin, Texas},
	booktitle = {Biomedical Engineering Society (BMES 2010)}
}
@conference {
	title = {Trust-aware State Estimation Under False Data Injection In Distributed Sensor Networks},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2010},
	month = {09/2010},
	abstract = {Distributed sensor networks have been widely employed to monitor and protect critical infrastructure assets. The network status can be estimated by centralized state estimation using coordinated data aggregation or by distributed state estimation, where nodes only exchange information locally to achieve enhanced scalability and adaptivity to network dynamics. One important property of state estimation is robustness against false data injection from sensors compromised by attackers. Different from most existing works in the literature that focus on centralized state estimation, we propose two novel robust distributed state estimation algorithms against false data injection. They are built upon an existing distributed Kalman filtering algorithm. In the first algorithm, we use variational Bayesian learning to estimate attack parameters and achieve performance similar to a centralized majority voting rule, without causing extra communication overhead. In the second algorithm, we introduce heterogeneity into the network by utilizing a subset of pre-trusted nodes to achieve performance better than majority voting. We show that as long as there is a path connecting each node to some of the pre-trusted nodes, the attackers can not subvert the network. Experimental results demonstrate the effectiveness of our proposed schemes.},
	address = {Austin, Texas},
	booktitle = {TECHCON 2010},
	pages = {pp. 1-4}
}
@conference {
	title = {Stochastic Average Consensus Filter for Distributed HMM Filtering: Almost Sure Convergence},
	author = {Ghasemi, Nader., Dey, Subhrakanti., Baras, John S.},
	year = {2010},
	month = {09/2010},
	abstract = {This paper studies almost sure convergence of a dynamic average consensus algorithm which allows distributed computation of the product of n time-varying conditional probability density functions. These conditional probability density functions (often called as {\textquotedblleft}belief functions{\textquotedblright}) correspond to the conditional probability of observations given the state of an underlying Markov chain, which is observed by n different nodes within a sensor network. The network topology is modeled as an undirected graph. The average consensus algorithm is used to obtain a distributed state estimation scheme for a hidden Markov model (HMM), where each sensor node computes a conditional probability estimate of the state of the Markov chain based on its own observations and the messages received from its immediate neighbors. We use the ordinary differential equation (ODE) technique to analyze the convergence of a stochastic approximation type algorithm for achieving average consensus with a constant step size. This allows each node to track the time varying average of the logarithm of conditional observation probabilities available at the individual nodes in the network. It is shown that, for a connected graph, under mild assumptions on the first and second moments of the observation probability densities and a geometric ergodicity condition on an extended Markov chain, the consensus filter state of each individual sensor converges almost surely~to the true average of the logarithm of the conditional observation probability density functions of all the sensors. Convergence is proved by using a perturbed stochastic Lyapunov function technique. Numerical results suggest that the distributed Markov chain state estimates obtained at the individual sensor nodes based on this consensus algorithm track the centralized state estimate (computed on the basis of having access to observations of all the nodes) quite well, while more formal convergence results for the distributed HMM filter to the centralized one are currently under investigation.},
	address = {Annecy, France},
	booktitle = {2nd IFAC Workshop on Distributed Estimation and Control in Networked Systems (NecSys{\textquoteright}10)},
	pages = {pp. 335-340}
}
@conference {
	title = {The asymptotic consensus problem on convex metric spaces},
	author = {Matei, Ion., Baras, John S.},
	year = {2010},
	month = {09/2010},
	abstract = {We consider the consensus problem of a group of dynamic agents whose communication network is modeled by a directed time-varying graph. In this paper we generalize the asymptotic consensus problem to convex metric spaces. A convex metric space is a metric space endowed with a convex structure. Using this convex structure we define convex sets and in particular the convex hull of a (finite) set. Under minimal connectivity assumptions, we show that if at each iteration an agent updates its state by choosing a point from a particular subset of the convex hull generated by the agent{\textquoteright}s current state and the states of its neighbors, then asymptotic agreement is achieved. In addition, we give bounds on the distance between the consensus point and the initial values of the agents.},
	address = {Annecy, France},
	booktitle = {2nd IFAC Workshop on Distributed Estimation and Control in Networked Systems (NecSys{\textquoteright}10)},
	pages = {pp. 287- 292}
}
@conference {
	title = {A Network Model of Alzheimer{\textquoteright}s disease},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2010},
	month = {07/2010},
	abstract = {We have derived a multi-scale network model to study the relationship between cholesterol and Aβ in silico to integrate with future experimental work. A pseudo-metabolic network approach has been taken to model the interactions between various signaling molecules, carrier and transport proteins, as well as other proteins that are considered pertinent to AD pathogenesis. We have also monitored the number of neurons and related synapses using a modified McCulloch-Pitts neural network.},
	address = {Pittsburgh, Pennsylvania},
	booktitle = {2010 SIAM Life Sciences Conference}
}
@conference {
	title = {Performance Evaluation of Multi-Agent Distributed Collaborative Optimizationunder Random Communication Topologies},
	author = {Matei, Ion., Baras, John S.},
	year = {2010},
	month = {07/2010},
	abstract = {We investigate collaborative optimization in a multi-agent setting, when the agents execute in a distributed manner using local information, while the communication topology used to exchange messages and information is modeled by a graph-valued random process, independent of other time instances. Specifically, we study the performance of the consensus-based multi-agent subgradient method, for the case of a constant stepsize, as measured by two metrics: rate of convergence and guaranteed region of convergence, evaluated via their expected values. Under a strong convexity type of assumption, we provide upper bounds on the performance metrics, which explicitly depend on the probability distribution of the random graph and on the agents{\textquoteright} estimates of the optimal solution. This provides a guide for tuning the parameters of the communication protocol such that good performance of the multi-agent subgradient method is ensured.},
	address = {Budapest, Hungary},
	booktitle = {Proceedings of the19th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2010)},
	pages = {pp.1-8}
}
@conference {
	title = {Architectures, Modularity and Robustness in Networked Control Systems},
	author = {Baras, John S.},
	year = {2010},
	month = {07/2010},
	address = {Leuven, Belgium},
	booktitle = {2010 IFAC International Symposium on Dynamics and Control of Process Systems}
}
@conference {
	title = {Efficient communication Infrastructures for Distributed Control and Decision Making in Networked Stochastic Systems},
	author = {Baras, John S., Hovareshti, Pedram.},
	year = {2010},
	month = {07/2010},
	abstract = {In networked systems, groups of agents achieve certain objectives via interaction at local levels in a distributed manner. the performance of such systems is determined by the communication infrastructure of the network as well as the system dynamics. In this paper we study the interdependence of the communication and collaboration graphs in a networked system, in the context of a coordination control and decision making problem. Each agent has to make a decision on whether to cooperate or not in a group effort. this is modelled by two-person coordination games between neighboring agents. the payoff of each agent is computed as the sum of the agent{\textquoteright}s payoffs from each of these games. Each agent{\textquoteright}s decision on whether to collaborate or not is based on its personal understanding of its own behavioral tendencies as well as its neighbors{\textquoteright}. to account for this fact we endow the agents with a behavioral variable which indicates how risk averse each agent is. The effect of the agents on each other is governed by an influence matrix which is partially derived from the communication graph{\textquoteright}s topology. This paper focuses on three major issues: The learning algorithm, the effect of communication network topology on the fast convergence of the scheme, the characterization of the effect of the number of like- minded agents and their well-connectedness as major decisive factors on which equilibrium is attained.},
	address = {Budapest, Hungary},
	booktitle = {The 19th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2010)},
	pages = {pp. 1-6}
}
@conference {
	title = {Tuning the TCP Timeout Mechanism in Wireless Networks to Maximize Throughput via Stochastic Stopping Time Methods},
	author = {Papageorgiou, George., Baras, John S.},
	year = {2010},
	month = {07/2010},
	abstract = {We present an optimization problem that aims to maximize the throughput of a Transmission Control Protocol (TCP) connection between two nodes in a wireless adhoc network. More specifically, we focus on a persistent TCP connection between two nodes that are one hop away in a wireless unslotted Aloha network. The optimization is over the TCP timeout period, i.e. the problem is to find the optimal waiting period before the TCP sender declares a timeout event in the absence of a received acknowledgement for a transmitted packet. The problem is formulated as an optimal stochastic stopping time problem. In the absence of a tractable analytical solution to the problem, a numerical method based on dynamic programming is used instead. We verify the performance increase by comparing our solution to the standard TCP timeout mechanism using simulations for a range of values of the involved parameters.},
	address = {Budapest, Hungary},
	booktitle = {The 19th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2010)},
	pages = {pp. 1539-1545}
}
@conference {
	title = {Local Pruning for Information Dissemination for the Idempotent Semiring Algebraic Path Problem},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2010},
	month = {07/2010},
	abstract = {The advent of pervasive mobile devices has created the need for new algorithm design mechanisms for mobile computing platforms. The limited capabilities of these mobile devices have created several interesting problems that do not exist in traditional networks. These limitations have made communication an expensive commodity for distributed algorithms. In this paper, we consider the communicationintensive information broadcast problem for distributed computation. In distributed computing, several different computations can be viewed from a common viewpoint as instances of the Semiring Algebraic Path Problem (SAPP) on graphs. We first show that many algorithms broadcast information to enable recomputation of the SAPP on a dynamic graph. We then develop a general theory of local pruning for the SAPP problem for idempotent semirings. We motivate the pruning problem as a multi-agent optimization problem, where the agents try to limit the amount of information they broadcast while ensuring that the broadcast is sufficient to recompute the SAPP. The main contribution of this paper is establishing that this local pruning scheme chooses sufficient information to compute the original SAPP. For the dynamic SAPP, the information broadcast required to recompute the SAPP is reduced by the pruning. We also show that our solution corresponds to a local Gauss elimination solution over an extended semiring.},
	address = {Budapest, Hungary},
	booktitle = {The 19th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2010)},
	pages = {pp. 1-8}
}
@conference {
	title = {Dynamic Magic Graphs in Cooperative Networked Systems},
	author = {Baras, John S.},
	year = {2010},
	month = {07/2010},
	address = {Budapest, Hungary},
	booktitle = {The 19th International Symposium on Mathematical Theory of Networks and Systems (MTNS 2010)}
}
@conference {
	title = {Distributed Collaborative Controlled Autonomous Vehicle Systems over Wireless Networks},
	author = {Chen, Hua., Hovareshti, Pedram., Baras, John S.},
	year = {2010},
	month = {06/2010},
	abstract = {Inspired by military tactical, civil help-and-rescue applications, it is desirable yet challenging to develop networked systems of autonomous vehicles and sensors in dynamic, resource-constrained and adversarial environments. An essential aspect of designing such collaborative systems is to address the communication needs of the vehicles in order to perform a given mission. The vehicles{\textquoteright} communication network should maintain a connectivity pattern based on the requirements of the mission. In this paper, we consider both the control and communication aspects for coordinated path planning of a group of autonomous vehicles in an adversarial environment. We propose distributed algorithms to control the vehicles{\textquoteright} trajectories over a wireless vehicle-to-vehicle network. Distributed control algorithms both with and without collaboration between the vehicles are presented. We study the performance of the wireless network over the distributed controlled autonomous vehicles. Simulation results show that collaboration between vehicles results in better performance for path planning and wireless inter-vehicle communications. However, contention based communication protocols are likely to fail due to severe channel conditions.},
	address = {Marrakech, Morocco},
	booktitle = {18th Mediterranean Conference onControl and Automation (MED 2010)},
	pages = {pp. 1695-1700}
}
@conference {
	title = {Security and Trust in Communication and Social Networks},
	author = {Baras, John S.},
	year = {2010},
	month = {06/2010},
	address = {Al Ain, UAE},
	organization = {United Arab Emirates University}
}
@conference {
	title = {Modeling Air Traffic Throughput and Delay with Network Cell Transmission Model},
	author = {Nguyen, Alex T., Baras, John S.},
	year = {2010},
	month = {05/2010},
	abstract = {In practice, the model is envisioned to initially run offline to determine a preliminary solution to the initial state of the system. Solutions for subsequent changes in actual state can be determined by running the model online for the incremental state change. Stochastic events such as convective weather clearing times or capacities can be included in the model to better see the benefits and impacts of pre-positioning traffic to take advantage of possible future clearing.},
	address = {Herndon, VA},
	booktitle = { Integrated Communications Navigation and Surveillance Conference (ICNS 2010)},
	pages = {pp. 1-14}
}
@conference {
	title = {A Systems Biology Approach to Understanding Alzheimer{\textquoteright}s Disease},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2010},
	month = {04/2010},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is the most prevalent form of dementia affecting the elderly. AD has devastating effects on the individual, leading to neuronal and synaptic loss, neuroinflammation, dysfunction of the blood-brain barrier and deposition of amyloid beta plaques in the brain parenchyma and cerebral blood vessels. Due to the inherent difficulty studying the many possible initiating factors of AD with in vivo models, we have chosen to approach this problem from a quantitative perspective initially to determine what key factors may initiate AD pathogenesis. We have developed a multi-scale systems biology model that describes the interactions between different components of the brain{\textquoteright}s biological network at the tissue, cellular and transcriptional levels. Neurons have been modeled using a modified McCulloch-Pitts neural network that accounts for cell death and synapse loss due to varying amyloid beta and cholesterol levels. Microglia have been modeled in both the ramified and activated states using the Langevin equations of motion. The spatial-temporal distribution of beta amyloid has been modeled using the convection-reaction-diffusion equation with stochastic generation rates. Transport of beta amyloid by LRP-1 across the blood-brain barrier has also been modeled. Future generations of the model will take into account experimental results, as well as include models for plaque development in the basement membrane of cerebral blood vessels.},
	address = {College Park, Maryland},
	booktitle = {2010 Southern Biomedical Engineering Conference},
	organization = {University of Maryland}
}
@conference {
	title = {Convergence Results for Ant Routing Algorithms via Stochastic Approximation and Optimization},
	author = {Purkayastha, Punyaslok., Baras, John S.},
	year = {2010},
	month = {04/2010},
	abstract = {In this paper, we provide convergence results for an Ant Routing (ARA) Algorithm for wireline, packet switched communication networks, that are acyclic. Such algorithms are inspired by the foraging behavior of ants in nature. We consider an ARA algorithm proposed by Bean and Costa [2]. The algorithm has the virtues of being adaptive and distributed, and can provide a multipath routing solution. We consider a scenario where there are multiple incoming data traffic streams that are to be routed to their destinations via the network. Ant packets, which are nothing but probe packets, are used to estimate the path delays in the network. The node routing tables, which consist of routing probabilities for the outgoing links, are updated based on these delay estimates. In contrast to the available analytical studies in the literature, the link delays in our model are stochastic, time-varying, and dependent on the link traffic. The evolution of the delay estimates and the routing probabilities are described by a set of stochastic iterative equations. In doing so, we take into account the distributed and asynchronous nature of the algorithm operation. Using methods from the theory of stochastic approximations, we show that the evolution of the delay estimates can be closely tracked by a deterministic ODE (Ordinary Differential Equation) system, when the step-size of the delay estimation scheme is small. We study the equilibrium behavior of the ODE in order to obtain the equilibrium behavior of the algorithm. We also provide illustrative simulation results.},
	address = {Stockholm, Sweden},
	booktitle = {Proceddings of the 13th International Conference on Hybrid Systems: Computation and Control (HSCC {\textquoteright}10)},
	pages = {pp. 201-210}
}
@conference {
	title = {A Trust Based Distributed Kalman Filtering Approach for Mode Estimation in Power Systems},
	author = {Jiang, Tao., Matei, Ion., Baras, John S.},
	year = {2010},
	month = {04/2010},
	abstract = {We consider distributed mode estimation in power systems. The measurements are observed by PMUs (Power Management Units). We introduce a novel model of trust, using weights on the graph links and nodes that represent the networked PMUs. We describe two algorithms that intergarte distributed Kalman filtering with these trust weights. We consider two interpretations of these trust weights as information accuracy and reliability. We show that by appropriate use of these weights from the distributed estimation algorithm avoids using information from untrusted PMUs. Simulation experiments further demonstrate the behavior of these algorithms.},
	address = {Stockholm, Sweden},
	booktitle = {First Workshop on Secure Control Systems (SCS) as part of CPSWeek 2010},
	pages = {pp. 1-6}
}
@conference {
	title = {Compositional Framework for System Security with Multi-metric Optimization"},
	author = {Baras, John S., Jiang, Tao., Somasundaram, Kiran K., Ivanov, Vladimir I.},
	year = {2010},
	month = {03/2010},
	abstract = {The objective of the proposed research is to develop a compositional framework and methods for~performance vs security tradeoffs via multi-criteria optimization of system security, and therefore it aligns~with problem statement 2: {\textquotedblleft}Security Framework.{\textquotedblright} We propose to study a top-down approach ~for~optimizing (1) the security metric(s) of a composite system viewed as a bivariate function of its~subsystems{\textquoteright} security and performance metrics under given constraints and (2) the composition of~subsystems that provides higher system security than that of the composition of the same subsystems~driven solely by performance maximization. In this way, we reconcile the trade-off between security and~performance by introducing a holistic, multi-objective solution that satisfies both the performance and the~security requirements for the system, by overcoming the problem of compartmentalized security solutions~and thus achieving the {\textquotedblleft}best value{\textquotedblright} of the system. Our framework delineates methods for achieving~provably secure composition of secure subsystems and system components {\textendash} a critical problem area~where almost all current results demonstrate infeasibility of achieving compositional security.},
	address = {Washington DC},
	booktitle = {SERC Security Workshop}
}
@conference {
	title = {Systems Engineering Challenges for Design and Realtime Management of Component-Enabled Wireless Ad-hoc Networks},
	author = {Austin, Mark A., Tabatabaee, Vahid., Baras, John S.},
	year = {2010},
	month = {03/2010},
	abstract = {This paper describes systems engineering challenges for the systematic design and realtime management of component-enabled wireless ad-hoc networks. At the front end of development, emphasis is placed on the use of goals and scenarios, and visual modelling abstractions for elicitation of models for required functionality. We assume that network nodes will be implemented as hierarchies of interconnected sub-components. To maximise system reliability and simplify technology upgrades we advocate the use of formal approaches to component interface definition, and to validation of component and system-level functionalities.},
	address = {Hoboken, NJ},
	booktitle = {Proceedings of the 8th Conference on Systems Engineering Research (CSER 2010)},
	pages = {pp. 1-10}
}
@conference {
	title = {A Mathematical Model for Alzheimer{\textquoteright}s disease},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2010},
	month = {02/2010},
	abstract = {A mathematical model for Alzheimer{\textquoteright}s disease (AD) has been developed using a systems biology approach. A cellular network of neurons, microglia and astrocytes has been created to model the levels of Aβ in the brain. The production and spatial distribution of beta amyloid (Aβ), the key protein implicated in AD, has been modeled using the reaction-diffusion equation, where reaction rates have been modeled using stochastic functions. Neurons have been modeled using a previously developed McCulloch-Pitts neural network (Butz 2006) modified to account for neuronal cell death and loss of synaptic elements during high Aβ levels. Microglia are either in the ramified state (at rest) and modeled using a continuous random walk model, or in the activated state (actively moving towards a source of Aβ) and modeled using the Langevin equation of motion. Astrocytes are defined to set locations and contribute to removal of Aβ from the brain interstitial fluid. The roles that local cerebral blood flow, transport across the BBB, and local reactions play have also been modeled. Future work will look at the development of amyloid beta plaques in the cerebrovasculature and brain parenchyma, and their relationship to observed decreases in cerebral blood flow as the disease progresses.},
	address = {San Francisco, California},
	booktitle = {Proceddings of the 2010 Biophysical Society Annual Meeting}
}
@conference {
	title = {A Systems Biology Approach to Modelling Alzheimer{\textquoteright}s disease},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2010},
	month = {01/2010},
	abstract = {A mathematical model for Alzheimer{\textquoteright}s disease (AD) has been developed using a systems biology approach. A cellular network of neurons, microglia and astrocytes has been created to model the levels of Aβ in the brain. The production and spatial distribution of beta amyloid (Aβ), the key protein implicated in AD, has been modeled using the reaction-diffusion equation, where reaction rates have been modeled using stochastic functions. Neurons have been modeled using a previously developed McCulloch-Pitts neural network (Butz 2006) modified to account for neuronal cell death and loss of synaptic elements during high Aβ levels. Microglia are either in the ramified state (at rest) and modeled using a continuous random walk model, or in the activated state (actively moving towards a source of Aβ) and modeled using the Langevin equation of motion. Astrocytes are defined to set locations and contribute to removal of Aβ from the brain interstitial fluid. The roles that local cerebral blood flow, transport across the BBB, and local reactions play have also been modeled. Future work will look at the development of amyloid beta plaques in the cerebrovasculature and brain parenchyma, and their relationship to observed decreases in cerebral blood flow as the disease progresses.},
	address = {San Francisco, California},
	booktitle = {Proceedings of the Joint Math Meeting 2010}
}
@conference {
	title = {Semiring Pruning for Information Dissemination in Mobile Ad Hoc Networks},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {12/2009},
	abstract = {Link state routing mechanisms have shown good convergence behaviour with mobile hosts. Pruning methods such as those used in Optimized Link State Routing (OLSR) have showed good throughput behaviour when compared to traditional link-state approaches which suffered from broadcast storm problems. In this paper, we show that the pruning function is a fundamental component of link-state routing protocols for mobile networks. We also show that this component architecture aids in interpreting both distance vector and link-state approaches under a common framework. We develop a class of pruning methods for many of the most commonly used routing objectives and show that these pruning methods are a special case of the semiring distribution property.},
	address = {Chennai, India},
	booktitle = {Proceedings of the The First International Conference on Networks and Communications(NetCoM-2009)},
	pages = {pp. 319-325}
}
@conference {
	title = {Efficient and Robust Communication Topologies for Distributed Decision Making in Networked Systems},
	author = {Baras, John S., Hovareshti, Pedram.},
	year = {2009},
	month = {12/2009},
	abstract = {Distributed decision making in networked systems depends critically on the timely availability of critical fresh information. Performance of networked systems, from the perspective of achieving goals and objectives in a timely and efficient manner is constrained by their collaboration and communication structures and their interplay with the networked system{\textquoteright}s dynamics. In most cases achieving the system objectives requires many agent to agent communications. A reasonable measure for system robustness to communication topology change is the number of spanning trees in the graph abstraction of the communication system. We address the problem of network formation with robustness and connectivity constraints. Solutions to this problem have also applications in trust and the relationship of trust to control. We show that the general combinatorial problem can be relaxed to a convex optimization problem. We solve the special case of adding a shortcut to a given structure and provide insights for derivation of heuristics for the general case. We also analyze the small world effect in the context of abrupt increases in the number of spanning trees as a result of adding a few shortcuts to a base lattice in the Watts-Strogatz framework and thereby relate efficient topologies to small world and expander graphs.},
	address = {Shanghai, China},
	booktitle = {48th IEEE Conference on Decision and Control},
	pages = {pp. 3751-3756}
}
@conference {
	title = {Achieving Symmetric Pareto Nash Equilibria using Biased Replicator Dynamics},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {12/2009},
	abstract = {Achieving the Nash equilibria for single objective games is known to be a computationally difficult problem. However, there is a special class of equilibria called evolutionary robust equilibria which can be obtained through a special type of evolutionary dynamics called the replicator dynamics. These dynamics has special properties over the simplex, which has been studied in optimization theory to solve several combinatorial problems. In this work, we consider the essentially hard combinatorial optimization problem of computing the equilibria in games with multiple objectives. We extend the notion of replicator dynamics to handle such games. We establish proofs of dynamic stability of this modified replicator dynamics and present their relation to the Pareto Nash equilibria in multiobjective games.},
	address = {Shanghai, China},
	booktitle = {48th IEEE Conference on Decision and Control},
	pages = {pp.7000 - 7005}
}
@conference {
	title = {Context-Dependent Multi-class Classification with Unknown Observation and Class Distributions with Applications to Bioinformatics},
	author = {Baras, A. S., Baras, John S.},
	year = {2009},
	month = {12/2009},
	abstract = {We consider the multi-class classification problem, based on vector observation sequences, where the conditional (given class observations) probability distributions for each class as well as the unconditional probability distribution of the observations are unknown. We develop a novel formulation that combines training with the quality of classification that can be obtained using the learned (via training) models. The parametric models we use are finite mixture models, where the same component densities are used in the model for each class, albeit with different mixture weights. Thus we use a model known as All-Class-One-Network (ACON) model in the neural network literature. We argue why this is a more appropriate model for context-dependent classification, as is common in bioinformatics. We derive rigorously the solution to this joint optimization problem. A key step in our approach is to consider a tight (provably) bound between the average Bayes error (the true minimal classification error) and the average model-based classification error. We rigorously show that the parameter estimates maximize the likelihood of the model-based class posterior probability distributions. We illustrate by application examples in the bioinformatics of cancer.},
	address = {Shanghai, China},
	booktitle = {48th IEEE Conference on Decision and Control},
	pages = {pp. 8523-8530}
}
@conference {
	title = {The Institute for Systems Research: the longest sustained ERC ~ 25 yrs},
	author = {Baras, John S.},
	year = {2009},
	month = {12/2009},
	address = {Bethesda, Maryland},
	booktitle = {NSF ERC Annual Meeting}
}
@conference {
	title = {Trust and Reputation in Networked Systems: Social, Information, Communication, Control},
	author = {Baras, John S.},
	year = {2009},
	month = {11/2009},
	address = {Irvine, CA},
	booktitle = {Networked Systems Seminar},
	organization = {University of California, Irvine}
}
@conference {
	title = {System Architecture and Component Based System Synthesis},
	author = {Baras, John S.},
	year = {2009},
	month = {11/2009},
	address = {Shanghai, China}
}
@conference {
	title = {Collaboration in Networks of Autonomous Agents: Coalitional Games, Constraints and Architectures},
	author = {Baras, John S.},
	year = {2009},
	month = {11/2009},
	address = {New Haven, CT},
	booktitle = {Workshop on Frontiers in Distributed Communication, Sensing and Control},
	organization = {Yale University}
}
@conference {
	title = {Network Cell Routing Model For Control of Throughput and Delay of Air Traffic},
	author = {Nguyen, Alex T., Baras, John S.},
	year = {2009},
	month = {10/2009},
	abstract = {Attempts to manage air traffic by either decreasing delay or increasing flow can have the reverse effect on the other. In the National Airspace System (NAS), flights typically depart at their chosen times, and flow management techniques are implemented in the air in an effort to maximize flow, which could lead to delay for individual aircraft. Other areas of the world allow flights to depart only at predetermined slot times knowing that there is a clear unobstructed path, leading to minimal delays but possibly under utilizing airspace. We propose a new approach in leveraging the highway cell transmission model (CTM) to the airspace in the form of a multi-objective optimization that trades between maximizing throughput and minimizing delay. The model is posed as a multi commodity traffic flow integer program where the constraints are relaxed slightly from the CTM to examine strategies for achieving optimal throughput and delay. In practice, the model is envisioned to initially run offline to determine a preliminary solution to the initial state of the system. Solutions for subsequent changes in actual state can be determined by running the model online for the incremental state change. Stochastic events such as convective weather clearing times or capacities can be included in the model to better see the benefits and impacts of pre-positioning traffic to take advantage of possible future clearing.},
	address = {Orlando, FL},
	booktitle = {28th Digital Avionics Systems Conference (DASC - 2009)},
	pages = {pp. 2.B.2-1 - 2.B.2-6}
}
@conference {
	title = {Modeling and Sensitivity Analysis of Reservation Based USAP Unicast Traffic in MANETs},
	author = {Perumal, Senni., Tabatabaee, Vahid., Baras, John S., Graff, Charles J., Yee, David G.},
	year = {2009},
	month = {10/2009},
	abstract = {In this paper, we develop and evaluate models to estimate and optimize various performance metrics for unicast traffic using the hard scheduling (virtual circuit connection oriented) mode of the reservation-based protocol USAP in mobile ad-hoc wireless networks (MANETs). USAP (Unifying Slot Assignment Protocol) is a dynamic distributed resource allocation protocol for MANETs. We model USAP hard scheduling mode using loss network models along with reduced link capacity that couple physical, MAC and routing layers effects. The key effect of multiuser interference on a link is modeled via reduced link capacity where the effects of transmissions and receptions in the link neighborhood are modeled using USAP reservation rules. We compare our results with simulation and obtain good results using our loss network models but with reduced link capacity distribution obtained by simulation. We also compute the throughput sensitivities with respect to network parameters and use these sensitivities to improve network performance.},
	address = {Boston, Massachusetts},
	booktitle = {MILCOM 2009 "The Challenge of Convergence"},
	pages = {pp.1-7}
}
@conference {
	title = {Component Based Modeling for Cross-layer Analysis of 802.11 MAC and OLSR Routing Protocols in Ad-hoc Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Jain, Kaustubh.},
	year = {2009},
	month = {10/2009},
	abstract = {We present a complete scenario driven component based analytic model of 802.11 MAC and OLSR routing protocols in MANETs. We use this model to provide a systematic approach to study the network performance and cross-layer analysis and design of routing, scheduling, MAC, and PHY layer protocols. The routing protocol is divided into multiple components. Componentization is a standard methodology for analysis and synthesis of complex systems. To provide a component based design methodology, we have to develop a component based model of the wireless network that considers cross-layer dependency of performance. The component based model enables us to study the effect of each component on the overall performance of the wireless network and to design each component separately. For the MAC layer, we use a fixed point loss model of 802.11 protocol that considers effects of hidden nodes and finite retransmission attempts. We have also considered simple models for PHY and scheduling. The main focus of this paper is on the integration of these models to obtain a complete model for wireless networks. In several scenario driven studies, with user-specified topologies and traffic demands, we study the performance metrics - throughput and delay. By analyzing the performances under varying network scenarios, we are able to identify a few sources of performance degradation. We also study the effect of certain design parameters on the network performance. Thus, demonstrating the ability of the model to quickly identify problem components and try alternative design parameters},
	address = {Boston, Massachusetts},
	booktitle = {MILCOM 2009 \&quot;The Challenge of Convergence\&quot;},
	pages = {pp. 1-7}
}
@conference {
	title = {Securing the Communication of Medical Information Using Local Biometric Authentication and Commercial Wireless Links},
	author = {Ivanov, Vladimir I., Yu, Paul L., Baras, John S.},
	year = {2009},
	month = {10/2009},
	abstract = {Medical information is extremely sensitive in nature  a compromise, such as eavesdropping or tampering by a malicious third party, may result in identity theft, incorrect diagnosis and treatment, and even death. Therefore, it is important to secure the transfer of the medical information from its source, i.e., the patient, to the system that collects and records it or its technology adoption will face a strong resistance from the users. We consider the scenario where a patient has a portable, wireless medical device that transfers the medical information to a remote server. We decompose this problem into two sub-problems and propose security solutions to each of them: (a) to secure the link between the patient and the portable device, and (b) to secure the link between the portable device and the network. Thus, we push the limits of the network security to the cutting edge: authenticating the user using their biometric information, authenticating the device to the network at the physical layer, and strengthening the security of the wireless link with a key exchange mechanism. The proposed authentication methods can be used for recording the readings of medical data in a central database and for accessing medical records.},
	address = {Kalmar, Sweden},
	booktitle = {International Symposium on Health Information Management Research (ISHIMR 2009)},
	pages = {pp.119-127}
}
@conference {
	title = {Network Cell Air Traffic Routing Model For Control of Throughput and Delay},
	author = {Nguyen, Alex T., Baras, John S.},
	year = {2009},
	month = {10/2009},
	abstract = {Attempts to manage air traffic by either decreasing delay or increasing flow can have the reverse effect on the other. In the National Airspace System (NAS), flights typically depart at their chosen times, and flow management techniques are implemented in the air in an effort to maximize flow, which could lead to delay for individual aircraft. Other areas of the world allow flights to depart only at predetermined slot times knowing that there is a clear unobstructed path, leading to minimal delays but possibly underutilizing airspace. We propose a new approach in leveraging the highway cell transmission model (CTM) to the airspace in the form of a multi-objective optimization that trades between maximizing throughput and minimizing delay. The model is posed as a multicommodity traffic flow integer program where the constraints are relaxed slightly from the CTM to examine strategies for achieving optimal throughput and delay. In practice, the model is envisioned to initially run offline to determine a preliminary solution to the initial state of the system. Solutions for subsequent changes in actual state can be determined by running the model online for the incremental state change. Stochastic events such as convective weather clearing times or capacities can be included in the model to better see the benefits and impacts of pre-positioning traffic to take advantage of possible future clearing.},
	address = {San Diego, CA},
	booktitle = {INFORMS 2009},
	pages = {2.B.2-1 - 2.B.2-6}
}
@conference {
	title = {Dynamic Self-Organization and Clustering in Distributed Networked Systems for Performance Improvement},
	author = {Baras, John S., Hovareshti, Pedram., Perumal, Senni.},
	year = {2009},
	month = {09/2009},
	abstract = {We consider two closely related dynamic self-organization problems in networked control systems. Both are forms of the~dynamic clustering of nodes. The structure of networked control systems is often abstracted using graph theory. In this abstraction, the nodes of the graph represent the agents and the edges between them represent the relation(s) or the possibility of communication between the corresponding agents. The topology of the communication network supporting a networked control system has critical consequences for its performance. The first problem we address is the development of a distributed self-organization algorithm, resulting into a dynamic two level hierarchy of leader and regular agents, which substantially improves the convergence speed of distributed algorithms utilized by the networked control system. For the second problem, we consider the collaborative control of a group of autonomous mobile agents (e.g. vehicles, robots) supported by a mobile wireless network, consisting of many grounds and a few aerial nodes. The agents collaborate to achieve a common goal or objective, like to move in a particular area and cover it, while avoiding obstacles and collisions. Building upon our earlier work on deterministic, randomized and hybrid distributed coordination algorithms we consider the communication needs of the agents, and in particular, the connectivity of their communication network as they move. We develop distributed algorithms that automatically select some agents and move them appropriately so as to maintain a~certain degree of desired connectivity among the moving agents. We characterize the trade-off between the gain from maintaining a certain degree of connectivity vs. the combined cost of communications and the associated dynamic re-positioning of agents. We also describe classes of efficient communication topologies and in particular their similarity to dynamic small-world topologies and extensions.},
	address = {Montecello, Illinois},
	booktitle = {Forty-Seventh Annual Allerton Conference on Communication, Control, and Computing (Allerton Conference 2009)},
	pages = {pp. 968-975},
	organization = {University of Illinois at Urbana-Champaign}
}
@conference {
	title = {Rate-Control System with Heterogeneous Time-varying Delays in Broadband Satellite Networks},
	author = {Zeng, Hui., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2009},
	month = {09/2009},
	abstract = {In a broadband satellite communications network, the propagation delays are not only significant, but also variable among users due to their different geographical locations and the problem becomes more severe with increasing data rates. We consider rate control algorithms with user feedback in the form of single bits and formulate analytic fluid flow models composed of first-order delay differential equations. Both single-flow and multi-flow system models are analyzed, with special attention paid to the Mitra-Seery algorithm. The stationary solutions are investigated first. For the fluctuating solutions, their dynamic behavior is analyzed, in terms of amplitude, transient behavior, fairness, and adaptability, etc., analytically and numerically. Especially the effects of heterogeneous time-varying delays are investigated. It is shown that with proper parameter design the system can achieve stabling behavior with close to pointwise proportional fairness among flows.},
	address = {Sardinia, Italy},
	booktitle = {The Ka and Broadband Communications Conference Navigation and Earth Observation Conference 2009 (KaConf2009)},
	pages = {pp. 1-8},
	organization = {Cagliari}
}
@conference {
	title = {Probabilistic Non-Repudiation for Source Authentication with TESLA Certificates in Hybrid Satellite/Wireless and Performance Analysis of the Authentication Protocol},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2009},
	month = {09/2009},
	abstract = {In this work, we describe a novel non-repudiation mechanism for an authentication protocol based on the extended TESLA certificate construct. With the non-repudiation mechanism, the authentication protocol is ideally suited for source authentication of low-powered nodes that participate in group communication in hybrid satellite/wireless networks. Security is a necessary parameter in hybrid wireless networks (consisting of groups of terrestrial wireless nodes interconnected by a satellite overlay) if the communication between a pair of nodes, or amongst a group of nodes, is to be protected from unauthorized The focus of our research work is on user authentication and message integrity protocols, which are required to enable communications and ensure that messages between communicating nodes are correctly delivered. This is a non-trivial problem in group communication, where authentication has been traditionally done using asymmetric cryptographic techniques such as public key certificates and digital signatures. However, such asymmetric techniques can be very expensive in terms of processing power and node energy for wireless nodes in hybrid networks. As a solution to this problem, we have proposed a new class of lightweight, symmetric key certificates called extended TESLA certificates, and we have designed an energy-efficient source authentication protocol for group communication that utilizes the infrastructure present in hybrid satellite networks. In our authentication protocol based on the extended TESLA certificate, we propose to add non-repudiation by taking advantage of the satellite infrastructure and the proposed mechanism of key disclosure by proxy. This is a major improvement over previous authentication algorithms based on TESLA, which does not provide for non-repudiation due to the symmetric nature of the underlying cryptographic primitive, Message Authentication Codes. In this paper, we describe the mechanism by which non-repudiation is achieved in our authentication protocol. The non-repudiation is probabilistic in nature, and we analyze the tradeoff between the degree of non-repudiation and the overhead due to the additional information necessary for non-repudiation. Furthermore, through simulations, we compare the performance between the basic authentication protocol and authentication with non-repudiation, and also compare the latter to public key-based schemes.},
	address = {Sardinia, Italy},
	booktitle = {The Ka and Broadband Communications Conference Navigation and Earth Observation Conference 2009 (KaConf2009)},
	pages = {pp.1-8},
	organization = {Cagliari}
}
@conference {
	title = {Event Triggered Distributed Collaborative Control},
	author = {Baras, John S., Hovareshti, Pedram., Perumal, Senni.},
	year = {2009},
	month = {08/2009},
	abstract = {We consider the collaborative control of a group of autonomous mobile agents (e.g. vehicles, robots). The agents collaborate to achieve a common goal or objective, like to move in a particular area and cover it, while avoiding obstacles and collisions. Building upon our earlier work on deterministic, randomized and hybrid distributed coordination algorithms we consider the communication needs of the agents, and in particular, the connectivity of their communication network as they move. We develop algorithms that automatically sense the possibility or inset of loss of connectivity among the agents. We also consider the automatic detection of path disconnection when more than one paths need to be maintained between pairs of agents. Using local probing schemes we formulate such problems as event-triggered control problems. We develop distributed algorithms that automatically select some agents and move them appropriately so as to maintain a~certain degree of desired connectivity among the moving agents. We characterize the trade-off between the gain from maintaining a certain degree of connectivity vs the combined cost of communications and the associated dynamic re-positioning of agents. The results illustrate the efficiency achieved by the~event-triggered control in such problems. We also describe the resulting communication topologies and in particular their similarity to dynamic small-world topologies.},
	address = {Budapest, Hungary},
	booktitle = {European Control Conference 2009 (ECC {\textquoteright}09)},
	pages = {pp.3797-3802}
}
@conference {
	title = {Coalition Formation and Trust in Collaborative Control},
	author = {Baras, John S., Jiang, Tao., Hovareshti, Pedram.},
	year = {2009},
	month = {08/2009},
	abstract = {We consider the collaboration of autonomous agents as a coalitional game subject to constraints, like communication, trust or reputation. We analyze the tradeoff between the benefits of collaboration and these constraints (or costs of collaboration) via dynamic, iterative stochastic games. The agents can observe locally the actions of other agents in their neighborhood and decide whether to collaborate or not in a distributed asynchronous manner. Trust values are taken into consideration when agents act and collaborate. Specifically they affect the selection of agents to collaborate with. We consider only problems where the information used for either estimating reputations or deciding on strategies is mostly local; i.e. from the neighbors of each agent. We show that randomized algorithms emerge as the agents try to reach the maximum payoff. We also investigate the topology of the formed network by studying the second largest eigenvalue of the corresponding graph, and describe its effects on control performance.},
	address = {Budapest, Hungary},
	booktitle = {European Control Conference 2009 (ECC {\textquoteright}09)},
	pages = {pp.1197-1202}
}
@conference {
	title = {Forward Looking Panel Discussion},
	author = {Baras, John S.},
	year = {2009},
	month = {07/2009},
	address = {Denver, Colorado},
	booktitle = {2009 SIAM Conference on Control and its Applications}
}
@conference {
	title = {Performance Improvements in Distributed Estimation and Fusion Induced by a Trusted Core},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {07/2009},
	abstract = {We consider distributed state estimation and fusion in autonomic ad-hoc sensor networks when some nodes are untrusted, corrupted or malicious. We provide rigorous graph models to capture both trust and network functionality relations. We propose a novel hierarchical scheme, inspired from socio-cognitive dynamics in economics and sociology, that utilizes a trusted core. We provide a component-based architecture to show the interplay between the trust and estimation schemes. As an explanatory example we consider the problem of distributed Kalman filtering. We show that trust-based schemes, implemented by a trusted core, result in significant improvement in the state estimation procedure. We also find that the interplay between estimation and trust updates quickly isolates malicious nodes and helps the observation limited nodes (corrupted sensor nodes).},
	address = {Seattle, WA},
	booktitle = {12th International Conference on Information Fusion (Fusion 2009)},
	pages = {pp. 1942-1949}
}
@conference {
	title = {Efficient Connectivity Topologies for Networked Control Systems},
	author = {Baras, John S.},
	year = {2009},
	month = {07/2009},
	abstract = {This paper presents a perceptually optimized joint source/channel coding scheme for video transmission over satellite broadcast channel. We express the end-to-end expected distortion in terms of the source coder distortion and the channel distortion. Perceptual distortion model just-noticeable-distortion (JND) is applied to improve the subjective quality of compressed video. 3-D wavelet video codec that is jointly optimized with channel codec can remove spatial and temporal redundancy and provide the scalability of video quality for broadcast channel. In order to conceal the errors under bad channel conditions and prevent the error propagation of arithmetic decoding, slicing method and a channel coding scenario that combines RCPC, Reed-Solomon codes and CRC are proposed. Two perceptual distortion indices based on JND are discussed. These two indices are combined in our joint source/channel coding scenario to achieve minimal bandwidth consumption subject to acceptable visual quality under normal and bad channel conditions. Computer simulation is conducted at difference signal-to-noise ratios (SNR). Our system uses offset QPSK (OQPSK) modulation scheme to combat the nonlinear effect of satellite channels. Acknowledgment: Research supported by the Communications and Networks Consortium sponsored by the U. S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011, and by the ARO MAASCOM MURI, grant W911NF-08-1-0238.},
	address = {Denver, Colorado},
	booktitle = {SIAM Conference on Control \& Its Applications (CT09)}
}
@conference {
	title = {Dynamic Distributed Control over Semirings and Applications},
	author = {Baras, John S.},
	year = {2009},
	month = {07/2009},
	abstract = {We demonstrate that many constrained dynamic control problems involving hybrid systems are control problems for dynamical systems over partially ordered semirings. Applications include biological-social-communication networks, collaborative robotics, consensus, flocking, trust, swarms. We next show that when time is discrete and inputs, outputs and states take values in finite sets, these problems are equivalent to constrained shortest path problems. We then develop algorithms, mostly distributed ones, for solving these dynamic constrained shortest path problems over semirings.},
	address = {Denver, Colorado},
	booktitle = {SIAM Conference on Control and its Applications (CT09)}
}
@conference {
	title = {A Composite Trust Model and its Application to Collaborative Distributed Information Fusion},
	author = {Matei, Ion., Baras, John S., Jiang, Tao.},
	year = {2009},
	month = {07/2009},
	abstract = {We consider distributed state estimation of~linear dynamic systems, observed by various sensors, as a problem in information fusion. We introduce a novel model of trust, using weights on the graph links and nodes that represent the sensor network. These weights can represent several interpretations of trustworthiness in sensor networks. We describe three algorithms that integrate distributed Kalman filtering with these trust weights. We consider two interpretations of these trust weights as information accuracy and reliability. We show that by appropriate use of these weights the distributed estimation algorithm avoids using information from untrusted sensors. Simulation experiments further demonstrate the behavior of these algorithms.},
	address = {Seattle, WA},
	booktitle = {12th International Conference on Information Fusion (Fusion 2009)},
	pages = {pp. 1950-1957}
}
@conference {
	title = {Evolutionary Dynamics of Collaborative Environments with Heterogenous Agents},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {06/2009},
	abstract = {The seminal work of Maynard Prince and Price in 1973 laid the foundations in establishing the concepts of evolutionarily stable game strategies. It attempts to select strategies which are robust to evolutionary selection pressures. We observe that most of the literature as evolved is concentrated on single objective games. In this work, we extend the notion of evolutionary stability to games with vector payoff functions. We illustrate by examples that this notion of Multicriteria evolutionary stability models a much larger class of interactions in social, economic and biological problems. Particular applications of interest are in autonomic wireless sensor networks and autonomic networked control systems. We present a multi-population replicator dynamics, which models the evolution of agent actions in a network with varying levels of selfishness. We observe this model clearly demarks the regions of co-operation among these selfish agents. We provide analytical results on the dynamic stability of the replication. This clearly characterizes the aforementioned demarcations.},
	address = {Thessaloniki, Greece},
	booktitle = {17th Mediterranean Conference on Control \&amp; Automation (MED 09)},
	pages = {pp 121-125}
}
@conference {
	title = {Performance-aware Security of Unicast Communication in Hybrid Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2009},
	month = {06/2009},
	abstract = {In this work, we address the performance problems that arise when unicast security protocols IPSEC and SSL are applied for securing the end-to-end communication in hybrid satellite networks. Satellite networks use TCP and HTTP performance-enhancing proxy servers to overcome the adverse
effect of the large delay-bandwidth product of the satellite channel. However, the proxy servers cannot function when IPSEC and SSL are used for secure unicast communication in hybrid satellite networks. We, therefore, propose the use of the Layered IPSEC (LES) protocol as an alternative to IPSEC for networklayer security. We describe a modification to the Internet Key Exchange protocol if dynamic key establishment is needed for
Layered IPSEC. For application-level security of web browsing with acceptable end-to-end delay, we propose the Dual-mode SSL protocol (DSSL) to be used instead of SSL. We describe how LES and DSSL protocols achieve the desired end-to-end communication security while allowing the TCP and HTTP proxy servers to function correctly. Through simulation studies, we quantify the improvement in performance that is achieved using
our proposed protocols, compared to traditional IPSEC and SSL.},
	address = {Dresden, Germany},
	booktitle = {IEEE ICC 2009 Communication and Information Systems Security Symposium},
	pages = {pp.1-6}
}
@conference {
	title = {Component Based Performance Modeling of Wireless Routing Protocols},
	author = {Baras, John S., Tabatabaee, Vahid., Purkayastha, Punyaslok., Somasundaram, Kiran K.},
	year = {2009},
	month = {06/2009},
	abstract = {We propose a component-based methodology for modelling and design of wireless routing protocols. Componentization is a standard methodology for analysis and synthesis of complex systems, or software. The feasibility of the component based design relies heavily on the compositionality property (i.e. system-level properties can be computed from properties of components). To provide a component based design methodology and to test compositionality for routing protocols, we have to develop a component-based model of the wireless network. We present the main components of the routing protocol that should be modelled and focus on three main components: neighborhood discovery, selector of topology information to disseminate, and the path selection components. For each component, we identify the inputs, outputs, and a generic methodology for modelling. Throughout the paper, we use the Optimized Link State Routing (OLSR) protocol as a case study to demonstrate the effectiveness of our approach. Using the neighborhood discovery component, we present our design methodology and design a modified enhanced version of this component, and compare its performance to the original OLSR design.},
	address = {Dresden, Germany},
	booktitle = {IEEE ICC 2009 Ad Hoc and Sensor Networking Symposium},
	pages = {pp.1-6}
}
@conference {
	title = {Consensus Problems with Directed Markovian Communication Patterns},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2009},
	month = {06/2009},
	abstract = {This paper is a continuation of our previous work and discusses the consensus problem for a network of dynamic agents with directed information flows and random switching topologies. The switching is determined by a Markov chain, each topology corresponding to a state of the Markov chain. We show that in order to achieve consensus almost surely and from any initial state, each union of graphs from the sets of graphs corresponding to the closed positive recurrent sets of states of the Markov chain must have a spanning tree. The analysis relies on tools from matrix theory, Markovian jump linear systems theory and random process theory. The distinctive feature of this work is addressing the consensus problem with {\textquotedblleft}Markovian switching{\textquotedblright} topologies.},
	address = {St. Louis, Missouri},
	booktitle = {2009 American Automatic Control Conference},
	pages = {pp.1298-1303}
}
@conference {
	title = {Swarms, Coalitional Games, Trust, and Network Topologies},
	author = {Baras, John S.},
	year = {2009},
	month = {06/2009},
	address = {Block Island, Rhode Island},
	booktitle = {3rd Workshop on Swarming in Natural and Engineering Systems}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Biological Autonomic Networks},
	author = {Baras, John S.},
	year = {2009},
	month = {06/2009},
	address = {Volos, Greece},
	booktitle = {2009 Information Theory Workshop}
}
@conference {
	title = {Effects of Network Structure on the Performance of Networked Systems},
	author = {Baras, John S.},
	year = {2009},
	month = {05/2009},
	address = {Santa Barbara, CA},
	booktitle = {Control Frontiers Workshop, in honor of Professor Petar Kokotovic},
	organization = {University of California Santa Barbara}
}
@conference {
	title = {Future of Multi-hopping: from Theory to Practice},
	author = {Baras, John S.},
	year = {2009},
	month = {05/2009},
	address = {New Orleans, Louisiana},
	booktitle = {Tenth ACM International Symposium on Mobile Ad Hoc Networking and Computing (Mobilhoc09)}
}
@conference {
	title = {Coalition Formation through Learning in Autonomic Networks},
	author = {Jiang, Tao., Baras, John S.},
	year = {2009},
	month = {05/2009},
	abstract = {Autonomic networks rely on the cooperation of participating nodes for almost all their functions. However, due to resource constraints, nodes are generally selfish and try to maximize their own benefit when participating in the network. Therefore, it is important to study mechanisms, which can be used as incentives for cooperation inside the network. In this paper, the interactions among nodes are modeled as games. A node joins a coalition if it decides to cooperate with at least one node in the coalition. The dynamics of coalition formation proceed via nodes that interact strategically and adapt their behavior to the observed behavior of others. We present conditions that the coalition formed is stable in terms of Nash stability and the core of the coalitional game.},
	address = {Istanbul, Turkey},
	booktitle = {International Conference on Game Theory for Networks (GameNets09)},
	pages = {pp.10-16}
}
@conference {
	title = {Performance Comparison of Two Sequential Change Detection Algorithms on Detection of In-band Wormholes},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2009},
	month = {03/2009},
	abstract = {This paper compares the performance of parametric and non-parametric sequential change detection algorithms for detecting in-band wormholes in wireless ad hoc networks. The algorithms considered are the non-parametric cumulative sum (NP-CUSUM) and the repeated sequential probability ratio test (R-SPRT). Theoretical performance of the two is compared using metrics that take into account the algorithms{\textquoteright} repeated nature, and the advantage of the parametric method is illustrated. On the other hand, connections between the parametric and non-parametric methods are made in the proposed worst-case adversary model, where the non-parametric method is shown to be more robust to attack strategy changes. Experimental evaluation of wormhole detection schemes based on the two algorithms is presented. This work has implications for both the theoretical understanding and practical design of wormhole detection schemes based on parametric and nonparametric change detection algorithms.},
	address = {Baltimore, MD},
	booktitle = {Conference on Information Sciences and Systems (CISS 2009)},
	pages = {pp.270-275}
}
@conference {
	title = {Constrained Coalitional Games and Network Science},
	author = {Baras, John S.},
	year = {2009},
	month = {03/2009},
	address = {Stockholm, Sweden},
	organization = {Department of Electrical Engineering, Royal Institute of Technology (KTH)}
}
@conference {
	title = {Cooperative Multi-agent Systems and {\textquotedblleft}Magical{\textquotedblright} Graphs},
	author = {Baras, John S.},
	year = {2009},
	month = {03/2009},
	address = {Ann Arbor, MI},
	booktitle = {Electrical and Computer Engineering Control Seminar},
	organization = {University of Michigan, Ann Arbor}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2009},
	month = {03/2009},
	address = {Washington DC},
	organization = {Mathe matics Department, Howard University}
}
@conference {
	title = {The Role of Trust in Collaborative and Adversarial Behavior in Networks of Autonomous Agents},
	author = {Baras, John S.},
	year = {2009},
	month = {03/2009},
	address = {Arlington, VA},
	booktitle = {AFOSR Workshop on Adversarial and Stochastic Elements in Autonomous Systems}
}
@conference {
	title = {New Algorithm for the Design of Topology Aware Hypercube in Multi-hop Ad hoc Networks},
	author = {Striki, Maria., Manousakis, Kyriakos., Baras, John S.},
	year = {2009},
	month = {03/2009},
	abstract = {Securing group communications in resource constrained, infrastructure-less environments such as Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless network security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security, on the other hand, is becoming an indispensable requirement of our modern life for all these applications. The inherent limitations of such dynamic and resource-constraint networks impose major difficulties in establishing a suitable secure group communications framework. This is even more so for the operation of Key Agreement (KA), under which all parties contribute equally to the group key. The logical design of efficient KA protocols has been the main focus of the related research to-date. Such a consideration, however, gives only a partial account on the actual performance of a KA protocol in a multi-hop network. This is because protocols have been evaluated only in terms of the group key related messaging in isolation from the underlying network functions that interact with the logical scheme and support its correct execution (i.e. routing). In recent work, we contributed towards efficiently extending a number of Diffie-Hellman (DH)-based group KA protocols in wireless multi-hop ad-hoc networks. Towards this end, we introduced a number of new algorithms to efficiently estimate the combined routing {\textendash} communication costs. We then improved these protocols with the addition of a new communication schedule subject to the underlying routing. Indeed, the resulting protocols were significantly more efficient in some or all of the metrics of interest, as our analytical and simulation results indicated. In this work, we contribute towards the latter, by extending an existing KA scheme that was left out in our previous work: Hypercube. Through our analysis and simulations, we demonstrate the superiority of the new, {\textquotedblleft}enriched{\textquotedblright} Hypercube that takes into account the underlying routing via the application of a topologically aware communications schedule.},
	address = {Gosier Guadeloupe, France},
	booktitle = {8th International Conference on Networks ICN 2009},
	pages = {pp.236-244}
}
@conference {
	title = {Autonomic Networked Information and Control Systems: The Critical Effects of Connectivity Architectures},
	author = {Baras, John S.},
	year = {2009},
	month = {02/2009},
	abstract = {We develop a unifying analytical and optimization framework for networks of autonomous agents. The fundamental view is that agents in such a network are dynamic entities that collaborate because via collaboration they can accomplish objectives and goals much better than working alone, or even accomplish objectives that they cannot achieve alone at all. Yet the benefits derived from such collaboration require some costs (or expenditures), for example due to communications. Or in equivalent terms, the collaboration is subject to constraints (static and dynamic). Understanding and quantifying this tradeoff between the benefits vs the costs of collaboration, leads to new methods that can be used to analyze, design and control/operate networks of agents. An important, yet not emphasized to-date, aspect of collaboration is the role of topologies and connectivities linking the agents. This is the main topic of this paper. We demonstrate that connectivities related to small world graphs and expander graphs offer dramatic advantages with respect to many problems that need to be solved in a distributed manner in collaborative information and control systems. These topologies are efficient from the perspective of costs yet lead to fast convergence of distributed algorithms from the benefits perspective. We show how they can be self-generated in response to cost-benefit tradeoffs. We illustrate by simple examples from communication, social and biological networks.},
	address = {San Diego, CA},
	booktitle = {2009 Workshop on Information Theory and Applications (ITA09)},
	organization = {University of California San Diego}
}
@conference {
	title = {Effects of Topology in Networked Systems: Stochastic Methods and Small Worlds},
	author = {Baras, John S., Hovareshti, Pedram.},
	year = {2008},
	month = {12/2008},
	abstract = {The topology of a networked control system has critical consequences for its performance. We provide first substantial examples on the effects of topology. Then we proceed to develop a rigorous evaluation of topology effects using stochastic methods inspired from statistical physics and Markov chains. This analysis leads us to proofs on faster convergence of distributed algorithms in networked systems for certain topologies and especially small-world topologies, which are~given an {\textquoteleft}efficiency{\textquoteright} characterization. Finally, these results lead to the development of self-organization of such systems in hierarchies that provably improve performance and response.},
	address = {Cancun, Mexico},
	booktitle = {47th IEEE Conference on Decision and Control},
	pages = {pp. 2973-2978}
}
@conference {
	title = {Average Consensus over Small World Networks: A Probabilistic Framework},
	author = {Hovareshti, Pedram., Baras, John S., Gupta, Vijay.},
	year = {2008},
	month = {12/2008},
	abstract = {It has been observed that adding a few long range edges to certain graph topologies can significantly increase the rate of convergence for consensus algorithms. A notable example is the class of ring-structured Watts-Strogatz small world graphs. Building on probabilistic methods for analyzing {\textquoteleft}small-world phenomena{\textquoteright}, developed in our earlier work, we provide here a probabilistic framework for analyzing this effect. We investigate what graph characteristics lead to such a significant improvement and develop bounds to analyze consensus problems on randomly varying graphs.},
	address = {Cancun, Mexico},
	booktitle = {47th IEEE Conference on Decision and Control},
	pages = {pp. 375-380}
}
@conference {
	title = {Almost Sure Convergence to Consensus in Markovian Random Graphs},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {12/2008},
	abstract = {In this paper, we discuss the consensus problem for a network of dynamic agents with undirected information flow and random switching topologies. The switching is determined by a Markov chain, each topology corresponding to a state of the Markov chain. We show that in order to achieve consensus almost surely and from any initial state the sets of graphs corresponding to the closed positive recurrent sets of the Markov chain must be jointly connected. The analysis relies on tools from matrix theory, Markovian jump linear systems theory and random processes theory. The distinctive feature of this work is addressing the consensus problem with {\textquotedblleft}Markovian switching{\textquotedblright} topologies.},
	address = {Cancun, Mexico},
	booktitle = {47th IEEE Conference on Decision and Control},
	pages = {pp. 3535-3540}
}
@conference {
	title = {Power Allocation Tradeoffs in Multicarrier Authentication Systems},
	author = {Yu, Paul L., Baras, John S., Sadler, Brian M.},
	year = {2008},
	month = {12/2008},
	abstract = {Physical layer authentication techniques exploit signal characteristics to identify radios. We describe how multicarrier systems may use such techniques to stealthily authenticate while maintaining high levels of security and robustness. We show that with channel state information (CSI) at the transmitter and receiver, multicarrier authentication systems can further improve performance by carefully allocating the authentication power on each carrier.},
	address = {Orlando, FL},
	booktitle = {26th Army Science Conference},
	pages = {pp.1-5}
}
@conference {
	title = {Trust Credential Distribution in Autonomic Networks},
	author = {Jiang, Tao., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {Autonomic networks are networks that are self-organized, and controlled and managed in a decentralized way. Peers/nodes in such networks rely on co-operation of each other. Thus, accurate trust establishment and maintenance is essential for secure and reliable operations in autonomic networks. Trust management in autonomic networks is a much more challenging problem than in traditional server-based networks. In traditional networks, centralized trusted servers provide necessary trust credentials for trust establishment. However, such servers are not available in autonomic networks, where trust credentials are distributed among users in the network. In this paper, we design a distributed scheme for efficiently distributing trust credentials, which requires no global information exchanges. Our scheme is inspired from network coding, where trust credentials are combined by the intermediate nodes during distribution.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {Performance Metric Sensitivity Computation for Optimization and Trade-off Analysis in Wireless Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas.},
	year = {2008},
	month = {11/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics for multihop wireless networks, including MANETs. We introduce an approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model takes into account effects of the hidden nodes, scheduling algorithms, IEEE 802.11 MAC and PHY layer transmission failures and finite packet transmission retries at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models, and develop a methodology for sensitivity analysis, parameter optimization and trade-off analysis for key wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {Aerial Platform Placement Algorithm to Satisfy Connectivity and Capacity Constraints in Wireless Ad-hoc Networks},
	author = {Perumal, Senni., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {In this paper, we address the problem of establishing full connectivity and satisfying required traffic capacity between disconnected clusters in large wireless ad-hoc ground networks by placing a minimum number of advantaged high flying Aerial Platforms (APs) as relay nodes at appropriate places. We formulate the problem of providing both connectivity and required capacity between disconnected ground clusters as a constrained clustering problem with complexity costs. The basic requirement for connectivity between the ground clusters and APs is converted into a summation form distortion function. The additional requirement for connectivity between the various APs is encoded by adding a new (summation form) constraint to the distortion function. In order to satisfy the required capacity out of each cluster to all other clusters, we add a cost function that depends on the assignment probabilities of the APs and relate~the source (prior) probabilities of each cluster to the required capacity out of this cluster. The cost function produces solutions which are load balanced, i.e., the capacities supported through each AP are nearly equal. We solve the resultant clustering problem using Deterministic Annealing in order to find (near) globally optimal solutions for the minimum number and locations of the APs to establish full connectivity and provide required traffic capacity between disconnected clusters. We establish the validity of our algorithm by comparing it with optimal exhaustive search algorithms and show that our algorithm is near-optimal for the problem of establishing connectivity and satisfying capacity requirements between disconnected clusters.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {A Lightweight Certificate-based Source Authentication Protocol for Group Communications in Hybrid Wireless/Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {In this paper, we describe an efficient authentication protocol for group communication in hybrid wireless networks with a satellite overlay. The proposed protocol uses a new class of lightweight, symmetric-key certificates called TESLA certificate. The certificates bind the identities of the senders to the anchor elements of their key chains; messages from the senders are authenticated by MACs computed with keys from the chain. The satellite is used as the Certificate Authority to generate the certificates. The satellite also acts as the proxy for the senders in disclosing the MAC keys to the receivers in the network. Due to the use of symmetric MAC functions, the proposed protocol is much less expensive in terms of node processing power and energy compared to digital signatures. The use of the satellite as the CA and the proxy allows strong security mechanisms and fast message verification. Through analysis, we show that the protocol is secure against malicious adversaries. We also estimate of the performance of the protocol in comparison to public key-based digital signatures.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-6}
}
@conference {
	title = {Intrusion Detection of In-Band Wormholes in MANETS Using Advanced Statistical Methods},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {Due to the dynamics and mobility of mobile ad hoc networks (MANETs), intrusion detection techniques in MANETs must be adaptive. In this work, we propose detection schemes that are suitable to detect in-band wormhole attacks. The first detection scheme uses the Sequential Probability Ratio Test (SPRT). The SPRT has been proven to be an optimal detection test when the probability distributions of both normal and abnormal behaviors are given. Furthermore, we introduce non-parametric methods, which require no training and are more adaptive to mobile scenarios. The proposed detection schemes are implemented and evaluated using a 48-node testbed and a mobile ad-hoc network emulator at the Army Research Lab. The performance and the~detection accuracy of various schemes are compared, especially in the presence of congestion. We provide a quantitative analysis of tradeoffs among detection latency and probabilities of false alarms and missed detection.},
	address = {San Diego, CA},
	booktitle = {Milcom: 08 Assuring Mission Success},
	pages = {pp. 1-7}
}
@conference {
	title = {Loss Network Models and Multiple Metric Performance Sensitivity Analysis for Mobile Wireless Multi-Hop Networks},
	author = {Baras, John S., Perumal, Senni., Tabatabaee, Vahid., Somasundaram, Kiran K., Purkayastha, Punyaslok.},
	year = {2008},
	month = {11/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics of mobile wireless multi-hop networks, including MANETs. The method utilizes approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model considers effects of the hidden nodes, node scheduling algorithms, MAC and PHY layer failures and unsuccessful packet transmission attempts at the MAC layer in~arbitrary time-varying network topologies where multiple paths share nodes. The method then applies Automatic Di{\textregistered}erentiation (AD) to these implicit performance models, to compute sensitivities of various performance metrics with respect to net- work parameters. We demonstrate the method by applying it to time-varying mobile network topologies, including reduced connectivity instances, with both random access MAC (contention mode of the 802.11) as well as reservation-based MAC (USAP TDMA based protocol). We analyze throughput, delay and packet loss as metrics and investigate metric optimization and tradeoff analysis. Finally, we provide numerical results for realistic mobile networks with time-varying topologies.},
	address = {Maui, Hawaii},
	booktitle = {Fourth International Wireless Internet Conference (WICON 2008)}
}
@conference {
	title = {Aerial Platform Placement Algorithms to Satisfy Connectivity, Capacity and Survivability Constraints in Wireless Ad-hoc Networks},
	author = {Perumal, Senni., Baras, John S., Graff, Charles J., Yee, David G.},
	year = {2008},
	month = {11/2008},
	abstract = {In this paper, we address the problem of establishing full connectivity and satisfying required traffic capacity between disconnected clusters in large wireless ad-hoc ground networks by placing a minimum number of advantaged high flying Aerial Platforms (APs) as relay nodes at appropriate places. We also extend the connectivity solution in order to make the network survivable to a single AP failure. The problem of providing both connectivity and required capacity between disconnected ground clusters is formulated as a summation-form clustering problem with inter-AP distance constraints that make the AP network fully connected and with complexity costs that take care of cluster to AP capacity constraints. The resultant clustering problem is solved using Deterministic Annealing to find (near) globally optimal solutions for the minimum number and locations of the APs to establish full connectivity and provide required traffic capacity between disconnected clusters. In order to make the network single AP survivable, the connectivity solution is extended so that each AP connects to at least two neighboring APs and each ground cluster connects to at least two APs. We establish the validity of our algorithms by comparing it with optimal exhaustive search algorithms and show that our algorithms are near-optimal for the problem of establishing connectivity between disconnected clusters.},
	address = {San Diego, CA},
	booktitle = {Milcom: 08 Assuring Mission Success},
	pages = {pp. 1-7}
}
@conference {
	title = {Constrained Coalitional Games and Networks for Autonomous Agents},
	author = {Baras, John S.},
	year = {2008},
	month = {10/2008},
	address = {Athens, Greece},
	booktitle = {Inter-Perf 2008: Workshop on Interdisciplinary Systems Approach in Performance Evaluation and Design of Computer \& Communication Systems}
}
@conference {
	title = {Performance Evaluation and Trade-Offs of Optimal Back-Off Misbehavior Detection Schemes in Wireless Networks in the Presence of Interference},
	author = {Radosavac, Svetlana., Baras, John S.},
	year = {2008},
	month = {10/2008},
	abstract = {In this work, we evaluate the impact of interference caused by concurrent transmissions of neighboring stations on the performance of quickest detection schemes for detection of back-off misbehavior in the IEEE 802.11 MAC. We evaluate the trade-offs that both the adversary and the detector face under such conditions using a game theoretic framework. Furthermore, we evaluate the worst-case scenarios under which the given detector can efficiently operate under the predetermined conditions and show by both mathematical analysis and simulation how the presence of uncertainty affects the performance of the detector. Finally, we conclude that in the presence of (i) adaptive intelligent adversaries and (ii) variable environment conditions, the adoption of a static detection system is not advisable and propose employment of an adaptive detection system in order to maintain satisfying performance under a wide range of conditions.},
	address = {Athens, Greece},
	booktitle = {Valuetools 2008},
	pages = {pp. 1-10}
}
@conference {
	title = {Performance Modeling of Hybrid Satellite/Wireless Networks Using Fixed Point Approximation and Sensitivity Analysis of the Performance Models for Network Design},
	author = {Roy-Chowdhury, Ayan., Tabatabaee, Vahid., Baras, John S.},
	year = {2008},
	month = {09/2008},
	abstract = {In this work, we propose a new analytical method for modeling and estimating the performance of hybrid networks that are comprised of terrestrial wireless networks interconnected by a satellite overlay. We take advantage of the natural hierarchy present in the hybrid architecture to split the network into multiple levels based on the node and link characteristics. For the lower level of terrestrial wireless nodes, we use a simple approximate (throughput) loss model that couples the physical, MAC and routing layers. The model provides quantitative statistical relations between the loss parameters used to characterize multiuser interference and physical path conditions on the one hand and traffic rates between origin-destination pairs on the other. For the higher layer consisting of the terrestrial gateway nodes interconnected by the satellite overlay, we use a simple satellite channel bit error loss model coupled with a channel access protocol, to derive a similar relationship between traffic arrival rate and the link loss. We use the technique of hierarchical~reduced loss network model, adapted for packet-switched networks, to create a reduced load network model for the hybrid network that connects the packet arrival rates in the different levels with the associated physical and link loss rates. We then apply a fixed point approximation approach for this set of relations to derive a solution that converges to a fixed point for the given set of parameters, while satisfying all the equations in the set. The result is an implicit model of the selected performance metric parameterized by the design variables. We apply the technique of Automatic Differentiation to the performance models obtained through the fixed point approximation and analyze the sensitivity of the performance metrics to variations in the selected network parameter. We thus develop a methodology for parameter optimization and sensitivity analysis of protocols to aid in the design of hybrid networks. We demonstrate the effectiveness of our approach through simulation results, compared with results from discrete event simulations on identical network topology.},
	address = {Matera, Italy},
	booktitle = {Ka and Broadband Communications Conference},
	pages = {pp. 245-253}
}
@conference {
	title = {Dynamic Network Security Deployment Under Partial Information},
	author = {Theodorakopoulos, George., Baras, John S., Le Boudec, Jean-Yves.},
	year = {2008},
	month = {09/2008},
	abstract = {A network user{\textquoteright}s decision to start and continue using security products is based on economic considerations. The cost of a security compromise (e.g., worm infection) is compared against the cost of deploying and maintaining a sufficient level of security. These costs are not necessarily the real ones, but rather the perceived costs, which depend on the amount of information available to a user at each time. Moreover, the costs (whether real or perceived) depend on the decisions of other users, too: The probability of a user getting infected depends on the security deployed by all the other users. In this paper, we combine an epidemic model for malware propagation in a network with a game theoretic model of the users{\textquoteright} decisions to deploy security or not. Users can dynamically change their decision in order to maximize their currently perceived utility. We study the equilibrium points~and their dependence on the speed of the learning process through which the users learn the state of the network. We find that the faster the learning process, the higher the total network cost.},
	address = {Monticello, IL},
	booktitle = {Forty-Sixth Annual Conference on Communication, Control and Computing},
	pages = {pp. 261-267}
}
@conference {
	title = {Multi-hop Mobile Wireless Network Design: Implicit Cross-layer Loss Models and Performance Sensitivities},
	author = {Baras, John S.},
	year = {2008},
	month = {09/2008},
	address = {San Francisco, CA},
	booktitle = {MobiCom 2008}
}
@conference {
	title = {Trust in Social, Economic, Communication and Web-based Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {08/2008},
	address = {Samos, Greece},
	booktitle = {12th Pan-Hellenic Conference on Informatics (PCI2008)}
}
@conference {
	title = {Constrained Coalitional Games and Networks of Autonomous Agents},
	author = {Baras, John S.},
	year = {2008},
	month = {08/2008},
	address = {Lund, Sweden},
	organization = {Department of Automatic Control, Lund University}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {08/2008},
	address = {Athens, Greece},
	organization = {National Technical University of Athens}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {07/2008},
	address = {Chania, Crete},
	organization = {Technical University of Crete}
}
@conference {
	title = {Physical Layer Authentication},
	author = {Baras, John S.},
	year = {2008},
	month = {07/2008},
	address = {Herakleion, Greece},
	organization = {University of Crete, Department of Electrical Engineering and FORTH Institute for Computer Science}
}
@conference {
	title = {Dynamic Trust, Reputation and Recommender Systems for Web-based Social Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {07/2008},
	address = {Patras, Greece},
	booktitle = {18th European Conference on Artificial Intelligence (ECAI{\textquoteright}08)},
	organization = {University of Patras}
}
@conference {
	title = {Optimal Linear Quadratic Regulator for Markovian Jump Linear Systems, in the Presence of One Stop-Time Step Delayed Mode Observations},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {07/2008},
	abstract = {In this paper, we provide the solution to the optimal Linear Quadratic Regulator (LQR) paradigm for Markovian Jump linear Systems, when the continuous state is available at the controller instantaneously, but the mode is available only after a delay of one-time step. This paper is the first to investigate the LQR paradigm in the presence of such mismatch between the delay in observing the mode and the continuous state at the controller. We show that the optimal LQR policy is a time-varying matrix gain multiplied by the continuous component of the state, where the gain is indexed in time by the one-step delayed mode. The solution to the LQR is expressed as a collection of coupled Riccati iterations and equations, for the finite and the infinite horizon cases respectively. In the infinite horizon case, the solution of the coupled Riccati equations or a certificate of infeasibility is obtained by solving a set of linear matrix inequalities. We also explain the difficulties of solving the LQR problem when the mode is observed by the controller with a delay of more than one step. We show that, with delays of more than one time-step, the optimal control will be a time-varying nonlinear function of the continuous state and of the control input, without presenting an exact solution.},
	address = {Seoul, Korea},
	booktitle = {17th IFAC World Congress},
	pages = {pp. 8056-8061}
}
@conference {
	title = {Main Issues in Defining and Maintaining Trust: Vision for the Future},
	author = {Baras, John S.},
	year = {2008},
	month = {06/2008},
	address = {Berlin, Germany},
	booktitle = {Future of Trust in Computing Conference}
}
@conference {
	title = {A Policy-Based Routing Scheme for Multi-Robot Systems},
	author = {Purkayastha, Punyaslok., Hovareshti, Pedram., Baras, John S.},
	year = {2008},
	month = {06/2008},
	abstract = {In this paper, we consider a policy-based routing scheme for a wireless communication network consisting of a set of robots as nodes. Our scheme provides a communication infrastructure that enables the multi-robot system to accomplish its assigned tasks. Our scheme is adaptive and can be implemented in a distributed manner by the nodes of the network. The scheme makes estimates of link and path costs in the network and uses these estimates to construct probabilistic routing tables in the nodes. We use ideas from the literature on simulation methods for approximate dynamic programming to compute, in a distributed manner, the cost estimates.We propose two schemes that update the probabilistic routing tables at the nodes of the network. One of the schemes is an adaptation of the Linear Reward Inaction rule found in studies of stochastic learning automata. Our other scheme is a modification of an Ant-Based Routing algorithm. We assume a simple model of the link behavior in the wireless network - a message transmission on a wireless link is assumed to be successful with a certain probability and is lost otherwise. We also analyze our algorithms and show that our probabilistic update schemes direct packets along paths with low costs.},
	address = {Ajaccio, France},
	booktitle = {16th Mediterranean Conference on Control and Automation},
	pages = {pp. 970-975}
}
@conference {
	title = {Multicarrier Authentication at the Physical Layer},
	author = {Yu, Paul L., Baras, John S., Sadler, Brian M.},
	year = {2008},
	month = {06/2008},
	abstract = {Authentication is the process where claims of identity are verified. Though authentication mechanisms typically exist above the physical layer, physical layer methods have recently been introduced that do not require extra bandwidth. In this paper, we propose a multi-carrier extension to the work and consider the stealth and robustness tradeoffs. We conclude by discussing the power-reliability tradeoff and the applicability to cross-layer security.},
	address = {Newport Beach, CA},
	booktitle = {IEEE Workshop on Security and Privacy in Wireless Networks (IEEE SPAWN 2008)},
	pages = {pp. 1-6}
}
@conference {
	title = {Optimal State Estimation for Discrete-Time Markovian Jump Linear Systems, in the Presence of Delayed Mode Observations},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {06/2008},
	abstract = {In this paper, we investigate an optimal state estimation problem for Markovian Jump Linear Systems. We consider that the state has two components: the first component of the state is finite-valued and is denoted as mode, while the second (continuous) component is in a finite dimensional Euclidean space. The continuous state is driven by a deterministic control input and a zero mean, white and Gaussian process noise. The observable output has two components: the first is the mode delayed by a fixed amount and the second is a linear combination of the continuous state observed in zero mean white Gaussian noise. Our paradigm is to design optimal estimators for the current state, given the current output observation. We provide a solution to this paradigm by giving a recursive estimator of the continuous state, in the minimum mean square sense, and a finitely parameterized recursive scheme for computing the probability mass function of the current mode conditional on the observed output. We show that the optimal estimator is nonlinear on the observed output and on the control input. In addition, we show that the computation complexity of our recursive schemes is an exponential function of the mode observation delay.},
	address = {Seattle, Washington},
	booktitle = {2008 Automatic Control Conference},
	pages = {pp.  3560-3565}
}
@conference {
	title = {Wireless Network Design: Implicit Loss Models, PHY Feedback, Performance Sensitivities},
	author = {Baras, John S.},
	year = {2008},
	month = {05/2008},
	address = {Los Angeles, California},
	booktitle = {USC Workshop on Wireless Networks}
}
@conference {
	title = {Optimal State Estimation for Discrete-Time Markovian Jump Linear Systems, in the Presence of Delayed Output Observations},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {05/2008},
	abstract = {In this paper, we investigate the design of optimal state estimators for Markovian Jump Linear Systems. We consider that the state has two components: the first component is finite-valued and is denoted as mode, while the second (continuous) component is in a finite dimensional Euclidean space. The continuous state is driven by a zero mean, white and Gaussian process noise. The observation output has two components: the first is the mode and the second is a linear combination of the continuous state observed and zero mean white Gaussian noise. Both output components are affected by delays, not necessarily equal. Our paradigm is to design optimal estimators for the current state, given the current output observation. We provide a solution to this paradigm by giving a recursive estimator for the continuous state, in the minimum mean square sense, and a finitely parameterized recursive scheme for computing the probability mass function of the current mode conditioned on the observed output. We show that when the mode is observed with a greater delay than the continuous output component, the optimal estimator nonlinear in the observed outputs.},
	address = {Porto, Portugal},
	booktitle = {IEEE Information Theory Workshop (ITW 2008)},
	pages = {pp. 237-242}
}
@conference {
	title = {Wireless Network and Network Protocol Design: A Components and Optimization Based Approach},
	author = {Baras, John S.},
	year = {2008},
	month = {04/2008},
	organization = {DoCoMo Labs USA}
}
@conference {
	title = {Fault-Tolerant Extension of Hypercube for Secure and Reliable Group Communications},
	author = {Striki, Maria., Baras, John S., Manousakis, Kyriakos.},
	year = {2008},
	month = {04/2008},
	abstract = {Securing group communications in resource constrained, infrastructure-less Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless networking and security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security, on the other hand, is becoming an indispensable requirement of our modern life for all these applications. The inherent limitations of MANETs impose major difficulties on establishing a suitable secure group communications framework. We contribute to the latter by extending Hypercube, an existing key agreement (KA) scheme - all parties contribute equally to the group key - to tolerate multiple member failures with low cost. We achieve this by enhancing Hypercube with a novel adaptively proactive algorithm. Members are assumed to be already authenticated via some underlying mechanism and we only focus on the design and analysis of a fault-tolerant scheme. Our algorithm has been evaluated and compared with the existing approach. Through our analysis and simulations, we demonstrate its superiority in terms of robustness and efficiency.},
	address = {Cancun, Mexico},
	booktitle = {Seventh International Conference on Networking (ICN 2008)},
	pages = {pp. 223-231}
}
@conference {
	title = {New Algorithms for the Efficient Design of Topology-Oriented Key Agreement Protocols in Multi-hop Ad Hoc Networks},
	author = {Striki, Maria., Baras, John S., Manousakis, Kyriakos.},
	year = {2008},
	month = {03/2008},
	abstract = {Securing group communications in resource constrained, infrastructure-less environments such as Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless network security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security, on the other hand, is an indispensable requirement of our modern life for all these applications. The inherent limitations of such dynamic and resource-constraint networks impose major difficulties in establishing a suitable secure group communications framework. This is even more so for the task of Key Agreement (KA), under which all parties contribute equally to the group key. The logical design of efficient KA protocols has been the main focus of the related research to-date. Such a consideration, however, gives only a partial account on the feasibility and actual performance of a KA protocol in a real multi-hop network. This is because protocols have been evaluated only in terms of the group key related messaging in isolation from the underlying network functions that interact with the logical scheme and support its correct execution (i.e. routing). In this work, we contribute towards efficiently extending a number of Diffie-Hellman (DH)-based group KA protocols in wireless multi-hop ad-hoc networks, and measuring their actual performance over these networks. Towards this end, we introduce a number of new algorithms that intelligently blend the logical protocol design with the underlying routing and network topology, to produce schemes that substantially improve on the metrics of interest. Indeed, the resulting protocols accomplish this goal, as our analytical and simulation results indicate.},
	address = {Berlin, Germany},
	booktitle = {6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt{\textquoteright}08)},
	pages = {pp. 384-393}
}
@conference {
	title = {Modelling and Optimization for Multi-hop Wireless Networks Using Fixed Point and Automatic Differentiation},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas.},
	year = {2008},
	month = {03/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics of multi-hop wireless networks, including MANETs. We introduce a simple approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model considers effects of the hidden nodes, node scheduling algorithms, MAC and PHY layer failures and unsuccessful packet transmission attempts at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models~and develop a methodology for sensitivity analysis and parameter optimization for wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.},
	address = {Berlin, Germany},
	booktitle = {6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt{\textquoteright}08)},
	pages = {pp.  295 -300}
}
@conference {
	title = {Clustering Characteristics of Millimeter Wave Indoor Channels},
	author = {Neekzad, Behnam., Sayrafian, Kamran., Baras, John S.},
	year = {2008},
	month = {03/2008},
	abstract = {Temporal-Angular channel sounding measurements of an indoor millimeter wave channel (60 GHz) is analyzed to determine whether ray arrivals at the receiver form clusters in the two-dimensional time-angle space. The channel behavior for directional antennas (with various 3dB beamwidths) at the transmitter is discussed and geometric interpretation of the results is provided.},
	address = {Las Vegas, Nevada},
	booktitle = {IEEE Wireless Communications \&amp; Networking Conference},
	pages = {pp. 1217-1222}
}
@conference {
	title = {Constrained Coalitional Games and Networks of Autonomous Agents},
	author = {Baras, John S., Jiang, Tao., Purkayastha, Punyaslok.},
	year = {2008},
	month = {03/2008},
	abstract = {We develop a unifying analytical and optimization based framework for the design, operation and performance evaluation of networks of dynamic autonomous agents. The fundamental view is that agents in such a network are dynamic entities that collaborate because via collaboration they can accomplish objectives and goals much better than working alone, or even accomplish objectives that they cannot achieve alone at all. Yet the benefits derived from such collaboration require some costs (e.g. communications), or equivalently, the collaboration is subject to constraints. Understanding and quantifying this tradeoff between the benefits vs the costs of collaboration, leads to new methods that can be used to analyze, design and control/operate networks of agents. Although the inspiration for the framework comes from social and economic networks, the fundamental ideas and in particular the methodology of dynamic constrained coalitional games (DCCG) can unify many concepts and algorithms for networks in various areas: social networks, communication networks, sensor networks, economic networks, biological networks, physics networks. We then analyze a specific instance of such tradeoffs arising in the design of security-aware network protocols. We extend network utility maximization (NUM) so as to encompass security metrics such as {\textquotedblleft}trust{\textquotedblright}. The trust values assigned to nodes are based on interaction history and community-based monitoring. The effect of these trust values on the resulting protocols is that in routing and media access scheduling node trustworthiness is automatically considered and used. We develop a distributed algorithm for the joint physical-MAC-routing protocol design. Our extension to NUM with security concerns leads to resilient networks.},
	address = {St. Julians, Malta},
	booktitle = {Third International Symposium on Communications, Control and Signal Processing},
	pages = {pp. 972-979}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {San Diego, CA},
	organization = {Department of ECE and CALIT Center, University of California San Diego}
}
@conference {
	title = {Trust and Reputation in Communication, Computer and Social Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {Sunnyvale, CA},
	organization = {Fujitsu Labs of America}
}
@conference {
	title = {Path Problems, Network Optimization and Applications to Networked Systems},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {Lausanne, Switzerland},
	organization = {Telecommunications Laboratory, EPFL}
}
@conference {
	title = {Dynamic Iterations on Partially Ordered Semirings with Applications to Trust Evaluation in Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {Lausanne, Switzerland}
}
@conference {
	title = {Sensor Scheduling using Smart Sensors},
	author = {Hovareshti, Pedram., Gupta, Vijay., Baras, John S.},
	year = {2007},
	month = {12/2007},
	abstract = {The sensor selection problem arises when multiple sensors are jointly trying to estimate a process but only a subset of them can take and/or use measurements at any time step. In a networked estimation situation, sensors are typically equipped with some memory and processing capabilities. We illustrate that utilization of these capabilities can lead to significant performance gains in the sensor selection problem for improved estimation performance. Further, it also leads to significant pruning of the search tree that yields the optimum sensor schedule. We also present a periodicity result for the case where the decision is whether the sensor should transmit or not.},
	address = {New Orleans, Louisiana},
	booktitle = {46th IEEE Conference on Decision and Control},
	pages = {pp. 494-499}
}
@conference {
	title = {Convergence Results for Ant Routing Algorithms via Stochastic Approximation and Optimization},
	author = {Purkayastha, Punyaslok., Baras, John S.},
	year = {2007},
	month = {12/2007},
	abstract = {"Ant algorithms" have been proposed to solve a variety of problems arising in optimization and distributed control. They form a subset of the larger class of {\textquotedblleft}Swarm Intelligence{\textquotedblright} algorithms. The central idea is that a {\textquoteleft}swarm{\textquoteright} of relatively simple agents can interact through simple mechanisms and collectively solve complex problems. Instances that exemplify the above idea abound in nature. The abilities of ant colonies to collectively accomplish complex tasks have served as sources of inspiration for the design of {\textquotedblleft}Ant algorithms{\textquotedblright}. Examples of {\textquotedblleft}Ant algorithms{\textquotedblright} are {\textquotedblleft}Ant Routing{\textquotedblright} algorithms that have been proposed for communication networks. We analyze in this paper an Ant-Based Routing Algorithm for packet-switched wireline networks. The algorithm is an attractive multiple path probabilistic routing scheme, that is fully adaptive and distributed. Using methods from adaptive algorithms and stochastic approximation, we show that the evolution of the link delay estimates can be closely tracked by a deterministic ODE system. A study of the equilibrium points of the ODE then gives us the equilibrium behavior of the routing algorithm, in particular, the equilibrium routing probabilities, and mean delays in the links under equilibrium. We also show that the fixed-point equations that the equilibrium probabilities satisfy are actually the necessary and sufficient conditions of an appropriate optimization problem. Simulations supporting the analytical results are provided.},
	address = {New Orleans, Louisiana},
	booktitle = {46th IEEE Conference on Decision and Control},
	pages = {pp. 340-345}
}
@conference {
	title = {Observing a Linear Process over Analog Erasure Channels using Multiple Sensors: Necessary and Sufficient Conditions for Mean-square Stability},
	author = {Gupta, Vijay., Martins, Nuno C., Baras, John S.},
	year = {2007},
	month = {12/2007},
	abstract = {Consider a discrete-time linear time-invariant process being observed by two sensors, which are connected to an observer via links that can be modeled as erasure channels. If a link transmits successfully then a finite-dimensional vector of real numbers is conveyed from the sensor to the controller. If an erasure event occurs, then any information conveyed over the link is lost. This paper addresses the problem of designing the maps that specify the processing at the sensors and the observer to calculate the minimum mean square error estimate of the state of the process. We derive necessary and sufficient conditions for the existence of maps such that the estimate error is bounded in the second moment sense.},
	address = {New Orleans, Louisiana},
	booktitle = {46th IEEE Conference on Decision and Control},
	pages = {pp. 659-664}
}
@conference {
	title = {Combined Single-Path Routing and Flow Control in Many-User Region: A Case for Nash Efficiency},
	author = {Chen, Huigang., Baras, John S.},
	year = {2007},
	month = {12/2007},
	abstract = {We consider the problem of combined single-path routing and flow control, which is nonconvex and NP-hard to solve exactly. We focus on the {\textquotedblleft}many-user{\textquotedblright} region, i.e. large networks that have far more number of users than that of bottleneck links, which is close to real network scenarios. We first show that by allowing a proportionally small number of users to use multipath routing~while keeping the remaining majority to use single-path routing, the resulting solution achieves multipath optimality. Therefore it is conceptually plausible that in the many-user region a local algorithm can achieve solutions arbitrarily close to the optimal solution. To show this is indeed correct, we focus on the solutions brought out by the simplest local algorithm, the Nash algorithm. We first examine a special type of network and show that the Nash equilibrium exists and the Nash algorithm always converges. It is then shown that the price of anarchy, that is the gap between the worst Nash equilibrium and the social optimal, is bounded when the number of users goes to infinity. For general networks, it is not known whether there exists a Nash equilibrium. However, we introduce the concept of approximate Nash equilibrium and we show its existence given a~sufficiently large number of users. Then we prove that the approximate Nash equilibrium will be arbitrary close to the social optimal when the number of users is sufficiently large.},
	address = {New Orleans, Louisiana},
	booktitle = {46th IEEE Conference on Decision and Control},
	pages = {pp. 26-31}
}
@conference {
	title = {Broadcast Scheduling for Time-Constrained Information Delivery},
	author = {Raissi-Dekhordi, Majid., Baras, John S.},
	year = {2007},
	month = {11/2007},
	abstract = {In this report, the problem of broadcast scheduling in Push broadcast systems is studied. We introduce an optimization approach that leads to well-justified policies for Push broadcast systems with time constraints. In particular, we apply our results to a Push broadcast system with different deadlines associated to the files while allowing the files to have arbitrary demand rates and lengths.We calculate the optimal average cost for our experimental settings and show, through extensive simulation studies, that the results obtained from our scheduling policy are very close to that optimal value for each experiment.},
	address = {Washington DC},
	booktitle = {IEEE 2007 Global Communications Conference (GLOBECOM) Enhibition \&amp; Industry Forum},
	pages = {pp. 5298-5303}
}
@conference {
	title = {Intrusion Detection System Resiliency to Byzantine Attacks: The Case Study of Wormholes in OLSR},
	author = {Baras, John S., Radosavac, Svetlana., Theodorakopoulos, George., Sterne, Dan., Budulas, Peter., Gopaul, Richard.},
	year = {2007},
	month = {10/2007},
	abstract = {In this paper, we extend the work presented in [1] by quantifying the effects of in-band wormhole attacks on Intrusion Detection Systems. More specifically, we propose a mathematical framework for obtaining performance bounds of Byzantine attackers and the Intrusion Detection System (IDS) in terms of detection delay. We formulate the problem of distributed collaborative defense against coordinated attacks in MANET as a dynamic game problem. In our formulation, we have on the one hand a group of attackers that observe what is going on in the network and coordinate their attack in an adaptive manner. On the other side, we have a group of defending nodes (the IDS nodes) that collaboratively observe the network and coordinate their actions against the attackers. Using extensions of the game theoretic framework of [2] we provide a mathematical framework for efficient identification of the worst attacks and damages that the attackers can achieve, as well as the best response of the defenders. This approach leads to quantifying resiliency of the routing-attack IDS with respect to Byzantine attacks.},
	address = {Orlando, FL},
	booktitle = {2007 Military Communication Conference},
	pages = {pp. 1-7}
}
@conference {
	title = {Trust Document Distribution in Manets},
	author = {Jiang, Tao., Baras, John S.},
	year = {2007},
	month = {10/2007},
	abstract = {Mobile ad-hoc networks (MANETs) are used in battlefields where no network infrastructure exists. Users rely on their physical neighbors to communicate with other users that are not in proximity. Accurate trust establishment and maintenance is essential for secure and reliable message transmissions in MANETs. Because of the mobility and dynamics of MANETs, the validity and value of trust documents change~with time as well as with battlefield conditions and scenario stage. Thus trust management in MANETs is a much more dynamic problem than in conventional wireline networks, as well as wireless cellular networks. In traditional networks, centralized trusted servers provide necessary trust documents for trust establishment. However, such servers are not available in MANETs. Trust documents are distributed among users in the network. In this paper, we develop and analyze distributed schemes for efficiently and securely distributing trust documents, and updates, so that users are able to establish reliable trust relations with their neighbors. Key performance metrics are time response and availability of documents across the network. Our approach is inspired from network coding, where trust documents are combined during distribution.},
	address = {Orlando, FL},
	booktitle = {2007 Military Communication Conference},
	pages = {pp. 1-7}
}
@conference {
	title = {Loss Model Approximations and Sensitivity Computations for Multi-Hop Wireless Network Design},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas., Shang, Yadong.},
	year = {2007},
	month = {10/2007},
	abstract = {We develop and evaluate a new method for estimating various performance metrics of multi-hop wireless networks, including MANETs. The estimates depend implicitly on network design parameters, and therefore the method can form the basis for designing such networks so as to achieve predictable performance bounds. Explicit simulation models for large wireless networks are too complex and can not be used for analysis and design of wireless networks in realistic settings. We introduce a simple approximate (throughput) loss model that couples the physical, MAC and routing layers. The model provides quantitative statistical relations between the loss parameters used to characterize multiuser interference and physical path conditions on the one hand and traffic rates between origin-destination pairs on the other. We use a fixed point approach together with recently proposed models for the MAC layer to find a consistent solution satisfying all equations in the set. The result is an implicit model of performance metrics, such as throughput, packet loss, delay, parameterized by design variables, such as path routing probabilities, power levels, noise levels. We next apply Automatic Differentiation (AD) to these implicit performance models and develop a methodology for design and parameter selection/tuning of wireless protocols.},
	address = {Orlando, FL},
	booktitle = {2007 Military Communication Conference},
	pages = {pp. 1-7}
}
@conference {
	title = {Trust in Social, Communication and Other Networks},
	author = {Baras, John S.},
	year = {2007},
	month = {10/2007},
	address = {Stockholm, Sweden},
	booktitle = {ACCESS Lecture at the ACCESS Linnaeus Center},
	organization = {KTH, Royal Institute of Technology}
}
@conference {
	title = {Probabilistic Switching and Convergence Rate in Consensus Problems},
	author = {Hovareshti, Pedram., Baras, John S., Gupta, Vijay.},
	year = {2007},
	month = {09/2007},
	abstract = {We consider the convergence problem of consensus seeking agents and the effect of probabilistic switching on the convergence rate. Using a probabilistic setting, we develop a framework to study the convergence rate for different classes of graph topologies, including Small World networks. We show that by making the effective diameter of the underlying graph small, probabilistic switching can be helpful in the design of fast consensus algorithms.},
	address = {Chicago, Illinois},
	booktitle = {Allerton Conference on Communication, Control and Computing},
	pages = {pp. 423-430},
	organization = {Allerton House, UIUC}
}
@conference {
	title = {Improving Network Performance in Hybrid Wireless Networks Using a Satellite Overlay},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2007},
	month = {09/2007},
	abstract = {Large wireless networks have the ability to provide rapid connectivity in disaster areas~or to interconnect users in far-flung geographical locations. However, limitations on performance and robustness have delayed the adoption of such networks. In this paper, we show that by the addition of a satellite overlay network, the performance and robustness of large-scale wireless networks can be greatly improved and thus make their deployment possible. We define a satellite overlay network as consisting of one or more satellite nodes and multiple terrestrial {\textquoteleft}{\textquoteleft}gateway{\textquoteright}{\textquoteright} nodes that have interfaces for both satellite links and terrestrial wireless communication. We divide the terrestrial network into multiple {\textquoteleft}{\textquoteleft}clusters{\textquoteright}{\textquoteright} of wireless nodes, with each cluster being served by one or more gateway nodes. Ordinary terrestrial user nodes reach the gateway node through multi-hop terrestrial paths. We thus propose a design for a hybrid satellite and terrestrial wireless network. Through network modeling and simulation, we show that significant improvement in end-to-end performance is possible in a wireless network when the satellite overlay is present, in comparison to the performance in flat wireless networks. Our results are for both stationary and mobile ground wireless nodes.},
	address = {Turin, Italy},
	booktitle = {13th KA and Broadband Communications Conference},
	pages = {pp. 111-118}
}
@conference {
	title = {Collaborative Control of Underwater Vehicles under Severely Limited Communication},
	author = {Baras, John S.},
	year = {2007},
	month = {09/2007},
	address = {Bol, Croatia},
	booktitle = {2007 IFAC Conference on Controls and Applications in Marine Systems (CAMS {\textquoteright}07)}
}
@conference {
	title = {On Optimal Watermarking Schemes in Uncertain Gaussian Channels},
	author = {Cardenas, Alvaro A., Moustakides, George V., Baras, John S.},
	year = {2007},
	month = {09/2007},
	abstract = {This paper describes the analytical derivation of a new watermarking algorithm satisfying optimality properties when the distortion of the watermarked signal is caused by a Gaussian process. We also extend previous work under the same assumptions and obtain more general solutions.},
	address = {San Antonio, Texas},
	booktitle = {IEEE International Conference on Signal Processing ICIP 2007},
	pages = {pp. 449-452}
}
@conference {
	title = {Comparison of Ray Tracing Simulations and Millimeter Wave Channel Sounding Measurements},
	author = {Neekzad, Behnam., Sayrafian, Kamran., Perez, Julio., Baras, John S.},
	year = {2007},
	month = {09/2007},
	abstract = {Temporal-Angular channel sounding measurements of an indoor millimeter wave channel (60 GHz) is analyzed to determine the location of two-dimensional clusters of arrivals at the receiver. The measurement scenarios are also emulated by a ray tracing tool. The results are similarly analyzed to verify possible agreements and determine the effectiveness of such tools in predicting cluster locations as well as ray arrival statistics within clusters in millimeter wave indoor channel.},
	address = {Athens, Greece},
	booktitle = {18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications},
	pages = {pp. 1-5}
}
@conference {
	title = {Constrained Coalitional Games and Component Based Networking},
	author = {Baras, John S.},
	year = {2007},
	month = {08/2007},
	address = {Adelphi, Maryland},
	booktitle = {ARL Fellows Symposium: Towards a Science of Networks}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2007},
	month = {07/2007},
	address = {Athens, Greece},
	organization = {Department of Informatics, University of Athens}
}
@conference {
	title = {Security and Trust for Wireless Autonomic Networks: System and Control Methods},
	author = {Baras, John S.},
	year = {2007},
	month = {07/2007},
	address = {Kos Island, Greece},
	booktitle = {2007 European Control Conference (ECC07)}
}
@conference {
	title = {Effects of Graph Topology on Performance of Distributed Algorithms for Networked Control and Sensing},
	author = {Baras, John S., Hovareshti, Pedram.},
	year = {2007},
	month = {06/2007},
	abstract = {We consider distributed collaborative control andsensing as they frequently arise in networked control systems.The algorithms are constrained to use local information. Weshow by experiments that the performance of such distributed,local information based algorithms, can depend dramaticallyon the structure of the underlying topology (connectivitypattern) of the agents. We investigate the speed of convergence,accuracy, robustness and resiliency of such algorithms includingconsensus problems. We consider several graphs that can beused to represent collaborative control and communicationpatterns. We first show that small world topologies offer severaladvantages from a perspective of a favorable tradeoff betweenperformance of collaborative behaviors vs costs of collaborativebehaviors (or equivalently constraints for collaboration). Second,we show that a two level hierarchy consisting of carefullylocated and controlled leaders at the higher level and therest of the agents at the lower level, can provide a veryefficient communication pattern with substantial improvementof performance. We close with a description of the possibletopologies for this two tier structure and their performance.},
	address = {Kalamata, Greece},
	booktitle = {Proceedings of the 2007 Kalamata Workshop on Networked Distributed Systems for Intelligent Sensing and Control},
	pages = {pp. 1-8},
	organization = {Filoxenia}
}
@conference {
	title = {MPC Based Motion Control of Car-like Vehicle Swarms},
	author = {Xi, Wei., Baras, John S.},
	year = {2007},
	month = {06/2007},
	abstract = {In this paper we study low level motion control of car-like vehicles for applications of UAV swarms. First, a Suboptimal Continuous-Curvature trajectory generation approach is studied to generate suboptimal reference trajectories(tracks) to connect desired way-point sequences. Two Model Predictive Control (MPC) based track following control approaches are then proposed to deal with the multiple constraints present in practice; for example, actuator saturation,local collision avoidance. Simulations further confirm the motion control design.},
	address = {Athens, Greece},
	booktitle = {Proceedings of 15th IEEE Mediterranean Conference on Control and Automation},
	pages = {pp. 1-6}
}
@conference {
	title = {Level-triggered Control of a Scalar Linear System},
	author = {Rabi, Maben., Baras, John S.},
	year = {2007},
	month = {06/2007},
	abstract = {In networked control systems, because of limits on communication rates, control waveforms are frequently piece-wise constant with limits on rates at which they can switch levels. It is, therefore, natural to expect event triggered control switchings to perform more efficiently than time-triggered ones. This article verifies the validity of this supposition. A method for designing good level-triggered control schemes is obtained by reducing the continuous time problem to one in discrete time. Then, by numerical procedures, the performance of the level-triggered schemes is computed for comparison with that of the periodically switched control scheme.},
	address = {Athens, Greece},
	booktitle = {Proceedings of the 15th IEEE Mediterranean Conference on Control and Automation},
	pages = {pp. 1-6}
}
@conference {
	title = {Security and Trust Management in Wireless Autonomic Networks},
	author = {Baras, John S.},
	year = {2007},
	month = {06/2007},
	address = {Corfu, Greece},
	booktitle = {2007 Mediterranean Conference on Ad Hoc Networks (Med-Hoc-Net 2007)}
}
@conference {
	title = {A New Rate-based Active Queue Management: Adaptive Virtual Queue RED},
	author = {Byun, Do Jun., Baras, John S.},
	year = {2007},
	month = {05/2007},
	abstract = {In an effort to improve performance of congested gateways, a new Active Queue Management (AQM) algorithm, Adaptive Virtual Queue Random Early Detection (AVQRED), was developed by feeding virtual queue size to the RED algorithm. The objective of the new algorithm is to improve overall performance by keeping link utilization high, link utilization stable, queueing delay low and consecutive packet drop rate low. This paper shows the objective is met by comparing AVQRED with six other well known AQM methods in a realistic emulation environment. To provide fair comparisons, the AQM parameters are fine-tuned by exploring many different parameter settings via emulations. The emulation results conclude that AVQRED improves overall performance by 8 to 25\%. To provide intuitive properties and validate the emulation results, a mathematical model is proposed and fed to MATLAB, and the results from MATLAB and emulations are compared.},
	address = {New Brunswick, Canada},
	booktitle = {Proceedings of the 5th Annual Conference on Communication Networks and Services Research},
	pages = {pp. 389-396}
}
@conference {
	title = {Malicious Users in Unstructured Networks},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2007},
	month = {05/2007},
	abstract = {Unstructured networks (like ad-hoc or peer-to-peer networks) are networks without centralized control of their operation. Users make local decisions regarding whether to follow the network protocol or not. While providing scalability benefits, this degrades the performance, which is compounded by the potential presence of Malicious Users. In general, these users are trying to disrupt the operation of the network, and prevent the legitimate users from achieving their objectives. More specifically, they could try to break the connectivity of the network, or waste the resources of the legitimate users. In this work we use game theory to examine the effect of Malicious Users. All users are modeled as payoff-maximizing strategic agents. A simple model, fictitious play, is used for the legitimate user behavior, but no limits are imposed on the Malicious Users strategies. We look for the worst case equilibrium: the one that gives Malicious Users the highest payoff. We identify the importance of the network topology.},
	address = {Anchorage, Alaska},
	booktitle = {Proceedings of the 26th Annual IEEE Conference on Computer Communications (Infocom)},
	pages = {pp. 884-891}
}
@conference {
	title = {Performance Comparison of Detection Schemes for MAC Layer Misbehavior},
	author = {Cardenas, Alvaro A., Radosavac, Svetlana., Baras, John S.},
	year = {2007},
	month = {05/2007},
	abstract = {This paper revisits the problem of detecting greedy behavior in the IEEE 802.11 MAC protocol by evaluating the performance of two previously proposed schemes: DOMINO and the Sequential Probability Ratio Test (SPRT). The evaluation is carried out in four steps. We first derive a new analytical formulation of the SPRT that takes into account the discrete nature of the problem. Then we develop a new tractable analytical model for DOMINO. As a third step, we evaluate the theoretical performance of SPRT and DOMINO with newly introduced metrics that take into account the repeated nature of the tests. This theoretical comparison provides two major insights into the problem: it confirms the optimality of SPRT and motivates us to define yet another test, a nonparametric CUSUM statistic that shares the same intuition as DOMINO but gives better performance.We finalize the paper with experimental results, confirming our theoretical analysis and validating the introduction of the new nonparametric CUSUM statistic.},
	address = {Anchorage, Alaska},
	booktitle = {Proceedings of the 26th Annual IEEE Conference on Computer Communications (Infocom)},
	pages = {pp. 1496-1504}
}
@conference {
	title = {Adaptive Virtual Queue Random Early Detection in Satellite Networks},
	author = {Byun, Do Jun., Baras, John S.},
	year = {2007},
	month = {04/2007},
	abstract = {Due to exponential increases in internet traffic, Active Queue Management (AQM) has been heavily studied by numerous researchers. However, little is known about AQM in satellite networks. A microscopic examination on queueing behavior in satellite networks is conducted to identify problems with applying existing AQM methods. A new AQM method is proposed to overcome the problems and it is validated with a realistic emulation environment.},
	address = {Pomona, California},
	booktitle = {2007 IEEE Wireless Telecommunications Symposium}
}
@conference {
	title = {Robust Feedback Control vs Uncertainty Model Complexity: from Information Theory to Networked Control},
	author = {Baras, John S.},
	year = {2007},
	month = {04/2007},
	address = {Limasol, Cyprus},
	booktitle = {2007 Workshop on Control over Communication Channels (ConCom 07), part of WiOpt {\textquoteright}07}
}
@conference {
	title = {Stabilization Using Multiple Sensors over Analog Erasure Channels},
	author = {Gupta, Vijay., Martins, Nuno C., Baras, John S.},
	year = {2007},
	month = {04/2007},
	abstract = {Consider a discrete-time, linear time-invariant process,two sensors and one controller. The process is observed by the sensors, which are connected to the controller via links that can be modeled as erasure channels. If a link transmits successfully then a finite-dimensional vector of real numbers is conveyed from the sensor to the controller. If an erasure event occurs, then any information conveyed over the link is lost. This paper addresses the problem of designing the maps that specify the processing at the controller and at the sensors for stabilizing the process in the bounded second moment sense. When the information is lost over the links either in an independent and identically distributed (i.i.d.) or Markovian fashion over time,we derive necessary and sufficient conditions for the existence of maps such that the process is stabilized. Such conditions are expressed as inequalities involving the parameters of the plant and the probabilities of link fading. and provide the least conservative stabilization conditions. We also indicate how our approach can be used if more than two sensors are available,if the sensors can cooperate and if the acknowledgment signals are also transmitted over erasure channels. The analysis also carries over to the case when the single channels are replaced by networks of erasure channels.},
	address = {Limassol, Cyprus},
	booktitle = {Proceedings of the 2007 Control Over Communication Channels, co-located with IEEE WiOpt 2007 Conference},
	pages = {pp. 1-7}
}
@conference {
	title = {Fundamental Tradeoffs and Constrained Coalitional Games in Autonomic Wireless Networks},
	author = {Jiang, Tao., Baras, John S.},
	year = {2007},
	month = {04/2007},
	abstract = {Autonomic networks depend on collaboration between their nodes for all their functionalities. The nodes, even if modeled as selfish, gain from such collaboration, in the sense that they can accomplish functionality and performance that is impossible to achieve without such collaboration. However,such gains from collaboration do not come for free. There are costs for such collaboration incurred by each node (e.g. energy consumption for forwarding other nodes packets). In this paper we use constrained coalitional games (i.e. collaborative dynamic games subject to constraints or costs for collaboration) to investigate several key problems in autonomic wireless networks including: network formation, efficient topologies and stability of coalitions.},
	address = {Limassol, Cyprus},
	booktitle = {5th International Symposium on Modeling and Optimization in Mobile, Ad Hoc,and Wireless Networks},
	pages = {pp. 1-8}
}
@conference {
	title = {Towards Optimal Design of Data Hiding Algorithms Against Nonparametric Adversary Models},
	author = {Cardenas, Alvaro A., Moustakides, George V., Baras, John S.},
	year = {2007},
	month = {03/2007},
	abstract = {This paper presents a novel zero-sum watermarking game between a detection algorithm and a data hiding adversary. Contrary to previous research, the detection algorithm and the adversary we consider are both nonparametric in a continuous signal space, and thus they have no externally imposed limitations on their allowed strategies except for some distortion constraints. We show that in this framework no deterministic detection algorithm is optimal. We then find optimal randomized detection algorithms for different distortion levels and introduce a new performance tradeoff between completeness and accuracy when a detection algorithm does not have enough evidence to make an accurate decision.},
	address = {Baltimore, Maryland},
	booktitle = {41st Annual Conference on Information Sciences and Systems},
	pages = {pp. 911-916}
}
@conference {
	title = {Detecting IEEE 802.11 MAC Layer Misbehavior in Ad Hoc Networks},
	author = {Radosavac, Svetlana., Cardenas, Alvaro A., Baras, John S., Moustakides, George V.},
	year = {2007},
	month = {01/2007},
	abstract = {Selfish behavior at the Medium Access (MAC) Layer can have devastating side effects on the performance of wireless networks, with effects similar to those of Denial of Service (DoS) attacks. In this paper we consider the problem of detection and prevention of node misbehavior at the MAC layer, focusing on the back-off manipulation by selfish nodes. We first propose an algorithm that ensures honest behavior of non-colluding participants. Furthermore, we analyze the problem of colluding selfish nodes, casting the problem within a minimax robust detection framework and providing an optimal detection rule for the worst-case attack scenarios. Finally, we evaluate the performance of single and colluding attackers in terms of detection delay. Although our approach is general and can be used with any probabilistic distributed MAC protocol, we focus our analysis on the IEEE 802.11 MAC.},
	booktitle = {Robust Strategies Against Individual and Colluding Attacker\&quot; Journal of Computer Security: Special Issue on Security of Ad Hoc and Sensor Networks},
	pages = {pp. 103-128}
}
@conference {
	title = {Maximum Entropy Models, Dynamic Games and Robust Output Feedback Control of Nonlinear Systems},
	author = {Baras, John S.},
	year = {2006},
	month = {12/2006},
	abstract = {In this paper, we develop a framework for designing controllers for general, partially observed discretetime nonlinear systems which are robust with respect to uncertainties (disturbances). A general deterministic model for uncertainties is introduced, leading to a dynamic game formulation of the robust control problem. This problem is solved using an appropriate information state. We derive a partially observed nonlinear stochastic model as the maximum entropy stochastic model for the nonlinear system. A risk-sensitive stochastic control problem is formulated and solved for this partially observed stochastic model. The two problems are related using small noise limits. These small noise asymptotics are for the first time justified as the appropriate randomization, using time asymptotics of the Lagrange multipliers involved in the maximum entropy model construction. Thus for the first time a complete unification of deterministic and randomized uncertainty models is achieved. Various interpretations, consequences and applications of this unification are explained and discussed.},
	address = {San Diego, CA},
	booktitle = {45th IEEE Conference on Decision and Control},
	pages = {pp. 4899-4906}
}
@conference {
	title = {Gibbs Sampler Based Control of Autonomous Vehicle Swarms in the Presence of Sensor Errors},
	author = {Xi, Wei., Baras, John S.},
	year = {2006},
	month = {12/2006},
	abstract = {In earlier work of the authors[1], [2], [3], [4], [5], it was shown that Gibbs sampler based annealing algorithms could be used for vehicle swarms to achieve self-organization. Nevertheless, the earlier convergence analyses were based on the assumption that the Gibbs potential can be precisely evaluated. In practice, Gibbs potentials have to be measured via sensors, which usually introduce errors. The robustness of the stochastic algorithm under sensor errors is studied in this paper. Two types of sensor error, range-error and random error, are investigated. Analytical results on convergence are derived for sensor errors with limited support, and are further validated through simulations.},
	address = {San Diego, CA},
	booktitle = {45th IEEE Conference on Decision and Control},
	pages = {pp. 5084-5090}
}
@conference {
	title = {Multiple Sampling for Estimation on a Finite Horizon},
	author = {Rabi, Maben., Moustakides, George V., Baras, John S.},
	year = {2006},
	month = {12/2006},
	abstract = {We discuss some multiple sampling problems that arise in finite horizon real-time estimation when there is an upper limit on the number of allowable samples. Measuring estimation quality by the aggregate squared error, we compare the performances of the best deterministic, level-triggered and the optimal sampling schemes. We restrict the signal to be either a Wiener or an Ornstein-Uhlenbeck process. For the Wiener process, we provide closed form expressions and series expansions, whereas for the Ornstein Uhlenbeck process, procedures for numerical computation. Our results indicate that the best level-triggered sampling is almost optimal when the signal is stable.},
	address = {San Diego, CA},
	booktitle = {45th IEEE Conference on Decision and Control},
	pages = {pp. 1351-1357}
}
@conference {
	title = {A Unified Framework of Information Assurance for the Design and Analysis fo Security Algorithms},
	author = {Cardenas, Alvaro A., Taban, Gelareh., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {Most information security algorithms cannot achieve perfect security without incurring severe operational costs such as false alarms, network congestion, capital investment etc. Operating or designing an algorithm with perfect security is therefore not an economically rational alternative and thus the question arises of how to find the appropriate tradeoff between security and its costs. Although several other researchers have recognized that there is a tradeoff, there is very little work in formally characterizing it. This paper provides the first steps towards a more systematic and general approach for cost-effective security management.},
	address = {Orlando, FL},
	booktitle = {25th Army Science Conference},
	pages = {pp. 1-8}
}
@conference {
	title = {Component Based Routing: A New Methodology for Designing Routing Protocols for MANET},
	author = {Huang, H., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {Large variation of performance due to various environment inputs is a major impediment of implementing existing routing protocols for MANET in the battlefield. Therefore, it is a major challenge to design a routing protocol that can adapt its behavior to environment alteration. In consideration of adaptability to the environment and flexibility in protocol construction, a novel component based routing protocol methodology is proposed in this paper. Distinguished from conventional investigation of routing protocols as individual entities, this paper will firstly generalize four fundamental components for MANET routing protocols. Then, a weak component diagnosis process is proposed to improve a weak component and enhance the overall performance. Finally, preliminary simulation results demonstrate the power of the component based methodology for improving overall performance and reducing performance variation. In conclusion, the evaluation and improvement at the component level is more insightful and effective than that at the protocol level.},
	address = {Orlando, FL},
	booktitle = {25th Army Science Conference},
	pages = {pp. 1-8}
}
@conference {
	title = {Energy Efficient Millimeter Wave Radio Link Establishment for Low Probability of Intercept with Smart Antenna Arrays},
	author = {Neekzad, Behnam., Baras, John S., Sayrafian, Kamran.},
	year = {2006},
	month = {11/2006},
	abstract = {Consider a system of two millimeter wave transceiver nodes A and B. We assume that each node is equipped with a circular array antenna that has beamforming capability. We are interested in using the beamforming capability to find the best possible directions for transmission and reception such that the communication link between two nodes provides maximal SNR at the receiver. A protocol that in most cases achieves the optimal solution is developed and simulation results are provided to show the effectiveness of the algorithm.},
	address = {Orlando, FL},
	booktitle = {25th Army Science Conference},
	pages = {pp. 1-6}
}
@conference {
	title = {A Testbed for Comparing Trust Computation Algorithms},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {Trust is the expectation of a person about another person{\textquoteright}s behavior. Trust is important for many security related decisions about, e.g., granting or revoking privileges, controlling access to sensitive resources and information, or evaluating intelligence gathered from multiple sources. More often than not, the issue is complicated even further because the person making the decision has no direct trust relationship with every single subject whose trustworthiness needs to be evaluated. So, the decision maker needs to rely on recommendations by others, and then somehow aggregate the trust related information that is collected. In this work we provide an algebraic framework in which we can describe multiple ways that trust related information can be aggregated to form a single value. We show the similarities and differences that the various so called trust computation algorithms have, and associate these with the algebraic properties of the frame- work that we consider.},
	address = {Orlando, FL},
	booktitle = {25th Army Science Conference},
	pages = {pp. 1-8}
}
@conference {
	title = {A Game for Ad Hoc Network Connectivity in the Presence of Malicious Users},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {Ad hoc network users are resource constrained: Before transmitting data, they have to take into account the energy expenditure involved. Even if a user is, in principle, willing to spend energy to improve network connectivity, his actual decision will be heavily influenced by the decisions of his neighboring users, since they act as relay nodes for him. Moreover, some of the neighbors may not be as benign as he is; in fact, they could be outright malicious. We are abstracting the tradeoff between spending energy and increasing connectivity by modeling the interaction of a user with his one-hop neighbors in a game theoretic fashion. Two types of users exist: Good users willingly trade energy for connectivity, but only if they expect their neighbors to do the same; Bad users try to destroy connectivity, but also lure the Good users to waste energy. Within our model for user behavior and sophistication, we explore outcomes that can arise in this graphical game.},
	address = {San Francisco, CA},
	booktitle = {2006 IEEE Globecom Technical Conference},
	pages = {pp. 1-5}
}
@conference {
	title = {Two-Level Dynamic Bandwidth Allocation for A Space-To-Ground Relay Network},
	author = {Zeng, Hui., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {We address issues related to efficiency, fairness, end to- end delay minimization and Quality-of-Service in order to enable a flexible access and dynamic mission operation capability in the next generation NASA space-to-ground communication infrastructure. To provide efficient and fair utilization while guaranteeing specific service requirements for different traffic classes, we propose a two-level (long-term and short-term) sharing of a slotted high data rate satellite communication link. The implemented long-term optimal bandwidth allocation provides per-user/per-flow service guarantee and gives the inputs to the next level. In our short-term bandwidth allocation with threshold regulation, a small portion of bandwidth is still assigned to all active spacecraft in advance, but most bandwidth is dynamically allocated per frame by solving an optimal timeslot scheduling problem. We finally discuss simulation results and our design optimization approach.},
	address = {San Francisco, CA},
	booktitle = {2006 IEEE Globecom Technical Conference},
	pages = {pp. 1-6}
}
@conference {
	title = {Coalition Formation in MANETS},
	author = {Jiang, Tao., Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {Wireless ad-hoc networks rely on the cooperation of participating nodes for almost all their functions. However, due to resource constraints, nodes are generally selfish and try to maximize their own benefit when participating in the network. Therefore, it is important to study mechanisms which can be used as incentives to form coalitions inside the network. In this paper, we study coalition formation based on game theory, especially cooperative game theory. First, the dynamics of coalition formation proceeds via pairwise bargaining. We show that the size of the maximum coalition is a decreasing function of the cost for establishing a link. After the coalition formation process reaches the steady state, we are interested in the stability of coalitions. We prove that coalitions are stable in terms of both pairwise stability and coalitional stability.},
	address = {Orlando, FL},
	booktitle = {25th Army Science Conference},
	pages = {pp.1-8}
}
@conference {
	title = {Detection and Performance Analysis of Greedy Individual and Colluding MAC Layer Attackers},
	author = {Radosavac, Svetlana., Baras, John S.},
	year = {2006},
	month = {11/2006},
	abstract = {Selfish behavior at the Medium Access (MAC) Layer can have devastating side effects on the performance of wireless networks, with effects similar to those of Denial of Service (DoS) attacks. In this paper we consider the problem of misbehavior detection at the MAC layer, focusing on the back-off manipulation by colluding selfish nodes. We cast the problem within a minimax robust detection framework, providing a detection rule of optimum performance for the worst-case attack. We analyze the effects of a single optimal attacker with respect to the detection delay and average number of backoff slots and compare them with the effects of colluding attackers.},
	address = {Myconos, Greece},
	booktitle = {2006 Information Society Technologies Conference}
}
@conference {
	title = {Distributed Trust in MANET: New Analytical Approaches},
	author = {Baras, John S.},
	year = {2006},
	month = {11/2006},
	address = {Adelphi, Maryland},
	booktitle = {Collaborative Technology Alliance on Communications and Networks},
	organization = {Army Research Laboratory}
}
@conference {
	title = {Impact of Optimal MAC Layer Attacks on the Network Layer},
	author = {Radosavac, Svetlana., Baras, John S., Moustakides, George V.},
	year = {2006},
	month = {10/2006},
	abstract = {Node misbehavior in wireless ad hoc networks leads to sudden unpredictable changes in network topology, resulting in fluctuation of traffic load and capacity for already existing links. In this work we consider node misbehavior in the Medium Access Control (MAC) layer and its effects on the performance of the network layer. In order to capture uncertainty of the attacker{\textquoteright}s strategy as well as the unpredictable nature of the wireless medium, we quantify the optimal attack strategy by using the principle of minimum cross entropy. Following that, we apply the obtained results for analysis of the IEEE 802.11 DCF MAC protocol and investigate the effects of such optimal attacks on the network layer. Finally, we evaluate the robustness of two different routing protocols against the worst-case MAC layer attacks and justify the need for the MAC layer-based Intrusion Detection Systems (IDS).},
	address = {Alexendria, VA},
	booktitle = {Fourth ACM Workshop on Security of Ad Hoc and Sensor Networks (SASN 2006)},
	pages = {pp. 135-145}
}
@conference {
	title = {Autonomic Wireless Networks and Computational Problems on Graphs},
	author = {Baras, John S.},
	year = {2006},
	month = {10/2006},
	address = {Stockholm, Sweden},
	organization = {Center for Industrial and Applied Mathematics, Royal Institute of Technology (CIAM KTH)}
}
@conference {
	title = {Analytical Methods for Trust Management in Autonomic Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {10/2006},
	address = {Leuven, Belgium},
	booktitle = {Study Day of the Interuniversity Attraction Pole IAP V/22 Dynamical Systems and Control: Computation, Identification and Modelling, the UCL research action on Large Graphs and Networks and the Francqui Foundation},
	organization = {Katholieke Universiteit Leuven}
}
@conference {
	title = {Component Based Design and Synthesis of Cyber-Physical Systems},
	author = {Baras, John S.},
	year = {2006},
	month = {10/2006},
	address = {Austin, Texas},
	booktitle = {NSF Workshop on Cyber-Physical Systems}
}
@conference {
	title = {Incentive Compatible Medium Access Control in Wireless Networks},
	author = {Benammar, Nassir., Baras, John S.},
	year = {2006},
	month = {10/2006},
	abstract = {The current IEEE 802.11 medium access control standard is being deployed in coffee shops, in airports and even across major cities. The terminals accessing these wi-fi access points do not belong to the same entity, as in corporate networks,but are usually individually owned and operated. Entities sharing these network resources have no incentive in following protocol rules other than to optimize their overall utility, usually a function of throughput and delay. We briefly discuss shortfalls of the current IEEE 802.11 standard in environments where terminals are competing for a common bandwidth resource, and then we introduce a new MAC protocol designed with the above considerations. Thus the new Incentive Compatible MAC (ICMAC) protocol is more suited for these open environments, without compromising the overall network performance.},
	address = {Pisa, Italy},
	booktitle = {2006 Workshop on Game Theory for Networks (GameNets 2006)}
}
@conference {
	title = {Systems Engineering for Automating V\&V of Dependable Systems},
	author = {Baras, John S.},
	year = {2006},
	month = {10/2006},
	address = {Alexendria, VA},
	booktitle = {NITRD HCSS-AS National Workshop on Aviation Software Systems: Design for Certifiably Dependable Systems}
}
@conference {
	title = {Dynamic Path Planning Around Moving Obstacles by Collaborating Robots for Space Exploration},
	author = {Brezina, Matthew, Baras, John S.},
	year = {2006},
	month = {09/2006},
	abstract = {We investigate dynamic control of collaborating robots by integrating methodologies from path planning and dynamic prediction of moving obstacles. Predicting for a finite horizon, instead of one step ahead, provides far better results. Efficient distributed algorithms are implemented and demonstrated via simulations. A combination of optimization and logic is needed for best performance and efficiency.},
	address = {San Jose, CA},
	booktitle = {Space 2006},
	pages = {pp. 1-5}
}
@conference {
	title = {An Integrative Principled Approach to Network Science for Autonomic Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {08/2006},
	address = {Athens, Greece},
	booktitle = {ARO-AFOSR Network Science Workshop}
}
@conference {
	title = {An Integrative Principled Approach to Network Science for Autonomic Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {08/2006},
	address = {Athens, Greece},
	booktitle = {ARO-AFOSR Network Science Workshop}
}
@conference {
	title = {Emerging Wireless Technologies and Services for Better Quality of Life and Work},
	author = {Baras, John S.},
	year = {2006},
	month = {08/2006},
	address = {Athens, Greece},
	booktitle = {45th Congress of the Federation of Telecommunications Engineers of the European Community (FITCE)}
}
@conference {
	title = {Enhancing Benign User Cooperation in the Presence of Malicious Adversaries in Ad Hoc Networks},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {08/2006},
	abstract = {Decentralized and unstructured networks are becoming more prevalent today (e.g. ad hoc networks). Like every network, they depend on the cooperation of their users to survive. However, each user does not necessarily know who the others are, or what their intentions are. Since there is no centralized infrastructure, the users can only base their decision on what they observe themselves. Ideally, they would like to cooperate only with users that have common interests with them. In this paper, we use a game theoretic model for the above situation. We assume there are only two kinds of users, Good (benign) and Bad (malicious). Good users receive a high game theoretic payoff when they cooperate with other Good users, but a low payoff when they cooperate with Bad users. We propose behavior rules (strategies) to achieve equilibria that enable as many Good users as possible to cooperate with each other, and at the same time minimize the number of Good-Bad cooperations.},
	address = {Baltimore, MD},
	booktitle = {2006 IEEE Communications Society/CreateNet International Conference on Security and Privacy in Communication Networks}
}
@conference {
	title = {Broadband Mobile Wireless Infrastructures: The Next {\textquoteleft}Massive Impact{\textquoteright} Paradigm Shift},
	author = {Baras, John S.},
	year = {2006},
	month = {07/2006},
	address = {Tokyo, Japan},
	organization = {Fujitsu Laboratories, Kawasaki}
}
@conference {
	title = {Vehicle Wireless Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {07/2006},
	address = {Tochigi, Japan},
	organization = {HONDA R\&D Center}
}
@conference {
	title = {Scalable and Distributed Control Laws for Network flow Optimization},
	author = {Chen, Huigang., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {We investigate the design of scalable and distributed control laws for flow control in a large network - equivalently an optimization problem. We identify the implications of the desired "plug-and-play{\textquoteright} property of of such protocols and propose design principles upon which our algorithm should be built: the class of our algorithms must achieve little extra communication cost and global asymptotic stability. General structural properties of such algorithms are presented and we finally provide an algorithm which satisfies our design principles for a network with heterogeneous delays.},
	address = {Kyoto, Japan},
	booktitle = {17th International Symposium on Mathematical Networks and Systems},
	pages = {pp. 42-49}
}
@conference {
	title = {Linear Iterations on Ordered Semirings for Trust Metric Computation and Attack Resiliency Evaluation},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {Within the realm of network security, we interpret the concept of trust as a relation among entities that participate in various protocols. Trust relations are based on evidence created by the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation of trust evidence in Ad Hoc Networks. Because of the dynamic nature of Ad Hoc Networks. Because of the dynamic nature of Ad Hoc Networks, trust evidence may be uncertain and incomplete. Also, no pre-established infrastructure can be assumed. The evaluation process is modelled as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We develop a novel formation of trust computation as linear interactions on ordered semirings. Using the theory of semirings, we analyze several key problems on the performance of trust algorithms. We also analyze the resilience to attacks of the resulting schemes.},
	address = {Kyoto, Japan},
	booktitle = {Proceedings of the 17th International Symposium on Mathematical Networks and Systems},
	pages = {pp. 509-514}
}
@conference {
	title = {Evaluation of Classifiers: Practical Considerations for Security Applications},
	author = {Cardenas, Alvaro A., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {In recent years several tools based on statistical methods and machine learning have been incorporated in security related tasks involving classification, such as intrusion detection systems (IDSs), fraud detection, spam filters, biometrics and multimedia forensics. Measuring the security performance of these classifiers is an essential part for facilitating decision making, determining the viability of the product, or for comparing multiple classifiers. There are however relevant considerations for security related problems that are sometimes ignored by traditional evaluation schemes. In this paper we identify two pervasive problems in security related applications. The first problem is the usually large class imbalance between normal events and attack events. This problem has been addressed by evaluating classifiers based on cost-sensitive metrics and with the introduction of Bayesian Receiver Operating Characteristic (B-ROC) curves. The second problem to consider is the fact that the classifier or learning rule will be deployed in an adversarial environment. This implies that good performance on average might not be a good performance measure, but rather we look for good performance under the worst type of adversarial attacks. In order to address this notion more precisely we provide a framework to model an adversary and define security notions based on evaluation metrics.},
	address = {Boston, Massachusetts},
	booktitle = {AAAI Workshop on Evaluation Methods for Machine Learning}
}
@conference {
	title = {B-ROC Curves for the Assessment of Classifiers over Imbalanced Data Sets},
	author = {Cardenas, Alvaro A., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {The class imbalance problem appears to be ubiquitous to a large portion of the machine learning and data mining communities. One of the key questions in this setting is how to evaluate the learning algorithms in the case of class imbalances. In this paper we introduce the Bayesian Receiver Operating Characteristic (B-ROC) curves, as a set of tradeoff curves that combine in an intuitive way, the variables that are more relevant to the evaluation of classifiers over imbalanced data sets. This presentation is based on section 4 of (C{\textasciiacute}ardenas, Baras, \&amp; Seamon 2006).},
	address = {Boston, Massachusetts},
	booktitle = {21st National Conference on Artificial Intelligence, (AAAI 06) Nectar track,},
	pages = {pp. 1581-1584}
}
@conference {
	title = {Evaluation of Classifiers Practical Considerations for Security Applications},
	author = {Cardenas, Alvaro A., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {In recent years several tools based on statistical methods and machine learning have been incorporated in security related tasks involving classification, such as intrusion detection systems (IDSs), fraud detection, spam filters, biometrics and multimedia forensics. Measuring the security performance of these classifiers is an essential part for facilitating decision making, determining the viability of the product, or for comparing multiple classifiers. There are however relevant considerations for security related problems that are sometimes ignored by traditional evaluation schemes. In this paper we identify two pervasive problems in securityrelated applications. The first problem is the usually large class imbalance between normal events and attack events. This problem has been addressed by evaluating classifiers based on cost-sensitive metrics and with the introduction of Bayesian Receiver Operating Characteristic (B-ROC) curves. The second problem to consider is the fact that the classifier or learning rule will be deployed in an adversarial environment. This implies that good performance on average might not be a good performance measure, but rather we look for good performance under the worst type of adversarial attacks. In order to address this notion more precisely we provide a framework to model an adversary and define security notions based on evaluation metrics},
	address = {Boston, MA},
	booktitle = {AAAI Workshop on Evaluation Methods for Machine Learning}
}
@conference {
	title = {Modeling and Synthesis of Networked Systems},
	author = {Baras, John S.},
	year = {2006},
	month = {07/2006},
	address = {Paris, France},
	booktitle = {Joint CTS-HYCON Workshop on Nonlinear Research and Hybrid Control}
}
@conference {
	title = {Ray-Tracing Simulation of the NICT Channel Measurements},
	author = {Sayrafian, Kamran., Neekzad, Behnam., Perez, Julio., Baras, John S.},
	year = {2006},
	month = {07/2006},
	address = {San Diego, CA},
	booktitle = {IEEE Standard 802.15.3c mm-Wave channel modeling subgroup}
}
@conference {
	title = {Modeling Key Agreement in Multi-Hop Ad Hoc Networks},
	author = {Crescenzo, Giovanni Di., Striki, Maria., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {Securing multicast communications in ad hoc networks has become one of the most challenging research directions in the areas of wireless networking and security. This is especially true as ad hoc networks are emerging as the desired environment for an increasing number of civilian, commercial and military applications, also addressing an increasingly large number of users. In this paper we study a very basic security question for Ad Hoc Networks: Key Agreement against passive adversaries. Despite being a widely studied area in wired networks, the problem becomes significantly more challenging for ad hoc networks, and even more for sensor networks, due to lack of trusted entities, infrastructures, full connectivity, routing structures, and due to severe limitations on the resources and capabilities of network nodes. In this paper we perform a comprehensive investigation of Key Agreement over resource constrained ad hoc networks. First, we formally model the key agreement problem over multi-hop ad hop networks, and we directly extend known key agreement protocols for wired networks, and evaluate the efficiency of such approaches. We then go beyond natural extensions of such protocols, by proposing non-trivial extensions based on efficient topology-driven simulations of logical networks over an arbitrary physical network, in order to optimize the most significant metrics of interest for such networks: i.e. bandwidth, latency, processing cost. Indeed, the resulting protocols are significantly more efficient in some or all of the above metrics, as our analytical results indicate},
	address = {Vancouver, Canada},
	booktitle = {2006 International Wireless Communications and Mobile Computing Conference},
	pages = {pp. 39-44}
}
@conference {
	title = {Efficient Sampling for Keeping Track of an Ornstein-Uhlenbeck Process},
	author = {Rabi, Maben., Moustakides, George V., Baras, John S.},
	year = {2006},
	month = {06/2006},
	abstract = {We consider estimation and tracking problems in sensor networks with constraints in the hierarchy of inference making, on the sharing of data and inter-sensor communications. We identify as a typical representative for such problems tracking of a process when the number and type of measurements are constrained. As the simplest representative of such problems, which still encompasses all the key issues involved, we analyze efficient sampling schemes for tracking an Ornstein- Uhlenbeck process. We consider sampling based on time, based on amplitude (event-triggered sampling) and optimal sampling (optimal stopping). We obtain the best sampling rule in each case as the solution to a constrained optimization problem. We compare the performances of the various sampling schemes and show that the event-triggered sampling performs close to optimal. Implications and extensions are discussed.},
	address = {Anconia, Italy},
	booktitle = {14th Mediterranean Conference on Control and Automation},
	pages = {pp. 1-6}
}
@conference {
	title = {Distributed Control of Autonomous Swarms by Using Parallel Simulated Annealing Algorithm},
	author = {Xi, Wei., Baras, John S.},
	year = {2006},
	month = {06/2006},
	abstract = {In early work of the authors, it was shown that Gibbs sampler based sequential annealing algorithm could be used to achieve self-organization in swarm vehicles based only on local information. However, long travelling time presents barriers to implement the algorithm in practice. In this paper we study a popular acceleration approach, the parallel annealing algorithm, and its convergence properties. We first study the convergence and equilibrium properties of the synchronous parallel sampling algorithm. A special example based on a battle field scenario is then studied. Sufficient conditions that the synchronous algorithm leads to desired configurations (global minimizers) are derived. While the synchronized algorithm reduces travelling time, it also raises delay and communication cost dramatically, in order to synchronize moves of a large group of vehicles. An asynchronous version of the parallel sampling algorithm is then proposed to solve the problem. Convergence properties of the asynchronous algorithm are also investigated.},
	address = {Anconia, Italy},
	booktitle = {14th Mediterranean Conference on Control and Automation},
	pages = {pp. 1-6}
}
@conference {
	title = {Control and Security of Networked Embedded Systems: Component Based Synthesis},
	author = {Baras, John S.},
	year = {2006},
	month = {06/2006},
	address = {Helsinki, Finland},
	booktitle = {, NSF-EU/IST TEKES Workshop: Long Term Challenges in High Confidence Embedded Systems}
}
@conference {
	title = {Distributed Trust Management in Wireless Autonomic Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {06/2006},
	address = {Canberra, Australia},
	organization = {Research School of Information Sciences and Engineering (RSISE), Australian National University}
}
@conference {
	title = {A Robust Distributed TGDH-based Scheme for Secure Group Communications in MANET{\textquoteright}s},
	author = {Striki, Maria., Baras, John S., Manousakis, Kyriakos.},
	year = {2006},
	month = {06/2006},
	abstract = {Securing multicast communications in Mobile Ad Hoc Networks (MANET) is considered among the most challenging research directions in the areas of wireless networking and security. MANET is emerging as the desired environment for an increasing number of commercial and military applications, addressing also a growing number of users. Security, on the other hand, is now an indispensable requirement for these applications. However, the limitations of the dynamic, infrastructure-less nature of MANET impose major difficulties in establishing a secure framework suitable for such services. The design of efficient key management (KM) schemes for MANET is of paramount importance since the performance of the KM functions imposes an upper limit on the efficiency and scalability of the whole secure group communication system. In this work, we contribute towards this direction by extending TGDH to a novel distributed scheme: DS-TGDH. Our aim is to modify TGDH to: a) be feasible in the most general resource-constrained MANET where no nodes with special capabilities exist, b) produce considerably lower overhead for the network nodes involved, c) handle disruptions with low cost. We consider the underlying routing protocol in our design, and we apply a distributed TGDH version over a robust schedule, optimizing parameters of interest. We focus on the design and analysis of the {\textquotedblleft}stealthy{\textquotedblright} TGDH and compare it with the original. Through our analysis and results, we shed insight on the actual feasibility of these protocols for MANET and provide realistic and fair comparison results that more accurately advocate the pros and cons of each protocol over the environment of study.},
	address = {Istanbul, Turkey},
	booktitle = {ICC2006 - IEEE International Conference on Communications},
	pages = {pp. 2249-2255}
}
@conference {
	title = {Flexible and Dynamic Communication Architecture for Lunar Exploration},
	author = {Zeng, Hui., Roy-Chowdhury, Ayan., Rentz, Nicolas., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2006},
	month = {06/2006},
	abstract = {We present work related to designing a communication network for lunar exploration. We discuss the important requirements for future space missions that influence the design of this network. We list some characteristics of the network, and highlight important issues and constraint related to performance, cost, and future network evolution. We address issues related to efficiency, fairness, end-to-end delay minimization and Quality-of-Service (QoS) framework in order to enable a flexible access and dynamic mission operation. To provide optimal or near-optimal efficient utilization and fair allocation of bandwidth of the downlink channel while guaranteeing specific QoS requirements for different service classes, we propose two-level (long-term static and short-term dynamic) sharing of a slotted high data rate satellite communication link. The long-term optimal bandwidth allocation is implemented to provide per-stream/per-user QoS guarantee and give the inputs to the next level, short-term dynamic bandwidth allocation. In our time-varying short-term bandwidth allocation with threshold regulation, a small portion of bandwidth is still assigned to all active spacecrafts in advance, but most bandwidth is dynamically allocated by the requests from them, per frame, by solving an optimal timeslot scheduling problem.},
	address = {San Diego, CA},
	booktitle = {24th American Institute of Aeronautics and Astronautics},
	pages = {pp. 1-9}
}
@conference {
	title = {Flow Control and Active Queue Management for Integrated Services in an Aeronautical Satellite Network},
	author = {Shang, Yadong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2006},
	month = {06/2006},
	abstract = {The IP-based broadband aeronautical satellite network will provide numerous new applications and services for both airspace system operations and passenger communications. Application of commercial off the shelf technologies and techniques has the potential to make network operations economically and technically realizable. However the performance of data communication protocols and applications over aeronautical satellite networks is degraded dramatically. For the satellite channel, the window based flow control algorithm may cause transient congestion. The flow control mechanisms with or without explicit feedback from the congested resource are limited in performance and not effective. We propose a hierarchical scheduler for satellite gateways. Different service disciplines are used for integrated services. A Random Early Detection Flow Control (REDFC) algorithm is proposed for best-effort traffic at the satellite gateways. In REDFC, each packet is transmitted with a probability that is a function of the queue length. If the packet is not transmitted successfully, it will be retransmitted after certain time interval. We also propose a virtual parallel queue structure as a new active queue management scheme for short life and long life web traffic. The new flow control and active queue management schemes will provide better performance for integrated services in aeronautical satellite networks.},
	address = {San Diego, CA},
	booktitle = {24th American Institute of Aeronautics and Astronautics},
	pages = {pp. 1-10}
}
@conference {
	title = {Future of Mobile Communications: Distributed Trust Management in Wireless Autonomic Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {06/2006},
	address = {Mykonos, Greece},
	booktitle = {15th IST Mobile and Wireless Communication Research Summit}
}
@conference {
	title = {An Integrative Principled Approach to Network Science},
	author = {Baras, John S.},
	year = {2006},
	month = {05/2006},
	booktitle = {ARL Network Science STI Workshop}
}
@conference {
	title = {Consensus Problems on Small World Graphs: A Structural Study},
	author = {Hovareshti, Pedram., Baras, John S.},
	year = {2006},
	month = {05/2006},
	abstract = {Consensus problems arise in many instances of collaborative control of multi-agent complex systems; where it is important for the agents to act in coordination with the other agents. To reach coordination, agents need to share information. In large groups of agents the information sharing should be local in some sense, due to energy limitation, reliability, and other constraints. A consensus protocol is an iterative method that provides the group with a common coordination variable. However, local information exchange limits the speed of convergence of such protocols. Therefore, in order to achieve high convergence speed, we should be able to design appropriate network topologies. A reasonable conjecture is that the small world graphs should result in good convergence speed for consensus problems because their low average pairwise path length should speed the diffusion of information in the system. In this paper we address this conjecture by simulations and also by studying the spectral properties of a class of matrices corresponding to consensus problems on small world graphs.},
	address = {Boston, Massachusetts},
	booktitle = {2006 International Conference on Complex Systems},
	pages = {pp. 1-8}
}
@conference {
	title = {A Framework for the Evaluation of Intrusion Detection Systems},
	author = {Cardenas, Alvaro A., Baras, John S., Seamon, Karl.},
	year = {2006},
	month = {05/2006},
	abstract = {Classification accuracy in intrusion detection systems (IDSs) deals with such fundamental problems as how to compare two or more IDSs, how to evaluate the performance of an IDS, and how to determine the best configuration of the IDS. In an effort to analyze and solve these related problems, evaluation metrics such as the Bayesian detection rate, the expected cost, the sensitivity and the intrusion detection capability have been introduced. In this paper, we study the advantages and disadvantages of each of these performance metrics and analyze them in a unified framework. Additionally, we introduce the intrusion detection operating characteristic (IDOC) curves as a new IDS performance tradeoff which combines in an intuitive way the variables that are more relevant to the intrusion detection evaluation problem. We also introduce a formal framework for reasoning about the performance of an IDS and the proposed metrics against adaptive adversaries. We provide simulations and experimental results to illustrate the benefits of the proposed framework.},
	address = {Oakland, California},
	booktitle = {2006 IEEE Symposium on Security and Privacy}
}
@conference {
	title = {Networked Embedded Systems: Component Based System Synthesis},
	author = {Baras, John S.},
	year = {2006},
	month = {05/2006},
	booktitle = {Office of the Secretary of Defense (OSD) Software-Intensive Systems Producibility Workshop}
}
@conference {
	title = {Dynamic Bandwidth Allocation for a Space Relay Communications Network},
	author = {Zeng, Hui., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2006},
	month = {04/2006},
	abstract = {We address issues related to efficiency, fairness, end-to-end delay minimization and Quality-of-Service framework in order to enable a flexible access and dynamic mission operation capability in the next generation NASA space-to-ground communication infrastructure. To provide optimal or near-optimal efficient utilization and fair allocation of bandwidth of the downlink channel while guaranteeing specific service requirements for different service classes, we propose two-level (long-term static and short-term dynamic) sharing of a slotted high data rate satellite communication link. The long-term optimal bandwidth allocation is implemented to provide per-stream/per-user service guarantee and give the inputs to the next level short-term dynamic bandwidth allocation. In our time-varying short-term bandwidth allocation with threshold regulation, a small portion of bandwidth is still assigned to all active spacecraft in advance but most bandwidth is dynamically allocated by the requests from them per frame by solving an optimal time slot scheduling problem.},
	address = {Charlottesville, Virginia},
	booktitle = {2006 IEEE Systems and Information Engineering Design Symposium (SIEDS06)},
	pages = {pp.75-80}
}
@conference {
	title = {Analyzing BGP ASPATH Behavior in the Internet},
	author = {Blazakis, Dionysus., Karir, Manish., Baras, John S.},
	year = {2006},
	month = {04/2006},
	abstract = {In this paper we introduce a new metric for analyzing the behaviour of ASPATH values in the Border Gateway Protocol (BGP) routing protocol. We base our metric on the edit distance algorithm, an algorithm used for approximate string matching. We modify this basic algorithm by adding features that embed BGP domain knowledge. This allows us to perform meaningful comparisons of ASPATH values contained in BGP update messages. We call our modified metric ASPATH Edit Distance(AED). We illustrate the application of this metric to characterize ASPATH changes at a global scale using the example of a major Internet routing anomaly. At the other end of the spectrum we illustrate how this metric can be used to quantify and model the behaviour of ASPATH values for individual Autonomous Systems. AED provides us with an important measure with which we can study the behaviour of ASPATHS in the Internet. With sufficient refinement, AED can be suitably adapted and used alongside other metrics in BGP routing anomaly detection algorithms and tools.},
	address = {Barcelona, Spain},
	booktitle = {Proceedings of the 9th IEEE Global Internet 2006 Symposium}
}
@conference {
	title = {Trust Evaluation in Anarchy: A Case Study on Autonomous Networks},
	author = {Jiang, Tao., Baras, John S.},
	year = {2006},
	month = {04/2006},
	abstract = {With the explosive growth of network techniques, in particular wireless communications, the traditional centralized, fixed networks can no longer satisfy the enormous demands on network connectivity, data storage and information exchanges. New types of networks, such as pervasive computing networks, mobile ad hoc networks and P2P networks, emerged in recent years in order to provide solutions for the increasing requirements on networked services. All those networks are autonomous networks, because they are distributed and self-organized. As a case study, we employ a specific application {\textendash} distributed trust management {\textendash} to understand and analyze the behavior and properties of these {\textquotedblleft}anarchical{\textquotedblright} autonomous networks. We propose a statistical trust evaluation rule, prove its convergence and investigate its characteristics when the system is at the steady state. Our investigation results in several conclusions for the design of trust evaluation rules, some of which are unexpected if we do not have the stationary distribution at hand. Our study shows the importance and necessity of applying theoretical analyses to understand the complex characteristics of distributed, self-organized, autonomous networks.},
	address = {Barcelona, Spain},
	booktitle = {Proceedings of the 25th IEEE Conference on Computer Communications (Infocom06)}
}
@conference {
	title = {BGP-Inspect - Extracting Information from Raw BGP Data},
	author = {Blazakis, Dionysus., Karir, Manish., Baras, John S.},
	year = {2006},
	month = {04/2006},
	abstract = {While BGP routing datasets, consisting of raw routing data, are freely available and easy to obtain, extracting any useful information is tedious. Currently, researcher and network operators implement their own custom data processing tools and scripts. A single tool that provides easy access to the information within large raw BGP data-sets could be used by both communities to avoid re-writing these tools each time. Moreover, providing not just raw BGP messages, but some commonly used summary statistics as well can help guide deeper custom analyses. Based on these observations this paper describes the first steps towards building a scalable tool. We describe the various techniques and algorithms we have used to build an efficient generic tool called BGP-Inspect. When dealing with large datasets, dataset size, lookup speed, and data processing time are the most challenging issues. We describe our implementations of chunked compressed files and B+ tree indices that attempt to address these issues. We then provide an evaluation of our implementations. Finally, we provide some example scenarios and case studies where BGP-Inspect can provide useful insight into the management and operation of complex BGP based networks. An efficient and flexible back-end custom BGP message database, coupled with an intuitive and easy to use web-based query front-end makes BGP-Inspect a unique and powerful tool.},
	address = {Vancouver, Canada},
	booktitle = {10th IEEE/IFIP Network Operations and Management Symposium},
	pages = {pp.174-185}
}
@conference {
	title = {Networked Embedded Systems: Component Based Design and Security},
	author = {Baras, John S.},
	year = {2006},
	month = {03/2006},
	booktitle = {Joint US-EU Workshop: ICT Enabled Critical Infrastructures and Interdependencies}
}
@conference {
	title = {Collaborative Networked Control: Stochastic Algorithms},
	author = {Baras, John S.},
	year = {2006},
	month = {03/2006},
	address = {Champaign, IL},
	booktitle = {Decision and Control Seminar},
	organization = {University of Illinois Urbana-Champaign}
}
@conference {
	title = {Cooperative Games, Statistical Physics and Trust in Ad Hoc Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {03/2006},
	address = {Champaign, IL},
	organization = {Information Trust Institute, University of Illinois Urbana-Champaign}
}
@conference {
	title = {On Trust Models and Trust Evaluation Metrics for Ad Hoc Networks},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {02/2006},
	abstract = {Within the realm of network security, we interpret the concept of trust as a relation among entities that participate in various protocols. Trust relations are based on evidence created by the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation of trust evidence in ad hoc networks. Because of the dynamic nature of ad hoc networks, trust evidence may be uncertain and incomplete. Also, no preestablished infrastructure can be assumed. The evaluation process is modeled as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We give intuitive requirements and discuss design issues for any trust evaluation algorithm. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. We show that our semiring framework is flexible enough to express other trust models, most notably PGP{\textquoteright}s Web of Trust. Our scheme is shown to be robust in the presence of attackers.},
	booktitle = {IEEE Journal on Selected Areas in Communications},
	pages = {pp. 318-328}
}
@conference {
	title = {Collaborative Networked Control: Stochastic Algorithms},
	author = {Baras, John S.},
	year = {2006},
	month = {01/2006},
	address = {Athens, Greece},
	organization = {Institute of Communication and Computer Systems (ICCS), National Technical University of Athens}
}
@conference {
	title = {Collaborative Networked Control: Stochastic Algorithms},
	author = {Baras, John S.},
	year = {2006},
	month = {01/2006},
	address = {Vienna, Austria},
	organization = {Institute of Econometrics, Operations Research and Systems Theory, University of Technology Vienna}
}
@conference {
	title = {Trust in Self-organized Mobile Ad Hoc Networks},
	author = {Baras, John S.},
	year = {2006},
	month = {01/2006},
	address = {Lausanne, Switzerland},
	organization = {Center for Telecommunications Research, Ecole Federale Polytechnique de Lausanne (EPFL)}
}
@conference {
	title = {Coalition Formation in MANET and Other Networks},
	author = {Jiang, Tao., Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {01/2006},
	abstract = {Wireless ad-hoc networks rely on the cooperation of participating nodes for almost all their functions. However, due to resource constraints, nodes are generally selfish and try to maximize their own benefit when participating in the network. Therefore, it is important to study mechanisms which can be used as incentives to form coalitions inside the network. In this paper, we study coalition formation based on game theory, especially cooperative game theory. First, the dynamics of coalition formation proceeds via pairwise bargaining. We show that the size of the maximum coalition is a decreasing function of the cost for establishing a link. After the coalition formation process reaches the steady state, we are interested in the stability of coalitions. We prove that coalitions are stable in terms of both pairwise stability and coalitional stability.},
	address = {Orlando, FL},
	booktitle = {25th Army Science Conference}
}
@conference {
	title = {A Stochastic Algorithm for Self-Organization of Autonomous Swarms},
	author = {Xi, Wei., Tan, Xiaobo., Baras, John S.},
	year = {2005},
	month = {12/2005},
	abstract = {In earlier work of the authors simulation results indicated the possibility of achieving self-organization of autonomous vehicles through Gibbs sampler-based simulated annealing. However, the dynamic graph structure associated with the network evolution presents challenges in convergence analysis. In this paper a novel algorithm is presented and shown to yield desired global configurations with primarily local interactions. Its convergence speed is provided in terms of the Gibbs potential function. The analytical results are further verified through simulation.},
	address = {Seville, Spain},
	booktitle = {44th IEEE Conference on Decision and Control and the European Control Conference (CDC-ECC {\textquoteright}05)},
	pages = {pp. 765-770}
}
@conference {
	title = {Maximum Entropy Models, Dynamic Games, and Robust Output Feedback Control for Automata},
	author = {Baras, John S., Rabi, Maben.},
	year = {2005},
	month = {12/2005},
	abstract = {In this paper, we develop a framework for designing controllers for automata which are robust with respect to uncertainties. A deterministic model for uncertainties is introduced, leading to a dynamic game formulation of the robust control problem. This problem is solved using an appropriate information state. We derive a Hidden Markov Model as the maximum entropy stochastic model for the automaton. A risk-sensitive stochastic control problem is formulated and solved for this Hidden Markov Model. The two problems are related using small noise limits.},
	address = {Seville, Spain},
	booktitle = {44th IEEE Conference on Decision and Control and the European Control Conference (CDC-ECC {\textquoteright}05)},
	pages = {pp.1043-1049}
}
@conference {
	title = {Iterative Dynamics on Graphs with Variable Topology},
	author = {Baras, John S.},
	year = {2005},
	month = {12/2005},
	address = {New Haven, CT},
	organization = {Yale University}
}
@conference {
	title = {A Multiple Subset Sum Formulation for Feedback Implosion Suppression over Satellite Networks},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2005},
	month = {11/2005},
	abstract = {In this paper, we present a feedback implosion suppression (FIS) algorithm that reduces the volume of feedback information transmitted through the network without relying on any collaboration between users, or on any infrastructure other than the satellite network. Next generation satellite systems that utilize the Ka frequency band are likely to rely on various fade mitigation techniques, in order to guarantee a service quality that is comparable to other broadband technologies. User feedback would be a valuable input for a number of such components, however, collecting periodic feedback from a large number of users would result in the well-known feedback implosion problem. Feedback implosion is identified as a major problem when a large number of users try to transmit their feedback messages through the network, holding up a significant portion of the uplink resources and clogging the shared uplink medium. In this paper, we look at a system where uplink channel access is organized in time-slots. The goal of the FIS algorithm is to reduce the number of uplink time-slots hold up for the purpose of feedback transmission. Our analysis show that the FIS algorithm effectively suppresses the feedback messages of 95\% of all active users, but still achieves acceptable performance results when the ratio of available time-slots to number of users is equal to or higher than 5\%.},
	address = {St. Louis, MO},
	booktitle = {Globecom 2005 Wireless Communications},
	pages = {pp. 3226-3230}
}
@conference {
	title = {An Authentication Framework for Hybrid Satellite Network with Resource-Constrained Nodes},
	author = {Roy-Chowdhury, Ayan., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2005},
	month = {11/2005},
	abstract = {The new phase of space exploration involves a growing number of human and robotic space missions to remote planets with varying communication and service requirements. Due to the critical nature of the missions, security is a very important requirement that needs to be addressed. Among primary security requirements are user authentication and message integrity that are needed to ensure that the data in the network is transmitted without unauthorized modifications between the source and destinations, and that data from only authorized network nodes are accepted by other nodes. In this paper we focus on the issue of user authentication and data integrity for a specific space network architecture supporting lunar exploration. We consider a hybrid network consisting of a terrestrial network on Earth, a network on the lunar surface, and a satellite constellation that connects the two surface networks. The lunar network comprises sensor nodes serviced by stationary gateways and mobile robotic vehicles with sensing capability, while the network on Earth is envisioned as a combination of private and public networ:ks. The problem of authentication in this network is co~plex due to the presence of nodes with varying capabilities in terms of computation strength, storage and energy. The nodes on .Earth and the gatewayso n the lunar surfacew ould have higher computationa nd energyc apabilitiesc omparedto the satellites and the sensor nodes. In this situation, an authentication protocol that is optimized to the strengths and limitations of the different classeso f nodesw ould be most suited. We focus on a solution that will operate under the constraints of the space environment (delay, limited energy, limited processing capability at remote nodes). We present a framework for user authentication and data integrity based on an authentication algorithm that makes use of symmetric certificates and hash chains of keys used to compute Message Authentication Codes,to provide asymmetric authentication capabilities to the network nodes. nodes with more resources. We give a detailed description of the authentication protocol we develop for this network and p~ovide an analysis of the security of the protocol by considering various types of passive and active attacks. We also highlight the savings incurred in terms of processing, storage and network bandwidth, which we get in using the proposed protocol in comparison to standard public-key authentication protocols.},
	address = {Wuhan, China},
	booktitle = {International Conference on Spatial Information Technology (ICSIT 2005)},
	pages = {pp. 1-12}
}
@conference {
	title = {Component Based System Synthesis},
	author = {Baras, John S.},
	year = {2005},
	month = {11/2005},
	address = {Washington DC},
	booktitle = {NSF ERC Annual Meeting, Panel on {\textquotedblleft}Strategies for Integration: Optimizing the Systems Focus in ERCs{\textquotedblright}}
}
@conference {
	title = {Collaborative Networked Control: Stochastic Algorithms},
	author = {Baras, John S.},
	year = {2005},
	month = {10/2005},
	address = {Philadelphia, Pennsylvania},
	organization = {GRASP Laboratory, University of Pennsylvania}
}
@conference {
	title = {Design Framework for Hierarchy Maintenance Algorithms in Mobile Ad Hoc Networks},
	author = {Manousakis, Kyriakos., Baras, John S., McAuley, Anthony J., Morera, Raquel.},
	year = {2005},
	month = {10/2005},
	abstract = {Domain autoconfiguration techniques allow the quick formation of highly optimized hierarchies that greatly enhance network scalability and overall performance. For example, instead of producing a simple two level hierarchy based only on topology, the optimization can produce multi-level hierarchies that take into account factors such as mission goals and predicted node/link heterogeneity. However, in dynamic networks, such as expected in the future military networks, these highly optimized solutions degrade very quickly. Indeed, if we use standard local maintenance algorithms that do not align well with the optimization goals, then the performance can reach the level of a suboptimal solution in less than two minutes. This paper proposes a taxonomy of local maintenance algorithms into four basic classes and quantifies the performance benefits of using representative approaches that act in accordance with the optimization goals.},
	address = {Atlantic City, NJ},
	booktitle = {2005 IEEE Military Communications Conference (MILCOM)},
	pages = {pp. 1-6}
}
@conference {
	title = {Domain Based Heirarchical Routing for Large Heterogeneous Manets},
	author = {Chandrashekar, Karthikeyan., Morera, Raquel., McAuley, Anthony J., Baras, John S.},
	year = {2005},
	month = {10/2005},
	abstract = {This paper proposes a domain based hierarchical routing for large ad hoc networks. Our approach is based on auto-configured optimized routing domains and an enhanced inter-domain routing scheme. The large heterogeneous ad-hoc network is divided into more scalable homogeneous domains where each domain can run the routing protocol that best suits its link and traffic characteristics. We here propose an inter-domain routing protocol that exploits existing messages needed to maintain the domain structure. To support heterogeneity, the inter-domain routing scheme is independent of the routing protocols running in each domain. We compare three different approaches to the inter-domain routing: a) based solely on the propagation of domain messages, b) border node based, c) dynamic border node. In this paper, OPNET simulations compare the performance of the different inter-domain routing schemes and show the benefits of the proposed approach using OLSR and DSR as intra-domain routing protocols. Results show significant reduction in protocol overhead, increased route stability and increased route availability in a dynamic heterogeneous network. It is worth mentioning that the increased route stability is not only given by the isolation of more mobile nodes from the rest in a single domain, but also by limiting the cross-layer interactions (e.g. as the routing overhead increases, collisions at the MAC layer increase and therefore more routing packets get lost).},
	address = {Atlantic City, NJ},
	booktitle = {2005 IEEE Military Communications Conference (MILCOM)},
	pages = {pp. 1284-1290}
}
@conference {
	title = {Hybrid Networks with a Space Segment - Topology Design and Security Issues},
	author = {Roy-Chowdhury, Ayan., Baras, John S., Hadjitheodosiou, Michael., Rentz, Nicolas.},
	year = {2005},
	month = {10/2005},
	abstract = {In this paper we investigate a hybrid network topology that is suitable for supporting interplanetary communications. We define an architecture comprised of a network of sensor nodes on a remote planetary surface, connected to a hybrid terrestrial network of wired and wireless LANs through a series of satellite relays. All the nodes in the network are IP-addressable and support public and symmetric key cryptography. The resulting network forms a hierarchical hybrid mesh that connects users on Earth to networks on or around a remote planetary surface. We describe the design of the network and present preliminary simulation results illustrating the network performance for various parameters. We also discuss how algorithms for user authentication, message integrity and data confidentiality can be incorporated in the network infrastructure for secure end-to-end communication.},
	address = {Atlantic City, NJ},
	booktitle = {2005 Military Communications Conference (MILCOM 2005),},
	pages = {pp.1414 - 1420}
}
@conference {
	title = {Swarm Collaborative Intelligence: From Networked Control to Trust in MANET},
	author = {Baras, John S.},
	year = {2005},
	month = {10/2005},
	address = {Chania, Crete},
	organization = {Technical University of Crete}
}
@conference {
	title = {Modeling and Design of a Communication Architecture Supporting Lunar Exploration},
	author = {Roy-Chowdhury, Ayan., Hadjitheodosiou, Michael., Baras, John S., Rentz, Nicolas.},
	year = {2005},
	month = {09/2005},
	abstract = {We discuss some basic requirements and trade-offs for designing a communication network supporting the needs of lunar exploration missions. We describe the unique characteristics of this network and outline a prototype network architecture. The proposed network consists of three distinct segments - a terrestrial network on Earth, a network on the lunar surface, and a space segment comprising a satellite constellation that connect the two surface networks.~We develop a simulation platform that includes the network topology, node orbits and mobility, and test the network performance with different applications and traffic loads. We present simulation results obtained with our models that illustrate the network connectivity and delay for varying satellite orbital patterns and traffic characteristics. We also discuss the requirements and constraints for providing a secure infrastructure for end-to-end communication in space exploration networks~and suggest algorithms and protocols for implementing end-to-end encryption, authentication and secure group communication.},
	address = {Rome, Italy},
	booktitle = {23rd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)},
	pages = {pp. 1-10}
}
@conference {
	title = {Integrated Packet Level FEC Coding for Bulk Data Transfer Over Satellite Network},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2005},
	month = {09/2005},
	abstract = {Packet level forward error correction (FEC) coding has been widely accepted as an efficient way of reducing the number of retransmissions and recovering from packet losses for reliable multicast in satellite networks. While there has been a significant effort in defining packet level FEC schemes that detail the structure, organization and delivery of the encoding packets, little attention has been given to how the physical channel, channel coding, and the downlink power budget affect the design space of these schemes in the context of a satellite network architecture. In this paper, we take a step in this direction, and define the points of interaction between various components and build a simulation environment. Using this simulation setup, we provide design suggestions for integrating FEC coding into reliable multicast transport protocols.},
	address = {Rome, Italy},
	booktitle = {23rd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)}
}
@conference {
	title = {AeroTCP: A Splitting Transport Protocol for an IP-based Satellite Network Supporting Aeronautical Communications},
	author = {Shang, Yadong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2005},
	month = {09/2005},
	abstract = {The IP-based Broadband Aeronautical Satellite Network will provide numerous new applications and services for both airspace system operations and passenger communications. However, the performance of data communications protocols and applications over such systems is dramatically degraded, especially the Internet TCP/IP protocol suite. In this paper, we propose a new transport protocols for satellite network supporting Internet and data services. Based on the observation that it is difficult for an end to- end TCP solution to solve the performance problem effectively, we propose a new splitting based TCP protocol, called Aeronautical Transport Control Protocol (AeroTCP), which takes advantage of the specific properties of satellite channel. Our simulation results show that AeroTCP improves satellite channel utilization and fairness.},
	address = {Rome, Italy},
	booktitle = {23rd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)}
}
@conference {
	title = {Dynamic Resource Allocation for an IP-based Communications Network Supporting Space Exploration},
	author = {Zeng, Hui., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2005},
	month = {09/2005},
	abstract = {We address issues related to efficiency, fairness, end-to-end delay minimization and Quality-of-Service (QoS) framework in order to enable a flexible access and dynamic mission operation capability in the next generation NASA space-to-ground IP-based communication infrastructure. In our scenario, the downlink channel of the NASA Tracking and Data Relay Satellite System is shared by a number of spacecraft, which we model as streams with different priority levels going through a common queue and a router. Both the current and future potential architectures for this relay system are addressed. We formulate an optimization problem for long-term static bandwidth allocation and present its solution to serve as initial bandwidth allocation algorithm and periodical regulation approach. Along with it, a hybrid Time Division Multiple Access (TDMA)-based protocol is proposed and then an assignment problem for the short-term dynamic optimal timeslot scheduling is studied. By using simulation, the performance of a suitable Medium Access Control (MAC) protocol with timeslot scheduling is analyzed and compared with that of the existing static fixed-assignment scheme.},
	address = {Rome, Italy},
	booktitle = {23rd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)},
	pages = {pp. 1-12}
}
@conference {
	title = {bufSTAT - A Tool for Early Detection and Classification of Buffer Overflow Attacks},
	author = {Radosavac, Svetlana., Seamon, Karl., Baras, John S.},
	year = {2005},
	month = {09/2005},
	abstract = {Buffer overflows constitute by far the most frequently encountered class of attacks against computer systems. In this paper we introduce a tool, termed bufSTAT that achieves a low probability of false alarm and issues early attack warnings. BufSTAT relies on Finite State Machines (FSM) for attack modeling and can detect every stage of an ongoing attack and can thus prevent its execution by issuing early warning in a progressive manner. It can also detect sophisticated multi-stage attacks that are executed over long periods of time. A significant attribute of our approach is that it is amenable to detecting unknown attacks as well after appropriate modification of bufSTAT.},
	address = {Athens, Greece},
	booktitle = {First International Conference on Security and Privacy for Emerging Areas in Communication Networks}
}
@conference {
	title = {A Framework for MAC Protocol Misbehavior Detection in Wireless Networks},
	author = {Radosavac, Svetlana., Baras, John S., Koutsopoulos, Iordanis. },
	year = {2005},
	month = {09/2005},
	abstract = {The pervasiveness of wireless devices and the architectural organization of wireless networks in distributed communities, where no notion of trust can be assumed, are the main reasons for the growing interest in the issue of compliance to protocol rules. Reliable and timely detection of deviation from legitimate protocol operation is recognized as a prerequisite for ensuring efficient and fair use of network resources and minimizing performance losses. Nevertheless, the random nature of protocol operation together with the inherent difficulty of monitoring in the open and highly volatile wireless medium poses significant challenges. In this paper, we consider the fundamental problem of detection of node misbehavior at the MAC layer. Starting from a model where the behavior of a node is observable, we cast the problem within a minimax robust detection framework, with the objective to provide a detection rule of optimum performance for the worst-case attack. The performance is measured in terms of required number of observations in order to derive a decision. This framework is meaningful for studying misbehavior because it captures the presence of uncertainty of attacks and concentrates on the attacks that are most significant in terms of incurred performance losses. It also refers to the case of an intelligent attacker that can adapt its policy to avoid being detected. Although the basic model does not include interference, we show that our ideas can be extended to the case where observations are hindered by interference due to concurrent transmissions. We also present some hints for the problem of notifying the rest of the network about a misbehavior event. Our work provides interesting insights and performance bounds and serves as a prelude to a future study that would capture more composite instances of the problem.},
	address = {Cologne, Germany},
	booktitle = {4th ACM Workshop on Wireless Security,},
	pages = {pp. 33-42}
}
@conference {
	title = {Swarm Collaborative Intelligence: From Networked Control to Trust in MANET},
	author = {Baras, John S.},
	year = {2005},
	month = {08/2005},
	address = {Napa Valley, CA},
	booktitle = {Workshop on Swarming in Natural and Engineered Systems}
}
@conference {
	title = {Solving Optimal Neural Layout by Gibbs Sampling},
	author = {Jiang, Tao., Xu, Peng., Abshire, Pamela A., Baras, John S.},
	year = {2005},
	month = {07/2005},
	abstract = {Neural systems of organisms derive their functionality largely from the numerous and intricate connections between individual components. These connections are costly and have been refined via evolutionary pressure that acts to maximize their functionality while minimizing the associated cost. This tradeoff can be formulated as a constrained optimization problem. In this paper, we use simulated annealing, implemented through Gibbs sampling, to investigate the minimal cost placement of individual components in neural systems. We show that given the constraints and the presumed cost function associated with the neural interconnections, we can find the configuration corresponding to the minimal cost. We restrict the mechanisms considered to those involving incremental improvement through local interactions since real neural systems are likely to be subject to such constraints. By adjusting the cost function and comparing with the actual configuration in neural systems, we can infer the actual cost function associated with the connections used by nature. This provides a powerful tool to biologists for investigating the configurations of neural systems.},
	address = {Salt Lake City, Utah},
	booktitle = {8th Joint Conference on Information Sciences 2005 (JCIS 2005 in conjunction with the 7th International Conference on Computational Intelligence and Natural Computation 2005, CINC)},
	pages = {pp. 424-427}
}
@conference {
	title = {Wireless Sensor Networks and Applications},
	author = {Baras, John S.},
	year = {2005},
	month = {07/2005},
	address = {Athens, Greece},
	organization = {Athens Agricultural University}
}
@conference {
	title = {Distributed Stochastic Coordination Algorithms for Autonomous Vehicle Control},
	author = {Baras, John S.},
	year = {2005},
	month = {07/2005},
	address = {New Orleans},
	booktitle = {Cooperative Control Mini-Symposium, 2005 SIAM Conference on Control Theory and Applications}
}
@conference {
	title = {Gibbs Sampler-Based Path Planning for Autonomous Vehicles: Convergence analysis},
	author = {Xi, Wei., Tan, Xiaobo., Baras, John S.},
	year = {2005},
	month = {07/2005},
	abstract = {Simulation has indicated that distributed self-organization of autonomous swarms might be achieved through Gibbs sampler-based simulated annealing. However, the dynamic nature of the underlying graph presents significant challenges in convergence analysis. As a first step toward such analysis, convergence of the algorithm is established in this paper for two special cases: single vehicle with limited sensing/moving range, and multiple vehicles with full sensing/moving range. The impact of Gibbs potential functions on the convergence speed is also investigated, which provides insight into the design of these functions.},
	address = {Prague, Czech Republic},
	booktitle = {IFAC 2005}
}
@conference {
	title = {Teaching System-Level Thinking at the Undergraduate Level: A Proposal for Fundamental Changes in Systems, Control, Communication and Computing Instruction},
	author = {Baras, John S.},
	year = {2005},
	month = {06/2005},
	address = {Limassol, Cyprus},
	booktitle = {Joint ISIC{\textquoteright}05 and MED{\textquoteright}05 Conferences}
}
@conference {
	title = {Mobility Based Distributed Domain Generation Algorithm for MANETs},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2005},
	month = {06/2005},
	abstract = {Ad hoc networks are very important for scenarios where there is not fixed network infrastructure. These scenarios may appear both in the military and the commercial world. Even though there is much advancement in the area of these networks, they do not scale well. This is due to the inability of the existing protocols (e.g., MAC, routing, security) to tolerate the dynamics of these networks when their size becomes large. A remedy is to apply these protocols in a hierarchical manner. The hierarchy generation in these dynamic environments can be advantageous since the network appears to be smaller due to the aggregation and abstraction resulted from the grouping of nodes. The numerous topological changes can be tolerated easier and the applied protocols can perform better. This division greatly reduces overall overhead (e.g., routing overhead with n nodes goes from O(n2) to O(nlogn)) and allows protocols to be tuned to more homogenous conditions). On the other hand, hierarchy has to be generated carefully in order to be beneficial for the network otherwise, it may harm it, due to the imposed maintenance overhead. Towards this objective we have to take into consideration the network environment and design appropriately the hierarchy generation algorithms. In this paper, we present a mobility based domain generation algorithm (DGA), which in a distributed manner attempts to exploit similarities in the mobility patterns of the participating nodes by utilizing a set of mobility metrics. By grouping together nodes with similar mobility characteristics, the mobility based DGA targets the generation of robust to mobility hierarchical structures. The algorithm presents better scalability and robustness characteristics from well known existing distributed domain generation algorithms.},
	address = {Maui, Hawaii},
	booktitle = {2005 International Conference on Wireless Networks, Communications and Mobile Computing},
	pages = {pp. 820-825}
}
@conference {
	title = {Analysis of Delay Properties and Admission Control in 802.11 Networks},
	author = {Raissi-Dekhordi, Majid., Chandrashekar, Karthikeyan., Baras, John S.},
	year = {2005},
	month = {06/2005},
	abstract = {The ubiquitous use of 802.11 wireless networks highlights the importance of understanding the performance of the 802.11 protocol, specifically its delay properties which is the key to sustaining delay sensitive applications over such networks. In this paper, analytical expressions are derived for the channel access delay distribution of 802.11 networks. An implicit admission control scheme is proposed that uses the channel service time distribution as input to determine the maximum number of users that can be admitted. The analytical expressions for the delay are shown to closely match simulation results. We analyze the performance of the admission control scheme and calculate the saturation throughput for the admitted user. Simulation results validate the effectiveness of the admission control scheme and the analytical results.},
	address = {Maui, Hawaii},
	booktitle = {2005 International Conference on Wireless Networks, Communications and Mobile Computing},
	pages = {pp. 674-679}
}
@conference {
	title = {A Hybrid Scheme for Distributed Control of Autonomous Swarms},
	author = {Xi, Wei., Tan, Xiaobo., Baras, John S.},
	year = {2005},
	month = {06/2005},
	abstract = {In this paper, a hybrid scheme for distributed control of autonomous vehicles is presented by combining the deterministic gradient-flow method and the stochastic method based on the Gibbs sampler. The scheme has the advantages of both methods and can potentially provide fast, distributed maneuvers while avoiding getting trapped at local minima of the potential function. Preliminary analysis is performed for the optimal design of the parameters controlling the switching between the two methods. The performance of the hybrid scheme is further enhanced by the introduction of vehicle memory. Simulation results are provided to confirm the analysis and show the effectiveness of the proposed algorithm.},
	address = {Portland USA},
	booktitle = {American Control Conference},
	pages = {pp. 3486-3491}
}
@conference {
	title = {Cooperation, Trust and Games in Wireless Networks},
	author = {Baras, John S., Jiang, Tao.},
	year = {2005},
	month = {06/2005},
	abstract = {As an important concept in network security, trust is interpreted as a set of relations among agents participating in the network activities. Trust relations are based on the previous behavior of an agent within a protocol. Trust establishment in distributed and resource-constraint networks, such as mobile ad hoc networks (MANETs), sensor networks and ubiquitous computing systems, is much more difficult but more crucial than in traditional hierarchical architectures, such as the Internet and base station- or access point-centered wireless LANs. Generally, this type of distributed networks have neither pre-established infrastructures, nor centralized control servers or trusted third parties (TTP). The trust information or evidence used to evaluate trustworthiness is provided by peers, i.e. the agents that form the network. Furthermore, resources (power, bandwidth, computation etc.) are normally limited because of the wireless and ad hoc environment, so the trust evaluation procedure should only rely on local information. Schemes that depend only on local interaction also have the desired emergent property that enables fast reaction to network member changes, topology changes and security changes that frequently happen in mobile networks. Therefore, the essential and unique properties of trust management in this new paradigm of wireless networking, as opposed to traditional centralized approaches are: uncertainty and incompleteness of trust evidence, trust value is between -1 and 1; locality in trust information exchange; distributed computation.},
	address = {Berkeley, CA},
	booktitle = {.Symposium on Systems, Control and Networks}
}
@conference {
	title = {Hybrid Wireless Networks Design, Performance Evaluation and Management},
	author = {Baras, John S.},
	year = {2005},
	month = {06/2005},
	address = {Los Angeles, CA},
	organization = {The Boeing Company}
}
@conference {
	title = {A Systems Engineering Perspective to Cross-Layer Design and Optimization with Applications to Wireless Information Assurance},
	author = {Baras, John S.},
	year = {2005},
	month = {05/2005},
	address = {Rome, NY},
	organization = {Air Force Rome Laboratory}
}
@article {
	title = {Control of Hysteresis in Smart Actuators with Application to Micro-Positioning},
	author = {Tan, Xiaobo., Baras, John S., Krishnaprasad, P S.},
	year = {2005},
	month = {05/2005},
	abstract = {Hysteresis in smart material actuators makes the effective use of these actuators quite challenging. The Preisach operator has been widely used to model smart material hysteresis. Motivated by positioning applications of smart actuators, this paper addresses the value inversion problem for a class of discretized Preisach operators, i.e., to find an optimal input trajectory given a desired output value. This problem is solved through optimal state transition of a finite state machine (FSM) that corresponds to the discretized Preisach operator. A state-space reduction scheme for the FSM is developed, which significantly saves the memory and the computation time. Experimental results on micro-positioning control of a magnetostrictive actuator are presented to demonstrate the effectiveness of the proposed approach.},
	pages = {pp. 483-492},
	volume = {Volume 54},
	number = {Issue 5},
	journal = {Systems \&amp; Control Letters}
}
@conference {
	title = {Trust in Self-organized Mobile Ad Hoc Networks},
	author = {Baras, John S.},
	year = {2005},
	month = {03/2005},
	address = {Volos, Greece},
	booktitle = {Invited Seminar, University of Thessaly}
}
@conference {
	title = {Autonomous Trust Establishment},
	author = {Jiang, Tao., Baras, John S.},
	year = {2005},
	month = {03/2005},
	abstract = {Trust establishment in networks is the essential foundation for follow-on security mechanisms, such as key management and secure transmission. In this paper, we concentrate on self-organized, distributed and resource-constraint networks which pose formidable challenges on trust establishment due to lack of infrastructure and centralized servers. We model our trust establishment strategy as a local voting scheme and discuss its long run behavior. More specifically, we investigate the dynamic evolution of trust within the network, i.e. how trust spreads among nodes, via analyzing its convergence behavior. By theoretical analysis based on graph theory, we also find the conditions under which trust spreads to a maximum set of nodes and parameters that speed up or slow down this transition.},
	address = {Lisbon, Portugal},
	booktitle = {2nd International Network Optimization Conference},
	pages = {pp. 1-8}
}
@conference {
	title = {A Multichannel Random Access Protocol for Multislot Short Messages with Delay Constraints},
	author = {Zhou, Xiaoming., Baras, John S.},
	year = {2005},
	month = {03/2005},
	abstract = {A multichannel random access protocol called FMCSA for multislot short messages is proposed in this paper to be used in access networks with large propagation delay. This protocol combines random access with the use of packet level forward error correction coding for new messages and scheduled retransmissions for partially received messages. Analytical and simulation results show that FMCSA can achieve a higher throughput and lower delay than slotted Aloha. When the system is operating in the low load region, the short messages can be delivered in their first attempts with very high probability. With the load increasing, more messages will be received partially in their first attempts and the scheduled retransmission scheme will guarantee the partially received messages to be recovered in their second attempts. Therefore the delay performance of FMCSA is much more robust to the load fluctuation than slot Aloha.},
	address = {Miami, Florida},
	booktitle = {INFOCOM 2005}
}
@conference {
	title = {Complex Engineering Systems},
	author = {Baras, John S.},
	year = {2005},
	month = {03/2005},
	address = {Arlington, VA},
	booktitle = {NSF Workshop {\textquotedblleft}From Macro to Nano: Challenges and Opportunities in Integrative Complex Systems Engineering{\textquotedblright}}
}
@conference {
	title = {Managing Trust in Self-organized Mobile Ad Hoc Networks},
	author = {Baras, John S.},
	year = {2005},
	month = {02/2005},
	address = {Athens, Greece},
	booktitle = {Invited Seminar, National Technical University of Athens},
	organization = {University of Athens}
}
@conference {
	title = {Managing Trust in Self-organized Mobile Ad Hoc Networks},
	author = {Baras, John S.},
	year = {2005},
	month = {02/2005},
	address = {San Diego, CA},
	booktitle = {Wireless and Mobile Security Workshop, part of NDSS 2005}
}
@conference {
	title = {Cooperative Games, Phase Transitions on Graphs and Distributed Trust in MANET},
	author = {Baras, John S., Jiang, Tao.},
	year = {2004},
	month = {12/2004},
	abstract = {Mobile ad-hoc networks (MANET) provide a relative new paradigm of wireless networking, which poses several formidable challenges for control, monitoring and management, due to the basically "infrastructureless" nature of these networks. Security is viewed in this paper as part of the control-operations-management functionality of MANET. An important and critical part of security is trust establishment and maintenance. We provide a description of distributed trust within the MANET framework that consists of two major components: (a) trust document distribution; and (b) distributed trust computation. Within (a) we summarize our earlier work on swarm-intelligence based trust document distribution schemes, including their major advantages as compared to other schemes as well as their performance. This paper is primarily addressing our new results within (b). Here we show that under a variety of schemes for distributed trust computation and establishment we have established strong connections with various components of the theory of random graphs. In this context we demonstrate how phase transitions (in this case they mean node transitions from nontrusted to trusted) can appear within a MANET. We link the existence and analysis of such phase transitions to dynamic cooperative games. We demonstrate that dynamic cooperative games provide a natural framework for analyzing several problems for MANET. We also demonstrate the fundamental influence of the topology of the MANET on these phase transitions. Finally we conclude with a preliminary description of results that describe the effects of mobility and topology change on these trust establishment schemes.},
	address = {Atlantis, Paradise Island, Bahamas},
	booktitle = {43rd IEEE Conference on Decision and Control,},
	pages = {pp. 93-98}
}
@conference {
	title = {Control of Autonomous Swarms Using Gibbs Sampling},
	author = {Baras, John S., Tan, Xiaobo.},
	year = {2004},
	month = {12/2004},
	abstract = {A distributed control approach is proposed for self-organization of autonomous swarms. The swarm is modeled as a Markov random field (MRF) on a graph where the (mobile) nodes and their communication/sensing links constitute the vertices and the edges of the graph, respectively. The movement of nodes is governed by the Gibbs sampler. The Gibbs potentials, local in nature, are designed to reflect collective goals such as gathering, dispersion, and linear formation. The algorithm can be run completely in parallel, and hence it is robust and scalable. Simulation results are provided to illustrate the proposed method.},
	address = {Atlantis, Paradise Island, Bahamas},
	booktitle = {43rd IEEE Conference on Decision and Control},
	pages = {pp. 4752-4757}
}
@conference {
	title = {Numerical Study on Joint Quantization and Control Under Block-Coding},
	author = {Tan, Xiaobo., Xi, Wei., Baras, John S.},
	year = {2004},
	month = {12/2004},
	abstract = {This paper addresses the joint quantization and control problem for hidden Markov chains with variable-length block-coding. The aim is to understand the impact of communication bandwidth and information delay (due to block-coding) on the control performance. A heuristic algorithm is developed to solve the dynamic programming (DP) equation through the introduction of a metric on the discrete observation space. Numerical results are presented demonstrating the attention division in block-coding and the tradeoffs between control performance and communication bandwidth.},
	address = {Atlantis, Paradise Island, Bahamas},
	booktitle = {43rd IEEE Conference on Decision and Control},
	pages = {pp. 4515-4520}
}
@conference {
	title = {Sampling of Diffusion Processes for Real-Time Estimation},
	author = {Rabi, Maben., Baras, John S.},
	year = {2004},
	month = {12/2004},
	abstract = {This paper addresses the causal sampling of observations of a diffusion process that results in a good quality continuous estimator based upon these samples. The optimal sampling scheme with a fixed number of samples is found by solving an optimal (multiple) stopping problem. This is solved explicitly in a special case. A class of threshold approximations is also described.},
	address = {Atlantis, Paradise Island, Bahamas},
	booktitle = {43rd IEEE Conference on Decision and Control},
	pages = {pp. 4163-4168}
}
@conference {
	title = {Distributed Certification Authority Generation to Enhance Autonomous Key Management for Group Communications in MANETs},
	author = {Striki, Maria., Baras, John S.},
	year = {2004},
	month = {11/2004},
	abstract = {A MANET is a collection of wireless mobile nodes dynamically forming a temporary network, without the use of fixed infrastructure or centralized entities, and this is exactly the environment envisioned for military operations by the Objective Force. Military command and control rely on secure (multicast) communications, and thus key management (KM) schemes that ensure secure communications under MANET constraints are required. However, without fixed infrastructure, e.g. trusted third parties (TTPs), Certification Authorities (CAs), the design of KM becomes particularly difficult, since its most fundamental service {\textendash} entity authentication, privileges update/revocation - rely on these entities to establish trust among nodes, terminate or renew participation to secure operations in a pre-agreed, global manner. Without this guarantee, all subsequent KM operations make no sense. So, it is of paramount importance to provide a secure authentication service that detects misbehavior and defends against dishonest users in the network. Thus, the challenge lies in dynamically generating mechanisms that provide individual nodes and KM groups with functionalities similar to those of the original CAs of fixed infrastructure, under MANET constraints. In this work, we develop distributed, scalable, robust and efficient mechanisms for dynamically generating CAs in MANETs, by distributing the tasks of a CA among legitimate members of existing (preferably hierarchical) KM groups. We will show how the features of our scheme render it superior in performance and resilience and how properties of KM groups are exploited to avoid impractical heavy bandwidth-delay solutions of other proposals in the literature.},
	address = {Orlando, Florida},
	booktitle = {24th Army Science Conference (ASC2004)}
}
@conference {
	title = {Measurement and Simulation Based Effective Bandwidth Estimation},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {11/2004},
	abstract = {Effective bandwidth represents the resource demand for network traffic to achieve its QoS goal. However, so far, the estimation of the effective bandwidth for modern Internet traffic has been difficult and inaccurate. We present a novel scheme using measurement and simulation techniques to estimate the effective bandwidth. The advantages of the scheme lie in its accuracy, its applicability to various traffic environments, and its efficiency. We describe the simulation procedure, the efficient search algorithm to lock the effective bandwidth quickly, the sample size determination algorithm, and the performance judgment policy in the simulation to guarantee the estimation accuracy. We also examine the issue of estimating the effective bandwidth of aggregate traffic from sub-aggregates, and provide an empirical formula to achieve very good accuracy.},
	address = {Dallas, TX},
	booktitle = {GLOBECOM 04},
	pages = {pp. 2108-2112}
}
@conference {
	title = {Improving the~ Speed of Dynamic Cluster Formation in Manet~ via Simulated~ Annealing},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2004},
	month = {11/2004},
	abstract = {Future military systems, such as FCS, require a robust and flexible network that supports thousands of ad hoc nodes. Therefore, networking protocols for MANETs must be made to scale. The use of hierarchy is a powerful general solution to the scaling problem. We have previously proposed methods based on Simulated Annealing (SA) to optimize hierarchy in MANETs. The challenge, however, is to improve the slow convergence time of SA, so it can be used in dynamic environments, without penalizing optimality. In previous work, the importance of parameters such as cooling schedule, state transition probabilities, and convergence condition are investigated. This paper proposes a new approach to decrease SA convergence time. SA is an optimization technique based on an iterative process that takes an initial solution, or map, to start the process. In this paper, we analyze the effect that this initial solution has on the SA convergence time as a function of the network size. We believe that the combined modifications to SA can speed the optimization process to the point that it can quickly generate very efficient clustering solutions in large dynamic networks.},
	address = {Orlando, Florida},
	booktitle = {24th Army Science Conference (ASC2004)},
	pages = {pp. 1-8}
}
@conference {
	title = {Rate of Degradation of Centralized Optimization Solutions and its Application to High Performance Domain Formation in Ad Hoc Networks},
	author = {Manousakis, Kyriakos., Baras, John S., McAuley, Anthony J., Morera, Raquel.},
	year = {2004},
	month = {10/2004},
	abstract = {Future military systems such a FCS and WIN-T require a robust and flexible network that supports thousands of ad hoc nodes; therefore, we must ensure the scalability of networking protocols (e.g., routing, security and QoS). The use of hierarchy is a powerful solution to the scaling problem~since it allows networking protocols to operate on a limited number of nodes, as opposed to the entire network. We have proposed an automated solution to dynamically create and maintain such hierarchy based on a combination of global optimization algorithms and local distributed maintenance protocols. Global optimization clearly improves performance in a static network but, it is unclear how effective it is in a dynamic ad hoc environment. In this paper, we analyze how the hierarchy created deteriorates from the optimal as network conditions change. We show that the fragility of the optimization depends on the particular cost function and the number of metrics that change. More important, we show, for the first time, that global optimization can remain effective for long periods with good cost functions, even in large dynamic ad hoc networks (where metrics may change rapidly due to node mobility and links making and breaking).~This result shows that, with fast optimization algorithms such as modified Simulated Annealing, future military systems can use global optimization to autoconfigure domains to significantly improve perform". We also show that local maintenance protocols support the global optimization mechanisms by extending the time the hierarchy remains feasible.},
	address = {Monterey, California},
	booktitle = {MILCOM 2004},
	pages = {pp. 1536-1542}
}
@conference {
	title = {Providing Full Connectivity in Large Ad-Hoc Networks by Dynamic Placement of Aerial Platforms},
	author = {Chandrashekar, Karthikeyan., Raissi-Dekhordi, Majid., Baras, John S.},
	year = {2004},
	month = {10/2004},
	abstract = {In this paper, we address the problem of providing full connectivity to disconnected ground MANET nodes by dynamically placing unmanned aerial vehicles (UAVs) to act as relay nodes. We provide a heuristic algorithm to find the minim1 number of such aerial vehicles required to provide full connectivity and find the corresponding locations for these aerial platforms (UAVs). We also track the movement of the ground nodes and update the location of the UAVs. We describe a communication framework that enables the ground nodes to communicate with its peer ground nodes as well as the UAVs that act as relay nodes. The communication architecture is designed to work with existing MANET Routing Protocols.},
	address = {Monterey, California},
	booktitle = {MILCOM 2004},
	pages = {pp. 1429-1436}
}
@conference {
	title = {Capability Assessment and Design Evaluation for the Hybrid Network of Space GiG and Terrestrial Sensor Nets: Global Monitoring, Tracking and Query},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {10/2004},
	abstract = {In this paper, we propose a hierarchical architecture for organizing the hybrid network of the LEO-satellite based space network and terrestrial sensor nets. The hybrid network has unique advantages in providing global monitoring, tracking, and query capabilities. We assess these three capabilities of the network, and seek the optimal design in terms of the cooperation of the MAC and routing protocols. We evaluate six combinations of the MAC and routing protocols, and identify the best solution. Extensive simulation results are provided, Application models and performance metrics for the three capabilities are developed. The work provides a reference framework for pursuing global monitoring, tracking, query capabilities with hybrid space-terrestrial networks.},
	address = {Monterey, California},
	booktitle = {MILCOM 2004},
	pages = {pp. 899-905}
}
@conference {
	title = {Detection and Prevention of MAC Layer Misbehavior in Ad Hoc Networks},
	author = {Cardenas, Alvaro A., Radosavac, Svetlana., Baras, John S.},
	year = {2004},
	month = {10/2004},
	abstract = {Selfish behavior at the MAC layer can have devastating side effects on the performance of wireless networks, similar to the effects of DoS attacks. In this paper, we focus on the prevention and detection of the manipulation of the backoff mechanism by selfish nodes in 802.11. We first propose an algorithm to ensure honest backoffs when at least one, either the receiver or the sender is honest. Then we discuss detection algorithms to deal with the problem of colluding selfish nodes. Although we have focused on the MAC layer of 802.11, our approach is general and can serve as a guideline for the design of any probabilistic distributed MAC protocol.},
	address = {Washington DC},
	booktitle = {2nd ACM workshop on Security of ad hoc and sensor networks},
	pages = {pp. 17-22}
}
@conference {
	title = {TCP Splitting Protocol for Broadband Aeronautical Satellite Networks},
	author = {Shang, Yadong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2004},
	month = {10/2004},
	abstract = {In this paper, we recommend suitable transport protocols for an aeronautical network supporting Internet and data services via satellite. For the future IP-based aeronautical satellite hybrid network, we describe TCP protocol and focus on the problems that cause dramatically degraded performance of the Transport Protocol. Based on the observation that it is difficult for an end-to-end solution to solve these problems effectively, we propose a new TCP-splitting protocol, termed Aeronautical Transport Control Protocol (AeroTCP). The main idea of this protocol is to use a fixed window for flow control and one duplicated acknowledgment (ACK) for fast recovery. We also study the Gilbert-Elliott channel model for satellite channel since protocol behavior often depends strongly on the channel behavior. Our simulation results show that AeroTCP can maintain higher utilization for the satellite link than end-to-end TCP, especially in burst error-environment.},
	address = {Salt Lake City, Utah},
	booktitle = {23rd Digital Avionics Systems Conference (DASC)},
	pages = {pp. 11.C.3 (1-9)}
}
@conference {
	title = {Vision-Based Microtribological Characterization of Linear Microball Bearings},
	author = {Tan, Xiaobo., Modafe, Alireza., Hergert, R., Ghalichechian, N., Shapiro, B, Baras, John S., Ghodssi, R.},
	year = {2004},
	month = {10/2004},
	abstract = {Microball bearings can potentially provide robust and low friction support in micromachines such as micromotors and microgenerators. Their microtribological behavior needs to be investigated for design and control of such micromachines. In this paper a vision-based, non-intrusive measurement method is presented for characterization of friction in linear microball bearings. Infrared imaging is used to directly observe the dynamics of microballs and track the motion of bearing components. It is verified that microballs roll most of the time with occasional sliding or bumping resulting from fabrication nonuniformity. The friction-velocity curve demonstrates evident hysteresis. The dependence of frictional behavior on several factors is studied.},
	address = {Long Beach, California},
	booktitle = {ASME/STLE International Joint Tribology Conference (IJTC04)},
	pages = {pp. 1-6}
}
@conference {
	title = {ATEMU: A Fine-Grained Sensor Network Simulator},
	author = {Polley, Jonathan., Blazakis, Dionysus., McGee, Jonathan., Rusk, Dan., Baras, John S., Karir, Manish.},
	year = {2004},
	month = {10/2004},
	abstract = {In this paper we describe the design and implementation of ATEMU, a fine grained sensor network simulator. ATEMU is intended to bridge the gap between actual sensor network deployments and sensor network simulations. We adopt a hybrid strategy, where the operation of individual sensor nodes is emulated in an instruction by instruction manner, and their interactions with each other via wireless transmissions are simulated in a realistic manner. A unique feature of ATEMU is its ability to simulate a heterogeneous sensor network. Using ATEMU it is possible to not only accurately simulate the operation of different application on the MICA2 platform but also a complete sensor network where the sensor nodes themselves maybe based on different hardware platforms. In addition we also describe our implementation of XATDB, our front-end debugger/GUI for ATEMU. XATDB provides an excellent educational tool for people to start learning about the operation of sensor nodes and sensor networks, without requiring the purchase of actual sensor node hardware. The accuracy and emulation capabilities provided by ATEMU ensure that when and if actual hardware is used, the software will already have undergone rigorous testing and debugging on an accurate platform. This would provide the sensor network deployment community with a much more accurate estimate of the performance of various algorithms and protocols in realistic scenarios and platforms.},
	address = {Santa Clara, CA},
	booktitle = {First Annual IEEE Communications Society Conference on Sensor and Ad Hoc Communications and Networks},
	pages = {pp. 145-152}
}
@conference {
	title = {Trust Evaluation in Ad-Hoc Networks},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2004},
	month = {10/2004},
	abstract = {An important concept in network security is trust, interpreted as a relation among entities that participate in various protocols. Trust relations are based on evidence related to the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation process of trust evidence in Ad Hoc Networks. Because of the dynamic nature of Ad Hoc Networks, trust evidence may be uncertain and incomplete. Also, no pre-established infrastructure can be assumed. The process is formulated as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. The results are robust in the presence of attackers. We give intuitive requirements for any trust evaluation algorithm. The performance of the scheme is evaluated on three topologies.},
	address = {Philadelphia, PA},
	booktitle = {2004 ACM workshop on Wireless security},
	pages = {pp. 1-10}
}
@conference {
	title = {Adaptive Hierarchical Resource Management for the Hybrid network of MANET-Satellite Internet},
	author = {Liu, Nelson X., Zhou, Xiaoming., Baras, John S.},
	year = {2004},
	month = {09/2004},
	abstract = {MANETs are often deployed in an infrastructure-less or hostile region where the satellite provides the only link for the MANETs to communicate with the rest part of the world. It faces many challenges to support multiple serviced communications between MANETs and Internet through satellite. In this paper we propose an efficient resource management scheme called AHRM to dynamically allocate bandwidths among multiple MANET users and multiple priority and non-priority services sharing a multi-access satellite channel. It uses a flexible hierarchical structure to exploit the channel utility and resolve contention from two levels. A bandwidth adaptation algorithm is designed to adjust the allocation dynamically in response to traffic and link status changes. The algorithm turns out to be in line with reinforcement learning and is a customized version of it for the practical satellite network setting. Implementation issues are discussed. Simulation results are presented, showing that the scheme can guarantee fast delivery of critical messages in spite of channel contention, and significantly improve the performance of multiple services.},
	address = {Los Angeles, California},
	booktitle = {2004 IEEE Vehicular Technology Conference},
	pages = {pp. 4027-4031}
}
@article {
	title = {Modeling and Control of Hysteresis in Magnetostrictive Actuators},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2004},
	month = {07/2004},
	abstract = {A novel dynamic model is proposed for the hysteresis in magnetostrictive actuators by coupling a Preisach operator to an ordinary differential equation, and a parameter identification method is described. An efficient inversion algorithm for a class of Preisach operators with piecewise uniform density functions is then introduced, based upon which an inverse control scheme for the dynamic hysteresis model is presented. Finally, the inversion error is quantified and l1 control theory is applied to improve the robustness of inverse compensation. Simulation and experimental results based on a Terfenol-D actuator are provided.},
	pages = {pp. 1469-1480},
	volume = {Volume 40},
	number = {Issue 9},
	journal = {Automatica}
}
@conference {
	title = {Adaptive Inverse Control of Hysteresis in Smart Materials},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2004},
	month = {09/2004},
	abstract = {Hysteresis hinders the effective use of smart materials in sensors and actuators. This paper addresses recursive identification and adaptive inverse control of hysteresis in smart material actuators, where hysteresis is modeled by a Preisach operator with a piecewise uniform density function. Two classes of identification schemes are proposed and compared, one based on the hysteresis output, the other based on the time-difference of the output. Conditions for parameter convergence are presented in terms of the input to the Preisach operator. An adaptive inverse control scheme is developed by updating the Preisach operator (and thus its inverse) with the output-based identification method. The asymptotic tracking property of this scheme is established, and for periodic reference trajectories, the parameter convergence behavior is characterized. Practical issues in the implementation of the adaptive identification and inverse control methods are also investigated. Simulation and experimental results based on a magnetostrictive actuator are provided to illustrate the proposed approach.},
	address = {Stuttgart, Germany},
	booktitle = {2004 Nonlinear Control Systems (NOLCOS) IFAC Workshop}
}
@article {
	title = {Adaptive Identification and Control of Hysteresis in Smart Materials},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2004},
	month = {09/2004},
	abstract = {Hysteresis hinders the effective use of smart materials in sensors and actuators. This paper addresses recursive identification and adaptive inverse control of hysteresis in smart material actuators, where hysteresis is modeled by a Preisach operator with a piecewise uniform density function. Two classes of identification schemes are proposed and compared, one based on the hysteresis output, the other based on the time difference of the output. Conditions for parameter convergence are presented in terms of the input to the Preisach operator. An adaptive inverse control scheme is developed by updating the Preisach operator (and thus its inverse) with the output-based identification method. The asymptotic tracking property of this scheme is established, and for periodic reference trajectories, the parameter convergence behavior is characterized. Practical issues in the implementation of the adaptive identification and inverse control methods are also investigated. Simulation and experimental results based on a magnetostrictive actuator are provided to illustrate the proposed approach.},
	pages = {pp. 827-839},
	volume = {Vol.  50},
	number = {No. 6},
	journal = {IEEE Transactions on Automatic Control.}
}
@conference {
	title = {Key Management for Secure Multicast in Hybrid Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2004},
	month = {08/2004},
	abstract = {This paper proposes a design for key management for secure multicast in hybrid satellite networks. Communication satellites offer an efficient way to extend IP multicast services for groups in wide-area networks. In order to be commercially viable, the multicast traffic should be accessible only to paying subscribers. Access control can be achieved by data encryption. This requires secure and efficient methods to generate, distribute and update the keys. Most current key management protocols do not scale well when applied to large dynamic groups in wide-area networks. This paper attempts to solve the above problem for groups in a hybrid network that is composed of terrestrial Ethernet LANs interconnected by ATM-based satellite channels. We investigate current group key management protocols, and design a framework for secure and scalable key management for the multicast routing architecture in the satellite network. The proposed framework is presented in detail, alongwith analysis and simulation results.},
	address = {Toulouse, France},
	booktitle = {19th IFIP International Information Security Conference (SEC 2000)},
	pages = {pp. 533-548}
}
@techreport {
	title = {Key Management for Secure Multicast in Hybrid Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2004},
	month = {08/2004},
	abstract = {This paper proposes a design for key management for secure multicast in hybrid satellite networks. Communication satellites offer an efficient way to extend IP multicast services for groups in wide-area networks. In order to be commercially viable, the multicast traffic should be accessible only to paying subscribers. Access control can be achieved by data encryption. This requires secure and efficient methods to generate, distribute and update the keys. Most current key management protocols do not scale well when applied to large dynamic groups in wide-area networks. This paper attempts to solve the above problem for groups in a hybrid network that is composed of terrestrial Ethernet LANs interconnected by ATM-based satellite channels. We investigate current group key management protocols, and design a framework for secure and scalable key management for the multicast routing architecture in the satellite network. The proposed framework is presented in detail, alongwith analysis and simulation results.},
	address = {Toulouse, France}
}
@conference {
	title = {Cumulative Caching for Reduced User-Perceived Latency for WWW Transfers on Networks with Satellite Links},
	author = {Bhalekar, Aniruddha., Baras, John S.},
	year = {2004},
	month = {08/2004},
	abstract = {The demand for internet access has been characterized by an exponential growth. The introduction of high-speed satellite communications systems providing direct-to-home internet is a response to this increasing demand. However such systems use geo-synchronous satellites and suffer from high latency. Currently, the most popular application layer protocols for the World Wide Web (WWW) are HTTP/1.0 and HTTP/1.1. Since HTTP is a request-response protocol, there are performance issues with using it over high-delay links such as links involving Geo-synchronous Earth Orbit (GEO) satellites. Such usage leads to severely increased user perceived latency which makes "internet browsing" a cumbersome experience. In this paper we investigate this problem and analyze a mechanism to reduce this user-perceived delay.},
	address = {Fortaleza, Brazil},
	booktitle = {Service Assurance with Partial and Intermittent Resources: First International Workshop, SAPIR 2004},
	pages = {pp. 179-186}
}
@conference {
	title = {Distributed Change Detection for Worms, DDoS and Other Network Attacks},
	author = {Cardenas, Alvaro A., Baras, John S., V. Ramezani},
	year = {2004},
	month = {06/2004},
	abstract = {Self-propagating code (worms) and distributed denial of service (DDoS) attacks are the most frequent and quite devastating attacks on communication networks and the Internet. We provide novel formulations for the rapid detection of these attacks in the control-theoretic framework of change detection. We present algorithms that effectively can detect worms from their temporal spreading characteristics. We describe the effects of the network topology on the algorithms and their performance. We next present algorithms for detecting DDoS while discriminating against changes in the normal traffic. This is accomplished by a distributed detection formalism where a concept of directionality is introduced and exploited. We then turn into attacks to routing protocols in mobile wireless networks. We develop change detection formulations involving hidden Markov models, which match distribution of the number of hops in the mobile and wireless nodes. Using observations that suggest that this distribution is altered substantially in the presence of such attacks we develop and analyze algorithms for their detection.},
	address = {Boston, MA},
	booktitle = {2004 American Control Conference},
	pages = {pp. 1008-1013}
}
@conference {
	title = {Recursive Identification of Hysteresis in Smart Materials},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2004},
	month = {06/2004},
	abstract = {This paper studies recursive identification of hysteresis in smart materials. A Preisach operator with a piece-wise uniform density function is used to model the hysteresis. Persistent excitation conditions for parameter convergence are discussed in terms of the input to the Preisach operator. Two classes of recursive identification schemes are explored, one based on the hysteresis output, the other based on the time difference of the output. Experimental results based on a magnetostrictive actuator are presented.},
	address = {Boston, MA},
	booktitle = {2004 American Control Conference},
	pages = {pp. 3857-3862}
}
@conference {
	title = {Long-Run Performance Analysis of a Multi-Scale TCP Traffic Model},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {06/2004},
	abstract = {The long-run queueing performance of a multi-scale TCP traffic model, the HOO model, is analysed. Since the model links the multi-scale behaviour with practical traffic elements and approximates TCP traffic very well, the analysis is expected to provide insights into the physical interpretation of multi-scale traffic and to give useful results for performance prediction. To derive a meaningful solution and avoid the extreme difficulty of an exact analysis, the authors adopt several techniques to track the problem, among which are techniques to establish equivalent processes to the traffic process or the queue content process in two cases, the case of fast flows and the case of slow flows. Quantitative results for the queue tails are obtained in both cases, and a unified form is derived. It indicates that three levels of traffic elements in different time scales, i.e. the connection, the burst and the packet, all affect the asymptotic queueing performance. It shows quantitatively how the connection determines the index of the queue tail, and the burst and the packet contribute to the tail with their averages. Used with simple statistical inferences, the analytical result is shown to predict the queueing performance of real traffic well.},
	booktitle = {IEE Proceedings- Communications},
	pages = {pp. 251-257}
}
@conference {
	title = {Web Access Over a Multiple Access Channel: Evaluations and Improvements},
	author = {Zhou, Xiaoming., Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {06/2004},
	abstract = {We evaluate Web browsing performance over a multiple access satellite channel for three different MAC layer protocols. A Web user behavior model is used to generate realistic source traffic. A new transport layer protocol called RWBP is proposed to solve the TCP problems inside satellite networks. RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion control. We compare its performance with TCP over the three multiple access protocols. Our simulation results show that RWBP can reduce the multiple access channel load and at the same time improve the Web page response time when driven by realistic Web traffic. For the MAC layer protocols, combined free demand assignment multiple access (CFDAMA) always performs better than the other two protocols.},
	address = {Paris, France},
	booktitle = {2004 IEEE International Conference on Communications},
	pages = {pp. 4392-4396}
}
@conference {
	title = {Towards Integrating Key Distribution with Entity Authentication for Efficient, Scalable and Secure Group Communication in MANETs},
	author = {Striki, Maria., Baras, John S.},
	year = {2004},
	month = {06/2004},
	abstract = {We focus on the design of key management (KM) schemes tailored for the environment of Mobile Ad Hoc Networks (MANETs). A MANET is a collection of wireless mobile nodes, communicating among themselves over possibly multi-hop paths, without the help of any infrastructure such as base stations or access points. The fact that no central authorization entity is assumed at all times for all nodes makes the task of network operations more difficult and indicates the need for distributed algorithms to provide the functions of centralized entities. KM ensures communication security among nodes and the capability of their cooperation as a secure group. It consists of key generation, user authentication and key distribution services. In this work we address key distribution, group key generation, entity authentication: we emphasize that entity authentication should be designed with key distribution algorithms in mind and vice versa, to achieve efficient and scalable KM schemes for MANETs. We present an entity authentication scheme based on the Merkle Tree algorithm, applied on a key generation protocol recently developed - MOT- to produce an efficient, scalable and secure KM scheme.},
	address = {Paris, France},
	booktitle = {2004 IEEE International Conference on Communications},
	pages = {pg. 4377-4381}
}
@conference {
	title = {Applying Simulated Annealing for Domain Generation in Ad-Hoc Networks},
	author = {Manousakis, Kyriakos., Morera, Raquel., Baras, John S.},
	year = {2004},
	month = {06/2004},
	abstract = {If heterogeneous ad hoc battlefield networks are to scale to hundreds or thousands of nodes, then they must be automatically split into separate network domains. Domains allow routing, QoS and other networking protocols to operate on fewer nodes. This division greatly reduces overall overhead (e.g., routing overhead with n nodes goes from O(n^2) to O(nlogn)) and allows protocols to be tuned to more homogenous conditions [1]. Domain generation (or clustering) can be done using either local or global information. The two approaches are complementary since local domain generation reacts faster, requires less overhead, and is more robust; while global domain generation provides better overall domains. While most existing work has concentrated on local distributed solutions, this paper reports on new global domain generation techniques. In particular we concentrate on the design of good cost functions and efficient optimization algorithms. We show that simple {\textquotedblleft}intuitive{\textquotedblright} cost functions do not produce good domains; rather we need complex functions with multiple parameters depending on the design goals (e.g., low overhead or low delay). Although existing optimization algorithms are too slow to be useful in a large dynamic network, we show that a modified simulated annealing algorithm, with well chosen cooling schedule, state transition probabilities and stop criteria, produces good quality domains in acceptable time},
	address = {Paris, France},
	booktitle = {IEEE International Conference on Communications},
	pages = {pp. 3864-3868}
}
@conference {
	title = {Attacks and Defenses Utilizing Cross-Layer Interactions in MANET},
	author = {Baras, John S., Radosavac, Svetlana.},
	year = {2004},
	month = {06/2004},
	abstract = {Cross-layer protocol design is one of the prevailing methodologies that have recently been adopted in networking research and leads to significant performance benefits. In this study,we assess the performance of cross-layer interaction and investigate its effects with regard to security and information assurance of mobile ad hoc wireless networks. Using attacks in realistic wireless networks as a prototype, we find that natural cross-layer interactions between physical, MAC and network layer protocols in MANET can turn out to be a weak point, causing various attacks and intrusions. However, by allowing a controlled synergy between layers affected by attacks, we facilitate timely detection of such attacks that are otherwise difficult to detect and may have devastating effects on network functionality and operation.},
	address = {Washington DC},
	booktitle = {Workshop on Cross-Layer Issues in the Design of Tactical Mobile Ad Hoc Wireless Networks: Integration of Communication and Networking Functions to Support Optimal Information Management},
	organization = {Naval Research Laboratory}
}
@conference {
	title = {Understanding the Trade-Off Between Multiuser Diversity Gain and Delay - An Analytical Approach},
	author = {Srinivasan, Roshni., Baras, John S.},
	year = {2004},
	month = {05/2004},
	abstract = {Innovative scheduling algorithms for packet switched air-interfaces have been shown to support higher data rates by exploiting the multiuser diversity inherent to cellular wireless systems. While such opportunistic schedulers significantly improve the system throughput, they could degrade the user experience through unfair resource allocation and increased variability in the scheduled rate and delay. The growing demand for service differentiation between real-time multimedia traffic and data traffic underscores the need for these schedulers to incorporate delay constraints. The analytical results in this paper not only highlight the inherent trade-off between system throughput and the delay experienced by mobile users with opportunistic scheduling, but they also provide a novel way of quantifying the Quality of Service(Q0S) offered by a general opportunistic scheduler.Our analysis is strongly supported by system simulations of a time-slotted cellular downlink shared by multiple mobile users with independent, time-varying channels. In addition, we use a continuous approximation to compute closed form expressions for the scheduler statistics.},
	address = {Milan, Italy},
	booktitle = {2004 IEEE 59th Vehicular Technology Conference},
	pages = {pp. 2543-2547}
}
@techreport {
	title = {Framework for IP Multicast in Satellite ATM Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2004},
	month = {05/2004},
	abstract = {This paper proposes a design for IP multicast routing in hybrid satellite networks. The emergence of IP multicast for Internet group communication has placed focus on communication satellites as an efficient way to extend IP multicast services for groups with distributed membership in wide-area networks. This poses interesting challenges for routing. Satellite networks can have both wired and wireless links and also combine different link-layer technologies like Ethernet and ATM. No proposed IP multicast routing protocol for wired networks offers an integrated solution for such networks. This paper attempts to provide a solution by proposing a design for IP multicast routing in wide-area networks that have terrestrial Ethernet LANs interconnected by ATM-based satellite channels. The paper reviews the multicast services offered by IP and ATM, and proposes a multicast routing framework that combines PIM-SM protocol for terrestrial multicasting with the ATM MARS and VC mesh architecture for multicast routing over the satellite links. Modifications are made to the standard protocols to suit the unique needs of the network being considered. The feasibility of the proposed design is tested by performing simulations. The proposed framework is presented in detail, along with analysis and simulation results.},
	address = {Monterey, California},
	number = {Number: CSHCN TR 2004-8}
}
@conference {
	title = {An Optimization-based Approach to Flow~Control and Resource Allocation Problem in Satellite Communication Systems},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {05/2004},
	abstract = {We propose an approach to optimize resource sharing and flow control in a multi-beam broadband satellite system that supports both unicast and multicast flows. We show that, in this architecture, the load on every spot-beam queue could be different, depending on the type of the flows and the distribution of the receivers across spot-beam coverage areas. This load imbalance may significantly under-utilized the system resources and decrease the system throughput when both unicast and multicast flows are active in the system. In this paper, we formulate an optimization problem for Intra- and inter-beam resource sharing such that the variance of the session rates experienced by users of a flow located in different beam coverage areas is minimized. The result of our resource allocation also determines the maximum sustainable rate of each flow. We present results that compare the beam utilization and maximum sustainable sessions rates with and without optimization. We conclude that this method improves the average session rates up to 40\% and average utilization of the system up to 15\% when both unicast and multicast flows are active.},
	address = {Monterey, California},
	booktitle = {22nd AIAA International Communication Satellite Systems Conference \&amp; Exhibit 2004, (ICSSC)}
}
@conference {
	title = {Transport Protocol Support for Aeronautical Satellite Communications},
	author = {Shang, Yadong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2004},
	month = {05/2004},
	abstract = {We recommend suitable transport protocols for an aeronautical network supporting Internet and data services via satellite. We study the characteristics of an aeronautical satellite hybrid network and focus on the problems that cause dramatically degraded performance of the Transport Protocol. We discuss various extensions to standard TCP that alleviate some of these performance problems. Through simulation, we identify those TCP implementations that can be expected to perform reasonably well. Based on the observation that it is difficult for an end-to-end solution to solve these problems effectively, we propose a new TCP-splitting protocol, termed Aeronautical Transport Control Protocol (AeroTCP). The main idea of this protocol is to use a fixed window for flow control and one duplicated acknowledgement (ACK) for fast recovery. Our simulation results show that AeroTCP can maintain higher utilization for the satellite link than end-to-end TCP, especially in high BER environment.},
	address = {Monterey, California},
	booktitle = {22nd AIAA International Communications Satellite Systems Conference \&amp; Exhibit 2004 (ICSSC22)}
}
@conference {
	title = {Framework for IP Multicast in Satellite ATM Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2004},
	month = {05/2004},
	abstract = {This paper proposes a design for IP multicast routing in hybrid satellite networks. The emergence of IP multicast for Internet group communication has placed focus on communication satellites as an efficient way to extend the multicast services for groups with distributed membership in wide-area networks. This poses interesting challenges for routing. Hybrid satellite networks can have both wired and wireless links and also combine different link-layer technologies like Ethernet and ATM. No proposed IP multicast routing protocol for wired networks offers an integrated solution for such networks. This paper attempts to provide a solution by proposing a design for IP multicast routing in wide-area networks that have terrestrial Ethernet LANs interconnected by ATM-based satellite channels. The paper reviews the multicast services offered by IP and ATM, and proposes a multicast routing framework that combines PIM-SM protocol for terrestrial multicasting with the ATM MARS and VC mesh architecture for multicast routing over the satellite links. Modifications are made to the standard protocols to suit the unique needs of the network being considered. The feasibility of the proposed design is tested by performing simulations. The proposed framework is presented in detail, along with analysis and simulation results.},
	address = {Monterey, California},
	booktitle = {22nd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)},
	pages = {pp. 1-13}
}
@conference {
	title = {Protocol Support for A New Satellite-Based Airspace Communication Network},
	author = {Shang, Yadong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2004},
	month = {04/2004},
	abstract = {We Recommend suitable transport protocols for an aeronautical network supporting internet and data services via sattelite.We study the characteristics of an aeronautical satellite hybrid network and focus on the problems that cause dramatically degraded performance of the Transport Protocol. We discuss various extensions to standard TCP that alleviate some of these performance problems. Through simulation, we identify those TCP implementations that can be expected to perform well. Based on the observation that it is difficult for an end-to-end solution to solve these problems effectively, we propose a new TCP splitting protocol, termed Aeronautical Transport Control Protocol (AeroTCP). The main idea of this protocol is to use a fixed window for flow control and one duplicated acknowledgement (ACK) for fast recovery. Our simulation results show that AeroTCP~can maintain higher utilization for the satellite link than end-to-end TCP, especially in high BER environment.},
	address = {Fairfax, Virginia},
	booktitle = {4th Integrated Communications, Navigation, and Surveillance (ICNS) Conference},
	pages = {pp. 81-90}
}
@conference {
	title = {Fixed Point Approximation for Multirate Multihop Loss Networks with State-Dependent Routing},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2004},
	month = {04/2004},
	abstract = {In this paper we consider a class of loss networks that have arbitrary topologies and routes of arbitrary length. Multiple traffic classes are present, each with different bandwidth requirement, and each routed according to a state-dependent routing scheme. In particular, we consider the least loaded routing method generalized to routes of arbitrary number of hops. The connection level performance metric of interest is the end-to-end blocking probability. We are interested in developing fast evaluation methods to provide reasonably accurate estimates of the blocking probability, especially under heavy traffic load. Our algorithms are based on the fixed-point method framework, also known as the reduced load approximation. In addition to what commonly examined by previous work, two more factors contribute to the complexity of the computation in the scenario under consideration in this paper. One is the state-dependent nature of the routing mechanism, the other is the possible overlapping between routes due to the general multihop topology of the network. We present two fast approximation algorithms to evaluate the blocking probability with state-dependent routing by simplifying the route overlapping computation. We discuss the computational complexity of our algorithms as well as sources of approximation error. We then compare the numerical results with that of simulation and show that our algorithms provide fairly accurate blocking probability estimates especially under heavy traffic load.},
	booktitle = {IEEE/ACM Transactions on Networking},
	pages = {pp.361 - 374}
}
@conference {
	title = {Ant-based Adaptive Trust Evidence Distribution in MANET},
	author = {Jiang, Tao., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {Due to the lack of infrastructure and vulnerability of wireless links, security in ad hoc networks is considered to be much more difficult than in traditional hierarchical networks. Building the trust relationship between entities is a fundamental problem in ad hoc networks, since the availability of servers, which distribute trust certificates, is not guaranteed. Furthermore, the existence of any trusted server might not be assumed either. Therefore, the commonly used key distribution center (KDC) and certification authority (CA) are not applicable in such highly autonomous environments. In this paper, we propose a scheme for the distribution of trust certificates, which is completely distributed and adaptive to mobility. Our scheme is based on the swarm intelligence paradigm, which has been used for routing both in wired and wireless networks. Our simulations in ns-2 show that it performs very well in ad hoc environments.},
	address = {Tokyo, Japan},
	booktitle = {2nd International Workshop on Mobile Distributed Computing, in conjunction with the International Conference on Distributed Computing Systems, MDC\&rsquo;04},
	pages = {pp. 588-593}
}
@article {
	title = {Long-run Performance Analysis of a Multi-Scale TCP Traffic Model},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {06/2004},
	abstract = {The long-run queueing performance of a multi-scale TCP traffic model, the HOO model, is analyzed. Since the model links the multi-scale behavior with practical traffic elements and approximates TCP traffic very well, the analysis is expected to provide insights into the physical interpretation of multi-scale traffic and to give useful results for performance prediction. To derive a meaningful solution and avoid the extreme difficulty of an exact analysis, the authors adopt several techniques to track the problem, among which are techniques to establish equivalent processes to the traffic process or the queue content process in two cases, the case of fast flows and the case of slow flows. Quantitative results for the queue tails are obtained in both cases, and a unified form is derived. It indicates that three levels of traffic elements in different time scales, i.e. the connection, the burst and the packet, all affect the asymptotic queueing performance. It shows quantitatively how the connection determines the index of the queue tail, and the burst and the packet contribute to the tail with their averages. Used with simple statistical inferences, the analytical result is shown to predict the queueing performance of real traffic well.},
	pages = {pp. 251-257},
	volume = {Vol.  151},
	number = {No. 3},
	journal = {Communications \&ndash; IEEE Proceedings}
}
@conference {
	title = {Adaptive Dynamic Routing in Mobile Wireless Ad Hoc Networks Utilizing On-Line Link Life Estimates},
	author = {Alzate, Marco A., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {The current duration of a link in a mobile wireless ad hoc network (MANET) can be used for link stability assessment through on-line remaining link life estimation. These estimates implicitly include the effects of true propagation mechanisms, mobility space geometry, power control mechanisms and other phenomena that are ignored or simplistically modeled in other methods based on location or signal strength measures. In this paper we use such estimates for multipath/backup adaptive dynamic routing, and compare its performance with a corresponding multipath/backup version of DSR.},
	address = {Princeton, NY},
	booktitle = {38th Annual Conference on Information Sciences and Systems (CISS 2004)}
}
@conference {
	title = {A Parallel Queue Structure for Active Queue Management},
	author = {Jou,  Jia-Shiang., Tan, Xiaobo., Baras, John S.},
	year = {2004},
	month = {03/2004},
	address = {Princeton, NJ},
	booktitle = {Annual Conference on Information Sciences and Systems}
}
@conference {
	title = {Cross-Layer Attacks in Wireless Ad-Hoc Networks},
	author = {Radosavac, Svetlana., Benammar, Nassir., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {Denial of Service (DoS) attacks are difficult to prevent and protect against. In this paper we focus on DoS attacks in wireless ad hoc networks that propagate from MAC to routing layer, causing breaking of critical routes. We present several traffic patterns that an intelligent attacker can generate to cause Denial of Service attack in one or several nodes in ad hoc networks. More specifically, we focus on the properties of IEEE 802.11 MAC protocol and attack propagation to the routing layer. We focus on attacks that use low-rate traffic patterns with the goal of disabling one or more specific nodes or partitioning the network. We propose a scheme for attack detection based on modelling of MAC protocols using Extended Finite State Machines (EFSM) and present general outline for an Intrusion Detection System that has the ability to generate attack patterns and check the validity of communication patterns in the network.},
	address = {Princeton, New Jersey},
	booktitle = {Proceedings of 38th Conference on Information Sciences and Systems - CISS 2004,},
	pages = {pp. 1266-1271}
}
@conference {
	title = {A Reliable Multicast Transport Protocol with Feedback Implosion Suppression for Satellite Communication Systems},
	author = {Akkor, Gun., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {In this paper, we propose a reliable multicast transport protocol for satellite communication systems. Many of the emerging applications in the Internet would benefit from reliable multicast services, and broadband satellite communication systems have attractive characteristics for supporting such services. However, many of the protocols designed primarily for terrestrial networks do not perform well over satellite networks. Therefore, it is necessary to look at the problem of reliable multicast in the solution space of satellite communications. Our protocol makes use of a special form of forward error correcting codes and couples it with an adaptive window based control mechanism to dynamically adjust the number of encoding packets forwarded to the users. Protocol makes very good use of the broadcast nature of the satellite channel and attempts to minimize the feedback volume by a novel feedback implosion suppression algorithm. We evaluate the protocol performance by computer simulations.},
	address = {Princeton, New Jersey},
	booktitle = {38th Annual Conference on Information Sciences and Systems (CISS 2004)},
	pages = {pp. 1-6}
}
@conference {
	title = {Dynamic Clustering of Self Configured Ad-Hoc Networks Based on Mobility},
	author = {Manasoukis, Kyriakos., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {If heterogeneous ad hoc battlefield networks are to scale to hundreds or thousands of nodes, then they must be automatically split into separate network domains. Domains allow routing, QoS and other networking protocols to operate on fewer nodes, with cross-domain interaction only through a few border nodes. This division greatly reduces overall overhead (e.g., routing overhead with n nodes goes from O(n2) to O(nlogn) and allows protocols to be tuned to more homogenous condition 1]. On the other hand, the benefits from grouping the nodes are obvious only when the clustering is done in a way that the overhead that is produced due to its application does not offset the gain from the grouping of nodes. A significant source of overhead is the reclustering of nodes due to dynamic changes in network topology. If we manage to minimize the effect of reclustering then we expect the performance of the network to be improved (e.g., more scalable and survivable network). In this work we try to identify the various mobility groups and cluster the nodes accordingly. By grouping together nodes with similar mobility characteristics we can minimize/eliminate the effect of reclustering, since the topology changes will not affect the intra cluster connectivity.},
	address = {Princeton, NJ},
	booktitle = {38th Annual Conference on Information Sciences and Systems (CISS 2004)},
	pages = {pp. 1-6}
}
@conference {
	title = {A Parallel Virtual Queue Structure for Active Queue Management},
	author = {Jou,  Jia-Shiang., Tan, Xiaobo., Baras, John S.},
	year = {2004},
	month = {03/2004},
	abstract = {Performance of the Adaptive RED scheme is susceptible to bursty web traffic. A parallel queue structure was proposed earlier to address this problem, where real time connections (such as web and UDP) and non-real time connections (such as FTP) are served in two different queues with droptail and Adaptive RED policies, respectively. In this paper a modified Adaptive RED scheme is proposed for the second queue to improve the goodput of non-real time connections. In this scheme the queue length thresholds for the Adaptive RED are dynamically determined by the average droppping probability. Simulation shows that the packet dropping probability of the Adaptive RED queue stays within a desired small region. The stability of the queue length variation under this policy is proved under mild conditions.},
	address = {Princeton, New Jersey},
	booktitle = {Proceedings of 38th Conference on Information Sciences and Systems - CISS 2004,},
	pages = {pp. 1-6}
}
@conference {
	title = {LES: Layered Encryption Security},
	author = {Karir, Manish., Baras, John S.},
	year = {2004},
	month = {02/2004},
	abstract = {In this paper we discuss the concept of Layered Encryption Security(LES). We analyze the need for introducing layering in a security infrastructure. Layered encryption provides us the ability to selectively disclose different parts of data to different parties that might be interested in it without compromising the security of the other parts. We have implemented a simple prototype implementation to demonstrate the practical feasibility of the concept by modifying IPSEC. Measurements from our implementation indicate that the Layered Encryption approach does not add unacceptable delays and does not substantially increase processing requirements at either the end points or at intermediate nodes.},
	address = { French Caribbean},
	booktitle = {3rd International Conference on Networking (ICN\&rsquo;04)},
	organization = {Gosier Guadeloupe}
}
@conference {
	title = {Multicast Routing in Mobile Ad Hoc Networks Using Source Grouped Flooding},
	author = {Chandrashekar, Karthikeyan., Baras, John S.},
	year = {2004},
	month = {02/2004},
	abstract = {In this paper, we address the multicast routing problem for mobile ad hoc networks (MANETs). We present the Source Grouped Flooding approach to achieve multicast in MANETs. In this protocol, each source creates a flooding group consisting of nodes connecting the source to the multicast members. The nodes in the flooding group are recruited based on hop count distance constraints obtained during a request-reply phase. The flooding group though robust may result in redundant data transmissions. We also propose a probabilistic data forwarding mechanism to achieve efficient data dissemination. The protocol aims to achieve the robustness of flooding and data distribution efficiency of tree based protocols. Simulation results verify performance.},
	address = {Barcelona, Spain},
	booktitle = {5th European Wireless Conference}
}
@conference {
	title = {Implementing Ad Hoc to Terrestrial Network Gateways},
	author = {McGee, Jonathan., Karir, Manish., Baras, John S.},
	year = {2004},
	month = {02/2004},
	abstract = {In this paper we describe our experience of implementing a gateway between ad hoc and terrestrial routing protocols. Our implementation of the gateway includes support for both a unicast routing protocol, as well as a multicast routing protocol. Though we limit our implementation to a particular set of protocols, we believe that the principles involved can easily be applied to other routing protocols. In particular, in this paper we detail our work on implementing a gateway between a network running MOSPF on a wired terrestrial network interface and MAODV on a wireless ad hoc network interface. Though we focus primarily on the single gateway scenario, we also discuss complications that arise from the use of multiple gateways and illustrate the potential failures that can arise in those scenarios.},
	address = {Frankfurt, Germany},
	booktitle = {2nd International Conference on Wired/Wireless Internet Communications (WWIC 2004)},
	pages = {pp. 132-142}
}
@conference {
	title = {Analyzing the Performance of Data Users in Packet Switched Wireless Systems with Prioritized Voice Traffic},
	author = {Srinivasan, Roshni., Baras, John S.},
	year = {2004},
	month = {02/2004},
	abstract = {The integration of wireless telephony and data services in 3G and 4G wireless systems that use packet-switched air interfaces poses new challenges in the management of network resources. Although highly compressed voice traffic is given priority over data traffic, scheduling algorithms which exploit multiuser diversity have been shown to significantly improve the data throughput . In this paper, we quantify the effect of prioritized voice traffic on the performance of data users in the system using a mix of analysis and simulation. We analytically characterize the scheduled rate, delay and packet service times for data in the presence of prioritized voice traffic by using a general scheduling metric that incorporates a measure of the user{\textquoteright}s channel quality in addition to a delay constraint. The results provide important tools for cellular network operators to evaluate system performance and provision resources for traffic with varying Quality of Service(QoS) requirements.},
	address = {Frankfurt, Germany},
	booktitle = {2nd International Conference on Wired/Wireless Internet Communications (WWIC 2004)},
	pages = {pp. 236-247}
}
@conference {
	title = {Measurement and Simulation Based Effective Bandwidth Estimation MANETs},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {01/2004},
	abstract = {Effective bandwidth represents the resource demand for network traffic to achieve its QoS goal. However, the estimation of the effective bandwidth for modern Internet traffic is difficult and inaccurate so far. In this paper we present a novel scheme using the measurement and simulation techniques to estimate the effective bandwidth. The advantages of the schemelie in its accuracy, its applicability to various traffic environments, and its efficiency. We describe the simulation procedure, the efficient search algorithm to quickly lock the effective bandwidth, the sample size determination algorithm, and the performance judgment policy in the simulation to guarantee the estimation accuracy. We also examine the issue of estimating the effective bandwidth of aggregate traffic from sub-aggregates, and provide an empirical formula to achieve very good accuracy.},
	address = {Dallas, Texas},
	booktitle = {GLOBECOM 2004}
}
@conference {
	title = {Decentralized control of autonomous vehicles},
	author = {Baras, John S., Tan, Xiaobo., Hovareshti, Pedram.},
	year = {2003},
	month = {12/2003},
	abstract = {Decentralized control methods are appealing in coordination of multiple vehicles due to their low demand for long-range communication and their robustness to single-point failures. In this paper we explore a decentralized approach to path generation for a group of vehicles in a battlefield scenario. The mission is to maneuver the vehicles to cover a target area while avoiding obstacles and threats during the maneuver. Each vehicle makes its moving decision by minimizing a potential function that encodes information about its neighbours, obstacles, threats and the target. Preliminary analysis of vehicle behaviors is conducted. Simulation has shown that this approach leads to interesting emergent behaviors, and the behaviors can be varied by adjusting the weighting coefficients of different potential function terms.},
	address = {Maui, Hawaii},
	booktitle = {42nd IEEE Conference on Decision and Control},
	pages = {pp. 1532-1537}
}
@conference {
	title = {Jointly optimal quantization, estimation, and control of hidden Markov chains},
	author = {Baras, John S., Tan, Xiaobo., Xi, Wei.},
	year = {2003},
	month = {12/2003},
	abstract = {It is of interest to understand the tradeoff between the communication resource consumption and the achievable system performance in networked control systems. In this paper we explore a general framework for tradeoff analysis and decision making in such systems by studying joint quantization, estimation, and control of a hidden Markov chain. Dynamic programming is used to find the optimal quantization and control scheme that minimizes a weighted combination of different cost terms including the communication cost, the delay, the estimation error, and the running cost. Simulation and analysis based on example problems show that this approach is able to capture the tradeoffs among competing objectives by adjusting the cost weights.},
	address = {Maui, Hawaii},
	booktitle = {42nd IEEE Conference on Decision and Control},
	pages = {pp. 1098-1103}
}
@conference {
	title = {Modeling and Simulation of Telecommunication Networks for Control and Management},
	author = {Baras, John S.},
	year = {2003},
	month = {12/2003},
	abstract = {In this paper, we describe methodologies for telecommunication networks modeling and simulation that are targeted to be useful as tools in on-line and off-line decision making of the type encountered in network control, management and planning problems. We describe the development, validation and use of self-similar and multifractal models, queuing control and performance evaluation, assessing the incremental utility of various models, hierarchical models based on aggregation, analytic approximation models for various performance metrics, trade-off and sensitivity analysis using a multi-objective optimization framework and automatic differentiation. We also describe four illustrative examples of applying these methodologies to dynamic network control and management problems. The examples involve primarily mobile ad hoc wireless and satellite networks in changing environments.},
	address = {New Orleans, Louisiana},
	booktitle = {35th Winter Simulation Conference: Driving Innovation},
	pages = {pp. 431-440}
}
@conference {
	title = {A Feedback Implosion Suppression Algorithm for Satellite Reliable Multicast},
	author = {Akkor, Gun., Baras, John S., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {12/2003},
	abstract = {In this paper, we propose a knapsack-based feedback suppression algorithm for reliable multicast transport protocols operating over a satellite network. A reliable transport protocol needs to identify the packets which failed to reach a given destination. This is achieved through feedback packets returned to the source. For multicast services, receive feedback has been shown to lead to the feedback implosion problem. Feedback implosion is a well-studied problem and various solutions exist in the literature. However, these solutions mainly focus on wireline terrestrial networks and do not take into account the inherent characteristics of the satellite channel and the architecture of the deployed network. Therefore, we need to revisit the problem and provide a new set of solutions for efficient integration to next-generation satellite systems. In this paper, we introduce a feedback implosion suppression algorithm, which effectively suppresses the amount of feedback relayed through the satellite channel, while ensuring that the critical information is conveyed in a timely fashion. The performance of the algorithm is evaluated through simulations.},
	address = {San Francisco, California},
	booktitle = {IEEE Globecom 2003},
	pages = {pp. 3765-3769}
}
@conference {
	title = {Modeling vulnerabilities of ad hoc routing protocols},
	author = {Yang, Shahan., Baras, John S.},
	year = {2003},
	month = {12/2003},
	abstract = {The purpose of this work is to automate the analysis of ad hoc routing protocols in the presence of attackers. To this end, a formal model fo protocol behavior is developed in which time is modeled by a set of constraints on the time of occurrence of events, enabling the representation of partially ordered timed events and asynchronous communication. Data variables are represented symbolically, capturing a range of distinct executions in each expression. Given a formal description of Ad Hoc On-Demand Distance Vector Routing Algorithm (AODV) and the desired safety property (route stability), an analysis by a naive semi-decision procedure discovers an instance of an attack that leads to a violation of the property.},
	address = {Fairfax, Virginia},
	booktitle = {1st ACM workshop on Security of ad hoc and sensor networks},
	pages = {pp. 12-20.},
	organization = {George Mason University}
}
@conference {
	title = {Probability of Imminent Failure as a Routing Metric in a High-Mobility Wireless Ad Hoc Network},
	author = {Alzate, Marco A., Baras, John S.},
	year = {2003},
	month = {10/2003},
	abstract = {The current duration of a link in a mobile wireless ad hoc network (MANET) has important information to offer with respect to its stability. Unlike location or signal strength methods, life measurements implicitly include the effects of true propagation mechanisms, mobility space geometry, power control mechanisms and other phenomena that are ignored or simplistically modeled in the methods mentioned above. Consequently, the information contained in the current duration of the links can be used to enhance the accuracy of these methods. Furthermore, under high mobility conditions and in the absence of any resources for location and signal strength measurements, this information can also be used alone to obtain new routing metrics to enhance the performance of routing algorithms in a MANET. One such metric is the probability of imminent failure, which can also be used to predict route failures with relatively high accuracy. Here we modify DSR to use this metric, improving the efficiency by reducing the routing overhead.},
	address = {Seoul, Korea},
	booktitle = {8th International Conference on Intelligent Communications (CIC 2003)}
}
@conference {
	title = {Dynamic Adaptation of Access Control Policies},
	author = {Bharadwaj, Vijay G., Baras, John S.},
	year = {2003},
	month = {10/2003},
	abstract = {We describe an architecture and algorithms for deriving an access control policy by composing access control requirements specified at multiple levels in a command hierarchy. Our method can detect conflicts in requirements, and find a policy that maximally satisfies the requirements, by satisfying higher priority requirements at the expense of lower priority ones. It also allows for easy verification of the final policy by an administrator. The architecture allows quick adaptation of policies to changing situations, by providing for delegation of authority while ensuring that high priority requirements will always be satisfied.},
	address = {Boston, Massachusetts},
	booktitle = {MILCOM 2003},
	pages = {pp. 761-766}
}
@conference {
	title = {Clustering for transmission range control and connectivity assurance for self configured ad hoc networks},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2003},
	month = {10/2003},
	abstract = {Ad hoc networks have been the new networking technology trend because of their promising characteristics. These characteristics fit better the requirements of today{\textquoteright}s army and the needs of today{\textquoteright}s commercial world. Most of the applications that have been referred in the bibliography assume devices that are of finite power. The latter is true because of the existing technology (web-enabled cell phones, PDAs, laptops, PPCs). The goal for ad hoc networks is to accommodate lightweight, battery-powered portable devices. Because of the finite power limitation, we have to design efficient ways to use the existing power. A first step towards efficient utilization of power is to eliminate its unnecessary usage wherever possible. For a networking device, significant part of power is consumed for communications and more specifically for transmissions. In this work we focus on eliminating the transmission power consumed into the network subject to the network{\textquoteright}s connectivity. The assurance of network connectivity is essential in this problem since the usage of limited transmission power from the nodes may result in a partitioned network. We provide solutions to the efficient usage of transmission power by clustering the nodes based on their proximity and ensuring the intracluster and intercluster connectivity of the network. The algorithms presented in this paper achieve their objective as the collected results from their simulation show.},
	address = {Boston, MA},
	booktitle = {Military Communications Conference, MILCOM 2003},
	pages = {pp. 1043-1047}
}
@conference {
	title = {Key Distribution Protocols for Secure Multicast Communication Survivable in MANETs},
	author = {Striki, Maria., Baras, John S.},
	year = {2003},
	month = {10/2003},
	abstract = {In this paper, we develop a secure, robust and scalable key management scheme for multicast communications in Mobile Ad Hoc Networks (MANETs). Most key distribution protocols of today are primarily designed for wire-line networks. Frequent node failures, network partitions, inefficient computational and communication capabilities of wireless nodes, network delay, bad quality of signal etc, are some of the reasons why they fail to work properly in MANETs. We classify existing and newly developed protocols in two families, contributory and non-contributory. We evaluate them and compare their performance. We focus on studying and developing key distribution techniques that achieve scalability and high performance within our framework without sacrificing the security level of the network. We also describe a hierarchical two-level hybrid key management scheme that utilizes some of the above protocols in the appropriate combinations to further reduce the storage, communication and computation costs of nodes.},
	address = {Boston, Massachusetts},
	booktitle = {MILCOM 2003},
	pages = {pp. 1-6}
}
@conference {
	title = {Data Dependent Keying for Wireless Networks},
	author = {Karir, Manish., Baras, John S.},
	year = {2003},
	month = {10/2003},
	abstract = {The failure of the 802.11 WEP security specifications to provide any reasonable level of security has come under sharp criticism recently. In this paper we propose a novel scheme for providing security in both a base station based, as well as an ad hoc network environment. Our proposed scheme uses data exchanged between communicating peers to evolve per-packet keys. In addition to the concept of data dependent keying (DDK), we include other well-known security primitives such as SHA-1 based HMAC and RC4 encryption to provide a complete security solution for wireless networks. We argue that our scheme provides an adequate security/overhead tradeoff, and can be easily implemented on current hardware platforms. In addition, the low overhead characteristic as well as the use of symmetric cryptographic functions makes the scheme an attractive option for sensor networks, where energy efficiency is a primary objective.},
	address = {Orlando, Florida},
	booktitle = {58th Vehicular Technology Conference},
	pages = {pp. 2098-2102}
}
@conference {
	title = {Near-optimal Policies for Broadcasting Files with Unequal Sizes},
	author = {Raissi-Dekhordi, Majid., Baras, John S.},
	year = {2003},
	month = {10/2003},
	abstract = {Information broadcasting is an effective method to deliver popular information pages to a large number of users in wireless and satellite networks. In a previous work, we used a dynamic optimization approach to address the problem of broadcast scheduling for a pull system with equal file sizes. In this paper, we address that problem in a more general setting where the file sizes are not equal and have geometric size distributions with possibly different means. The dynamic optimization approach allows us to find a near-optimal scheduling policy, which we use as a benchmark to evaluate a number of other heuristic policies. Also, we modify the resulting policy and apply it to the case with fixed (unequal) file sizes and compare the results with some other well known, as well as new, heuristic policies. Finally, we introduce a low-complexity heuristic policy to be used for practical implementations. The results show that the performance of the new policy is very close to that of the original policy.},
	address = {Monticello, Illinois},
	booktitle = {41st Annual Allerton 2003 Conference},
	pages = {pp. 279-288}
}
@conference {
	title = {Multi-Agent Stochastic Control: Models Inspired from Quantum Physics},
	author = {Baras, John S.},
	year = {2003},
	month = {08/2003},
	abstract = {In this paper, we consider multi-agent stochastic optimization and control problems, with partial information. The agent can operate in a distributed and asynchronous fashion. We investigate new problems that arise out of the interaction between observations and control actions by the agent. We show that new non-classical and non-commutative probability models are needed in order to properly formulate such problems. The models we develop here are inspired by models developed for dynamical physics problems. We establish a series of fundamental results for the trade-off between information and control patterns in distributed stochastic control, detection and estimation.},
	address = {Saint Petersburg, Russia},
	booktitle = {2003 International Conference on Physics and Control},
	pages = {pp. 747-758}
}
@conference {
	title = {Correctness Proof for a Dynamic Adaptive Routing Algorithm for Mobile Ad-hoc Networks},
	author = {Yang, Shahan., Baras, John S.},
	year = {2003},
	month = {07/2003},
	abstract = {Dynamic and adaptive routing algorithms are the {\textquotedblleft}brains{\textquotedblright} of mobile ad-hoc networks (MANETs), in that they govern the self-organization of these networks. MANETs are infrastructureless {\textquotedblleft}intelligent{\textquotedblright} networks, which are becoming increasingly popular and have wide applicability. In this paper, we view dynamic adaptive routing algorithms for MANETs as hybrid systems (partly based on logic and partly based on numerics). In this paper, we introduce formal models for the analysis and verification of one such routing algorithm, the Temporally Oriented Routing Algorithm (TORA) under certain assumptions. More specifically we give a rigorous mathematical proof of correctness and convergence of TORA. Other formal methods, their limitations~and future research challenges are also discussed.},
	address = {Lake Baikal, Russia},
	booktitle = {IFAC Workshop \&ndash; Modeling and Analysis of Logic Controlled Dynamic Systems},
	pages = {pp. 1-10}
}
@conference {
	title = {An Implementation Study of Multicast Extensions of AODV},
	author = {Dharmaraju, Dinesh., Karir, Manish., Baras, John S., Das, Subir.},
	year = {2003},
	month = {07/2003},
	abstract = {In this paper we describe our experience of implementing multicast extensions of AODV (MAODV). Using insight gained from our implementation we propose some enhancements to MAODV that enhance its stability and its performance. We propose the use of a tree optimization scheme based on Group Hello messages, a scheme for merging group partitions, as well as a method to add reliability to the multicast tree formation and maintenance, via the use of an acknowledgement for MACT messages. Our implementation is based on the kernel AODV implementation from NIST. We describe details regarding our implementation that can provide valuable insight to future implementers of ad hoc routing protocols, and in particular, people attempting to implement multicast routing protocols. We also provide a brief description of some basic validation experiments that we used to verify the functionality and the various features of our implementation.},
	address = {Montreal, Canada},
	booktitle = {SPECTS 2003 Conference}
}
@conference {
	title = {Performance evaluation of run-to-run control methods in semiconductor processes},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {Run-to-run (RtR) control plays an important role in semiconductor manufacturing processes. In this paper, RtR control methods are classified and evaluated. The set-valued RtR controllers with ellipsoid approximation are compared with two typical RtR controllers: the exponentially weighted moving average (EWMA) controller and the optimizing adaptive quality controller (OAQC) by simulations according to the following criteria: a good RtR controller should be able to compensate for various disturbances, such as small drifts, step disturbances and model errors; moreover, it should be able to deal with bounds, cost requirement and multiple targets that are often encountered in semiconductor processes. Based on our simulation results, suggestions on selection of a proper RtR controller for a semiconductor process are given as conclusions.},
	address = {Istanbul, Turkey},
	booktitle = {2003 IEEE Conference on Control Applications},
	pages = {pp. 841-848}
}
@conference {
	title = {Jitter analysis of CBR streams in multimedia networks},
	author = {Jou,  Jia-Shiang., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {The performance of real-time applications such as video and voice streams relies on packet delay jitter. Large delay jitter causes buffer overflow or underflow at the receiver end and the user encounters interrupt. The delay jitter is mainly due to the perturbation of background traffic in the bottleneck router. Fulton and Li (1998) provide an analytical approximation for the first-order and second-order statistics of delay jitter. However, their analysis is based on a Markovian model of the background traffic, which is not quite suitable for Internet traffic and requires lots of computational effort. We propose an efficient method to predict the jitter variance of a CBR (constant-bit-rate) connection based on the wavelet model of the background traffic. The wavelet analysis extracts the statistical properties of background traffic and the analysis result can be used to predict an upper bound for the jitter variance of the CBR connection.},
	address = {Istanbul, Turkey},
	booktitle = {2003 IEEE Conference on Control Applications},
	pages = {pp. 1339-1344}
}
@conference {
	title = {Markov Processes with State-Dependent Failure Rates and Application to RED and TCP Window Dynamics},
	author = {Misra, Archan., Ott, Teunis., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {This paper presents a mathematical technique for computing the stationary distribution of Markov processes that evolve deterministically between arbitrarily distributed {\textquoteleft}failure events{\textquoteright}. The key innovation in this paper is the use of a state-dependent time rescaling technique, such that the re-scaled process can be described by a Poisson-interrupted stochastic differential equation. This technique is first applied to compute the stationary window distribution of a TCP flow performing idealized classical congestion avoidance under variable, but state-dependent, packet loss, and subsequently, to study the distribution of a TCP flow performing generalized congestion avoidance. We show how the stochastic differential equation can be solved by a rapidly convergent numerical technique to obtain the stationary distribution in the re-scaled (subjective) time, and present the re-scalings needed to eventually obtain the distribution of the original Markov process. We demonstrate how this analysis can be used to compute the window distribution of a TCP flow interacting with a RED, ERD or ECN queue, with or without minimally assured throughput guarantees.},
	address = {Rhodes, Greece},
	booktitle = {11th Mediterranean Conference on Control and Automation (MED\&rsquo;03)}
}
@conference {
	title = {A New Adaptive Aggregation Algorithm for Infinite Horizon Dynamic Programming},
	author = {Zhang, Chang., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {Dynamic programming suffers the {\textquotedblleft}curse of dimensionality{\textquotedblright} when it is employed for complex control systems. State aggregation is used to solve the problem and accelerate computation by looking for a sub-optimal policy. In this paper, a new method, which converges much faster than conventional aggregated value iteration based on TD(0), is proposed for computing the value functions of the aggregated system. Preliminary results show that the new method increases the speed of convergence impressively. Aggregation introduces errors inevitably. An adaptive aggregation scheme employing the new computation method is also proposed to reduce the aggregation errors.},
	address = {Rhodes, Greece},
	booktitle = {11th Mediterranean Conference on Control and Automation (MED\&rsquo;03)},
	pages = {pp. 1-6}
}
@conference {
	title = {A dynamic model for magnetostrictive hysteresis},
	author = {Tan, Xiaobo., Baras, John S., Krishnaprasad, P S.},
	year = {2003},
	month = {06/2003},
	abstract = {The rate-dependent hysteresis present in thin magnetostrictive actuators can be captured by a dynamic model, consisting of a Preisach operator coupled to an ordinary differential equation in an unusual way. The model presents interesting problems in analysis and computation due to its special structure. In this paper, we first transform the model into a more amenable form and gain insight into the model by introducing a new hysteretic operator. Then we investigate some system-theoretic properties of the model: stability of equilibria, input-output stability, reachability~and observability. Existence of periodic solutions under periodic forcing is also established. Finally, numerical integration schemes for the model are discussed.},
	address = {Denver, Colorado},
	booktitle = {2003 American Control Conference},
	pages = {pp. 1074-1079}
}
@conference {
	title = {A robust control framework for smart actuators},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {Hysteresis in smart actuators presents a challenge in control of these actuators. A fundamental idea to cope with hysteresis is inverse compensation. But due to the open loop nature of inverse compensation, its performance is susceptible to model uncertainties and to errors introduced by inverse schemes. In this paper, we develop a robust control framework for smart actuators by combining inverse control with the l/sub 1/ robust control theory, where the inversion error is modeled as an exogenous disturbance with a magnitude bound quantifiable in terms of parameter uncertainties and inversion schemes. Through the example of controlling a magnetostrictive actuator, we present a systematic controller design method which guarantees robust stability and robust trajectory tracking while taking actuator saturation into account. Simulation and experimental results are provided.},
	address = {Denver, Colorado},
	booktitle = {2003 American Control Conference},
	pages = {pp. 4645-4650}
}
@conference {
	title = {Towards automated negotiation of access control policies},
	author = {Baras, John S., Bharadwaj, Vijay G.},
	year = {2003},
	month = {06/2003},
	abstract = {We examine the problem of negotiating access control policies between autonomous domains. Our objective is to develop software agents that can automatically negotiate access control policies between autonomous domains with minimal human guidance. In this paper, we show a mathematical framework that is capable of expressing many such negotiation problems~and illustrate its application to some practical scenarios.},
	address = {Lake Como, Italy},
	booktitle = {4th International Workshop on Policies for Distributed Systems and Networks},
	pages = {pp. 111-119}
}
@conference {
	title = {Routing and Security Problems in Networking: A Systems and Control Perspective},
	author = {Baras, John S.},
	year = {2003},
	month = {05/2003},
	address = {Seattle, WA},
	organization = {University of Washington}
}
@conference {
	title = {Engineering and Information Technology},
	author = {Baras, John S.},
	year = {2003},
	month = {05/2003},
	address = {College Park, MD},
	booktitle = {Charles and Helen White Symposium},
	organization = {University of Maryland}
}
@conference {
	title = {Dynamic Clustering for Transmission Range Control in Ad Hoc Networks},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2003},
	month = {04/2003},
	abstract = {Ad hoc networks have being given a lot of attention in recent years. The problems associated with this kind of networks are many and difficult to solve because of their dynamic nature {\textendash} networks with non-static topology and non-static infrastructure. A large number of the issues under investigation are related with the finite power of the mobile devices. In terms of the communication tasks that those devices perform, the transmission power that is utilized plays a very important role to the long-term survivability of the network. The issue of transmission power affects the connectivity of the network, in a way that when the utilized transmission power is small then the network may be partitioned. In this work the latter has equivalent importance with the case where the assignment of excessive transmission power, resulting in a very dense net of communication links. When we use large transmission power then the long-term survivability and connectivity of the network is jeopardized because the nodes use their finite power inefficiently. Our task is to adjust the transmission power to the level where both the connectivity of the network is ensured and the transmitted power is minimized among all participating devices.},
	address = {College Park, Maryland},
	booktitle = {Collaborative Technology Alliances (CTA) Communications \&amp; Networks (C\&amp;N) Alliance - 2003 Annual Symposium},
	organization = {University of Maryland Conference Center}
}
@conference {
	title = {Efficient Scalable Key Agreement Protocols for Secure Multicast Communication in MANETs},
	author = {Striki, Maria., Baras, John S.},
	year = {2003},
	month = {04/2003},
	abstract = {In this paper protocols for group key distribution are compared and evaluated from the point of view of Mobile Ad Hoc Networks (MANETs). A MANET is a collection of wireless mobile nodes, communicating among themselves over possibly multihop paths, without the help of any infrastructure such as base stations or access points. So the need to render those networks as autonomous and secure as possible, since no central authorization can be assumed at all times, becomes emergent. Key management is the service that ensures the security of communication among nodes, and the capability of their cooperation as a secure group. It consists of three important services: key generation, user authentication and key distribution. In this work we assume that the participating users have already been authenticated with some mechanism, and we are focused only on studying and comparing protocols for group key establishment in MANETs. We distinguish the protocols in two families, the contributory and noncontributory and we evaluate them from the point of view of MANETs.},
	address = {College Park, Maryland},
	booktitle = {Collaborative Technology Alliances (CTA) Communications \&amp; Networks (C\&amp;N) Alliance - 2003 Annual Symposium},
	organization = {University of Maryland Conference Center}
}
@conference {
	title = {Performance Evaluation and Traffic Analysis for Routing Protocols in a Real MANET},
	author = {Chen, Huigang., Jou,  Jia-Shiang., Dharmaraju, Dinesh., Papageorgiou, George., Baras, John S.},
	year = {2003},
	month = {04/2003},
	abstract = {Mobile Ad-hoc NETworks (MANETs) are characterized by bandwidth constrained links, multiple hops, varying link qualities and highly dynamic topologies. In this paper, we evaluate the performance and analyze the traffic of a mobile ad-hoc network in a realistic setting. Using simulation, we provide results of performance evaluation in terms of various metrics. We study performance with scenarios of different propagation matrices, different traffic mixes, and different routing protocols (DSDV, DSR, AODV). The results show that in most cases, the performance is sensitive to the routing protocol, path loss, and traffic characteristics. This provides rationale and insight for choosing the right protocols to provide quality of service in terms of different metrics in different environments. Also, we find that in a MANET, we obtain long-range dependency traffic regardless of source file size distribution. This discovery will help in providing methodology to tackle the network dimensioning problem in ad hoc networks.},
	address = {College Park, Maryland},
	booktitle = {Collaborative Technology Alliances (CTA) Communications \&amp; Networks (C\&amp;N) Alliance - 2003 Annual Symposium},
	pages = {pp.147-151},
	organization = {University of Maryland Conference Center}
}
@conference {
	title = {Distributed Trust Establishment in MANETs{\textquoteright} Swarm Intelligence},
	author = {Eschenauer, Laurent., Baras, John S., Gligor, Virgil D.},
	year = {2003},
	month = {04/2003},
	abstract = {We present some properties of trust establishment in mobile, ad-hoc networks and illustrate how they differ from those of trust establishment in the Internet. We present a framework for trust establishment in mobile ad-hoc networks and argue that peer-to-peer networks are especially suitable to solve the problems of generation, distribution, and discovery of trust evidence in mobile ad-hoc networks. We develop a new scheme based on swarm intelligence and demonstrate its advantages over the peer to peer scheme. We evaluate our approach through simulation with NS-2.},
	address = {College Park, Maryland},
	booktitle = {Collaborative Technology Alliances (CTA) Communications \&amp; Networks (C\&amp;N) Alliance - 2003 Annual Symposium},
	pages = {pp. 125-129},
	organization = {University of Maryland Conference Center}
}
@conference {
	title = {Dynamic Adaptive Routing in MANETs},
	author = {Baras, John S., Mehta, Harsh.},
	year = {2003},
	month = {04/2003},
	abstract = {Mobile ad hoc networks are infrastructure-less networks consisting of wireless, possibly mobile nodes that are organized in peer-to-peer and autonomous fashion. The highly dynamic topology, limited bandwidth availability and energy constraints make the routing problem a challenging one. The Swarm Intelligence paradigm has recently been used in solving the routing problem in static computer networks with encouraging results. These algorithms have been proven to be robust and resilient to topology changes. In this paper, we present performance results on a new routing algorithm for MANETs based on the swarm intelligence paradigm. We present simulation results that measure the performance of our algorithm with respect to the characteristics of a MANET, the varying parameters of the algorithm itself as well as performance comparison with other well-known MANET routing protocols.},
	address = {College Park, Maryland},
	booktitle = {Collaborative Technology Alliances (CTA) Communications \&amp; Networks (C\&amp;N) Alliance- 2003 Annual Symposium},
	pages = {pp. 367-371},
	organization = {University of Maryland Conference Center}
}
@conference {
	title = {Efficient Source Authentication for Multicasting in MANETs},
	author = {Baras, John S., Ramachandran, Prabha.},
	year = {2003},
	month = {04/2003},
	abstract = {In this paper, we investigate a popular source authentication scheme, TESLA (Timed Efficient Stream Loss-tolerant Authentication) for multicast communication in mobile ad hoc networks. We evaluate the performance of a source authentication scheme inspired from TESLA and mu-TESLA based on simulations. Time synchronization is a crucial assumption made by these schemes. We describe effective means to achieve time synchronization in MANETs and conclude that overlay networks, whether they are UAVs or satellites are essential for high efficiency and performance. Since such overlay networks are typical in hierarchical wireless mobile networks, the proposed schemes are very appropriate for these scenarios. We claim that having an overlay network will help in routing and key distribution, in addition to time synchronization.},
	address = {College Park, Maryland},
	booktitle = {Collaborative Technology Alliances (CTA) Communications \&amp; Networks (C\&amp;N) Alliance - 2003Annual Symposium},
	organization = {University of Maryland Conference Center}
}
@conference {
	title = {A framework for automated negotiation of access control policies},
	author = {Bharadwaj, Vijay G., Baras, John S.},
	year = {2003},
	month = {04/2003},
	abstract = {Our research examines the problem of negotiating access control policies between autonomous domains. Our objective is to develop software agents that can automatically negotiate access control policies between autonomous domains with minimal human guidance. In this paper we describe a mathematical framework that is capable of expressing many such negotiation problems, and illustrate its application to some practical scenarios.},
	address = {Washington DC},
	booktitle = {DARPA Information Survivability Conference and Exposition}
}
@conference {
	title = {Integrated security services for dynamic coalitions},
	author = {Khurana, Himanshu., Serban Gavrila, Bobba, Rakeshbabu., Koleva, Radostina. , Sonalker, Anuja., Dinu, Emilian., Gligor, Virgil D., Baras, John S.},
	year = {2003},
	month = {04/2003},
	abstract = {Coalitions are collaborative networks of autonomous domains where resource sharing is achieved by the distribution of access permissions to coalition members based on negotiated resource-sharing agreements. The focus of our research is on dynamic coalitions, namely, coalitions where member domains may leave or new domains may join during the life of the coalition. We have developed a set of tools that integrate security services for dynamic coalitions, namely, services for (1) private and shared resource management, (2) identity and attribute certificate management, (3) secure group communication, and (4) joint administration for enforcing joint-action policies on shared critical resources. In this paper we give an overview of the architecture and implementation of our tools.},
	address = {Washington DC},
	booktitle = {2003 DARPA Information Survivability Conference and Exposition},
	pages = {pp. 38-40}
}
@conference {
	title = {Using Broadband Satellite Systems to Support Aeronautical Communication},
	author = {Shang, Yadong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2003},
	month = {04/2003},
	abstract = {In this paper we discuss the possibility of using a broadband satellite-based system to support aeronautical communications. First, we investigate the applications and service requirements for current and future aeronautical communications. Then the communication system and network architecture are outlined and some of the system components are discussed in detail, including the satellite transmission channel, the airplane on-board network, and various aspects of aeronautical terminals. Finally we present a simulation analysis of the system with the focus on meeting the Quality of Service requirements for identified service categories.},
	address = {Yokohama, Japan},
	booktitle = {23rd AIAA International Communications Satellite Systems Conference and Exhibit (ICSSC)},
	pages = {pp. 1-9}
}
@conference {
	title = {Statistical modeling and performance analysis of multi-scale traffic},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2003},
	month = {03/2003},
	abstract = {In this paper we propose a new statistical model for multi-scale traffic, and present an exact queueing analysis for the model. The model is based on the central moments and the marginal distributions of the cumulative traffic loads in different time scales. Only the first two moments are needed to characterize the traffic process, which greatly simplifies the representation and estimation. The queueing analysis uses a very general approach and can evaluate not only the steady state performance but also the transient queuing behavior. The analysis reveals that there exist two classes of packet losses, the absolute loss and the opportunistic loss, both of which can be examined exactly with the method. Based on the statistical model and the queueing analysis method, a compound model is constructed for the practical multiscale traffic, and its performance is evaluated from various aspects. This work provides a good basis for practical application of the multiscale traffic characterizations in network dimensioning and resource management.},
	address = {San Francisco, CA},
	booktitle = {22nd Annual Joint Conference of the IEEE Computer and Communications Societies, INFOCOM 2003},
	pages = {pp. 1837-1847}
}
@conference {
	title = {The Experimentation and Modeling of {\textquotedblleft}Satellite-Friendly{\textquotedblright} HTTP},
	author = {Bhalekar, Aniruddha., Baras, John S.},
	year = {2003},
	month = {03/2003},
	abstract = {The demand for Internet access has been characterized by an exponential growth. The introduction of high-speed satellite communication systems providing direct-to-home Internet services is a response to this increasing demand. However, such systems suffer from high delay-bandwidth product and high bit-error-rate which causes degradation in the performance of HTTP, which is a request-response type, application-layer protocol over TCP. In this paper we investigate HTTP/1.0, HTTP/1.1 and analyze different mechanisms to reduce the user-perceived delay and improve the performance of Internet delivery over satellite links. The paper also suggests other mechanisms, such as multiple parallel connections and a delta encoding implementation to overcome the above-mentioned problem. We show that there is a marked improvement in Internet browsability and user-perceived delay, using these methods.},
	address = {Baltimore, Maryland},
	booktitle = {37th Conference on Information Sciences and Systems (CISS)},
	organization = {John Hopkins University}
}
@conference {
	title = {Detection and Classification of Network Intrusions Using Hidden Markov Models},
	author = {Radosavac, Svetlana., Baras, John S.},
	year = {2003},
	month = {03/2003},
	abstract = {This paper demonstrates that it is possible to model attacks with a low number of states and classify them using Hidden Markov Models with very low False Alarm rate and very few False Negatives. We also show that the models developed can be used for both detection and classification. We put emphasis on detection and classification of network intrusions and attacks using Hidden Markov Models and training on anomalous sequences. We test several algorithms, apply different rules for classification and evaluate the relative performance of these. Several of the attack examples presented exploit buffer overflow vulnerabilities, due to availability of data for such attacks. We emphasize that the purpose of our algorithms is not only the detection and classification of buffer overflows; they are designed for detecting and classifying a broad range of attacks.},
	address = {Baltimore, Maryland},
	booktitle = {37th Conference on Information Sciences and Systems (CISS)},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Finite Automata Models for Anomaly Detection},
	author = {V. R. Ramezani, Yang, Shahan., Baras, John S.},
	year = {2003},
	month = {03/2003},
	abstract = {A fundamental problem in Intrusion detection is the fusion of dependent information sequences.In this paper ,we consider the fusion of two such sequences ,namely the sequence of system calls and the value of the instruction pointer.We introduce FAAD, a finite automation representation defined for the product alphabet of the two sequences where dependencies are implicitly taken into account by a matching procedure.},
	address = {Baltimore, Maryland},
	booktitle = {37th Conference on Information Sciences and Systems (CISS)},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Fault-tolerance and efficiency considerations for key distribution ~protocols in MANETs},
	author = {Striki, Maria., Baras, John S.},
	year = {2003},
	month = {03/2003},
	abstract = {In this paper we address the Fault-Tolerance and Efficiency of key distribution protocols for group communications in Mobile AdHoc Networks. Most key distribution protocols that exist today are primarily designed for wireline networks. These protocols either fail to work as intended or cannot work at all when they are applied to the demanding environment of MANETs. The main reasons for this are: frequent node failures, network partitions and merges, inefficient computational and communication capabilities of certain wireless nodes, network delay, bad quality of signal etc. We determine the framework under which protocols can efficiently work in MANETs, design new protocols or modify existing ones, so that they can be robust, scalable and applicable in this environment. We classify these protocols in two families: contributory and non-contributory. We evaluate them from the point of view of MANETs and compare their performance.},
	address = {Baltimore, Maryland},
	booktitle = {37th Conference on Information Sciences and Systems(CISS)},
	organization = {Johns Hopkins University}
}
@conference {
	title = {A Probabilistic Emergent Routing Algorithm (PERA) for Mobile Ad Hoc Networks},
	author = {Baras, John S., Mehta, Harsh.},
	year = {2003},
	month = {03/2003},
	abstract = {Mobile ad hoc networks are infrastructure-less networks consisting of wireless, possibly mobile nodes which are organized in peer-to-peer and autonomous fashion. The highly dynamic topology, limited bandwidth availability and energy constraints make the routing problem a challenging one. In this paper we take a novel approach to the routing problem in MANETs by using swarm intelligence-inspired algorithms. The proposed algorithm uses Ant-like agents to discover and maintain paths in a MANET with dynamic topology. We present simulation results that measure the performance of our algorithm with respect to the characteristics of a MANET, the varying parameters of the algorithm itself as well as performance comparison with other well-known routing protocols.},
	address = {Sophia-Antipolis, France},
	booktitle = {WiOpt \&rsquo;03: Modeling and Optimization in Mobile, AdHoc and Wireless Networks}
}
@conference {
	title = {TORA, Verification, Proofs and Model Checking},
	author = {Yang, Shahan., Baras, John S.},
	year = {2003},
	month = {03/2003},
	address = {Sophia-Antipolis, France},
	booktitle = {WiOpt \&rsquo;03: Modeling and Optimization in Mobile, AdHoc and Wireless Networks}
}
@conference {
	title = {On the performance limits of data-aided synchronization},
	author = {Jiang, Yimin., Sun, Feng-Wen., Baras, John S.},
	year = {2003},
	month = {01/2003},
	abstract = {This paper addresses data-aided (DA) synchronization, in which the reference parameter acquisition is aided by a training sequence known to the receiver. The Cramer-Rao lower bound (CRB) for the DA timing and/or carrier phase recovery is presented. For DA parameter estimation, the CRB typically varies with the training sequence. This indicates that different training sequences offer fundamentally different performance. In the literature, the widely cited closed-form CRB for timing and carrier phase recovery was derived under the assumption that the training sequence is independent and identically distributed (i.i.d.) and sufficiently long. We derive a closed-form CRB for timing and carrier phase recovery with respect to an arbitrary training sequence and pulse shaping function for the over and under sampling cases. It turns out that the CRB is a weighted summation of the aperiodic correlation of the training sequence and the weighting factor is determined by the pulse shaping filter. Therefore, this paper reveals the fundamental link between a training sequence and its corresponding performance limit.},
	booktitle = {IEEE Transactions on Information Theory},
	pages = {191 - 203}
}
@conference {
	title = {On the convergence of the inverses of Toeplitz matrices and its applications},
	author = {Sun, Feng-Wen., Jiang, Yimin., Baras, John S.},
	year = {2003},
	month = {01/2003},
	abstract = {Many issues in signal processing involve the inverses of Toeplitz matrices. One widely used technique is to replace Toeplitz matrices with their associated circulant matrices, based on the well-known fact that Toeplitz matrices asymptotically converge to their associated circulant matrices in the weak sense. This often leads to considerable simplification. However, it is well known that such a weak convergence cannot be strengthened into strong convergence. It is this fact that severely limits the usefulness of the close relation between Toeplitz matrices and circulant matrices. Observing that communication receiver design often needs to seek optimality in regard to a data sequence transmitted within finite duration, we define the finite-term strong convergence regarding two families of matrices. We present a condition under which the inverses of a Toeplitz matrix converges in the strong sense to a circulant matrix for finite-term quadratic forms. This builds a critical link in the application of the convergence theorems for the inverses of Toeplitz matrices since the weak convergence generally finds its usefulness in issues associated with minimum mean squared error and the finite-term strong convergence is useful in issues associated with the maximum-likelihood or maximum a posteriori principles.},
	booktitle = {IEEE Transactions on Information Theory},
	pages = {180 - 190}
}
@conference {
	title = {Modeling and control of a magnetostrictive actuator},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2002},
	month = {12/2002},
	abstract = {The rate-dependent hysteresis existing in magnetostrictive actuators presents a challenge in control of these actuators. In this paper we propose a novel dynamical model for the hysteresis in a thin magnetostrictive actuator. The model features the coupling of the Preisach operator with an ordinary differential equation (ODE). We prove the well-posedness of the model, study the parameter identification methods, and propose an inverse control scheme. The effectiveness of the identification and inverse control schemes is demonstrated through experimental results.},
	address = {Las Vegas, Nevada},
	booktitle = {41st IEEE Conference on Decision and Control},
	pages = {pp. 866-872}
}
@conference {
	title = {On-line Detection of Distributed Attacks from Space-time Network Flow Patterns},
	author = {Baras, John S., Cardenas, Alvaro A., Vahid Ramezani},
	year = {2002},
	month = {12/2002},
	abstract = {Parametric and non-parametric change detection algorithms are applied to the problem of detecting changes in the direction of traffic flow. The directionality of the change in a network flow is assumed to have an objective or target. The particular problem of detecting distributed denial of service attacks from distributed observations is presented as a working framework. The performance of our change detection algorithms is evaluated via simulations.},
	address = {Orlando, Florida},
	booktitle = {23rd Army Science Conference}
}
@conference {
	title = {Routing Domain Autoconfiguration for more Efficient and Rapidly Deployable Mobile Networks},
	author = {Manousakis, Kyriakos., McAuley, Anthony J., Morera, Raquel., Baras, John S.},
	year = {2002},
	month = {12/2002},
	abstract = {One approach to achieving scalability in rapidly deployed dynamic networks, such as Future Combat Systems (FCS), is to automatically divide nodes into small (e.g., 30 node) interconnected IP domains and assigning each a routing protocol that best meets the domain{\textquoteright}s characteristics (Morera and McAuley, 2002). Although an attractive idea, it has not been tested. This paper* presents the first realization of domain autoconfiguration through extensions to the IP Autoconfiguration Suite (IPAS) (McAuley et al., 2001; McAuley et al., 2002; Cheng et al., 2002). While IPAS already configures and reconfigures information such as interface IP address and server locations, it assumes a single domain. We describe IPAS enhancements that support the automatic creation and configuration of multiple domains and describe a prototype implementation where interfaces are dynamically assigned to run different routing protocols. Finally, we show some initial performance results that show configuration time for even large (1000 node) sparse networks in a few seconds and small bandwidth overhead (a few hundred bytes per link).},
	address = {Orlando, Florida},
	booktitle = {23rd Army Science Conference}
}
@conference {
	title = {Two Level Hybrid key Scheme for Efficient Key Distribution in Mobile Ad-Hoc Networks},
	author = {Baras, John S., Striki, Maria.},
	year = {2002},
	month = {12/2002},
	abstract = {Military command and control require that information be communicated to the appropriate groups and only with the utmost security. At the same time the environment envisioned by the Objective Force is mobile ad-hoc and consists of a large number of heterogeneous nodes deployed in a hostile field of limited bandwidth and unreliable channels. The nodes of the network may present severe bandwidth, energy, capacity and processing constraints (vary from Satellites, PDAs, laptops, to GPS devices, cellphones and pagers). In this work we develop a secure, robust and scalable key management scheme for multicast communications. This service is very important in determining the security and efficiency of the network. It consists of key generation, entity authentication and key distribution. We assume that the nodes are already authenticated and focus on studying and developing key distribution techniques with the aim to achieve scalability and high performance of our key distribution framework without sacrificing the security level of the network. For that we need to reduce the total storage, communication and computation cost of the nodes, resulting from the key distribution protocol we apply to our network. The new key distribution framework we designed is a hierarchical, two-level hybrid key management scheme.},
	address = {Orlando, Florida},
	booktitle = {23rd Army Science Conference}
}
@conference {
	title = {Generic congestion control through network coordination},
	author = {Liu, Xicheng., Cheung, Cynthia., Baras, John S.},
	year = {2002},
	month = {11/2002},
	abstract = {With the rapid emergence of new services and the quick change of traffic in Internet, the widely used end-to-end congestion control scheme becomes insufficient. This paper proposes a new congestion control architecture based on the coordination among the core router the edge router, and the host. The core router notifies its immediately upstream nodes when it detects incipient congestion. Those nodes then constrain their sending rates to prevent congestion. No per-flow state information is maintained in routers. The application itself need not take care of the rate adaptation. The architecture provides a uniform solution accommodating both responsive and unresponsive traffic with trivial overhead. It reduces the packet loss to zero, and leads to higher network resource utilization. Response time to congestion is greatly reduced. The architecture has been implemented in the Linux kernel, Some preliminary experiments show its advantages.},
	address = {Singapore},
	booktitle = {8th International Conference on Communication Systems},
	pages = {pp. 903-907}
}
@conference {
	title = {Aggregation of heavy-tailed on-off flows is multifractal},
	author = {Liu, Xicheng., Baras, John S.},
	year = {2002},
	month = {11/2002},
	abstract = {We show that the aggregation of heavy-tailed on-off flows can exhibit multifractality in nature in addition to the well-known long-range dependency. Justifications are provided through analyzing the power density spectrum of a single on-off flow, calculating the multifractal spectrum of aggregated flows, and measuring the distributions of the increment process. Effects of the on and the off period on the multifractal behavior are examined. With a new understanding of the on-off model taking into account the TCP window-based control mechanism, possible roles of the TCP window size and the RTT in producing multifractal traffic are suggested.},
	address = {Singapore},
	booktitle = {8th International Conference on Communication Systems},
	pages = {pp. 578-582}
}
@conference {
	title = {Broadcast scheduling in information delivery systems},
	author = {Raissi-Dekhordi, Majid., Baras, John S.},
	year = {2002},
	month = {11/2002},
	abstract = {Information broadcasting is an effective method to deliver popular information packages to a large number of users in wireless and satellite networks. We address the problem of broadcast scheduling in the pull environment and try to solve this problem by formulating it as a dynamic optimization problem. This approach allows us to find a near-optimal scheduling policy, which we use as a benchmark to evaluate a number of other existing heuristic policies. Also, in addition to providing a solution for the usual case with Poisson arrivals and equal priority pages, our approach enables us to address extended versions of this problem with other arrival processes and with distinct weights assigned to different pages.},
	address = {Taipei, Taiwan},
	booktitle = {Global Telecommunications Conference, Taipei},
	pages = {pp. 2935-2939}
}
@conference {
	title = {Reliable multicast for flat hierarchy networks based on adaptive air caching},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2002},
	month = {10/2002},
	abstract = {The evolution of satellite networks in the commercial and military world has pushed the research community towards the solution of important problems related to this kind of networks. One of those important problems is how to design an efficient reliable multicast protocol in a network where there is no hierarchy involved, and the link presents characteristics like high propagation delay and high BER. The existing reliable multicast protocols cannot be applied in the case of flat hierarchy networks, since those are based on intermediate receivers and local recovery techniques. So, we introduce the air caching technique, which serves as a fast access memory that is realized on the air and contains packets for the recovery of corrupted or erroneous data packets at the receivers. In this paper we present some of the protocols that we designed and are based on air caching combined with FEC and ARQ. In the past[7] we have presented protocols that are based on those techniques but the characteristics of the Air Cache were constant. In this paper we propose RM protocols, which are based on adaptive air caching, where the size and/or content of the Air Cache change dynamically based on feedback information. Our goal is to improve the delay and/or bandwidth usage characteristics of the non-adaptive Air Cache RM protocols.},
	address = {Anaheim, CA},
	booktitle = {IEEE Military Communications Conference MILCOM},
	pages = {pp. 1295-1299}
}
@conference {
	title = {TCP over GEO satellite hybrid networks},
	author = {Zhou, Xiaoming., Baras, John S.},
	year = {2002},
	month = {10/2002},
	abstract = {Broadcast satellite networks are going to play an important role in the global information infrastructure. Satellites can provide direct-to-user Internet services and as well as traffic trunks in the middle of the network. About 98\% of Internet traffic is TCP traffic. TCP works well in terrestrial fiber networks, but does not work well in satellite and in hybrid (satellite-terrestrial) networks. We analyze the problems that cause this degraded performance and review the solutions proposed in the literature. Because an end-to-end solution is difficult in the hybrid network, we propose a solution based on connection splitting. While much research has been done on improving TCP throughput for a single connection, we consider the case when multiple connections with different round trip times compete with each other. The crucial part of our scheme is the flow control algorithm at the hybrid gateways (i.e., the interfaces between the satellite and terrestrial networks). Because the end-to-end connection is split at the hybrid gateways, the data packets are buffered at the TCP layer rather than at the IP layer as in a normal router. Furthermore, the TCP layer not only buffers data waiting for transmission, but also buffers data transmitted but not yet acknowledged. The flow control algorithm should avoid stall caused by buffer exhaustion, guarantee fairness among all competing connections and maintain high utilization of the satellite link. A performance evaluation demonstrates that our scheme meets these requirements.},
	address = {Anaheim, CA},
	booktitle = {Military Communications Conference},
	pages = {pp. 29-34}
}
@conference {
	title = {Intrusion Detection with Support Vector Machines and Generative Models},
	author = {Baras, John S., Rabi, Maben.},
	year = {2002},
	month = {09/2002},
	abstract = {This paper address the task of detecting intrusions in the form of malicious attach on programs running OD a host computer system by inspecting the trace of system calls made by these programs. We use {\textquoteright}attack-tree{\textquoteright} type generative models for such intrusions to select features that are used by a Support Vector Machine Classifier. Our approach combines the ability of an HMM generative model to handle variable-length strings, i.e. the traces, and the non-asymptotic nature of Support Vector Machines that permits them to work well with small training sets.},
	address = {Sao Paulo, Brazil},
	booktitle = {5th International Conference, ISC 2002, Springer lecture notes in Computer Science (LNCS)},
	pages = {pp 32-47}
}
@conference {
	title = {INORA-A Unified Signaling and Routing Mechanism for QoS Support in Mobile Ad Hoc Networks},
	author = {Dharmaraju, Dinesh., Roy-Chowdhury, Ayan., Hovareshti, Pedram., Baras, John S.},
	year = {2002},
	month = {08/2002},
	abstract = {Mobile Ad hoc NETworks(MANET) are characterized by bandwidth constrained wireless links, multiple hops and highly dynamic topologies. Providing QoS support in MANETs is hence a challenging task. This paper presents the design, implementation and evaluation of INORA, which is a network layer QoS support mechanism that makes use of the INSIGNIA in-band signaling mechanism and TORA routing protocol for MANETs. TORA provides multiple routes between a given source and destination. We present an effective coupling between TORA and INSIGNIA to get routes that are {\textquotedblleft}best-able{\textquotedblright} to provide QoS requirements for a flow. INORA also combines congestion control with routing},
	address = {Vancouver, Canada},
	booktitle = {International Conference on Parallel Processing Workshops},
	pages = {pp. 86-93},
	organization = {British Columbia}
}
@conference {
	title = {Tool wear estimation from acoustic emissions: a model incorporating wear-rate},
	author = {Varma, Sudhir., Baras, John S.},
	year = {2002},
	month = {08/2002},
	abstract = {Almost all prior work on modeling the dependence of acoustic emissions on tool wear have concentrated on the effect of wear-level on the sound. We give justification for including the wear-rate information contained in the sound to improve estimation of wear. A physically meaningful model is proposed which results in a hidden Markov model (HMM) whose states are a combination of the wear-level and rate and observations are the feature vectors extracted from the sound. We also present an efficient method for picking feature vectors that are most useful for the classification problem.},
	address = {Quebec City, CA},
	booktitle = {16th International Conference on Pattern Recognition},
	pages = {pp. 492-495}
}
@conference {
	title = {Combined Research and Curriculum Development in Information centric Systems Engineering},
	author = {Austin, Mark A., Baras, John S., Kositsyna, N. I.},
	year = {2002},
	month = {07/2002},
	abstract = {This paper describes a multidisciplinary program of research and curriculum development in Information-Centric Systems Engineering currently underway at the Institute for Systems Research, University of Maryland, College Park. This work is supported by a significant grant from the National Science Foundation and industrial funds from US industry. After motivating the need for an information-centric approach to systems engineering education, this paper describes the research methodology, pathway from research to curriculum development and teaching, and architecture for web-based project deliverables.},
	address = {Las Vegas, Nevada},
	booktitle = {12th Annual INCOSE Symposium}
}
@conference {
	title = {Dynamic Adaptive Routing in MANETs: New Algorithms Using Swarm Intelligence},
	author = {Baras, John S.},
	year = {2002},
	month = {07/2002},
	address = {Adelphi, Maryland},
	booktitle = {Distinguished Lecture, Army Research Laboratory, }
}
@conference {
	title = {Dynamic Resource Allocation in Next Generation High Data Rate (Ka-Band) Satellites},
	author = {Baras, John S.},
	year = {2002},
	month = {06/2002},
	booktitle = {2002 Workshop on High Speed Networks, part of Infocom 2002}
}
@conference {
	title = {Alternative Network Architectures for Supporting Communications From the International Space Station},
	author = {Nguyen, Alex T., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2002},
	month = {05/2002},
	abstract = {In order to support the communications needs of the International Space Station (ISS), alternative communications architectures to provide broadband support need to be considered. We address three communications options and evaluate an architecture for the direct to ground option, which could serve as an intermediary solution to satisfy near term communications needs of commercial experiments and payloads on the ISS and overcome certain limitations of the current ISS communications infrastructure. We focus on a particular user{\textquoteright}s requirements, and examine the system{\textquoteright}s communications links, and coverage availability. These parameters, along with high-level cost estimates, are compared to using commercial relay satellites, and an enhanced TDRSS. The direct to ground option is viable for store-and-forward applications and cost comparable to commercial constellations, but TDRSS is the choice for realtime or continuous data applications.},
	address = {Quebec, Canada},
	booktitle = {20th AIAA International Communication Satellite systems Conference and Exhibit},
	pages = {pp. 1-10},
	organization = {Montreal}
}
@conference {
	title = {Cross-disciplinary Systems Issues in Undergraduate Engineering Education},
	author = {Baras, John S.},
	year = {2002},
	month = {05/2002},
	address = {Avchorage, Alaska},
	booktitle = {NSF Workshop on the Research Needs in the Modeling, Dynamics, Control and Monitoring of Complex Engineering Systems, part of the American Control Conference}
}
@conference {
	title = {Cross-Departmental Undergraduate Control and Systems Education},
	author = {Baras, John S.},
	year = {2002},
	month = {05/2002},
	address = {Anchorage, Alaska},
	booktitle = {2nd Automatic Control Conference}
}
@techreport {
	title = {A direct-to-ground architecture for supporting Commercial Communications from the International Space Station},
	author = {Nguyen, Alex T., Zhou, Xiangrong., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {We outline the first steps of an effort to start defining a communications architecture for supporting broadband data communications from the International Space Station. We address three communications options and focus on a direct-to-ground architecture, which could serve as an intermediary solution to satisfy near-term communications needs of commercial experiments and payloads on the ISS and overcome certain limitations of the current ISS communications infrastructure. A high-level analysis of the architecture for the direct to ground option is performed, focusing on a particular user{\textquoteright}s requirements, communications links, and coverage availability. We also discuss system, mobility support and protocol issues that need to be addressed for this solution to be a feasible alternative.},
	address = {New York, NY}
}
@conference {
	title = {A direct-to-ground architecture for supporting commercial communications from the International Space Station},
	author = {Nguyen, Alex T., Zhou, Xiangrong., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2002},
	month = {04/2002},
	abstract = {We outline the first steps of an effort to start defining a communications architecture for supporting broadband data communications from the International Space Station. We focus on a direct-to-ground architecture, which could serve as an intermediate solution to satisfy the near term communications needs of commercial experiments and payloads on the ISS and overcome certain limitations of the current ISS communications infrastructure. We address three communications options and evaluate an architecture for the direct-to-ground option, focusing on a particular user{\textquoteright}s requirements, communications links, and coverage availability. We also discuss system, mobility support and protocol issues that need to be addressed for this solution to be a feasible alternative.},
	address = {New York, NY},
	booktitle = {IEEE International Conference on Communications},
	pages = {pp. 2989-2993}
}
@conference {
	title = {On Trust Establishment in Mobile Ad-Hoc Networks},
	author = {Eschenauer, Laurent., Gligor, Virgil D., Baras, John S.},
	year = {2002},
	month = {04/2002},
	abstract = {We present some properties of trust establishment in mobile, ad-hoc networks and illustrate how they differ from those of trust establishment in the Internet. We motivate these differences by providing an example of ad-hoc network use in battlefield scenarios, yet equally practical examples can be found in non-military environments. We argue that peer-to-peer networks are especially suitable to solve the problems of generation, distribution, and discovery of trust evidence in mobile ad-hoc networks, and illustrate the importance of evaluation metrics in trust establishment.},
	address = {Cambridge, UK},
	booktitle = {10th International Workshop on Security Protocols},
	pages = {pp. 47-66}
}
@conference {
	title = {Optimal Control of Hysteresis in Smart Actuators: A Viscosity Solution Approach},
	author = {Tan, Xiaobo., Baras, John S.},
	year = {2002},
	month = {03/2002},
	abstract = {Hysteresis in smart materials hinders their wider applicability in actuators. The low dimensional hysteresis models for these materials are hybrid systems with both controlled switching and autonomous switching. In particular, they belong to the class of Duhem hysteresis models and can be formulated as systems with both continuous and switching controls. In this paper, we study the control methodology for smart actuators through the example of controlling a commercially available magnetostrictive actuator. For illustrative purposes, an infinite horizon optimal control problem is considered. We show that the value function satisfies a Hamilton-Jacobi-Bellman equation (HJB) of a hybrid form in the viscosity sense. We further prove uniqueness of the viscosity solution to the (HJB), and provide a numerical scheme to approximate the solution together with a sub-optimal controller synthesis method. Numerical and experimental results based on this approach are presented.},
	address = {Palo Alto, CA},
	booktitle = {5th International Workshop on Hybrid Systems: Computation and Control, Springer Lecture notes in Computer Science(LNCS)},
	pages = {pp.451-464}
}
@conference {
	title = {Stochastic Dynamic Models for Internet Traffic and Congestion Control},
	author = {Baras, John S.},
	year = {2002},
	month = {02/2002},
	address = {Atlanta, Georgia},
	organization = {Georgia Institute of Technology}
}
@conference {
	title = {Dynamic Models for Internet Congestion Control: A Control Perspective},
	author = {Baras, John S.},
	year = {2001},
	month = {12/2001},
	address = {Greece},
	organization = {National Technical University of Athens}
}
@conference {
	title = {An Information-Theoretic Approach for Design and Analysis of Rooted-Tree-Based Multicast Key Management Schemes},
	author = {Poovendran, Radha., Baras, John S.},
	year = {2001},
	month = {11/2001},
	booktitle = {IEEE Transactions on Information Theory},
	pages = {pp.2824-2834}
}
@conference {
	title = {A Framework for Supporting Intelligent Fault and Performance Management for Communication Networks},
	author = {Li, Hongjun., Baras, John S.},
	year = {2001},
	month = {10/2001},
	abstract = {In this paper, we present a framework for supporting intelligent fault and performance management for communication networks.Belief networks are taken as the basis for knowledge representation and inference under evidence. When using belief networks for diagnosis, we identify two questions: When can I say that I get the right diagnosis and stop? If right diagnosis has not been obtained yet, which test should I choose next? For the first question, we define the notion of right diagnosis via the introduction of intervention networks. For the second question, we formulate the decision making procedure using the framework of partially observable Markov decision processes. A heuristic dynamic strategy is proposed to solve this problem and the effectiveness is shown via simulation.},
	address = {Chicago, Illinois},
	booktitle = {IFIP / IEEE MMNS 2001},
	pages = {pp. 227-240}
}
@conference {
	title = {Scalable and robust reliable multicast for satellite networks},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2001},
	month = {10/2001},
	abstract = {The evolution of satellite applications has created new traffic patterns on satellite links. That is because the number of users demanding service from satellite links has increased tremendously. The result is a more sophisticated use of resources. One way of accomplishing that is by multicasting, which is a natural extension of the broadcast nature of the satellite medium. Numerous existing satellite applications demand reliable delivery of the transmitted data, which is opposed to the unreliable nature of multicast transmission due to the error prone satellite medium. We have designed a number of reliable multicasting protocols which are based on forward error correction (FEC) and air caching. The combination of those two techniques results in a significant boost in the performance of reliable multicasting protocols.},
	address = {VA, USA},
	booktitle = {Military Communications Conference, McLean},
	pages = {pp. 676-680}
}
@conference {
	title = {Stochastic Dynamic Models of TCP, Extensions and Marking: A Control Perspective},
	author = {Baras, John S.},
	year = {2001},
	month = {10/2001},
	address = {Lawrence, Kansas},
	booktitle = {Stochastic Theory and Control Conference, honoring Professor Tyrone Duncan on his 60th birthday},
	organization = {University of Kansas}
}
@conference {
	title = {Commercial Broadband Communications To/From the ISS: a SatCom Interoperability Testbed},
	author = {Baras, John S.},
	year = {2001},
	month = {10/2001},
	address = {Cape Canaveral, Florida},
	booktitle = {ISS Utilization Conference}
}
@conference {
	title = {Group Communication Security and Key Management for Hybrid and Satellite Networks},
	author = {Baras, John S.},
	year = {2001},
	month = {10/2001},
	address = {Gaithersburg, MD},
	organization = {Hughes Network Systems}
}
@conference {
	title = {An Efficient Run-To-Run Controller : ESET},
	author = {Zhang, Chang.},
	year = {2001},
	month = {10/2001},
	abstract = {The EWMA run-to-run (RtR) controller is easy to deploy and can effectively deal with small disturbances. But it can not compensate for shifts (step disturbances) and large model errors well. The common solution to such a problem is to use the SPC to detect the occurrence of a shift and them remove the cause of the shift or apply a rapid mode. In this paper, a novel approach to handle shifts and large model errors is proposed: the SVR-MOVE controller is used to compensate for a shift when it is detected. The SVR-MOVE controller is very efficient to handle shifts and large model errors. On the other hand, a well-tuned EWMA controller may outperform a coarsely tuned SVR-MOVE controller when the disturbances are smooth drifts. It is much easier to tune the parameters of the EWMA controller than that of the SVR-MOVE controller. Our new controller, named ESET, has the advantage of both controllers. Simulation shows that the ESET outperforms the EWMA controller and the SVR-MOVE controller in most situations.},
	address = {Alberta, Canada},
	booktitle = {AEC/APC Symposium XIII},
	pages = {pp. 1-4},
	organization = {Banff}
}
@conference {
	title = {Interoperability Challenges for Global Wireless Internetworks},
	author = {Baras, John S.},
	year = {2001},
	month = {06/2001},
	address = {Moffett Field, CA},
	booktitle = {Mobile Terrestrial and Space Networking Workshop: Supporting the Scientific Community},
	organization = {NASA Ames Research Center}
}
@conference {
	title = {Hybrid Information Internetworks},
	author = {Baras, John S.},
	year = {2001},
	month = {06/2001},
	organization = {Boeing-wide}
}
@conference {
	title = {Effect of Exponential Averaging on the variability of a RED Queue},
	author = {Misra, Archan., Ott, Teunis., Baras, John S.},
	year = {2001},
	month = {06/2001},
	abstract = {The paper analyzes how using a longer memory of the past queue occupancy in computing the average queue occupancy affects the stability and variability of a RED queue. Extensive simulation studies with both persistent and Web TCP sources are used to study the variance of the RED queue as a function of the memory of the averaging process. Our results show that there is very little performance improvement (and in fact, possibly significant performance degradation) if the length of memory is increased beyond a very small value. Contrary to current practice, our results show that a longer memory reduces the negative correlation typically observed among the windows of the constituent TCP flows, and hence, suggest the use of the instantaneous queue occupancy in practical RED queues.},
	address = {Helsinki, Finland},
	booktitle = {IEEE International Conference on Communications (ICC) 2001},
	pages = {pp. 1817-1823}
}
@conference {
	title = {Wireless Internetworks: Information to the User},
	author = {Baras, John S.},
	year = {2001},
	month = {06/2001},
	booktitle = { Technology Council of Maryland meeting with theme {\textquotedblleft}Unwired and still Connected{\textquotedblright}},
	organization = {Howard County Center for Business and Technology Development}
}
@conference {
	title = {Biologically-Inspired Acoustic Wear Analysis},
	author = {Varma, Sudhir., Baras, John S., Shamma, S A. },
	year = {2001},
	month = {06/2001},
	address = {Baltimore, Maryland},
	booktitle = {NSIP: 2001 IEEE-EURASIP Workshop on Nonlinear Signal and Image Processing}
}
@conference {
	title = {System designs for adaptive, distributed network monitoring and control},
	author = {Li, Hongjun., Yang, Shahan., Xi, Haifeng., Baras, John S.},
	year = {2001},
	month = {05/2001},
	abstract = {We present system designs for adaptive, distributed network monitoring and control. The ideas are to distribute some processing intelligence to network elements, and to design a dynamic interface such that the delegated agents could be managed remotely by the manager. The functionality of the delegated agents, and even that of the native software processes, could be extended dynamically without recompilation. The creation, deployment, operation, and management of the delegated agents require a standard infrastructure on each system where these agents need to be hosted. We use Java technology and C/C++ dynamic linkage mechanism to fulfill such a requirement under different situations and our system designs span a wide scope of applications},
	address = {Seattle, WA},
	booktitle = {IEEE/IFIP International Symposium on Integrated Network Management}
}
@conference {
	title = {Internet over Satellite: Metrology, Traffic Models, New Protocols and Applications},
	author = {Baras, John S.},
	year = {2001},
	month = {05/2001},
	address = {Arlington, Virginia},
	booktitle = {Telecommunications Industry Association technical standards group},
	organization = {TIA headquarters}
}
@conference {
	title = {On the Negotiation of Access Control Policies},
	author = {Gligor, Virgil D., Koleva, Radostina. , Bharadwaj, Vijay G., Baras, John S.},
	year = {2001},
	month = {04/2001},
	abstract = {Although the notion of negotiation has been used extensively in secure communication protocols to establish common keying states, protocol modes and services, this notion is only now emerging in the area of access control policies. In this paper, we review the motivation for access policy negotiation and we provide some examples of use in practice. In particular, we illustrate the meaning, the types, and the process of negotiation for establishing common access states and common interpretations of policy models for dynamic coalitions and large-scale access control in the Internet.},
	address = {Cambridge, United Kingdom},
	booktitle = {Security Protocols, Proceedings of 9th International Workshop},
	pages = {pp. 188-201}
}
@conference {
	title = {Introducing Air Caching Techniques for Boosting Reliable Multicasting for Satellite Networks},
	author = {Manousakis, Kyriakos., Baras, John S.},
	year = {2001},
	month = {03/2001},
	abstract = {The emergence of satellite networks and the demand for reliability in transferring large files over the network via satellites has created the need for building effective reliable multicasting protocols, customized for this kind of networks. During the previous years, several protocols and techniques have been proposed to address the demanding problem of reliability in multicasting protocols. In our study we are trying to give a different perspective to the work that already has been done, with the use of Air Caching. The combined use of this technique along with the use of forward error correction (FEC) can boost substantially the performance of reliable protocols in terms of transmission rounds, by paying a small overhead in bandwidth usage. We present three protocols, the UDPAC (Unchanged Data Packets in Air Cache), the RDPAC (Replace Data Packets in Air Cache) and the PPAC (Parity Packets inAir Cache). The performance of these three protocols, in terms of Transmission Rounds and robustness in erroneous environments, is compared with two already known protocols, which are based on the simple ARQ and the FEC, respectively.},
	address = {College Park, Maryland},
	booktitle = {5th ARL Federated Laboratory Symposium},
	pages = {pp. 1-6},
	organization = {University of Maryland}
}
@conference {
	title = {Network Design Using Hierarchical Performance Models and Multi-Criteria Optimization},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2001},
	month = {03/2001},
	abstract = {Network design and dimensioning often involve trade-offs between different objectives that sometimes may have opposing effects on design. At the same time, some objectives are mandatory while others are optional. In this paper we use the multi-objective optimization package CONSOL-OPTCAD for the design trunk reservation parameters. We also study link capacity design by using CFSQP along with our model and its sensitivities generated by Automatic Differentiation (AD). Using AD for sensitivity analysis of our reduced load approximation is a novel approach. Using AD for computing derivatives of the fixed point along with the calculation of the fixed point itself is both accurate and efficient. Putting together these techniques we present a systematic way of network design, regardless of the details of the underlying performance evaluation model.},
	address = {College Park, Maryland},
	booktitle = {5th ARL Federated Laboratory Symposium},
	pages = {pp. 1-6},
	organization = {University of Maryland}
}
@conference {
	title = {Information Centric Systems Engineering},
	author = {Baras, John S.},
	year = {2001},
	month = {02/2001},
	booktitle = {Systems Engineering Subcouncil of Lockheed Martin Corporation}
}
@conference {
	title = {Information Theoretic Methods for Evaluating Key Distribution Schemes in Multicast},
	author = {Baras, John S.},
	year = {2001},
	month = {02/2001},
	address = {Athens, Greece},
	organization = {National Technical University of Athens}
}
@conference {
	title = {Integrated Product and Process Design of Microwave Modules Using AI Planning and Integer Programming},
	author = {Nau, Dana S., Ball, Mike., Baras, John S., Chowdhury, Abdur., Lin, Edward., Meyer, Jeff., Rajamani, Ravi., Splain, John., Trichur, Vinai.},
	year = {2001},
	month = {01/2001},
	abstract = {A This paper describes the process planning techniques we developed for use in an Integrated Product and Process Design (IPPD) tool for the design and manufacture of microwave transmit/receive modules. Given a collection of data about the design of a microwave module, the IPPD tool uses a combination of AI planning and optimization-based tradeoff analysis to produce a collection of alternative designs and alternative process plans that have Pareto optimal values for manufacturing and purchasing lead time, process yield, cost, and number of suppliers. The IPPD tool provides facilities to enable the user to generate and examine these Pareto optimal alternatives in real time, in order to provide immediate feedback on how to modify the design to improve its cost and productivity.},
	booktitle = {4th Workshop on Knowledge Intensive CAD, Kluwer Academic Publishers,},
	pages = {pp.186-196.}
}
@conference {
	title = {A learning algorithm for Markov decision processes with adaptive state aggregation},
	author = {Baras, John S., Borkar, V.S, V. S. },
	year = {2000},
	month = {12/2000},
	abstract = {We propose a simulation-based algorithm for learning good policies for a Markov decision process with unknown transition law, with aggregated states. The state aggregation itself can be adapted on a slower time scale by an auxiliary learning algorithm. Rigorous justifications are provided for both algorithms.},
	address = {Sydney, Australia},
	booktitle = {Proceedings of the IEEE Conference on Decision and Control},
	pages = {pp.3351-3356}
}
@conference {
	title = {Performance Analysis Using a Hierarchical Loss Network Model},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2000},
	month = {11/2000},
	abstract = {In this paper we present a hierarchical loss network model for estimating the end-to-end blocking probabilities of large networks. As networks grow in size, nodes tend to form clusters geographically and hierarchical routing schemes are more commonly used. Loss network and reduced load models are often used to approximate end-to-end call blocking probabilities and hence throughput. However so far all work being done in this area is for flat networks with flat routing schemes. We aim at developing a more efficient approximation method for networks that have a natural hierarchy and/or when some form of hierarchical routing policy is used. We present two hierarchical models in detail for fixed hierarchical routing and dynamic hierarchical routing policies, respectively, via the notion of network abstraction, route segmentation, traffic segregation and aggregation. Computation is done separately within each cluster (local) and among clusters (global), and the fixed point is obtained by iteration between local and global computations. We present results from both numerical experiments and discrete event simulations.},
	address = {San Fransisco, CA},
	booktitle = {IEEE Globecom 2000,Comunications: The Global Bridge},
	pages = {pp. 1793-1797}
}
@conference {
	title = {Generalized TCP Congestion Avoidance and Its Effect on Bandwidth Sharing and Variability},
	author = {Misra, Archan., Baras, John S., Ott, Teunis.},
	year = {2000},
	month = {11/2000},
	abstract = {To model possible suggested changes in TCP window adaptation in response to randomized feedback, such as ECN, we formulate a generalized verslon of the TCP congestion avoidance algorithm. We first consider multiple such generalized TCP flows sharing a bottleneck buffer under the Assured Service model and use a fixed point technique to obtain the mean window sizes and throughputs for the TCP flows. To further study how changes in the adaptation algorithm affect the variability in the throughput, we use an analytical-cum-numerical technique to derive the window distribution (and related statistics) of a single generalized flow under state-dependent randomized congestion feedback.},
	address = {San Francisco, California},
	booktitle = {IEEE Global Telecommunications Conference (GLOBECOM), Communications: The Global Bridge},
	pages = {pp. 329-337.}
}
@conference {
	title = {Maximum Likelihood Slow Frequency-Selective Fading Channel Estimation Using Frequency Domain approach},
	author = {Jiang, Yimin., Sun, Feng-Wen., Baras, John S.},
	year = {2000},
	month = {11/2000},
	abstract = {This paper addresses the channel estimation problem for slow frequency-selective fading channels using training sequences and the maximum likelihood (ML) approach. In the literature people usually assume a symbol period spaced delay-tapped-line model and additive white Gaussian noise (AWGN). Due to the pre-filtering in the receiver front end, if the sampling rate is larger than one sample per symbol or sampling epoch is unknown (Le., the timing information is unavailable), the AWGN model is not valid anymore. A more general ML channel estimation method using the discrete Fourier transform (DFT) is derived for colored Gaussian noise and over-sampling. A similar idea can be adopted to derive the ML joint carrier phase and timing offsets estimation algorithm.},
	address = {San Francisco, CA},
	booktitle = {IEEE Globecom2000, Communications:The Global Bridge},
	pages = {pp. 955-959}
}
@conference {
	title = {Using Drop{\textendash}Biasing to stabilize the Occupancy of Random-Drop Queues with TCP Traffic},
	author = {Misra, Archan., Ott, Teunis., Baras, John S.},
	year = {2000},
	month = {11/2000},
	abstract = {The paper describes how the use of {\textquoteleft}drop-biasing{\textquoteright}, a technique to control the distribution of the gap between consecutive packet losses in random drop queues (such as RED) can be used to reduce the variability of the queue occupancy with TCP traffic. Reducing the variance of the queue occupancy reduces delay jitter for buffered packets, as well as decreases the likelihood of buffer underflow. We find that modifying the packet drop probabilities to ensure a minimum separation between consecutive packet drops serves to decrease the variability in the queue occupancy. This is really achieved as a result of the increased negative correlation among the congestion windows of the constituent TCP flows. Such negative correlation explains why the use of simple drop-biasing strategies can reduce the queue variability without increasing the likelihood of bursts of packet losses. The results of our investigations have relevance for the design and deployment of RED-like algorithms for congestion control in the Internet.},
	address = {Singapore},
	booktitle = {IEEE International Conference on Communications Systems(ICCS)},
	pages = {pp. 1-9}
}
@conference {
	title = {The Set-Valued Run-to-Run Controller with Ellipsoid Approximation},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2000},
	month = {09/2000},
	address = {Lake Tahoe, Nevada},
	booktitle = {AEC/APC Symposium XII},
	pages = {pp. 167-178}
}
@conference {
	title = {Comparison of Run-to-Run Control Methods in Semiconductor Manufacturing Processes},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2000},
	month = {09/2000},
	abstract = {In this paper, RtR control methods are generalized. The set-valued RtR controllers with ellipsoid approximation are compared with other RtR controllers by simulation according to the following principles:

A good RtR controller should be able to compensate for various disturbances, such as small drifts and ~large step disturbances.~
	It should be able to deal with constraints, cost requirement, multiple targets,~time delays etc.
Preliminary results show the satisfactory performance of the set-valued RtR controller with ellipsoid approximation.~},
	address = {Lake Tahoe, Nevada},
	booktitle = {AEC/APC Symposium XII},
	pages = {pp. 889-896}
}
@conference {
	title = {Analysis of the Dynamics of TCP Congestion Avoidance: Random Drops and Random Marking of Queues},
	author = {Baras, John S.},
	year = {2000},
	month = {08/2000},
	address = {Sophia-Antipolis, France},
	organization = {INRIA}
}
@conference {
	title = {Internet and Web Metrology: The Keys to High Performance},
	author = {Baras, John S.},
	year = {2000},
	month = {06/2000},
	address = {Virginia},
	booktitle = {Research and Network Management Personnel },
	organization = {AOL Headquarters}
}
@conference {
	title = {Group Invariance and Symmetries in Nonliear Control and Estimation},
	author = {Baras, John S.},
	year = {2000},
	month = {06/2000},
	abstract = {We consider nonlinear filtering problems, nonlinear robust control problems and the partial differential equations that characterize their solutions. These include the Zakai equation, and in the robust control case two coupled Dynamic Programming equations. We then characterize equivalence between two such problems when we can compute the solution of one from the solution of the other using change of dependent, independent variables and solving an ordinary differential equation. We characterize the resulting transformation groups via their Lie Algebras. We illustrate the relationship of these results to symmetries and invariances in physics, Noether{\textquoteright}s theorem, and calculus of variations. We show how using these techniques one can solve nonlinear problems by reduction to linear ones.},
	address = {Paris, France},
	booktitle = {Proceedings of the Second Nonlinear Control Network (NCN) Workshop}
}
@conference {
	title = {Group Invariance and Symmetries in Nonlinear Control and Estimation},
	author = {Baras, John S.},
	year = {2000},
	month = {06/2000},
	abstract = {We consider nonlinear filtering problems, nonlinear robust control problems and the partial differential equations that characterize their solutions. These include the Zakai equation, and in the robust control case two coupled Dynamic Programming equations. We then characterize equivalence between two such problems when we can compute the solution of one from the solution of the other using change of dependent, independent variables and solving an ordinary differential equation. We characterize the resulting transformation groups via their Lie Algebras. We illustrate the relationship of these results to symmetries and invariances in physics, Noether{\textquoteright}s theorem, and calculus of variations. We show how using these techniques one can solve nonlinear problems by reduction to linear ones.},
	address = {Paris, France},
	booktitle = {Second Nonlinear Control Network (NCN) Workshop, Nonlinear Control in the Year 2000},
	pages = {pp. 01-30}
}
@conference {
	title = {On the True Cramer-Rao lower Bound for Data{\textendash}Aided Joint Estimation of Carrier phase and Timing Offsets},
	author = {Jiang, Yimin., Sun, Feng-Wen., Baras, John S.},
	year = {2000},
	month = {06/2000},
	abstract = {This paper concerns the Cramer-Rao lower bound (CRB) for the data-aided (DA) timing and/or phase recovery, i.e., the synchronization parameter acquisition is aided by a training sequence known to the receiver. For the DA parameter estimation, the CRB typically varies with the training sequence. This indicates that different training sequences offer fundamental different performance. In this manuscript, we derive a closed-form formula of the CRB for timing and phase recovery with respect to any particular training sequence. The bound illustrates the close relation between the training sequence and the fundamental limit on timing and phase synchronization. It provides additional insights on the training sequence design.},
	address = {New Orleans},
	booktitle = {IEEE International Conference on Communication (ICC\&rsquo;00)}
}
@conference {
	title = {Computational Micromagnetics for Magnetostrictive Actuators},
	author = {Tan, Xiaobo., Baras, John S., Krishnaprasad, P S.},
	year = {2000},
	month = {05/2000},
	abstract = {Computational micromagnetics plays an important role in design and control of magnetostrictive actuators. A systematic approach to calculate magnetic dynamics and magnetostriction is presented. A method is developed to solve the coupled Landau-Lifshitz-Gilbert equation for dynamics of magnetization and the 1-D elastic motion equation. A hierarchical algorithm using multipole approximation speeds up the evaluation of the demagnetizing eld, reducing computational cost from O(N2) to O(NlogN). A hybrid 3D-1D scheme is adopted to compute the magnetostriction. Numerical results include domain wall dynamics, hysteresis, magnetostriction, and applications to control of actuators.},
	address = {Philadelphia, Pennsylvania},
	booktitle = {3rd SIAM Conference on Mathematical aspects of Materials Science}
}
@conference {
	title = {A decision-process analysis of implicit coscheduling},
	author = {Poovendran, Radha., Keleher, P. , Baras, John S.},
	year = {2000},
	month = {05/2000},
	abstract = {This paper presents a theoretical framework based on Bayesian decision theory for analyzing recently reported results on implicit coscheduling of parallel applications on clusters of workstations. Using probabilistic modeling, we show that the approach presented can be applied for processes with arbitrary communication mixes. We also note that our approach can be used for deciding the additional spin times in the case of spin-yield. Finally, we present arguments for the use of a different notion of fairness than assumed by prior work.},
	address = {Cancun, Mexico},
	booktitle = {International Parallel and Distributed Processing Symposium, IPDPS}
}
@conference {
	title = {Reliable Multicasting via Satellite : Delay Considerations},
	author = {Payne, Stephen Marshall., Baras, John S.},
	year = {2000},
	month = {03/2000},
	abstract = {Many different multicast protocols have been proposed and analysed in the current literature.Since satellites are naturally a broadcast medium,multicast communications have a potential to greatly benefit from their wide scale deployment. The performance of reliable multicast protocols needs to be studied and becomes better understood over networks including satellite links.},
	address = {College Park, MD},
	booktitle = {ATIRP 4th Annual Conference},
	organization = {University of Maryland}
}
@conference {
	title = {Vehicle Classification Using Acoustic Data Based on Biology Hearing Models and Multiscale Vector Quantization},
	author = {Depireux, Didier A., Varma, Sudhir., Baras, John S., Srour, N., Pham, T.},
	year = {2000},
	month = {03/2000},
	abstract = {The army is interested in using acoustic sensors in the battlefield to perform vehicle identification~ using passive microphone and seismic arrays. The main advantages of acoustic arrays are that they are non-line of sight, low cost, low power, can be made small and rugged and can provide 360o coverage. Their capability includes target detection, bearing, tracking, classification and identification, and can provide wake-up and cueing for other sensors.

Acoustic arrays can be deployed in an expandable tracking system: the outputs of a nework of acoustic arrays can detect, track, and identify ground targets at tactical range by triangulating the reports from several distributed arrays.

Here, we present a prototype of~ vehicle acoustic signal classification. To analyze the signature of the vehicle, we adopt biologically motivated feature extraction models. Several possible representations are used in a classification system. Different vector quantization(VQ) clustering algorithms are implemented and tested for real world vehicle acoustic signal, such as Learning VQ, Tree-Structured VQ and Parallel TSVQ. Experiments on the Acoustic-seismic Classification Identification Data Set~ (ACIDS) database show that both PTSVQ and LVQ achieve high classification rates.

The VQ schemes presented here have the advantage of not having to choose explicitly the features that distinguish~ the targets. The burden is shifted to having to choose the {\textquoteleft}{\textquoteleft}best{\textquoteright}{\textquoteright} representation for the classifier.},
	address = {College Park, MD},
	booktitle = {ARL Federated Laboratory 4th Annual Symposium}
}
@conference {
	title = {A Hierarchical Loss Network Model For Performance Evaluation},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2000},
	month = {03/2000},
	abstract = {In this paper we present a hierarchical loss network model for estimating the end to end blocking probabilties for large networks .As network grows in size,nodes tend to form clusters geographically and hierarchical routing schemes are more commonly used. Loss networks are reduced load models are often used to approximate end to end call blocking probabilities and hence throughput.},
	address = {College Park, Maryland},
	booktitle = {ATIRP 4th Annual Conference},
	organization = {University of Maryland}
}
@conference {
	title = {Analysis and Design of Robust Key Schemes for Multicast Communications},
	author = {Poovendran, Radha., Baras, John S.},
	year = {2000},
	month = {03/2000},
	abstract = {Recent literature presents several rooted tree based member deletion/revocation schemes [5,6,7,8,1,2] trying to simultaneously minimize the key storage while providing efficient member deletion /revocation. many of these approaches have different solutions and provide different values for the number of keys to be stored and distributed.In this paper we show these problems can be systematically studied using basic concepts from information theory.},
	booktitle = {ATIRP 4th Annual Conference},
	organization = {University of Maryland}
}
@conference {
	title = {Fast Evaluation of Demagetizing Field in Three Dimensional Micromagnetics Using Multipole Approximation},
	author = {Tan, Xiaobo., Baras, John S., Krishnaprasad, P S.},
	year = {2000},
	month = {03/2000},
	abstract = {Computational micromagnetics in three dimensions is of increasing interest with the development of magnetostrictive sensors and actuators. In solving the Landau-Lifshitz-Gilbert (LLG) equation, the governing equation of magnetic dynamics for ferromagnetic materials, we need to evaluate the effective field. The effective field consists of several terms, among which the demagnetizing field is of long-range nature. Evaluating the demagnetizing field directly requires work of O(N2) for a grid of N cells and thus it is the bottleneck in computational micromagnetics. A fast hierarchical algorithm using multipole approximation is developed to evaluate the demagnetizing field. We first construct a mesh hierarchy and divide the grid into boxes of different levels. The lowest level box is the whole grid while the highest level boxes are just cells. The approximate field contribution from the cells contained in a box is characterized by the box attributes, which are obtained via multipole approximation. The algorithm computes field contributions from remote cells using attributes of appropriate boxes containing those cells, and it computes contributions from adjacent cells directly. Numerical results have shown that the algorithm requires work of O(NlogN) and at the same time it achieves high accuracy. It makes micromagnetic simulation in three dimensions feasible},
	address = {Newport Beach, CA},
	booktitle = {7th SPIE International Symposium on Smart Structures and Materials},
	pages = {pp. 195-201}
}
@conference {
	title = {Computational Micromagnetics for Magnetostrictive Actuators},
	author = {Tan, Xiaobo., Baras, John S., Krishnaprasad, P S.},
	year = {2000},
	month = {03/2000},
	abstract = {Computational micromagnetics plays an important role in design and control of magnetostrictive actuators. A systematic approach to calculate magnetic dynamics and magnetostriction is presented. A method is developed to solve the coupled Landau-Lifshitz-Gilbert equation for dynamics of magnetization and the 1-D elastic motionequation.},
	address = {Newport Beach, CA},
	booktitle = {7th SPIE International Symposium on Smart Structures and Materials},
	pages = {pp. 162-173}
}
@conference {
	title = {Integrating AI Planning and Integer Programming for Use in Integrated Product and Process Design},
	author = {Nau, Dana S., Meyer, Jeff., Ball, Mike., Baras, John S., Chowdhury, Abdur., Lin, Edward., Rajamani, Ravi., Splain, John., Trichur, Vinai.},
	year = {2000},
	month = {01/2000},
	abstract = {This paper describes an Integrated Product and Process Design (IPPD) tool for the design and manufacture of microwave transmit/receive modules. The tool, which was developed as part of a contract with Northrop Grumman, was designed to combine high performance, ease of understandability by manufacturing personnel, ease of maintenance, and integration with other systems. It uses AI planning to generate process-plan elements, IP tradeoff analysis to select Pareto optimal combinations of design elements and plan elements, and a GUI for user control of the system{\textquoteright}s operation.},
	address = {Austin, Texas},
	booktitle = {2000 AAAI Workshop on Integration of AI and OR Techniques for Combinatorial Optimization}
}
@conference {
	title = {Adaptive Classification Based on Compressed Data Using Learning Vector Quantization},
	author = {Baras, John S., Dey, Subhrakanti.},
	year = {1999},
	month = {12/1999},
	abstract = {Classification problems using compressed data are becoming increasingly important in many applications with large amounts of sensory data and large sets of classes. These applications range from Aided Target~Recognition (ATR), to medical diagnosis, to speech recognition, to fault detection and identification in manufacturing systems. In this paper, we develop and analyze a learning vector quantization (LVQ) based algorithm for the combined compression and classification problem. We show convergence of the algorithm using techniques from stochastic approximation, namely, the ODE method.},
	address = {Phoenix, Arizona},
	booktitle = {38th IEEE Conference on Decision and Control},
	pages = {pp. 3677-3683}
}
@conference {
	title = {At the Gates of the Millenium: Are we in Control?},
	author = {Baras, John S.},
	year = {1999},
	month = {12/1999},
	address = {Phoenix, Arizona},
	booktitle = {38th IEEE Conference on Decision and Control},
	pages = {pp. 1721-1724}
}
@conference {
	title = {At the Gates of the Millennium: Are We in Control?},
	author = {Baras, John S., Doyle, John C., Y-C. Ho, Johnson, Timothy L.},
	year = {1999},
	month = {12/1999},
	address = {Phoenix, Arizona},
	booktitle = {38th IEEE Conference on Decision and Control},
	pages = {pp. 1721-1724}
}
@conference {
	title = {Data-Aided ML Parameter Estimators of PSK Burst Modems and their Systolic VLSI Implementations},
	author = {Jiang, Yimin., Verahrami, Farhad., Ting, Wen-Chun., Richmond, Robert L., Baras, John S.},
	year = {1999},
	month = {12/1999},
	abstract = {A high-performance Universal Modem ASIC that supports several modulation~types and burst mode frame formats is under development. Powerful and generic data-aided (DA) parameter estimators are necessary to accommodate many modes. In this paper, we present an approximated maximum likelihood (ML) carrier frequency offset estimator and their systolic VLSI implementations for PSK burst modems. The performances are close to the Cramer-Rao lower bounds (CRLB) as low SNRs. Compared with theoretical solutions the estimators proposed here are much simpler and easier to implement by the current VLSI technology. The CRLB for DA estimations is discussed in some depth, some issues on training sequence design are also addressed in the work.~},
	address = {Rio de Janeiro, Brazil},
	booktitle = {1999 IEEE Global Telecommunications Conference (GLOBECOM)},
	pages = {pp. 2177-2182}
}
@conference {
	title = {The Window Distribution of Multiple TCPs with Random Loss Queues},
	author = {Misra, Archan., Ott, Teunis., Baras, John S.},
	year = {1999},
	month = {12/1999},
	abstract = {Two approximate techniques for analyzing the window size distribution of TCP flows sharing an RED-like bottleneck queue are presented. Both methods presented first to use a fixed point algorithm to obtain the mean window sizes of the flows, and the mean queue length in the bottleneck buffer. The simpler of the two methods then uses the {\textquoteleft}square root formula{\textquoteright} for TCP; the other method is more complicated. More often than not, the simpler method is slightly more accurate; this is probably due to the fact that window sizes of the different flows are negatively correlated.},
	address = {Rio de Janeiro, Brazil},
	booktitle = {1999 IEEE Global Telecommunications Conference (GLOBECOM)},
	pages = {pp.  1714-1726}
}
@conference {
	title = {Object-Relational Databases and Telecommunication Network Management},
	author = {Baras, John S.},
	year = {1999},
	month = {11/1999},
	address = {Link{\"o}ping, Sweden},
	booktitle = {Annual Review Workshop, ISIS Competence Center},
	organization = {Link{\"o}ping University}
}
@conference {
	title = {Classification and Control from Compressed Data},
	author = {Baras, John S.},
	year = {1999},
	month = {11/1999},
	address = {London, UK},
	organization = {Imperial College}
}
@conference {
	title = {VLSI Implemented Data-Aided ML Parameter Estimators of PSK Burst Modems},
	author = {Jiang, Yimin., Ting, Wen-Chun., Verahrami, Farhad., Richmond, Robert L., Baras, John S.},
	year = {1999},
	month = {09/1999},
	abstract = {A high-performance universal modem ASIC that supports several modulation types and burst mode frame formats are under development. The ASIC is designed to work under stringent conditions such as large carrier frequency offset (up to 13\% symbol rate) and low signal-to-noise ratio (SNR). Powerful and generic data-aided parameter estimators are necessary to accommodate many modes. In this paper, we present an approximated maximum likelihood (ML) carrier frequency offset estimator, ML joint carrier phase, and timing offsets estimator and their systolic VLSI implementations for PSK burst modems. The performances are close to the Cramer-Rao lower bounds at low SNRs. Compared with theoretical solutions the estimators proposed here are much simpler and easier to implement by the current VLSI technology.},
	address = {Amsterdam, Netherlands},
	booktitle = {1999 Vehicular Technology Conference},
	pages = {pp.733-738}
}
@conference {
	title = {Caching and Multicasting in DBS systems},
	author = {Liu, Mingyan., Karir, Manish., Baras, John S.},
	year = {1999},
	month = {09/1999},
	abstract = {The use of caching and multicasting has been studied extensively in the context of terrestrial networks. However, the use of these technologies in a Direct Broadcast Satellite (DBS) system remains unclear. In this paper, we discuss possible choices of caching and multicasting schemes, motivated by current applications in the terrestrial Internet, that could be considered for a DBS system. We examine their advantages and disadvantages as well as the tradeoffs involved in combinations of different approaches. We also propose some uses of these technologies and describe an architecture that enhances the performance and efficiency of a DBS system.},
	address = {Aizu, Japan},
	booktitle = {1999 International Workshop on Group Communications},
	pages = {pp. 56-61}
}
@conference {
	title = {VLSI implemented ML joint carrier phase and timing offsets estimator for QPSK/OQPSK burst modems},
	author = {Jiang, Yimin., Verahrami, Farhad., Ting, Wen-Chun., Richmond, Robert L., Baras, John S.},
	year = {1999},
	month = {09/1999},
	abstract = {A high-performance ASIC supporting multiple modulation, error correction, and frame formats is under development at Hughes Network Systems, Inc. Powerful and generic data-aided (DA) estimators are needed to accommodate operation in the required modes. A simplified DA maximum likelihood (ML) joint estimator for carrier phase and symbol timing offset for QPSK/OQPSK burst modems and a sample systolic VLSI implementation for the estimator are presented. Furthermore, the Cramer-Rao lower bound (CRLB) for DA case is investigated. The performance of the estimator is shown through simulation to meet the CRLB even at low signal-to-noise ratios (SNR). Compared with theoretical solutions, the proposed estimator is less computationally intensive and is, therefore, easier to implement using current VLSI technology},
	address = {New Orleans, Louisiana},
	booktitle = {Proceedings of Wireless Communications and Networking Conference},
	pages = {pp. 742-746}
}
@conference {
	title = {A Video Transmission System Based on Human Visual Model},
	author = {Jiang, Yimin., Gu, Junfeng., Baras, John S.},
	year = {1999},
	month = {09/1999},
	abstract = {This paper presents a joint source-channel coding scheme of digital video broadcasting over satellite channel. The video compression is based on human visual model. Perceptual distortion model the just-noticeable-distortion (JND) is applied to improve the subjective quality of compressed videos. 3-D wavelet decomposition can remove spatial and temporal redundancy and provide scalability of video quality. In order to conceal the errors occurred under bad channel conditions, a novel slicing method and a joint source channel coding scenario that combines RCPC with CRC and utilizes the distortion information to allocate convolutional coding rates are presented. A new performance index based on JND is proposed and used to evaluate the overall performance at different signal-to-noise ratios(SNR). Our system uses OQPSK modulation scheme.},
	address = {Amsterdam, Netherlands},
	booktitle = {IEEE VTC 1999},
	pages = {pp. 868-873}
}
@conference {
	title = {A Simulation Study of Enhanced TCP/IP Gateways for Broadband Internet over satellite},
	author = {Karir, Manish., Liu, Mingyan., Barrett, Bradley A., Baras, John S.},
	year = {1999},
	month = {08/1999},
	abstract = {The demand for Internet bandwidth has been growing rapidly over the years and the use of high bandwidth satellites has been proposed as one possible solution to meet the increasing demand. However, there are certain performance problems with providing Internet over satellite due to the nature of TCP/IP protocol suite and the satellite link characteristics. In this paper we describe a simulation study of architecture for improving the performance of TCP/IP over satellite links. On each end of satellite link, there are gateways that split the TCP ~connection so that the satellite link is transparent to the end hosts. The split TCP connection over the satellite segment is then optimized. TCP connection control is maintained on each segment of the split connection. We simulated such an architecture in OPNET and present results showing improved throughput over the satellite link.~},
	address = {Washington DC},
	booktitle = {OPNETWORK \&rsquo;99},
	pages = {pp. 1-6}
}
@conference {
	title = {Hybrid Internet Simulation Testbed},
	author = {Liu, Mingyan., Karir, Manish., Raissi-Dekhordi, Majid., Baras, John S.},
	year = {1999},
	month = {08/1999},
	abstract = {Internet technology as a widely accepted modern telecommunication standard has been widely extended to combine with numerous other technologies, e.g..,satellite, ATM, wireless. This is what we term as Hybrid Internet. Along with this technology emerging, various enhancements and alterations of standard TCP/IP for different purposes have been proposed and studied in-tensively. More and more frequently we are facing the question of how to choose from these different schemes to design a system for a particular purpose, which would inevitably involve the interaction and trade-of study. We believe that simulation is a powerful tool for this type of work. In this paper, we describe our implementation of a Hybrid Internet testbed which includes a series of traffic models and TCP/IP enhancements. The goal of our work is to make a set of reusable modules upon which we can build complex systems to study the standard protocols and their variations. We also present application examples using these module components.},
	address = {Washington DC},
	booktitle = {Proceedings of the 1999 OPNET Annual Technology Conference (OPNETWORK)},
	pages = {pp. 1-6}
}
@conference {
	title = {An Information Theoretic Analysis of Rooted Tree Based Multicast Key Distribution Schemes},
	author = {Poovendran, Radha., Baras, John S.},
	year = {1999},
	month = {08/1999},
	abstract = {Several variations of rooted tree based solutions have been recently proposed for member revocation in multicast communications [18 ,19,20,21] .In this paper we show that by assigning Probabilities for member revocations,the optimality correctness and the system requirements of some these schemes [18,19,20,21 ] can be systematically studied using information theoretic concepts. Specifically, we show that the optimal average number of keys per member in a rooted tree is related to the entropy of the member revocation event. Using our derivation we show that (a) the key assignments in [18, 21, 20, 19] corresponds to the maximum entropy solution, (b) and direct application of source coding will lead to member collusion (we present recently proposed solutions [21, 20] as examples of this) and a general criteria that admits member collusion. We also show the relationship between entropy of member revocation event and key length.},
	address = {Santa Barbara, CA},
	booktitle = {Crypto\&rsquo;99: 19th Annual IACR Crypto Conference},
	pages = {pp.624-638}
}
@conference {
	title = {An Information Theoretic approach to Secure Multicast Key Management},
	author = {Poovendran, Radha., Baras, John S.},
	year = {1999},
	month = {06/1999},
	abstract = {New results are presented for recently proposed rooted tree based secure multicast key revocation scheme [1,2] by studying the information theoretic properties of member revocation events .It is shown that the optimal average number of keys per person is given by the entropy of the member revocation event and the currently available solution correspond to the worst case or the maximum entropy scenario. It is shown that the proposed key assignment in [2] corresponds to optimal source coding and is susceptible to attack by compromise or collusion of multiple members.},
	address = {Metsovo, Greece},
	booktitle = {1999 IEEE International Symposium on Information Theory},
	pages = {pp.36}
}
@conference {
	title = {A Private Scheme for distributed ,Shared Secret Generation},
	author = {Poovendran, Radha., Corson, Scott M., Baras, John S.},
	year = {1999},
	month = {06/1999},
	abstract = {We present a scheme for shared secret generations by n members that combines the contributions the members in a fashion such that the individual contribution of each member is not exposed to anyone- including other members. We note that for an external attacker trying to break the n L-bit secrets of the members, the effective search space dimension is~nL, meaning that all n keys must be broken simultaneously in order to crack system integrity. We also note that the scheme provides "Unconditional Secrecy"[1].},
	address = {Kruger National Park, South Africa},
	booktitle = {1999 IEEE Information Theory and Communications Workshop},
	pages = {pp.8}
}
@conference {
	title = {Optimal Scaleable Security Architectures in the presence of Colluding Mobile Traitors},
	author = {Poovendran, Radha., Baras, John S.},
	year = {1999},
	month = {04/1999},
	abstract = {We present the issues related to secure multicast communication,in the presence of members who may collaborate to compromise the integrity of the system{\textquoteright}s security. We also show that the ability to compartmentalize the system compromise depends on the availability of trusted intermediate nodes.We also note that some variations of the recently proposed tree based schemes don{\textquoteright}t provide the required level of security and may be compromised if two appropriate members are compromised. We present the analysis of the weakness of these schemes here. We further note that the currently available tree based key distribution schemes are not optimal, and choose the worst case solution for key assignment. We note that the claims, including the collusion, can be formally proved using basic concepts from source coding theory and entropy as in [4].},
	address = {Richardson, Texas},
	booktitle = {1999 Emerging Technologies Symposium on Wireless Communications and Wireless systems},
	pages = {pp.1-5}
}
@conference {
	title = {A Carrier Frequency Estimation Method of MPSK Signals and its Systolic VLSI Implementation},
	author = {Y. Jiang, Ting, Wen-Chun., Verahrami, Farhad., Richmond, Robert L., Baras, John S., Hughes Network Systems, Inc.},
	year = {1999},
	month = {03/1999},
	abstract = {In this paper we present an autocorrelation-based method for estimating the carrier frequency offset of an MPSK signal with random data modulation. Although autocorrelation based techniques imply heavy usage of hardware resourses this technique is scalable and lends itself to systolic VLSI implementations. The performance of the open-loop estimator presented is close to Cramer-Rao lower bound (CRLB) for the frequency estimation from a block of random MPSK symbols at low signal-to-noise ratios (SNR). The estimator can be used in frequency acquisition of burst and continuous modems operating under low SNR and large frequency offset conditions.},
	address = {Baltimore, MD},
	booktitle = {CISS\&rsquo;99 : 33rd Annual Conference on Information Sciences and Systems},
	pages = {pp.142-146},
	organization = {John Hopkins University}
}
@conference {
	title = {Delay Monitoring in ATM networks},
	author = {Arora, Anubhav., Baras, John S., Mykoniatis, George.},
	year = {1999},
	month = {02/1999},
	abstract = {ATM Network provide end-to-end QoS guarntees to connections for their lifetime,in the form of bounds on delays,errors and losses. Performance Management invloves measurement of these parameters accurately and taking control measures if required,to improve performance.This is very important for real time connections in which losses are irrecoverable and delays cause interruptions in service. In this paper, we concentrate on delay monitoring mechanisms. After presenting the OAM standards for ATM and a few sloutions in the literature, problems still remaining are formulated and directions being pursued to obtain solutions are indicated.},
	address = {College Park, MD},
	booktitle = {3rd Annual Conference on Advanced Telecommunications and Information Distribution Research Program(ATIRP)},
	pages = {pp. 259-263},
	organization = {University of Maryland}
}
@conference {
	title = {Dynamic Elgamal Public Key Generation with Tight Binding},
	author = {Poovendran, Radha., Corson, Scott M., Baras, John S.},
	year = {1999},
	month = {02/1999},
	abstract = {We present a new distributed ,group ElGamal public key generation algorithm which also permits maintenance of a group specific, dynamic,individual ElGamal public key infrastructure. We parameterize the group with a time varying quantity that serves as a distributed mechansim for controlling key generation privilege. Our scheme can be viewed as an alternative to polynomial schemes where, at the time of secret construction step,there has to be a thrid party or black box to combine the shares. Also, in polynomial schemes, at the time of combining, the individual shares of the secret have to be revealed the third party. In our scheme, the common secret can be generated without ever exposing the individual shares constructing it. We note that many of the ~proposed distributed key management [2-4] schemes need such group keys for certification and signing process.},
	booktitle = {3rd Annual Conference on Advanced Telecommunications and Information Distribution Research Program(ATIRP)},
	pages = {pp. 471-475}
}
@conference {
	title = {An Automated, Distributed, Intelligent Fault Management System for Communication Networks},
	author = {Li, Hongjun., Baras, John S., Mykoniatis, George.},
	year = {1999},
	month = {02/1999},
	abstract = {In this paper we present a Distributed Intelligent Fault Management (DIFM) system for communication networks. The overall architecture of the proposed system is based on a distributed cooperative multi-agent paradigm, with probabilistic networks as the framework for knowledge representation and evidence inferencing. We adopt the management by delegation paradigm [5] for network monitoring and integrate both hard and soft faults.},
	address = {College Park, MD},
	booktitle = {3rd Annual Conference on Advanced Telecommunications and Information Distribution Research Program(ATIRP)},
	pages = {pp. 253-257},
	organization = {University of Maryland}
}
@conference {
	title = {Modeling and Simulation of Large Hybrid Networks},
	author = {Liu, Mingyan., Baras, John S., Payne, Stephen Marshall., Harrelson, Hal.},
	year = {1999},
	month = {02/1999},
	abstract = {This paper describes a modeling and simulation framework for large Hybrid networks that includes satellites framework for large hybrid networks that include satellites, terrestrial wireless and mobile and ad hoc networks. The purpose of simulation framework is to parallel the actual implementation of a testbed network currently being constructed at ARL. The modelling framework uses the performance measures generated by simulation to analytically study larger scaled versions of the testbed networks. The combination of two methodologies allows the feasibility of the testbed architecture{\textquoteright}s widespread implementation to be studied without the associated costs of performing such experiments with actual equipment. Additionally, technological tradeoffs and interoperability issues can be studied so that informed decisions can be made about the implementation of future military communication networks.

~

~

~

,terrestrial wireless and mobile Ad Hoc networks.The purpose of simulation framework is to parallel the actual implementation of the test bed network currently being constructed at ARL.},
	address = {College Park, Maryland},
	booktitle = {3rd Annual Conference on Advanced Telecommunications and Information Distribution Research Program(ATIRP)},
	pages = {pp. 201-206},
	organization = {University of Maryland}
}
@conference {
	title = {Broadband Internet and Satellite Technologies},
	author = {Baras, John S.},
	year = {1999},
	month = {01/1999},
	address = {Dallas, Texas},
	booktitle = {Sixth Annual Mobile Communications Conference and Exhibition}
}
@conference {
	title = {Finite-Dimensional Methods for Computing the Information State in Nonlinear Robust Control},
	author = {Baras, John S., Darling, RWR.},
	year = {1998},
	month = {12/1998},
	abstract = {In nonlinear output robust control and in nonlinear risk sensitive partially observed stochastic control, the optimal control is a memoryless function of the information state. The information state dynamics are directly influenced by the control performance metric, thus displaying a direct linkage between control objectives and sufficient statistics for control. It has been observed in several examples that by modifying the control performance metric one can render the dynamics of the information state finite dimensional. In linear robust control, it is well known that the information state can be computed by a simple finite-dimensional formula. Using the Lie theory for transformations of this basic solution, we show how the information state for certain nonlinear control problems can also be obtained using finite-dimensional calculations, e.g.. via the solution of systems of ODEs. This is explained using fundamental results on the invariance groups of the equations involved. An intuitive interpretation of the significance of the result is also provided.},
	address = {Tampa, Florida},
	booktitle = {37th IEEE Conference on Decision and Control}
}
@conference {
	title = {University-Industry Collaboration},
	author = {Baras, John S.},
	year = {1998},
	month = {12/1998},
	address = {Washington DC},
	booktitle = {Workshop on Enhancing Academic Research Contributions to the Aerospace Industry},
	organization = {National Academy of Engineering }
}
@conference {
	title = {Information Based Complex Systems Design},
	author = {Baras, John S.},
	year = {1998},
	month = {11/1998},
	address = {Link{\"o}ping, Sweden},
	booktitle = {Annual Review Workshop, ISIS Competence Center},
	organization = {Link{\"o}ping University}
}
@conference {
	title = {A Distributed Shared Key Generation Procedure Using Fractional Keys},
	author = {Poovendran, Radha., Corson, Scott M., Baras, John S.},
	year = {1998},
	month = {10/1998},
	abstract = {We present a new class of distributed key generation and recovery algorithms suitable for group communication systems where the group membership is either static or slowly time-varying, and must be tightly controlled. The proposed key generation approach allows entities which may have only partial trust in each other to jointly generate a shared key without the aid of an external third party. The group collectively generates and maintains a dynamic group parameter, and the shared key is generated using a pseudo random function using this parameter as a seed. The validity of key generation can be checked using veriable secret sharing techniques. The key retrieval method does not require the keys to be stored in an external retrieval center. We note that many Internet-based applications may have these requirements. Fulllment of these requirements is realized through the use of fractional keys-a distributed technique recently developed to enhance the security of distributed systems in a non-cryptographic manner.},
	address = {Bedford, MA},
	booktitle = {MILCOM\&rsquo;98},
	pages = {pp. 1-6}
}
@conference {
	title = {Group Invariance and Symmetries in Control Systems and Mathematical Physics},
	author = {Baras, John S.},
	year = {1998},
	month = {10/1998},
	address = {Cambridge, Massachusetts},
	booktitle = {Perspectives in Control, honoring Professor Roger W. Brockett on his 60th birthday}
}
@conference {
	title = {Systems and Control Education as Foundation of Systems Engineering Education},
	author = {Baras, John S.},
	year = {1998},
	month = {10/1998},
	address = {Champaign, IL},
	booktitle = {NSF Workshop on New Directions in Control Engineering Educatio},
	organization = {University of Illinois at Urbana-Champaign}
}
@conference {
	title = {Web-it-Man: A Web-based Integrated Tool for Manufacturing Environment},
	author = {Karne, Ramesh K., Baras, John S., Nau, Dana S., Ball, Michael O., Lin, Edward., Trichur, Vinai., Dandekar, Swati V., Poluri, Sridhar., Williams, James T.},
	year = {1998},
	month = {09/1998},
	abstract = {Exponential growth in Internet applications and a need for a global access for future manufacturing demands web-based tools that operate seamlessly in heterogeneous environments. We present a Web-based Integrated Tool for Manufacturing that assists designers with a variety of CAD/CAM tools through a unified user interface. Web enabled system architecture is proposed for the future development of manufacturing tools. Design issues and research topics pertinent to this architecture are described. A prototype implementation based on this architecture and its current status is outlined. Finally, our research efforts in the development of this tool and some future research areas are identified.},
	address = {Atlanta, GA},
	booktitle = {1998 ASME Design Technical Conferences, ASME Computers in Engineering Conference},
	pages = {pp. 1-12}
}
@conference {
	title = {Process Planning in Microwave Module Production},
	author = {Meyer, Jeff., Ball, Mike., Baras, John S., Chowdhury, Abdur., Lin, Edward., Nau, Dana S., Rajamani, Ravi., Trichur, Vinai.},
	year = {1998},
	month = {08/1998},
	abstract = {This paper describes the development of a process planning module for an integrated production and process design (IPPD) tool which automates the design and manufacture of microwaves modules. Specifically, this paper presents a process template that is used to interface with multiobjective optimization techniques to create a planner that can consider alternative designs based on process yields, cost, and manufacturing and purchasing lead tiems. The integrations of the planner and the tradeoff optimization modules provides the designer immediate feedback on cost and productivity through generation and evaluation of alternative designs early in the design state.},
	address = {Albuquerque, New Mexico},
	booktitle = {SIGMAN: Artificial Intelligence and Manufacturing: State of the Art and State of Practice},
	pages = {pp. 120-126}
}
@conference {
	title = {Flow Control and Dynamic Service Allocation in DBS-Based Internet},
	author = {Baras, John S., Olariu, Gabriel L. },
	year = {1998},
	month = {06/1998},
	abstract = {This paper describes the development of a process planning module for an integrated product and process design (IPPD) tool which automates the design and manufacture of microwave modules. Specifically, this paper presents a process template that is used to interface with multi-objective optimization techniques to create a planner that can consider alternative designs based in process yields, cost, and manufacturing and purchasing lead times. The integration of the planner and the tradeoff optimization modules provides the designer immediate feedback on cost and productivity through generation and evaluation of alternative designs early in the design stage.},
	address = {Cleveland, Ohio},
	booktitle = {Satellite Networks: Architectures, Applications and Technologies Workshop},
	pages = {pp. 489-498},
	organization = {NASA Lewis Research Center}
}
@conference {
	title = {Scalable Coding of Video Objects},
	author = {Haridasan, Radhakrishnan., Baras, John S.},
	year = {1998},
	month = {05/1998},
	abstract = {This paper provides a methodology to encode video objects in a scalable manner with regard to both content and quality. Content scalability and quality scalability have been identified as required features in order to support video coding across different environments. Following the object-based approach to coding video, we extend our previous work on motion-based segmentation by using a time recursive approach to segmenting image sequences and decomposing a video "shot" into its constituent objects. Our formulation of the segmentation problem enables us to design a codec in which the information (shape, texture and motion) pertaining to each video object is encoded independently of the other. The multiresolution wavelet decomposition used in encoding texture information is shown to be helpful in providing spatial scalability. Our codec design is also shown to be temporally scalable.},
	address = {Monterey, CA},
	booktitle = {IEEE International Symposium on Circuits and Systems 1998 (ISCAS\&rsquo;98)},
	pages = {pp. 289-292}
}
@conference {
	title = {Hybrid Communication Networks: Modeling, Performance Evaluation and Broadband Data Services},
	author = {Baras, John S.},
	year = {1998},
	month = {04/1998},
	booktitle = {ARL Federated Lab Distinguished Lecture},
	organization = {ARL}
}
@conference {
	title = {Hybrid Communication Networks: The Last Mile and Efficient Broadband Service Provision},
	author = {Baras, John S.},
	year = {1998},
	month = {04/1998},
	address = {Boston, Massachusetts},
	booktitle = {AA/EECS Departments seminar on Innovative Directions in Communications},
	organization = {MIT}
}
@conference {
	title = {Wavelet-Based Hierarchical Organization of Large Image Databases:~ ISAR and Face Recognition},
	author = {Baras, John S., Wolk, Sheldon I.},
	year = {1998},
	month = {04/1998},
	abstract = {We present a method for constructing efficient hierarchical organization of image databases for fast recognition and classification. The method combines a wavelet preprocessor with a Tree-Structured-Vector-Quantization for clustering. We show results of application of the method to ISAR data from ships and to face recognition based on photograph databases. In the ISAR case we show how the method constructs a multi-resolution aspect graph for each target.},
	address = {Orlando, Florida},
	booktitle = {SPIE 12th International Symposium on Aerospace, Defense Sensing, Simulation and Control},
	pages = {pp. 546-558}
}
@conference {
	title = {Integrated Product and Process Design for Electromechanical Products},
	author = {Baras, John S.},
	year = {1998},
	month = {04/1998},
	address = {Boston, Massachusetts},
	booktitle = {Lean Manufacturing Program},
	organization = {MIT}
}
@conference {
	title = {Fast Internet Services via Direct Broadcast Satellites},
	author = {Baras, John S., Kenyon, J.},
	year = {1998},
	month = {03/1998},
	address = {College Park, MD},
	booktitle = {Three-Presidents Summit, A Industry-University collaboration},
	organization = {University of Maryland}
}
@conference {
	title = {Progressive Classification: Universal Algorithms and Applications},
	author = {Baras, John S.},
	year = {1998},
	month = {03/1998},
	address = {Boston, Massachusetts},
	booktitle = {Laboratory for Information and Decision Systems Colloquium},
	organization = {MIT}
}
@conference {
	title = {High Performance IP Multicasting Over Wireless Satellite-Terrestrial Networks},
	author = {Baras, John S., Secka, Isatou.},
	year = {1998},
	month = {02/1998},
	abstract = {We describe our work on IP multicast extensions to the wireless hybrid network described. We describe effective extensions of IGMP, and asymmetric multicast algorithms that exploit the asymmetry to increase the number of users, scale-up and improve the loading of the terrestrial components. This requires an asymmetric multicast routing mechanism. We describe enhancements to existing multicast routing protocols such as CBT to the hybrid environment described here. We provide results on performance of our proposed hybrid multicast algorithms with respect to the following performance metrics: time to join a group; time for a packet to reach every member of the multicast group; performance with large multicast groups.},
	booktitle = {17th AIAA International Communications Satellite Systems Conference and Exhibit}
}
@conference {
	title = {Linking Satellites and Terrestrial Networks for Digital Connectivity},
	author = {Baras, John S.},
	year = {1998},
	month = {02/1998},
	address = {Boston, Massachusetts},
	booktitle = {EECS Department Colloquium},
	organization = {MIT}
}
@conference {
	title = {Performance Evaluation in Multi-Rate, Multi-Hop Communication Networks with Adaptive Routing},
	author = {Liu, Mingyan., Baras, John S., Misra, Archan.},
	year = {1998},
	month = {02/1998},
	abstract = {Accurate performance evaluation has always been an important issue in network design and analysis. Discrete event simulation has been known to be accurate but very time consuming. Thus analytical methods/approximation is necessary for real time estimation, large scale network optimization and sensitivity analysis. In a circuit-switched loss network, a~particular performance metric of interest is the end-to-end blocking probability. Various analytical approaches and approximation schemes have been suggested for this problem and among them, the fixed-point method, or reduced load method, has ~received~much attention. However, most of these schemes either consider only single traffic rate situations or multi-rate traffic under fixed routing. We develop an approximation scheme to estimate end-to-end blocking probability in a multi-rate multi-hop network with an adaptive routing scheme. The approximation results are compared with that of discrete event simulation. An example of application is also provided in which the proposed scheme is linked to the optimization tool CONSOL-OPTCAD to get network design trade-offs. The method described here is readily applicable to accurate performance evaluation of military networks which are often large and hybrid.},
	address = {College Park, Maryland},
	booktitle = {ARL Federated Laboratory 2nd Annual Conference},
	pages = {pp. 136-140},
	organization = {University of Maryland}
}
@conference {
	title = {A Scalable Extension of Group Key Management Protocol},
	author = {Poovendran, Radha., Ahmed, S., Corson, Scott M., Baras, John S.},
	year = {1998},
	month = {02/1998},
	abstract = {This paper presents a robust, scalable extension to the recently proposed multicast Group Key Management Protocol (GKMP) ([1], [2]), in terms of security administration. The GKMP has two major security related problems: (a) lack of any mechanism to remove a compromised group administrator, and (b) lack of scalability. We are able to remove a compromised single panel member from generating the group keys by setting the panel members with shared authority to generate the group keys. We then introduce the sub-controllers who have all the functionalities of the group control panel except the authority to generate the group keys. The sub-control panel helps scalability of the network in terms of the security operations. The sub-controllers are chosen using a threshold-based clustering algorithm.},
	address = {College Park, Maryland},
	booktitle = {ARL Federated Laboratory 2nd Annual Conference},
	pages = {pp. 187-191},
	organization = {University of Maryland}
}
@conference {
	title = {Accurate Segmentation and Estimation of Parametric Motion Fields for Object-Based Video Coding Using Mean Field Theory},
	author = {Haridasan, Radhakrishnan., Baras, John S.},
	year = {1998},
	month = {01/1998},
	abstract = {We formulate the problem of decomposing a scene into its constituent objects as one of partitioning the current frame into objects comprising it. The motion parameter is modeled as a nonrandom but unknown quantity and the problem is posed as one of Maximum Likelihood (ML) estimation. The MRF potentials which characterize the underlying segmentation field are defined in a way that the spatio-temporal segmentation is constrained by the static image segmentation of the current frame. To compute the motion parameter vector and the segmentation simultaneously we use the Expectation Maximization (EM) algorithm. The E-step of the EM algorithm, which computes the conditional expectation of the segmentation field, now reflects interdependencies more accurately because of neighborhood interactions. We take recourse to Mean Field theory to compute the expected value of the conditional MRF. Robust M-estimation methods are used in the M- step. To allow for motions of large magnitudes image frames at various scales and the EM procedure is embedded in a hierarchical coarse-to-fine framework. Our formulation results in a highly parallel algorithm that computes robust and accurate segmentations as well as motion vectors for use in low bit rate video coding.},
	address = {San Jose, CA},
	booktitle = {SPIE 10th Annual Symposium on Visual Communications and Image Processing 1998 (VICP \&rsquo;98)},
	pages = {pp. 361-369}
}
@conference {
	title = {Internet Service via Broadband Satellite Networks},
	author = {Butts, Norman P., Bharadwaj, Vijay G., Baras, John S.},
	year = {1998},
	month = {01/1998},
	abstract = {The demand for Internet bandwidth has grown rapidly in the past few years. A new generation of broadband satellite constellations promise to provide high speed Internet connectivity to areas not served by optical fiber, cable, or other high speed terrestrial connections. However, using satellite links to supply high bandwidth has been difficult due to problems with inefficient performance of the Internet{\textquoteright}s TCP/IP protocol suite over satellite. We describe an architecture for improving the performance of TCP/IP protocols over heterogeneous network environments, especially networks containing satellite links. The end-to-end connection is split into segments, and the protocol in the satellite segment is optimized for the satellite link characteristics. TCP congestion control mechanisms are maintained on each segment, with some coupling between the segments to produce the effect of end-to-end TCP flow control. We have implemented this design and present results showing that using such gateways can improve throughput for individual connections by a large factor over paths containing a satellite link.},
	address = {Boston, Massachusetts},
	booktitle = {SPIE Voice, Video and Data Communications Symposium}
}
@conference {
	title = {Combined Estimation and Control of HMMs},
	author = {Frankpitt, Bernard., Baras, John S.},
	year = {1997},
	month = {12/1997},
	abstract = {The principal contribution of this paper is the presentation of the potential theoretical results that are needed for an application of stochastic approximation theory to the problem of demonstrating asymptomatic stability for combined estimation and control of a plant described by a hidden Markov model. We motivate the results by briefly describing a combined estimation and control problem. We show how the problem translates to the stochastic approximation framework. We also show how the Markov chain that underlies the stochastic approximation problem~can be decomposed into factors with discrete and continuous range. Finally, we use this decomposition to develop the results that are needed for an application of the ODE method to the stochastic control problem.},
	address = {San Diego, CA},
	booktitle = {1997 IEEE Conference on Decision and Control},
	pages = {pp. 2254-2259}
}
@conference {
	title = {Integrated Management of Large Satellite-Terrestrial Networks},
	author = {Baras, John S., Ball, Mike., Roussopoulos, Nick., Jang, Kap D., Stathatos, Kostas., Valluri, Jaibharat.},
	year = {1997},
	month = {11/1997},
	abstract = {Hybrid communication networks provide an economically feasible and technologically efficient means to implement the global information infrastructure. The management of such heterogeneous networks is a critical market differentiator for telecommunications companies and a formidable technical task. In this paper we describe our efforts in the Center for Satellite and Hybrid Communications Networks, to design and implement an integrated network management system for such networks. The major accomplishments to date are the design and implement an integrated network management system for such networks. The major accomplishments to date are the design and implementations of an object oriented data model for hybrid networks consisting of satellite networks and terrestrial ATM networks; the extension of the system to hybrid networks with as many as 300,000 nodes; the development of browsing graphical tools so that mesh-connected graph networks (as opposed to tree networks) can be efficiently queried; specifically designed graphical widgets for displaying performance data continuously from the network management information database (MIB); extensions of the GUI to distributed operation including appropriate designs for consistency and concurrency between the GUI display and the network MIB;~storage and organization issues for performance data in the MIB; integration of configuration management and performancce management.},
	address = {Monterey, CA},
	booktitle = {MILCOM \&rsquo;97},
	pages = {383-387}
}
@conference {
	title = {Hierarchical, Layered Modeling and Performance Evaluation of Hybrid Communication Networks},
	author = {Baras, John S., Corson, Scott M., Jang, Kap D., Liu, Mingyan., Misra, Archan., Xie, Hui.},
	year = {1997},
	month = {11/1997},
	abstract = {Commercial and military networks are rapidly becoming hybrid networks;~that is interconnected wireless terrestrial, wireline terrestrial and satellite networks. There is a great need for software tools to design, model and also do performance analysis efficiently for such large heterogeneous networks. This is the topic addressed in this paper. The hybrid network modeling and performance evaluation tool is currently under development at the University of Maryland. The tool consists of an algorithmic structure and a software architecture. The algorithm is hierarchical in form, deriving its structure from that of the network which follows the network{\textquoteright}s routing hierarchy. At each level, a node represents a set of nodes at a lower level. The boundary of a node is characterized by a set of statistical models. The statistics and their parametric representations for the models of the level 1 nodes are obtained from the OPNET simulations which are run offline. The model defines procedures that convey modeling, simulation and performance data up and down the hierarchy of models. We consider the following performance metrics only: end-to-end delay, throughput, blocking probabilities, cell or packet loss rate. We describe algorithms based on loss network approximations and fast progressive solutions of resulting fixed point equations.},
	address = {Monterey, CA},
	booktitle = {MILCOM \&rsquo;97},
	pages = {1-5}
}
@conference {
	title = {Automated Network Fault Management},
	author = {Baras, John S., Ball, Mike., Gupta, Sandeep., Viswanathan, P., Shah, Parthiv.},
	year = {1997},
	month = {11/1997},
	abstract = {Future military communication will have a mixture of backbone terrestrial, sattelite and wireless terrestrial networks. The speeds of these networks vary and they are very heterogeneous. As networks become faster, it is not enough to do reactive fault management. Our approach combines proactive and reactive fault management. Proactive fault management is implemented by dynamic and adaptive routing. Reactive fault management is implented by a combination of a neural network and an expert system. The system has been developed for the X.25 protocol. Several fault scenarios were modeled and included in the study: reduced switch capacity, increased packet gneration rate of a certain application, disabled switch in the X.25 cloud, disabled links. We also modeled occurence of alarms including severity of the problem, location of the event and a threshold. To detect and identify faults we use both numerical data associated with the perfomance objects (attributes) in the MIB as well as SNMP traps (alarms). Simulation experiments have been performed in order to understand the convergence of the algorithms, the training of the neural networks involved and the G2/NeurOn-Line software environment and MIB design.},
	address = {Monterey, CA},
	booktitle = {MILCOM \&rsquo;97},
	pages = {pp. 1244- 1250}
}
@conference {
	title = {Fast Asymmetric Internet Over Wireless Satellite-Terrestrial Networks},
	author = {Baras, John S., Corson, Scott M., Papademetriou, Spyro., Secka, Isatou., Suphasindhu, Narin.},
	year = {1997},
	month = {11/1997},
	abstract = {We describe our recent work on the design and implementation of high perfomrnace Internet services over networks consisting of interconnected Direct Broadcast (Satellite) hosts and terrestrial wireless LANs with various capabilities. The network uses receive only satellite links for downstream data delivery and wireless and wireline terrestrial links for the upstream path. A key concept in our work is that of a hybrid terminal which is a PC connected to a DBS antenna and to the local wireless LAN. The hybrid terminal uses a modem connection for outgoing traffic while receiving incoming information through the VSAT.},
	address = {Monterey, CA},
	booktitle = {MILCOM \&rsquo;97},
	pages = {372-377}
}
@conference {
	title = {Extensions of DBS and Hybrid Internet},
	author = {Karir, Manish., Bharadwaj, Vijay G., Holleman, Keith., Suphasindhu, Narin., Papademetriou, Spyro., Baras, John S.},
	year = {1997},
	month = {10/1997},
	abstract = {We describe some experiments which extend the DBS system, in particular, the DirecPC(TM) and DirecTV(TM) DBS, by using the PC with the satellite receiver as a gateway to connect networks together. We also discuss simple methods of receiving multimedia traffic from the multicast backbone (MBONE) [Cas94] over the satellite link, and distributing it, through this gateway, to end users.},
	address = {Budapest, Hungary},
	booktitle = {2nd ACM International Workshop on Satellite-Based Information Services (WOSBIS)},
	pages = {pp. 67-74}
}
@conference {
	title = {Infinite Dimensional Systems, Hardy Function Algebras, the Corona Theorem and Complexity},
	author = {Baras, John S.},
	year = {1997},
	month = {09/1997},
	address = {Kaiserslautern, Germany},
	booktitle = {Operators, Systems and Linear Algebra:  Three Decades of Algebraic Systems Theory, honoring Professor Paul A. Fuhrmann on his 60th birthday}
}
@conference {
	title = {Integrated Product and Process Design Environment Tool for Manufacturing T/R Modules},
	author = {Karne, Ramesh K., Baras, John S., Ball, Michael O., Bashyam, Sridhar., Kebede, Abraham., Williams, James T., Trichur, Vinai., Karir, Manish., Lai, Hsing-Tsu., Dandekar, Swati V.},
	year = {1997},
	month = {09/1997},
	abstract = {We present a decision making assistant tool for integrated product and process design environment for manufacturing applications. Specifically, we target microwave modules which use electro-mechanical components and require optimal solutions to reduce cost, improve quality, and gain leverage in time to market the product. This tool will assist the product and process designer to improve their productivity and also enable to cooperate and coordinate their designs through a common design interface. We consider a multiobjective optimization model that determines components and processes for a given conceptual designs for microwave modules. This model outputs a set of solutions that are Pareto optimal with respect to cost, quality, and other metrics. In addition, we identify system integrations issues for manufacturing applications, and propose and architecture which will serve as a building block to our continuing research in virtual manufacturing applications.},
	address = {Los Angeles, California},
	booktitle = {6th IEEE International Conference on Emerging Technologies and Factory Automation},
	pages = {pp. 1-27},
	organization = {UCLA}
}
@conference {
	title = {Adaptive Data Broadcast in Hybrid Networks},
	author = {Stathatos, Kostas., Roussopoulos, Nick., Baras, John S.},
	year = {1997},
	month = {08/1997},
	abstract = {With the immense popularity of the Web, the world is witnessing an unprecedented demand for data services. At the same time, the Internet is evolving towards an information super-highway that incorporates a wide mixture of existing and emerging communication technologies, including wireless, mobile, and hybrid networking. Taking advantage of these new technologies, we are proposing a hybrid scheme which effectively combines broadcast for massive data dissemination and unicast for individual data delivery. In this paper, we describe a technique that uses the broadcast medium for storage of frequently requested data~and an algorithm that continuously adapts the broadcast content to match the hot-spot of the database. We show that the hot-spot can be accurately obtained by the monitoring the "broadcast misses" observed through direct requests. This is a departure from other broadcast-based systems which rely on efficient scheduling based on precompiled user profiles. We also show that the proposed scheme performs effectively even under very dynamic and rapidly changing workloads. Extensive simulation results demonstrate both the scalability and versatility of the technique.},
	address = {Athens, Greece},
	booktitle = {Twenty\&ndash;third International Conference on Very Large Databases},
	pages = {pp. 326-335}
}
@conference {
	title = {Integrated Product and Process Design Environment Tool for Manufacturing T/R Modules},
	author = {Karne, Ramesh K., Baras, John S., Ball, Mike., Bashyam, Sridhar., Kebede, Abraham., Williams, James T., Trichur, Vinai., Karir, Manish., Lai, Hsing-Tsu., Dandekar, Swati V.},
	year = {1997},
	month = {08/1997},
	abstract = {We present a decision making assistant tool for integrated product and process design environment for manufacturing applications. Specifically, we target microwave modules which use Electro-mechanical components and require optimal solutions to reduce cost, improve quality, and gain leverage in time to market the product. This tool will assist the product and process designer to improve their productivity and also enable to cooperate and coordinate their designs through a common design interface. We consider a multiobjective optimization model that determines components and processes for a given conceptual designs for microwave modules. This model outputs a set of solutions that are Pareto optimal with respect to cost, quality, and other metrics. In addition, we identify system integration issues for manufacturing applications~and propose an architecture which will serve as a building block to our continuing research in virtual manufacturing applications.},
	address = {Montreal, Canada},
	booktitle = {Proceedings of the International Association of Management 15th Annual International Conference}
}
@conference {
	title = {Estimation of Hidden Markov Models for Partially Observed Risk Sensitive Control Problems},
	author = {Frankpitt, Bernard., Baras, John S.},
	year = {1997},
	month = {07/1997},
	abstract = {We look at the problem of estimation for partially observed, risk-sensitive control problems with finite state, input and output sets, and receding horizon. We describe architectures for risk-sensitive controllers, and estimation, and we state conditions under which both the estimated model converges to the true model, and the control policy will converge to the optimal risk sensitive policy.},
	address = {Cyprus, Greece},
	booktitle = {5th IEEE Mediterranean Conference on Control and Systems}
}
@conference {
	title = {Hybrid Communication Networks for Video and Broadband Data Services},
	author = {Baras, John S.},
	year = {1997},
	month = {07/1997},
	address = {Alexandria, Egypt},
	booktitle = {Second IEEE Symposium on Computers and Communications}
}
@conference {
	title = {Nonlinear Hoo Control with Delayed Measurements},
	author = {Baras, John S., Patel, Nital S.},
	year = {1997},
	month = {07/1997},
	abstract = {This paper considers the nonlinear H-infinity control problem for systems subject to delayed measurements. Necessary and sufficient conditions for the solvability of the problem are presented. A key point of our approach is the extension of the information state concept. In particular, the information state is no longer the "worse case cost to come" function. We also present the certainty equivalence principle for such systems, and draw an analogy with the solution to the linear case. The paper ends with an example.},
	address = {Brussels, Belgium},
	booktitle = {4th European Control Conference (ECC\&rsquo;97)}
}
@conference {
	title = {Identification of Noisy FM Signals Using Nonorthogonal Wavelet Transforms},
	author = {Teolis, Carole A., Baras, John S.},
	year = {1997},
	month = {04/1997},
	address = {Orlando, Florida},
	booktitle = {11th Annual SPIE International Symposium on Aerospace/Defense Sensing, Simulation and Controls},
	pages = {pp. 590-601}
}
@conference {
	title = {From Robust to Intelligent Control},
	author = {Baras, John S.},
	year = {1997},
	month = {03/1997},
	address = {Champaign, IL},
	booktitle = {Lecture in the Coordinated Sciences Laboratory},
	organization = {University of Illinois at Urbana{\textendash}Champaign}
}
@conference {
	title = {Tactical and Strategic Communication Network Simulation and Performance Analysis},
	author = {Baras, John S., Corson, Scott M., Doan, Khoa., Jang, Kap D., Liu, Mingyan., Misra, Archan., Xie, Hui.},
	year = {1997},
	month = {01/1997},
	abstract = {We describe a framework for the efficient modeling and performance evaluation of large networks consisting of a mixture of strategic and tactical components. The method emphasizes hierarchical, layered techniques that are fed parametric models at the lower level. In addition to the algorithmic structure, and some initial algorithms we describe an object-oriented software architecture that is under development to support these algorithmic methods in a distributed environment.},
	address = {College Park, MD},
	booktitle = {First ATIRP Annual Conference: Advanced Telecommunications/Information Distribution Research Program},
	pages = {pp. 343-347},
	organization = {University of Maryland}
}
@conference {
	title = {Performance Analysis of PNNI Routing in ATM Networks: Hierarchical Reduced Load Approximation},
	author = {Xie, Hui., Baras, John S.},
	year = {1997},
	month = {01/1997},
	abstract = {In this paper, we investigate the performance issue of PNNI routing for ATM networks. A brief introduction to PNNI routing protocol is given. We extend the reduced load approximation algorithm to ATM networks with PNNI routing. A hierarchical reduced load approximation scheme is proposed. The scheme includes two steps: the reduced load approximation algorithm is first applied on the aggregated network at upper level; then the approximation is refined at the lower level as needed using the results from the upper level. This hierarchical scheme follows the PNNI routing framework and results a fast and scaleable algorithm.},
	address = {Monterey, CA},
	booktitle = {MILCOM \&rsquo;97},
	pages = {pp. 998-1002}
}
@conference {
	title = {Adaptive Data Broadcasting Using Air-Cache},
	author = {Stathatos, Kostas., Roussopoulos, Nick., Baras, John S.},
	year = {1996},
	month = {11/1996},
	abstract = {In the Data Air Waves Project at the University of Maryland, we are integrating Direct Broadcast Satellite (DBS) systems with terrestrial networks to provide a hybrid and effective communication substrate lying between data resources and remote/mobile user applications. Smooth integration of these two media balances the need for rapid data dissemination to very large numbers of clients and on-demand interactive data services. This paper describes the air-cache, a method for effective data broadcasting and an algorithm which rapidly adapts the content of the cache based on the "misses" which result in explicit (on-demand) data requests. Simulation results show that the hypothesis of adapting based only on the misses performs quite reasonable and has very little deviation from a system that has complete information - both hits and misses.},
	address = {Rye, New York},
	booktitle = {First International Workshop on Satellite-based Information Services (WOSBIS)},
	pages = {pp. 30-37}
}
@conference {
	title = {Integrating Tradeoff Analysis and Plan-Based Evaluation of Designs for Microwave Modules},
	author = {Trichur, Vinai., Ball, Mike., Baras, John S., Hebbar, Kiran., Minis, Ioannis., Nau, Dana S., Smith, Stephen J J.},
	year = {1996},
	month = {10/1996},
	abstract = {In this paper, we describe our current work towards the integration and enhancement of the capabilities of EDAPS and EXTRA. We integrate EXTRA{\textquoteright}s functionality with the intiial design step of EDAPS. In the resultant system, the user, supported by an enhanced tradeoff analysis capability, can select and describe a promising preliminary design and process plan based on the analysis of a variety of alternatives from both an electrical and mechanical perspective. This preliminary design is then subjected to further analysis and refinement using existing EDAPS capabilities. In addition to the integration of these two systems, specific new functions have been developed, including tradeoff analysis over a much broader set of criteria, and the ability of the tradeoff module to query the process planner to determine costs of individual options.},
	address = {Troy},
	booktitle = {Conference on Agile and Intelligent Manufacturing Systems}
}
@conference {
	title = {Reduced Complexity Nonlinear H$\infty$ Controllers: Relation to Certainty Equivalence},
	author = {Baras, John S., Patel, Nital S.},
	year = {1996},
	month = {06/1996},
	abstract = {This paper considers the problem of constructing reduced complexity controllers for output feedback nonlinear H$\infty$ control. Conditions are obtained under which such controllers achieve the closed loop performance requirements. These controllers are non-optimal in general. However, in case optimality holds, they are in fact the certainty equivalence controllers. Conditions under which certainty equivalence holds are simplified and linked to the solvability of a functional equation.},
	address = {San Francisco, CA},
	booktitle = {IFAC\&rsquo;96, 13th World Congress International Federation of Automatic Control},
	pages = {pp. 383-387}
}
@conference {
	title = {Weak Continuity with Structural Constraints},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1996},
	month = {06/1996},
	abstract = {Nonlinear regression and nonlinear regularization are two powerful approaches to segmentation and nonlinear filtering. In this correspondence, we propose a hybrid approach that effectively combines the best of both worlds and can be efficiently implemented via the Viterbi algorithm.},
	address = {Corfu, Greece},
	booktitle = {8th IEEE Signal Processing Workshop on Statistical Signal and Array Processing}
}
@conference {
	title = {Computer-Aided Selection of Window and Level for Filmless Radiology},
	author = {Sidiropoulos, N D., Baras, John S., Siegel, E., Protopapas, Z., S. M. Pomerantz, Reiner, B I.},
	year = {1996},
	month = {06/1996},
	address = {Denver, Colorado},
	booktitle = {SCAR \&lsquo;96},
	pages = {pp. 251-256}
}
@conference {
	title = {Robust Control of Semiconductor Manufacturing Processes},
	author = {Baras, John S., Patel, Nital S.},
	year = {1996},
	month = {06/1996},
	abstract = {This paper considers the control of semiconductor manufacturing processes. We start by considering the run to run control problem. We pose the problem in a risk-sensitive control framework, and derive the recursion for the information state. We then take large deviation type limits, and go on to show that the limiting information state recursion is related to that arising in solving ultimate boundedness control problems. For completeness we present the solution to the deterministic problem. The paper ends with an example involving application of run to run control to end-pointing.},
	address = {Williamsburg, VA},
	booktitle = {AMS-SIAM Summer Seminar on Mathematics of Stochastic Manufacturing Systems, Lectures in Applied Mathematics}
}
@conference {
	title = {Robust Recognition of Cellular Telephone Speech by Adaptive Vector Quantization},
	author = {Sonmez, Kemal M., Rajasekaran, Raja., Baras, John S.},
	year = {1996},
	month = {05/1996},
	abstract = {The performance degradation as a result of acoustical environment mismatch remains an important practical problem in speech recognition. The problem carries a greater significance in applications over telecommunication channels, especially with the wider use of personal communications systems such as cellular phones which invariably present challenging acoustical conditions. In this work, we introduce a vector quantization (VQ) based compensation technique which both makes use of a priori information about likely acoustical environments and adapts to the test environment to improve recognition. The technique is progressive and requires neither simultaneously recorded speech from the training and the testing environments nor EM-type batch iterations. Instead of using simultaneously recorded data, the integrity of the updated VQ codebooks with respect to acoustical classes is maintained by endowing the codebooks with a topology of reference environment. We report results on the McCaw Cellular Corpus where the technique decreases the word error for continuous ten digit recognition of cellular hands-free microphone speech with land line trained models from 23.8\% to 13.6\% and the speaker dependent voice calling sentence error from 16.5\% to 10.6\%.},
	address = {Atlanta, Georgia},
	booktitle = {IEEE (ICASSP 96) Conference on Acoustics, Speech, and Signal Processing},
	pages = {pp. 503-506}
}
@conference {
	title = {Constructing Optimal Wavelet Basis for Image Compression},
	author = {Zhuang, Yan., Baras, John S.},
	year = {1996},
	month = {05/1996},
	abstract = {We study the problem of choosing an image based optimal wavelet basis with compact support for image data compression and provide a general algorithm for computing the optimal wavelet basis. We parameterize the mother wavelet and scaling function of wavelet systems through a set of real coefficients of the relevant quadrature mirror filter (QMF) banks. We further introduce decomposition entropy as an information measure to describe the distance between a given digital image and its projection into the subspace spanned by the wavelet basis. The optimal basis for the given image is obtained through minimizing this information measure. The resulting subspace is used for image analysis and synthesis. Experiments show improved compression ratios due to the application of the optimal wavelet basis and demonstrate the potential applications of our methodology in image compression. This method is also useful for constructing efficient wavelet-based image coding systems.},
	address = {Atlanta, Georgia},
	booktitle = {IEEE (ICASSP) Conference on Acoustics, Speech, and Signal Processing},
	pages = {pp. 2351-2354}
}
@conference {
	title = {Robust Nonlinear Control of a Rapid Thermal Processor},
	author = {Baras, John S., Patel, Nital S.},
	year = {1996},
	month = {05/1996},
	abstract = {This paper presents application of robust multivariable nonlinear control to the temperature control problem for rapid thermal processing systems. The controller designed achieves good tracking and temperature uniformity for a wide range of processing conditions.},
	address = {Los Angeles, CA},
	booktitle = {13th International Conference on Chemical Vapor Deposition (CVD-XIII)},
	pages = {pp. 171-176}
}
@conference {
	title = {Simple Calls for Flexible Constructs Using the Traditional File API},
	author = {Gupta, Sandeep., Baras, John S., Kelley, Steve., Roussopoulos, Nick.},
	year = {1996},
	month = {04/1996},
	abstract = {We present the design for a remote QOS/Control interface to the transport protocol using the read/write calls from the traditional file system API, with simple extensions resulting in a very flexible interface. We limit the interface to the kernel to be read/write, and introduce two cells, atleast~one of which needs to be a system service (dsplice system call or implemented otherwise). These calls use file descriptor as input and output parameters, and because of that have a much more flexible interface than the traditional ioctl/fcntl~interface. The resulting API can be used to construct efficient communication schemes and result in simpler and efficient ways for distributed interaction. Parts of this API have been implemented in our ongoing experiments. The adjoining figures outline the potential for flexibility.},
	address = {New Jersey},
	booktitle = {Open Signaling for ATM, Internet and Mobile Networks Workshop (OPENSIG)},
	organization = {Columbia University}
}
@conference {
	title = {A Statistical Complexity Framework for Topology Preserving Adaptive Vector Quantization},
	author = {Sonmez, Kemal M., Baras, John S.},
	year = {1996},
	month = {03/1996},
	abstract = {We propose a statistical model complexity framework for topology preserving adaptive vector quantization. In this setting, the adaptation of the neighborhood function during training of the codebooks, which is essential for producing global organization, may be regarded as increasing the statistical model complexity as more data become available. Therefore, the training is equivalent to on the fly optimization of the bias/variance trade-off.},
	address = {Princeton, NJ},
	booktitle = {CISS\&rsquo;96}
}
@conference {
	title = {Consistency and Performance of Concurrent Interactive Database Appications},
	author = {Stathatos, Kostas., Kelley, Steve., Roussopoulos, Nick., Baras, John S.},
	year = {1996},
	month = {02/1996},
	address = {New Orleans, Louisiana},
	booktitle = {12th IEEE International Conference of Data Engineering}
}
@conference {
	title = {Hybrid Network Management},
	author = {Baras, John S., Ball, Mike., Karne, Ramesh K., Kelley, Steve., Jang, Kap D., Plaisant, Catherine., Roussopoulos, Nick., Stathatos, Kostas., Vakhutinsky, Andrew., Valluri, Jaibharat., Whitefield, David.},
	year = {1996},
	month = {02/1996},
	abstract = {We Describe our collaborative efforts towards the design the implementation of a next generation integrated network management system for Hybrid networks (INMS/HN).We describe the overall software architecture of the system at its current stage of development. This network management system is specifically designed to address issues relevant for complex heterogeneous networks consisting of seamlessly interoperable terrestrial and satellite networks. Network management systems are~key elements for interoperability in such network. We describe the integration of~configuration management and performance management. In particular, we describe the object~model, issues of the Graphical User Interface (GUI), browsing tools and performance data graphical widget displays, management information database (MIB) organization issues. Several components of the system are being commercialized by Hughes Network System. ~~},
	address = {Washington DC},
	booktitle = {AIAA: 16th International Communications Satellite Systems Conference and Exhibit},
	pages = {pp. 490-500}
}
@conference {
	title = {Asymmetric Internet Access Over Satellite-Terrestrial Networks},
	author = {Arora, Vivek., Suphasindhu, Narin., Baras, John S., Dillon, Douglas.},
	year = {1996},
	month = {02/1996},
	abstract = {DirecPC Turbo Internet is a low-cost hybrid( Satellite-terrestrial) High-speed digital transmission system developed as a collaborative effort between the Centre for satellite and Hybrid Communication Networks and Hughes Network Systems. The System uses receive only satellite links for downstream data delivery and public telephone networks at modem speed to provide the upstream communication path.},
	address = {Washington DC},
	booktitle = {Proceedings of the AIAA: 16th International Communications Satellite Systems Conference and Exhibit},
	pages = {pp. 476-482}
}
@conference {
	title = {ATM in Hybrid Networks},
	author = {Baras, John S.},
	year = {1996},
	month = {01/1996},
	abstract = {A discussion of the extensions or modifications required to integrate ATM into hybrid networks,~i.e. seamlessly interconnected terrestrial and space, wireline and wireless networks will be presented. In this context, the discussion will include, interoperability problems and issues, asymmetric channels, and various data rates. Several issues with proposed standards will also be addressed.~},
	address = {Santa Clara, CA},
	booktitle = {Design SuperCon 1996},
	pages = {pp. 1-1 to 1-13}
}
@conference {
	title = {Integrated Network Management System for Hybrid Networks},
	author = {Baras, John S., Ball, Mike., Karne, Ramesh K., Kelley, Steve., Jang, Kap D., Plaisant, Catherine., Roussopoulos, Nick., Stathatos, Kostas., Vakhutinsky, Andrew., Valluri, Jaibharat., Whitefield, David.},
	year = {1996},
	month = {01/1996},
	abstract = {We describe our collaborative effort towards the design and implementation of next generation integrated network management system for Hybrid networks(INMS/HN).We describe the overall software architecture of the system at its current stage of development.This network management system is specifically designed to address issues relevant for complex heterogeneous networks consisting of seamlessly interoperable terrestrial and satellite networks. Network management systems are a key element for interoperability in such network. We describe the integration of configuration management and performance management. The next step in this integration is fault management. In particular, we describe the object model, issues of the Graphical User Interfaces (GUI), browsing tools and performance data graphical widget displays, management information~database (MIB) organization issues. Several components of the system are being commercialized by Hughes Network Systems.},
	address = {Albuquerque, New Mexico},
	booktitle = {1st Conference of Commercial Development of Space\&rdquo;},
	pages = {pp. 345-350}
}
@conference {
	title = {Effective Extensions of Internet in Hybrid Satellite-Terrestrial Networks},
	author = {Arora, Vivek., Suphasindhu, Narin., Baras, John S., Dillon, Douglas.},
	year = {1996},
	month = {01/1996},
	abstract = {DirecPC Turbo Internet is a low-cost hybrid( Satellite-terrestrial) High-speed digital transmission system developed as a collaborative effort between the Centre for satellite and Hybrid Communication Networks and Hughes Network Systems. The System uses receive only VSAT-satellite links for downstream data delivery and public telephone networks at modem speeds to provide the upstream communication path.},
	address = {Albuquerque, New Mexico},
	booktitle = {1st Conference of Commercial Development of Space},
	pages = {pp. 339-344}
}
@conference {
	title = {Some results on risk-sensitive control with partial information},
	author = {Baras, John S., Bensoussan, Alain., Elliott, Robert J.},
	year = {1995},
	month = {12/1995},
	abstract = {We consider in this presentation the risk-sensitive control problem with partial observation. Risk-sensitive Zakai and Kushner equations are established and studied. They are explicitly solved in all situations where the classical Zakai and Kushner equations can be solved. In these cases the solution of the control problem can be characterized nicely. Also, the small noise case is considered. The limit problem is a differential game with output control. The full justification of all the results is still a long range plan.},
	address = {New Orleans, Louisiana},
	booktitle = {The 34th IEEE Conference on Decision and Control},
	pages = {pp. 2853-2857}
}
@conference {
	title = {Information State for Robust Control of Set-Valued Discrete Time Systems},
	author = {Baras, John S., Patel, Nital S.},
	year = {1995},
	month = {12/1995},
	abstract = {We consider the problem of robust output feedback control of set-valued discrete time systems. Such systems appear frequently in applications such as process control. The aim is to motivate and obtain an efficient formulation of robust control problems and the resulting structure of the controller for such systems. This formulation, and the controller structure are obtained by taking small noise limits of the information state dynamics arising in a related risk-sensitive stochastic control problem. The necessary and sufficient conditions for solvability are also presented.},
	address = {New Orleans, Louisiana},
	booktitle = {The 34th IEEE Conference on Decision and Control},
	pages = {pp. 2302-2307}
}
@conference {
	title = {On Morphological Openings and Closings of Signals in Shaped Noise},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1995},
	month = {10/1995},
	abstract = {In recent work, we have shown that morphological Openings and closingS can be viewed as consistent MAP estimators of morphologically Smooth binary image signals immersed in i.i.d. union (clutter) noise, or suffering from i.i.d. random dropouts. We revisit this viewpoint under a different set of assumptions, which allows the explicit incorporation of geometric and morphological constraints into the noise model, i.e., the noise may now exhibit geometric Structure; surprisingly, it turns out that this affects neither the optimality nor the consistency of these filters.},
	address = {Washington DC},
	booktitle = {The IEEE 1995 International Conference on Image Processing},
	pages = {pp. 518-521}
}
@conference {
	title = {Decision Making Assistant for Integrated Product and Process Design Environment},
	author = {Karne, Ramesh K., Baras, John S., Ball, Michael O., Bashyam, Sridhar., Townsley. Mark., Huang, Feng., Trichur, Vinai., Karir, Manish., Xie, Hui., Inbar, Asaf.},
	year = {1995},
	month = {10/1995},
	abstract = {We present a decision making assistant tool for integrated product and process design environment for manufacturing applications. Specifically, we target microwave modules which use electro-mechanical components and require optimal solutions to reduce cost, improve quality, and gain leverage in time to market the product. This tool will assist the product and process designer to improve their productivity and also enable to cooperate and coordinate their designs through a common design interface. We consider a multiobjective optimization model that determines components and processes for a given conceptual designs for microwave modules. This model outputs a set of solutions that are Pareto optimal with respect to cost, quality, and other metrics. In addition, we identify System integration issues for Manufacturing applications, and propose an architecture which will serve as a building block to our continuing research in virtual manufacturing applications.},
	address = {Albuquerque, New Mexico},
	booktitle = {The Symposium on Timely Realization of Affordable Military Systems Through Enhanced Manufacturing Technology}
}
@conference {
	title = {On the Selection of Parts and Processes during Design of Printed Circuit Board Assemblies},
	author = {Ball, Michael O., Baras, John S., Bashyam, Sridhar., Karne, Ramesh K., Trichur, Vinai.},
	year = {1995},
	month = {10/1995},
	abstract = {We consider a multiobjective optimization model that determines components and processes for given conceptual designs of printed circuit board assemblies. Specifically, our model outputs a set of solutions that are Pareto optimal with respect to a cost and a quality metric. The discussion here broadly outlines an integer programming based solution strategy and represents in-progress work being carried out in collaboration with a manufacturing firm.},
	address = {Paris, France},
	booktitle = {The INRIA/IEEE Conference on Emerging Technologies and Factory Automation},
	pages = {pp. 241-248}
}
@conference {
	title = {Designing Response Surface Model Based Run by Run Controllers: A New Approach},
	author = {Baras, John S., Patel, Nital S.},
	year = {1995},
	month = {10/1995},
	abstract = {This paper presents a framework for carrying out robust Run by Run (RbR) control via a set-theoretic approach. In particular the RbR controller developed tries to minimize the worst case performance of the plant. This gives us a methodology to handle uncertainty. An interesting consequence of using the set valued approach is that now we can relax the assumptions made on the statistics of the noise. Hence, we can also deal with non-Gaussian and correlated noise. We provide results comparing the performance of the controller to a recursive least squares based controller.},
	address = {Austin, Texas},
	booktitle = {The 1995 International Electronic Manufacturing Technology Symposium},
	pages = {pp. 210-217}
}
@conference {
	title = {New Results on Optimality and Consistency of Morphological Openings and Closings},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1995},
	month = {07/1995},
	abstract = {It has been recently shown that morphological openings and closings can be viewed as consistent MAP estimators of morphologically smooth signals in i.i.d. noise. We revisit this viewpoint under a different set of assumptions, which allows the explicit incorporation of geometric and morphological constraints into the noise model, i.e., the noise may now exhibit geometric structure; surprisingly, it turns out that this affects neither the optimality nor the consistency of these filters.},
	address = {San Diego, CA},
	booktitle = {The Morphological Image Processing and Random Image Modeling},
	pages = {pp. 118-122}
}
@conference {
	title = {Nonlinear Filtering: the Set-Membership (Bounding) and the H$\infty$ Techniques},
	author = {Baras, John S., Kurzhansky, A.},
	year = {1995},
	month = {06/1995},
	abstract = {We consider the problem of nonlinear filtering within the framework of deterministic uncertain systems (i.e. control systems with disturbances). We investigate the relationship between the two main approaches to the problems: the set-membership approach and the nonlinear Ho approach. We establish an interesting connection between the two basic constructs of these two approaches: the information state and the information domain. This connection helps to establish a clearer understanding~the problem and will play a fundamental role in nonlinear robust output feedback control.},
	address = {Davis},
	booktitle = {The NOLCOS{\textquoteright}95 IFAC Workshop},
	pages = {pp. 449-454},
	organization = {University of California}
}
@conference {
	title = {Robust Control of Discrete Time Generalized Dynamical Systems: Finite and Infinite Time Results},
	author = {Baras, John S., Patel, Nital S.},
	year = {1995},
	month = {06/1995},
	abstract = {This paper deals with the output feedback robust control of discrete time systems modeled as dynamic inclusions. This formulation allows for the more typical in practice situation of non-additive disturbances. The control problem is solved via dynamic programming. Separation between estimation and control is achieved by using the concept of an information state. The nature of the information state is investigated.},
	address = {Seattle, Washington},
	booktitle = {The 1995 American Control Conference},
	pages = {pp. 1990-1994}
}
@conference {
	title = {The Multiple LAG Process and Its Estimation},
	author = {Sonmez, Kemal M., Baras, John S.},
	year = {1995},
	month = {06/1995},
	abstract = {We derive estimators for the multiple lag process, a generalization of the lag process, via spectral representations of stationary processes by complex random spectral measures. We present estimators of transfer functions for the multiple lag model with a given vector of lags and derive a multiple-lag (quadratic) coherence which can be maximized to choose the best vector of lags in the minimum mean squared error sense from a given set of lag vectors. We also demonstrate the estimation scheme by a simulation example and point out possible applications for the multiple-lag model in speech processing.},
	address = {Detroit, MI},
	booktitle = {The International Conference on Acoustics, Speech and Signal Processing},
	pages = {pp. 1697-1700}
}
@conference {
	title = {Wavelet Based Progressive Classification with Learning: Applications to Radar Signals},
	author = {Baras, John S., Wolk, Sheldon I.},
	year = {1995},
	month = {04/1995},
	abstract = {In this paper we investigate the problem of fast and accurate classification of naval targets from radar returns. The algorithms can be applied to both 1-D and 2-D data (i.e. high range resolution and imaging radar returns). We describe the structure of these algorithms and report experimental results on their performance with synthetic returns from ships.

We have successfully addressed the problem of reducing the target model representations with respect to viewpoint variations and other Sensor parametric variations. Our method can be viewed as a quantization of the space of sensing Operations. The resulting multiresolution aspect graph is a (relational) graph representation of this quantization. Aspect graphs of target radar returns are generated algorithmically. Since our off-line model/parameter tuning methods are based on general vector quantization, our methods extend naturally and efficiently to multi-sensor data: LADAR, TV, mmWave, SAR, etc.. We describe new results on the {\textquotedblleft}continuity{\textquotedblright} of the aspect graph, new properties and improvements of our algorithmic constructions.

Our basic classification algorithm utilizes a cascade of a wavelet preprocessor followed by a tree-structured clustering algorithm: a learning mode can be also added. We develop a high performance parallel progressive classification algorithm and report On its performance and Complexity. We show experiments illustrating that the parallel algorithm Outperforms a Compound version (which is the more intuitive choice) and that it has performance close to Bayes optimal classification (via comparison to Learning Vector Quantization). We Outline an analytical framework for establishing these results theoretically. We also discuss similar experiments from face recognition and medical image classification problems.},
	address = {Orlando, Florida},
	booktitle = {The SPIE 1995 International Symposium on Aerospace/ Defense Sensing and Dual-Use Photonics},
	pages = {pp. 339-350}
}
@conference {
	title = {Image Compression Using Optimal Wavelet Basis},
	author = {Zhuang, Yan., Baras, John S.},
	year = {1995},
	month = {04/1995},
	abstract = {We study the problem of choosing an image based optimal wavelet basis with compact support for image data Compression and provide a general algorithm for computing the optimal wavelet basis. We parameterize the mother wavelet and the scaling function of wavelet systems through a set of real coefficients of the relevant quadrature mirror filter (QMF) banks. We further introduce the concept of decomposition entropy as an information measure to describe the distance between a given digital image and its projection into the subspace spanned by the wavelet basis. The optimal basis for the given image is obtained through minimizing this information measure. The resulting subspace is used for image analysis and Synthesis. A gradient based Optimization algorithm is developed for computing the image based optimal wavelet basis. Experiments show improved compression ratios due to the application of the Optimal wavelet basis and demonstrate the potential applications of Our methodology in image Compression. This method is also useful for constructing efficient wavelet-based image coding systems.},
	address = {Orlando, FL},
	booktitle = {The SPIE 1995 International Symposium on Aerospace/ Defense Sensing and Dual-Use Photonics},
	pages = {pp 131-140}
}
@conference {
	title = {The Wavelet Processing Workstation: An Interactive MATLAB Based Computational Tool for Wavelet Processing},
	author = {Teolis, Carole A., Baras, John S.},
	year = {1995},
	month = {04/1995},
	abstract = {We present a highly powerful, modular, and interactive software tool for the analysis of time-frequency coherent signals via wavelet transformations. A major design goal of the Wavelet Signal Processing Workstation (WSPW) is to maximize ease of use while minimizing programming complexity. As such the WSPW makes ample use of graphical mouse driven user interfaces and in turn, allows powerful signal processing, classification, and identification techniques to be rapidly implemented and tested. Because it has been developed using MATLAB, the WSPW is easily extensible and inherently portable between varying system architectures. Although the emphasis of this paper is on the wavelet representation of signals, the WSPW has proven itself a valuable tool in applications including radar source identification and signal classification.},
	address = {Orlando, Florida},
	booktitle = {The SPIE 1995 International Symposium on Aerospace/ Defense Sensing and Dual-Use Photonics},
	pages = {pp. 592-603}
}
@conference {
	title = {The Combinatorial Basis of Uniformly Bounded Discrete Random Set Theory},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1995},
	month = {03/1995},
	abstract = {We provide a purely combinatorial view of the essential structure of uniformly bounded DRS theory without any reference to discrete probability and highlight the two fundamental functionals arising out of this exposition. The key tool is Moebius inversion. We conclude that the study of uniformly bounded DRS theory is the study of Incidence functions on Boolean algebras of finite rank. Some useful results arise as a by-product of this investigation.},
	address = {Baltimore, MD},
	booktitle = {The 29th Annual Conference on Information Sciences and Systems},
	pages = {pp. 463-467},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Hybrid Network Architectures: A Framework for Comparative Analysis},
	author = {Baras, John S., Campanella, Joseph S., Kirkwood, Timothy.},
	year = {1995},
	month = {01/1995},
	abstract = {The Global Information Infrastructure of the future will include a great variety of heterogeneous, seamlessly interconnected networks. There are strong variety of heterogeneous, seamlessly interconnected networks. There are strong technical and economic reasons predicating the emergence of these hybrid networks which will include many diverse terrestrial (tethered or wireless) and satellite networks in an interoperating configuration. This paper critically analyzes the basis for these new architectures and examines the various possibilities that will emerge in various phases in the future. A summary view is presented for these emerging hybrid architectures, the alternative components and subsystems available and the trade-offs that must be considered. The role of satellites is carefully analyzed and several conclusions are drawn. This paper will present a summary of the work and views of the Center for Satellite and Hybrid Communication Networks to date, in this important area. Specific design and performance evaluation tools being developed will also be described.},
	address = {Albuquerque, New Mexico},
	booktitle = {The 12th Symposium on Space Nuclear Power and Propulsion/Commercialization},
	pages = {pp. 45-50}
}
@conference {
	title = {Hybrid Internet Access},
	author = {Arora, Vivek., Baras, John S., Falk, Aaron David., Dillon, Douglas., Suphasindhu, Narin.},
	year = {1995},
	month = {01/1995},
	abstract = {Access to the Internet is either too slow (dial-up SLIP) or too expensive (switched 56 kbps, frame relay) for the home user or small enterprise. The Center for Satellite and Hybrid Communication Networks and Hughes Network Systems have collaborated using systems integration principles to develop a prototype of a low-cost hybrid (dial-up and satellite) network terminal which can deliver data from the Internet to the user at rates up to 160 kbps. An asymmetric TCP/IP connection is used breaking the network link into two physical channels: a terrestrial dial-up for carrying data from the terminal into the Internet and a receive-only satellite link carrying IP packets from the Internet to the user. With a goal of supporting bandwidth hungry Internet applications such as Mosaic, Gopher, and FTP, this system has been designed to support any Intel 80386/486 PC, any commercial TCP/IP package, any unmodified host on the Internet, and any of the routers, etc., within the Internet. The design exploits the following three observations: 1) satellites are able to offer high bandwidth connections to a large geographical area, 2) a receive-only VSAT is cheap to manufacture and easier to install than one which can also transmit, and 3) most computer users, especially those in a home environment, will want to consume much more information than they generate. IP encapsulation, or tunneling, issued to manipulate the TCP/IP protocols to route packets asymmetrically.},
	address = {Albuquerque, New Mexico},
	booktitle = {The 12th Symposium on Space Nuclear Power and Propulsion/Commercialization},
	pages = {pp. 69-74}
}
@conference {
	title = {Dynamic Routing in Hybrid Networks with Integrated Voice and Data Traffic},
	author = {Baras, John S., Chen, Shihwei.},
	year = {1995},
	month = {01/1995},
	abstract = {In this paper, we consider a large hybrid network which consists of a low-delay terrestrial sub-network and a high-bandwidth satellite sub-network. Both voice and data traffic are transmitted and routed through the same network. We show how to route both traffic via ground and/or satellite links. Two common voice/data integrated protocols such as fixed boundary and movable boundary schemes for the satellite channel are investigated, and the performance of both schemes is evaluated. The optimal splitting ratios for voice and data at the SIMPs (Satellite Interface Message Processors) are found using a powerful numerical optimization package (FSQP). We also develop dynamically optimal splitting ratios between satellite network and terrestrial network for data and voice traffic. We constantly monitor the traffic and measure the arrival rate and occupancy of every link. Based on these data, we optimize data traffic delay in a suitable time-frame under the constraints of voice traffic blocking probabilities of voice transmission links being less than specified value, which is up to system{\textquoteright}s design or users{\textquoteright} requirements. A dynamic routing algorithm is presented.},
	address = {Albuquerque, New Mexico},
	booktitle = {The 12th Symposium on Space Nuclear Power and Propulsion/Commercialization},
	pages = {pp. 21-26}
}
@conference {
	title = {Next Generation Network Management Technology},
	author = {Atallah, George C., Ball, Mike., Baras, John S., Goli, Shravan., Karne, Ramesh K., Kelley, Steve., Kumar, Harsha., Plaisant, Catherine., Roussopoulos, Nick., Shneiderman, Ben., Mulugu, Srinivasaro., Stathatos, Kostas., Teittinen, Marko., Whitefield, David.},
	year = {1995},
	month = {01/1995},
	abstract = {Today{\textquoteright}s telecommunications networks are becoming increasingly large, complex, mission critical and heterogeneous in several dimensions. For example, the underlying physical transmission facilities of a given network may be "mixed media" (copper, fiber-optic, radio, and satellite); the Sub networks may be acquired from different vendors due to economic, performance, or general availability reasons; the information being transmitted over the network may be "multimedia" (video, data, voice, and images) and, finally, varying performance criteria may be imposed e.g. data transfer may require high throughput while the others, whose concern is voice communications, may require low call blocking probability. For these reasons, future telecommunications networks are expected to be highly complex in their services and operations. Due to this growing complexity and the disparity among management systems for individual sub networks, efficient network management systems have become critical to the current and future success of telecommunications companies. This paper addresses a research and development effort which focuses on prototyping configuration management, since that is the central process of network management and all other network management functions must be built upon it. Our prototype incorporates ergonomically designed graphical user interfaces tailored to the network configuration management subsystem and to the proposed advanced object-oriented database structure. The resulting design concept follows open standards such as Open Systems Interconnection (OSI) and incorporates object oriented programming methodology to associate data with functions, permit customization, and provide an open architecture environment.},
	address = {Albuquerque, New Mexico},
	booktitle = {The 12th Symposium on Space Nuclear Power and Propulsion/Commercialization},
	pages = {pp. 75-82}
}
@conference {
	title = {Robust H$\infty$ Output Feedback Control of Bilinear Systems},
	author = {Teolis, Carole A., Yuliar, S., James, Matthew R., Baras, John S.},
	year = {1994},
	month = {12/1994},
	abstract = {In this paper we present a solution to the robust Hoo output feedback control problem for bilinear systems over a finite time interval. The solution is obtained through the use of the information state method. We discuss the relation of the information state controller with the certainty equivalence controller under smoothness and uniqueness assumptions. Finally, numerical examples are provided to illustrate implementation issues of the information state feedback controller.},
	address = {Lake Buena Vista, Florida},
	booktitle = {The 33rd CDC Conference},
	pages = {pp. 1421-1426}
}
@conference {
	title = {Nonlinear H$\infty$ Control},
	author = {Baras, John S., James, Matthew R.},
	year = {1994},
	month = {12/1994},
	abstract = {This paper discusses various aspects of recent developments concerning the robust Hoo problem for continuous-time nonlinear systems. In the state feedback case, the problem can be solved in the framework of dissipative systems, and the associated storage functions solve the PDI in the viscosity sense. The main problem is then one of controller synthesis. In the output feedback case, the information state concept provides the appropriate framework. The solution is expressed in terms of a PDE for the information state (filter), and an infinite dimensional PDE or dissipation-type PDI for the value function (control). The attendant mathematical issues are discussed.},
	address = {Lake Buena Vista, Florida},
	booktitle = {The 33rd CDC Conference},
	pages = {pp. 1435-1438}
}
@conference {
	title = {Object Oriented Hybrid Network Simulation},
	author = {Baras, John S., Murad, Ahsun H., Jang, Kap D., Atallah, George C., Karne, Ramesh K., Campanella, Joseph S.},
	year = {1994},
	month = {11/1994},
	abstract = {The simulation of complex contemporary hybrid communication networks is a daunting task and cannot be handled by the array of conventional network simulation tools available today. This paper discusses the key issues involved in the visualization and simulation of complex hybrid networks and presents the design of an object-oriented hybrid network simulator being developed at the Center for Satellite and Hybrid Communication Networks (a NASA center for the commercial development of space), University of Maryland at College Park. This software incorporates a complex system simulation paradigm, advanced visualization techniques, a flexible interface and an object-oriented database to allow the simulator to be used not only as a network simulation tool, but also as a network design tool, as a network performance evaluation tool, and as part of an intelligent network management software.},
	address = {Washington DC},
	booktitle = {The Technology 2004 Conference}
}
@conference {
	title = {A System Design for a Hybrid Network Terminal Using Asymmetric TCP/IP to Support Internet Applications},
	author = {Falk, Aaron David., Suphasindhu, Narin., Dillon, Douglas., Baras, John S.},
	year = {1994},
	month = {11/1994},
	abstract = {The purpose of this paper is to describe the system design process used to build a prototype terminal which uses a hybrid satellite-terrestrial connection and "asymmetric" TCP/IP network protocols to give the computer user who has a minimum bandwidth modem connection to the Internet access to bandwidth hungry Internet applications.},
	address = {Washington DC},
	booktitle = {The Technology 2004 Conference}
}
@conference {
	title = {Derivation of Fuzzy Rules for Parameter Free PID Gain Tuning},
	author = {Baras, John S., Patel, Nital S.},
	year = {1994},
	month = {05/1994},
	abstract = {In this paper, rules for a fuzzy logic based PID tuner (expert) for stable dominant pole plants with large rise times are derived. Applications of the expert to separator temperature control, and to pH control are presented. It is observed that the expert can successfully tune the PID gains without requiring any process identification.},
	address = {Kyoto, Japan},
	booktitle = {The IFAC Symposium on Advanced Control of Chemical Processes (ADCHEM{\textquoteright}94)},
	pages = {pp. 319-324}
}
@conference {
	title = {Model Based Automatic Target Recognition from High Range Resolution Radar Returns},
	author = {Baras, John S., Wolk, Sheldon I.},
	year = {1994},
	month = {04/1994},
	abstract = {Economic descriptions of objects are essential for model-based ATR. We develop economic target descriptions based on high range resolution target returns, utilizing wavelet multiresolution representations and Tree Structured Vector Quantization, in its clustering mode. The algorithm automatically constructs the multi-scale aspect graph of the target, which is a most efficient model that guides the on-line ATR algorithm. This results in a progressive coding of the target model information and in an extremely efficient, hierarchical indexing of the stored target models. As a final outcome we obtain extremely fast recovery, search and matching during the on-line ATR operation. In addition, these scale space (or multiresolution) representations can be used to generate target fingerprints across a range of scales, unavailable heretofore, which aid substantially in target recognition even with occluded or spurious data.

We have Successfully addressed the problem of reducing the target model representations with respect to viewpoint variations and other sensor parametric variations. Our method can be viewed as a quantization of the space of sensing operations. The resulting aspect graph is a (relational) graph representation of this quantization. Aspect graphs of target radar returns are generated algorithmically. Since our off-line model/parameter tuning methods are based on general vector quantization, our methods extend naturally and efficiently to multi-sensor data: LADAR, TV, mmWave, SAR, etc..

We also investigate~the so-called new target insertion problem in a fielded ATR system, and the required fast re-programmability of the ATR system. We compare the performance and cost (both computational and hardware) of ATR algorithms based on the parallel use of single target aspect graphs vs ATR algorithms using the combined aspect graph for the group of targets under consideration. We show that efficient real-time ATR algorithms can be constructed using the aspect graph of each target in a parallel computation. The resulting architecture includes wavelet preprocessing with neural networks postprocessing. We use synthetic radar returns from ships as the experimental data to demonstrate the performance of the resulting ATR algorithm.},
	address = {Orlando, FL},
	booktitle = {The SPIE International Symposium on Intelligent Information Systems},
	pages = {pp. 57-66}
}
@conference {
	title = {Wavelet Based Progressive Classification of High Range Resolution Radar Returns},
	author = {Baras, John S., Wolk, Sheldon I.},
	year = {1994},
	month = {04/1994},
	abstract = {We investigate the problem of fast and accurate classification of high range resolution radar returns from ships. In addition, we investigate the problem of efficient organization of large databases of pulsed high resolution radar returns from multiple targets in order to economize memory requirements and minimize search time. We use synthetic radar returns from ships as the experimental data. We develop a novel algorithm for hierarchically organizing the database which utilizes a multiresolution wavelet representation working in synergy with a Tree Structured Vector Quantizer (TSVQ), utilized in its clustering mode. The tree structure is induced by the multiresolution decomposition of the radar returns. The TSVQ design algorithm is of the "greedy{\textquotedblright} type. We demonstrate that our algorithm automatically computes the aspect graph (i.e. the simultaneous representation of compressed pulses as functions of aspect and elevation) for a single target or for a group of targets. We also develop a novel optimization framework for the simultaneous design of the wavelet basis, the Tree-Structured Vector Quantizer and the Classification rule. We describe an efficient and promising implementation consisting of an adaptive Wavelet Transform - Tree Structured Vector Quantization with Learning. We show experimental results which indicate that the combined algorithm executes orders of magnitude faster data search time, with negligible performance degradation (as measured by rate-distortion curves).},
	address = {Orlando, FL},
	booktitle = {The SPIE International Symposium on Intelligent Information Systems},
	pages = {pp. 967-977}
}
@conference {
	title = {Optimal Wavelet Basis Selection for Signal Representation},
	author = {Zhuang, Yan., Baras, John S.},
	year = {1994},
	month = {04/1994},
	abstract = {We study the problem of choosing an optimal wavelet basis with compact support for signal representation and provide a general algorithm for computing the optimal wavelet basis. We first briefly review the multiresolution property of wavelet decompositions and the conditions for generating an Orthonormal basis of compactly supported discrete wavelets in terms of properties of quadrature mirror filter (QMF) banks. We then parameterize the mother wavelet and scaling function of wavelet systems through a set of real coefficients. We further introduce the concept of decomposition entropy as an information measure to describe the distance between a given signal and its projection onto the subspace spanned by the wavelet basis in which the signal is to be reconstructed. The optimal basis for the given signal is obtained through minimizing this information measure. We have obtained explicitly the sensitivity of dilations and shifts of the mother wavelet with respect to the coefficient set. A systematic approach is developed in this paper to derive the information gradient with respect to the parameter set from a given square integrable signal and an initial discrete basis of wavelets. The existence of the optimal basis for the wavelets has been proven in this paper. A gradient based Optimization algorithm is developed for computing the optimal wavelet basis.},
	address = {Orlando, FL},
	booktitle = {The SPIE International Symposium on Intelligent Information Systems},
	pages = {pp. 200-211}
}
@conference {
	title = {Shape Optimization of Distributed Sensors and Actuators for Smart Structure Control},
	author = {Zhuang, Yan., Baras, John S.},
	year = {1994},
	month = {02/1994},
	abstract = {We describe a design technique for optimal control in active structural vibration damping using smart materials. The vibration of a cantilever beam is stabilized by feedback the weighted integration of vibration velocity in the closed loop system through the application of distributed sensors and actuators made of smart materials. We model the beam by the Timoshenko beam model embedded with the distributed sensors and actuators to account for the shear and inertial effects on the structures. We propose an algorithm to find the optimal placement of the actuators and sensors so as to maximize the damping effect. An objective functional is defined based on the vibration energy of the system. The optimal shapes of the sensor and actuator are determined through minimizing the energy functional of the beam over the admissible shape function space subject to certain constraints. This~approach can be generalized to cases of plate damping and active control of more complicated smart structures as well.},
	address = {Orlando, FL},
	booktitle = {The SPIE: 1994 North American Conference on Smart Structures and Materials},
	pages = {pp. 381-388}
}
@conference {
	title = {Output Feedback Risk-Sensitive Control and Differential Games for Continuous-Time Nonlinear Systems},
	author = {James, Matthew R., Baras, John S., Elliott, Robert J.},
	year = {1993},
	month = {12/1993},
	abstract = {In this paper, we carry out a formal analysis of an output feedback risk-sensitive~stochastic control problem. Using large derivation limits this problem is related to a deterministic differential game. Both problems are solved using appropriate information states. The use of an information state~for the game problem is new and is the principal contribution of our work. Our results have important~implications for the nonlinear robust stabilization problem.},
	address = {San Antonio, Texas},
	booktitle = {The 1993 32nd  IEEE Conference on Decision and Control},
	pages = {pp. 3357-3360},
	organization = {Marriott rivercenter}
}
@conference {
	title = {Robust Output Feedback Control for Discrete-Time Nonlinear Systems:  The Finite Time Case},
	author = {Baras, John S., James, Matthew R.},
	year = {1993},
	month = {12/1993},
	abstract = {In this paper we present a new approach to the solution of the output feedback robust control problem. We employ the recently developed concept of information state for output feedback dynamic games and obtain necessary and sufficient conditions for the solution to the robust control problem expressed in terms of the information state. The resulting controller is an information state feedback controller~and is intrinsically infinite dimensional.},
	address = {San Antonio, Texas},
	booktitle = {The 1993 32nd  IEEE Conference on Decision and Control},
	pages = {pp. 51-55},
	organization = {Marriott rivercenter}
}
@conference {
	title = {Implementation of a Dynamic Game Controller for Partially Observed Discrete-Time Nonlinear Systems},
	author = {Teolis, Carole A., James, Matthew R., Baras, John S.},
	year = {1993},
	month = {12/1993},
	abstract = {In this paper we describe an implementation of a certainty equivalence controller for a discrete time partially observed dynamic game problem.},
	address = {San Antonio, Texas},
	booktitle = {The 1993 32nd  IEEE Conference on Decision and Control},
	pages = {pp. 2997-2998},
	organization = {Marriott rivercenter}
}
@conference {
	title = {VLSI Architectures for Orthonormal Wavelets Without Multipliers},
	author = {Frantzeskakis, Emmanuel., Baras, John S.},
	year = {1993},
	month = {11/1993},
	abstract = {The Discrete Wavelet Transform (DWT) is proving to be a highly effective tool in progressive coding of audio and video data. Due to the advances in ISDN network and high definition television (HDTV) technology, a high speed computation of the DWT has become very desirable. Since the algorithmic implementations on programmable DSP chips can not match the high throughput requirements of these applications, the use of Specialized VLSI designs has emerged. The wavelet transform can be implemented by a tree structured digital filter bank. In particular, for an orthogonal wavelet basis this filter bank exhibits the para unitarity property, thus it can be realized by using the Givens rotation as the basic building block. A complete parameterization for this class of Systems is known.

In this paper, we consider the architectural implementation of the DWT that is associated with an Orthonormal wavelet basis. We discuss the trade-offs involved in the use of distributed arithmetic and CORDIC processors for the implementation of the Givens rotation. The resulted circuits are modular, regular and they require only local communication. Furthermore, they involve only adders and ROM lookup tables and no multipliers. Consequently, they are very appropriate for VLSI implementation. The question of the on-line adaptation of the parameters of the circuit is also addressed. This feature is very important in adaptive signal processing applications. Although our discussion is focused on the one dimensional dyadic DWT, Our conclusions are projected to the M-band orthonormal wavelets and the two-dimensional DWT with quincunx subsampling.},
	address = {Pacific Grove, California},
	booktitle = {The 27th Annual Asilomar Conference on Signals, Systems and Computers}
}
@conference {
	title = {Efficient Organization of Large Ship Radar Databases Using Wavelets and Structured Vector Quantization},
	author = {Baras, John S., Wolk, Sheldon I.},
	year = {1993},
	month = {11/1993},
	abstract = {We investigate the problem of efficient representations of large databases of pulsed radar returns froTn naval vessels in order to economize memory and minimize search time. We use synthetic radar returns from ships as the experimental data. The results extend to real ISAR returns. We develop a novel algorithm for organizing the database, which utilizes a ~multiresolution wavelet representation working in synergy with a Tree Structured Vector Quantizer (TSWQ), utilized in its clustering mode. The tree Structure is induced by the multiresolution decomposition of the pulses. The TSVQ design algorithm is of the "greedy" type.~Our experiments todate indicate that the combined algorithm results in orders of magnitude faster data search time, with negligible performance degradation from the full search vector quantization. The combined algorithm provides an efficient indexing scheme (with respect to variations in aspect, elevation and pulse width) for radar data which can facilitate the development of ATR, surveillance and multi-sensor fusion systems.},
	address = {Pacific Grove, California},
	booktitle = {The 27th Annual Asilomar Conference on Signals, Systems and Computers},
	pages = {pp. 491-498}
}
@conference {
	title = {An Architectural Framework for Parallel Time-Recursive Computation},
	author = {Frantzeskakis, Emmanuel., Baras, John S., Liu, Ray K J.},
	year = {1993},
	month = {10/1993},
	abstract = {The time-recursive computation model has been proven particularly useful for the real-time evaluation of one and two-dimensional block transforms. Unlike the FFT based architectures, time-recursive ones require only local communication. Also, they are modular and regular, thus they are very appropriate for VLSI implementation and they allow high degree of parallelism.

In this paper, we establish an architectural framework for parallel time-recursive computation. We consider a class of linear operators that consists of the discrete time, time invariant, compactly supported, but otherwise arbitrary kernel functions. We specify the properties of the linear operators that can be implemented efficiently in a time-recursive way. Based on these properties, we develop a routine that produces a time-recursive architectural implementation for a given operator. This routine is instructive for the design of a CAD tool that will facilitate the derivation of time-recursive architectures. The design of architectures for the Discrete Cosine Transform and the Modulated Lapped Transform based on this routine is reported.},
	address = {Athens, Greece},
	booktitle = {The 4th Conference on Informatics , organized by the Greek Computer Society},
	pages = {pp. 1-12}
}
@conference {
	title = {Time-Recursive Computation and Real-Time Parallel Architectures, with Application on the Modulated Lapped Transform},
	author = {Frantzeskakis, Emmanuel., Baras, John S., Liu, Ray K J.},
	year = {1993},
	month = {07/1993},
	abstract = {The time-recursive computation has been proved particularly useful for the real-time evaluation of one and two-dimensional block transforms. Unlike the FFT based ones, time-recursive architectures require only local communication. Also, they are modular and regular, thus they are very appropriate for VLSI implementation and they allow high degree of parallelism.

In this paper, we establish an architectural framework for parallel time-recursive computation. We consider a class of linear operators that consists of the discrete time, time invariant, compactly supported, but otherwise arbitrary kernel functions. We specify the properties of the linear operators that can be implemented efficiently in a time-recursive way. Based on these properties, we develop a routine that produces a time-recursive architectural implementation for a given operator. This routine is instructive for the design of a CAD tool that will facilitate the architecture derivation.

Using this background, we design an architecture for the Modulated Lapped Transform (commonly called Modified Discrete Cosine Transform), which has linear cost in operator counts.},
	address = {San Diego, California},
	booktitle = {The 1993 SPIE International Symposium on Optical Science and Engineering},
	pages = {pp. 100-111}
}
@conference {
	title = {Time Series Modeling by Perceptrons: A Likelihood Approach},
	author = {Sonmez, Kemal M., Baras, John S.},
	year = {1993},
	month = {07/1993},
	abstract = {We consider neural network learning problems in which the objective is to learn the relationship between the inputs and the probability distribution of a proposition. We regard successive truth values of the proposition as a dependent binary time series whose instantaneous probability of truth is a function of the past behavior of the joint process between the analog inputs and binary output truth values. In this context, we identify the gradient descent learning algorithm using the Kullback-Leibler relative entropy cost function on a perceptron with a Maximum~Partial Likelihood (MPL) estimator of the perceptron model for the probability of a binary event in terms of its covariates. The implications of this result are: (i) The neural network models obtained by relative entropy learning are shown to have the nice large sample (i.e. training set size) characteristics of MPL estimates: consistency and asymptotic normality. (ii) An important and widely used statistical inference technique, logistic regression, can efficiently be implemented on analog perceptrons for time series modeling and prediction.},
	address = {Portland, Oregon},
	booktitle = {The World Congress on Neural Networks},
	pages = {pp. 601-604}
}
@conference {
	title = {Optimal Design of Distributed Sensors and Actuators Made of Smart Materials for Active Vibration Control},
	author = {Zhuang, Yan., Baras, John S.},
	year = {1993},
	month = {05/1993},
	abstract = {We describe a design technique for optimal control in active structural vibration damping using smart materials. The vibration of a cantilever beam is stabilized by using distributed sensors and actuators. We model the beam by the Timoshenko beam model together with the distributed sensors and actuators. A control law using the weighted integration of vibration velocity is incorporated in the closed loop system. We propose a method to find the optimal layout design of the smart material so as to maximize the damping effect. An objective functional is defined based on the vibration energy of the system. The optimal shapes of the sensor and actuator are determined through minimizing the energy functional of the beam over the admissible shape function space subject to certain geometric constraints. An algorithm has been developed to determine the optimal sensor and actuator layout. This method can be generalized to the plate damping problem and more complicated structures as well.},
	address = {Thousand Oaks, CA},
	booktitle = {The 1993 IEEE Regional Conference on Aerospace Control Systems},
	pages = {pp. 65-69},
	organization = { Rockwell Science Center}
}
@conference {
	title = {More About Wavelet Maxima Representations},
	author = {Berman, Zeev., Baras, John S.},
	year = {1993},
	month = {04/1993},
	abstract = {Results regarding reconstruction and modifications of multiscale (wavelet) maxima and zero-crossings representations are presented. The work is based on a general signal description, called an inherently bounded Adaptive Quasi Linear Representation (AQLR), motivated by two important examples: the wavelet zero-crossings representation. The convergence of two new reconstruction algorithms is guaranteed for all inherently bounded AQLR. As a consequence, we describe modifications in the basic multiscale maxima representation. The modifications allow to trade-off between the amount of required information and the reconstruction quality.},
	address = {Minneapolis, Minnesota},
	booktitle = {1993 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2011)},
	pages = {pp. 662-665},
	organization = {Minneapolis Convention Center}
}
@conference {
	title = {Time-Recursive Architectures and Wavelet Transform},
	author = {Frantzeskakis, Emmanuel., Baras, John S., Liu, Ray K J.},
	year = {1993},
	month = {04/1993},
	abstract = {The time-recursive computation has been proved as a particularly useful tool in real-time data compression and in transform domain adaptive filtering, with applications in the areas of audio, radar, sonar and video. Unlike the FFT based ones, the time-recursive architectures require only local communication. Also, they are modular and regular, thus they are very appropriate for VLSI implementation and they allow high degree of parallelism. In this paper, we propose an architectural framework for parallel time-recursive computation. We consider a class of linear operators that consists of the discrete time, time invariant, compactly supported, but otherwise arbitrary kernel functions. We define a shift property of the linear operators and reveal its relation with the time-recursive implementation. We demonstrate the potential of the proposed framework by designing a time-recursive architecture for the Discrete Wavelet Transform.},
	address = {Minneapolis, Minnesota},
	booktitle = {The 1993 International Conference on Acoustics, Speech and Signal Processing},
	pages = {pp. I-445 - I-448}
}
@conference {
	title = {Robustness Study of Free-Text Speaker Identification and Verification},
	author = {Kao, Yu-Hung., Baras, John S., Rajasekaran, P K. },
	year = {1993},
	month = {04/1993},
	abstract = {Usable free-text speaker identification and voice verification systems must exhibit robustness under varying operational conditions. We study the degree of robustness provided by various signal processing techniques [1] [2] [3] by experimenting on a widely used long distance telephone data base [4] [5] [6]. This data base consists of data recorded at two different sites, with data from one site much poorer in quality than the other; further, the recording equipment had been inadvertly changed for the later half of the sessions resulting in a significantly changed environment. Our study identifies the combination of techniques that provide consistent and significant improvements; our results surpass other published results [4] [5] [6] on the same task. Specifically, in the task of identifying 16 speakers, with training data from the recording prior to equipment change and testing on data from a set after the change(the most challenging condition), we obtain a correct identification rate of 87.5\% with an average rank of 1.12; [4] obtains the hitherto best result of 75\% correct identification with an average rank of 1.56: without any robustness processing, the rate was only 12\%. Detailed results on exhaustive experimentation are presented along with appropriate discussions.},
	address = {Minneapolis, Minnesota},
	booktitle = {IEEE International Conference on Acoustics, Speech and Signal Processing},
	pages = {pp. 379-382}
}
@conference {
	title = {Design of the MANDATE MIB},
	author = {Haritsa, Jayant., Ball, Mike., Roussopoulos, Nick., Baras, John S., Datta, Anindya.},
	year = {1993},
	month = {04/1993},
	abstract = {A management information database is the heart of a network management system - it provides the interface between all functions of the network management system, and therefore has to provide sophisticated functionality allied with high performance. In this paper, we introduce the design of MANDATE, a database system that is designed to effectively support the management of large enterprise networks. MANDATE proposes to use special characteristics of network management data and transactions, together with recent advances in database technology, to efficiently derive its functionality.},
	address = {San Francisco, California},
	booktitle = {The 3rd International Symposium on Integrated Network Management},
	pages = {pp. 85-96}
}
@conference {
	title = {Maximum Partial Likelihood Estimation with Perceptrons},
	author = {Sonmez, Kemal M., Baras, John S.},
	year = {1993},
	month = {03/1993},
	abstract = {We show the equivalence of two techniques of time series modeling/prediction; (ii) perceptron learning of probability distribution of the truth value of a proposition from first order stochastic density approximations, (ii) Maximum Partial Likelihood (MPL) estimation of the parameters of a logistic regressive model for binary time series. This result provides large training set characteristics for the approximate Kullback-Leibler relative entropy learning scheme.},
	address = {Baltimore, Maryland},
	booktitle = { The 1993 Conference on Information Sciences and Systems},
	pages = {pp. 812-817},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Convergence of a Neural Network Classifier},
	author = {Baras, John S., Chen, Shihwei.},
	year = {1993},
	month = {03/1993},
	abstract = {In this paper, we consider mixed-media networks with multi-media traffic to find the optimal splitting ratios between satellite network ~and terrestrial network for data and voice traffic dynamically. We constantly monitor the traffic and measure the arrival rate and occupancy of every link. Based on these data, we optimize data traffic delay in a suitable time-frame under the constraints of voice traffic blocking probabilities of voice transmission links being less than specified values, which is up to system{\textquoteright}s design or user{\textquoteright}s requirements. A dynamic routing algorithm is presented.~},
	address = {Baltimore, Maryland},
	pages = {pp. 1-10},
	organization = {John Hopkins University}
}
@conference {
	title = {A New Deterministic Codebook Structure for CELP Speech Coding},
	author = {Kao, Yu-Hung., Baras, John S.},
	year = {1993},
	month = {01/1993},
	abstract = {Low bit rate, high quality speech coding is a vital part in voice telecommunication systems. The introduction of CELP (1984) (Codebook Excited Linear Prediction) speech coding provided a feasible way to compress speech data to 4.8 kbps with high quality, but the formidable computational complexity required for real-time processing has prevented its wide application. Using the new deterministic codebook, we reduce the computational complexity of codebook search, which originally accounted for 2/3 of the computational complexity, to negligible. Based on this reduction, we produce an algorithm with complexity about 5 MIPS. It can be implemented in even inexpensive DSP chips, while maintaining the same high quality. In addition to extremely simple encoding and decoding schemes, this codebook also provides optimal error tolerance and it doesn{\textquoteright}t require codebook storage. We hope that this contribution can finally make CELP speech coding a widely applicable and practical technology.},
	address = {San Antonio, Texas},
	booktitle = {The 1993 IEEE International Symposium on Information Theory},
	pages = {pp. 340}
}
@conference {
	title = {Parameter Identification of Large Spacecraft Systems Based on Frequency Characteristics},
	author = {Augenstein, Donald R., Baras, John S., Fisher, Shalom M.},
	year = {1992},
	month = {12/1992},
	abstract = {In this paper we describe parameter identification for an in-orbit satellite. Actual experimental results are described for the Low Atmospheric Control Experiment (LACE) spacecraft. This is a low earth orbit satellite that was launched into a circular orbit. Its structure consists of a central rigid body or bus with three deployable booms. We accomplished the identification of the structural modes and damping factors of the spacecraft in orbit utilizing the frequency characteristics of the Hankel operator. Frequency domain error bounds and time domain error bounds were considered. The experiment utilized ground based laser illumination and identified three of the lowest vibration modes. The accuracy of the methods was extremely good.},
	address = {Tucson, Arizona},
	booktitle = { The 31st IEEE Conference on Decision and Control},
	pages = {pp. 1696-1701},
	organization = {Westin La Paloma}
}
@conference {
	title = {Optimal Filtering of Digital Binary Images Corrupted by Union/Intersection Noise},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1992},
	month = {12/1992},
	abstract = {We model digital binary image data as realizations of a uniformly bounded discrete random set (or discrete random set, for short), a mathematical object which can be directly defined on a finite lattice. We consider the problem of estimating realizations of discrete random sets distorted by a degradation process which can be described by a union/intersection noise model. We start by providing some theoretical justification of the popularity of certain Morphological filters, namely Morphological openings, closings, unions of openings, and intersections of closings. In particular, we prove that if the signal is {\textquotedblleft}smooth{\textquotedblright}, then these filters are optimal (in the sense of providing the MAP estimate of the signal) under reasonable worst-case statistical scenarios. Then we consider a class of filters which arises quite naturally from the set-theoretic analysis of optimal filters. We call this the class of mask filters. We consider both fixed and adaptive mask filters~and derive explicit formulas for the optimal mask filter under quite general assumptions on the signal and the degradation process.},
	address = {Tucson, Arizona},
	booktitle = { The 31st IEEE Conference on Decision and Control},
	pages = {pp. 3287-3292},
	organization = {Westin La Paloma}
}
@conference {
	title = {An Adaptive Quasi-Linear Representation-A Generalization of the Multiscale Edge Representation},
	author = {Berman, Zeev., Baras, John S.},
	year = {1992},
	month = {12/1992},
	abstract = {The analysis of the discrete multiscale edge representation is considered. A general signal description, called an inherently bounded Adaptive Quasi Linear Representation (AQLR), motivated by two important examples: the wavelet maxima representation and the wavelet zero crossings representation is introduced. This paper addresses the questions of uniqueness, stability, and reconstruction. It is shown, that the dyadic wavelet maxima (zero-crossings) representation is, in general, nonunique. Nevertheless, these representations are always stable. A reconstruction algorithm, based on the minimization of an appropriate cost function, is proposed. The convergence of the algorithm is guaranteed for all inherently bounded AQLR. In the case, of the wavelet transform, this method yields an efficient, parallel algorithm, especially promising in an analog-hardware implementation},
	address = {Tucson, Arizona},
	booktitle = { The 31st IEEE Conference on Decision and Control},
	pages = {pp. 3281-3286},
	organization = {Westin La Paloma}
}
@conference {
	title = {Optimal Routing in Mixed Media Networks with Integrated Voice and Data Traffic},
	author = {Chen, Shihwei., Baras, John S.},
	year = {1992},
	month = {12/1992},
	abstract = {In this paper, we consider a large mixed-media network which consists of a low-delay terrestrial sub-network and a high-bandwidth satellite sub-network. Both voice and data traffic are transmitted and routed through the same network. We show how to route both traffic via ground and/or satellite links by means of static, deterministic procedures. Two common voice/data integrated protocols such as fixed boundary and movable boundary schemes for the satellite channel are investigated, and the performance of both schemes is evaluated. The optimal splitting ratios for voice and data at the SIMPs (Satellite Interface Message Processors) are found using a powerful numerical optimization package (FSQP).},
	address = {Orlando, Florida},
	booktitle = {The Globecom 92},
	pages = {pp. 335-339}
}
@conference {
	title = {Optimal Morphological Filters for Discrete Random Sets under a  Union or Intersection Noise},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1992},
	month = {11/1992},
	abstract = {We consider the problem of optimal binary image restoration under a union or intersection noise model. Union noise is well suited to model random clutter (obscuration), whereas intersection noise is a good model for random sampling. Our approach is random set-theoretic, i.e. digital images are viewed as realizations of a uniformly bounded discrete random set. First we provide statistical proofs of some "folk theorems{\textquotedblright} of Morphological filtering. In particular, we prove that, under some reasonable worst-case statistical scenarios, Morphological openings, closings, unions of openings, and intersections of closings, can be viewed as MAP estimators of the signal based on the noisy observation. Then we propose a "generic{\textquotedblright} procedure for the design of optimal Morphological filters for independent union or intersection noise.},
	address = {Boston, Massachusetts},
	booktitle = {The SPIE Conference on Visual Communication \& Image Processing},
	pages = {pp. 402-413}
}
@conference {
	title = {Distributed Control of a Timoshenko Beam},
	author = {Zhuang, Yan., Baras, John S.},
	year = {1992},
	month = {11/1992},
	abstract = {We consider a flexible beam clamped to a rigid base on one end with the other end free. In order to stabilize the beam vibration, we introduce active damping into the beam with feedback control using distributed actuators and sensors. We apply Tim Oshenko beam theory to model the substructure. Unlike the familiar Euler-Bernoulli beam model, the shear effect and the rotational inertia are included in the modeling of elastic deformation to obtain a more precise beam model. The piezoelectric~theory is briefly reviewed. The piezoelectric ceramic material (PZT) is used to build the distributed actuator. The distributed sensor is made of piezoelectric polymer polyvinylidene fluoride (PVDF). The sensor and actuator are layers which are attached directly to both sides of the beam. Based on the constitutive properties and layer geometry, the models for sensor and actuator are developed. We then embed the static actuator and sensor models into the beam substructure to form the model of the composite beam. We design the feedback controller by Lyapunov direct methods based on the energy functional of the system. It is proved that the derived controller can extract energy from the system and increase system damping. The resulting closed loop system is asymptotically stable. Since this method does not depend on model truncation, we further analyze the combined effect of the distributed controller on the relevant vibration modes. It is possible to suppress the selected modes by choosing the appropriate actuator layout. It is also shown that by properly installing the sensor and determining the sensor shape function,~we can further extract and manipulate the sensor signal for our control need.

~

~},
	address = {San Diego, CA},
	booktitle = {The Third International Conference on Adaptive Structures},
	pages = {pp. 216-227}
}
@conference {
	title = {Stochastic Morphology and Nonlinear Filtering of Digital Images},
	author = {Baras, John S.},
	year = {1992},
	month = {11/1992},
	address = {Quebec, Canada},
	booktitle = {Workshop on Stochastic Control},
	organization = {Centre de Recherches Mathematiques, Universite de Montreal}
}
@conference {
	title = {Robust Free-Text Speaker Identification Over Long Distance Telephone Channels},
	author = {Kao, Yu-Hung., Rajasekaran, P K. , Baras, John S.},
	year = {1992},
	month = {10/1992},
	abstract = {Usable free-text speaker identification and voice verification systems must exhibit robustness under varying Operational conditions. We study the degree of robustness provided by various signal processing techniques [1] [2] [3] by experimenting on a widely used long distance telephone data base [4] [5]~[6]. This data base consists of data recorded at two different sites, with data from one site much poorer in quality than the other; further, the recording equipment had been inadvertently changed for the later half of the sessions resulting in a significantly changed environment. Our study identifies the combination of techniques that provide consistent and significant improvements, our results surpass other published results [4] [5]~[6] on the same task. Specifically, in the task of identifying 16 speakers, with training data from the recording prior to equipment change and testing on data from a set after the change (the most challenging condition), we obtain a correct identification rate of 87.5\% with an average rank of 1.12; [4]~obtains the hitherto best result of 75\% correct identification with an average rank of 1.56; without any robustness processing, the rate was only 12\%. Detailed results on exhaustive experimentation are presented along with appropriate discussions.},
	address = {Piscataway, New Jersey},
	booktitle = { IEEE Workshop on Interactive Voice Technology for Telecommunications Applications},
	pages = {pp. 1-5}
}
@conference {
	title = {Hybrid (Satellite and Terrestrial) Communication Networks:  Object Oriented Generic Tools for Simulation and Management},
	author = {Baras, John S., Charuhas, Thomas.},
	year = {1992},
	month = {10/1992},
	abstract = {We describe a generic object oriented software environment for the simulation and management of hybrid communication networks (satellite and terrestrial) under development at the University of Maryland, as part of the NASA CCDS program. We refer to this environment as a "systems engineering workstation for hybrid networks". It will have the capability to model such networks in a totally object oriented environment and link to network performance evaluation modules. Satellites are treated both as electronic/mechanical systems and as communication nodes. Great flexibility is allowed for defining the various components of the satellite, including its type (i.e. LEO or GEO), on board processing capabilities, bandwidth, multiple access scheme, linkage to terrestrial networks. The satellite link is also treated as an object allowing great flexibility in modeling weather effects, multipath interference and coverage. We show the system{\textquoteright}s flexibility in studying combined adaptive routing and access for voice-data large hybrid networks.},
	address = {San Diego, California},
	booktitle = {1992 IEEE MILCOM Conference},
	pages = {pp. 0553-0559}
}
@conference {
	title = {The Parametric Wavelet Maxima Representation},
	author = {Berman, Zeev., Baras, John S., Berenstein, Carlos A.},
	year = {1992},
	month = {10/1992},
	abstract = {A general signal description, called an inherently bounded Adaptive Quasi Linear Representation (AQLR), motivated by two important examples, namely, the wavelet maxima representation, and the wavelet zero-crossings representation, is introduced. This paper presents a new reconstruction scheme based on the minimization of an appropriate cost function. The convergence of two described algorithms is guaranteed for all inherently bounded AQLR. As a consequence, we describe possible modifications in the basic multiscale maxima representations.},
	address = {Victoria, British Columbia, Canada},
	booktitle = {IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis},
	pages = {pp. 59-62}
}
@conference {
	title = {Evaluation of Producibility and Manufacturability of High Power Surveillance T/R Modules},
	author = {McMahon, M., R. Prasannappa, Baras, John S., Zhang, G., Kebede, Abraham., Mendicino, P.},
	year = {1992},
	month = {09/1992},
	abstract = {This paper describes techniques and an implementation for managing costs and quality of electronics products during design. Emphasis is given to the development of an economic model to estimate the production costs at the assembly level. The unique feature of this system is to bring the experience of a manufacturing engineer, quality engineer, and cost controller into the hands of a designer. Such an early integration of manufacturing knowledge creates a concurrent engineering environment which~improves product quality and reduces cost through careful monitoring of the design phase.},
	address = {Baltimore, Maryland},
	booktitle = {13th International Electronics Manufacturing Technology Symposium},
	pages = {pp. 266-271},
	organization = {Inner Harbor}
}
@conference {
	title = {Uniqueness and Stability of Discrete Zero-Crossings and Maxima Wavelet Representations},
	author = {Berman, Zeev., Baras, John S.},
	year = {1992},
	month = {08/1992},
	abstract = {A general signal description, called an inherently bounded Adaptive Quasi Linear Representation (AQLR), motivated by two important examples, namely the wavelet maxima representation, and the wavelet zero-crossings representation, is introduced. It is shown, that the dyadic wavelet maxima~(zero-crossings) representation is, in general, nonunique. Using the idea of the inherently bounded AQLR, a global BIBO stability is shown. For a special case, where perturbations are limited to the continuous part of the representation, a Lipschitz condition is satisfied.},
	address = {Brussels, Belgium},
	booktitle = {6th European Signal Processing Conference (EUSIPCO)},
	pages = {pp. 913-916}
}
@conference {
	title = {Discrete Random Sets: An Inverse Problem, Plus Tools for the Statistical Inference of the Discrete Boolean Model},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1992},
	month = {07/1992},
	abstract = {We consider digital binary images as a realization~of a bounded discrete random set, a mathematical object which can be defined directly on a finite lattice. In this setting, we show that it is possible to move between two equivalent probabilistic model specifications. We formulate a restricted version of the discrete-case analog of a Boolean random set model, obtain it{\textquoteright}~probability mass function. and employ some methods of Morphological image analysis to derive tools for its statistical inference.},
	address = {San Diego, California},
	booktitle = {SPIE Conference on Image Algebra and Morphological Image Processing III},
	pages = {pp. 32-43}
}
@conference {
	title = {Optimization, Intelligent Control and Complexity},
	author = {Baras, John S.},
	year = {1992},
	month = {06/1992},
	address = {London, UK},
	booktitle = {Systems and Control Themes for the Nineties, A Conference in honor of Professor David Mayne},
	organization = {Imperial College}
}
@conference {
	title = { Parameter Identification of Large Spacecraft Systems Based on Frequency Characteristics},
	author = {Augenstein, Donald R., Baras, John S., Fisher, Shalom M.},
	year = {1992},
	month = {06/1992},
	abstract = {In this paper we describe parameter identification for an in-orbit satellite. Actual experimental results are described for the Low Atmospheric Control Experiment (LACE) spacecraft. This is a low earth orbit satellite that was launched into a circular orbit. Its structure consists of a central rigid body or bus with three deployable booms. The first boom is the gravity gradient boom while the second is the retro-reflector boom. We accomplished the identification of the structural modes and damping factors of the spacecraft in orbit. A systems approach was used to analyze the experiment and present identification techniques utilizing the frequency characteristics of the Hankel operator. Frequency domain error bounds and time domain error bounds were considered.

The experiment was performed on a satellite in conjunction with the Naval Research Laboratory. The experiment utilized ground based laser illumination with Doppler shifted returns and identified three of the lowest vibration modes. The accuracy of the methods was extremely good.},
	address = {Sophia-Antipolis, France},
	booktitle = {The 10th International Conference on Analysis and Optimization of Systems},
	pages = {pp. 624-635}
}
@conference {
	title = {Active Vibration Damping Using Smart Material},
	author = {Baras, John S., Zhuang, Yan.},
	year = {1992},
	month = {06/1992},
	abstract = {We consider the Modeling and active damping of an elastic beam using distributed actuators and sensors. The piezoelectric ceramic material (P7T) is used to build the actuator. The sensor is made of the piezoelectric polymer polyvinylidene fluoride (PVDF). These materials are glued on both side of the beam. For the simple clamped beam, the closed loop controller has been shown to be able to extract energy from the beam. The shape of the actuator and its influence on the closed loop system performance are discussed. It is shown that it is possible to suppress the selected mode by choosing the appropriate actuator layout. It is also shown that by properly installing the sensor and determine the sensor shape we can further extract and manipulate the sensor signal for our control need.},
	address = {Williamsburg, Virginia},
	booktitle = {Workshop on Distributed Parameter Modeling and Control of Flexible Aerospace Systems},
	pages = {pp. 1-14}
}
@conference {
	title = {An Analysis of Discrete Zero-Crossings and Maxima Wavelet Representations},
	author = {Zeev Berman, Baras, John S.},
	year = {1992},
	month = {06/1992},
	address = {Toulouse, France}
}
@conference {
	title = {Free-Text Speaker Identification Over Long Distance Telephone Channel Using Hypothesized Phonetic Segmentation},
	author = {Kao, Yu-Hung., Rajasekaran, P K. },
	year = {1992},
	month = {03/1992},
	abstract = {Experimental investigation of free-text speaker identification method based on long-term statistics is conducted on a widely-used long distance telephone data base (l). On a 26-speaker subset, an average correct identification of 93.3\% is obtained; on the complete 51speaker set, 67.6\% correct identification is obtained. Speaker verification experiments on the data base provided receiver operating characteristics (ROC) comparable to or better than the ones available in open literature.},
	address = {San Francisco, CA},
	booktitle = {1992 International Conference on Acoustics, Speech, and Signal Processing (ICAASP)},
	pages = {pp. 177-180}
}
@conference {
	title = {A Study on Discrete Multiscale Edge Representations},
	author = {Berman, Zeev., Baras, John S.},
	year = {1992},
	month = {03/1992},
	abstract = {The analysis of a discrete multiscale edge representation is considered. A general signal description, called an inherently bounded Adaptive Quasi Linear Representation (AQLR), motivated by two important examples, namely, the wavelet maxima representation, and the wavelet zero-crossings representation, is introduced. This paper addresses the questions of uniqueness, stability, and reconstruction. It is shown, that the dyadic wavelet maxima (zero-crossings) representation is, in general, non unique. Nevertheless, these representations are always stable. Using the idea of the inherently bounded AQLR, two stability results are proven. For a general perturbation, a global BIBO stability is shown. For a special case, where perturbations are limited to the continuous part of the representation, a Lipschitz condition is satisfied. A reconstruction algorithm, based on the minimization of an appropriate cost function, is proposed.},
	address = {Princeton, New Jersey},
	booktitle = {Twenty-Sixth Annual Conference on Information Sciences and Systems},
	pages = {pp. 896-901},
	organization = {Princeton University}
}
@conference {
	title = {Optimal Mask Filtering of Discrete Random Sets under a Union/Intersection Noise Model},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1992},
	month = {03/1992},
	abstract = {We consider the problem of estimating realizations of highly nonstationary Discrete Random Sets, distorted by a degradation process which can be described by a union/intersection model. We start by presenting some important structural results concerning the probabilistic description of Discrete Random Sets defined on a finite lattice. Then we propose a family of filters which can be viewed as lattice operators, and, for each degradation model, derive the optimal filter by means of minimizing a suitable fidelity criterion.},
	address = {Princeton, New Jersey},
	booktitle = {Twenty-Sixth Annual Conference on Information Sciences and Systems},
	pages = {pp. 313-318},
	organization = {Princeton University}
}
@conference {
	title = {Model-Based ATR:  Algorithms Based on Reduced Target Models, Learning and Probing},
	author = {Baras, John S., MacEnany, David C.},
	year = {1992},
	month = {03/1992},
	abstract = {Two new model based ATR algorithms are presented. The algorithms employ economic target models, recent mathematical developments in the extraction and reduction of target silhouettes from noisy images, and on-line probing for clutter reduction and target classification. The target models used employ a small, carefully selected set of characteristic viewpoints and local features. The design of the algorithms are described and their performance evaluated using synthetic FLIR data. The two algorithms are: the Probing Algorithm and the 4-Way Distance Algorithm. Both algorithms have an early phase which is primarily statistical, and a late phase which is primarily geometric, although the two phases are tightly coupled, with frequent revisitation of the image data used to increase decision confidence. In the Probing Algorithm novel on-line probing is performed using stored target geometric models to efficiently implement a generalized maximum likelihood principle. The Probing Algorithm self-adapts to find the most appropriate target location, range and viewpoint geometry and then performs decision-making based on selected maximum likelihood estimates and on-line computed, optimal probing sets. The 4-Way Distance Algorithm performs decision making based on a classification tree logic utilizing matching scores computed on four components of the target silhouette.},
	address = {Ft. Belvoir, Virginia},
	booktitle = {Second ATR Systems and Technology Conference},
	pages = {pp. 277-300}
}
@conference {
	title = {Scale-Space Polygonalization of Target Silhouettes and Applications to Model-Based ATR},
	author = {MacEnany, David C., Baras, John S.},
	year = {1992},
	month = {03/1992},
	abstract = {Economic descriptions of shapes and objects are essential for model based ATR. In addition to object silhouettes, geometric features such as corners and simplified representations such as polygonal approximations can be used to reduce shape description complexity. Here we analyze the polygonal approximation of object silhouette boundaries. Robust polygonalization for ATR requires the construction of polygonal approximations in various scales; namely polygons preserving features of the boundary with varying resolution. In this paper we introduce the notion of scalespace polygonalization. Scale-space polygonalization allows for the generation of polygonal approximations across a range of resolutions and achieve vertex localization which is uniform in scale. The notion of scale or resolution for a polygon involves the distances between its vertices and the magnitude of its vertex angles. Fine scale implies high resolution of the details of boundary contours while coarse scale implies only gross details of boundary contours with a consequent reduction of both computational and descriptive complexity. The polygonalization methods and algorithms presented here are novel in that we control the reduction of the contour complexity by adjusting resolution parameters which have a natural interpretation and achieve vertex localization which is uniform in scale and persistent in scale. These polygonalized boundaries can be used to generate a target fingerprint across a range of scales. Scale-space polygons are important for ATR because they provide a way to reduce the complexity of digitized planar curves consisting of polygons having hundreds of sides to polygons of about a dozen sides, while still capturing the essential features of the model silhouette. This is desirable because shorter polygonal descriptions yield faster correlations and matchings and reduce the overall computational complexity of the ATR problem. We show how scale-space polygonalization can be used to obtain efficient representations of targets, and fast matching algorithms. We also show how scale-space polygons can be used to obtain stable edges from noisy images. We demonstrate these results on examples involving synthetic FLIR data and CAD target models.},
	address = {Ft. Belvoir, Virginia},
	booktitle = {Second ATR Systems and Technology Conference},
	pages = {pp. 223-247}
}
@conference {
	title = {Motion-Compensated Wavelet Transform Coding for Full-Motion Color Video Signals},
	author = {Zhang, Ya-Qin. , Zafar, Sohail., Baras, John S.},
	year = {1991},
	month = {11/1991},
	abstract = {The discrete wavelet transform (DWT) has recently received much attention in the context of image~processing due to its flexibility in representing nonstationary image signals and its ability in ~adapting human visual characteristics. Its relationships to subband coding, Gabor transform, pyramid~structure and other intermediate spatial-frequency representation have been investigated [MALL89][BURT 89][VETT90]. Most of current research in DWT has been concentrated on still imagecoding in the area of data compression. In [BAAZ90], DWT was applied to decompose a sequence~of images and no coding results were reported. It is the purpose of this paper to apply DWT to~compress full motion color TV video signals using inter-frame motion-compensated coding, which,~to the best of our knowledge, has not been researched previously.

The compression scheme we implemented in our work is an interframe hybrid DPCM/DWT scheme~with a new motion compensation method. After motion compensation, the displaced frame difference(DFD) residue video signal is decomposed by wavelet representation and the wavelet pyramid~samples are uniformly quantized in each band. The quantization process takes advantage of human~visual characteristics and coefficients are weighted prior to the quantization. Motion vectors are~noiselessly coded. All quantities are entropy-coded adaptively prior to the transmission. The number~of samples in the wavelet representation is equal to the samples in the original frame as a consequence~of orthogonality of the decomposition.~

Two new block-based motion estimation schemes, namely: intra-frame and inter-frame predictive~motion estimation schemes, are used to find the displacement information prior to the wavelet~decomposition on the displace difference frame. In the proposed intra-frame predictive pattern~searching scheme (PPS), motion information in the neighboring blocks is exploited. This is especially~useful in estimating motion vectors of video signals which contain large homogeneous areas and~translations caused by object moving or camera panning. Therefore, motion vectors for these areas~are highly correlated. The purpose of intra-frame PPS is to take advantage of this correlation and~ hereby reduce the searching area. The proposed inter-frame predictive pattern searching scheme is based on the "inertia" property of moving object. The motion vectors of a block is estimated from~those of previous frames represented by an autoregressive model. The propose intra/inter PPS~Schemes not only significantly reduce the computational complexity of motion estimations, it also~gives more realistic motion vectors.

The proposed motion compensated DWT coding scheme is implemented in our Abekas-60 based~video compression testbed. The Abekas A-60 is basically a digital video recorder which allows a~real-time playback of 25 second recorded CCIR 601 digital video. The Abekas system is interfaced~with a SPARC workstation, where the compression software resides. By software simulation of the~compression/decompression techniques in the SPARC, we can reconstruct video segments to~compare with the original signal via a real-time play back. Therefore, we can evaluate compression performance, quality degradation, computational efficiency of different coding algorithms. The test~sequences "CAR" and "TOPGUN" we use are two full-motion color video sequences in CCIR 601~format with 720 by 480 per frame, 16 bits per pixel in YUV format (or 24 bits in RGB format) and~30 frames/60 fields per second. We measured the first-order entropy of the DFD signal, the entropy~of motion vectors, the reconstructed signal-to-noise ratio at a coding rate ranging from 1Mbps to 3~Mbps. Those results are also compared with the MPEG-like scheme which uses a motion~compensated hybrid DPCM/DCT scheme and is currently being standardized by the CCITT MPEG~committee. The subjective and comparative results suggest that the DWT can be successfully applied~to full-motion video compression and less "blocking effect" is observed compared to the DCT-based~block transform coding with about the same data rate and signal-to-noise ratio.},
	address = {Boston, Massachusetts},
	booktitle = {SPIE-Visual Communications and Image Processing {\textquoteright}91: Sixth in a Series},
	pages = {pp. 301-316}
}
@conference {
	title = {Consistent Estimation of the Order of Hidden Markov Chains},
	author = {Baras, John S., Finesso, Lorenzo.},
	year = {1991},
	month = {09/1991},
	abstract = {The structural parameters of many statistical models can be estimated maximizing a penalized version of the likelihood function. We use this idea to construct strongly consistent estimators of the order of Hidden Markov Chain models. The specification of the penalty term requires precise information on the rate of growth of the maximized likelihood ratio. We find an upper bound to the rate using results from Information Theory. We give sufficient conditions on the penalty term to avoid overestination and underestimation of the order. Examples of penalty terms that~generate strongly consistent estimators are also given.},
	address = {Lawrence, Kansas},
	booktitle = {Stochastic Theory and Adaptive Control Workshop},
	pages = {pp. 26-39},
	organization = {University of Kansas}
}
@conference {
	title = {Two-Dimensional Signal Deconvolution: Design Issues Related to a Novel Multisensor-based Approach},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1991},
	month = {07/1991},
	abstract = {We employ recent results of analysis in several complex variables to come up with a set of compactly supported approximate deconvolution kernels for the reconstruction of a two dimensional signal based on multiple linearly degraded versions of the signal with a family of kernels that satisfy suitable technical conditions. We discuss the question of convergence of the proposed deconvolution kernels, present simulation results that demonstrate the gain in bandwidth, and propose two data parallel grid layouts for the off-line computation of the deconvolution kernels.},
	address = {San Diego, California},
	booktitle = {SPIE 1991 International Symposium on Stochastic and Neural Methods in Signal Processing, Image Processing, and Computer Vision},
	pages = {pp. 356-366}
}
@conference {
	title = {A Bayesian Matching Technique for Detecting Simple Objects in Heavily Noisy Environment},
	author = {Baras, John S., Frantzeskakis, Emmanuel.},
	year = {1991},
	month = {07/1991},
	abstract = {The template matching problem for binary corrupted images with spatially white, binary, symmetric noise is studies. We compare matching based directly on the pixel-value image data as well as data coded by two simple schemes: a modification of the Hadamard~basis and direct coarsening of resolution. Bayesian matching rules based on M-ary~hypothesis are developed. The performance evaluation of these rules is provided,

The paper presents a study of the trade-off between the quantization level and the ability of detecting an object in an image. This trade-off depends on the (external) noise generated at the moment we receive the uncoded image.

The sum-of pixels and the histogram statistics are introduced in order to reduce the computational load inherent in the correlation statistic, with the resulting penalty of a higher probability~of false alarm rate.

In the present work~we demonstrate by examples that it is beneficial for recognition to combine an image coding technique with an algorithm extracting some "basic" information from the image. In other words~coding (for compression) helps recognition. Numerical results illustrate this claim.},
	address = {San Diego, California},
	booktitle = {SPIE 1991 International Symposium on Stochastic and Neural Methods in Signal Processing, Image Processing, and Computer Vision},
	pages = {pp. 341-353}
}
@conference {
	title = {Convergence of Kohonen{\textquoteright}s Learning Vector Quantization},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1991},
	month = {06/1991},
	abstract = {Kohonen{\textquoteright}s Learning Vector Quantization is a nonparametric classification scheme which classifies observations by comparing then to k; templates called Voronoi vectors. The locations of these vectors are determined from past labeled data through a learning algorithm. When learning is complete, the class of a new observation is the same as the class of the closest Voronoi vector. Hence LVQ is similar to nearest neighbors, except that instead of all of the past observations being searched only the k Voronoi vectors are searched.

In this paper, we show that the LVQ~learning algorithm converges to locally asymptotic stable equilibria of an ordinary differential equation. It is shown that the learning algorithm performs stochastic approximation. Convergence of the vectors is guaranteed under the appropriate conditions on the underlying statistics of the classification problem. We also present a modification to the learning algorithm which results in more robust convergence.},
	address = {San Diego, California},
	booktitle = {The 1990 International Joint Conference on Neural Networks (IJCNN)},
	pages = { pp. 17-20}
}
@conference {
	title = {Real Time Architectures for the Zakai Equation and Applications},
	author = {Baras, John S.},
	year = {1991},
	month = {06/1991},
	abstract = {We examine in detail real-time architectures for the sequential detection and/or estimation problems for diffusion type signals. We demonstrate the fundamental role played by Zaki equation in defining candidate architectures. For scalar and two dimensional state models an architecture based on systolic arrays is derived. For higher dimensional implementation~of the Multigrid algorithm is derived. Properties of the architectures and practical hardware implementation results are also reported.},
	booktitle = {Conference honoring Professor Moshe Zakai on his 60th Birthday},
	pages = {pp. 15-38}
}
@conference {
	title = {Predictive Block-Matching Motion Estimation Schemes for Video Compression -- Part II: Inter-frame Prediction of Motion Vectors},
	author = {Zhang, Ya-Qin. , Zafar, Sohail., Baras, John S.},
	year = {1991},
	month = {04/1991},
	abstract = {A new predictive block-matching motion estimation scheme is proposed in this paper for efficient video codec design. The proposed Scheme is based on the "inertia" effect of natural video scenes and takes advantage of the motion vectors obtained in the previous frames. Not only motion searching time and overhead are significantly reduced, the proposed scheme also provides realistic motion tendency, which is very useful for frame skipping/interpolation techniques. These advantages are also demonstrated by some experimental results obtained on Abekas video system.},
	address = {Williamsburg, Virginia},
	booktitle = {The IEEE Southeastcon {\textquoteright}91 Conference},
	pages = {pp. 1093-1095}
}
@conference {
	title = {Predictive Block-Matching Motion Estimation Schemes for Video Compression -- Part I:  Inter-Block Prediction},
	author = {Zafar, Sohail., Zhang, Ya-Qin. , Baras, John S.},
	year = {1991},
	month = {04/1991},
	abstract = {A new motion estimation/compensation~scheme for TV coding is proposed in this paper. This~scheme is based on prediction of inter-block motion information using minimum absolute difference block matching and hence substantially increases the searching and computation efficiency. A comparison is also made with the "optimal" full motion searching scheme for a standard test sequence.},
	address = {Williamsburg, Virginia},
	booktitle = {The IEEE Southeastcon {\textquoteright}91 Conference},
	pages = {pp. 1088-1092}
}
@conference {
	title = {Two-Dimensional Signal Deconvolution Using Multiple Sensors},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1991},
	month = {03/1991},
	abstract = {We consider the two dimensional Analytic Bezout Equation (ABE) and investigate the properties of a particular solution, based on certain conditions imposed on the convolution kernels. We propose the use of approximate deconvolution kernels, prove compactness of their support, and discuss various design problems pertaining to the question of convergence of the proposed deconvolution kernels. We point out the fact that these approximate deconvolution kernels exhibit a strong asymmetry in the FT domain, and propose solutions to this problem. Simulation results are presented in order to demonstrate the gain in bandwidth, the asymmetry of the FT of the overall system, and the effectiveness of the proposed solutions to compensate for this asymmetry.},
	address = {Baltimore, MD},
	booktitle = {The 1991 Conference on Information Sciences and Systems},
	pages = {pp. 594-599},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Convergence of a Neural Network Classifier},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1990},
	month = {12/1990},
	abstract = {In this paper, we show that the LVQ learning algorithm converges to locally asymptotic stable equilibria of an ordinary differential equation. We show that the learning algorithm performs stochastic approximation. Convergence of the Voronoi vectors is guaranteed under the appropriate conditions on the underlying statistics of the classification problem. We also present a modification to the learning algorithm which we argue results in convergence of the LVQ~for a larger set of initial conditions. Finally, we show that LVQ~is a general histogram classifier and that its risk converges to the Bayesian optimal risk as the appropriate parameters go to infinity with the number~of past observations.},
	address = {Honolulu, Hawaii},
	booktitle = {The 29th Conference on Decision and Control (CDC)},
	pages = {pp. 1735-1740}
}
@conference {
	title = {Real-Time Control for a Zero Gravity Robotic End Effector},
	author = {Teolis, Carole A., Baras, John S.},
	year = {1990},
	month = {12/1990},
	abstract = {The ability to easily manipulate objects in a zero gravity environment will play a key role in future space activities. Emphasis will be placed on robotic manipulation. This will serve to increase astronaut safety and utility in addition to several other benefits. It is the aim of this research to develop control laws for the zero gravity robotic end effector designed by engineers at NASA Goddard. A hybrid force/position controller will be used. Sensory data available to the controller are obtained from an array of strain gauges and a linear potentiometer. Applying well known optimal control theoretic principles, the control which minimizes the transition time between positions is obtained. A robust force control scheme is developed which allows the desired holding force to be achieved smoothly without oscillation. In addition, an algorithm is found to determine contact force and contact location.},
	address = {Honolulu, Hawaii},
	booktitle = {The 29th Conference on Decision and Control (CDC)},
	pages = {pp. 3138-3142}
}
@conference {
	title = {Fast Error-Free Algorithms for Polynomial Matrix Computations},
	author = {Baras, John S., MacEnany, David C., Munach, Robert Lawrence.},
	year = {1990},
	month = {12/1990},
	abstract = {Matrices of polynomials over rings and fields provide a unifying framework for many control system design problems. These include dynamic compensator design, infinite dimensional systems, controllers for nonlinear systems, and even controllers for discrete events stems. An important obstacle for utilizing these powerful mathematical tools in practical applications has been the non-availability of accurate and efficient algorithms to carry through the precise error-free computations required by these algebraic methods. In this paper we develop highly efficient, error-free algorithms, for most of the important computations needed in near systems over fields or rings. We show that the structure of the underlying rings and modules is critical in designing such algorithms.},
	address = {Honolulu, Hawaii},
	booktitle = {The 29th Conference on Decision and Control (CDC)},
	pages = {pp. 941-946}
}
@conference {
	title = {Bayesian Sequential Hypothesis Testing},
	author = {Baras, John S., MacEnany, David C.},
	year = {1990},
	month = {08/1990},
	abstract = {We consider the Bayesian sequential detection problem for general observation processes with a continuous time parameter. Primary emphasis is placed on first exit policies and their generic optimality. A new geometric formulation and solution to the existence and uniqueness of the optimal first exit policy will be given as well as an explicit constructive algorithm for its computation. We will apply these resuits to the problem of Bayesian sequential detection for diffusion-type observations although our methods and results generalize to problems of optimal stopping and decision for partially observed Markov chains where the observation processes are of the diffusion or point process type. These results will appear elsewhere.},
	address = {Tallin, USSR},
	booktitle = {The 11th IFAC World Congress},
	pages = {pp. 227-232}
}
@conference {
	title = {Convergence of the Vectors in Kohonen{\textquoteright}s Learning Vector Quantization},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1990},
	month = {07/1990},
	abstract = {Kohonen{\textquoteright}s Learning Vector Quantization is a nonparametric classification scheme which classifies observations by comparing them to k templates called Voronoi vectors. The locations of these vectors are determined from past labeled data through a learning algorithm. When learning is complete, the class of a new observation is the same as the class of the closest Voronoi vector. Hence LVQ is similar to nearest neighbors, except that instead of all of the past observations being searched only the k Voronoi vectors are searched.

In this paper, we show that the LVQ learning algorithm converges to asymptotically stable zeros of an ordinary differential eq{\"u}ation. It is shown that the learning algorithm performs stochastic approximation. Convergence of the vectors is guaranteed under the appropriate conditions on the underlying statistics of the classification problem. We also~present a modification to the learning algorithm which results in more robust convergence.},
	address = {Paris, France},
	booktitle = {The  1990 International Conference on Neural Networks},
	pages = {pp. 1028-1031}
}
@conference {
	title = {Nonlinear Filtering Asymptotics, Large Deviations and Observers for Nonlinear Systems},
	author = {Baras, John S., James, Matthew R.},
	year = {1990},
	month = {04/1990},
	address = {Santa Barbara, CA},
	booktitle = {NSF-UC-NASA Workshop on Nonlinear Control},
	pages = {pp. 29-30},
	organization = {UCSB}
}
@conference {
	title = {Efficient Computer Algebra Algorithms for Polynomial Matrices in Control Design},
	author = {Baras, John S., MacEnany, David C., Munach, Robert Lawrence.},
	year = {1989},
	month = {08/1989},
	abstract = {The theory of polynomial matrices plays a key role in the design and analysis of multi-input multi-output control and communications systems using frequency domain methods. Examples include coprime factorizations of transfer functions, canonical realizations from matrix fraction descriptions, and the transfer function design of feedback compensators. Typically, such problems abstract in a natural way to the need to solve systems of Diophantine equations (the so-called generalized Bezout equations) or systems of linear equations over polynomials. These and other problems involving polynomial matrices can in turn be reduced to polynomial matrix triangularization procedures, a result which is not surprising given the importance of matrix triangularization techniques in numerical linear algebra. - There, we deal with matrices with entries from a field and Gaussian elimination plays a fundamental role in understanding the triangularization process. In the case of polynomial matrices we are dealing with matrices with entries from a ring for which Gaussian elimination is not defined and triangularization is accomplished by what is quite properly~called Euclidean elimination.

~Unfortunately, the numerical stability and sensitivity issues which accompany floatingpoint approaches to Euclidean elimination are not very well understood at present. In~this paper we present new algorithms which circumvent entirely such numerical issues through the use of exact, symbolic methods in computer algebra. The use of such error-free algorithms guarantees that the results are accurate to within the precision of the model data-the best that can be hoped. Care must be taken in the design of such algorithms due to the phenomenon of intermediate epression swell, the price paid for freedom from roundoff error. The emphasis will be placed on efficient algorithms to compute exact Hermite forms for polynomial matrices because this triangularization procedure is central to a large variety of algorithms important in the design of control and communication systems. Moreover, the triangular Hermite form is defined for any matrix with entries from a principal ideal ring and such matrices arise in many practical problems in communications and control, such as the design of convolutional coders and the analysis of quantization effects in linear systems. Due to their symbolic nature, our algorithms apply equally well to such problems since the particular ring involved in a problem can itself be considered~as program input data.},
	address = {Oxnard, California},
	booktitle = {The 3rd Annual Conference on Aerospace Computational Control},
	pages = {pp. 292}
}
@conference {
	title = {Complex Variable Methods in the Modeling and Control of Distributed Parameter Systems},
	author = {Baras, John S.},
	year = {1989},
	month = {06/1989},
	address = {Amsterdam, Netherlands},
	booktitle = {Book of Abstracts on the International Symposium on the Mathematical Theory of Networks and Systems (MTNS-89)},
	pages = {pp. 59}
}
@conference {
	title = {Fast Algorithms for the Triangularization of Polynomial Matrices},
	author = {Baras, John S., MacEnany, David C.},
	year = {1989},
	month = {05/1989},
	abstract = {The theory of polynomial matrices plays a key role in the design and analysis of multi-input-multi-output control systems. More generally, matrices with entries from various principal ideal rings arise in many practical problems in communications and control, such as the design of convolutional coders and the analysis of computational aspects which accompany such matrices are not widely appreciated at present. Indeed, one popularly held belief is that polynomial matrix problems are merely "big" linear algebra problems, but are otherwise essentially straightforward from a numerical standpoint. However, time and again, when confronted by real-world data, the best algorithms of linear algebra fail miserably despite meticulous program design and use of multiple precision floating-point arithmetic. We will describe the nature of this unexpectedly bad behavior and present new algorithms which circumvent it entirely through the use of exact, symbolic methods in computer algebra. Emphasis will be placed on efficient algorithms to compute exact Hermite forms for polynomial matrices because this triangularization procedure is central to a large variety of algorithms important in the design of control and communication systems},
	address = {San Francisco, California},
	booktitle = {The SIAM Conference on Control in the 90{\textquoteright}s: Achievements, Opportunities, and Challenges},
	pages = {pp. 301}
}
@conference {
	title = {Multi-grid Algorithms in Stochastic Estimation and Control},
	author = {Baras, John S.},
	year = {1989},
	month = {05/1989},
	address = {San Francisco, California},
	booktitle = {minisymposium on "Stochastic Dynamic Optimization: Part 1 of 2", at the SIAM Conference on Control in the 90{\textquoteright}s: Achievements, Opportunities, and Challenges}
}
@conference {
	title = {Sensor Scheduling Problems},
	author = {Baras, John S., Bensoussan, Alain.},
	year = {1988},
	month = {12/1988},
	abstract = {We consider the nonlinear filtering problem of a vector difussion process, when several noisy vector observations with possibly different dimension of their range space are available. At each time any number of these observations~(or sensors) can be utilized in the signal processing performed by the nonlinear filter. The problem considered is the optimal selection of a schedule of these sensors from the available set, so as to optimally estimate a function of the state at the final time. Optimality is measured by a combined performance measure that allocates penalties for~errors in estimation, for switching between sensor schedules and for running a sensor. The solution is obtained in the form of a system of quasi-variational inequalities in the space of solutions of certain Zakai equations.},
	address = {Austin, Texas},
	booktitle = {27th IEEE Conference on Decision and Control},
	pages = {pp. 2342-2345}
}
@conference {
	title = {Nonlinear Filtering Asymptotics, Large Deviations and Observers for Nonlinear Systems},
	author = {Baras, John S., James, Matthew R.},
	year = {1988},
	month = {11/1988},
	abstract = {We present a methodology for the construction of the dynamic observers for nonlinear systems. The basic methodology used is to construct these observers as limits of nonlinear filters when certain noise parameters tend to zero. We, therefore, make contact with some interesting results on large derivations~of filtered diffusion processes. Some examples illustrate the results. ~},
	address = {Osaka, Japan},
	booktitle = {20th ISCIE Symposium on Stochastic Systems Theory and its Applications},
	pages = {pp. 1-12}
}
@conference {
	title = {Symbolic and Numeric Real-Time Signal Processing},
	author = {Baras, John S.},
	year = {1988},
	month = {08/1988},
	abstract = {We consider real-time sequential detection and estimation problems for non-gaussian signal and noise models. We develop optimal algorithms and several architectures for realtime implementation based on numerical algorithms, including asynchronous implementations of multigrid algorithms. These implementations are of high complexity, costly and cannot easily accommodate model variability. We then propose and analyze a different class of algorithms, which are symbolic, of the neural network type. The preliminary results presented here demonstrate that these algorithms have remarkably lower complexity and cost, work well under model variability and their performance is nearly optimal. We also discuss how these type of algorithms are incorporated in the DELPHI system for integrated design of signal processing systems.},
	address = {San Diego, California},
	booktitle = {SPIE{\textquoteright}s 32nd Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, in Real Time Signal Processing XI},
	pages = {pp. 112-121}
}
@conference {
	title = {The Conditional Adjoint Process},
	author = {Baras, John S., Elliott, Robert J., Kohlmann, Michael.},
	year = {1988},
	month = {06/1988},
	abstract = {The adjoint process and minimum principle for a partially observed diffusion can be obtained by differentiating the statement that a control u{\textquoteright} is optimal. Using stochastic flows the variation in the cost resulting from a change in an optimal control can be computed explicitly. The technical difficulty is to justify the differentiation.},
	address = {Antibes, France},
	booktitle = {The 8th International Conference on Analysis and Optimization of Systems},
	pages = {pp. 654-662},
	organization = {INRIA}
}
@conference {
	title = {An Observer Design for Nonlinear Control Systems},
	author = {James, Matthew R., Baras, John S.},
	year = {1988},
	month = {06/1988},
	abstract = {We present an observer design for systems with controlled nonlinear dynamics and nonlinear observation. The design is a development of earlier work, which was motivated by nonlinear filtering asymptotics. The basic design requires that the initial conditions belong to a bounded region determined by the data and design parameters. However, for a certain class of systems, no such a priori knowledge is required. To illustrate the utility of our design, several examples are given.},
	address = {Antibes, France},
	booktitle = {The 8th International Conference on Analysis and Optimization of Systems},
	pages = {pp. 170-180},
	organization = {INRIA}
}
@conference {
	title = {Sequential Testing on the Rate of a Counting Process},
	author = {Baras, John S., MacEnany, David C.},
	year = {1987},
	month = {12/1987},
	abstract = {In this paper, optimality results are given for the problems of Bayesian and Wald sequential (simple, binary) hypothesis testing on the rate of a counting process. An explicit formula is given for the Bayes risk, and the system to solve for the exact optimal thresholds is also given.},
	address = {Los Angeles, California},
	booktitle = {The 26th IEEE Conference on Decision and Control},
	pages = {pp. 1592-1593}
}
@conference {
	title = {Order Determination for Functions of Finite Markov Chains},
	author = {Finesso, Lorenzo., Baras, John S.},
	year = {1987},
	month = {12/1987},
	address = {Los Angeles, California},
	booktitle = {The 26th IEEE Conference on Decision and Control},
	pages = {pp. 1881-1882}
}
@conference {
	title = {Nonlinear Filtering and Large Deviations},
	author = {James, Matthew R., Baras, John S.},
	year = {1987},
	month = {12/1987},
	abstract = {We consider the nonlinear filtering problem dx~= f(x)dt + (~∈~)dw, dy = h(x)dt + (~∈~)^1/2 dv, and obtain lim ~∈~-\&gt;0 log q^t (x,t) = -W (x, t) for unnormalised conditional densities q{\textquoteright}(x, t) using PDE methods. Here, W(x,t) is the value function for a deterministic optimal control problem arising in Mortensen{\textquoteright}s deterministic estimation, and is the unique viscosity solution of a Hamilton-Jacobi-Bellman equation.},
	address = {Los Angeles, California},
	booktitle = {The 26th IEEE Conference on Decision and Control},
	pages = {pp. 1588-1589}
}
@conference {
	title = {Real Time Sequential Detection for Diffusion Signals},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1987},
	month = {12/1987},
	abstract = {We present the sequential detection problem for diffusion type signals in both the fixed probability of error and the Bayesian formulations. The optimal strategy in both cases is a threshold policy with explicit{\l}y computable thresholds. We provide numerical schemes for approximating the relevant likelihood ratio and~provide an architecture for real-time signal processing.},
	address = {Los Angeles, California},
	booktitle = {The 26th IEEE Conference on Decision and Control},
	pages = {pp. 1153-1157}
}
@conference {
	title = {Distributed Asynchronous Detection: General Models},
	author = {Baras, John S.},
	year = {1987},
	month = {12/1987},
	abstract = {We introduce axiomatically, new non-commutative probability models for the data in distributed detection asynchronous schemes. We completely characterize mathematically these models and their representation. They represent extensions of models for communicating asynchronous processes. We provide a general theorem characterizing the representation of data collected by a distributed asynchronous detection scheme. We discuss how this~model can be used to obtain performance bounds.},
	address = {Los Angeles, California},
	booktitle = {The 26th IEEE Conference on Decision and Control},
	pages = {pp. 1832-1835}
}
@conference {
	title = {Robustness Issues in Boundary Feedback of Flexible Structures},
	author = {Bennett, William H., Kwatny, H G., Baras, John S.},
	year = {1987},
	month = {09/1987},
	abstract = {Transfer function models for basic structural elements with boundary control reveal certain inherent properties relevant to questions of control system realization, design, and analysis of robustness. The transfer functions involved are not strictly proper, may be nonminimum phase (except for the special case of colocated actuation and sensing), and often have large number of poles on the imaginary axis.

In this paper we consider these basic questions in terms of modeling and control system design for robustness. We investigate the application of algebraic methods for computing stabilizing control based on certain exact, irrational transfer functions. We consider boundary control of the wave equation and suggest extension of the method to more general problems. Special attention is given to implementation issues associated with a class of infinite dimensional control laws of the type described by Baras.},
	address = {Minneapolis, Minnesota},
	booktitle = {The 1987 American Control Conference},
	pages = {pp. 1307-1313}
}
@conference {
	title = {The DELPHI System:  A System Level Tool for Integrated Design of Real-Time Signal Processors},
	author = {Baras, John S., Ebrahimi, Fariborz., Israel, Bruce., LaVigna, Anthony., MacEnany, David C.},
	year = {1987},
	month = {08/1987},
	address = {San Diego, CA},
	booktitle = {SPIE{\textquoteright}s 31st Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, in Real Time Signal Processing X},
	pages = {pp. 10-14}
}
@conference {
	title = {Architectures for Real-Time Sequential Detection and Estimation},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1987},
	month = {08/1987},
	abstract = {We present the sequential detection for diffusion type signals both in the fixed probability of error formulation and in the Bayesian formulation. The optimal strategy in both cases is a threshold policy with explicitly computable thresholds. We provide numerical schemes for approximating the revelant likelihood ratio and provide an architecture for real time signal processing.},
	address = {San Diego, CA},
	booktitle = {SPIE{\textquoteright}s 31st Annual International Technical Symposium on Optical and Optoelectronic Applied Science and Engineering, in Real Time Signal Processing X},
	pages = {pp. 100-105}
}
@article {
	title = {Dynamic Observers as Asymptotic Limits of Recursive Filters: Special Cases},
	author = {Baras, John S., Bensoussan, Alain., James, Matthew R.},
	year = {1988},
	month = {10/1988},
	abstract = {A method for constructing observers for dynamical systems as asymptotic limits of filters is described. The program is carried out in detail for linear systems, and in addition~an observer is obtained for a class of systems with nonlinear dynamics and linear observations. The method is motivated by some large deviation results of Hijab for certain conditional measures.},
	pages = {pp. 1147-1158},
	volume = {Vol. 48},
	number = {No.  5},
	journal = {SIAM Jounal on Applied Mathematics}
}
@conference {
	title = {Distributed Asynchronous Systems: State Concepts Revisited},
	author = {Baras, John S.},
	year = {1987},
	month = {06/1987},
	address = {Phoenix, Arizona},
	booktitle = {The 1987 International Symposium on Mathematical Theory of Networks and Systems}
}
@conference {
	title = {Architectures for Real-Time Signal Processing},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1987},
	month = {06/1987},
	abstract = {We present the sequential detection for diffusion type signals both in fixed probability of error formulation and bayesian formulation. The optimal strategy in both cases is a threshold policy with explicitly computable thresholds. We provide numerical schemes for approximating the revelant likelihood ratio and provide an architectural for real time signal processing.},
	address = {Phoenix, Arizona},
	booktitle = {The 1987 International Symposium on Mathematical Theory of Networks and Systems},
	pages = {100-105}
}
@conference {
	title = {Dynamic Observers as Asymptotic Limits of Recursive Filters: Special Cases},
	author = {Baras, John S., Bensoussan, Alain., James, M R.},
	year = {1987},
	month = {06/1987},
	abstract = {A method for constructing observers for dynamical systems as asymptotic~limits of filters is described. The program is carried out in detail for linear~systems, and in addition an observer is obtained for a class of systems with~nonlinear dynamics and linear observations. The method is motivated by~some large deviation results of Hijab for certain conditional measures.},
	address = {Phoenix, Arizona},
	booktitle = {The 1987 International Symposium on Mathematical Theory of Networks and Systems},
	pages = {pp. 1-31}
}
@conference {
	title = {Future Directions in Control Systems Research},
	author = {Baras, John S.},
	year = {1986},
	month = {12/1986},
	address = {Athens, Greece},
	booktitle = {25th IEEE Conference on Decision and Control}
}
@conference {
	title = {The Systems Research Center:  Creating the Design Tools for the Systems of Tomorrow},
	author = {Baras, John S.},
	year = {1986},
	month = {11/1986},
	address = {Albuquerque, New Mexico},
	booktitle = {the International Symposium on Robot Manipulators}
}
@conference {
	title = {A Continuous-Time Distributed Version of Wald{\textquoteright}s Sequential Hypothesis Testing Problem},
	author = {Makowski, Armand M., LaVigna, Anthony., Baras, John S.},
	year = {1986},
	month = {10/1986},
	address = {Ann Arbor, MI},
	booktitle = {The 1986 IEEE International Symposium on Information Theory},
	pages = {pp. 533-543}
}
@conference {
	title = {Control Engineering: Challenges and Opportunities},
	author = {Baras, John S.},
	year = {1986},
	month = {09/1986},
	address = {Arlington, Virginia},
	booktitle = {1986 Computer Aided Control Systems Design Symposium}
}
@techreport {
	title = {Systems Research Center: The First Year},
	author = {Baras, John S.},
	year = {1986},
	month = {06/1986}
}
@conference {
	title = {A Continuous-Time Distributed Version of Wald{\textquoteright}s Sequential Hypothesis Testing Problem},
	author = {LaVigna, Anthony., Makowski, Armand M., Baras, John S.},
	year = {1986},
	month = {06/1986},
	address = {Antibes, France},
	booktitle = {The Seventh International Conference on Analysis and Optimization of Systems},
	pages = {pp. 533-543},
	organization = {INRIA}
}
@conference {
	title = {Architectures for Real-Time Sequential Detection and Estimation},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1986},
	month = {06/1986},
	abstract = {We present the sequential detection for diffusion type signals in both the fixed probability of error and the Bayesian formulation. The optimal strategy in both cases is a threshold policy with explicit{\l}y computable thresholds. We provide numerical schemes for approximating the relevant likelihood ratio and provide an architecture for real-time signal processing.},
	address = {Minneapolis, Minnesota},
	booktitle = {The Institute for Mathematics and Its Applications Workshop on Stochastic Differential Equations and Their Applications},
	pages = {pp. 100-105}
}
@conference {
	title = {An Impulse Control Problem for a Stochastic PDE Arising in Nonlinear Filtering},
	author = {Baras, John S., Bensoussan, Alain.},
	year = {1985},
	month = {12/1985},
	abstract = {We consider the nonlinear filtering problem of a vector diffusion process, when several noisy vector observations with possibly different dimension of their range space are available. At each time any number of these observations (or sensors) can be utilized in the signal processing performed by the nonlinear filter. The problem considered is the optimal selection of a schedule of these sensors from the available set, so as to optimally estimate a function of the state at the final time. Optimality is measured by a combined performance measure that allocates penalties for errors in estimation, switching between sensor schedules and for running a sensor. The solution is obtained in the form of a system of quasi-variational inequalities in the space of solutions of certain Zakai equations.},
	address = {Ft. Lauderdale, Florida},
	booktitle = {The 24th IEEE Conference on Decision and Control},
	pages = {pp. 1184-1187}
}
@conference {
	title = {A New Geometric Stability Margin for Feedback Systems},
	author = {Bennett, William H., Baras, John S.},
	year = {1985},
	month = {12/1985},
	abstract = {This paper provides a new geometric concept for a stability margin for feedback control systems which is applicable for any number of inputs and outputs. The measure of stability margin employed has the advantage over standard measures of exposing certain additional internal stability properties of a feedback configuration employing dynamic compensation.

The stability margin is based on the essential topological features of an abstract Nyquist criterion proposed by Brockett and Byrnes. This abstract Nyquist criterion for multivariable systems involves the topology of intersections between certain pairs of subspaces of the direct sum of the system inputs and outputs. The measures employed here are derived from the idea of principal angles between a pair of subspaces.},
	address = {Ft. Lauderdale, Florida},
	booktitle = {The 24th IEEE Conference on Decision and Control},
	pages = {pp. 519-526}
}
@conference {
	title = {Decomposition and Decentralized Control System Design: A Review of Frequency Domain Methods},
	author = {Bennett, William H., Baras, John S.},
	year = {1985},
	month = {12/1985},
	abstract = {We provide a short review of the literature on design of decentralized control based on weak coupling measures for transfer function models. The notion of diagonal dominance for transfer functions has been suggested as a measure of weak coupling for system decomposition. Various generalizations of this notion for partitioned transfer function matrices are discussed as they pertain to design of decentralized control.

Such weak coupling techniques permit a decentralized design procedure based on an approximate decoupled model. The accuracy of these decoupled approximations for control design is highlighted.},
	address = {Ft. Lauderdale, Florida},
	booktitle = {The 24th IEEE Conference on Decision and Control},
	pages = {pp. 1828-1835}
}
@conference {
	title = {Optimization-Based Direct Frequency Domain Design of Controllers for Linear Distributed Systems},
	author = {Baras, John S.},
	year = {1985},
	month = {06/1985},
	abstract = {A CAD methodology is developed for the design of controllers~for linear distributed systems incorporating the following key~components: (i) Transfer function models of distributed systems~and their approximations; (ii) Recent frequency domain design~methodology for multi-variable control systems; (iii) Interactive~optimization packages (DELIGHT) in the search for feasible designs~satisfying practical engineering specifications. Primarily~specifications on the shape of the frequency response and of the~unit step response will be considered. The application of the method for large space structures is explained via simple examples~including beams and plates.},
	address = {Capri, Italy,},
	booktitle = {The Fifth IFAC Workshop on Control Applications of Nonlinear Programming  and Optimization},
	pages = {pp. 1-17}
}
@conference {
	title = {Expert Systems and VLSI Architectures for Non-Gaussian Detection and Nonlinear Filtering},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1985},
	month = {06/1985},
	address = {Bonn, West Germany},
	booktitle = {The 3rd Bad Honnef Conference on Stochastic Systems}
}
@conference {
	title = {Stability, Parameter Estimation and Adaptive Control for Discrete-Time Competing Queues},
	author = {Baras, John S., Dorsey, Arthur J., Makowski, Armand M.},
	year = {1984},
	month = {12/1984},
	abstract = {In this paper, several discrete-time queues compete~at the beginning of each time slot for the attention of a single server with infinite capacity. The service requirements are geometric with queue-dependent parameters, independent from customer to customer and independent from the arrivals. The stability of such systems is characterized under the action of an arbitrary , not necessarily Markovian, service allocation policy. Maximum likelihood estimates are obtained in explicit form for the service rates and their strong consistency is established.The results are then applied to the problem of adaptively controlling such systems when the service rates are unknown, under the long-run average performance criterion with instantaneous cost linear in the queue sizes.},
	address = {Las Vegas, Nevada},
	booktitle = {The 23rd IEEE Conference on Decision and Control},
	pages = {pp. 1149-1157}
}
@conference {
	title = {DELPHI: A CAD System for Integrated Design of Non-Gaussian Signal Processors},
	author = {Baras, John S., LaVigna, Anthony.},
	year = {1984},
	month = {12/1984},
	address = {Rome, Italy},
	booktitle = {The IFIP Conference on Recent Advances in Stochastic Estimation and Control}
}
@conference {
	title = {Complex Variables and Infinite Dimensional Linear Systems},
	author = {Baras, John S.},
	year = {1984},
	month = {12/1984},
	abstract = {Complex function algebras play a fundamental role in the analysis and synthesis of the linear infinite dimensional systems. In this talk, we present concrete applications of the complex variable methods to such problems as : stabilization, parametrization of stable controllers, spectral factorization, controller design. The mathematical topics discussed include : Corona theorems, algebraic functions, Hoo~ theory.},
	address = {Ontario, Canada},
	booktitle = {Canadian Mathematical Society, Annual Winter Meeting}
}
@conference {
	title = {Simultaneous Detection and Estimation for Diffusion Process Signals},
	author = {Baras, John S.},
	year = {1984},
	month = {07/1984},
	abstract = {We consider the problem of simultaneous detection and estimation when the signals corresponding to the M different hypotheses can be modelled as outputs of M distinct stochastic dynamical systems of the Ito type. Under very mild assumptions on the models and on the cost structure we show that there exist a set of sufficient statistics for the simultaneous detection-estimation problem that can be computed recursively by linear equations. Furthermore we show that the structure of the detector and estimator is completely determined by the cost structure. The methodology used employes recent advances in nonlinear filtering and stochastic control of partially observed stochastic systems of the Ito type. Specific examples and applications in radar tracking and discrimination problems are discussed.},
	address = {Budapest, Hungary},
	booktitle = {The 9th IFAC World Congress},
	pages = {pp. 59-64}
}
@conference {
	title = {Special Purpose VLSI Array Processors for the Zakai Equation and Applications},
	author = {Baras, John S.},
	year = {1984},
	month = {07/1984},
	address = {Budapest, Hungary},
	booktitle = {The 9th IFAC World Congress},
	pages = {pp. 40-42}
}
@conference {
	title = {Simultaneous Detection and Estimation for Diffusion Process Signals},
	author = {Baras, John S.},
	year = {1984},
	month = {06/1984},
	abstract = {We consider the problem of simultaneous detection and estimation when the signals corresponding to the M different hypotheses can be modelled as outputs of M distinct stochastic dynamical systems of the Ito type. Under very mild assumptions on the models and on the cost structure we show that there exist a set of sufficient statistics for the simultaneous detection-estimation problem that can be computed recursively by linear equations. Furthermore we show that the structure of the detector and estimator is completely determined by the cost structure. The methodology used employes recent advances in nonlinear filtering and stochastic control of partially observed stochastic systems of the Ito type. Specific examples and applications in radar tracking and discrimination problems are discussed.},
	address = {Nice, France},
	booktitle = {6th International Conference on Analysis and Optimization of Systems },
	pages = {pp. 471-484},
	organization = {INRIA}
}
@conference {
	title = {Discrete-Time Competing Queues with Geometric Service Requirements:  Stability, Parameter Estimation and Adaptive Control},
	author = {Baras, John S., Dorsey, Arthur J., Makowski, Armand M.},
	year = {1984},
	month = {05/1984},
	abstract = {In this paper, several discrete-time queues compete at the beginning of each time slot for the attention of a single server with infinite capacity. The service requirements are geometric with queue dependent parameters, independent from customer to customer and independent from the arrivals. The stability of such systems is characterized under the action~of an arbitrary, not necessarily Markovian, service allocation policy. Maximum likelihood estimates are obtained in explicit form for the service rates and their~strong consistency is established. The results are then applied to the problem of adaptively controlling such systems when the service rates are unknown, under the long-run average performance criterion with instantaneous cost linear in the queue sizes.},
	address = {San Francisco, California},
	booktitle = {1984 Joint TIMS/ORSA Meeting}
}
@conference {
	title = {Delight: LQG, a CAD System for Control System Design Using LQG Controller Structure},
	author = {Baras, John S., Fan, Michael K H., Nye, W T. , Tits, A L.},
	year = {1984},
	month = {03/1984},
	abstract = {A new CAD package for the design of control systems is presented. The package combines the powerful interactive optimization-based methodology of the DELIGHT system with the control theoretic design methodology known as LQG. The result is a powerful, self-contained design package which can be used to design controllers to practical engineering specifications in a highly interactive mode. An example from the design of a flight control system for a high performance aircraft is included.},
	address = {Princeton, New Jersey},
	booktitle = {The 1984 Princeton Conference on Information Sciences and Systems,},
	pages = {pp. 1-9}
}
@conference {
	title = {Optimal Sensor Scheduling in Nonlinear Filtering of Diffusion Processes},
	author = {Baras, John S., Bensoussan, Alain.},
	year = {1984},
	month = {01/1984},
	abstract = {The nonlinear filtering problem of a vector diffusion process is considered when several noisy vector observations with possibly different dimension of their range space are available. At each time any number of these observations (or sensors) can be used in the signal processing performed by the nonlinear filter. The problem considered is the optimal selection of a schedule of these sensors from the available set, so as to optimally estimate a function of the state at the final time. Optimality is measured by a combined performance measure that allocates penalties for errors in estimation, for switching between sensor schedules, and for running a sensor. The solution is obtained in the form of a system of quasi-variational inequalities in the space of solutions of certain Zakai equations.},
	address = {Louisville, Kentucky},
	booktitle = {Joint AMS-AMAA meeting},
	pages = {pp. 786-813}
}
@conference {
	title = {Two Competing Queues with Linear Costs and Geometric Service Requirements},
	author = {Baras, John S., Dorsey, Arthur J., Makowski, Armand M.},
	year = {1983},
	month = {12/1983},
	abstract = {A discrete-time model is presented for a system of two queues cmompeting for the service attention of a single server with infinite buffer capacity. The service requirements are geometrically distributed and independent from customer to customer as well as from the arrivals. The allocation of service attention is governed by feedback policies which are based on past decisions and buffer content histories. The cost of operation per unit time is a linear function of queue sizes. Under the model assumptions, a fixed prioritization scheme known as the~{\textmu}c-rule, is shown to be optimal for the long run average criterion and for the expected discounted-criterion, over both finite and infinite horizons. Two different approaches are proposed to solve these problems. One is based on dynamic programming methodology for markov decision processes, and assumes the arrival to be i.i.d. The other is valid under no additional assumptions on the arrival streams and uses direct comparision arguments. In both cases the sample path properties of the adopted state-space model are exploited.},
	address = {San Antonio, Texas},
	booktitle = {22nd IEEE Conference on Decision and Control},
	pages = {pp. 1173-1178}
}
@conference {
	title = {Two Competing Queues with Linear Costs: The  μc-rule is Often Optimal},
	author = {Baras, John S., Dorsey, Arthur J., Makowski, Armand M.},
	year = {1983},
	month = {12/1983},
	abstract = {A discrete-time model is presented for a system of two queues competing for the service attention of a single server with infinite buffer capacity. The service requirements are geometrically distributed and independent from customer to customer as well as from the arrivals. The allocation of service attention is governed by feedback policies which are based on past decisions and buffer content histories. The cost of operation per unit time is a linear function of the queue sizes. Under the model assumptions, a fixed prioritization scheme, known as the uc-rule, is shown to be optimal for the expected long-run average criterion and for the expected discounted criterion, over both finite and infinite horizons. Two different approaches are proposed for solving these problems. One is based on the dynamic programming methodology for Markov decision processes, and assumes the arrivals to be i.i.d. The other is valid under no additional assumption on the arrival stream and uses direct comparison arguments. In both cases, the sample path properties of the adopted state-space model are exploited.},
	address = {San Antonio, Texas},
	booktitle = {22nd IEEE Conference on Decision and Control},
	pages = {pp. 186-209}
}
@conference {
	title = {Simultaneous Detection and Estimation for Diffusion Process Signals},
	author = {Baras, John S.},
	year = {1983},
	month = {09/1983},
	abstract = {We consider the problem of simultaneous detection and estimation when the~signals corresponding to the M different hypotheses can be modelled as outputs of M distinct stochastic dynamical systems of the Ito type. Under very mild assumptions on the models and on the cost structure we show that there exist a set of sufficient statistics for the simultaneous detection-estimation problem that can be computed recursively by linear equations. Furthermore we show that the structure of the~detector and estimator is completely determined by the cost structure. The methodology used ~employes recent advances in nonlinear filtering and stochastic control of partially observed stochastic systems of the Ito type. Specific examples and applications in radar tracking and discrimination problems are given.},
	address = {St. Jovite, Quebec, Canada},
	booktitle = {The 1983 IEEE International Symposium on Information Theory},
	pages = {pp. 104-105}
}
@conference {
	title = {Adaptive Control of Two Competing Queues},
	author = {Baras, John S., Dorsey, Arthur J.},
	year = {1983},
	month = {04/1983},
	abstract = {The adaptive control of two queues competing for the services of a single server is treated. The arrival rates and service rates are considered constant but unknown. Convergence results for certainty-equivalence type, adaptive control schemes are established. Several possible extensions of the results are discussed briefly.},
	address = {San Diego, California},
	booktitle = {1983  IEEE International Conference on Computer Communications (INFOCOM)},
	pages = {pp. 427-435}
}
@conference {
	title = {Adaptive Control of Two Competing Queues},
	author = {Baras, John S., Dorsey, Arthur J.},
	year = {1983},
	month = {04/1983},
	abstract = {We consider the problem of optimally all locating the time of a server to two parallel queues. "First we consider the problem when the queue sizes are observed, although the arrival and departure rates are not available, but have to be estimated. We next consider the problem when the arrival process is observed, but its rate is unknown, while the departure process is not observed and its rate known within certain bounds. In both cases adaptive control schemes are developed. The performance criterion used is aggregate delay .},
	address = {Chicago, Illinois},
	booktitle = {The 1983 Institute for Operations Research and the Management Sciences Joint ORSA/TIMS Meeting (INFORMS)},
	pages = {pp. 104}
}
@conference {
	title = {Decentralized Stabilization of Large Scale Systems by Frequency Domain Methods},
	author = {Bennett, William H., Baras, John S.},
	year = {1983},
	month = {03/1983},
	abstract = {A notion of weak coupling between subsystem~of a large-scale~system is developed based on a sufficient condition for a linear, time-invariant MIMO systems. The weak coupling measure provides a frequency dependent requirement on the system response for stability of a decentralized controller for the system. An abstract notion of a generalized Nyquist criterion for MIMO systems (as discussed in Brockett and byrnes [7]~)~is extended for decentralized feedback control. Computational methods are provided which exploit a connection between a gap-metric and the principal angles between pairs of subspaces. The principal angles are shown to be related to the singular values of an easily conputed matrix.},
	address = {Baltimore, Maryland},
	booktitle = {The 1983 Conference on Information Sciences and Systems},
	pages = {pp. 599-606},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Transfer Function Classes Appearing in Linear Distributed Systems: Applications to Feedback Compensation},
	author = {Baras, John S.},
	year = {1983},
	month = {01/1983},
	address = {Norfolk, Virginia},
	booktitle = {SIAM 1983 Fall Meeting}
}
@conference {
	title = {Algorithms and Computational Aspects Pertaining to Block Diagonal Methods for Design of Decentralized Feedback Compensation},
	author = {Bennett, William H., Baras, John S.},
	year = {1982},
	month = {12/1982},
	abstract = {In a previous paper the notion of a block diagonally dominant transfer function matrix is used to provide criteria for the design of decentralized feedback control. In this paper we develop computer implementable algorithms for determining the block diagonal dominance condition. The algorithms are developed with consideration for numerical stability. Implementation of the algorithms in an interactive computing environment is suggested.},
	address = {Orlando, Florida},
	booktitle = {21st IEEE Conference on Decision and Control},
	pages = {pp. 479-484}
}
@conference {
	title = {Dynamic Observers as Asymptotic Limits of Recursive Filters},
	author = {Baras, John S., Krishnaprasad, P S.},
	year = {1982},
	month = {12/1982},
	abstract = {~

In this paper we discuss the ansatz: nonlinear observer = limit of nonlinear filter. The results of Vent-tsel{\textquoteright} and Freidlin on large deviations are useful in interpreting observer trajectories as {\textquoteright}most-likely{\textquoteright} paths.},
	address = {Orlando, Florida},
	booktitle = {21st IEEE Conference on Decision and Control},
	pages = {pp. 1126-1127}
}
@conference {
	title = {Local Stochastic Models in Large Scale Stochastic Hamiltonian Systems},
	author = {Blankenship,  Gilmer L., Baras, John S.},
	year = {1982},
	month = {10/1982},
	abstract = {We consider the problem of isolating the dynamical behavior of a portion of a system imbedded in a large stochastic system. The large scale system is assumed to have a Hamiltonian structure. The method employed is the derivation of the appropriate master equations. Several examples illustrate the theory.},
	address = {Virginia Beach, Virginia},
	booktitle = {The IEEE International Symposium on Large Scale Systems},
	pages = {pp. 474-478}
}
@conference {
	title = {Nonlinear Filtering of Diffusion Processes: Implementable Approximations of the Duncan-Mortensen-Zakai Equation},
	author = {Baras, John S.},
	year = {1982},
	month = {07/1982},
	abstract = {Numerical methods for the solution of the robust version of the~Duncan-Mortensen-Zakai partial differential equation are considered.~Both semidiscretization and complete~discretization schemes are~included. Direct implementation of such schemes via array processors~is proposed as a design method for nonlinear filters. The importance~of existence, uniqueness~and tail behavior of solutions is irelated to ~properties of such implementations.~},
	address = {Les Arcs, France},
	booktitle = {The 1982 IEEE International Symposium of Information Theory},
	pages = {pp. 1-4}
}
@conference {
	title = {Accurate Evaluation of Stochastic Wiener Integrals with Applications to Scattering and Nonlinear Filtering Problems},
	author = {Hopkins, William E., Blankenship,  Gilmer L., Baras, John S.},
	year = {1982},
	month = {01/1982},
	abstract = {Using s one approximation formulas for stochastic Wiener function Space integrals , it is possible to approximate~the~conditional densities which arise in the nonlinear filtering of diffusion processes to within O(n), with n \&gt;= 1 arbitrary, by n-fold ordinary integrals. The latter have the simple form of a {\textquoteright}rectangular rule", but their accuracy is an order of magnitude better . Then {\textendash} fold integral. can be further decomposed into a recursion involving in one dimensional integrals. The sequence is recursive in the increments of the observation process~in the filtering problem . It is not, however , recursive in time. The one dimensional integrals are naturally treated by an m - step Gaussian quadrature which has an error proportiona1 to nm! / 2" (2 m) : ). (The proportionality constant can be estimated and optimized. ) The computation of these individual integrals can be reduced further by exploiting~certain inherent symmetries of the problem, and by doing some preliminary, {\textquoteright}off-line{\textquoteright} computing. The end result is a highly accurate, computationally efficient numerical algorithm for ~evaluating conditional densities for a substantial class of non linear filtering problems . By accepting light reductions~in accuracy , One can Obtain an algorithm (apparently) fast enough, when efficiently coded, for "Online" recursive filtering in real-time~},
	address = {Shanghai, Peoples Republic of China, Gordon and Breach, New York},
	booktitle = {Recent Developments in Control Theory and its Applications, Proceedings of IEEE--Chinese Association for Automation, Bilateral Meeting on Control Systems},
	pages = {pp. 54-68}
}
@article {
	title = {Accurate Evaluation of Stochastic Wiener Integrals with Applications to Scattering and Nonlinear Filtering Problems},
	author = {Blankenship,  Gilmer L., Baras, John S.},
	year = {1981},
	month = {01/1981},
	abstract = {In 1973 A. J. Chorin [Math. Comp., 27 (1973), pp. 1-15] reported quadrature formulas for the approximation~of a class of Wiener path integrals by n-fold ordinary integrals with an error O(n-2). Similar formulas are presented here for certain stochastic Wiener function space integrals in which n-fold integral approximations result in error O(n^-2) or O(n^-3/2). Stochastic Wiener integrals arise in the physics of wave propagation in random media and in signal estimation problems in communication theory. The present formulas provide simple, accurate computational tools for these applications, among others. This point is illustrated by several examples in the paper.},
	pages = {pp. 518-552},
	volume = {Vol.  41},
	number = {3},
	journal = {SIAM Journal on Applied Mathematics}
}
@conference {
	title = {Feedback Compensation with Irrational Transfer Functions: An Algebraic Approach},
	author = {Baras, John S.},
	year = {1981},
	month = {12/1981},
	abstract = {We present here extensions of earlier work [1]~on dynamic feedback compensation of infinite dimensional systems. The extensions are in two directions: (a) Unstable (in the input-output sense) plans are allowed (b) New classes of irrational transfer functions are being considered (other than meromorphic of bounded type).},
	address = {San Diego, California},
	booktitle = {20th IEEE Conference on Decision and Control},
	pages = {885-886}
}
@conference {
	title = {Filtering and Smoothing Equations for the Filtering Problems of Benes},
	author = {Ocone, D. L., Baras, John S.},
	year = {1981},
	month = {12/1981},
	abstract = {Filtering of a diffusion with nonlinear drifts of a type defined by Benes is studied. Explicit, finite dimensional, recursive filters are shown to exist for moments and polynomial functionals of the diffusion, and a smoothing formula is given. These results are related to current, geometric approaches to filtering.},
	address = {San Diego, CA},
	booktitle = {20th IEEE Conference on Decision and Control},
	pages = {pp. 83-88}
}
@conference {
	title = {Approximate Solution of Nonlinear Filtering Problems by Direct Implementation of the Zakai Equation},
	author = {Baras, John S.},
	year = {1981},
	month = {12/1981},
	abstract = {Numerical methods for the solution of the robust version of the Duncan-Mortensen-Zakai partial differential equation are considered. Both semidiscretization and complete discretization schemes are included. Direct implementation of such schemes via array processors is proposed as a design method for nonlinear filters. The importance of existence, uniqueness and tail behavior of solutions is related to properties of such implementations.},
	address = {San Diego, CA},
	booktitle = {20th IEEE Decision and Control Conference},
	pages = {pp. 309-310}
}
@conference {
	title = {Stochastic Control of Two Competing Queues},
	author = {Baras, John S., Belbas, Stavros A.},
	year = {1981},
	month = {10/1981},
	abstract = {We consider optimal server time allocation to two parallel queues. The server has available complete past observations of the queue sizes for his decisions. The infinite time discounted version of the problem is analyzed here. It is shown that the optimal strategy is stationary. The optimal value function is shown to be the unique solution of the Bellman equation. Finally, analysis of degenerate Bellman equations, of the type appearing in this problem is presented. Numerical methods of solution can be derived from the results presented here.},
	address = {Monticello, IL},
	booktitle = {19th Allerton Conference on Communication, Control and Computing},
	pages = {pp. 269-278}
}
@conference {
	title = {Nonlinear Filtering of Diffusion Processes},
	author = {Baras, John S., Blankenship,  Gilmer L., S. K. Mitter},
	year = {1981},
	month = {07/1981},
	abstract = {Representations of conditional statistics (densities) are~described for the problem of nonlinear estimation of diffusion processes. Existence and uniqueness properties and algebraic structure of the Duncan-Mortensen-Zakai evolution equation are considered together with some approximation techniques.},
	address = {Kyoto, Japan},
	booktitle = {8th IFAC World Conference},
	pages = {pp. 57-62}
}
@conference {
	title = {Overview of Some Recent Results on Traffic Control},
	author = {Levine, William S., Baras, John S.},
	year = {1981},
	month = {06/1981},
	abstract = {This paper presents an overview of the authors{\textquoteright} recent research on urban traffic control. Since the technical details are very complicated and well reported elsewhere the emphasis is on placing these results in a traffic context. A fairly complete solution to the optimal control of an isolated intersection is outlined. The extension of these results to networks is sketched. Finally, some interesting areas for further research are given.},
	address = {Henniker, New Hampshire},
	booktitle = {Engineering Foundation Conference on Issues in Control of Urban Traffic Systems},
	pages = {pp. 43-49}
}
@conference {
	title = {Frequency Domain Design of Linear Distributed Systems},
	author = {Baras, John S.},
	year = {1980},
	month = {12/1980},
	abstract = {Using techniques from the theory of operators and the Hardy spaces of analytic functions we extend to certain classes of linear distributed systems a well known design technique for lumped parameter systems: dynamic-pole-relocation.},
	address = {Albuquerque, New Mexico},
	booktitle = {19th IEEE Conference On Decision and Control},
	pages = {pp. 728-732}
}
@conference {
	title = {Group Invariance Methods in NonLinear Filtering Of Diffusion Processes},
	author = {Baras, John S.},
	year = {1980},
	month = {12/1980},
	address = {Albuquerque, New Mexico},
	booktitle = {19th IEEE Conference On Decision and Control},
	pages = {pp. 72-79}
}
@conference {
	title = {Group Invariance Methods in Nonlinear Filtering of Diffusion Processes},
	author = {Baras, John S.},
	year = {1980},
	month = {06/1980},
	abstract = {Given two {\textquotedblleft}nonlinear filtering problems{\textquotedblright} described by the processes

dxi(t)=fi(xi(t))dt+gi(xi(t))dwi(t)dxi(t)=fi(xi(t))dt+gi(xi(t))dwi(t)

dyi(t)=hi(xi(t))dt+dvi(t),i=1,2,dyi(t)=hi(xi(t))dt+dvi(t),i=1,2,

we define a notion of strong equivalence relating the solutions to the corresponding Mortensen-Zakai equations

dui(t,x)=Liui(t,x)dt+Li1ui(t,x)dyit,i=1,2,dui(t,x)=Luii(t,x)dt+L1iui(t,x)dyti,i=1,2,

which allows solution of one problem to be obtained easily from solutions of the other. We give a geometric picture of this equivalence as a group of local transformations acting on manifolds of solutions. We then show that by knowing the full invariance group of the time invariant equations

dui(t,x)=Liui(t,x)dt,i=1,2,

we can analyze strong equivalence for the filtering problems. In particular if the two time invariant parabolic operators are in the same orbit of the invariance group we can show strong equivalence for the filtering problems. As a result filtering problems are separated into equivalent classes which correspond to orbits of invariance groups of parabolic operators. As specific example we treat V. Bene{\v s}{\textquoteright}s case establishing from this point of view the necessity of the Riccati equation.},
	address = {Savoie, France},
	booktitle = {Stochastic Systems: The Mathematics of Filtering and Identification and Application},
	pages = {pp. 565-572}
}
@conference {
	title = {Block Diagonal Dominance and Design of Decentralized Compensators},
	author = {Bennett, William H., Baras, John S.},
	year = {1980},
	month = {06/1980},
	abstract = {An extension of Rosenbrock{\textquoteright}s design method for linear multivariable~systems is presented, based on the concept of block diagonal dominance for rational~transfer function matrices.~The technique allows independent design of compensators for low-interacting subsystems.~The flexibility of the method with~respect to partitioning and measured of gain leads to improved estimates for overall~system stability under decentralized compensator design.~ Various new directions~and extensions suggested by our methods are discussed and examples illustrate~the theory.},
	address = {Toulouse, France},
	booktitle = {IFAC Symposium on Large Scale Systems: Theory and Applications},
	pages = {pp. 93-102}
}
@conference {
	title = {Some Results on Computer Control of Urban Traffic},
	author = {Baras, John S., Levine, William S.},
	year = {1980},
	month = {06/1980},
	abstract = {The problem of controlling vehicle traffic on an urban street network is a particular example of a large scale systems problem,~In a reasonably typical~network there will be one thousand or more traffic signals, there may be several hundred sensors (vehicle detectors) and the network is typically distributed over~several hundred square miles. It is now quite common to control these systems primarily from a central computer. The traffic control problem is modelled by a kind of "store and forward" network in which vehicles are {\textquoteright}stored{\textquoteright} in queues at the signals and "forwarded{\textquoteright} in platoons. The data from detectors is modelled as a point process that is statistically related~to the queues and platoons.~It would be very tempting to design optimal feedback control algorithms for these~systems. However, the size of the problems makes this impossible. Instead sub-optimal controls are developed. These sub-optimal controls use the minimum error variance estimator of the queues at each intersection as determined from the above model to improve the control provided by several intuitively derived sub-optimal~controls. The sub-optimal controls have been tested using a good simulation of urban traffic. The sub-optimal controls give substantially better performance than benchmark open loop controls. Conditions under which the network can be decomposed~than~into subnetworks without significant degradation in performance are also given.~},
	address = {Toulouse, France},
	booktitle = {IFAC Symposium on Large Scale Systems: Theory and Applications},
	pages = {pp. 449-458}
}
@conference {
	title = {Nonlinear Filtering of Diffusion Processes: A Generic Example},
	author = {Blankenship,  Gilmer L., Baras, John S.},
	year = {1979},
	month = {12/1979},
	abstract = {An analytical procedure is described for~ treating a generic nonlinear filtering problem.},
	address = {Ft. Lauderdale, Florida},
	booktitle = {18th IEEE Conference on Decision and Control}
}
@conference {
	title = {Linear Stochastic Systems with Memoryless Nonlinearities},
	author = {Baras, John S., Goldberg, Allen Jay.},
	year = {1979},
	month = {12/1979},
	abstract = {Our motivation to study this class of systems comes from a basic need to develop analytical methods to analyze and evaluate radar systems " performance in a realistic environment and in particular with distributed targets. We need, therefore, simple probabilistic~models for the various "noise " processes that influence ~radar behavior in such an environment (e.g. amplitude Scintillation, angle noise~, sea clutter and~sea multipath effects ) . In our ~previous work we have succeeded in developing such models that match very well experimental evidence concerning the statistics of such noise processes . The models developed consist of linear stochastic systems coupled with smooth memoryless nonlinearities. In this paper we report our current efforts to study such systems by analyzing the functional expansion that expresses the input-output behavior . In particular , we establish conditions for the statistical validity of a finite functional expansion and techniques for obtaining directlly the required kernels from experimental data . We also discuss applications to some related detection problems . Finally , we indicate how these~results can be extended to more general classes of systems than the ones we have considered to date.},
	address = {Ft. Lauderdale, Florida},
	booktitle = {18th IEEE Conference on Decision and Control},
	pages = {p. 1038}
}
@conference {
	title = {Algorithms for the Computer Control of Urban Traffic},
	author = {Baras, John S., Levine, William S.},
	year = {1979},
	month = {08/1979},
	abstract = {Recent developments in computer technology have made substantial computational~capability, in the form of mini- and micro-computers, available at modest prices.~This, coupled with the available traffic sensors, controllable traffic signals and~communications, makes the computer control of traffic feasible in many urban areas~today. Many such systems are either operating or are being planned.~

Software for today{\textquoteright}s hardware environment can be oriented toward several, or~many, small machines each of which controls a small local area. Alternatively,the software can do more pre-processing of data in a small machine located near~the detector thereby reducing communication costs.~

This paper describes a set of filtering, prediction and control algorithms~that are primarily intended for traffic responsive control of networks. A way~to partition the network algorithms among a collection of microprocessors is~proposed. Because of the way in which the control computations can be~partitioned, the algorithms will also work well for isolated intersections.},
	address = {University of California, Berkeley},
	booktitle = {International Symposium on Traffic Control Systems}
}
@conference {
	title = {On the Conditional Density Equation in Nonlinear Filtering Problems},
	author = {Blankenship,  Gilmer L., Baras, John S.},
	year = {1979},
	month = {06/1979},
	abstract = {We consider the unnormalized conditional density equation arising from a very simple, albeit nontrivial, nonlinear filtering problem. After establishing existence and uniqueness of solutions for this stochastic partial differential equation, we derive an expression for the solution as a "doubly~stochastic{\textquoteright}{\textquoteright} Feynnnann - Kac path integral. The results are extensions of previous results by Pardoux, Chow and others, in that certain operators appearing in this stochastic partial differential equation are unbounded. We then consider the problem of computing the requisite Wiener integral in exact or approximate form. In a different direction an {\textquoteright}{\textquoteright}assumed density{\textquoteright}{\textquoteright} approximation method is applied to this specific stochastic p. d. e. Certain relations with quantum filtering problems are discussed and the possibility of a direct {\textquoteright}distributed{\textquoteright} implementation is investigated. Finally we show how by appropriate nonlinear transformations, these ideas and techniques can be extended to an interesting class of nonlinear filtering problems with multiplicative noise.},
	address = {Grignano, Italy},
	booktitle = {1979 IEEE International Symposium on Information Theory},
	pages = { p. 97}
}
@conference {
	title = {Quantum Filtering with Counting Measurements},
	author = {Baras, John S.},
	year = {1979},
	month = {06/1979},
	abstract = {Continuous time quantum filtering problems are formulated based on ideas from quantum stochastic processes. This formulation extends previous work in~that it allows modelling of the interaction between the measurement process and~the state of the quantum field. However, the abstract quantum measurements~are restricted to those that can be implemented by counting measurements. The~type and properties of the resulting point process are discussed. Following ideas~of Davies on Quantum stochastic processes the optimal filtering problem, including~optimal measurement selection (from the above type) is formulated. Methods of~solutions are discussed and examples illustrate the results. The operator~differential equation satisfied by the density operator is analyzed and relations~with stochastic partial differential equations of a specific type are illustrated.},
	address = {Grignano, Italy},
	booktitle = {1979 IEEE International Symposium on Information Theory},
	pages = {pp.1- 8}
}
@conference {
	title = {On the Point Process Disorder Problem and Applications to Urban Traffic Estimation},
	author = {Dorsey, Arthur J., Baras, John S., Levine, William S.},
	year = {1979},
	month = {03/1979},
	abstract = {We consider here the point process disorder problem in its generality and we develop the maximum likelihood and MAP estimates of the disorder time T. Applications of the results to the platoon determination problem in urban traffic show that both estimators outperform previous solutions to the problem.},
	address = {Baltimore, MD},
	booktitle = {1979 Conference on Information Sciences and Systems},
	pages = { pp. 37-42},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Block Diagonal Dominance and Design of Decentralized Compensators},
	author = {Bennett, William H., Baras, John S.},
	year = {1979},
	month = {03/1979},
	abstract = {An extension of Rosenbrock{\textquoteright}s design method for linear multivariable systems is presented, based on the concept of block diagonal dominance for rational transfer function matrices. The technique allows independent~design of compensators for low-interacting subsystems. The flexibility of the method with respect to partitioning and measures of gain leads to improved estimates for overall system stability under decentralized compensator~designs. Various new directions and extensions suggested by our methods are discussed and examples illustrate the theory.},
	address = {Baltimore, MD},
	booktitle = {1979 Conference on Information Sciences and Systems},
	pages = {pp. 343-351},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Traffic Estimation Based On Point Process Models},
	author = {Baras, John S., Levine, William S., Dorsey, Arthur J., Lin, Tahsin L.},
	year = {1979},
	month = {02/1979},
	abstract = {Two families of models for the relation between detector data and the flow of traffic on urban streets are developed. The first describes the relation between the queues at traffic signal and data from nearby detectors. The second model~headways statistics for urban traffic thereby relating detector data to the passage of platoons of vehicles. Recent results in the theory of point processes then give the non-linear minimum error variance filters/predictors corresponding to these models. It is shown that these optimal~estimators are computationally feasible in a microprocessor. The algorithm also performs very well when tested using data derived from UTCS-I traffic simulation.},
	address = {Asilomar conference grounds, Pacific Grove,  CA},
	booktitle = {Engineering Foundation Conference on Issues in Control of Urban Traffic Systems},
	pages = {pp. 266-285}
}
@conference {
	title = {Estimation of Traffic Platoon Structure from Headway Statistics},
	author = {Baras, John S., Levine, William S., Dorsey, Arthur J.},
	year = {1978},
	month = {12/1978},
	abstract = {This paper deals first with the modeling of urban traffic headway statistics. It is shown that a composite distribution based on the convex combination of a lognormal and a shifted exponential distribution gives a good fit to observed traffic data. This statistical model is then used to generate a model for the formation and passage of "platoons" of vehicles. It is shown that the problem of estimating the time at which a "platoon" passes a detector, as well as the number of vehicles in the disorder "platoon", problem. corresponds An optimal to the estimator point process for the platoon size and passage time, based on detector data, is then derived via known results for the point process disorder problem. It is shown that the computations required by~this estimator can be performed~in a microprocessor. required by this Furthermore, the estimator is tested against the UTCS-1 traffic simulator and performs very well. Parameter sensitivity analysis of the estimator is presented. Finally, the use of these results to improve the filter/predictor described in a companion paper, and vice versa, is explained.},
	address = {San Diego, CA},
	booktitle = {17th IEEE Conference on Decision and Control},
	pages = {pp. 697-703}
}
@conference {
	title = {Discrete Time Point Processes in Urban Traffic Queue Estimation},
	author = {Baras, John S., Levine, William S., Lin, Tahsin L.},
	year = {1978},
	month = {12/1978},
	abstract = {This research was motivated by the belief that it is possible to develop improved algorithms for the computer control of urban traffic. Previous research suggested that the computer software, and especially the filtering and prediction algorithms, is the limiting factor in computerized traffic control. Since the modern approach to filtering and prediction begins with the development of models for the generation of the data and since these models are also useful in the control problem, this paper deals with the modeling of traffic queues and filtering and prediction.

It is shown that the data received from vehicle detectors is a discrete time point process. The formation and dispersion of queues at a traffic signal is then modeled by a discrete-time time-varying Markov chain which is related to the observation point process. Three such models of increasing complexity are given. Recent results in the theory of point-process filtering and prediction are then used to derive the nonlinear minimum error variance filters/predictors corresponding to these models. It is then shown that these optimal estimators are computationally feasible in a microprocessor. All three algorithms were tested against the UTCS-1 traffic simulator and, in one case, against an algorithm in current use called ASCOT. Some results of these tests are shown. They indicate good performance in every case and better performance than ASCOT in the comparable case.},
	address = {San Diego, CA},
	booktitle = {17th IEEE Conference on Decision and Control},
	pages = {pp. 12-27}
}
@conference {
	title = {Signal Filtering with Gaussian Quantum States and Canonical Measurements},
	author = {Harger, Robert O., Baras, John S.},
	year = {1977},
	month = {10/1977},
	address = {Ithaca, New York},
	booktitle = {1977 IEEE International Symposium on Information Theory},
	pages = {pp. 74}
}
@conference {
	title = {Continuous Quantum Filtering},
	author = {Baras, John S.},
	year = {1977},
	month = {09/1977},
	abstract = {We consider here the general filtering problem for signals carried by quantum mechanical fields. The continuous time, continuous quantum measurement problem is formulated. Simple examples from quantum optics illustrate the approach.},
	address = {Monticello, Illinois},
	booktitle = {15th Allerton Conference},
	pages = {pp. 68-77}
}
@conference {
	title = {Efficient Algorithms For Operator Riccati Equations And Applications To Distributed Parameter Systems},
	author = {Baras, John S.},
	year = {1977},
	month = {09/1977},
	abstract = {Filtering and quadratic optimal control problems for linear distributed parameter~ systems lead to an operator Riccati equation. The applicability of the theoretical~results is severely hindered by the task of solving this operator Riccati equation.~The new Chandrasekhar type algorithms hold promise for significant reduction in~the computational complexity of these problems. In this paper we study the~operator Riccati equation with time varying operators, and derive various alternatives for the solution. As a result we: l) rigorously establish the Chandrasekhar~type algorithms for Linear Tirne Varying Distributed Systems; 2) rigorously~ e stablish the proper generalization of the partitioning algorithms for lumped~systems of Lainiotis and Reid, to distributed systems. In addition the computational savings implied by these algorithms is discussed and their applicability~and effectiveness is demonstrated by explicit examples for various distributed parameter systems.},
	address = {Wurzburg, Federic Republic of Germany},
	booktitle = {8th IFIP Conference on Optimization Techniques}
}
@conference {
	title = {Estimation of Traffic Flow Parameters in Urban Traffic Networks},
	author = {Baras, John S., Levine, William S.},
	year = {1977},
	month = {06/1977},
	abstract = {The basic problem addressed in this paper is the development of better software for the computer control of urban traffic. Previous research indicates that the computer software, and especially the filtering and prediction algorithm, is the limiting factor in computerized traffic control. Recently developed techniques for the filtering, prediction~and control of point processes, the type of statistics that occur in traffic flow, are used to develop filtering and prediction algorithms to facilitate the development of traffic responsive urban traffic control systems.},
	address = {San Francisco, CA},
	booktitle = {The 1977 JACC},
	pages = {pp. 428-434}
}
@conference {
	title = {Stochastic Partial Differential Equations in Optical Communication Problems},
	author = {Baras, John S.},
	year = {1977},
	month = {01/1977},
	abstract = {In this paper we present examples of stochastic partial differential equations of the "multiplicative noise type" arising from laser communication problems. The basic origins and generic structure of these equations are described and their relation to general quantum estimation and filtering theory explained. The major part for the paper is devoted to explicitly analyze certain examples arising from practical applications and to provide exact or approximate solutions with the help of the underlying physical theories. Directions from future theoretical work are discussed.},
	address = {Taormina, Sicily},
	booktitle = {Third US-Italy Conference on Variable Structure Systems},
	pages = {pp. 21-43}
}
@conference {
	title = {Bilinear Hereditary Differential Systems: State Space Models in Hilbert Space},
	author = {Baras, John S.},
	year = {1976},
	month = {12/1976},
	abstract = {We analyze here state space models for bilinear hereditary differential systems of various levels of complexity. It is shown that for many reasons it is more convenient to develop state space models in Hilbert spaces, following the method of Delfour and Mitter. In certain cases~explicit bilinear operational differential equations are obtained that illustrate the way the controls influence the spectrum of the infinitesimal generator of the system. Certain connections with the theory of Lie senigroups are also discussed.},
	address = {Clearwater, Florida},
	booktitle = {1976 Conference on Decision and Control (CDC)},
	pages = {pp. 148-149}
}
@conference {
	title = {Filtering Techniques For Urban Traffic Data},
	author = {Baras, John S., Levine, William S.},
	year = {1976},
	month = {12/1976},
	abstract = {There is evidence that the algorithms for estimating traffic flows from sensor data need to be improved before computer controlled traffic responsive urban traffic control systems can reach their full potential effectiveness . A large part of the problem appears to be that the data - from traffic sensors is, in the statistical jargon, a marked point process. It is only very recently that the theoretical techniques for estimation based on point process data have reached the sophistication needed for traffic problems. In this paper, these techniques are used to derive several recursive algorithms for filtering traffic sensor data and predicting urban traffic flows. These filters and predictors are then evaluated and compared using simulated traffic data .},
	address = {Clearwater, Florida},
	booktitle = {1976 Conference on Decision and Control (CDC)},
	pages = {pp. 1297-1298}
}
@conference {
	title = {Filtering and Prediction Algorithms for Urban Traffic Control Systems},
	author = {Baras, John S., Levine, William S.},
	year = {1976},
	month = {07/1976},
	abstract = {There is evidence that the algorithms for estimating traffic flows from~sensor data need to be improved before computer controlled traffic responsive~urban traffic control systems can reach their full potential effectiveness. A~large part of the problem appears to be that the data from traffic sensors is,in the statistical jargon, a marked point process. It is only very recently that the theoretical techniques for estimation based on point process data have reached the sophistication needed for traffic problems. Thus, this paper~describes and illustrates the way in which these techniques are being applied~to the design of algorithms for filtering and prediction of urban traffic flows.},
	address = {Los Angeles, California},
	booktitle = {4th Intersociety Conference on Transportation},
	pages = {pp. 1-17}
}
@conference {
	title = {Linear Filtering with Quantum Mechanical Measurements},
	author = {Baras, John S., Harger, Robert O.},
	year = {1976},
	month = {06/1976},
	abstract = {Filtering problems arising in the quantum electronics are investigated in the quantum mechanical framework. In particular the minimum varience linear estimator based on optimal selection of the present quantum measurement and optimal linear processing of past and present outcomes is found for vector signal processes. Under certain natural assumptions a separation theorum is for the filter is proven~which leads to consideable simplification of the complexity of the filter. Examples from optical communication systems provide a recursive filters and illustrate the results.},
	address = {Leningrad, USSR},
	booktitle = {4th International Symposium on Information Theory},
	pages = {PP. 172-179}
}
@conference {
	title = {Conditional Expectations and Fock Space Representations in Quantum Filtering},
	author = {Baras, John S., Harger, Robert O.},
	year = {1976},
	month = {06/1976},
	abstract = {The role on conditional expectations on von Neumann algebras in the theory of quantum filtering is investigated. The relations characterising the solutions of various quantum filtering problems are interpreted via the notion of conditional expectation. The equations that describe optimal linear quantum filters are represented in Fock space of the analytical functions, and the usefulness of this representation is discussed. Finally some priliminary results on the applications of these methods in non-linear and continous time filtering are described.},
	address = {Leningrad, USSR},
	booktitle = {4th International Symposium on Information Theory},
	pages = {pp. 180-185}
}
@conference {
	title = {Infinite Dimensional Filtering Problems in Optical Communication Systems},
	author = {Baras, John S.},
	year = {1976},
	month = {06/1976},
	abstract = {Several filtering problems utilizing quantum mechanical measurements are discussed and formulated as optimization problems in infinite dimensional spaces. the solution to some of these problems and their physical interpretation is given, Two examples illustrate the implementation of the mathematical results.},
	address = {Rome, Italy},
	booktitle = {IFIP Working Conference on Distributed Parameter Systems},
	pages = {pp. 128-137}
}
@conference {
	title = {Chandrasekhar Algorithms for Linear Time Varying Distributed Systems},
	author = {Baras, John S., Lainiotis, Demetrios G.},
	year = {1976},
	month = {03/1976},
	abstract = {Generalized Chandrasekhar type algorithms are obtained that are applicable to linear time varying as well as time-invariant distributed systems. Utilizing the framework of J.H. Lions for quadratic controla and the framework of A. Bensoussan for filtering of linear distributed systems we analyze the implications of these algorithms.},
	address = {Baltimore, Maryland},
	booktitle = {1976 Conference on Information Sciences and Systems},
	pages = {pp. 269-274},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Nonclassical Filtering Problems in Quantum Electronics},
	author = {Baras, John S., Harger, Robert O.},
	year = {1975},
	month = {12/1975},
	abstract = {Filtering problems arising in quantum electronics are investigated. In particular, the minimum variance linear filtering problems incorporating quantum mechanical measurements is solved for both scalar and vector signal processes. The simplification of the filter under certain assumptions is demonstrated. Examples from optical communication systems illustrate the result.},
	address = {Houston Texas},
	booktitle = {14th IEEE Decision and Control Conference},
	pages = {pp. 804-806}
}
@conference {
	title = {Some Controllability Properties of Bilinear Delay-Differential Systems},
	author = {Baras, John S., Hampton, Luther P.},
	year = {1975},
	month = {12/1975},
	abstract = {Bilinear delay-differential systems appear frequently in applications. We present here controllability properties of such systems and in particular, we derive criteria for local accessibility and a "bang-bang" theorem.},
	address = {Houston Texas},
	booktitle = {14th IEEE Decision and Control Conference},
	pages = {pp. 360-361}
}
@conference {
	title = {Frequency Response Methods in Multivariable infinite Dimensional Linear Systems},
	author = {Baras, John S.},
	year = {1975},
	month = {08/1975},
	abstract = {Recent results on the analysis of models and structural properties of linear distributed systems are presented. The presentation emphasizes the role play-ed by harmonic analysis in these studies. The conclusions are that a careful selection of mathematical methods makes possible a satisfactory classification and detailed analysis of distributed systems models. These methods provide simple models that reflect input-output data of engineering importance.},
	address = {Montreal, Canada},
	booktitle = {2nd International Symposium on Operator Theory of Networks and Systems},
	pages = {pp. 24-28}
}
@conference {
	title = {Algebraic Structure of Infinite Dimensional Linear Systems in Hilbert Space},
	author = {Baras, John S.},
	year = {1975},
	month = {06/1975},
	address = {Udine, Italy},
	booktitle = {Symposium- Advanced School on Algebraic System Theory}
}
@conference {
	title = {Bilinear Delay Differential Systems},
	author = {Baras, John S., Hampton, Luther P.},
	year = {1975},
	month = {04/1975},
	address = {Baltimore, Maryland},
	booktitle = {1975 Conference on Information Sciences and Systems},
	pages = {pp. 26-32},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Multiparameter filtering with Quantum Measurements},
	author = {Baras, John S., Harger, Robert O.},
	year = {1975},
	month = {04/1975},
	abstract = {We analyze here the problem of estimating a member of a vector discrete time process utilizing past and present quantum mechanical~measurements. The minimum variance linear estimator based on optimal present measure-ment selection combined with an optimal linear processing of past measurements is studied. A necessary condition for the optimal extended measurement and the optimal coefficient matri-ces is given which leads to the generation of several more specialized necessary conditions. Certain operator equations related to these necessary conditions are studied and it is found that the conditions are necessary and sufficient in the commutative case. Finally when the average quantum measurement is linear in the random signal and the signal process is pairwise Gaussian, the filter separates: the optimal measurement can be taken the same as the optimal measurement with no regard to past data and the past and present data are processed classically. The results are illustrated by considering the estimator of the amplitude and phase of a laser received in a single-mode ca-vity along with thermal noise; when the random signal sequence satisfies a linear recursion, the estimate can be computed recursively.},
	address = {Baltimore, MD},
	booktitle = {1975 Conference on Information Sciences and Systems},
	pages = {178-184},
	organization = {Johns Hopkins University}
}
@conference {
	title = {Estimation of Random Signals based on Quantum Mechanical Measurements},
	author = {Baras, John S., Park, Young H.},
	year = {1974},
	month = {12/1974},
	abstract = {We consider here the problem of estimating a scalar random signal based on quantum mechanical measurements, a situation frequently appearing in optical communication systems. We find the minimum variance estimator based on the combination of optimal observable selection at each time and optimal linear processing of past measurements. We compare this estimator with the one obtained by optimal selection of observables at each time independently. Under additional assumptions we demonstrate that the former estimator uses the same physical devices as the latter, followed by recursive classical filtering. The results are illustrated in the estimation of the real amplitude of a random coherent signal through quantum mechanical measure-ments in a single mode cavity with background thermal noise.},
	address = {Pacific Grove, CA},
	booktitle = {8th Asilomar Conference on Circuits, Systems, and Computers},
	pages = {pp. 533-539}
}
@conference {
	title = {Recursive Filtering of Operator Valued Processes in Quantum Estimation},
	author = {Baras, John S., Harger, Robert O., Ephremides, Anthony.},
	year = {1974},
	month = {10/1974},
	abstract = {The unified approach to estimation of a stochastic signal satisfying a dynamical equation through the use of martingale and multiplicity theory is applied, in its infinite dimensional version, to the problem of estimation of a signal via quantum mechanical measurements in an optical communication system. The "state" is an operator valued stochastic process representing~a density operator in the quantum mechanical sense acting in an appropriate Hilbert space. The aim is the derivation of recursion relations for the optimum measurement operators that minimize a quadratic cost function. The Markovian nature of the density operator indexed by the signal process allows for optimum or suboptimum recursive filtering relations that are analogous to the ones in the classical case.},
	address = {Notre Dame, Indiana},
	booktitle = {1974 IEEE International Symposium on Information Theory}
}
@conference {
	title = {Lumped Distributed Network Synthesis and Infinite  Dimensional Realization Theory},
	author = {Baras, John S.},
	year = {1974},
	month = {04/1974},
	abstract = {We study the relations between infinite dimensional realization theory,~and the synthesis of networks using lumpted and distributed elements. In particular, we indicate how results from operator theory and especially the theory of invariant subspaces in HP spaces can be applied to both these problems. We discuss synthesis by reactance extraction and cascade synthesis.},
	address = {San Francisco, CA},
	booktitle = {IEEE Seventh International Symposium on Circuits and Systems},
	pages = {pp. 76-80}
}
@conference {
	title = {Natural Models for Infinite Dimensional Systems and their Structural Properties},
	author = {Baras, John S.},
	year = {1974},
	month = {03/1974},
	abstract = {We study here multi-input, multi-output distrib-uted parameter systems. The state space has the structure of a Hilbert space, and the evolution operators form a strongly continuous semigroup. We are thus able to include a large class of systems governed by linear partial differential equations. We present realizability conditions for the input-output maps considered and investigate canonical realizations and their properties. The main mathematical tools are invariant subspace theory in vectorial Hardy Spaces. Using the methods of this particular branch of operator theory we are able to classify the transfer functions considered according to their singularities. This classification is also related to system theoretic concepts and especially to the existence of spectrally minimal realizations. Finally, we discuss the implica-tions of these results to the structure theory of dis-tributed parameter systems, to lumped-distributed network synthesis and delay systems.},
	address = {Princeton, New Jersey},
	booktitle = {8th Annual Princeton Conference on Information Sciences and Systems},
	pages = {pp. 195-199}
}
@conference {
	title = {On Canonical Realizations with Unbounded Infinitesimal Generators},
	author = {Baras, John S.},
	year = {1973},
	month = {10/1973},
	abstract = {In this paper, we study canonical (controllable and observable) realiza-tions for infinite dimensional linear systems. In these realizations the infinitesimal state transition operator is unbounded but the generator of a Co -semigroup in a Hilbert space. We present ways to reduce a realization to a canonical one. We also study the relation between the analytic proper-ties of a transfer function and the spectral properties of the infinitesimal generators in its realizations. Finally, we describe a class of transfer functions which can be realized by a system with an infinitesimal generator having spectral properties closely related to the singularities of the trans-fer functions.},
	address = {Illinois},
	booktitle = {11th Annual Allerton Conference on Circuit and System Theory},
	pages = {pp. 1-10}
}
@conference {
	title = {H 2-Functions and Infinite Dimensional Realization Theory},
	author = {Baras, John S., Brockett, Roger W.},
	year = {1972},
	month = {12/1972},
	abstract = {In this paper, the realization question for infinite dimensional linear systems is examined for both bounded and unbounded operators. In addition to obtaining realizability criteria covering the basic cases, we discuss the relation between canonical realizations of the same system.What one finds is that the set of transfer functions, which are realizable by triples (A,b,c) with A bounded is related in a close way to the space of the complex functions analytic and square integrable on the disk |s| \&lt;1 and that the set of transfer functionsn which are~realizable by triples (A,b,c) with ~A unbounded but generating a strongly continuous semigroup is related in a close way to functions analytic and square integrable on a half-plane.},
	address = {New Orleans, Louisiana},
	booktitle = {1972 IEEE Conference on Decision and Control},
	pages = {pp. 355-360}
}
@article {
	title = {Dynamics over Signed Networks},
	author = {Shi, Guodong., Altafini, Claudio., Baras, John S.},
	year = {2018},
	month = {06/2018},
	abstract = {A signed network is a network with each link associated with a positive or negative sign. Models for nodes interacting over such signed networks, where two di erent types of interactions take place along the positive and negative links, respectively, arise from various biological, social, political, and economic systems. As modi cations to the conventional DeGroot dynamics for positive links, two basic types of negative interactions along negative links, namely the opposing rule and the repelling rule, have been proposed and studied in the literature. This paper reviews a few fundamental convergence results for such dynamics over deterministic or random signed networks under a uni ed algebraic-graphical method. We show that a systematic tool of studying node state evolution over signed networks can be obtained utilizing generalized Perron-Frobenius theory, graph theory, and elementary algebraic recursions.},
	journal = {SIAM}
}
@article {
	title = {Optimal LQG Control under Delay-dependent Costly Information},
	author = {Maity, Dipankar., Mamduhi, Mohammad H., Hirche, Sandra., Johansson, Karl Henrik., John S. Baras},
	year = {2018},
	month = {06/2018},
	abstract = {In the design of closed-loop networked control systems (NCSs), induced transmission delay between sensors and control station is an often-present issue which compromises control performance and may even cause instability. Taking into account the current advances of communication technology, a very relevant scenario within which induced delay needs to be investigated is cost-prone usage of communication resources. More precisely, if information exchange over the network is costly, then induced delay is the matter of decision maker{\textquoteright}s willingness to either pay the required cost to have immediate access to communication resource, or delay the access at a reduced price. In this article, we consider price-based decision making problem for a stochastic linear time-invariant system, and address the effect of induced delay on control performance based on LQG cost function. Assuming that network access with shorter delay is costlier, a decision maker installed at the control station determines real-time delay duration such that an optimal balance between the control performance and the communication cost is maintained. In this article, we show that, under mild assumptions on the available information for decision makers, the separation property holds between the optimal transmission and control policies. As the cost function is decomposable, the optimal policies are efficiently computed.},
	journal = {IEEE L-CSS (2018)}
}
@article {
	title = {Optimal Event Triggered Control of Nondeterministic Linear Systems},
	author = {Maity, Dipankar., Baras, John S.},
	year = {2018},
	month = {03/2018},
	abstract = {We consider an event-triggered controller synthesis problem to replace the continuous feedback policy with an intermittent feedback one for a non-deterministic linear system. An event-triggered framework communicates the measurement to the controller only at certain discrete time instances which are generated by an event-generator. The objective of this work is to synthesize an optimal event generator and controller such that the trajectory of the states of the event-triggered system mimics the trajectory of the state of the feedback system with arbitrary precision. The optimality is in the sense that the least number of state measurements are sent to the controller in order to compute the control signal. The results of this paper show that such an optimal event-triggered controller retains the linear structure when the continuous feedback controller is linear; and the optimal event-generator follows a threshold based policy, where the eventgenerator decides to send the state measurement to the controller every time a certain signal exceeds that threshold. Finally, the similar framework was extended for a controller synthesis of infinite horizon. The structural properties of the optimal eventtriggered controller and event-generator remain unchanged when extended to an infinite horizon.},
	pages = {1-3},
	journal = {IEEE Transactions on Automatic Control}
}
@article {
	title = {Convergence Analysis of Classes of Asymmetric Networks of Cucker-Smale Type with Deterministic Perturbations},
	author = {Somarakis, Christoforos., Paraskevas, Evripidis., Baras, John S., Motee, Nader.},
	year = {2017},
	month = {10/2017},
	abstract = {We discuss two nonlinear perturbed extensions of the Cucker-Smale model with asymmetric coupling weights. The first model assumes a finite collection of autonomous agents aiming to perform a consensus process in the presence of identical internal dynamics. The second model describes a similar population of agents that perform velocity alignment with the restriction of collision-free orbits. Although qualitatively different, we explain how these two non-trivial types of perturbations are analyzed under a unified framework. Rigorous analysis is conducted towards establishing sufficient conditions for asymptotic flocking to a synchronized motion. Applications of our results are compared with simulations to illustrate the effectiveness of our theoretical estimates.},
	pages = {pp. 1-11},
	journal = {IEEE transactions on control of network systems}
}
@techreport {
	title = {Distributed Opportunistic Scheduling for Wireless Ad-Hoc Networks with Block-Fading Model},
	author = {Chen, Hua., Baras, John S.},
	year = {2017},
	month = {10/2017},
	abstract = {In this paper, we study a distributed opportunistic scheduling problem to exploit the channel fluctuations in wireless ad-hoc networks. In this problem, channel probing is followed by a transmission scheduling procedure executed independently within each link in the network. We study this problem for the popular block-fading channel model, where channel dependencies are inevitable between different time instances during the channel probing phase. Different from existing works, we explicitly consider this type of channel dependencies and its impact on the transmission scheduling and hence the system performance. We use optimal stopping theory to formulate this problem, but at carefully chosen time instances at which effective decisions are made. The problem can then be solved by a new stopping rule problem where the observations are independent between different time instances. Since the stopping rule problem has an implicit horizon determined by the network size, we first characterize the system performance using backward induction. We develop one recursive approach to solve the problem and show that the computational complexity is linear with respect to network size. Due to its computational complexity, we present an approximated approach for performance analysis and develop a metric to check how good the approximation is. We characterize the achievable system performance if we ignore the finite horizon constraint and design stopping rules based on the infinite horizon analysis nevertheless. We present an improved protocol to reduce the probing costs which requires no additional cost}
}
@article {
	title = {Authentication of Swipe Fingerprint Scanners},
	author = {Ivanov, Vladimir I., Baras, John S.},
	year = {2017},
	month = {09/2017},
	abstract = {Swipe fingerprint scanners (sensors) can be distinguished based on their scanner pattern{\textemdash}a sufficiently unique, persistent, and unalterable intrinsic characteristic even to scanners of the same technology, manufacturer, and model. We propose a method to extract the scanner pattern from a single image acquired by a widely-used capacitive swipe fingerprint scanner and compare it with a similarly extracted pattern from another image acquired by the same or by another scanner. The method is extremely simple and computationally efficient as it based on moving-average filtering, yet it is very accurate and achieves an equal error rate below 0.1\% for 27 swipe fingerprint scanners of exactly the same model. We also show the receiver operating characteristic for different decision thresholds of two modes of the method. The method can enhance the security of a biometric system by detecting an attack on the scanner in which an image containing the fingerprint pattern of the legitimate user and acquired by the authentic fingerprint scanner has been replaced by another image that may still contain the fingerprint pattern of the legitimate user but has been acquired by another, unauthentic fingerprint scanner, i.e., for scanner authentication.},
	pages = {pp. 2212-2226},
	volume = {Vol. 12},
	number = {No. 9},
	journal = {IEEE Transactions on Information Forensics and Security}
}
@article {
	title = {RFID-based Smart Parking Management System},
	author = {Tsiropoulou, Eirini Eleni., Baras, John S., Papavassiliou, Symeon., Sinha, Surbhit. },
	year = {2017},
	month = {08/2017},
	abstract = {In this paper, the adoption of passive Radio Frequency Identification (RFID) tag-to-tag communication paradigm within the context of a smart parking system is evangelised, in terms of achieving improved energy-efficiency and operational effectiveness. To demonstrate that the joint routing and RFID readers{\textquoteright} transmission power minimisation problem is studied, considering tag-to-tag communication. The superiority of the proposed framework against conventional direct RFID reader-tag communication is demonstrated in terms of: (i) reduction of RFID readers{\textquoteright} transmission power to the minimum required to guarantee connectivity, and (ii) expansion of RFID reader{\textquoteright}s coverage area towards communicating with more distant tags, otherwise unreachable through direct communication.},
	pages = {pp. 1-4, 22-41},
	volume = {Vol. 3},
	journal = {Cyber-Physical Systems}
}
@article {
	title = {Active View Point Control for Detection of Dynamic Targets in Human-Robot Interaction},
	author = {Luan, Wentao., John S. Baras, Fermuller, Cornelia., Mao, Ren.},
	year = {2017},
	month = {06/2017},
	abstract = {Object detection is a fundamental task for robots, and is particularly challenging in the dynamic setting of humanrobot interaction because of the user{\textquoteright}s movements. In this work, we put forward a practical viewpoint control mechanism for object detection in human-robot interaction. We not only consider constraints from vision but also incorporate the low level robot kinematics to guarantee reachability of the desired viewpoint. Using a linear time cost score function, our system selects very fast the viewpoints, which in turn leads to a smooth user interaction experience. We also provide a method to learn from human demonstration the score function weights to fit the task{\textquoteright}s preference.
~},
	journal = {IEEE Robotics and Automation Letters (RA-L)}
}
@article {
	title = {COBRAM: Component-Based Reusable Adaptive Mitigation for Mobile Ad-Hoc Networks},
	author = {M. A. Fecko, Manasoukis, Kyriakos., Paraskevas, Evripidis., Kang, J., Baras, John S., Young, K, Phoel. W.},
	year = {2017},
	month = {02/2017},
	abstract = {This paper presents component-based reusable~adaptive mitigation (COBRAM) - a novel framework for defending~against control and data plane attacks on wireless network~protocols. The COBRAM system consists of two main parts:~the mitigated protocol-components and the component activation~engine. It applies several novel mitigation techniques embedded~in the specific protocol components to maximize the reusability of~mitigations across multiple protocols and attacks. The activation~engine selects the appropriate mitigated component based on~the type of the detected attack(s) and the inferred network state.~An extensive performance evaluation showed that COBRAM can~restore network throughput to 60-88\% of the baseline with 44\%~of the nodes attacking, with outages limited to 5-20s.},
	journal = {IEEE Communication Magazine}
}
@article {
	title = {Authentication of Area Fingerprint Scanners},
	author = {Ivanov, Vladimir I., Baras, John S.},
	year = {2016},
	month = {11/2016},
	abstract = {Each area fingerprint scanner (sensor) has a unique scanner pattern that can~be used to distinguish one scanner from another. The pattern results from im-~perfections in the conversion of the signal acquired from the object applied to the scanner into a digital image. The scanner pattern is a suciently unique,~persistent, and unalterable intrinsic characteristic of the ngerprint scanners~even to those of the same technology, manufacturer, and model. We propose a~model of the image acquisition in widely-used capacitive area ngerprint scan-~ners and a method to extract the pattern from a single image and compare it~with a similarly extracted pattern from another image. The method is very~simple and computationally ecient yet extremely accurate, achieving an equal~error rate in the order of 1e-7 for 22 scanners of exactly the same model, and is~also robust in a wide range of conditions. The scanner pattern can be used to~enhance the security of a biometric system by detecting an attack in which an~image containing the ngerprint pattern of the legitimate user and acquired by~the authentic ngerprint scanner has been replaced by another image that may~still contain the ngerprint pattern of the legitimate user but has been acquired~by another, unauthentic ngerprint scanner, i.e., for scanner authentication.},
	journal = {Submitted to Journal of Pattern Recognition}
}
@article {
	title = {The Evolution of Beliefs over Signed Social Networks},
	author = {Shi, Guodong., Proutiere, Alexandre., Johansson, Mikael., Baras, John S., Johansson, Karl Henrik.},
	year = {2016},
	month = {10/2016},
	abstract = {We study the evolution of opinions (or beliefs) over a social network modeled as a signed graph. The sign attached to an edge in this graph characterizes whether the corresponding individuals or end nodes are friends (positive links) or enemies (negative links). Pairs of nodes are randomly selected to interact over time, and when two nodes interact, each of them updates its opinion based on the opinion of the other node and the sign of the corresponding link. This model generalizes the DeGroot model to account for negative links: when two adversaries interact, their opinions go in opposite directions. We provide conditions for convergence and divergence in expectation, in mean-square, and in almost sure sense and exhibit phase transition phenomena for these notions of convergence depending on the parameters of the opinion update model and on the structure of the underlying graph. We establish a no-survivor theorem, stating that the difference in opinions of any two nodes diverges whenever opinions in the network diverge as a whole. We also prove a live-or-die lemma, indicating that almost surely, the opinions either converge to an agreement or diverge. Finally, we extend our analysis to cases where opinions have hard lower and upper limits. In these cases, we study when and how opinions may become asymptotically clustered to the belief boundaries and highlight the crucial influence of (strong or weak) structural balance of the underlying network on this clustering phenomenon},
	pages = {pp. 585-604},
	volume = {Vol. 64},
	number = {Issue 3},
	journal = {Operations Research}
}
@article {
	title = {Joint Optimization for Social Content Dissemination in Wireless Networks},
	author = {Weng, Xiangnan., Baras, John S.},
	year = {2016},
	month = {09/2016},
	abstract = {Over the last decade, success of social networks has significantly reshaped how information is~disseminated among users in terms of scale, intensity and speed. Much effort, both academic and~industrial, has been dedicated to learning the patterns of content dissemination to further facilitate ~it.~However, as users become dominantly mobile in this process, little is done to consider the impact of the~wireless environment, in particular, how to optimize the system in the presence of capacity shortage to~better disseminate the contents. In this paper, we investigate how the wireless transmission delays degrade~the performance of the content dissemination and propose a novel method to mitigate it. Results indicate~that predictions of dissemination at social layer (even coarse ones) benefit the social dissemination, by~improving scheduling performance at wireless layer. This in turn improves the accuracy of the predictions~with user feedback. We also demonstrate that the system performance is greatly improved by introducing~bias towards active user requests.},
	journal = {IEEE JSAC Special Issue on Human-In-The-Loop Mobile Networks}
}
@article {
	title = {Reachable Set Approach to Collision Avoidance for UAVs},
	author = {Zhou, Yuchen., Baras, John S.},
	year = {2016},
	month = {07/2016},
	abstract = {In this paper, we propose a reachable set based collision avoidance algorithm for unmanned aerial vehicles (UAVs). UAVs have been deployed for agriculture research and management, surveillance and sensor coverage for threat detection and disaster search and rescue operations. It is essential for the aircraft to have on-board collision avoidance capability to guarantee safety. Instead of the traditional approach of collision avoidance between trajectories, we propose a collision avoidance scheme based on reachable sets and tubes. We then formulate the problem as a convex optimization problem seeking suitable control constraint sets for participating aircraft. We have applied the approach on a case study of two quadrotors and two fix-wing aircraft collision avoidance scenario.},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Crowdsourcing with Multi Dimensional Trust and Active Learning},
	author = {Liu, Xiangyang., He He, Baras, John S.},
	year = {2016},
	month = {06/2016},
	abstract = {We consider a typical crowdsourcing task that aggregates input from multiple workers as a problem in information fusion. To cope with the issue of noisy and sometimes malicious input from workers, trust is used to model workers expertise. In a multi-domain knowledge learning task, however, using scalarvalued trust to model a workers performance is not sufficient to reflect the workers trustworthiness in each of the domains. To address this issue, we propose a probabilistic model to jointly infer multi-dimensional trust of workers, multi-domain properties of questions, and true labels of questions. Our model is flexible and extensible to incorporate metadata associated with questions. To show that, we further propose two extended models, one of which handles input tasks with real-valued features and the other handles tasks with text features by incorporating topic models. Finally, we evaluate our model on real-world datasets and demonstrate that our models are superior to state-of-the-art. In addition, our models can effectively recover trust vectors of workers, which can be very useful in task assignment adaptive to workers trust in the future. In order to decrease entropies and reduce error rates more quickly with fewer annotations from workers, we further propose strategies for selecting which questions to ask and which workers to assign the questions to based on multi- dimension characteristics of questions and workers trust values in those dimensions. These results can be applied for fusion of information from multiple data sources like sensors, human input, machine learning results, or a hybrid of them.},
	journal = {Journal of Advances in Information Fusion}
}
@article {
	title = {Emergent Behaviors over Signed Random Dynamical Networks: Relative-State-Flipping Model},
	author = {Shi, Guodong., Proutiere, Alexandre., Johansson, Mikael., Baras, John S., Johansson, Karl Henrik.},
	year = {2016},
	month = {06/2016},
	abstract = {We study asymptotic dynamical patterns that emerge among a set of nodes interacting in a dynamically evolving signed random network, where positive links carry out standard consensus and negative links induce relative-state flipping. A sequence of deterministic signed graphs defines potential node interactions that take place independently. Each node receives a positive recommendation consistent with the standard consensus algorithm from its positive neighbors, and a negative recommendation defined by relative-state flipping from its negative neighbors. After receiving these recommendations, each node puts a deterministic weight to each recommendation and then encodes these weighted recommendations in its state update through stochastic attentions defined by two Bernoulli random variables. We establish a number of conditions regarding almost sure convergence and divergence of the node states. We also propose a condition for almost sure state clustering for essentially weakly balanced graphs, with the help of several martingale convergence lemmas. Some fundamental differences on the impact of the deterministic weights and stochastic attentions to the node state evolution are highlighted between the current relative-state- flipping model and the state-flipping model considered in Shi et al., IEEE Transaction on Control of Network Systems, 2015.},
	pages = {pp. 1-11},
	volume = {Vol. 3},
	number = {Issue 2},
	journal = {IEEE transactions on control of network systems}
}
@article {
	title = {Performance-Aware Cross-layer Design in Wireless Multihop Networks via a Weighted Backpressure Approach},
	author = {Stai, Eleni., Papavassiliou, Symeon., Baras, John S.},
	year = {2016},
	month = {02/2016},
	abstract = {In this paper, we study, analyze, and evaluate a performance-aware cross-layer design approach for wireless multihop networks. Through network utility maximization (NUM) and weighted network graph modeling, a cross-layer algorithm for performing jointly routing, scheduling, and congestion control is introduced. The performance awareness is achieved by both the appropriate definition of the link weights for the corresponding application{\textquoteright}s requirements and the introduction of a weighted backpressure (BP) routing/scheduling. Contrary to the conventional BP, the proposed algorithm scales the congestion gradients with the appropriately defined per-pair (link, destination) weights. We analytically prove the queue stability achieved by the proposed cross-layer scheme, while its convergence to a close neighborhood of the optimal source rates{\textquoteright} values is proven via an epslon-subgradient approach. The issue of the weights{\textquoteright} assignment based on various quality-of-service (QoS) metrics is also investigated. Through modeling and simulation, we demonstrate the performance improvements that can be achieved by the proposed approach{\textemdash}when compared against existing methodologies in the literature{\textemdash}for two different examples with diverse application requirements, emphasizing respectively on delay and trustworthiness.},
	pages = {pp. 245-258},
	volume = {Vol. 24},
	number = {Issue 1},
	journal = {IEEE ACM Transactions on Networking}
}
@article {
	title = {Crowdsourcing with Multi Dimensial Trust and Active Learning},
	author = {Liu, Xiangyang., He, He., Baras, John S.},
	year = {2016},
	month = {01/2016},
	abstract = {We consider a typical crowdsourcing task that aggregates input from multiple workers as a problem in information fusion. To cope with the issue of noisy and sometimes malicious input from workers, trust is used to model workers expertise. In a multi-domain knowledge learning task, however, using scalar-valued trust to model a workers performance is not sufficient to reflect the worker{\textquoteright}s trustworthiness in each of the domains. To address this issue, we propose a probabilistic model to jointly infer multi-dimensional trust of workers, multi-domain properties of questions, and true labels of questions. Our model is flexible and extensible to incorporate metadata associated with questions. To show that, we further propose two extended models, one of which handles input tasks with real-valued features and the other handles tasks with text features by incorporating topic models. Finally, we evaluate our model on real-world datasets and demonstrate that our models are superior to state-of-the-art. In addition, our models can effectively recover trust vectors of workers, which can be very useful in task assignment adaptive to workers trust in the future. In order to decrease entropies and reduce error rates more quickly with fewer annotations from workers, we further propose strategies for selecting which questions to ask and which workers to assign the questions to based on multi- dimension characteristics of questions and workers trust values in those dimensions. These results can be applied for fusion of information from multiple data sources like sensors, human input, machine learning results, or a hybrid of them.~},
	journal = {Journal of Advances in Information Fusion}
}
@article {
	title = {Trust is the Cure to Distributed Consensus with Adversaries},
	author = {Liu, Xiangyang., Baras, John S.},
	year = {2016},
	month = {01/2016},
	abstract = {Extensive research efforts have been devoted to distributed~consensus with adversaries. Many diverse applications~drive this increased interest in this area including~distributed collaborative sensor networks, sensor fusion~and distributed collaborative control. We consider the~problem of detecting Byzantine adversaries in a network~of agents with the goal of reaching consensus. We~propose a novel trust model that establishes both local~trust based on local evidences and global trust based~on local exchange of local trust values. We describe~a trust-aware consensus algorithm that integrates the~trust evaluation mechanism into the traditional consensus~algorithm and propose various local decision rules based~on local evidence. To further enhance the robustness of~trust evaluation itself, we also provide a trust propagation~scheme in order to take into account~evidences of other~nodes in the network. The algorithm is flexible and extensible~to incorporate more complicated designs of decision~rules and trust models. To demonstrate the power of~our trust propagation scheme, we provide theoretical~security performance in terms of miss detection rate and~false alarm rate under regular trust graph and relaxed~security performance bound under general trust graph.~In addition, we demonstrate through simulation that the~trust-aware consensus algorithm can effectively detect~Byzantine adversaries and excluding them from consensus~iterations even in sparse networks with connectivity~less than 2f + 1, where f is the number of adversaries.~These results can be applied for fusion of trust evidences~as well as for sensor fusion when malicious sensors~are present like for example in power grid sensing~and monitoring.~},
	journal = {IEEE Transactions on Automatic Control}
}
@article {
	title = {Distributed Learning Algorithm for Multi agent Welfare Optimization},
	author = {Menon, Anup., Baras, John S.},
	year = {2016},
	month = {01/2016},
	abstract = {A multi-agent system comprising N non-strategic agents is considered. Each agent picks actions~from a finite set and receives a payoff that depends on the actions of the whole. The setting is non-model~based where the exact form of the utility (or payoff) functions are unknown, and only their ~values can~be measured by the respective agents. A distributed algorithm which enables the agents to learn to play~welfare (i.e. the sum of individual utilities) optimal actions is proposed. While the exact form of the~utilities is unknown, a novel framework is developed to capture implicit communication{\textemdash}the measured~change in utility by an agent due to actions by another{\textemdash}and convergence of the algorithm is proved~under appropriate assumptions on implicit and explicit communications. The proposed algorithm has~kinship with a body of work in learning in repeated games and the main analysis tool is perturbed~Markov chains.},
	journal = {IEEE Transactions on Automatic Control}
}
@article {
	title = {Social Network Ad Allocation and Optimization: A Hyperbolic Embedding-Based Approach},
	author = {Gao, Peixin., Miao, Hui., Baras, John S., Hajiaghayi, MohammadTaghi.},
	year = {2015},
	month = {12/2015},
	abstract = {With the increasing popularity of online social networks (SNS), many advertisers choose to post their advertisements (ads) within SNS. Advertising activity on social network sites (SNS) has grown rapidly and is now a billion-dollar business. For example, Facebook has reached more than 1 million active advertisers who contribute 90\% of its revenue. In the SNS advertising model, advertisers participating in a SNS ad campaign benefit from the effects of viral marketing and network diffusion. Modern SNS serve as advertising agents, and take advantage of the network diffusion to attract advertisers and charge for the cascading impressions. The optimal ad allocation task is the problem of choosing the ad allocation plan that maximizes revenue for the SNS. Considering that users have diffusion abilities and limited daily impressions, and advertisers have various bidding prices and budget concerns, a feasible plan that obeys the constraints is difficult to find. The solution to this problem lies in the space of N 0 |Ads|{\texttimes}|User|, which makes direct optimization unattractive. In this work, we study SNS advertising business models and formulate the SNS ad allocation problem. We show its connection with hyperbolic embedding and how the SNS ad allocation problem can be formulated as a linear program based on the hyperbolic embedding of a complex network. Accordingly, we develop a new embedding algorithm HyperCubeMap and an~optimization framework that allow for dimension reduction in the optimization process. Our proposed method is able to reduce the dimensionality of the original problem significantly, run two to four orders of magnitude faster, and reach 95\% of the optimal solution. We also discuss the possible extensions based on our current optimization framework, including shape design in allocation strategies for domain constraints like fairness and more comprehensive social influence models, in order to incorporate more real-world requirements.},
	journal = {Social Network Analysis and Mining}
}
@article {
	title = {Emergent Behaviors over Signed Random Dynamical Networks: State-Flipping Model},
	author = {Shi, Guodong., Proutiere, Alexandre., Johansson, Mikael., Baras, John S., Johansson, Karl Henrik.},
	year = {2015},
	month = {06/2015},
	abstract = {Recent studies from social, biological, and engineering network systems have drawn attention to the dynamics over signed networks, where each link is associated with a positive/negative sign indicating trustful/mistrustful, activator/ inhibitor, or secure/malicious interactions. We study asymptotic dynamical patterns that emerge among a set of nodes that interact in a dynamically evolving signed random network. Node interactions take place at random on a sequence of deterministic signed graphs. Each node receives positive or negative recommendations from its neighbors depending on the sign of the interaction arcs, and updates its state accordingly. Recommendations along a positive arc follow the standard consensus update. As in the work by Altafini, negative recommendations use an update where the sign of the neighbor state is flipped. Nodes may weight positive and negative recommendations differently, and random processes are introduced to model the time-varying attention that nodes pay to these recommendations. Conditions for almost sure convergence and divergence of the node states are established. We show that under this so-called state-flipping model, all links contribute to a consensus of the absolute values of the nodes, even under switching sign patterns and a dynamically changing environment. A no-survivor property is established, indicating that every node state diverges almost surely if the maximum network state diverges.},
	pages = {pp. 142-153},
	volume = {Vol. 2},
	number = {No. 2},
	journal = {IEEE transactions on control of network systems}
}
@article {
	title = {A Generalized Gossip Algorithm on Convex Metric Spaces},
	author = {Matei, Ion., Somarakis, Christoforos., Baras, John S.},
	year = {2015},
	month = {05/2015},
	abstract = {A consensus problem consists of a group of dynamic agents who seek to agree upon certain quantities of interest. This problem can be generalized in the context of convex metric spaces that extend the standard notion of convexity. In this paper, we introduce and analyze a randomized gossip algorithm for solving the generalized consensus problem on convex metric spaces, where the communication between agents is based on a set of Poisson counters. We study the convergence properties of the algorithm using stochastic differential equations theory. In particular, we show that the distances between the states of the agents converge to zero with probability one and in the rth mean sense. In the special case of complete connectivity and uniform Poisson counters, we give upper bounds on the dynamics of the first and second moments of the distances between the states of the agents. In addition, we introduce instances of the generalized consensus algorithm for several examples of convex metric spaces together with numerical simulations. th~mean sense. In the special case of complete connectivity and uniform Poisson counters, we give upper bounds on the dynamics of the first and second moments of the distances between the states of the agents. In addition, we introduce instances of the generalized consensus algorithm for several examples of convex metric spaces together with numerical simulations.},
	pages = {pp. 1175 - 1187},
	volume = {Vol. 60},
	number = {No. 5},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {The Asymptotic Consensus Problem on Convex Metric Spaces},
	author = {Matei, Ion., Baras, John S.},
	year = {2015},
	month = {04/2015},
	abstract = {A consensus problem consists of a group of dynamic agents who seek to agree upon certain quantities of interest. The agents exchange information according to a communication network modeled as a directed time-varying graph and evolve in a convex metric space; a metric space endowed with a convex structure. In this paper, we generalize the asymptotic consensus problem to convex metric spaces. Under weak connectivity assumptions, we show that if at each iteration an agent updates its state by choosing a point from a particular subset of the generalized convex hull generated by the agent{\textquoteright}s current state and the states of its neighbors, then agreement is achieved asymptotically. In addition, we present several examples of convex metric spaces and their corresponding agreement algorithms.},
	pages = {pp. 907-921},
	volume = {Vol. 60},
	number = {No. 4},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Flow Control in Time-Varying, Random Supply Chains},
	author = {Matei, Ion., Gueye, Assane., Baras, John S.},
	year = {2015},
	month = {01/2015},
	abstract = {This paper focuses on the logistics aspect of supply chain management. It proposes a randomized flow management algorithm for a time-varying, random, supply chain network. A constrained stochastic optimization problem that maximizes the profit function in terms of the long-run, time-average of the flows in the supply chain is formulated. The algorithm is distributed and based on queueing theory and stochastic Lyapunov analysis concepts. The long-run, time averages of the flows generated by the algorithm can get arbitrarily close to the solution of the aforementioned optimization problem. In support of the theoretical results, numerical simulations are also presented.},
	pages = {pp. 311-330},
	volume = {Vol. 77},
	journal = {Transportation Research Part E: Logistics and Transportation Review}
}
@techreport {
	title = {Nonlinear Programming Methods for Distributed Optimization},
	author = {Matei, Ion., Baras, John S.},
	year = {2015},
	month = {01/2015},
	abstract = {In this paper we investigate how standard nonlinear programming algorithms can be used to solve constrained optimization problems in a distributed manner. The optimization setup consists of a set of agents interacting through a communication graph that have as common goal the minimization of a function expressed as a sum of (possibly non-convex) differentiable functions. Each function in the sum corresponds to an agent and each agent has associated an equality constraint. By re-casting the distributed optimization problem into an equivalent, augmented centralized problem, we show that distributed algorithms result naturally from applying standard nonlinear programming techniques. Due to the distributed formulation, the standard assumptions and convergence results no longer hold. We emphasize what changes are necessary for convergence to still be achieved for three algorithms: two algorithms based on Lagrangian methods, and an algorithm based the method of multipliers. The changes in the convergence results are necessary mainly due to the fact that the (local) minimizers of the lifted optimization problem are not regular, as a results of the distributed formulation. Unlike the standard algorithm based on the method of multipliers, for the distributed version we cannot show that the theoretical superlinear convergence rate can be achieved.}
}
@techreport {
	title = {On the dynamics of linear functional differential equations with asymptotically constant solutions},
	author = {Somarakis, Christoforos., Baras, John S., Paraskevas, Evripidis.},
	year = {2015},
	month = {01/2015},
	abstract = {We discuss the dynamics of general linear functional differential equations with solutions that exhibit asymptotic constancy. We apply fixed point theory methods to study the stability of these solutions and we provide sufficient conditions of asymptotic stability with emphasis on the rate of convergence. Several examples are provided to illustrate the claim that the derived results generalize, unify and in some cases improve the existing ones.}
}
@article {
	title = {Exploiting Diversity of Usage to Enhance User Equipment Energy Efficiency in LTE Networks},
	author = {Ta, Tuan., Baras, John S.},
	year = {2014},
	month = {12/2014},
	abstract = {Energy efficiency is widely recognized as an important factor for future cellular networks. For mobile devices, energy efficiency leads to extended battery life. Existing works consider the battery to be equally important for all users at all time. We recognize that the value of a device{\textquoteright}s battery depends on the user{\textquoteright}s target usage. In particular, we introduce the notions of valueless and valued battery, as being the available battery when the user does or does not have access to a power source, respectively. We argue that user experience only depends on valued battery.We propose a cooperative system to help raise the overall amount of valued battery in the network. Our system makes use of device-to-device communications underlying LTE to create cooperative relay links between users. Users who expect to have a large amount of valueless battery help relay traffic for users with a small amount of valued battery.We develop our system as a proximity service for future LTE releases. We propose a framework to study utility functions to evaluate the value of the battery. We show that with appropriate utility functions, a set of thresholding cooperative rules ensure network performance improvement. We illustrate this improvement through simulation. Our simulator source code is made available to the public.},
	pages = {pp. 5-23},
	volume = {Vol. 59},
	number = {Issue 1},
	journal = {Special Issue on Energy Efficient 5G Wireless Technologies, Springer Telecommunication Systems Journal}
}
@techreport {
	title = {Stability by Fixed Point Theory in Time Delayed Distributed Consensus Networks},
	author = {Somarakis, Christoforos., Baras, John S., Paraskevas, Evripidis.},
	year = {2014},
	month = {09/2014},
	abstract = {We study the stability of linear time invariant distributed consensus dynamics in the presence of multiple propagation and processing delays. We employ fixed point theory (FPT) methods and derive sufficient conditions for asymptotic convergence to a common value while the emphasis is given in estimating the rate of convergence. We argue that this approach is novel in the field of networked dynamics as it is also flexible and thus capable of analyzing a wide variety of consensus based algorithms for which conventional Lyapunov methods are either too restrictive or unsuccessful.}
}
@techreport {
	title = {A non-consensus based distributed optimization algorithm},
	author = {Matei, Ion., Baras, John S.},
	year = {2014},
	month = {01/2014},
	abstract = {In this paper we introduce a discrete-time, distributed optimization algorithm executed by a set of agents whose interactions are subject to a communication graph. The algorithm can be applied to optimization costs that are expressed as sums of functions, where each function is associated to an agent. The algorithm can be applied to continuously differentiable cost functions, it is not consensus-based and is derived naturally by solving the first order necessary conditions of a lifted optimization problem with equality constraints. We show that, provided the agents{\textquoteright} initial values are sufficiently closed to a local minimizer and the step-size is sufficiently small, each agent converges to the local minimizer at a linear rate. In addition, we revisit two popular consensus-based distributed optimization algorithms and give sufficient conditions so that there use is extended to non-convex functions as well. We take a closer look at their rate of convergence and also show that unlike our algorithm, for a constant step-size, the consensus-based algorithms do not converge to a local minimizer even though the agents start close enough to the local minimizer}
}
@techreport {
	title = {A non-heuristic distributed algorithm for non-convex constrained optimization},
	author = {Matei, Ion., Baras, John S.},
	year = {2013},
	month = {12/2013},
	abstract = {In this paper we introduce a discrete-time, distributed optimization algorithm executed by a set of agents whose interactions are subject to a communication graph. The algorithm can be applied to optimization problems where the cost function is expressed as a sum of functions, and where each function is associated to an agent. In addition, the agents can have equality constraints as well. The algorithm can be applied to non-convex optimization problems with equality constraints, it is not consensus-based and it is not an heuristic. We demonstrate that the distributed algorithm results naturally from applying a first order method to solve the first order necessary conditions of an augmented optimization problem with equality constraints; optimization problem whose solution embeds the solution of our original problem. We show that, provided the agents{\textquoteright} initial values are sufficiently close to a local minimum, and the step-size is sufficiently small, under standard conditions on the cost and constraint functions, each agent converges to the local minimum at a linear rate.}
}
@techreport {
	title = {Study of OLSR for Real-time Media Streaming over 802.11 Wireless Network in Software Emulation Environment},
	author = {Jain, Kaustubh., Somasundaram, Kiran K., Brian, K Wang., Baras, John S., Roy-Chowdhury, Ayan.},
	year = {2013},
	month = {12/2013},
	abstract = {In this paper we present a setup to study the real-time traffic carrying performance of Optimized Link State Routing (OLSR) protocol using software emulation. We emulate the IEEE 802.11 MAC/PHY using the EMANE software emulator, on a cluster of machines, for different multi-hop wireless scenarios. As an instance of real-world usage scenario, we study the performance of real-time streaming media over a mesh network supported by OLSR. In particular, we study the effect of mobility and background traffic on carried load and jitter. We propose to extend this emulation setup to test the real-time performance of prototype routing protocols such as Stable Path Topology Control (SPTC) and other real-time applications.}
}
@techreport {
	title = {Development of a Framework for CPS Open Standards and Platforms},
	author = {Baras, John S., Austin, Mark A.},
	year = {2013},
	month = {11/2013},
	abstract = {This technical report describes a Framework we have developed through our research and investigations in this project, with the goal to facilitate creation of Open Standards and Platforms for CPS; a task that addresses a critical mission for NIST. The rapid development of information technology (in terms of processing power, embedded hardware and software systems, comprehensive IT management systems, networking and Internet growth, system design environments) is producing an increasing number of applications and opening new doors. In addition over the last decade we entered a new era where systems complexity has increased dramatically. Complexity is increased both by the number of components that are included in each system as well as by the dependencies between those components. Increasingly, systems tend to be more software dependent and that is a major challenge that engineers involved in the development of such systems face. The challenge is even greater when a safety critical system is considered, like an airplane or a passenger car. Software-intensive systems and devices have become everyday consumables. There is a need for development of software that is provably error-free. Thanks to their multifaceted support for networking and inclusion of data and services from global networks, systems are evolving to form integrated, overarching solutions that are increasingly penetrating all areas of life and work. When software dependent systems interact with the physical environment then we have the class of cyber-physical systems (CPS) [1, 2]. The challenge in CPS is to incorporate the inputs (and their characteristics and constraints) from the physical components in the logic of the cyber components (hardware and software). CPS are engineered systems constructed as networked interactions of physical and computational (cyber) components. In CPS, computations and communication are deeply embedded in and interacting with physical processes, and add new capabilities to physical systems. Competitive pressure and societal needs drive industry to design and deploy airplanes and cars that are more energy efficient and safe, medical devices and systems that are more dependable, defense systems that are more autonomous and secure. Whole industrial sectors are transformed by new product lines that are CPS-based. Modern CPSs are not simply the connection of two different kinds of components engineered by means of distinct design technology, but rather, a new system category that is both physical and computational [1, 2]. Current industrial experience tells us that, in fact, we have reached the limits of our knowledge of how to combine computers and physical systems. The shortcomings range from technical limitations in the foundations of cyber-physical systems to the way we organize our industries and educate engineers and scientists that support cyber-physical system design. If we continue to build systems using our very limited methods and tools but lack the science and technology foundations, we will create significant risks, produce failures and lead to loss of market. Nowadays, with increasing frequency we observe systems that cooperate to achieve a common goal, even though there were not built for that reason. These are called systems of systems. For example, the Global Positioning System (GPS) is a system by itself. However, it needs to cooperate with other systems when the air traffic control system of systems is under 3 consideration. The analysis and development of such systems should be done carefully because of the emergent behavior that systems exhibit when they are coupled with other systems. However, apart from the increasing complexity and the other technical challenges, there is a need to decrease time-to-market for new systems as well as the associated costs. This specific trend and associated requirements, which are an outcome of global competitiveness, are expected to continue and become even more stringent. If a successful contribution is to be made in shaping this change, the revolutionary potential of CPS must be recognized and incorporated into internal development processes at an early stage. For that Interoperability and Integratability of CPS is critical. In this Task we have developed a Framework to facilitate interoperability and integratability of CPS via Open Standards and Platforms. The purpose of this technical report is to introduce this Framework and its critical components, to provide various instantiations of it, and to describe initial successful applications of it in various important classes of CPS. An additional goal of publishing this technical report is to solicit feedback on the proposed Framework, and to catalyze discussions and interactions in the broader CPS technical community towards improving and strengthening this Framework. CPS integrate data and services from different systems which were developed independently and with disparate objectives, thereby enabling new functionalities and benefits. Currently there is a lack of well-defined interfaces that on the one hand define the standards for the form and content of the data being exchanged, but on the other hand take account of non-functional aspects of this data, such as differing levels of data quality or reliability. A similar situation exists with respect to tools and synthesis environments, although some work has been initiated in the latter. The technological prerequisite for the design of the aforementioned various functions and value added services of CPS is the interoperability and integratability of these systems as well as their capability to be adapted flexibly and application-specifically as well as extended at the different levels of abstraction. Dependent on the objective and scope of the application, it may be necessary to integrate component functions (Embedded Systems (ES), System of Systems (SoS), CPS), to establish communication and interfaces, and to ensure the required level of quality of interaction and also of the overall system behavior. This requires cross-domain concepts for architecture, communication and compatibility at all levels. The effects of these factors on existing or yet undeveloped systems and architectures represent a major challenge. Investigation into these factors is the objective of current national and international studies and research projects. CPS create core technological challenges for traditional system architectures, especially because of their high degree of connectivity. This is because CPS are not constructed for one specific purpose or function, but rather are open for many different services and processes, and must therefore be adaptable. In view of their evolutionary nature, they are only controllable to a limited extent. This creates new demands for greater interoperability and communication within CPS that cannot be met by current closed systems. In particular, the differences in the characteristics of embedded systems in relation to IT systems and services and data in networks lead to outstanding questions in relation to the form of architectures, the definition of system and communication interfaces and requirements for underlying CPS platforms with basic services and parallel architectures at different levels of abstraction. 4 The technological developments underlying CPS evolution require the development of standards in the individual application domains, as well as basic infrastructure investments that cannot be borne by individual companies alone. This is particularly significant for SMEs. The development and operation of uniform platforms to migrate individual services and products will therefore be as much of a challenge as joint specification standards. The creation of such quasi standards, less in the traditional mold of classic industry norms and standards and more in the sense of de facto standards that become established on the basis of technological and market dominance, will become an essential part of technological and market leadership. To summarize and emphasize, the complexity of the subject in terms of the required technologies and capabilities of CPS, as well as the capabilities and competences required to develop, control and design/ create innovative, usable CPS applications, demand fundamentally integrated action, interdisciplinarity (research and development, economy and society) and vertical and horizontal efforts in:  The creation of open, cross-domain platforms with fundamental services (communication, networking, interoperability) and architectures (including domainspecific architectures);  The complementary expansion and integration of application fields and environments with vertical experimentation platforms and correspondingly integrated interdisciplinary efforts;  The systematic enhancement with respect to methods and technologies across all involved disciplines to create innovative CPS. The aim of our research and investigations under this Task of the project, was precisely to clarify these objectives and systematically develop detailed recommendations for action. Our research and investigations have identified the following essential and fundamental challenges for the modeling, design, synthesis and manufacturing of CPS: (i) The creation and demonstration of a framework for developing cross-domain integrated modeling hubs for CPS. (ii) The creation and demonstration of a framework for linking the integrated CPS modeling hub of (i) with powerful and diverse tradeoff analysis methods and tools for design exploration for CPS. (iii) The creation of a framework of linking the integrated CPS synthesis environment of (i) and (ii) with databases of modular component and process (manufacturing) models, backwards compatible with earlier legacy systems; (iv)The creation of a framework for translating textual requirements to mathematical representations as constraints, rules and metrics involving both logical and numerical variables and the automatic (at least to 75\%) allocation of the resulting specifications to components of the CPS and of processes, in a way that allows traceability. 5 These challenges have been listed here in the order of increasing difficulty both conceptually and in terms of arriving at implementable solutions. The order also reflects the extent to which the current state of affairs has made progress towards developing at least some initial instantiations of the desired frameworks. In this context, it is useful to compare with the advanced state of development of similar frameworks and their instantiations for synthesis and manufacturing of complex microelectronic VLSI chips including distributed ones, which have been available as integrated tools by several vendors for at least a decade. Regarding challenge (i) we have performed extensive work and research in this project towards developing model-based systems engineering (MBSE) procedures for the design, integration, testing and operational management of cyber-physical systems, that is, physical systems with cyber potentially embedded in every physical component. Thus in the Framework, described in this report, for standards for integrated modeling hubs for CPS, MBSE methods and tools are prominent. Regarding the search for a framework for standards for CPS this selection has the additional advantage that it is also emerging as an accepted framework for systems engineering by all industry sectors with substantial interest in CPS [3, 7]. Regarding challenge (ii) we have performed extensive work and research in this project towards developing the foundations for such an integration, and we have developed and demonstrated the first ever integration of a powerful tradeoff analysis tool (and methodology) with our SysMLIntegrated system modeling environments for CPS synthesis [3, 7]. Primary applications of interest that we have instantiated this framework are: microgrids and power grids, wireless sensor networks (WSN) and applications to Smart Grid, energy efficient buildings, microrobotics and collaborative robotics, and the overarching (for all these applications) security and trust issues including our pioneering and innovative work on compositional security systems. A key concept here is the integration of multi-criteria, multi constraint optimization with constrained based reasoning. Regarding challenge (iii) we have only developed the conceptual Framework, as any required instantiations will require substantial commercial grade software development beyond the scope of this project. It is clear however that object-relational databases and database mediators (for both data and semantics) will have to be employed. Regarding challenge (iv) we have developed a Framework for checking and validating specifications, after they have been translated to their mathematical representations as constraints and metrics with logical and numerical variables. Various multi-criteria optimization, constrained based reasoning, model checking and automatic theorem proving tools will have to be combined. The automatic annotation of the system blocks with requirements and parameter specifications remains an open challenge.}
}
@article {
	title = {Distributed Opportunistic Scheduling for Wireless Ad-Hoc Networks with Block-Fading Model},
	author = {Chen, Hua., Baras, John S.},
	year = {2013},
	month = {11/2013},
	abstract = {In this paper, we study a distributed opportunistic scheduling problem to exploit the channel fluctuations in wireless ad-hoc networks. In this problem, channel probing is followed by a transmission scheduling procedure that is executed independently within each link in the network. We study this problem for the popular block-fading channel model, where channel dependencies are inevitable between different time instances during the channel probing phase. Different from existing works, we explicitly consider this type of channel dependencies and its impact on the transmission scheduling and hence the system performance. We use optimal stopping theory to formulate this problem, but at carefully chosen time instances at which effective decisions are made. The problem can then be solved by a new stopping rule problem where the observations are independent between different time instances. Since the stopping rule problem has an implicit horizon determined by the network size, we first characterize the system performance using backward induction. We develop one recursive approach to solve the problem and show that the computational complexity is linear with respect to the network size. Due to its computational complexity, we present an approximation for performance analysis and develop a metric to check how good the approximation is. We characterize the achievable system performance if we ignore the finite horizon constraint and apply the stopping rules based on the infinite horizon analysis nevertheless. We present an improved protocol to reduce the probing costs which require no additional cost. We characterize the performance improvement and the energy savings in terms of the probing signals. We show numerical results based on our mathematical analysis with various settings of parameters.},
	pages = {pp. 2324-2337},
	volume = {Vol. 31},
	number = {No. 11},
	journal = {IEEE Journal on Selected Areas in Communications}
}
@article {
	title = {Studying the Role of ApoE in Alzheimer{\textquoteright}s Disease Pathogenesis Using a Systems Biology Model},
	author = {Kyrtsos, C Rose., Baras, John S.},
	year = {2013},
	month = {10/2013},
	abstract = {Alzheimer{\textquoteright}s disease (AD) is the most common form of dementia. Even with its well-known symptoms of memory loss and well-characterized pathology of beta-amyloid (Aβ) plaques and neurofibrillary tangles, the disease pathogenesis and initiating factors are still not well understood. To tackle this problem, a systems biology model has been developed and used to study the varying e{\textregistered}ects of variations in the ApoE allele present, as well as the e{\textregistered}ects of short term and periodic inflammation at low to moderate levels. Simulations showed a late onset peak of Aβ~in the ApoE4 case that lead to localized neuron loss which could be ameliorated in part by application of short-term pro-inflammatory mediators. The model that has been developed herein represents one of the first attempts to model AD from a systems approach to study physiologically relevant parameters that may prove useful to physicians in the future.},
	pages = {pp. 1342003.1-1342003.21},
	volume = {Vol. 11},
	number = {Issue 5},
	journal = {Journal of Bioinformatics and Computational Biology (JBCB)}
}
@techreport {
	title = {Distributed Algorithms for Optimization Problems with Equality Constraints},
	author = {Matei, Ion., Baras, John S.},
	year = {2013},
	month = {09/2013},
	abstract = {In this paper we introduce two discrete-time, distributed optimization algorithms executed by a set of agents whose interactions are subject to a communication graph. The algorithms can be applied to optimization problems where the cost function is expressed as a sum of functions, and where each function is associated to an agent. In addition, the agents can have equality constraints as well. The algorithms are not consensus-based and can be applied to non-convex optimization problems with equality constraints. We demonstrate that the first distributed algorithm results naturally from applying a first order method to solve the first order necessary conditions for a lifted optimization problem with equality constraints; the solution of our original problem is embedded in the solution of this lifted optimization problem. We show that, provided the agents{\textquoteright} initial values are sufficiently close to a local minimizer, and the step-size is sufficiently small, under standard conditions on the cost and constraint functions, each agent converges to the local minimizer at a linear rate. Next, we use an augmented Lagrangian idea to derive a second distributed algorithm whose local convergence requires weaker sufficient conditions than in the case of the first algorithm.}
}
@techreport {
	title = {A Distributed Learning Algorithm with Bit-valued Communications for Multi-agent Welfare Optimization},
	author = {Menon, Anup., Baras, John S.},
	year = {2013},
	month = {07/2013},
	abstract = {A multi-agent system comprising N agents, each picking actions from a finite set and receiving a payoff that depends on the action of the whole, is considered. The exact form of the payoffs are unknown and only their values can be measured by the respective agents. A decentralized algorithm was proposed by Marden et. al. [1] and in the authors{\textquoteright} earlier work [2] that, in this setting, leads to the agents picking welfare optimizing actions under some restrictive assumptions on the payoff structure. This algorithm is modified in this paper to incorporate exchange of certain bit-valued information between the agents over a directed communication graph. The notion of an interaction graph is then introduced to encode known interaction in the system. Restrictions on the payoff structure are eliminated and conditions that guarantee convergence to welfare minimizing actions w.p. 1 are derived under the assumption that the union of the interaction graph and communication graph is strongly connected.}
}
@article {
	title = {On the Dynamics of a Simple Rational Planar Map},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {06/2013},
	abstract = {are discussed for various values of it{\textquoteright}s parameters. Despite the simple algebraic structure, this map, recently introduced in the literature, is very rich in non-linear phenomena. Multiple strange attractors, transitions to chaos via period doubling bifurcations, quasiperiodicity as well as intermittency, interior crisis, hyper-chaos are only a few. In this work, strange attractors, bifurcation diagrams, periodic windows, invariant characteristics are investigated both analytically and numerically.},
	pages = {pp. 1330021.1-1330021.21},
	volume = {Vol. 23},
	number = {Issue 6},
	journal = {International Journal of Bifurcation and Chaos (IJBC)}
}
@article {
	title = {Convergence Results for Ant Routing Algorithms via Stochastic Approximations},
	author = {Purkayastha, Punyaslok., Baras, John S.},
	year = {2013},
	month = {04/2013},
	abstract = {In this article, we provide convergence results for an Ant-based Routing Algorithm (ARA) for wireline, packet-switched communication networks, that are acyclic. Such algorithms are inspired by the foraging behavior of ants in nature. We consider an ARA algorithm proposed earlier by Bean and Costa [2005]. The algorithm has the virtues of being adaptive and distributed and can provide a multipath routing solution. We consider a scenario where there are multiple incoming data traffic streams that are to be routed to their respective destinations via the network. Ant packets, which are nothing but probe packets, are introduced to estimate the path delays in the network. The node routing tables, which consist of routing probabilities for the outgoing links, are updated based on these delay estimates. In contrast to the available analytical studies in the literature, the link delays in our model are stochastic, time-varying, and dependent on the link traffic. The evolution of the delay estimates and the routing probabilities are described by a set of stochastic iterative equations. In doing so, we take into account the distributed and asynchronous nature of the algorithm operation. Using methods from the theory of stochastic approximations, we show that the evolution of the delay estimates can be closely tracked by a deterministic ODE (Ordinary Differential Equation) system when the step size of the delay estimation scheme is small. We study the equilibrium behavior of the ODE system in order to obtain the equilibrium behavior of the routing algorithm. We also explore properties of the equilibrium routing probabilities and provide illustrative simulation results.},
	pages = {pp. 1-34},
	volume = {Vol.  8},
	number = {Issue 1, Article 3},
	journal = {ACM Transactions on Autonomous and Adaptive Systems (TAAS)}
}
@techreport {
	title = {A Fixed Point Theory Approach to Multi-Agent Consensus Dynamics With Delays},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {02/2013},
	abstract = {The classic linear time-invariant multi-agent consensus scheme is revisited in the presence of constant and distributed bounded delays. We create a fixed point argument and prove exponential convergence with specific rate that depends both on the topology of the communication graph and the upper bound of the allowed delay.}
}
@article {
	title = {Selfish response to Epidemic Propagation},
	author = {Theodorakopoulos, George., Le Boudec, Jean-Yves., Baras, John S.},
	year = {2013},
	month = {02/2013},
	abstract = {An epidemic that spreads in a network calls for a decision on the part of the network users. They have to decide whether to protect themselves or not. Their decision depends on the tradeoff between the perceived infection and the protection cost. Aiming to help users reach an informed decision, security advisories provide periodic information about the infection level in the network. We study the best-response dynamic in a network whose users repeatedly activate or de-activate security, depending on what they learn about the infection level. Our main result is the counterintuitive fact that the equilibrium level of infection increases as the users{\textquoteright} learning rate increases. The same is true when the users follow smooth best-response dynamics or any other continuous response function that implies a higher probability of protection when learning a higher level of infection. In both cases, we characterize the stability and the domains of attraction of the equilibrium points. Our finding also holds when the epidemic propagation is simulated on human contact traces, both when all users are of the same best-response behavior type and when they are of two distinct behavior types.},
	pages = {pp. 363 - 376},
	volume = {Volume 58.},
	number = {Issue 2},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Convergence Results for the Linear Consensus Problem under Markovian Random Graphs},
	author = {Matei, Ion., Baras, John S., Somarakis, Christoforos.},
	year = {2013},
	month = {01/2013},
	abstract = {This paper discusses the linear asymptotic consensus problem for a network of dynamic agents whose communication network is modeled by a randomly switching graph. The switching is determined by a finite state Markov process, each topology corresponding to a state of the process. We address the cases where the dynamics of the agents is expressed both in continuous time and in discrete time. We show that, if the consensus matrices are doubly stochastic, average consensus is achieved in the mean square sense and the almost sure sense if and only if the graph resulting from the union of graphs corresponding to the states of the Markov process is strongly connected. The aim of this paper is to show how techniques from the theory of Markovian jump linear systems, in conjunction with results inspired by matrix and graph theory, can be used to prove convergence results for stochastic consensus problems.},
	pages = {pp. 1574-1591},
	volume = {Vol.  51},
	number = {No. 2},
	journal = {SIAM Journal on Control and Optimization}
}
@techreport {
	title = {Compositional Analysis of Dynamic Bayesian Networks and Applications to CPS},
	author = {Yang, Shahan., Zhou, Yuchen., Baras, John S.},
	year = {2012},
	month = {12/2012},
	abstract = {Dynamic Bayesian networks (DBNs) can be effectively used to model various problems in complex dynamic systems. We perform an empirical investigation on compositional analysis of DBNs using abstraction. In static systems and hidden Markov models, computation of a metric called treewidth induces a tree decomposition that can be used to perform logical or probabilistic inference and max + optimizations in time exponential in treewidth and linear in overall system size. Intuitively, the linear scaling means that very large systems can be analyzed as long as they are sufficiently sparse and well structured. In these simple cases, summary propagation, which uses two operations, summation (projection) and product (composition), suffices to perform the inference or optimization. Here, we begin an extension of this to structured networks of communicating dynamic systems. We define generalizations of projection and composition operators that treat labeled Markov chains as primitive objects. The projection operation, corresponding to summation, is implemented as label deletion followed by exact state reduction for Markov chains, similar to Hopcroft{\textquoteright}s DFA minimization algorithm, with O(n log m) complexity. The composition operation is the product of state machines. We use canonical MDDs, similar to BDDs, to capture logical dependencies symbolically. Combining symbolic representations with Markov chain lumping algorithms is a novel contribution. Using this approach, we have created a tool leveraging model based systems engineering technologies. The communicating Markov chains are specified using UML Statecharts via Papyrus extended using an ANTLR parsed domain specific language (DSL). The tool reduces the number of states in networks of Markov chains by several orders of magnitude. In one example, a network having a product state space of more than 600 million states is reduced to about 500 states. A feature of this technique is that the state space is examined incrementally, meaning that the full state space is never explicitly represented, even as an input to the reduction algorithm. The primary reduction appears to come from symmetry which is surprising because the technique includes no explicit symmetry handling. We note that composition is efficient at least for systems with high symmetry. We describe applications to a hospital intensive care unit (ICU) from a systems engineering perspective.}
}
@article {
	title = {Sequential Anomaly Detection in Wireless Sensor Networks and Effects of Long Range Dependant Data},
	author = {Zheng, Shanshan., Baras, John S.},
	year = {2012},
	month = {10/2012},
	abstract = {Anomaly detection is important for the correct functioning of wireless sensor networks. Recent studies have shown that node mobility along with the spatial correlation of the monitored phenomenon in sensor networks can lead to observation data that have long-range dependency, which could significantly increase the difficulty of anomaly detection. In this article, we develop an anomaly detection scheme based on multiscale analysis of the long-range dependent traffic to address this challenge. In this proposed detection scheme, the discrete wavelet transform is used to approximately de-correlate the traffic data and capture data characteristics in different timescales. The remaining dependencies are then captured by a multilevel hidden Markov model in the wavelet domain. To estimate the model parameters, we develop an online discounting expectation-maximization (EM) algorithm, which also tracks variations of the estimated models over time. Network anomalies are detected as abrupt changes in the tracked model variation scores. Statistical properties of our detection scheme are evaluated numerically using long-range dependent time series. We also evaluate our detection scheme in malicious scenarios simulated using the NS-2 network simulator.},
	pages = {p.p. 458-480},
	volume = {Volume 31},
	journal = {Special IWSM Issue of Sequential Analysis (SQA)}
}
@article {
	title = {A Linear Distributed Filter Inspired by the Markovian Jump Linear System Filtering Problem},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {08/2012},
	abstract = {In this paper, we introduce a consensus-based distributed filter, executed by a sensor network, inspired by the Markovian jump linear system filtering theory. We show that the optimal filtering gains of the Markovian jump linear system can be used as an approximate solution of the optimal distributed filtering problem. This parallel allows us to interpret each filtering gain corresponding to a mode of operation of the Markovian jump linear system as a filtering gain corresponding to a sensor in the network. The approximate solution can be implemented distributively and guarantees a quantifiable level of performance.},
	pages = {Pages 1924-1928},
	volume = {Volume 48},
	number = {Issue 8},
	journal = {Automatica}
}
@article {
	title = {Consensus-Based Linear Distributed Filtering},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {08/2012},
	abstract = {We address the consensus-based distributed linear filtering problem, where a discrete time, linear stochastic process is observed by a network of sensors. We assume that the consensus weights are known and we first provide sufficient conditions under which the stochastic process is detectable, i.e. for a specific choice of consensus weights there exists a set of filtering gains such that the dynamics of the estimation errors (without noise) is asymptotically stable. Next, we develop a distributed, sub-optimal filtering scheme based on minimizing an upper bound on a quadratic filtering cost. In the stationary case, we provide sufficient conditions under which this scheme converges; conditions expressed in terms of the convergence properties of a set of coupled Riccati equations.},
	pages = {Pages 1776-1782},
	volume = {Volume 48},
	number = {Issue 8},
	journal = {Automatica}
}
@techreport {
	title = {Flow Control in Time-Varying, Random Supply Chains},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {05/2012},
	abstract = {Today{\textquoteright}s supply chains are more and more complex. They depend on a network of independent, yet~interconnected moving parts. They rely on critical infrastructures and experience a lot of time variability~and randomness. Designing strategies that deal with such constantly changing supply chains is necessary~in this increasingly globalized economy where supply chain disruptions have impacts that propagate not~only locally but also globally. In this paper we propose a randomized flow control algorithm for a time~varying, random supply chain network. We formulate a constrained stochastic optimization problem that~maximizes the profit function in terms of the long-run, time-average rates of the flows in the supply~chain. We show that our algorithm, which is based on queueing theory and stochastic analysis concepts,~can get arbitrarily close to the solution of the aforementioned optimization problem. In addition, we~describe how the flow control algorithm can be extended to a multiple firms supply chain setup and~present numerical simulations of our algorithm for different supply chain topologies.}
}
@techreport {
	title = {A performance comparison between two consensus-based distributed optimization algorithms},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {05/2012},
	abstract = {In this paper we address the problem of multi-agent optimization for convex functions expressible as sums of convex functions. Each agent has access to only one function in the sum and can use only local information to update its current estimate of the optimal solution. We consider two consensus-based iterative algorithms, based on a combination between a consensus step and a subgradient decent update. The main difference between the two algorithms is the order in which the consensus-step and the subgradient descent update are performed. We show that updating first the current estimate in the direction of a subgradient and then executing the consensus step ensures better performance than executing the steps in reversed order. In support of our analytical results, we give some numerical simulations of the algorithms as well.}
}
@article {
	title = {Adaptive Sampling For Linear State Estimation},
	author = {Rabi, Maben., Moustakides, George V., Baras, John S.},
	year = {2012},
	month = {03/2012},
	abstract = {When a sensor has continuous measurements but sends occasional messages over a data network to a supervisor which estimates the state, the available packet rate fixes the achievable quality of state estimation. When such rate limits turn stringent, the sensor{\textquoteright}s messaging policy should be designed anew. What are good causal messaging policies? What should message packets contain? What is the lowest possible distortion in a causal estimate at the supervisor? Is Delta sampling better than periodic sampling? We answer these questions for a Markov state process under an idealized model of the network and the assumption of perfect state measurements at the sensor. If the state is a scalar or a vector of low dimension, then we can ignore sample quantization. If in addition, we can ignore jitter in the transmission delays over the network, then our search for efficient messaging policies simplifies. First, each message packet should contain the value of the state at that time. Thus a bound on the number of data packets becomes a bound on the number of state samples. Second, the remaining choice in messaging is entirely about the times when samples are taken. For a scalar, linear diffusion process, we study the problem of choosing the causal sampling times that will give the lowest aggregate squared error distortion. We stick to finite horizons and impose a hard upper bound N on the number of allowed samples. We cast the design as a problem of choosing an optimal sequence of stopping times. We reduce this to a nested sequence of problems, each asking for a single optimal stopping time. Under an unproven but natural assumption about the least-square estimate at the supervisor, each of these single stopping problems are of standard form. The optimal stopping times are random times when the estimation error exceeds designed envelopes. For the case where the state is a Brownian motion, we give analytically: the shape of the optimal sampling envelopes, the shape of the envelopes under optimal Delta sampling, and their performances. Surprisingly, we find that Delta sampling performs badly. Hence, when the rate constraint is a hard limit on the number of samples over a finite horizon, we should not use Delta sampling.},
	pages = {pp. 672-702},
	volume = {Volume 50},
	number = {No. 2},
	journal = {SIAM Journal on Control and Optimization}
}
@techreport {
	title = {A randomized gossip consensus algorithm on convex metric spaces},
	author = {Matei, Ion., Somarakis, Christoforos., Baras, John S.},
	year = {2012},
	month = {02/2012},
	abstract = {A consensus problem consists of a group of dynamic agents who seek to agree upon certain quantities of interest. This problem can be generalized in the context of convex metric spaces that extend the standard notion of convexity. In this paper we introduce and analyze a randomized gossip algorithm for solving the generalized consensus problem on convex metric spaces. We study the convergence properties of the algorithm using stochastic differential equations theory. We show that the dynamics of the distances between the states of the agents can be upper bounded by the dynamics of a stochastic differential equation driven by Poisson counters. In addition, we introduce instances of the generalized consensus algorithm for several examples of convex metric spaces together with numerical simulations.}
}
@article {
	title = {Toward a Science of Cyber-Physical System Integration},
	author = {Sztipanovits, Janos., Koutsoukos, Xenofon., Karsai, Gabor., Kottenstette, Nicholas., Antsaklis, Panos., Gupta, Vijay., B. Goodwine, Baras, John S., Wang, Shige.},
	year = {2012},
	month = {01/2012},
	abstract = {| System integration is the elephant in the china store of large-scale cyber{\textendash}physical system (CPS) design. It would be hard to find any other technology that is more undervalued scientifically and at the same time has a bigger impact on the presence and future of engineered systems. The unique challenges in CPS integration emerge from the heterogeneity of components and interactions. This heterogeneity drives the need for modeling and analyzing cross-domain interactions among physical and computational/networking domains and demands a deep understanding of the effects of heterogeneous abstraction layers in the design flow. To address the challenges of CPS integration, significant progress needs to be made toward a new science and technology foundation that is model based, precise, and predictable. This paper presents a theory of composition for heterogeneous systems focusing on stability. Specifically, the paper presents a passivity-based design approach that decouples stability from timing uncertainties caused by networking and computation. In addition, the paper describes cross-domain abstractions that provide an effective solution for model-based fully automated software synthesis and high-fidelity performance analysis. The design objectives demonstrated using the techniques presented in the paper are group coordination for networked unmanned air vehicles (UAVs) and high-confidence embedded control software design for a quadrotor UAV. Open problems in the area are also discussed, including the extension of the theory of compositional design to guarantee properties beyond stability, such as safety and performance.},
	pages = {pp. 29-44},
	volume = {Vol. 100},
	number = {No. 1},
	journal = {Special Issue of the Proceedings of the IEEE}
}
@article {
	title = {Energy-efficient Source Authentication for Secure Group Communication with Low-Powered Smart Devices in Hybrid Wireless/Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2011},
	month = {12/2011},
	abstract = {In this paper, we describe a new class of lightweight, symmetric-key digital certificates called extended TESLA certificates and a source authentication protocol for wireless group communication that is based on the certificate. The certificate binds the identity of a wireless smart device to the anchor element of its key chain; keys from the chain are used for computing message authentication codes (MACs) on messages sourced by the device. The authentication protocol requires a centralized infrastructure in the network: we describe the protocol in a hybrid wireless network with a satellite overlay interconnecting the wireless devices. The satellite is used as the Certificate Authority (CA) and also acts as the proxy for the senders in disclosing the MAC keys to the receivers. We also design a probabilistic nonrepudiation mechanism that utilizes the satellite{\textquoteright}s role as the CA and sender proxy. Through analysis, we show that the authentication protocol is secure against malicious adversaries. We also present detailed simulation results that demonstrate that the proposed protocol is much cheaper than traditional public key-based authentication technologies for metrics like processing delay, storage requirements, and energy consumption of the smart devices.},
	pages = {pp. 1-19},
	volume = {vol. 2011},
	number = {Article ID  392529},
	journal = {EURASIP Journal on Wireless Communications and Networking Special Issue on Security and Resilience for Smart Devices and Applications}
}
@article {
	title = {Solving Multi-metric Network Problems: An Interplay Between Idempotent Semiring Rules},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2011},
	month = {10/2011},
	abstract = {We motivate computations in a multifunctional networked system as instances of algebraic path problems on labeled graphs. We illustrate, using examples, that composition operators used in many function computations in a networked system follow semiring axioms. We present an abstract framework, using a special idempotent semiring algebraic path problem, to handle multiple metrics for composition. We show that using different vector order relations in this abstract framework, we can obtain different rules of compositions such as Pareto, lexicographic and max-order efficiency. Under this framework, we identify a class of tractable composition rules that can be solved in different multi-criteria settings at affordable computational cost. We demonstrate using an example of trusted routing in which logical security rules of admission control can be combined with delay performance metrics in the multi-criteria optimization framework.},
	pages = {pp. 1494 -1512},
	volume = {Volume 435},
	number = {Issue 7},
	journal = {LAA Special Issue on the occasion of 1st Montreal Workshop on Idempotent and Tropical Mathematics}
}
@article {
	title = {Optimal State Estimation for Discrete-Time Markovian Jump Linear Systems, in the Presence of Delayed Output Observations},
	author = {Matei, Ion., Baras, John S.},
	year = {2011},
	month = {09/2011},
	abstract = {We investigate the design of optimal state estimators for Markovian Jump Linear Systems. We consider that the output observations and the mode observations are affected by delays not necessarily identical. Our objective is to design optimal estimators for the current state, given the current observations.We provide a solution to this paradigm by giving an optimal recursive estimator for the state, the probability in the minimum mean square sense, and a finitely parameterized recursive scheme the probability computing mass function of the current mode conditioned on the observed output. We also show that ifthe output delay is less then the one in observing the mode, then the optimal state estimation becomes nonlinear in the output observations.},
	pages = {pp. 2235 - 2240},
	volume = {Volume 56.},
	number = {Issue 9},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Performance Evaluation of the Consensus-based Distributed Subgradient Method Under Random Communication Topologies},
	author = {Matei, Ion., Baras, John S.},
	year = {2011},
	month = {08/2011},
	abstract = {We investigate the collaborative optimization of an objective function expressed as a sum of local convex functions, when the agents make decisions in a distributed manner using local information, while the communication topology used to exchange messages and information is modeled by a graph-valued random process, assumed independent and identically distributed. Specifically, we study the performance of the consensus-based multi-agent distributed subgradient method and show how it depends on the probability distribution of the random graph. For the case of a constant stepsize, we first give an upper bound on the difference between the objective function, evaluated at the agents{\textquoteright} estimates of the optimal decision vector, and the optimal value. Second, for a particular class of convex functions, we give an upper bound on the distances between the agents{\textquoteright} estimates of the optimal decision vector and the minimizer. In addition, we provide the rate of convergence to zero of the time varying component of the aforementioned upper bound. The addressed metrics are evaluated via their expected values. As an application, we show how the distributed optimization algorithm can be used to perform collaborative system identification and provide numerical experiments under the randomized and broadcast gossip protocols.},
	pages = {pp. 754-771},
	volume = {Volume 5.},
	number = {No. 4},
	journal = {IEEE Journal of Selected topics in Signal Processing}
}
@article {
	title = {Decentrailzed Coordination of Autonomous Swarms Using Parallel Gibbs Sampling},
	author = {Tan, Xiaobo., Xi, Wei., Baras, John S.},
	year = {2010},
	month = {12/2010},
	abstract = {In this paper, we present analysis of a discrete-time, decentralized, stochastic coordination algorithm for a group of mobile nodes, called an autonomous swarm, on a finite spatial lattice. All nodes take their moves by sampling in parallel their locally perceived Gibbs distributions corresponding to a pairwise, nearest-neighbor potential. The algorithm has no explicit requirements on the connectedness of the underlying information graph, which varies with the swarm configuration. It is established that, with an appropriate annealing schedule, the algorithm results in swarm configurations converging to the (global) minimizers of a modified potential energy function. The extent of discrepancy between the modified and original potential energy functions is determined by the maximum node travel between time steps, and when such distance is small, the ultimate swarm configurations are close to the global minimizers of the original potential energy. Simulation results are further presented to illustrate the capability of the sampling algorithm in approximate global optimization for swarms.},
	pages = {pp. 2068-2076},
	volume = {Volume 46},
	number = {Issue 12},
	journal = {Automatica}
}
@article {
	title = {Securing the Communication of Medical Information Using Local Biometric Authentication and Commercial Wireless Links},
	author = {Ivanov, Vladimir I., Yu, Paul L., Baras, John S.},
	year = {2010},
	month = {09/2010},
	abstract = {Medical information is extremely sensitive in nature {\textendash} a compromise, such as eavesdropping or tampering by a malicious third party, may result in identity theft, incorrect diagnosis and treatment, and even death. Therefore, it is important to secure the transfer of medical information from the patient to the recording system. We consider a portable, wireless device transferring medical information to a remote server. We decompose this problem into two sub-problems and propose security solutions to each of them:(1) to secure the link between the patient and the portable device, and(2) to secure the link between the portable device and the network. Thus we push the limits of the network security to the edge by authenticating the user using their biometric information; authenticating the device to the network at the physical layer, and strengthening the security of the wireless link with a key exchange mechanism. The proposed authentication methods can be used for recording the readings of medical data in a central database and for accessing medical records in various settings.},
	pages = {pp.  211-223},
	volume = {Volume 16},
	number = {Number 3},
	journal = {Health Informatics Journal}
}
@techreport {
	title = {Distributed Topology Control for Stable Path Routing in Multi-hop Wireless Networks},
	author = {Somasundaram, Kiran K., Baras, John S., Jain, Kaustubh., Tabatabaee, Vahid.},
	year = {2010},
	month = {07/2010},
	abstract = {In this paper, we introduce the topology control problem for stable path routing in mobile multi-hop networks. We formulate the topology control problem of selective linkstate broadcast as a graph pruning problem with restricted local neighborhood information. We develop a multi-agent optimization framework where the decision policies of each agent are restricted to local policies on incident edges and independent of the policies of the other agents. We show that under a condition called the positivity condition, these independent local policies preserve the stable routing paths globally. We then provide an efficient algorithm to compute an optimal local policy that yields a minimal pruned graph, which we call the Stable Path Topology Control (SPTC) algorithm. Using simulations, we demonstrate that this algorithm, when used with the popular ETX metric, has lesser control overhead and the resulting pruned routing paths carry more upper layer traffic when compared with other topology control mechanisms commonly used for Mobile Ad Hoc Networks.}
}
@techreport {
	title = {The asymptotic consensus problem on convex metric spaces},
	author = {Matei, Ion., Baras, John S.},
	year = {2010},
	month = {04/2010},
	abstract = {We consider the consensus problem of a group of dynamic agents whose communication network is modeled by a directed time-varying graph. In this paper we generalize the asymptotic consensus problem to convex metric spaces. A convex metric space is a metric space on which we define a convex structure. Using this convex structure we define convex sets and in particular the convex hull of a (finite) set. Under minimal connectivity assumptions, we show that if at each iteration an agent updates its state by choosing a point from a particular subset of the convex hull generated by the agent{\textquoteright}s current state and the states of his/her neighbors, then the asymptotic agreement is achieved. In addition, we give bounds on the distance between the consensus point(s) and the initial values of the agents. As application example, we use this framework to introduce an iterative algorithm for reaching consensus of opinion. In this example, the agents take values in the space of discrete random variable on which we define an appropriate metric and convex structure. For this particular convex metric space we provide a more detail analysis of the convex hull generated by a finite set points. In addition we give some numerical simulations of the consensus of opinion algorithm.}
}
@techreport {
	title = {Distributed Topology Control for Stable Path Routing in Mobile Ad Hoc Networks},
	author = {Somasundaram, Kiran K., Jain, Kaustubh., Tabatabaee, Vahid., Baras, John S.},
	year = {2010},
	month = {03/2010},
	abstract = {In this paper, we introduce the stable path topology control problem for routing in Mobile Ad Hoc Networks (MANETs). We formulate the problem as a constrained multiagent optimization problem with only local neighborhood information. We develop and prove local pruning strategies that solve this problem. We also introduce the notion of distorted pruning, which offers a systematic method to trade path stability off against the hop count metric. Finally, we quantify the performance of our pruning algorithms using several simulation scenarios.}
}
@techreport {
	title = {Path Optimization Techniques for Trusted Routing in Mobile Ad-Hoc Networks: An Interplay Between Ordered Semirings},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2010},
	month = {02/2010},
	abstract = {In this paper, we formulate the problem of trusted routing as a transaction of services over a complex networked environment. We present definitions from service-oriented environments which unambiguously capture the difference between trust and reputation relations. We show that the trustworthiness measures associated with these relations have a linear order embedded in them. Identifying this order structure permits us to treat the trusted routing problem as a bi-objective path optimization problem. Further, we present polynomial time solutions to obtain the optimal routing paths in various biobjective settings. In developing these algorithms, we identify an interesting semiring decomposition principle that yields a distributed solution.}
}
@techreport {
	title = {Pareto Nash Replies for Multi-Objective Games},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {11/2009},
	abstract = {We observe the notions of Pareto Nash strategies and their relations to multiparametric linear programming has made repeated appearances the game theory literature. . What we contribute . We feel that the theory of MOG has significant potential to model several practical scenarios especially in the context of networked communications}
}
@techreport {
	title = {Convergence Results for Ant Routing Algorithms via Stochastic Approximation},
	author = {Purkayastha, Punyaslok., Baras, John S.},
	year = {2009},
	month = {10/2009},
	abstract = {In this paper, we provide convergence results for an Ant-Based Routing (ARA) Algorithm for wireline, packet-switched communication networks, that are acyclic. Such algorithms are inspired by the foraging behavior of ants in nature. We consider an ARA algorithm proposed by Bean and Costa [2]. The algorithm has the virtues of being adaptive and distributed, and can provide a multipath routing solution. We consider a scenario where there are multiple incoming data traffic streams that are to be routed to their respective destinations via the network. Ant packets, which are nothing but probe packets, are introduced to estimate the path delays in the network. The node routing tables, which consist of routing probabilities for the outgoing links, are updated based on these delay estimates. In contrast to the available analytical studies in the literature, the link delays in our model are stochastic, time-varying, and dependent on the link traffic. The evolution of the delay estimates and the routing probabilities are described by a set of stochastic iterative equations. In doing so, we take into account the distributed and asynchronous nature of the algorithm operation. Using methods from the theory of stochastic approximations, we show that the evolution of the delay estimates can be closely tracked by a deterministic ODE (Ordinary Differential Equation) system, when the step-size of the delay estimation scheme is small. We study the equilibrium behavior of the ODE system in order to obtain the equilibrium behavior of the routing algorithm. We also explore properties of the equilibrium routing probabilities, and provide illustrative simulation results.}
}
@techreport {
	title = {Distributed subgradient method under random communication topology - the effect of the probability distribution of the random graph on the performance metrics},
	author = {Matei, Ion., Baras, John S.},
	year = {2009},
	month = {09/2009},
	abstract = {In this note we study the performance metrics (rate of convergence and guaranteed region of convergence) of a multi-agent subgradient method for optimizing a sum of convex functions. We assume that the agents exchange information according to a communication topology modeled as a random graph, independent of other time instances. Under a strong convexity type of assumption, we express the performance metrics directly as functions of the estimates of the optimal decision vector. We emphasize how the probability distribution of the random graph affects the upper bounds on the performance metrics. This provide a guide for tuning the parameters of the communication protocol such that good performance of the multi-agent subgradient method is ensured. We perform the tuning of the protocol parameters for two communication scenarios. In the first scenario, we assume a randomized scheme for link activation with no-error transmissions while in the second scenario we use a pre-established order of transmissions but we consider the interference effect. Both these scenarios are applied on a small world type of topology.}
}
@techreport {
	title = {Semiring Pruning for Information Dissemination in Mobile Ad Hoc Networks},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {08/2009},
	abstract = {Link state routing mechanisms have shown good convergence behaviour with mobile hosts. Pruning methods such as those used in Optimized Link State Routing (OLSR) have showed good throughput behaviour when compared to traditional link-state approaches which suffered from broadcast storm problems. In this paper, we show that the pruning function is a fundamental component of link-state routing protocols for mobile networks. We also show that this component architecture aids in interpreting both distance vector and link-state approaches under a common framework. We develop a class of pruning methods for many of the most commonly used routing objectives and show that these pruning methods are a special case of the semiring distribution property.}
}
@article {
	title = {Optimal Output Feedback Control Using Two remote Sensors Over Erasure Channels},
	author = {Gupta, Vijay., Martins, Nuno C., Baras, John S.},
	year = {2009},
	month = {07/2009},
	abstract = {Consider a discrete-time, linear time-invariant process, two sensors and one controller. The process is observed by the sensors, which are connected to the controller via links that can be modeled as erasure channels. If a link transmits successfully then a finite-dimensional vector of real numbers is conveyed from the sensor to the controller. If an erasure event occurs, then any information conveyed over the link is lost. This paper addresses the problem of designing the maps that specify the processing at the controller and at the sensors for stabilizing the process in the bounded second-moment sense. When the information is lost over the links either in an independent and identically distributed (i.i.d.) or Markovian fashion over time, we derive necessary and sufficient conditions for the existence of maps such that the process is stabilized. Such conditions are expressed as inequalities involving the parameters of the plant and the probabilities of link fading. and provide the least conservative stabilization conditions. We also indicate how our approach can be used if more than two sensors are available if the sensors can cooperate and if the acknowledgment signals are also transmitted over erasure channels. The analysis also carries over to the case when the single channels are replaced by networks of erasure channels.},
	pages = {pp. 1463-1476},
	volume = {Vol. 54},
	number = {Number 7},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Evaluation of Detection Algorithms for MAC Layer Misbehavior: Theory and Experiments},
	author = {Cardenas, Alvaro A., Radosavac, Svetlana., Baras, John S.},
	year = {2009},
	month = {04/2009},
	abstract = {We revisit the problem of detecting greedy behavior in the IEEE 802.11 MAC protocol by evaluating the performance of two previously proposed schemes: DOMINO and the Sequential Probability Ratio Test (SPRT). Our evaluation is carried out in four steps. We first derive a new analytical formulation of the SPRT that considers access to the wireless medium in discrete time slots. Then, we introduce an analytical model for DOMINO. As a third step, we evaluate the theoretical performance of SPRT and DOMINO with newly introduced metrics that take into account the repeated nature of the tests. This theoretical comparison provides two major insights into the problem: it confirms the optimality of SPRT and motivates us to define yet another test: a nonparametric CUSUM statistic that shares the same intuition as DOMINO but gives better performance. We finalize the paper with experimental results, con- firming the correctness of our theoretical analysis and validating the introduction of the new nonparametric CUSUM statistic.},
	pages = {pp. 605-617},
	volume = {Vol. 17},
	number = {No 2},
	journal = {IEEE/ACM Transactions on Networking (TON)}
}
@techreport {
	title = {Path Optimization Techniques for Trusted Routing in Tactical Mobile Ad-Hoc Networks},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {03/2009},
	abstract = {Over the past decade a lot of research effort has been invested in trying to understand security principles for Mobile Ad-Hoc Networks (MANETs). Among the various problems that the research community has focussed, a particularly interesting problem is that of trusted routing in MANETs. Unlike in traditional networks like the Internet, the information flow in a MANET is not restricted to a certain class of routing nodes. The MANETs are different in this sense, because every node acts as a potential relay node. Thus for the proper functioning of any higher layer protocols in MANETs it is of paramount importance that the mobile ad hoc nodes co-operate in routing and forwarding. In many practical scenarios where MANETs are deployed, it might be advantageous for individual nodes not to participate in this forwarding game. Thus one might expect under an unsupervised or unmonitored scenario, the network essentially breaks into components with similar interest groups. This raises the major issue of connectivity in a MANET which is a primitive requirement for the routing layer. Thus securing the network from self-interest groups is inherently coupled with the security of the routing layer. This particular observation has spawned several interesting works in the recent past.}
}
@article {
	title = {AVQRED in Satellite Networks},
	author = {Byun, Do Jun., Baras, John S.},
	year = {2009},
	month = {01/2009},
	abstract = {Due to exponential increases in internet traffic, Active Queue Management (AQM) has been heavily studied by numerous researchers. However, little is known about AQM in satellite networks. A microscopic examination on queueing behavior in satellite networks is conducted to identify problems with applying existing AQM methods. A new AQM method is proposed to overcome the problems and it is validated with a realistic emulation environment.},
	pages = {pp. 63-82},
	volume = {Vol.  44},
	journal = {Wireless Technology: Applications, Management and Security, Lecture Notes in Electrical Engineering.}
}
@article {
	title = {Game Theoretic Modeling of Malicious Users in Collaborative Networks},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2008},
	month = {09/2008},
	abstract = {If a network is to operate successfully, its users need to collaborate. Collaboration takes the form of following a network protocol and involves some resource expenditure on the part of the user. Therefore, users cannot automatically be expected to follow the protocol if they are not forced to. The situation is exacerbated by the presence of malicious users whose objective is to damage the network and increase the cost incurred by the legitimate users. The legitimate users are, at least initially, unaware of the type (legitimate or malicious) of the other users. Our contribution is a model for the strategic interaction of legitimate and malicious users as described above. The model is based on repeated graphical games with incomplete information. We describe and analyze two specific instantiations, aiming to demonstrate the model{\textquoteright}s expressive power and tractability. The main benefit we see from using game theory for this essential security problem is the ability to bound the damage caused by the malicious users.},
	pages = {pp.1317-1327},
	volume = {Vol. 26},
	number = {Issue. 7},
	journal = {IEEE Journal on Selected Areas in Communications}
}
@article {
	title = {An Analytic Framework for Modeling and Detecting Access Layer Misbehavior in Wireless Networks},
	author = {Radosavac, Svetlana., Moustakides, George V., Baras, John S., Koutsopoulos, Iordanis. },
	year = {2008},
	month = {07/2008},
	abstract = {The widespread deployment of wireless networks and hot spots that employ the IEEE 802.11 technology has forced network designers to put emphasis on the importance of ensuring efficient and fair use of network resources. In this work, we propose a novel framework for detection of intelligent adaptive adversaries in the IEEE 802.11 MAC by addressing the problem of detection of the worst-case scenario attacks. Utilizing the nature of this protocol we employ sequential detection methods for detecting greedy behavior and illustrate their performance for detection of least favorable attacks. By using robust statistics in our problem formulation, we attempt to utilize the precision given by parametric tests, while avoiding the specification of the adversarial distribution. This approach establishes the lowest performance bound of a given Intrusion Detection System (IDS) in terms of detection delay and is applicable in online detection systems where users who pay for their services want to obtain the information about the best and the worst case scenarios and performance bounds of the system. This framework is meaningful for studying misbehavior due to the fact that it does not focus on specific adversarial strategies and therefore is applicable to a wide class of adversarial strategies.},
	pages = {pp. 19.1 - 19.28},
	volume = {Vol. 11},
	number = {Issue 4, Article 19},
	journal = {ACM Transactions on Information and System Security}
}
@article {
	title = {Physical-Layer Authentication},
	author = {Yu, Paul L., Baras, John S., Sadler, Brian M.},
	year = {2008},
	month = {03/2008},
	abstract = {Authentication is the process where claims of identity are verified. Most mechanisms of authentication (e.g., digital signatures and certificates) exist above the physical layer, though some (e.g., spread-spectrum communications) exist at the physical layer
often with an additional cost in bandwidth. This paper introduces a general analysis and design framework for authentication at the
physical layer where the authentication information is transmitted concurrently with the data. By superimposing a carefully designed secret modulation on the waveforms, authentication is added to the signal without requiring additional bandwidth, as do spread-spectrum methods. The authentication is designed to be stealthy to the uninformed user, robust to interference, and secure for identity verification. The tradeoffs between these three goals are identified and analyzed in block fading channels. The use of the authentication for channel estimation is also considered, and an improved bit-error rate is demonstrated for time-varying channels. Finally, simulation results are given that demonstrate the potential application of this authentication technique.},
	pages = {pp. 38-51},
	volume = {Vol. 3},
	number = {No. 1},
	journal = {IEEE Transactions on Information Forensics and Security}
}
@article {
	title = {Application of Sequential Detection Schemes for Obtaining Performance Bounds of Greedy Users in the IEEE 802.11 MAC},
	author = {Radosavac, Svetlana., Baras, John S.},
	year = {2008},
	month = {02/2008},
	abstract = {The widespread deployment of wireless networks and hot spots that employ the IEEE 802.11 technology has forced network designers to put emphasis on the importance of ensuring efficient and fair use of network resources. In order to be able to evaluate the performance of the adversary, we define a set of security guarantees and requirements for an intrusion detection system and precisely define an adversary model. We then apply the proposed model for defining performance bounds of the worst case adversary and the quickest detection IDS in the IEEE 802.11 MAC.},
	pages = {pp. 148-154},
	volume = {Vol. 46},
	journal = {IEEE Communications Magazine special issue on Security in Mobile Ad Hoc and Sensor Networks}
}
@article {
	title = {Application of Sequential Detection Schemes for Obtaining Performance Bounds of Greedy Users in the IEEE 802.11 MAC},
	author = {Radosavac, Svetlana., Baras, John S.},
	year = {2008},
	month = {02/2008},
	abstract = {The widespread deployment of wireless networks and hot spots that employ the IEEE 802.11 technology has forced network designers to put emphasis on the importance of ensuring efficient and fair use of network resources. In order to be able to evaluate the performance of the adversary, we define a set of security guarantees and requirements for an intrusion detection system and precisely define an adversary model. We then apply the proposed model for defining performance bounds of the worst-case adversary and the quickest detection IDS in the IEEE 802.11 MAC.},
	pages = {pp. 148-154},
	volume = {Vol. 46},
	journal = {IEEE Communications Magazine special issue on Security in Mobile Ad Hoc and Sensor Networks}
}
@article {
	title = {An Optimal Distributed Routing Algorithm using Dual Decomposition Techniques},
	author = {Purkayastha, Punyaslok., Baras, John S.},
	year = {2008},
	month = {01/2008},
	abstract = {We consider the routing problem in wireline, packet-switched communication networks. We cast our optimal routing problem in a multicommodity network flow optimization framework. Our cost function is related to the congestion in the network and is a function of the flows on the links of the network. The optimization is over the set of flows in the links corresponding to the
various destinations of the incoming traffic. We separately address the single commodity and the multicommodity versions of the routing problem. We consider the dual problems and using dual decomposition techniques, we provide primal-dual algorithms that converge to the optimal solutions of the problems. Our algorithms, which are subgradient algorithms to solve the corresponding dual problems, can be implemented in a distributed manner by the nodes of the network. For online, adaptive implementations of our algorithms, the nodes in the network need to utilize {\textquoteleft}locally available information{\textquoteright} like estimates of queue lengths on outgoing links. We show convergence to the optimal routing solutions for synchronous versions of the algorithms, with perfect (noiseless) estimates of the queueing delays. Every node of the network controls the flows on the outgoing links using the distributed algorithms. For both the single commodity and multicommodity cases, we show that our algorithm converges to a loop-free optimal solution. Our optimal solutions also have the attractive property of being multipath routing solutions.},
	pages = {pp. 277-302},
	volume = {Vol. 8},
	number = {Issue 3},
	journal = {Communications in Information and Systems, Brockett Legacy Issue, International Press}
}
@techreport {
	title = {Sensor Scheduling using Smart Sensors},
	author = {Hovareshti, Pedram., Gupta, Vijay., Baras, John S.},
	year = {2007},
	month = {07/2007},
	abstract = {The sensor selection problem arises when multiple sensors are jointly trying to estimate a process but only a subset of them can take and/or use measurements at any time step. In a networked estimation situation, sensors are typically equipped with some memory and processing capabilities. We illustrate that utilization of these capabilities can lead to significant performance gains in the sensor selection problem for improved inference. Further, it also leads to significant pruning of the search tree that yields the optimum sensor schedule. We also present a periodicity result for the case where the decision is whether the sensor should transmit or not.}
}
@article {
	title = {Security and Trust for Wireless Autonomic Networks: System and Control Methods},
	author = {Baras, John S.},
	year = {2007},
	month = {03/2007},
	abstract = {We analyze and solve various problems of security information assurance and trust in dynamic wireless networks. These include detection and defense against attacks, detection of propagating viruses, evaluation of intrusion systems, attacks at the physical, MAC and routing protocols, trust establishment-dynamics-management. We demonstrate persistently that systems and control models and methodologies provide new and powerful techniques to analyze these problems. We describe the use of distributed change detection methods and algorithms for intrusion detection and the methods and the use of non-cooperative games for the detection and defense against attacks at all layers. We demonstrate how Bayesian decision theory can be used to evaluate problems in this area. We use game theoretic methods again to develop robust protocols against attacks, including Byzantine ones. We provide an in-depth investigation of trust establishment and computation in such networks. We describe various methods for distributed trust evaluation and the associated trust (and mistrust) {\textquoteright}spreading{\textquoteright} dynamics. We investigate rules and policies that establish {\textquoteright}trust-connected{\textquoteright} networks using only local interactions and find the parameters (e.g. topology type) that speed up or slow down this transition. We describe and explain the phase transition phenomena that we have found in these evolutions. We model the interactions among agents as cooperative games and show that trust can encourage agents to collaborate. This leads us to a fundamental analytical technique, constrained coalitional games, that can be used to evaluate tradeoffs in collaborative networks in various areas: communications, sensors, economics, sociology, biology. We also describe a model for trust evaluation that uses pairwise iterated graph games between the agents to create a {\textquoteright}trust reputation{\textquoteright} with evolution coupled to the game dynamics. Finally, we present a new modeling framework for trust metric evaluation as linear iterations over ordered semirings. This allows us to formulate problems of the resilience of trust metrics and trust evaluation to attacks.},
	pages = {pp. 105-133},
	volume = {Volume 13},
	number = {Number 2-3},
	journal = {European Journal of Control: Special Issue}
}
@article {
	title = {Detecting IEEE 802.11 MAC Layer Misbehavior in Ad Hoc Networks: Robust Strategies Against Individual and Colluding Attackers},
	author = {Radosavac, Svetlana., Cardenas, Alvaro A., Baras, John S., Moustakides, George V.},
	year = {2007},
	month = {01/2007},
	abstract = {Selfish behavior at the Medium Access (MAC) Layer can have devastating side effects on the performance of wireless networks, with effects similar to those of Denial of Service (DoS) attacks. In this paper we consider the problem of detection and prevention of node misbehavior at the MAC layer, focusing on the back-off manipulation by selfish nodes. We first propose an algorithm that ensures honest behavior of non-colluding participants. Furthermore, we analyze the problem of colluding selfish nodes, casting the problem within a minimax robust detection framework and providing an optimal detection rule for the worst-case attack scenarios. Finally, we evaluate the performance of single and colluding attackers in terms of detection delay. Although our approach is general and can be used with any probabilistic distributed MAC protocol, we focus our analysis on the IEEE 802.11 MAC.},
	pages = {pp.  103-128},
	volume = {Vol. 15},
	number = {No. 1},
	journal = {Journal of Computer Security: Special Issue on Security of Ad Hoc and Sensor Networks}
}
@article {
	title = {Gibbs Sampler-Based Self-Organization of Autonomous Swarms},
	author = {Xi, Wei., Tan, Xiaobo., Baras, John S.},
	year = {2006},
	month = {07/2006},
	abstract = {In this paper a novel, Gibbs sampler-based algorithm is proposed for coordination of autonomous swarms. The swarm is modeled as a Markov random field (MRF) on a graph with a time-varying neighborhood system determined by local interaction links. The Gibbs potential is designed to reflect global objectives and constraints. It is established that with primarily local sensing/communications, the swarm configuration converges to the global minimizer(s) of the potential function. The impact of the Gibbs potential on the convergence speed is investigated. Finally, a hybrid algorithm is developed to improve the efficiency of the stochastic scheme by integrating the Gibbs sampler-based method with the deterministic gradient-flow method. Simulation results are presented to illustrate the proposed approach and verify the analyses.},
	pages = {pp.  1107-1119},
	volume = {Vol. 42},
	number = {Issue 7},
	journal = {Automatica}
}
@article {
	title = {On Trust Models and Trust Evaluation Metrics for Ad-Hoc Networks},
	author = {Theodorakopoulos, George., Baras, John S.},
	year = {2006},
	month = {02/2006},
	abstract = {Within the realm of network security, we interpret the concept of trust as a relation among entities that participate in various protocols. Trust relations are based on evidence created by the previous interactions of entities within a protocol. In this work, we are focusing on the evaluation of trust evidence in ad hoc networks. Because of the dynamic nature of ad hoc networks, trust evidence may be uncertain and incomplete. Also, no preestablished infrastructure can be assumed. The evaluation process is modeled as a path problem on a directed graph, where nodes represent entities, and edges represent trust relations. We give intuitive requirements and discuss design issues for any trust evaluation algorithm. Using the theory of semirings, we show how two nodes can establish an indirect trust relation without previous direct interaction. We show that our semiring framework is flexible enough to express other trust models, most notably PGP{\textquoteright}s Web of Trust. Our scheme is shown to be robust in the presence of attackers.},
	pages = {pp. 318-328},
	volume = {Vol. 24},
	number = {Number 2},
	journal = {Journal of Selected Areas in Communications, Security in Wireless Ad-Hoc Networks [2007~IEEE Communications Society Leonard G. Abraham Prize]}
}
@article {
	title = {Multicast-Aware Power Allocation in Multiple Spot-Beam Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2006},
	month = {01/2006},
	abstract = {In this paper, we address the problem of user heterogeneity in satellite multicast from the perspective of resource allocation in a multiple spot-beam satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and direct access to a large number of users, clearly have an inherent advantage in supporting multicast applications. In order to remain competitive against other broadband technologies, however, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that user heterogeneity across spot-beam queues may result in lower allocated session rates for active flows, and be perceived as unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization-based approach that allocates resources with the goal of smoothing user heterogeneity and show that resulting session rates are higher on the average for both unicast and multicast flows. This is achieved through the re-distribution of system power among spot-beam queues, by taking into account the load on the queues and the channel states. We conclude that it is possible to increase the average session rates of multicast flows by 25{\textendash}100\%, and the rates of unicast flows by 15{\textendash}40\% compared to the pre-optimization levels.},
	pages = {pp. 49-71},
	volume = {Vol. 24},
	number = {Issue  1},
	journal = {International Journal of Satellite Communications}
}
@techreport {
	title = {Efficient Sampling for Keeping Track of an Ornstein-Uhlenbeck Process},
	author = {Rabi, Maben., Moustakides, George V.},
	year = {2006},
	month = {01/2006},
	abstract = {We consider estimation and tracking problems in sensor networks with constraints in the hierarchy of inference making, on the sharing of data and inter-sensor communications. We identify as a typical representative for such problems tracking of a process when the number and type of measurements in constrained. As the simplest representative of such problems, which still encompasses all the key issues involved we analyze efficient sampling schemes for tracking an Ornstein-Uhlenbeck process. We considered sampling based on time, based on amplitude (event-triggered sampling) and optimal sampling (optimal stopping). We obtained the solution in each case as a constrained optimization problem. We compare the performance of the various sampling schemes and show that the event-triggered sampling performs close to optimal. Implications and extensions are discussed.},
	number = {Number: ISR TR 2006-3}
}
@techreport {
	title = {Consensus Problems on Small World Graphs: A Structural Study},
	author = {Hovareshti, Pedram.},
	year = {2006},
	month = {01/2006},
	abstract = {Consensus problems arise in many instances of collaborative control of multi-agent complex systems; where it is important for the agents to act in coordination with the other agents. To reach coordination, agents need to share information. In large groups of agents the information sharing should be local in some sense, due to energy limitation, reliability, and other constraints. A consensus protocol is an iterative method that provides the group with a common coordination variable. However, local information exchange limits the speed of convergence of such protocols. Therefore, in order to achieve high convergence speed, we should be able to design appropriate network topologies. A reasonable conjecture is that the small world graphs should result in good convergence speed for consensus problems because their low average pairwise path length should speed the diffusion of information in the system. In this paper we address this conjecture by simulations and also by studying the spectral properties of a class of matrices corresponding to consensus problems on small world graphs.},
	number = {Number: ISR TR 2006-10}
}
@article {
	title = {Network Tomography},
	author = {Berenstein, Carlos A., Gavilanez, Franklin. , Baras, John S.},
	year = {2006},
	month = {01/2006},
	abstract = {While conventional tomography is associated to the Radon transform in Euclidean spaces, electrical impedance tomography, or EIT, is associated to the Radon transform in the hyperbolic plane. We discuss some recent work on network tomography that can be associated with a problem similar to EIT on graphs and indicate how in some sense it may be also associated to the Radon transform on trees.},
	pages = {pp. 11-17},
	volume = {Vol. 405},
	journal = {AMS Contemporary Mathematical Journal}
}
@techreport {
	title = {Detection of Greedy Individual and Colluding MAC Layer Attackers},
	author = {Radosavac, Svetlana., Cardenas, Alvaro A., Moustakides, George V.},
	year = {2006},
	month = {01/2006},
	abstract = {Selfish behavior at the Medium Access (MAC) Layer can have devastating side effects on the performance of wireless networks, with effects similar to those of Denial of Service (DoS) attacks. In this paper we consider the problem of detection and prevention of node misbehavior at the MAC layer, focusing on the back-off manipulation by selfish nodes. We propose an algorithm that ensures honest behavior of non-colluding participants. Furthermore, we analyze the problem of colluding selfish nodes, casting the problem within a minimax robust detection framework, providing a detection rule of optimum performance for the worst-case attack. Finally, we compare the effects of colluding attackers with a single attacker in terms of the detection delay. Although our approach is general and can serve as a guideline for the design of any probabilistic distributed MAC protocol, we focus our analysis on the IEEE 802.11 MAC.},
	number = {Number: ISR TR 2006-8}
}
@techreport {
	title = {Multiple Sampling for Estimation on a Finite Horizon},
	author = {Rabi, Maben., Moustakides, George V.},
	year = {2006},
	month = {01/2006},
	abstract = {We discuss some multiple sampling problems that arise in real-time estimation problems with limits on the number of samples. The quality of estimation is measured by an aggregate squared error over a finite horizon. We compare the performances of the best detereministic, level-triggered and the optimal sampling schemes. We restrict the signal to be either a Wiener process or an Ornstein-Uhlenbeck process. For the Wiener process, we provide closed form expressions and series expansions. For the Ornstein Uhlenbeck process, we provide procedures for numerical computation. Our results show that level-triggered sampling is almost optimal when the signal is stable.},
	number = {Number: ISR TR 2006-7}
}
@article {
	title = {Security Issues in Hybrid Networks with a Satellite Component},
	author = {Roy-Chowdhury, Ayan., Baras, John S., Hadjitheodosiou, Michael., Papademetriou, Spyro.},
	year = {2005},
	month = {12/2005},
	abstract = {Satellites are expected to play an increasingly important role in providing broadband Internet services over long distances in an efficient manner. Most future networks will be hybrid in nature {\textemdash} having terrestrial nodes interconnected by satellite links. Security is an important concern in such networks since the satellite segment is susceptible to a host of attacks, including eavesdropping, session hijacking, and data corruption. In this article, we address the issue of securing communication in satellite networks. We discuss various security attacks that are possible in hybrid satellite networks and survey the different solutions proposed to secure data communications in these networks. We look at the performance problems arising in hybrid networks due to security additions like Internet Security Protocol (IPSec) or Secure Socket Layer (SSL) and suggest solutions to performance-related problems. We also point out important drawbacks in the proposed solutions and suggest a hierarchical key-management approach for adding data security to group communication in hybrid networks.},
	pages = {pp. 50-61},
	volume = {Vol. 12},
	number = {Issue 6},
	journal = {IEEE Wireless Communications Magazine}
}
@article {
	title = {Network and Domain Autoconfiguration: A Unified Approach for Large Dynamic Networks},
	author = {Manousakis, Kyriakos., Baras, John S., McAuley, Anthony J., Morera, Raquel.},
	year = {2005},
	month = {08/2005},
	abstract = {Configuration management is critical to correct and efficient operation of large networks. Where the users and networks are dynamic and ad hoc, manual configuration quickly becomes too complex. The combination of the sheer number of nodes with heterogeneity and dynamics makes it almost impossible for the system administrator to ensure good configuration or even correct operation. To achieve the vision of pervasive computing, nodes must automatically discover their environment and self-configure, then automatically reconfigure to adapt to changes. Protocols such as DHCP, DDNS, and mDNS provide some degree of host autoconfiguration, but network administrators must still configure information such as address pools, routing protocols, and OSPF routing areas. Only limited progress has been made in automating the configuration of routers, servers, and network topology. We propose the first unified attempt to combine both self-configuration of much of the host, router, and server information with automatic generation and maintenance of hierarchy under the same algorithmic framework. Testbed implementations show the approach is practical, while simulations reveal its scalability, rapidity, and efficiency with respect to network performance.},
	pages = {pp. 78-85},
	volume = {Vol.  43},
	number = {Issue 8},
	journal = {IEEE Communication Magazine}
}
@techreport {
	title = {Hybrid Networks with a Space Segment - Topology Design and Security issues},
	author = {Roy-Chowdhury, Ayan., Hadjitheodosiou, Michael., Rentz, Nicolas.},
	year = {2005},
	month = {01/2005},
	abstract = {In this paper we investigate a hybrid network topology that is suitable for supporting interplanetary communications. We define an architecture comprised of a network of sensor nodes on a remote planetary surface, connected to a hybrid terrestrial network of wired and wireless LANs through a series of satellite relays. All the nodes in the network are IPaddressable and support public and symmetric key cryptography. The resulting network forms a hierarchical hybrid mesh that connects users on Earth to networks on or around a remote planetary surface. We describe the design of the network and present preliminary simulation results illustrating the network performance for various parameters. We also discuss how algorithms for user authentication, message integrity and data confidentiality can be incorporated in the network infrastructure for secure end-to-end communication.},
	number = {Number: CSHCN TR 2005-6}
}
@techreport {
	title = {Network Tomography},
	author = {Gavilanez, Franklin. , Berenstein, Carlos A., Baras, John S.},
	year = {2005},
	month = {01/2005},
	abstract = {While conventional tomography is associated to the Radon transform in Euclidean spaces, electrical impedance tomography or EIT is associated to the Radon transform in the hyperbolic plane. We discuss some recent work on network tomography that can be associated to a problem similar to EIT on graphs and indicate how in some sense it may be also associated to the Radon transform on trees.},
	number = {Number: ISR TR 2005-70}
}
@techreport {
	title = {A Certificate-Based Light-Weight Authentication Algorithm For Resource-Constrained Devices},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2005},
	month = {01/2005},
	abstract = {In this work, we analyze and extend a recently proposed design of digital certificates called TESLA certificates. Certificates are a necessary tool in today{\textquoteright}s secure networks to certify the identity of nodes taking part in communication. Most prevalent certificate technologies make use of public-key cryptography. Messages generated by the user are signed using its private key, and the signature can be verified by any node who knows the user{\textquoteright}s public key via its certificate. Signature generation and verification using public-key cryptography is computationally expensive for devices with limited computation power and energy resources. In this situation TESLA certificates can be very useful to certify identity, since they rely on symmetric cryptography which is computationally much more efficient. In this paper we explain the concept of TESLA certificates and provide a preliminary description of proposed modifications to the original algorithm to strengthen its security. We extend the original proposal by combining hash chains with TESLA certificates and come up with an efficient source and message authentication protocol based on symmetric key certificates. We also propose a new type of TESLA certificates called Group Certificates for use in multicast group communication. Through analysis, we show that our protocol is secure against malicious adversaries. We also give an initial estimate of the performance of our algorithm and the related comparison to public-key signatures, and we highlight network scenarios where the TESLA certificates could be particularly useful.},
	number = {Number: CSHCN TR 2005-4}
}
@techreport {
	title = {A Robust, Distributed TGDH-based Scheme for Secure Group Communications in MANETs},
	author = {Striki, Maria.},
	year = {2005},
	month = {01/2005},
	abstract = {Through our analysis and results we shed more insight on the actual feasibility of these protocols for MANETs and provide more realistic and {\textquotedblleft}fair{\textquotedblright} comparison results that more accurately advocate the pros and cons of each protocol over the environment of interest.},
	number = {Number: CSHCN TR 2005-9}
}
@techreport {
	title = {Interactive Data Services in Wireless Access Networks: Capacity Planning and Protocols},
	author = {Zhou, Xiaoming., Raissi-Dekhordi, Majid.},
	year = {2005},
	month = {01/2005},
	abstract = {In this paper, we study the capacity planning in wireless access network for interactive data services such as web browsing. A closed queuing model has been developed which can capture the bottleneck effects in both the forward and the reverse channels. The model can be used to calculate the average throughput, the average response time and the number of users the system can support. We evaluate the performance of several MAC protocols such as slotted Aloha, static TDMA, Aloha/periodic stream and combined free demand assignment multiple access (CFDAMA) using realistic web traffic models. Based on the performance evaluation, we propose a new MAC protocol and a new transport layer protocol. Our new MAC protocol called combined polling free demand assignment multiple access (CPFDAMA) explores the correlation between forward channel data packets and reverse channel acknowledgement packets. Our new transport layer protocol called RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion management. RWBP can eliminate congestion losses inside the wireless networks. Our protocol suite outperforms the proposed protocols in term of both channel utilization and response time. Our results can be used for service providers to dimension their networks and provide quality of service to a certain number of users.},
	number = {Number: CSHCN TR 2005-5}
}
@techreport {
	title = {Fault-Tolerant Extension of Hypercube Algorithm for Efficient, Robust Group Communications in MANETs},
	author = {Striki, Maria.},
	year = {2005},
	month = {01/2005},
	abstract = {Securing multicast communications in Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless networking and security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security on the other hand, is becoming an indispensable requirement of our modern life for all these applications. However, the limitations of the dynamic, infrastructure-less nature of MANETs impose major difficulties in establishing a secure framework suitable for group communications. The design of efficient key management (KM) schemes for MANET is of paramount importance, since the performance of the KM functions (key generation, entity authentication, key distribution/agreement) imposes an upper limit on the efficiency and scalability of the whole secure group communication system. In this work, we contribute towards efficient, robust and scalable, secure group communications for MANETs, by extending an existing key agreement (KA) scheme (where all parties contribute equally to group key generation) {\textendash}Hypercube - to tolerate multiple member failures with low cost, through its integration with a novel adaptively proactive algorithm. We assume that the participating users have already been authenticated via some underlying mechanism and we focus on the design and analysis of a fault-tolerant Hypercube, with the aim to contribute to the robustness and efficiency of Octopus-based schemes (an efficient group of KA protocols for MANETs using Hypercube as backbone). We compare our algorithm with the existing approach, and we evaluate the results of our analysis. Through our analysis and simulation results we demonstrate how the new Hypercube algorithm enhances the robustness of the Octopus schemes maintaining their feasibility in MANETs at the same time.},
	number = {Number: CSHCN TR 2005-108}
}
@article {
	title = {Transport Protocols in Multicast via Satellite},
	author = {Akkor, Gun., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2004},
	month = {11/2004},
	abstract = {In a wide variety of broadband applications, there is a need to distribute information to a potentially large number of receiver sites that are widely dispersed from each other. Communication satellites are a natural technology option and are extremely well suited for carrying such services because of the inherent broadcast capability of the satellite channel. Despite the potential of satellite multicast, there exists little support for multicast services over satellite networks. Although several multicast protocols have been proposed for use over the Internet, they are not optimized for satellite networks. One of the key multicast components that are affected when satellite networks are involved in the communication is the transport layer. In this paper, we attempt to provide an overview of the design space and the ways in which the network deployment and application requirements affect the solution space for transport layer schemes in a satellite environment. We also highlight some of the issues that are critical in the development of next generation satellite multicast services.},
	pages = {pp. 611-627},
	volume = {Vol. 22},
	number = {No. 6},
	journal = {International Journal of Satellite Communication}
}
@article {
	title = {Broadband Communication Support for Earth Observation from the International Space Station},
	author = {Nguyen, Alex T., Hadjitheodosiou, Michael., Baras, John S.},
	year = {2004},
	month = {10/2004},
	abstract = {In order to support the communications needs of Earth-observing instruments on the International Space Station (ISS), alternative communications architectures to provide broadband support need to be considered. In this paper, we evaluate the direct-to-ground option in terms of coverage. We show that a direct-to-ground option is a feasible solution to enhance the limited communication capabilities provided by the current ISS infrastructure. In order to ensure efficient end-to-end communication support and deal with the complications of the space environment, COTS equipment with recently demonstrated protocol modifications needs to be adopted. We also demonstrate that selecting the most appropriate location for placement of the ground stations is an important design issue that can ensure optimal coverage and maximize throughput. As both the need for broadband services from the ISS and from other upcoming space missions increases, this option will play a role in enhancing the currently limited space-relay architecture until a next generation relay system is deployed.},
	pages = {pp. 375-388},
	volume = {Vol. 46},
	number = {Issue 3},
	journal = {Computer Networks Journal}
}
@article {
	title = {Continuous and Discrete Inverse Conductivity Problems},
	author = {Baras, John S., Berenstein, Carlos A., Gavilanez, Franklin. },
	year = {2004},
	month = {06/2004},
	abstract = {Tomography using CT scans and MRI scans in now well-known as a medical diagnostic tool which allows for detection of tumors and other abnormalities in a noninvasive way, providing very detailed images of the inside of the body using low-dosage X-rays and magnetic fields. They have both also been used for determination of material defects in moderate size objects. In medical and other applications they complement conventional tomography. There are many situations where one wants to monitor the electrical conductivity of different portions of an object, for instance, to find out whether a metal object, possibly large, has invisible cracks. This kind of tomography, usually called Electrical Impedance Tomography or EIT, has also medical applications like monitoring of blood flow. While CT and MRI are related to Euclidean geometry, EIT is closely related to hyperbolic geometry. A question that has arisen in the recent past is whether there are similar "tomographic" methods to monitor the "health" of networks. Our objective is to explain how EIT ideas can in fact effectively be used in this context.},
	pages = {pp. 33-51},
	volume = {Vol. 362},
	journal = {American Mathematical Society, Contemporary Mathematics}
}
@article {
	title = {Modeling Multi-Dimensional QoS: Some Fundamental Constraints},
	author = {Liu, Nelson X., Baras, John S.},
	year = {2004},
	month = {04/2004},
	abstract = {In this paper, we model multi-dimensional QoS in a unified framework and study some fundamental constraints from the network and the traffic on realizing multiple QoS goals. Multidimensional QoS requirements are quantitatively represented using a QoS region. Based on the theory of effective bandwidths, the framework connects the throughput, the delay, and the loss rate in a uniform formula. Important traffic and network factors, namely, the burst size and the link speed are involved. With this framework, it is found that the burst size sets a hard limit on the QoS region that can be achieved and that the matching between the link speed and the node processing power can greatly improve the limit. It is also made clear that while pure load imbalance among links does not affect the QoS region, the heterogeneities of burst size or link speed may severely degrade the QoS performance. Applying the theory to real-time services in differentiated services architecture, we show it provides a useful tool for QoS prediction and network dimensioning.},
	pages = {pp. 193-215},
	volume = {Vol. 17},
	journal = {International Journal of Communication Systems}
}
@article {
	title = {Fixed Point Approximation for Multirate Multihop Loss Networks With State-Dependent Routing},
	author = {Liu, Mingyan., Baras, John S.},
	year = {2004},
	month = {04/2004},
	abstract = {In this paper, we consider a class of loss networks that have arbitrary topologies and routes of arbitrary length. Multiple traffic classes are present, each with different bandwidth requirement, and each routed according to a state-dependent routing scheme. In particular, we consider the least loaded routing method generalized to routes of an arbitrary number of hops. The connection level performance metric of interest is the end-to-end blocking probability. We are interested in developing fast evaluation methods to provide reasonably accurate estimates of the blocking probability, especially under heavy traffic load. Our algorithms are based on the fixed-point method framework, also known as the reduced load approximation. In addition to what commonly examined by previous work, two more factors contribute to the complexity of the computation in the scenario under consideration in this paper. One is the state-dependent nature of the routing mechanism, the other is the possible overlapping between routes due to the general multihop topology of the network. We present two fast approximation algorithms to evaluate the blocking probability with state-dependent routing by simplifying the route overlapping computation. We discuss the computational complexity of our algorithms as well as sources of approximation error.We then compare the numerical results with that of simulation and show that our algorithms provide fairly accurate blocking probability estimates especially under heavy traffic load.},
	pages = {pp. 361- 374},
	volume = {Vol. 12},
	number = {No. 2},
	journal = {IEEE/ACM Transactions on Networking}
}
@techreport {
	title = {A Multiple Subset Sum Formulation for Feedback Implosion Suppression over Satellite Networks},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {In this paper, we present a feedback implosion suppression (FIS) algorithm that reduces the volume of feedback information transmitted through the network without relying on any collaboration between users, or on any infrastructure other than the satellite network. Next generation satellite systems that utilize the Ka frequency band are likely to rely on various fade mitigation (compensation) techniques ranging from adaptive coding to dynamic power control, in order to guarantee a service quality that is comparable to other broadband technologies. User feedback would be a valuable input for a number of such components, however, collecting periodic feedback from a large number of users would result in the well-known feedback implosion problem. Feedback implosion is identified as a major problem when a large number of users try to transmit their feedback messages through the network, holding up a significant portion of the uplink resources and clogging the shared uplink medium. In this paper, we look at a system where uplink channel access is organized in time-slots. The goal of the FIS algorithm is to reduce the number of uplink time-slots hold up for the purpose of feedback transmission. Our analysis show that the FIS algorithm effectively suppresses the feedback messages of 95\% of all active users, but still achieves acceptable performance results when the ratio of available time-slots to number of users is equal to or higher than 5\%.},
	number = {Number: CSHCN TR 2004-21}
}
@techreport {
	title = {Providing Full Connectivity in Large Ad-Hoc Networks by Dynamic Placement of Aerial Platforms},
	author = {Karthikeyan Chadrashekar, Raissi-Dekhordi, Majid.},
	year = {2004},
	month = {01/2004},
	abstract = {In this paper we address the problem of providing full connectivity to disconnected ground MANET nodes by dynamically placing unmanned aerial vehicles (UAVs) to act as relay nodes. We provide a heuristic algorithm to find the minimal number of such aerial vehicles required to provide full connectivity and find the corresponding locations for these aerial platforms (UAVs). We also track the movement of the ground nodes and update the location of the UAVs. We describe a communication framework that enables the ground nodes to communicate with its peer ground nodes as well as the UAVs that act as relay nodes. The communication architecture is designed to work with existing MANET routing protocols.},
	number = {Number: CSHCN TR 2004-11}
}
@techreport {
	title = {An Analysis of Delay-Constrained Opportunistic Scheduling for Cellular Wireless Systems},
	author = {Srinivasan, Roshni.},
	year = {2004},
	month = {01/2004},
	abstract = {In this work, we focus primarily on the trade-off between the realization of multiuser diversity gain and the provision of delay guarantees. Our main contribution is an analytical characterization of the distributions of the delay and rate offered by an opportunistic scheduler. The scheduling metric used in the algorithm combines the rate requested by the user and scheduling delay in a general form. Our analysis of a wireless system with a finite number of users in discrete time is strongly supported by system simulations of a time-slotted cellular downlink shared by multiple mobile users with independent, fading channels. We also compute closed form expressions for the scheduler statistics using a continuous approximation. The results in this paper can be used to evaluate system performance and provision resources to support Quality of Service (QoS) guarantees in broadband wireless networks.},
	number = {Number: CSHCN TR 2004-2}
}
@techreport {
	title = {Web access over a multiple access channel: evaluations and improvements},
	author = {Zhou, Xiaoming., Liu, Nelson X.},
	year = {2004},
	month = {01/2004},
	abstract = {We evaluate web browsing performance over a multiple access satellite channel for three different MAC layer protocols. A web user behavior model is used to generate realistic source traffic. A new transport layer protocol called RWBP is proposed to solve the TCP problems inside satellite networks. RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion control. We compare its performance with TCP over the three multiple access protocols. Our simulation results show that RWBP can reduce the multiple access channel load and at the same time improve the web page response time when driven by realistic web traffic. For the MAC layer protocols, combined free demand assignment multiple access (CFDAMA) always performs better than the other two protocols.},
	number = {Number: CSHCN TR 2004-10}
}
@techreport {
	title = {Multicast-aware Power Allocation in Multiple Spot-Beam Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We address the problem of optimizing resource sharing and flow control in a multiple spot-beam broadband satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and direct access to large number of users, clearly have an inherent advantage in supporting multicast applications. In order to remain competitive against other broadband technologies, however, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that, in a multiple spot-beam system, a high load variation across spot-beam queues may force lower allocated session rates for active flows, and be perceived as unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization framework for balancing the spot-beam queue service rates such that the sum of the rate variances of all active multicast flows is minimized. This is achieved through the re-distribution of system power among spot-beam queues, by taking into account the load on the queues and the channel states. We conclude that it is possible to increase the average session rates of multicast flows by up to 16\%, and the rates of unicast flows by up to 4\% after this optimization is applied.},
	number = {Number: CSHCN TR 2004-19}
}
@techreport {
	title = {A Multichannel Random Access Protocol for Multislot Short Messages with Delay Constraints},
	author = {Zhou, Xiaoming.},
	year = {2004},
	month = {01/2004},
	abstract = {A multichannel random access protocol called FMCSA for multislot short messages is proposed in this paper to be used in access networks with large propagation delay. This protocol combines random access with the use of packet level forward error correction coding for new messages and scheduled retransmissions for partially received messages. Analytical and simulation results show that FMCSA can achieve a higher throughput and lower delay than slotted Aloha. When the system is operating at the low load region, the short messages can be delivered in their first attempts with very high probability. With the load increasing, more messages will be received partially in their first attempts and the scheduled retransmission scheme will guarantee the partially received messages to be recovered in their second attempts. Therefore the delay performance of FMCSA is much more robust to the load fluctuation than slot Aloha.},
	number = {Number: CSHCN TR 2004-14}
}
@techreport {
	title = {Load balancing in multi-beam satellite systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We propose an approach to optimize resource sharing and in a multi-beam broadband satellite system that supports both unicast and multicast flows. We show that in this architecture, the load on every spot-beam queue could be different, depending on the type of the flows and the distribution of the receivers across spot-beam coverage areas. This load unbalance may significantly under-utilize the system resources and decrease the system throughput when both unicast and multicast flows are active in the system. In this paper, we formulate an optimization problem for intra- and inter-beam resource sharing such that the variance of the session rates experienced by users of a flow located in different beam coverage areas is minimized. The result of our resource allocation also determines the maximum sustainable rate of each flow. We calculate the beam utilization and maximum sustainable sessions rates with and without optimization and compare the results. We conclude that this method significantly improves the session rates and overall utilization of the system when both unicast and multicast flows are active.},
	number = {Number: CSHCN TR 2004-9}
}
@techreport {
	title = {Power Balancing in Multiple Spot-Beam Satellite Systems for Multicast Support},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We address the problem of optimizing resource sharing and flow control in a multiple spot-beam broadband satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and ubiquitous access to large number of users, clearly have an inherent advantage in supporting distributed applications that require concurrent transmission of content to multiple users. In order to remain competitive against other broadband technologies, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that a high load variation across the spot-beam queues may significantly under-utilize the system and be perceived unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization based-approach to balance the load in the system and conclude that it is possible to increase the average session rates of all active flows by up to 30\% after this optimization is applied.},
	number = {Number: CSHCN TR 2004-15}
}
@article {
	title = {An Implementation Study of Multicast Extensions of AODV},
	author = {Dharmaraju, Dinesh., Karir, Manish., Das, Subir., Baras, John S.},
	year = {2003},
	month = {11/2003},
	abstract = {In this paper, we describe our experience of implementing multicast extensions of AODV (MAODV). Using insight gained from our implementation we propose some enhancements to MAODV that enhance its stability and its performance. We propose the use of a tree optimization scheme based on Group Hello messages, a scheme for merging group partitions, as well as a method to add reliability to the multicast tree formation and maintenance, via the use of an acknowledgment for MACT messages. Our implementation is based on the kernel AODV implementation from NIST. We describe details regarding our implementation that can provide valuable insight to future implementers of ad hoc routing protocols, and in particular, people attempting to implement multicast routing protocols. We also provide a brief description of some basic validation experiments that we used to verify the functionality and the various features of our implementation.},
	volume = {Vol. 46},
	number = {Issue 3},
	journal = {International Journal of Communication}
}
@techreport {
	title = {Multicast Routing in Mobile Ad Hoc Networks Using Source Grouped Flooding},
	author = {Chandrashekar, Karthikeyan.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we address the multicast routing problem for mobile ad hoc networks (MANETs). We present the Source Grouped Flooding approach to achieve multicast in MANETs. The protocol creates multiple multicast routes between the source and group members based on hop count distance constraints. We also propose a probabilistic data forwarding mechanism to achieve efficient data dissemination. The protocol aims to achieve the robustness of flooding and data distribution efficiency of tree based protocols. Simulation results verify performance.},
	number = {Number: CSHCN TR 2003-6}
}
@techreport {
	title = {A Feedback Implosion Suppression Algorithm for Satellite Reliable Multicast},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we propose a knapsack-based feedback suppressionalgorithm for reliable multicast transport protocols operating over asatellite network. A reliable transport protocol needs to identify thepackets which failed to reach a given destination. This is achievedthrough feedback packets returned to the source. For multicastservices, receiver feedback has been shown to lead to thefeedback implosion problem. Feedback implosion is awell-studied problem and various solutions exist in the literature.However, these solutions mainly focus on wireline terrestrial networksand do not take into account the inherent characteristics of thesatellite channel and the architecture of the deployed network.Therefore, we need to revisit the problem and provide a new set ofsolutions for efficient integration to next generation satellitesystems. In this paper, we introduce a feedback implosion suppressionalgorithm, which effectively suppresses the amount of feedback relayedthrough the satellite channel, while ensuring that the criticalinformation is conveyed in a timely fashion. The performance of thealgorithm is evaluated through simulations.},
	number = {Number: CSHCN TR 2003-3}
}
@techreport {
	title = {Congestion management in access networks with long propagation delay},
	author = {Zhou, Xiaoming.},
	year = {2003},
	month = {01/2003},
	abstract = {Satellite networks are going to play an important role in the global information infrastructure. Satellites can be used to provide Internet services to fixed users and to mobile users. However, recent measurements show that the satellite link efficiency is only about 30\%. In order to improve the performance of Internet over satellite, a new protocol called Receiver Window Backpressure Protocol (RWBP) is proposed. RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion management. Simulation results show that RWBP can maintain high utilization of the satellite link and improve fairness among the competing connections.},
	number = {Number: CSHCN TR 2003-23}
}
@techreport {
	title = {Dynamical Properties of TCP System with AQM Routers},
	author = {Chen, Huigang., Liu, Nelson X.},
	year = {2003},
	month = {01/2003},
	abstract = {In this report we discuss the dynamics of heterogeneous TCP systems with propagation delays. Instead of studying the local linearized TCP dynamics, we study the global stability conditions and obtain the stability regions. Also we provide proof of periodic behavior of a single TCP connection when stability conditions are not met.},
	number = {Number: CSHCN TR 2003-22}
}
@techreport {
	title = {Jitter Analysis of CBR Streams in Multimedia Networks},
	author = {Jou,  Jia-Shiang.},
	year = {2003},
	month = {01/2003},
	abstract = {The performance of real time applications such as video andvoice streams relies on packet delay jitter. Large delay jittercauses buffer overflow or underflow at the receiver end and theuser encounters interrupts. The delay jitter is mainly due to theperturbation of background traffic in the bottleneck router.Fulton and Li provide an analytical approximationfor the first-order and second-order statistics of delay jitter.However, their analysis is based on a Markovian model of thebackground traffic, which is not quite suitable for Internettraffic and requires lots of computational effort. We propose anefficient method to predict the jitter variance of a CBR(constant-bit rate) connection based on the wavelet model of thebackground traffic. The wavelet analysis extracts the statisticalproperties of background traffic and the analysis result can beused to predict an upper bound for the jitter variance of the CBRconnection.},
	number = {Number: CSHCN TR 2003-11}
}
@techreport {
	title = {A Parallel Virtual Queue Structure for Active Queue Management},
	author = {Jou,  Jia-Shiang., Tan, Xiaobo.},
	year = {2003},
	month = {01/2003},
	abstract = {The performance of the Adaptive RED scheme is susceptible to bursty web traffic. In this paper a parallel virtual queue structure is proposed for active queue management at the bottleneck router. Real time connections such as web and UDP, and non-real time connections such as FTP are served in two different virtual queues with drop-tail and Adaptive RED policies, respectively. Both queues share the same physical buffer memory. Simulation shows that file delivery for the web traffic is greatly improved due to shorter packet delay and lower packet loss rate, and that the queue length variation for the FTP traffic is small. To improve the goodput of the non-real time connections, a modified Adaptive RED scheme with dynamic queue length thresholds is also proposed. This scheme is able to keep the packet dropping probability within a desired small region. Stability of the queue length under this scheme is studied through analysis and numerical computation.},
	number = {Number: CSHCN TR 2003-18}
}
@techreport {
	title = {Key Distribution Protocols for Multicast Group Communication in MANETs},
	author = {Striki, Maria.},
	year = {2003},
	month = {01/2003},
	abstract = {In this work we will attempt to combine these protocols with all the possible combinations into a two-layered hybrid scheme that exploits adavantages of both protocols and reduces possibly their overhead. We will develop models of these combinations, redefine their function principles and we will do a mathematical analysis to derive all costs. The analytical formulae of these models will provide us with the tools for comparisons among them, and push the research towards the best behaving models.},
	number = {Number: CSHCN TR 2003-10}
}
@article {
	title = {On the Performance Limits of the Data-Aided Synchronization},
	author = {Jiang, Yimin., Sun, Feng-Wen., Baras, John S.},
	year = {2003},
	month = {01/2003},
	abstract = {This paper addresses data-aided (DA) synchronization, in which the reference parameter acquisition is aided by a training sequence known to the receiver. The Cramer{\textendash}Rao lower bound (CRB) for the DA timing and/or carrier phase recovery is presented. For DA parameter estimation, the CRB typically varies with the training sequence. This indicates that different training sequences offer fundamentally different performance. In the literature, the widely cited closed-form CRB for timing and carrier phase recovery was derived under the assumption that the training sequence is independent and identically distributed (i.i.d.) and sufficiently long. In this paper, we derive a closed-formCRBfor timing and carrier phase recovery with respect to an arbitrary training sequence and pulse shaping function for the over and under sampling cases. It turns out that theCRBis a weighted summation of the aperiodic correlation of the training sequence and the weighting factor is determined by the pulse shaping filter. Therefore, this paper reveals the fundamental link between a training sequence and its corresponding performance limit.},
	pages = {pp. 191-203},
	volume = {Vol. 49},
	number = {No.1},
	journal = {IEEE Transactions on Information Theory}
}
@techreport {
	title = {A Reliable Multicast Transport Protocol for Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we propose a reliable multicast transport protocol for satellite communication systems. Many of the emerging applications in the Internet would benefit from reliable multicast services, and broadband satellite communication systems have attractive characteristics for supporting such services. However, many of the protocols designed primarily for terrestrial networks do not perform well over satellite networks. Therefore, it is necessary to look at the problem of reliable multicast in the solution space of satellite communications. Our protocol makes use of a special form of forward error correcting codes and couples it with an adaptive window based control mechanism to dynamically adjust the number of encoding packets forwarded to the users. Protocol makes very good use of the broadcast nature of the satellite channel and attempts to minimize the feedback from users. We evaluate the protocol performance by extensive computer simulations.},
	number = {Number: CSHCN TR 2003-17}
}
@techreport {
	title = {Detection and Classification of Network Intrusions using Hidden Markov Models},
	author = {Radosavac, Svetlana.},
	year = {2003},
	month = {01/2003},
	abstract = {This paper demonstrates that it is possible to model attacks witha low number of states and classify them using Hidden MarkovModels with very low False Alarm rate and very few FalseNegatives. We also show that the models developed can be used forboth detection and classification. We put emphasis on detectionand classification of network intrusions and attacks using HiddenMarkov Models and training on anomalous sequences. We test severalalgorithms, apply different rules for classification and evaluatethe relative performance of these. Several of the attack examplespresented exploit buffer overflow vulnerabilities, due toavailability of data for such attacks. We emphasize that thepurpose of our algorithms is not only the detection andclassification of buffer overflows; they are designed fordetecting and classifying a broad range of attacks.},
	number = {Number: CSHCN TR 2003-6}
}
@article {
	title = {Run-to-Run Control Methods Based on the DHOBE Algorithm},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2003},
	month = {01/2003},
	abstract = {Since process models are typically not known exactly in real problems, it is important to estimate the process parameters before one applies the optimal control to a process. In this paper, the Dasgupta{\textendash}Huang optimal bounding ellipsoid (DHOBE) algorithm is employed to estimate process parameters in semiconductor process run-to-run (RtR) control. At each iteration, the DHOBE algorithm returns an outer bounding ellipsoid of the likely process parameter set. If the vector center of the ellipsoid is taken as the estimate of the process parameter vector, then a model-reference controller results; if the vector within the ellipsoid that produces the worst expected cost is taken as the process parameter estimate, then a worst-case controller results. These two methods are compared with other RtR control schemes: the exponentially weighted moving average (EWMA) method and the optimizing adaptive quality controller (OAQC). Simulation results show that the performance of the model-reference RtR controller based on the DHOBE algorithm is comparable to or better than that of the other two RtR controllers in some specific examples of semiconductor processes.},
	pages = {pp. 35-45},
	volume = {Vol.  39},
	number = {Issue 1},
	journal = {Automatica}
}
@article {
	title = {On the Convergence of the Inverse of Toeplitz Matrices and its Applications},
	author = {Sun, Feng-Wen., Jiang, Yimin., Baras, John S.},
	year = {2003},
	month = {01/2003},
	abstract = {Many issues in signal processing involve the inverses of Toeplitz matrices. One widely used technique is to replace Toeplitz matrices with their associated circulant matrices, based on the well-known fact that Toeplitz matrices asymptotically converge to their associated circulant matrices in the weak sense. This often leads to considerable simplification. However, it is well known that such a weak convergence cannot be strengthened into strong convergence. It is this fact that severely limits the usefulness of the close relation between Toeplitz matrices and circulant matrices. Observing that communication receiver design often needs to seek optimality in regard to a data sequence transmitted within finite duration, we define the finite-term strong convergence regarding two families of matrices. We present a condition under which the inverses of a Toeplitz matrix converges in the strong sense to a circulant matrix for finite-term quadratic forms. This builds a critical link in the application of the convergence theorems for the inverses of Toeplitz matrices since the weak convergence generally finds its usefulness in issues associated with minimum mean squared error and the finite-term strong convergence is useful in issues associated with the maximum-likelihood or maximum a posteriori principles.},
	pages = {pp. 180-190},
	volume = {Vol. 49},
	number = {No. 1},
	journal = {IEEE Transactions on Information Theory}
}
@techreport {
	title = {Decentralized Control of Autonomous Vehicles},
	author = {Tan, Xiaobo., Hovareshti, Pedram.},
	year = {2003},
	month = {01/2003},
	abstract = {Decentralized control methods are appealing in coordination ofmultiple vehicles due to their low demand for long-range communication and their robustness to single-point failures. An important approach in decentralized multi-vehicle control involves artificial potentials or digital pheromones. In this paper we explore a decentralized approach to path generation for a group of combat vehicles in a battlefield scenario. The mission is to maneuver the vehicles to cover a target area. The vehicles are required to maintain good overall area coverage, and avoid obstacles and threats during the maneuvering. The gradient descent method is used, where each vehicle makes its moving decision by minimizing a potential function that encodes information about its neighbours, obstacles, threats and the target. We conduct analysis of vehicle behaviors by studying the vector field induced by the potential function. Simulation has shown that this approach leads to interesting emergent behaviors, and the behaviors can be varied by adjusting the weighting coefficientsof different potential function terms.},
	number = {Number: CSHCN TR 2003-8}
}
@techreport {
	title = {Jointly Optimal Quantization, Estimation, and Control of Hidden Markov Chains},
	author = {Tan, Xiaobo., Xi, Wei.},
	year = {2003},
	month = {01/2003},
	abstract = {It is of interest to understand the tradeoff between the communication resource comsumption and the achievable system performance in networked control systems. In this paper we explore a general framework for trade-off analysis and decision making in such systems by studying joint quantization,estimation, and control of a hidden Markov chain. We first formulate the joint quantization and estimation problem, where vector quantization with variable-block length is considered. Dynamic programming (DP) is used to find the optimal quantization scheme that minimizes a weighted combination of the estimation error, the communication cost, and the delay due to block coding. The DP equation issolved numerically and simulation shows that this approach is able to capture the tradeoffs among competing objectives by adjusting the cost weights. We then study the joint quantization and control problem. An example problem is solved analytically, which provides interesting insight into the approach. In both the joint quantization/estimation problem and the joint quantization/control problem, we show that the separation principle holds. The approaches to solving these two problemsshare the same spirit, and can be combined and extended to accomodate more objectives.},
	number = {Number: CSHCN TR 2003-9}
}
@article {
	title = {Predicting Bottleneck Bandwidth Sharing by Generalized TCP Flows},
	author = {Misra, Archan., Ott, Teunis., Baras, John S.},
	year = {2002},
	month = {11/2002},
	abstract = {The paper presents a technique for computing the individual throughputs and the average queue occupancy when multiple TCP connections share a single bottleneck buffer. The bottleneck buffer is assumed to perform congestion feedback via randomized packet marking or drops. We first present a fixed point-based analytical technique to compute the mean congestion window sizes, the mean queue occupancy and the individual throughputs when the TCP flows perform idealized congestion avoidance. We subsequently extend the technique to analyze the case where TCP flows perform generalized congestion avoidance and demonstrate the use of this technique under the Assured Service model, where each flow is assured a minimum traffic rate. Simulations are used to demonstrate the accuracy of this technique for relatively low values of packet dropping probability and a much wider range of packet marking probability.},
	pages = {pp. 557-576},
	volume = {Volume 40},
	number = {Issue 4},
	journal = {Computer Networks Journal}
}
@article {
	title = {Understanding Multi-Scaling Network Traffic: A Structural TCP Traffic Model},
	author = {Liu, Xicheng., Baras, John S.},
	year = {2002},
	month = {03/2002},
	journal = {IEEE ACM Transactions on Networking}
}
@techreport {
	title = {Flow Control at Satellite Gateways},
	author = {Zhou, Xiaoming., Liu, Xicheng.},
	year = {2002},
	month = {01/2002},
	abstract = {In this paper we analyze the problems that cause this dramatically degradedperformance. Based on the observation that it difficult for an end-to-end solution to solve these problems in this kind of hybrid networks, we propose a connection splitting based solution. A rate-based protocol is designed for the satellite connections and a flow control scheme at the satellite gateways (SGW) used to couple the two split connections together.},
	number = {Number: CSHCN TR 2002-19}
}
@techreport {
	title = {A Dynamic Optimization Approach to the Scheduling Problem in Satellite and Wireless Broadcast Systems},
	author = {Raissi-Dekhordi, Majid.},
	year = {2002},
	month = {01/2002},
	abstract = {The continuous growth in the demand for access to information andthe increasing number of users of the information delivery systemshave sparked the need for highly scalable systems with moreefficient usage of the bandwidth. One of the effective methods forefficient use of the bandwidth is to provide the information to agroup of users simultaneously via broadcast delivery. Generally,all applications that deliver the popular data packages (trafficinformation, weather, stocks, web pages) are suitable candidatesfor broadcast delivery and satellite or wireless networks withtheir inherent broadcast capability are the natural choices forimplementing such applications.In this report, we investigate one of the most important problemsin broadcast delivery i.e., the broadcast scheduling problem. Thisproblem arises in broadcast systems with a large number of datapackages and limited broadcast channels and the goal is to findthe best sequence of broadcasts in order to minimize the average waiting time of the users.We first formulate the problem as a dynamic optimization problemand investigate the properties of the optimal solution. Later, weuse the bandit problem formulation to address a version of theproblem where all packages have equal lengths. We find anasymptotically optimal index policy for that problem and comparethe results with some well-known heuristic methods.},
	number = {Number: CSHCN TR 2002-34}
}
@techreport {
	title = {Scalable and Efficient Key Agreement Protocols for Secure Multicast Communication in MANETs},
	author = {Striki, Maria.},
	year = {2002},
	month = {01/2002},
	abstract = {In this paper protocols for group key distribution are compared and evaluated from the point of view of Mobile Ad Hoc Networks (MANETs). A MANET is a collection of wireless mobile nodes, communicating among themselves over possibly multihop paths, without the help of any infrastructure such as base stations or access points. So the need to render those networks as autonomous and secure as possible, since no central authorization can be assumed at all times, becomes emergent. Key management is the service that ensures the security of communication among nodes, and the capability of their cooperation as a secure group. It consists of three important services: key generation, user authentication and key distribution. In this work we assume that the participating users have already been authenticated with some mechanism, and we are focused only on studying and comparing protocols for group key establishment in MANETs. We distinguish the protocols in two families, the contributory and non-contributory and we evaluate them from the point of view of MANETs.},
	number = {Number: CSHCN TR 2002-28}
}
@techreport {
	title = {TCP Performance in Wireless Systems with Opportunistic Scheduling},
	author = {Srinivasan, Roshni.},
	year = {2002},
	month = {01/2002},
	abstract = {We use extensive simulations to expose the linkage between scheduling atthe medium access (MAC) layer and TCP performance. The results in thispaper underscore the need for careful design of opportunistic schedulingmechanisms in order to ensure that gains in MAC layer are also realized by TCP.},
	number = {Number: CSHCN TR 2002-22}
}
@techreport {
	title = {On QoS Provisioning in ATM Networks},
	author = {Arora, Anubhav.},
	year = {2002},
	month = {01/2002},
	abstract = {A novel framework for QoS management is proposed in this paper to provide QoS guarantees to real-time connections.It comprises of in-service QoS monitoring mechanisms, a hierarchical scheduling algorithm based on dynamicpriorities that are adaptive to measurements, and methods to tune the schedulers at individual nodes based on the endto-end measurements.},
	number = {Number: CSHCN TR 2002-7}
}
@techreport {
	title = {A Multilevel ON/OFF Model for Multifractal Internet Traffic},
	author = {Jou,  Jia-Shiang.},
	year = {2002},
	month = {01/2002},
	abstract = {In this paper, an open-loop multilevel ON/OFF modelis proposed to capture the multifractal behavior of the HTTPtraffic on the Internet. It is assumed that the life time of aTCP session and the active time of a burst within a TCP session have a heavy-tail type distribution. The aggregatetraffic of this model is shown to be multifractal. We analyze itssecond and higher order statistics by the wavelet analysis anddevelop a simple method to estimate the model parameters from areal Internet trace. We show that real and synthesized trafficproduce the same Logscale Diagram with accuracy, for properselection of the model parameter. Finally, we compare using theNS-2 simulator the queueing behavior of FIFO queues fed by realand synthetic traffic demands.},
	number = {Number: CSHCN TR 2002-5}
}
@techreport {
	title = {Alternative Network Architectures for Supporting Communications from the International Space Station},
	author = {Nguyen, Alex T., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {In order to support the communications needs of the International Space Station (ISS), alternative communications architectures to provide broadband support need to be considered. We address three communications options and evaluate an architecture for the direct to ground option, which could serve as an intermediary solution to satisfy near term communications needs of commercial experiments and payloads on the ISS and overcome certain limitations of the current ISS communications infrastructure. We focus on a particular user\&rsquo;s requirements, and examine the system\&rsquo;s communications links, and coverage availability. These parameters, along with high-level cost estimates, are compared to using commercial relay satellites, and an enhanced TDRSS. The direct to ground option is viable for store-and-forward applications and cost comparable to commercial constellations, but TDRSS is the choice for real-time or continuous data applications.},
	number = {Number: CSHCN TR 2002-9}
}
@techreport {
	title = {TCP over Satellite Hybrid Networks: A Survey},
	author = {Zhou, Xiaoming.},
	year = {2002},
	month = {01/2002},
	abstract = {Satellite is going to play an important role in the global information infrastructure. Satellite canprovide direct to home Internet service (i.e. DirecPC from Hughes Network System) and it can alsoserve as traffic trunk in the middle of the network. About 98 percent of the Internet traffic is TCPtraffic. TCP works well in the terrestrial fiber network. However, in the satellite hybrid networks,because of the long propagation delay, large bandwidth-delay product, high bit error rate anddownstream/upstream bandwidth asymmetry, TCP performance degrades dramatically. This paperaddresses the problems of TCP in satellite data networks and reviews the proposed solutions in theliterature. For each solution, the advantages and disadvantages are pointed out. In addition,extensive simulations have been done for the proxy based scheme currently used in the industry tofind out how and to what extent the enhancements, such as connection splitting, window scalingand selective acknowledgement, benefit the TCP throughput.},
	number = {Number: CSHCN TR 2002-15}
}
@techreport {
	title = {IP Multicast via Satellite: A Survey},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {Many of the emerging applications in the Internet, such astele-conferencing, distance-learning, distributed games, softwareupdates, and distributed computing would benefit from multicastservices. In many of these applications, there is a need todistribute information to many sites that are widely dispersed fromeach other. Communication satellites are a natural technology optionand are extremely well suited for carrying such services. Despite thepotential of satellite multicast, there exists little support forsatellite IP multicast services. Both Internet Engineering andInternet Research Task Forces (IETF and IRTF) have been involved in aresearch effort to identify the design space for a general purposereliable multicast protocol and standardize certain protocolcomponents as building blocks. However, for satellite multicastservices, several of these components have a different designspace. In this paper, we attempt to provide an overview of the designspace and the ways in which the network deployment and applicationrequirements affect the solution space. We maintain a similartaxonomy to that of the IETF efforts, and identify which keycomponents of a general multicast protocol are affected by two of themost common satellite network deployment scenarios. We also highlightsome of the issues which we think are critical in the development ofnext generation satellite IP multicast services.},
	number = {Number: CSHCN TR 2002-35}
}
@techreport {
	title = {Negotiating Access Control Policies Between Autonomous Domains},
	author = {Bharadwaj, Vijay G.},
	year = {2002},
	month = {01/2002},
	abstract = {Autonomous policy domains often need to share resources to accomplish a common task. To do this they must negotiate a common access control policy to the shared resources. We use mathematical techniques from game theory to show that the outcome of such negotiations can often be predicted from the distribution of power among the participants, independent of the actual mechanics of negotiation. We discuss the axiomatic derivation of some game theoretic solution concepts, and illustrate our techniques with examples.},
	number = {Number: CSHCN TR 2002-3}
}
@techreport {
	title = {INORA- A Unified Signaling and Routing Protocol in Mobile AdHoc networks},
	author = {Dharmaraju, Dinesh., Roy-Chowdhury, Ayan., Hovareshti, Pedram.},
	year = {2002},
	month = {01/2002},
	abstract = {Mobile Ad hoc NETworks(MANET) are characterized by bandwidthconstrained wireless links, multiple hops and highly dynamic topologies.Providing QoS support in MANETs is hence a challenging task. Thispaper presents the design, implementation and evaluation of INORA,which is a network layer QoS support mechanism that makes use of theINSIGNIA in-band signaling mechanism and TORA routing protocol forMANETs. TORA provides multiple routes between a given source and destination.},
	number = {Number: CSHCN TR 2002-18}
}
@article {
	title = {An Information Theoretic Approach for Design and Analysis of Rooted-Tree Based Multicast Key Management Schemes},
	author = {Poovendran, Radha., Baras, John S.},
	year = {2001},
	month = {11/2001},
	abstract = {Recent literature presents several seemingly different approaches to rooted-tree-based multicast key distribution schemes [6]{\textendash}[8], [28], [29] that try to minimize the user key storage while providing efficient member deletion. In this paper, we show that the user key storage on rooted trees can be systematically studied using basic concepts from information theory. We show that the rooted-tree-based multicast key distribution problem can be posed as an optimization problem that is abstractly identical to the optimal codeword length selection problem in information theory. In particular, we show that the entropy of member deletion statistics quantifies the optimal value of the average number of keys to be assigned to a member. We relate the sustainable key length to statistics of member deletion event and the hardware bit generation rate. We then demonstrate the difference between the key distribution on rooted trees and the optimal codeword length selection problem with an example of a key distribution scheme that attains optimality but fails to prevent user collusion [7], [8]},
	pages = {pp. 2824-2834},
	volume = {Vol. 47},
	number = {No. 7},
	journal = {IEEE Transactions on Information Theory}
}
@techreport {
	title = {On System Designs of Distributed, Extensible Framework for Network Monitoring and Control},
	author = {Li, Hongjun., Yang, Shahan.},
	year = {2001},
	month = {01/2001},
	abstract = {In this paper, we present a distributed, extensible framework for supporting adaptive, dynamic network monitoring and control. We borrow the paradigm of management by delegation [8] and distribute some processing intelligence to network elements. The functionality of the delegated agents, and even that of the native software processes, could be extended dynamically without recompilation. Such procedure is called change of logic and we explain it in the framework of communicating finite state machines for extending native process functionality. We use Java technology and C/C++ dynamic linkage mechanism to achieve the standard hosting infrastructure for these agents and our system designs span a wide scope of applications.},
	number = {Number: CSHCN TR 2001-12}
}
@techreport {
	title = {A New Adaptive Aggregation Algorithm for Infinite Horizon Dynamic Programming},
	author = {Zhang, Chang.},
	year = {2001},
	month = {01/2001},
	abstract = {Dynamic programming suffers the "curse of dimensionality" when it isemployed for complex control systems. State aggregation is used to solvethe problem and acceleratecomputation by looking for a sub-optimal policy. In this paper, a new method, which converges much faster thanconventional aggregated value iteration based on TD(0), is proposed for computing the valuefunctions of theaggregated system. Preliminary results show that the new method increases thespeed of convergence impressively. Aggregation introduces errorsinevitably. An adaptive aggregation scheme employing the newcomputation method isalso proposed to reduce the aggregation errors.},
	number = {Number: CSHCN TR 2001-5}
}
@techreport {
	title = {Performance Evaluation of Run-to-Run Control Methods in Semiconductor Processes},
	author = {Zhang, Chang.},
	year = {2001},
	month = {01/2001},
	abstract = {Run-to-Run (RtR) control plays an important role in semiconductormanufacturing processes. In this paper, RtR control methods are classified and evaluated. The set-valued RtR controllers with ellipsoid approximation are compared with two typical RtR controllers: the Exponentially Weighted Moving Average (EWMA) controller and the Optimizing Adaptive Quality Controller (OAQC) by simulations according to the following criteria: A good RtR controller should be able to compensate for various disturbances, such as small drifts, step disturbances and model errors; moreover, it should be able to deal with bounds, cost requirement and multipletargets that are often encountered in semiconductor processes. Based on our simulation results, suggestions on selection of a proper RtR controller for a semiconductor process are given as conclusions.},
	number = {Number: CSHCN TR 2001-20}
}
@techreport {
	title = {A Framework for Supporting Intelligent Fault and Performance Management for Communication Networks},
	author = {Li, Hongjun.},
	year = {2001},
	month = {01/2001},
	abstract = {For the first question, we define the notion of right diagnosis via the introduction of intervention networks. For the second question, we formulate the decision making procedure using the framework of partially observable Markov decision processes. A heuristic dynamic strategy is proposed to solve this problem and the effectiveness is shown via simulation.},
	number = {Number: CSHCN TR 2001-13}
}
@article {
	title = {An Architecture for Internet Service via Broadband Satellite Networks},
	author = {Bharadwaj, Vijay G., Baras, John S., Butts, Norman P.},
	year = {2001},
	month = {01/2001},
	abstract = {High bandwidth satellites offer the promise of a rapidly deployable communication infrastructure with a natural support for mobility. However, many used versions of the Transmission Control Protocol perform poorly over satellite links, and this presents an obstacle to the deployment of such systems. We present an architecture that overcomes these problems and allows easy integration of heterogeneous networks into the larger Internet. We also present some results from our initial implementation, which uses TCP connection splitting to improve TCP performance over satellite links.},
	pages = {pp. 29-50},
	volume = {Vol. 19},
	number = {Issue  1},
	journal = {International Journal of Satellite Communications}
}
@article {
	title = {Generating and Evaluating Designs and Plans for Microwave Modules},
	author = {Nau, Dana S., Ball, Mike., Baras, John S., Chowdhury, Abdur., Lin, Edward., Meyer, Jeff., Rajamani, Ravi., Splain, John., , Trichur, Vinai.},
	year = {2000},
	month = {09/2000},
	abstract = {This paper describes the process planning techniques we developed for us in an integrated product and process design (IPPD) tool for the design and manufacture of microwave transmit/receive modules. Given a collection of data about the design of a microwave module, the IPPD tool uses a combination of AI planning and OR tradeoff analysis to produce a collection of alternative designs and alternative process plans that have Pareto optimal values for manufacturing and purchasing lead time, process yield, cost, and number of suppliers. This information is intended to provide designers with immediate feedback on how to improve the cost and productivity of their designs.},
	pages = {pp. 289-304},
	volume = {Vol. 14},
	number = {No. 4},
	journal = {AI for Engineering Design, Analysis and Manufacturing (AI-EDAM)}
}
@techreport {
	title = {Hierarchical Modeling for Network Performance Evaluation},
	author = {Liu, Mingyan.},
	year = {2000},
	month = {01/2000},
	abstract = {As networks grow in size, nodes tendto form clusters geographically and hierarchical routing schemes are morecommonly used, and it is important that network modeling methods havescale-up capabilities. Loss networks and reduced load/fixed point modelsare often used toapproximate call blocking probabilities and hence throughput in a circuitswitched network. We use the same idea for estimating connection blockingin a data network with certain QoS routing schemes. However so far most workbeing done in this area is for flat networks with flat routing schemes.},
	number = {Number: CSHCN TR 2000-8}
}
@techreport {
	title = {Maximum Likelihood Slow Frequency-Selective Fading Channel Estimation Using Frequency Domain Approach},
	author = {Jiang, Yimin.},
	year = {2000},
	month = {01/2000},
	abstract = {Traditional works assumed symbol period spaced delay-tapped line model and additive white Gaussian noise (AWGN). Because of pre-filtering in the receiver front end, if the sampling rate is larger than one sample per symbol or sampling epoch is unknown (i.e., timing information is not available), AWGN model is not valid anymore.},
	number = {Number: CSHCN TR 2000-13}
}
@techreport {
	title = {Reliable Multicasting via Satellite: Delay Considerations},
	author = {Payne, Stephen Marshall.},
	year = {2000},
	month = {01/2000},
	abstract = {Many different reliable multicast protocols have been proposed and analyzed in the current literature. Since satellites are naturallya braodcast medium, multicast communications have the potential togreatly benefit from their wide-scale deployment. The performance ofreliable multicast protocols needs to be studied and become betterunderstood over networks including satellite links. Most of the analysisperformed on these protocols has dealt with bandwidth usage, bufferrequirements, and processing delay. Very few studies address thetransmission delay incurred from using reliable multicast protocols. Hybriderror control protocols have been studied in terms of bandwidth and delay.The effects of different estimation schemes coupled with autoparityusage are investigated and results are compared. Simple adaptive mechanismsused with a local recovery scheme are found to offer the best overallresults in terms of reducing recovery latency and satellite bandwidth usage.},
	number = {Number: CSHCN TR 2000-10}
}
@techreport {
	title = {Hierarchical Loss Network Model for Performance Evaluation},
	author = {Liu, Mingyan.},
	year = {2000},
	month = {01/2000},
	abstract = {As networks grow in size, nodes tendto form clusters geographically and hierarchical routing schemes are morecommonly used. Loss network and reduced load models are often used toapproximate end-to-endcall blocking probabilities, and hence, throughput. However so far all workbeing done in this area is for flat networks with flat routing schemes.},
	number = {Number: CSHCN TR 2000-1}
}
@techreport {
	title = {A Decision-Process Analysis of Implicit Coscheduling},
	author = {Poovendran, Radha., Keleher, P. },
	year = {2000},
	month = {01/2000},
	abstract = {This paper presents a theoretical framework based on Bayesian decision theory for analyzing recently reported results on implicit coscheduling of parallel applications on clusters of workstations. Using probabilistic modeling, we show that the approach presented can be applied for processes with arbitrary communication mixes. We also note that our approach can be used for deciding the additional spin times in the case of spin-yield.Finally, we present arguments for the use of a different notion of fairness than assumed by prior work.},
	number = {Number: CSHCN TR 2000-12}
}
@techreport {
	title = {Fair Bandwidth Allocation and Buffer Management in Hybrid Network Gateways},
	author = {Srinivasan, Roshni., Vaidyanathan, Ravichander.},
	year = {2000},
	month = {01/2000},
	abstract = {In supportof each of these contributions, we report on extensive simulationresults. Our scheme outperforms other resource allocation schemesreported in the literature and in particular, demonstrates significantimprovements in fairness to long RTT connections in the hybrid networkframework.},
	number = {Number: CSHCN TR 2000-11}
}
@techreport {
	title = {A Hierarchical Structure For Finite Horizon Dynamic Programming Problems},
	author = {Zhang, Chang.},
	year = {2000},
	month = {01/2000},
	abstract = {In this paper, we propose a hierarchical structure to solve finite horizon stochastic shortest pathproblems in parallel. In general, the approach reducesthe time complexity of the original problem to a logarithm level, which hassignificant practical meaning.},
	number = {Number: CSHCN TR 2000-19}
}
@techreport {
	title = {On the True Cramer-Rao Lower Bound for the DA Joint Estimation of Carrier Phase and Timing Offsets},
	author = {Jiang, Yimin., Sun, Feng-Wen.},
	year = {2000},
	month = {01/2000},
	abstract = {In this manuscript, we derive a closed-form formula for data-aided CRB fortiming and phase synchronization with respect to arbitrary training sequence. The bound illustrates the close relation between the training sequence and the fundamental limit on timing and phase synchronization. This bound provides additional insights on the sequence design.},
	number = {Number: CSHCN TR 2000-14}
}
@techreport {
	title = {Intelligent Distributed Fault Management for Communication Networks},
	author = {Li, Hongjun.},
	year = {2000},
	month = {01/2000},
	abstract = {In this paper, we present an intelligent, distributed fault management system for communication networks using belief networks as fault model and inference engine. The managed network is divided into domains and for each domain, there is an intelligent agent called Domain Diagnostic Agent attached to it, which is responsible for this domain{\textquoteright}s fault management. Belief network models are embedded in such an agent and under symptoms observation, the posterior probabilities of each candidate fault node being faulty is computed. We define the notion of right diagnosis, describe the diagnosis process based on this concept, and present a strategy for generation of test sequence.},
	number = {Number: CSHCN TR 2000-15}
}
@article {
	title = {Combined Compression and Classification with Learning Vector Quantization},
	author = {Baras, John S., Dey, Subhrakanti.},
	year = {1999},
	month = {09/1999},
	abstract = {Combined compression and classification problems are becoming increasingly important in many applications with large amounts of sensory data and large sets of classes. These applications range from automatic target recognition (ATR) to medical diagnosis, speech recognition, and fault detection and identification in manufacturing systems. In this paper, we develop and analyze a learning vector quantization (LVQ) based algorithm for combined compression and classification. We show convergence of the algorithm using the ODE method from stochastic approximation. We illustrate the performance of our algorithm with some examples.},
	pages = {pp. 1991-1920},
	volume = {Vol. 45},
	number = {No. 6},
	journal = {IEEE Transactions on Information Theory}
}
@article {
	title = {Estimation of Hidden Markov Models for Partially Observed Risk Sensitive Control Problems},
	author = {Frankpitt, Bernard., Baras, John S.},
	year = {1998},
	month = {01/1998},
	abstract = {This paper provides a summary of our recent work on the problem of combined estimation and control of systems described by finite state, hidden Markov models. We establish the stochastic framework for the problem, formulate a separated control policy with risk-sensitive cost functional, describe an estimation scheme for the parameters of the hidden Markov model that describes the plant and finally indicate how the combined estimation and control problem can be reformulated in a framework that permits an application of stochastic approximation techniques to the proof of asymptotic convergence of the estimator.},
	pages = {pp 739-746},
	volume = {Vol 34},
	number = {No. 6},
	journal = {Kybernetika}
}
@article {
	title = {Robust Control of Set-Valued Discrete Time Dynamical Systems},
	author = {Baras, John S., Patel, Nital S.},
	year = {1998},
	month = {01/1998},
	abstract = {This paper presents results obtained for the control of set-valued discrete-time dynamical systems. Such systems model nonlinear systems subject to persistent bounded noise. A robust control problem for such systems is introduced. The problem is formulated as a dynamic game, wherein the controller plays against the set-valued system. Both necessary and sufficient conditions in terms of (stationary) dynamic programming equalities are presented. The output feedback problem is solved using the concept of an information state, where a decoupling between estimation and control is obtained. The methods yield a conceptual approach for constructing controlled-invariant sets and stabilizing controllers for uncertain nonlinear systems.},
	pages = {pp. 61-75},
	volume = {Vol. 43},
	number = {No. 1},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Weak Continuity with Structural Constraints},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1997},
	month = {12/1997},
	abstract = {Nonlinear regression and nonlinear regularization are two powerful approaches to segmentation and nonlinear filtering. In this correspondence, we propose a hybrid approach that effectively combines the best of both worlds and can be efficiently implemented via the Viterbi algorithm.},
	pages = {pp.  3096-3104},
	volume = {Vol. 45},
	number = {No. 12},
	journal = {IEEE Transactions on Signal Processing}
}
@article {
	title = {A Framework for Robust Run by Run Control with Lot Delayed Measurements},
	author = {Baras, John S., Patel, Nital S.},
	year = {1997},
	month = {02/1997},
	abstract = {This paper considers the run by run control problem. We develop a framework to solve such a problem in a robust fashion. The framework also encompasses the case when the system is subject to delayed measurements. Recent results available for the control of such systems are reviewed, and two examples are presented. The first example is based on the end-pointing problem for a depositional process and is subject to noise which has both Gaussian and uniform components. The second one is concerned with rate control in an LPCVD reactor.},
	pages = {pp. 75-83},
	volume = {Vol. 10},
	number = {No. 1},
	journal = {IEEE Transactions on Semiconductor Manufacturing}
}
@article {
	title = {Robust and Risk-Sensitive Output Feedback Control for Finite State Machines and Hidden Markov Models},
	author = {Baras, John S., James, Matthew R.},
	year = {1997},
	month = {01/1997},
	abstract = {The purpose of this paper is to develop a framework for designing controllers for finite state systems which are robust with respect to uncertainties. A deterministic model for uncertainties is introduced, leading to a dynamic game formulation of the robust control problem. This problem is solved using an appropriate information state. A risk-sensitive stochastic control problem is formulated and solved for Hidden Markov Models, corresponding to situations where the model for the uncertainties is stochastic. The two problems are related using small noise limits.},
	pages = {pp. 371-374},
	volume = {Vol. 7},
	number = {No. 3},
	journal = {Journal of Mathematical Systems, Estimation, and Control}
}
@article {
	title = {Partially Observed Differential Games, Infinite Dimensional HJI Equations, and Nonlinear H$\infty$~Control},
	author = {James, Matthew R., Baras, John S.},
	year = {1996},
	month = {07/1996},
	abstract = {This paper presents new results for partially observed nonlinear differential games. Using the concept of information state, we solve this problem in terms of an infinite-dimensional partial differential equation, which turns out to be the Hamilton-Jacobi-Isaacs (HJI) equation for partially observed differential games. We give definitions of smooth and viscosity solutions and prove that the value function is a viscosity solution of the HJI equation. We prove a verification theorem, which implies that the optimal controls are separated in that they depend on the observations through the information state. This constitutes a separation principle for partially observed differential games. We also present some new results concerning the certainty equivalence principle under certain standard assumptions. Our results are applied to a nonlinear output feedback H$\infty$~ robust control problem.},
	pages = {pp.  1342-1364},
	volume = {Vol. 34},
	number = {No. 4},
	journal = {SIAM Journal on Control and Optimization}
}
@article {
	title = {Further results on MAP Optimality and Strong Consistency of Certain Classes of Morphological Filters},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1996},
	month = {05/1996},
	abstract = {Morphological openings and closings can be viewed as consistent MAP estimators of smooth random binary image signals immersed in i.i.d. clutter, or suffering from i.i.d. random dropouts. We revisit this viewpoint under much more general assumptions and show that, quite surprisingly, the above interpretation is still valid.},
	pages = {pp. 762-764},
	volume = {Vol. 5},
	number = {No. 5},
	journal = {IEEE Transactions on Image Processing}
}
@article {
	title = {Designing Response Surface Model Based Run by Run Controllers: A Worse Case Approach},
	author = {Baras, John S., Patel, Nital S.},
	year = {1996},
	month = {04/1996},
	abstract = {This paper presents a framework for carrying out run-by-run (RbR) control via a deterministic worst-case approach. In particular, the RbR controller developed tries to minimize the worst-case performance of the plant. This yields a methodology for handling uncertainty. A consequence of using the deterministic approach is that we no longer need any assumptions on the statistics of the noise. Rather, what we require is that the noise be bounded. Thus, we can also deal with non- Gaussian and correlated noise. We provide results comparing the performance of the controller to a recursive least squares (US) based controller.},
	pages = {pp. 98-104},
	volume = {Vol. 19},
	number = {No. 2},
	journal = {IEEE Transactions on Components, Packaging, and Manufacturing Technology, Pt C: Manufacturing}
}
@article {
	title = {Time-Recursive Computation and Real-Time Parallel Architectures:~A Framework},
	author = {Frantzeskakis, Emmanuel., Baras, John S., Liu, Ray K J.},
	year = {1995},
	month = {11/1995},
	abstract = {The time-recursive computation has been proven a particularly useful tool in real-time data compression, in transform domain adaptive filtering, and in spectrum analysis. Unlike the FFT-based ones, the time-recursive architectures require only local communication. Also, they are modular and regular, thus they are very appropriate for VLSI implementation and they allow a high degree of parallelism. In this two-part paper, we establish an architectural framework for parallel time-recursive computation. We consider a class of linear operators that consists of the discrete time, time invariant, compactly supported, but otherwise arbitrary kernel functions. We show that the structure of the realization of a given linear operator is dictated by the decomposition of the latter with respect to proper basis functions. An optimal way for carrying out this decomposition is demonstrated. The parametric forms of the basis functions are identified and their properties pertinent to the architecture design are studied. A library of architectural building modules capable of realizing these functions is developed. An analysis of the implementation complexity for the aforementioned modules is conducted. Based on this framework, the time-recursive architecture of a given linear operator can be derived in a systematic routine way.},
	pages = {pp. 2762-2775},
	volume = {Vol. 43},
	number = {No. 11},
	journal = {IEEE Transactions on Signal Processing}
}
@article {
	title = {Robust H$\infty$~Output Feedback Control for Nonlinear Systems},
	author = {James, Matthew R., Baras, John S.},
	year = {1995},
	month = {06/1995},
	abstract = {In this paper, we present a new approach to the solution of the output feedback robust H$\infty$~control problem. We employ the recently developed concept of information state for output feedback dynamic games and obtain necessary and sufficient conditions for the solution to the robust control problem expressed in terms of the information state. The resulting controller is an information state feedback controller and is intrinsically infinite dimensional. Stability results are obtained using the theory of dissipative systems, and indeed, our results are expressed in terms of dissipation inequalities.},
	pages = {pp. 1007-1017},
	volume = {Vol. 40},
	number = {No.  6},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Finite-Dimensional Optimal Controllers for Nonlinear Plants},
	author = {Moore, John B., Baras, John S.},
	year = {1995},
	month = {01/1995},
	abstract = {Optimal risk sensitive feedback controllers are now available for very general stochastic nonlinear plants and performance indices. They consist of nonlinear static feedback of so-called information states from an information state filter. In general, these filters are linear, but infinite dimensional, and the information state feedback gains are derived from (doubly) infinite dimensional dynamic programming. The challenge is to achieve optimal finite dimensional controllers using finite dimensional calculations for practical implementation. This paper derives risk sensitive optimality results for finite-dimensional controllers. The controllers can be conveniently derived from {\textquoteright}linearized{\textquoteright} (approximate) models (applied to nonlinear stochastic systems). Performance indices for which the controllers are optimal for the nonlinear plants are revealed. That is, inverse risk-sensitive optimal control results for nonlinear stochastic systems with finite-dimensional linear controllers are generated. It is instructive to see from these results that as the nonlinear plants approach linearity, the risk sensitive finite dimensional controllers designed using linearized plant models and risk sensitive indices with quadratic cost kernels, are optimal for a risk-sensitive cost index which approaches one with a quadratic cost kernel. Also even far from plant linearity, as the linearized model noise variance becomes suitably large, the index optimized is dominated by terms which can have an interesting and practical interpretation. Limiting versions of the results as the noise variances approach zero apply in a purely deterministic nonlinear H$\infty$~setting. Risk neutral and continuous-time results are summarized. More general indices than risk sensitive indices are introduced with the view to giving useful inverse optimal control results in non-Gaussian noise environments.

Keywords: Nonlinear control; Optimal controllers; Risk-sensitive control; Information state filters; Finite-dimensional controllers},
	pages = {pp. 223-230},
	journal = {Systems and Control Letters, 26}
}
@article {
	title = {Derivation of Fuzzy Rules for Model Free Tuning of PID Controllers},
	author = {Baras, John S., Patel, Nital S.},
	year = {1995},
	month = {01/1995},
	abstract = {In this article, we derive the rules for a fuzzy logic based PID tuner (expert) for dominant pole systems with large rise times. We present applications of the expert to a third-order plant, separator temperature control, and pH control. It is observed that the expert can successfully tune the PID gains without requiring any process identification.},
	pages = {pp. 59-69},
	volume = {Vol. 3},
	number = {Issue I},
	journal = {Journal of Intelligent and Fuzzy Systems}
}
@article {
	title = {Binary Images Corrupted by Union/Intersection Noise},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1995},
	month = {01/1995},
	abstract = {This paper derives risk sensitive optimality results for finite-dimensional controllers. The controllers can be conveniently derived for {\textquoteright}linearized{\textquoteright} (approximate) models (applied to nonlinear stochastic systems). Performance indices for which the controllers are optimal for the nonlinear plants are revealed. That is, inverse risk-sensitive optimal control results for nonlinear stochastic systems with finite dimensional linear controllers are generated. It is instructive to see from these results that as the nonlinear plants approach linearity, the risk sensitive finite dimensional controllers designed using linearized plant models and risk sensitive indices with quadratic cost kernels, are optimal for a risk sensitive cost index which approaches one with a quadratic cost kernel. Also even far from plant linearity, as the linearized model noise variance becomes suitably large, the index optimized is dominated by terms which can have an interesting and practical interpretation.},
	pages = {pp. 223-230},
	journal = {Systems and Control Letters, 26}
}
@article {
	title = {Algebraic Analysis of the Generating Functional for Discrete Random Sets, and Statistical Inference for Intensity in the Discrete Boolean Random Set Model},
	author = {Sidiropoulos, N D., Baras, John S., Berenstein, Carlos A.},
	year = {1994},
	month = {06/1994},
	abstract = {We consider binary digital images as realizations fo a uniformly bounded discrete random set, a mathematical object that can be defined directly on a finite lattice. In this setting, we show that it is possible to move between two equivalent probabilistic model specifications. We formulate a restricted version of the discrete-case analog of a Boolean random-set model obtained its probability mass function, and use some methods of morphological image analysis to derive tools for its statistical stability},
	pages = {pp.  273-290},
	volume = {Vol. 4},
	number = {Issue 3},
	journal = {Journal of Mathematical Imaging and Vision}
}
@article {
	title = {Risk-Sensitive Control and Dynamic Games for Partially Observed Discrete-Time Nonlinear Systems},
	author = {James, Matthew R., Baras, John S., Elliott, Robert J.},
	year = {1994},
	month = {04/1994},
	abstract = {In this paper, we solve a finite-horizon partially observed risk-sensitive stochastic optimal control problem for discrete-time nonlinear systems and obtain small noise and small risk limits. The small noise limit is interpreted as a deterministic partially observed dynamic game, and new insights into the optimal solution of such game problems are obtained. Both the risk-sensitive stochastic control problem and the deterministic dynamic game problem are solved using information states, dynamic programming, and associated separated policies. A certainty equivalence principle is also discussed. Our results have implications for the nonlinear robust stabilization problem. The small risk limit is a standard partially observed risk-neutral stochastic optimal control problem.},
	pages = {pp.  780-792},
	volume = {Vol. 39},
	number = {No. 9},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Properties of the Multiscale Maxima and Zero-Crossings Representations},
	author = {Berman, Zeev., Baras, John S.},
	year = {1993},
	month = {12/1993},
	abstract = {The analysis of a discrete multiscale edge representation is considered. A general signal description called an inherently bounded adaptive quasi-linear representation (AQLR), motivated by two important examples, namely, the wavelet maxima representation, and the wavelet zero-crossings representation is introduced. This paper mainly addresses the questions of uniqueness and stability. It is shown that the dyadic wavelet maxima (zero-crossings) representations are, in general nonunique. Nevertheless, using the~idea of the inherently bounded AQLR, two stability results are proven. For a special case, where perturbations are limited to the continuous part of the representation, a Lipschitz condition is satisfied.},
	pages = {pp. 3212-3231},
	volume = {Vol. 41},
	number = {No. 12},
	journal = {Special issue \&ldquo;Wavelets and Signal Processing\&rdquo; of the IEEE Trans. on Signal Processing}
}
@article {
	title = {MANDATE:~Managing Networks using Database Technology},
	author = {Haritsa, Jayant., Ball, Mike., Roussopoulos, Nick., Datta, Anindya., Baras, John S.},
	year = {1993},
	month = {12/1993},
	abstract = {In recent years, there has been a growing demand for the development of tools to manage enterprise communication networks. A management information database is the heart of a network management system-- it provides the interface between all functions of the network management system and, therefore, has to provide sophisticated functionality allied with high performance. In this paper, we introduce the design of MANDATE (MAnaging Networks using DAtabase TEchnology), a proposed database system for effectively supporting the management of large enterprise networks. The MANDATE design makes a conscious attempt to take advantage of the special characteristics of network data and transactions, and of recent advances in database technology, to efficiently derive some of the required management functionality.},
	pages = {pp. 1360-1372},
	volume = {Vol. 11},
	number = {No. 9},
	journal = {IEEE Journal on Selected Areas in Communication}
}
@article {
	title = {Predictive Block-Matching Motion Estimation for TV Coding -- Part I:~Inter-Block Prediction},
	author = {Zafar, Sohail., Zhang, Ya-Qin. , Baras, John S.},
	year = {1991},
	month = {09/1991},
	abstract = {A new motion estimation/compensation scheme for TV coding is proposed in this paper. This scheme is based on predictions of inter-block motion information using minimum absolute difference block matching and hence substantially increases the searching and computation efficiency. A comparison is also made with the "optimal" full motion searching scheme for a standard test sequence.},
	pages = {pp. 97-101},
	volume = {Vol. 37},
	number = {No. 3},
	journal = {IEEE Transactions on Broadcasting}
}
@article {
	title = {Optimization-Based Design, Performance Evaluation, and Management of Communication Networks},
	author = {Baras, John S.},
	year = {1990},
	month = {04/1990},
	volume = {Vol. 3},
	number = {No. 2},
	journal = {CTContact}
}
@article {
	title = {The Partially Observed Stochastic Minimum Principle},
	author = {Baras, John S., Elliott, Robert J., Kohlmann, Michael.},
	year = {1989},
	month = {11/1989},
	abstract = {Using stochastic flows and the generalized differentiation formula of Bismut and Kunita, the change in cost due to a strong variation of an optimal control is explicitly calculated. Differentiating this expression gives a minimum principle in both the partially observed and stochastic open loop situations. In the latter case the equation satisfied by the adjoint process is obtained by applying a martingale representation result.},
	pages = {pp. 1279-1292},
	volume = {Vol. 27},
	number = {No. 6},
	journal = {SIAM Journal on Control and Optimization}
}
@article {
	title = {Optimal Sensor Scheduling in Nonlinear Filtering of Diffusion Processes},
	author = {Baras, John S., Bensoussan, Alain.},
	year = {1989},
	month = {07/1989},
	abstract = {The nonlinear filtering problem of a vector diffusion process is considered when several noisy vector observations with possibly different dimension of their range space are available. At each time any nimber of these observations (or sensors) can be sued in the signal processing performed by the nonlinear filter. The problem considered is the optimal selection of a schedule of these sensors from the available set, so as to optimally estimate a function of the state at the final time. Optimality is measured by a combined performance measure that allocates penalties for errors in estimation, for switching between sensor schedules, and for running a sensor. The solution is obtained in the form of a system of quasi-variational inequalities in the space of solutions of certain Zakai equations.},
	pages = {pp. 786-813},
	volume = {Vol. 27},
	number = {No. 4},
	journal = {SIAM Journal on Control and Optimization}
}
@article {
	title = {An Optimization Problem from Linear Filtering with Quantum Measurements},
	author = {Baras, John S.},
	year = {1988},
	month = {01/1988},
	abstract = {We consider the problem of optimal (in the sense of minimum error variance) linear filtering a vector discrete-time signal process, which influences a quantum mechanical field, utilizing quantum mechanical measurements. The nonclassical characteristic of the problem is the joint optimization over the measurement process and the linear signal processing scheme. The problem is formulated as an optimization problem of a functional over a set of operator-valued measures and matrices. We prove the existence of optimal linear filters and provide necessary and sufficient conditions for optimality.},
	pages = {pp. 191-214},
	volume = {Vol. 18},
	journal = {Journal of Applied Mathematics and Optimization}
}
@article {
	title = {Nonlinear Filtering and Large Deviations: A PDE-Control Theoretic Approach},
	author = {James, Matthew R., Baras, John S.},
	year = {1988},
	month = {01/1988},
	abstract = {We consider the nonlinear filtering problem dx = f(x)dt + √(є)dw, dy = h(x)dt + √(є)dv, and obtain lim[є{\textrightarrow}0] є log qє (x,t) = -W(x,t) for unnormalized conditional densities qє (x,t) using PDE methods. Here, W(x,t) is the value function for a deterministic optimal control problem arising in Mortensen{\textquoteright}s deterministic estimation and is the unique viscosity solution of a Hamilton-Jacobi-Bellman equation. Hijab has also studied this filtering problem, and we extend his large deviation result for certain unnormalized conditional measures. The resulting variational problem corresponds to the above control problem.},
	pages = {pp. 391-412},
	volume = {Vol. 23},
	journal = {Stochastics}
}
@article {
	title = {Controlled Computations or Computer Control?},
	author = {Baras, John S.},
	year = {1987},
	month = {04/1987},
	pages = {pp. 7-8},
	volume = {Vol. 7},
	number = {No. 2},
	journal = {IEEE Control Systems Magazine}
}
@article {
	title = {K Competing Queues With Geometric Service Requirements and Linear Costs: The uc-rule is Always Optimal},
	author = {Baras, John S., Ma, D -J., Makowski, Armand M.},
	year = {1985},
	month = {08/1985},
	abstract = {In this note, a discrete-time system of K competing queues with geometric service requirements and arbitrary arrival patterns is studied. When the cost per slot is linear in the queue sizes, it is shown that the {\textmu}c-rule minimizes the expected discounted cost over the infinite horizon.},
	pages = {pp. 173-180},
	volume = {Vol. 6},
	number = {No. 3},
	journal = {Systems and Control Letters}
}
@article {
	title = {Two Competing Queues with Linear Costs and Geometric Service Requirements},
	author = {Baras, John S., Dorsey, Arthur J., Makowski, Armand M.},
	year = {1985},
	month = {01/1985},
	abstract = {A discrete-time model is presented for a system of two queues competing for the service attention of a single server with infinite buffer capacity. The service requirements are geometrically distributed and independent from customer to customer as well as from the arrivals. The allocation of service attention is governed by feedback policies which are based on past decisions and buffer content histories. The cost of operation per unit time is a linear function of queue sizes. Under the model assumptions, a fixed prioritization scheme known as the~{\textmu}c-rule, is shown to be optimal for the long run average criterion and for the expected discounted-criterion, over both finite and infinite horizons. Two different approaches are proposed to solve these problems. One is based on dynamic programming methodology for Markov decision processes and assumes the arrival to be i.i.d. The other is valid under no additional assumptions on the arrival streams and uses direct comparison arguments. In both cases, the sample path properties of the adopted state-space model are exploited.},
	pages = {pp. 186-209},
	volume = {Vol. 17},
	journal = {Advances in Applied Probability}
}
@article {
	title = {Existence, Uniqueness and Asymptotic Behavior of Solutions to a Class of Zakai Equations with Unbounded Coefficients},
	author = {Baras, John S., Blankenship,  Gilmer L., Hopkins, William E., Jr. },
	year = {1983},
	month = {02/1983},
	abstract = {Conditions are given to guarantee the existence and uniqueness of solutions to the Zakai equation associated with the nonlinear filtering of diffusion processes. The conditions permit stronger than a polynomial growth of the coefficients and depend instead on the relative growth rates. The results are derived by adapting, through a sequence of exponential transformations, the classical existence and uniqueness theorems for parabolic PDE{\textquoteright}s due to Besala to the "robust" form of the Zakai equation. In this process, we also obtain sharp estimates for the tail behavior of the conditional density. Examples, including observations through a polynomial sensor and estimation of the state of a "bilinear" system, are worked out in detail. Our results are compared to those of Fleming and Mitter, Pardoux, and Sussmann who, among others, have obtained existence and uniqueness theorems for a more limited class of problems by different methods.},
	pages = {pp. 203-214},
	volume = {Vol. 28-2},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Explicit Filters for Diffusions with Certain Nonlinear Drifts},
	author = {Ocone, D. L., Baras, John S., Marcus, S I.},
	year = {1982},
	month = {01/1982},
	pages = {pp. 1-16},
	volume = {Vol. 8},
	journal = {Stochastics}
}
@article {
	title = {Stochastic Control of Two Partially Observed Competing Queues},
	author = {Baras, John S., Dorsey, Arthur J.},
	year = {1981},
	month = {10/1981},
	abstract = {We consider the dynamic control of two queues competing for the services of one server. The problem is to design a server time allocation strategy, when the sizes of the queues are not observable. The performance criterion used is total expected aggregate delay. The server is assumed to observe arrivals but not departures.

This problem is formulated as a stochastic optimal control problem with partial observations. The framework we adopt is that of stochastic control in discrete time and countable "state space." The observations are modeled as discrete time, 0-1 point process with rates that are influenced by a Markov chain. Examples from computer control of urban traffic are given, to illustrate the practical motivation behind the present work, and to relate to earlier work by us on the subject. A particular feature of the formulation is that the observations are influenced by transitions of the state of the Markov chain. The classical tools of simple Bayes rule and dynamic programming suffice for the analysis. In particular, we show that the "one step" predicted density for the state of the Markov chain, given the point process observations is a sufficient statistic for control.

This framework is then applied to the specific problem of two queues competing for the services of one server. We obtain explicit solutions for the finite time expected aggregate delay problem. The implications of these results for practical applications as well as implementation aspects of the resulting optimal control laws are discussed.},
	pages = {pp. 1105-1117},
	volume = {AC-26},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Noncommutative Probability Models in Quantum Communication and Multi-Agent Stochastic Control},
	author = {Baras, John S.},
	year = {1979},
	month = {12/1979},
	abstract = {In this paper, we present a survey of basic results in quantum communication theory that utilize heavily so-called noncommutative probability models. We indicate by means of examples how these mathematical methods can lead to actual computations in specific examples. We offer a careful review of these non-commutative models and we observe the similarities with desired features in the representation of the statistics in multi-agent stochastic control problems. We then give suggestions for integrating some of the basic constructs of quantum models in the language of multi-agent stochastic control systems.},
	pages = {pp. 217-264},
	volume = {Vol. X},
	number = {No. 2},
	journal = {Richerche di Automatica}
}
@article {
	title = {Estimation of Traffic Platoon Structure from Headway Statistics},
	author = {Baras, John S., Dorsey, Arthur J., Levine, William S.},
	year = {1979},
	month = {08/1979},
	abstract = {This paper deals first with the modeling of urban traffic headway statistics. It is shown that a composite distribution based on the convex combination of a lognormal and a shifted exponential distribution gives a good fit to observed traffic data. This statistical model is then used to generate a model for the formation and passage of "platoons" of vehicles. It is shown that the problem of estimating the time at which a "platoon" passes a detector, as well as the number of vehicles in the "platoon" corresponds to the point process disorder problem. An optimal estimator for the platoon size and passage time, based on detector data, is then derived via known results for the point process disorder problem. It is shown that the computations required for this estimator can be performed in a microprocessor . Furthermore, the estimator is tested against the UTCS-1 traffic simulator and performs very well. Parameter sensitivity analysis of the estimator is presented. Finally, the use of these results to improve the filter/predictor described in a companion paper, and vice versa, is explained.},
	pages = {pp. 553-559},
	volume = {AC-24},
	number = {No. 4},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Discrete Time Point Processes in Urban Traffic Queue Estimation},
	author = {Baras, John S., Levine, William S., Lin, Tahsin L.},
	year = {1979},
	month = {02/1979},
	abstract = {Thk research was motivated by the belief that it is possible to develop improved algorithms for the computer control of urban traffic Previous research suggested that the computer software, and especially the filtering and prediction algorithms, is the limiting factor in computerized traffic control. Since the modern approach to filtering and prediction begins with the development of models for the generation of the data and since these models are also useful in the control problem, this paper deals with the modeling of traffic queues and filtering and prediction.

It is shown that the data received from vehicle detectors is a discrete time point process. The formation and dispersion of queues at a traffic signal is then modeled by a discrete-time time-varying Markov chain which is related to the observation point process Three such models of increasing complexity are given. Recent results in the theory of point-process filtering and prediction are then used to derive the nonlinear minimum error variance filters/predictors corresponding to these models. It is then shown that these optimal estimators are computationally feasible in a microprocessor. All three algorithm were tested against the UTCS-1 traffic simulator and, in one case, against an algorithm in current use called ASCOT. Some results of these tests are shown. They indicate good performance in every case and better performance than ASCOT in the comparable case.},
	pages = {pp. 12-27},
	volume = {AC-24},
	number = {No. 1},
	journal = {IEEE Transactions on Automatic Control.}
}
@article {
	title = {Chandrasekhar Algorithms for Linear Time-Varying Distributed Systems},
	author = {Baras, John S., Lainiotis, Demetrios G.},
	year = {1979},
	month = {01/1979},
	abstract = {Generalized Chandrasekhar type algorithms are obtained that are applicable to linear time varying as well as time invariant distributed systems. Utilizing the framework of J. L. Lions for quadratic control and the framework of A. Bensoussan for filtering of linear distributed systems, we analyze the implications of these algorithms.},
	pages = {pp. 153-167},
	journal = {Information Sciences 17}
}
@techreport {
	title = {Ship RCS Scintillation Simulation},
	author = {Baras, John S.},
	year = {1978},
	month = {01/1978}
}
@conference {
	title = {Quantum Mechanical Linear Filtering of Vector Signal Processes},
	author = {Baras, John S., Harger, Robert O.},
	year = {1977},
	month = {11/1977},
	abstract = {The problem of estimating a member of a discretetime vector process from past and present quantum mechanical measurements is considered; specifically, the minimum-variance linear estimator based on optimal present measurements is studied. Necessary and sufficient conditions that characterize the optimal processing matrix coefficients and the optimal measurements are discussed and interpreted. The optimal linear filter is compared to the optimal quantum estimator without postprocessing of past data. When the signal sequence is pairwise Gaussian and the optimal quantum measurement without postprocessing has the properties that it is linear in a specific sense and that its outcome and the corresponding element of the signal sequence are jointly Gaussian, then the optimal linear filter separates. That is, the optimal measurement can be taken to be the same as the optimal measurement without regard to past data, and the past and present data are processed classically. The results are illustrated by considering the filtering of the in-phase and quadrature amplitudes of a laser field received in a single-mode cavity along with thermal noise. In this case, when the random signal sequence satisfies a linear recursion, the estimate can be computed recursively in a very efficient manner.},
	booktitle = {IEEE Transactions on Information Theory},
	pages = {pp. 683-693}
}
@article {
	title = {Quantum Mechanical Linear Filtering of Vector Signal Processes},
	author = {Baras, John S., Harger, Robert O.},
	year = {1977},
	month = {11/1977},
	abstract = {The problem of estimating a member of a discrete-time vector process from past and present quantum mechanical measurements is considered; specifically, the minimum-variance linear estimator based on optimal present measurements is studied. Necessary and sufficient conditions that characterize the optimal processing matrix coefficients and the optimal measurements are discussed and interpreted. The optimal linear filter is compared to the optimal quantum estimator without postprocessing of past data. When the signal sequence is pairwise Gaussian and the optimal quantum measurement without postprocessing has the properties that it is linear in a specific sense and that its outcome and the corresponding element of the signal sequence are jointly Gaussian, then the optimal linear filter separates. That is, the optimal measurement can be taken to be the same as the optimal measurement without regard to past data, and the past and present data are processed classically. The results are illustrated by considering the filtering of the in-phase and quadrature amplitudes of a laser field received in a single-mode cavity along with thermal noise. In this case, when the random signal sequence satisfies a linear recursion, the estimate can be computed recursively in a very efficient manner.},
	pages = {pp. 683-693},
	volume = {Vol. IT-23},
	number = {No. 6},
	journal = {IEEE Transactions. on Information Theory}
}
@article {
	title = {Invariant Subspace Methods in Linear Multivariable Distributed Systems and Lumped-Distributed Network Synthesis},
	author = {Baras, John S., Dewilde, Patrick},
	year = {1976},
	month = {02/1976},
	abstract = {Linear multivariable-distributed systems and synthesis problems for lumped-distributed networks are analyzed. The methods used center around the invariant subspace theory of Helson-Lax and the theory of vectorial Hardy functions. State-space and transfer function models are studied and their relations analyzed. We single out a class of systems and networks with nonrational transfer functions (scattering matrices), for which several of the well-known results for lumped systems and networks are generalized. In particular, we develop the relations between singularities of transfer functions and "natural modes" of the systems, a degree theory for infinite-dimensional linear systems and a synthesis via lossless embedding of the scattering matrix. Finally, coprime factorizations for this class of systems are developed.},
	pages = {pp. 160-178},
	journal = {IEEE Proceedings, Special Issue on Recent Trends in Systems Theory}
}
@article {
	title = {Quantum Mechanical Linear Filtering of Random Signal Sequences},
	author = {Baras, John S., Harger, Robert O., Park, Young H.},
	year = {1976},
	month = {01/1976},
	abstract = {The problem of estimating a member of a scalar random signal sequence with quantum-mechanical measurements is considered. The minimum variance linear estimator based on an optimal present quantum measurement and optimal linear processing of past measurements is found. When the average optimal measurement without post-processing, for a fixed signal, is linear in the random signal and the signal sequence is pairwise Gaussian, the optimal processing separates: the optimal measurement is the same as the optimal measurement without regard to past data, and the past and present data are processed classically. The results are illustrated by considering the estimator of the real amplitude of a laser signal received in a single-mode cavity along with thermal noise; when the random signal sequence satisfies a linear recursion, the estimate can be computed recursively. For a one-step memory signal sequence, it is shown that the optimal observable generally differs from the optimal observable disregarding the past; the optimal measurement can be computed recursively.},
	pages = {pp. 59-64},
	volume = {Vol. IT-22},
	number = {No. 1},
	journal = {IEEE Transactions on Information Theory}
}
@article {
	title = {H2-Functions and Infinite-Dimensional Realization Theory},
	author = {Baras, John S., Brockett, Roger W.},
	year = {1975},
	month = {01/1975},
	abstract = {In this paper, the realization question for infinite-dimensional linear systems is examined for both bounded and unbounded operators. In addition to obtaining realizability criteria covering the basic cases, we discussed the relationship between canonical realizations of the same system. What one finds is that the set of transfer functions which are realizable by triples (A, b, c) with A bounded is related in a close way to the space of complex functions analytic and square integrable on the disk |s|\&lt;1, and that the set of transfer functions which is realizable by triples (A, b, c) with A unbounded but generating a strongly continuous semigroup is related in a close way to functions analytic and square integrable on a half-plane. This relation makes possible a deeper study between the transfer function and the models which realize it. Some examples illustrate the results and their applications.},
	pages = {pp.  221-241},
	volume = {Vol. 13},
	number = {No. 1},
	journal = {SIAM Journal of Control}
}
@article {
	title = {State Space Models for Infinite Dimensional Systems},
	author = {Baras, John S., Brockett, Roger W., Fuhrmann, Paul A.},
	year = {1974},
	month = {12/1974},
	abstract = {Distributed effects are present in almost all physical systems. In some cases, these can be safely ignored but there are many interesting problems where these effects must be taken into account. Most infinite dimensional systems which are important in control theory are specifiable in terms of a finite number of parameters and hence are, in principle, amenable to identification. The state-space theory of infinite dimensional systems has advanced greatly in the last few years and is now at a point where real applications can be contemplated. The realizability criteria provided by this work can be employed effectively in the first step of the identification of nonrational transfer functions, which is based on the character of their singularities. This classification has important implications for the problem of finite dimensional approximations of infinite dimensional systems. In addition, it reveals the class of transfer functions for which there exist models with spectral properties closely reflecting the properties of the singularities of the transfer functions. The study of models with infinitesimal generators having a connected resolvent sheds light on some open problems in classical frequency response methods. Finally, the methods used here allow one to see the finite dimensional theory itself more clearly as the result of placing it in the context of a larger theory.},
	pages = {pp.  693-700},
	volume = {Vol. AC-19},
	number = {No. 6},
	journal = {IEEE Transactions on Automatic Control}
}
@article {
	title = {Value of Information in Feedback Control},
	author = {Soleymani, Touraj., Baras, John S.},
	abstract = {In this article, we investigate the impact of information on networked control systems, and illustrate how to quantify a fundamental property of stochastic processes that can enrich our understanding about such systems. To that end, we develop a theoretical framework for the joint design of an event trigger and a controller in optimal event-triggered control. We cover two distinct information patterns: perfect information and imperfect information. In both cases, observations are available at the event trigger instantly, but are transmitted to the controller sporadically with one-step delay. For each information pattern, we characterize the optimal triggering policy and optimal control policy such that the corresponding policy profile represents a Nash equilibrium. Accordingly, we quantify the value of information VoIk as the variation in the cost-to-go of the system given an observation at time k. Finally, we provide an algorithm for approximation of the value of information, and synthesize a closed-form suboptimal triggering policy with a performance guarantee that can readily be implemented.},
	journal = {IEEE Transactions on Automatic Control}
}
@conference {
	title = {Linking Satellites with Terrestrial Networks for Broadband Internet Services},
	author = {Baras, John S.},
	address = {Cleveland, Ohio},
	booktitle = {Satellite Networks: Architectures, Applications and Technologies Workshop},
	pages = {pp. 27-36},
	organization = {NASA Lewis Research Center}
}
@conference {
	title = {On Observer Problems for Systems Governed by Partial Differential Equations},
	author = {Baras, John S., Bensoussan, Alain.},
	booktitle = {Conference honoring Professor A.V. Balakrishnan on his 60th birthday}
}
@conference {
	title = {Algebraic System Theory, Computer Algebra and Controller Synthesis},
	author = {Baras, John S.}
}
@article {
	title = {On Scaling Property of Network Traffic in Small Scales},
	author = {Liu, Nelson X., Baras, John S.},
	journal = {Computer Networks Journal}
}
@article {
	title = {Trust Credentials Distribution in Automatic Networks},
	author = {Jiang, Tao., Baras, John S.},
	journal = {submitted to IEEE Transactions on Parallel and Distributed Systems}
}
@conference {
	title = {Existence, Uniqueness and Tail Behavior of Solutions to Zakai Equations with Unbounded Coefficients},
	author = {Hopkins, William E., Baras, John S., Blankenship,  Gilmer L.},
	abstract = {Conditions are given to guarantee the existence and uniqueness of solutions to the Duncan-Mortensen-Zakai equation for nonlinear filtering of multivariable diffusions with unbounded coefficients. Sharp upper and lower bounds on the trail of conditional densities are also obtained. A methodology is described to treat these problems using classical p.d.e methods applied to the "robust" version of the DMZ equation. Several examples are included.},
	address = {New York, NY},
	booktitle = {Advances in Filtering and Stochastic Control, W.H. Fleming and L.G. Gorostiza},
	pages = {pp. 01-17}
}
@article {
	title = {Local Topology Pruning for Algebraic QoS Path Computations for Link-State Routing},
	author = {Somasundaram, Kiran K., Baras, John S.},
	journal = {IEEE ACM Transactions on Networking}
}
@conference {
	title = {Wireless Information Infrastructures and the Future Internet: Protocol Components, System Architectures, Security and Privacy},
	author = {Baras, John S.},
	address = {France},
	booktitle = {2014 International Symposium on Wireless Personal Multimedia Communications (WPMC)},
	organization = {Brest}
}
@conference {
	title = {Accurate Evaluation of Conditional Densities in Nonlinear Filtering},
	author = {Hopkins, William E., Blankenship,  Gilmer L., Baras, John S.},
	address = {New York, NY},
	booktitle = {Advances in Filtering and Stochastic Control, W.H. Fleming and L.G. Gorostiza},
	pages = {pp. 54-68}
}
@article {
	title = {Near-Optimal Placement of Virtualized EPC Functions with Latency Bounds},
	author = {Dietrich, David., Papagianni, Chrysa. , Panagiotis, Papadimitriou., John S. Baras},
	abstract = {The proliferation of mobiles devices, application sprawl, and
the ever-increasing data volume generates significant stress on cellular
networks and particularly on the cellular core, also known as the
Evolved Packet Core (EPC), i.e., the cellular network component residing
between the radio access network and the Internet. This is further
exacerbated by the deployment of hardware appliances for the implementation
of a wide range of network functions (e.g., gateways, mobility
management, firewalls, network address translation), hindering any
opportunity for elastic provisioning, and eventually leading to high operational
costs and a significant degree of load imbalance across the EPC.
Network Function Virtualization (NFV) has been seen a promising
solution in order to enable elasticity in the cellular core. Applying NFV
to the EPC raises the need for network function (NF) placement, which
in turn entails significant challenges, due to the stringent delay budgets
among cellular core components and the coexistence of communicating
data and control plane elements. To address these challenges, we
present a linear programming (LP) formulation for the computation of
NF placements that strikes a balance between optimality and time complexity.
Our evaluation results show that the LP achieves significantly
better load balancing, request acceptance rate, and resource utilization
compared to a greedy algorithm that performs NF placement inline with
carriers{\textquoteright} common practice today.},
	pages = {200-222},
	volume = {10340},
	journal = {Communication Systems and Networks, Series: Computer Communication Networks and Telecommunications}
}
