@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}
}
@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}
}
@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.}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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)}
}
@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)}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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)}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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}
}
@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)}
}
@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 = {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 = {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 = {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 = {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 = {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 = {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}
}
@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 = {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}
}
@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}
}
@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}
}
@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}
}
