@techreport {
	title = {Key Management for Secure Multicast in Hybrid Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2004},
	month = {08/2004},
	abstract = {This paper proposes a design for key management for secure multicast in hybrid satellite networks. Communication satellites offer an efficient way to extend IP multicast services for groups in wide-area networks. In order to be commercially viable, the multicast traffic should be accessible only to paying subscribers. Access control can be achieved by data encryption. This requires secure and efficient methods to generate, distribute and update the keys. Most current key management protocols do not scale well when applied to large dynamic groups in wide-area networks. This paper attempts to solve the above problem for groups in a hybrid network that is composed of terrestrial Ethernet LANs interconnected by ATM-based satellite channels. We investigate current group key management protocols, and design a framework for secure and scalable key management for the multicast routing architecture in the satellite network. The proposed framework is presented in detail, alongwith analysis and simulation results.},
	address = {Toulouse, France}
}
@techreport {
	title = {Framework for IP Multicast in Satellite ATM Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2004},
	month = {05/2004},
	abstract = {This paper proposes a design for IP multicast routing in hybrid satellite networks. The emergence of IP multicast for Internet group communication has placed focus on communication satellites as an efficient way to extend IP multicast services for groups with distributed membership in wide-area networks. This poses interesting challenges for routing. Satellite networks can have both wired and wireless links and also combine different link-layer technologies like Ethernet and ATM. No proposed IP multicast routing protocol for wired networks offers an integrated solution for such networks. This paper attempts to provide a solution by proposing a design for IP multicast routing in wide-area networks that have terrestrial Ethernet LANs interconnected by ATM-based satellite channels. The paper reviews the multicast services offered by IP and ATM, and proposes a multicast routing framework that combines PIM-SM protocol for terrestrial multicasting with the ATM MARS and VC mesh architecture for multicast routing over the satellite links. Modifications are made to the standard protocols to suit the unique needs of the network being considered. The feasibility of the proposed design is tested by performing simulations. The proposed framework is presented in detail, along with analysis and simulation results.},
	address = {Monterey, California},
	number = {Number: CSHCN TR 2004-8}
}
@techreport {
	title = {A direct-to-ground architecture for supporting Commercial Communications from the International Space Station},
	author = {Nguyen, Alex T., Zhou, Xiangrong., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {We outline the first steps of an effort to start defining a communications architecture for supporting broadband data communications from the International Space Station. We address three communications options and focus on a direct-to-ground architecture, which could serve as an intermediary solution to satisfy near-term communications needs of commercial experiments and payloads on the ISS and overcome certain limitations of the current ISS communications infrastructure. A high-level analysis of the architecture for the direct to ground option is performed, focusing on a particular user{\textquoteright}s requirements, communications links, and coverage availability. We also discuss system, mobility support and protocol issues that need to be addressed for this solution to be a feasible alternative.},
	address = {New York, NY}
}
@techreport {
	title = {Systems Research Center: The First Year},
	author = {Baras, John S.},
	year = {1986},
	month = {06/1986}
}
@techreport {
	title = {Distributed Opportunistic Scheduling for Wireless Ad-Hoc Networks with Block-Fading Model},
	author = {Chen, Hua., Baras, John S.},
	year = {2017},
	month = {10/2017},
	abstract = {In this paper, we study a distributed opportunistic scheduling problem to exploit the channel fluctuations in wireless ad-hoc networks. In this problem, channel probing is followed by a transmission scheduling procedure executed independently within each link in the network. We study this problem for the popular block-fading channel model, where channel dependencies are inevitable between different time instances during the channel probing phase. Different from existing works, we explicitly consider this type of channel dependencies and its impact on the transmission scheduling and hence the system performance. We use optimal stopping theory to formulate this problem, but at carefully chosen time instances at which effective decisions are made. The problem can then be solved by a new stopping rule problem where the observations are independent between different time instances. Since the stopping rule problem has an implicit horizon determined by the network size, we first characterize the system performance using backward induction. We develop one recursive approach to solve the problem and show that the computational complexity is linear with respect to network size. Due to its computational complexity, we present an approximated approach for performance analysis and develop a metric to check how good the approximation is. We characterize the achievable system performance if we ignore the finite horizon constraint and design stopping rules based on the infinite horizon analysis nevertheless. We present an improved protocol to reduce the probing costs which requires no additional cost}
}
@techreport {
	title = {Nonlinear Programming Methods for Distributed Optimization},
	author = {Matei, Ion., Baras, John S.},
	year = {2015},
	month = {01/2015},
	abstract = {In this paper we investigate how standard nonlinear programming algorithms can be used to solve constrained optimization problems in a distributed manner. The optimization setup consists of a set of agents interacting through a communication graph that have as common goal the minimization of a function expressed as a sum of (possibly non-convex) differentiable functions. Each function in the sum corresponds to an agent and each agent has associated an equality constraint. By re-casting the distributed optimization problem into an equivalent, augmented centralized problem, we show that distributed algorithms result naturally from applying standard nonlinear programming techniques. Due to the distributed formulation, the standard assumptions and convergence results no longer hold. We emphasize what changes are necessary for convergence to still be achieved for three algorithms: two algorithms based on Lagrangian methods, and an algorithm based the method of multipliers. The changes in the convergence results are necessary mainly due to the fact that the (local) minimizers of the lifted optimization problem are not regular, as a results of the distributed formulation. Unlike the standard algorithm based on the method of multipliers, for the distributed version we cannot show that the theoretical superlinear convergence rate can be achieved.}
}
@techreport {
	title = {On the dynamics of linear functional differential equations with asymptotically constant solutions},
	author = {Somarakis, Christoforos., Baras, John S., Paraskevas, Evripidis.},
	year = {2015},
	month = {01/2015},
	abstract = {We discuss the dynamics of general linear functional differential equations with solutions that exhibit asymptotic constancy. We apply fixed point theory methods to study the stability of these solutions and we provide sufficient conditions of asymptotic stability with emphasis on the rate of convergence. Several examples are provided to illustrate the claim that the derived results generalize, unify and in some cases improve the existing ones.}
}
@techreport {
	title = {Stability by Fixed Point Theory in Time Delayed Distributed Consensus Networks},
	author = {Somarakis, Christoforos., Baras, John S., Paraskevas, Evripidis.},
	year = {2014},
	month = {09/2014},
	abstract = {We study the stability of linear time invariant distributed consensus dynamics in the presence of multiple propagation and processing delays. We employ fixed point theory (FPT) methods and derive sufficient conditions for asymptotic convergence to a common value while the emphasis is given in estimating the rate of convergence. We argue that this approach is novel in the field of networked dynamics as it is also flexible and thus capable of analyzing a wide variety of consensus based algorithms for which conventional Lyapunov methods are either too restrictive or unsuccessful.}
}
@techreport {
	title = {A non-consensus based distributed optimization algorithm},
	author = {Matei, Ion., Baras, John S.},
	year = {2014},
	month = {01/2014},
	abstract = {In this paper we introduce a discrete-time, distributed optimization algorithm executed by a set of agents whose interactions are subject to a communication graph. The algorithm can be applied to optimization costs that are expressed as sums of functions, where each function is associated to an agent. The algorithm can be applied to continuously differentiable cost functions, it is not consensus-based and is derived naturally by solving the first order necessary conditions of a lifted optimization problem with equality constraints. We show that, provided the agents{\textquoteright} initial values are sufficiently closed to a local minimizer and the step-size is sufficiently small, each agent converges to the local minimizer at a linear rate. In addition, we revisit two popular consensus-based distributed optimization algorithms and give sufficient conditions so that there use is extended to non-convex functions as well. We take a closer look at their rate of convergence and also show that unlike our algorithm, for a constant step-size, the consensus-based algorithms do not converge to a local minimizer even though the agents start close enough to the local minimizer}
}
@techreport {
	title = {Study of OLSR for Real-time Media Streaming over 802.11 Wireless Network in Software Emulation Environment},
	author = {Jain, Kaustubh., Somasundaram, Kiran K., Brian, K Wang., Baras, John S., Roy-Chowdhury, Ayan.},
	year = {2013},
	month = {12/2013},
	abstract = {In this paper we present a setup to study the real-time traffic carrying performance of Optimized Link State Routing (OLSR) protocol using software emulation. We emulate the IEEE 802.11 MAC/PHY using the EMANE software emulator, on a cluster of machines, for different multi-hop wireless scenarios. As an instance of real-world usage scenario, we study the performance of real-time streaming media over a mesh network supported by OLSR. In particular, we study the effect of mobility and background traffic on carried load and jitter. We propose to extend this emulation setup to test the real-time performance of prototype routing protocols such as Stable Path Topology Control (SPTC) and other real-time applications.}
}
@techreport {
	title = {A non-heuristic distributed algorithm for non-convex constrained optimization},
	author = {Matei, Ion., Baras, John S.},
	year = {2013},
	month = {12/2013},
	abstract = {In this paper we introduce a discrete-time, distributed optimization algorithm executed by a set of agents whose interactions are subject to a communication graph. The algorithm can be applied to optimization problems where the cost function is expressed as a sum of functions, and where each function is associated to an agent. In addition, the agents can have equality constraints as well. The algorithm can be applied to non-convex optimization problems with equality constraints, it is not consensus-based and it is not an heuristic. We demonstrate that the distributed algorithm results naturally from applying a first order method to solve the first order necessary conditions of an augmented optimization problem with equality constraints; optimization problem whose solution embeds the solution of our original problem. We show that, provided the agents{\textquoteright} initial values are sufficiently close to a local minimum, and the step-size is sufficiently small, under standard conditions on the cost and constraint functions, each agent converges to the local minimum at a linear rate.}
}
@techreport {
	title = {Development of a Framework for CPS Open Standards and Platforms},
	author = {Baras, John S., Austin, Mark A.},
	year = {2013},
	month = {11/2013},
	abstract = {This technical report describes a Framework we have developed through our research and investigations in this project, with the goal to facilitate creation of Open Standards and Platforms for CPS; a task that addresses a critical mission for NIST. The rapid development of information technology (in terms of processing power, embedded hardware and software systems, comprehensive IT management systems, networking and Internet growth, system design environments) is producing an increasing number of applications and opening new doors. In addition over the last decade we entered a new era where systems complexity has increased dramatically. Complexity is increased both by the number of components that are included in each system as well as by the dependencies between those components. Increasingly, systems tend to be more software dependent and that is a major challenge that engineers involved in the development of such systems face. The challenge is even greater when a safety critical system is considered, like an airplane or a passenger car. Software-intensive systems and devices have become everyday consumables. There is a need for development of software that is provably error-free. Thanks to their multifaceted support for networking and inclusion of data and services from global networks, systems are evolving to form integrated, overarching solutions that are increasingly penetrating all areas of life and work. When software dependent systems interact with the physical environment then we have the class of cyber-physical systems (CPS) [1, 2]. The challenge in CPS is to incorporate the inputs (and their characteristics and constraints) from the physical components in the logic of the cyber components (hardware and software). CPS are engineered systems constructed as networked interactions of physical and computational (cyber) components. In CPS, computations and communication are deeply embedded in and interacting with physical processes, and add new capabilities to physical systems. Competitive pressure and societal needs drive industry to design and deploy airplanes and cars that are more energy efficient and safe, medical devices and systems that are more dependable, defense systems that are more autonomous and secure. Whole industrial sectors are transformed by new product lines that are CPS-based. Modern CPSs are not simply the connection of two different kinds of components engineered by means of distinct design technology, but rather, a new system category that is both physical and computational [1, 2]. Current industrial experience tells us that, in fact, we have reached the limits of our knowledge of how to combine computers and physical systems. The shortcomings range from technical limitations in the foundations of cyber-physical systems to the way we organize our industries and educate engineers and scientists that support cyber-physical system design. If we continue to build systems using our very limited methods and tools but lack the science and technology foundations, we will create significant risks, produce failures and lead to loss of market. Nowadays, with increasing frequency we observe systems that cooperate to achieve a common goal, even though there were not built for that reason. These are called systems of systems. For example, the Global Positioning System (GPS) is a system by itself. However, it needs to cooperate with other systems when the air traffic control system of systems is under 3 consideration. The analysis and development of such systems should be done carefully because of the emergent behavior that systems exhibit when they are coupled with other systems. However, apart from the increasing complexity and the other technical challenges, there is a need to decrease time-to-market for new systems as well as the associated costs. This specific trend and associated requirements, which are an outcome of global competitiveness, are expected to continue and become even more stringent. If a successful contribution is to be made in shaping this change, the revolutionary potential of CPS must be recognized and incorporated into internal development processes at an early stage. For that Interoperability and Integratability of CPS is critical. In this Task we have developed a Framework to facilitate interoperability and integratability of CPS via Open Standards and Platforms. The purpose of this technical report is to introduce this Framework and its critical components, to provide various instantiations of it, and to describe initial successful applications of it in various important classes of CPS. An additional goal of publishing this technical report is to solicit feedback on the proposed Framework, and to catalyze discussions and interactions in the broader CPS technical community towards improving and strengthening this Framework. CPS integrate data and services from different systems which were developed independently and with disparate objectives, thereby enabling new functionalities and benefits. Currently there is a lack of well-defined interfaces that on the one hand define the standards for the form and content of the data being exchanged, but on the other hand take account of non-functional aspects of this data, such as differing levels of data quality or reliability. A similar situation exists with respect to tools and synthesis environments, although some work has been initiated in the latter. The technological prerequisite for the design of the aforementioned various functions and value added services of CPS is the interoperability and integratability of these systems as well as their capability to be adapted flexibly and application-specifically as well as extended at the different levels of abstraction. Dependent on the objective and scope of the application, it may be necessary to integrate component functions (Embedded Systems (ES), System of Systems (SoS), CPS), to establish communication and interfaces, and to ensure the required level of quality of interaction and also of the overall system behavior. This requires cross-domain concepts for architecture, communication and compatibility at all levels. The effects of these factors on existing or yet undeveloped systems and architectures represent a major challenge. Investigation into these factors is the objective of current national and international studies and research projects. CPS create core technological challenges for traditional system architectures, especially because of their high degree of connectivity. This is because CPS are not constructed for one specific purpose or function, but rather are open for many different services and processes, and must therefore be adaptable. In view of their evolutionary nature, they are only controllable to a limited extent. This creates new demands for greater interoperability and communication within CPS that cannot be met by current closed systems. In particular, the differences in the characteristics of embedded systems in relation to IT systems and services and data in networks lead to outstanding questions in relation to the form of architectures, the definition of system and communication interfaces and requirements for underlying CPS platforms with basic services and parallel architectures at different levels of abstraction. 4 The technological developments underlying CPS evolution require the development of standards in the individual application domains, as well as basic infrastructure investments that cannot be borne by individual companies alone. This is particularly significant for SMEs. The development and operation of uniform platforms to migrate individual services and products will therefore be as much of a challenge as joint specification standards. The creation of such quasi standards, less in the traditional mold of classic industry norms and standards and more in the sense of de facto standards that become established on the basis of technological and market dominance, will become an essential part of technological and market leadership. To summarize and emphasize, the complexity of the subject in terms of the required technologies and capabilities of CPS, as well as the capabilities and competences required to develop, control and design/ create innovative, usable CPS applications, demand fundamentally integrated action, interdisciplinarity (research and development, economy and society) and vertical and horizontal efforts in:  The creation of open, cross-domain platforms with fundamental services (communication, networking, interoperability) and architectures (including domainspecific architectures);  The complementary expansion and integration of application fields and environments with vertical experimentation platforms and correspondingly integrated interdisciplinary efforts;  The systematic enhancement with respect to methods and technologies across all involved disciplines to create innovative CPS. The aim of our research and investigations under this Task of the project, was precisely to clarify these objectives and systematically develop detailed recommendations for action. Our research and investigations have identified the following essential and fundamental challenges for the modeling, design, synthesis and manufacturing of CPS: (i) The creation and demonstration of a framework for developing cross-domain integrated modeling hubs for CPS. (ii) The creation and demonstration of a framework for linking the integrated CPS modeling hub of (i) with powerful and diverse tradeoff analysis methods and tools for design exploration for CPS. (iii) The creation of a framework of linking the integrated CPS synthesis environment of (i) and (ii) with databases of modular component and process (manufacturing) models, backwards compatible with earlier legacy systems; (iv)The creation of a framework for translating textual requirements to mathematical representations as constraints, rules and metrics involving both logical and numerical variables and the automatic (at least to 75\%) allocation of the resulting specifications to components of the CPS and of processes, in a way that allows traceability. 5 These challenges have been listed here in the order of increasing difficulty both conceptually and in terms of arriving at implementable solutions. The order also reflects the extent to which the current state of affairs has made progress towards developing at least some initial instantiations of the desired frameworks. In this context, it is useful to compare with the advanced state of development of similar frameworks and their instantiations for synthesis and manufacturing of complex microelectronic VLSI chips including distributed ones, which have been available as integrated tools by several vendors for at least a decade. Regarding challenge (i) we have performed extensive work and research in this project towards developing model-based systems engineering (MBSE) procedures for the design, integration, testing and operational management of cyber-physical systems, that is, physical systems with cyber potentially embedded in every physical component. Thus in the Framework, described in this report, for standards for integrated modeling hubs for CPS, MBSE methods and tools are prominent. Regarding the search for a framework for standards for CPS this selection has the additional advantage that it is also emerging as an accepted framework for systems engineering by all industry sectors with substantial interest in CPS [3, 7]. Regarding challenge (ii) we have performed extensive work and research in this project towards developing the foundations for such an integration, and we have developed and demonstrated the first ever integration of a powerful tradeoff analysis tool (and methodology) with our SysMLIntegrated system modeling environments for CPS synthesis [3, 7]. Primary applications of interest that we have instantiated this framework are: microgrids and power grids, wireless sensor networks (WSN) and applications to Smart Grid, energy efficient buildings, microrobotics and collaborative robotics, and the overarching (for all these applications) security and trust issues including our pioneering and innovative work on compositional security systems. A key concept here is the integration of multi-criteria, multi constraint optimization with constrained based reasoning. Regarding challenge (iii) we have only developed the conceptual Framework, as any required instantiations will require substantial commercial grade software development beyond the scope of this project. It is clear however that object-relational databases and database mediators (for both data and semantics) will have to be employed. Regarding challenge (iv) we have developed a Framework for checking and validating specifications, after they have been translated to their mathematical representations as constraints and metrics with logical and numerical variables. Various multi-criteria optimization, constrained based reasoning, model checking and automatic theorem proving tools will have to be combined. The automatic annotation of the system blocks with requirements and parameter specifications remains an open challenge.}
}
@techreport {
	title = {Distributed Algorithms for Optimization Problems with Equality Constraints},
	author = {Matei, Ion., Baras, John S.},
	year = {2013},
	month = {09/2013},
	abstract = {In this paper we introduce two discrete-time, distributed optimization algorithms executed by a set of agents whose interactions are subject to a communication graph. The algorithms can be applied to optimization problems where the cost function is expressed as a sum of functions, and where each function is associated to an agent. In addition, the agents can have equality constraints as well. The algorithms are not consensus-based and can be applied to non-convex optimization problems with equality constraints. We demonstrate that the first distributed algorithm results naturally from applying a first order method to solve the first order necessary conditions for a lifted optimization problem with equality constraints; the solution of our original problem is embedded in the solution of this lifted optimization problem. We show that, provided the agents{\textquoteright} initial values are sufficiently close to a local minimizer, and the step-size is sufficiently small, under standard conditions on the cost and constraint functions, each agent converges to the local minimizer at a linear rate. Next, we use an augmented Lagrangian idea to derive a second distributed algorithm whose local convergence requires weaker sufficient conditions than in the case of the first algorithm.}
}
@techreport {
	title = {A Distributed Learning Algorithm with Bit-valued Communications for Multi-agent Welfare Optimization},
	author = {Menon, Anup., Baras, John S.},
	year = {2013},
	month = {07/2013},
	abstract = {A multi-agent system comprising N agents, each picking actions from a finite set and receiving a payoff that depends on the action of the whole, is considered. The exact form of the payoffs are unknown and only their values can be measured by the respective agents. A decentralized algorithm was proposed by Marden et. al. [1] and in the authors{\textquoteright} earlier work [2] that, in this setting, leads to the agents picking welfare optimizing actions under some restrictive assumptions on the payoff structure. This algorithm is modified in this paper to incorporate exchange of certain bit-valued information between the agents over a directed communication graph. The notion of an interaction graph is then introduced to encode known interaction in the system. Restrictions on the payoff structure are eliminated and conditions that guarantee convergence to welfare minimizing actions w.p. 1 are derived under the assumption that the union of the interaction graph and communication graph is strongly connected.}
}
@techreport {
	title = {A Fixed Point Theory Approach to Multi-Agent Consensus Dynamics With Delays},
	author = {Somarakis, Christoforos., Baras, John S.},
	year = {2013},
	month = {02/2013},
	abstract = {The classic linear time-invariant multi-agent consensus scheme is revisited in the presence of constant and distributed bounded delays. We create a fixed point argument and prove exponential convergence with specific rate that depends both on the topology of the communication graph and the upper bound of the allowed delay.}
}
@techreport {
	title = {Compositional Analysis of Dynamic Bayesian Networks and Applications to CPS},
	author = {Yang, Shahan., Zhou, Yuchen., Baras, John S.},
	year = {2012},
	month = {12/2012},
	abstract = {Dynamic Bayesian networks (DBNs) can be effectively used to model various problems in complex dynamic systems. We perform an empirical investigation on compositional analysis of DBNs using abstraction. In static systems and hidden Markov models, computation of a metric called treewidth induces a tree decomposition that can be used to perform logical or probabilistic inference and max + optimizations in time exponential in treewidth and linear in overall system size. Intuitively, the linear scaling means that very large systems can be analyzed as long as they are sufficiently sparse and well structured. In these simple cases, summary propagation, which uses two operations, summation (projection) and product (composition), suffices to perform the inference or optimization. Here, we begin an extension of this to structured networks of communicating dynamic systems. We define generalizations of projection and composition operators that treat labeled Markov chains as primitive objects. The projection operation, corresponding to summation, is implemented as label deletion followed by exact state reduction for Markov chains, similar to Hopcroft{\textquoteright}s DFA minimization algorithm, with O(n log m) complexity. The composition operation is the product of state machines. We use canonical MDDs, similar to BDDs, to capture logical dependencies symbolically. Combining symbolic representations with Markov chain lumping algorithms is a novel contribution. Using this approach, we have created a tool leveraging model based systems engineering technologies. The communicating Markov chains are specified using UML Statecharts via Papyrus extended using an ANTLR parsed domain specific language (DSL). The tool reduces the number of states in networks of Markov chains by several orders of magnitude. In one example, a network having a product state space of more than 600 million states is reduced to about 500 states. A feature of this technique is that the state space is examined incrementally, meaning that the full state space is never explicitly represented, even as an input to the reduction algorithm. The primary reduction appears to come from symmetry which is surprising because the technique includes no explicit symmetry handling. We note that composition is efficient at least for systems with high symmetry. We describe applications to a hospital intensive care unit (ICU) from a systems engineering perspective.}
}
@techreport {
	title = {Flow Control in Time-Varying, Random Supply Chains},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {05/2012},
	abstract = {Today{\textquoteright}s supply chains are more and more complex. They depend on a network of independent, yet~interconnected moving parts. They rely on critical infrastructures and experience a lot of time variability~and randomness. Designing strategies that deal with such constantly changing supply chains is necessary~in this increasingly globalized economy where supply chain disruptions have impacts that propagate not~only locally but also globally. In this paper we propose a randomized flow control algorithm for a time~varying, random supply chain network. We formulate a constrained stochastic optimization problem that~maximizes the profit function in terms of the long-run, time-average rates of the flows in the supply~chain. We show that our algorithm, which is based on queueing theory and stochastic analysis concepts,~can get arbitrarily close to the solution of the aforementioned optimization problem. In addition, we~describe how the flow control algorithm can be extended to a multiple firms supply chain setup and~present numerical simulations of our algorithm for different supply chain topologies.}
}
@techreport {
	title = {A performance comparison between two consensus-based distributed optimization algorithms},
	author = {Matei, Ion., Baras, John S.},
	year = {2012},
	month = {05/2012},
	abstract = {In this paper we address the problem of multi-agent optimization for convex functions expressible as sums of convex functions. Each agent has access to only one function in the sum and can use only local information to update its current estimate of the optimal solution. We consider two consensus-based iterative algorithms, based on a combination between a consensus step and a subgradient decent update. The main difference between the two algorithms is the order in which the consensus-step and the subgradient descent update are performed. We show that updating first the current estimate in the direction of a subgradient and then executing the consensus step ensures better performance than executing the steps in reversed order. In support of our analytical results, we give some numerical simulations of the algorithms as well.}
}
@techreport {
	title = {A randomized gossip consensus algorithm on convex metric spaces},
	author = {Matei, Ion., Somarakis, Christoforos., Baras, John S.},
	year = {2012},
	month = {02/2012},
	abstract = {A consensus problem consists of a group of dynamic agents who seek to agree upon certain quantities of interest. This problem can be generalized in the context of convex metric spaces that extend the standard notion of convexity. In this paper we introduce and analyze a randomized gossip algorithm for solving the generalized consensus problem on convex metric spaces. We study the convergence properties of the algorithm using stochastic differential equations theory. We show that the dynamics of the distances between the states of the agents can be upper bounded by the dynamics of a stochastic differential equation driven by Poisson counters. In addition, we introduce instances of the generalized consensus algorithm for several examples of convex metric spaces together with numerical simulations.}
}
@techreport {
	title = {Distributed Topology Control for Stable Path Routing in Multi-hop Wireless Networks},
	author = {Somasundaram, Kiran K., Baras, John S., Jain, Kaustubh., Tabatabaee, Vahid.},
	year = {2010},
	month = {07/2010},
	abstract = {In this paper, we introduce the topology control problem for stable path routing in mobile multi-hop networks. We formulate the topology control problem of selective linkstate broadcast as a graph pruning problem with restricted local neighborhood information. We develop a multi-agent optimization framework where the decision policies of each agent are restricted to local policies on incident edges and independent of the policies of the other agents. We show that under a condition called the positivity condition, these independent local policies preserve the stable routing paths globally. We then provide an efficient algorithm to compute an optimal local policy that yields a minimal pruned graph, which we call the Stable Path Topology Control (SPTC) algorithm. Using simulations, we demonstrate that this algorithm, when used with the popular ETX metric, has lesser control overhead and the resulting pruned routing paths carry more upper layer traffic when compared with other topology control mechanisms commonly used for Mobile Ad Hoc Networks.}
}
@techreport {
	title = {The asymptotic consensus problem on convex metric spaces},
	author = {Matei, Ion., Baras, John S.},
	year = {2010},
	month = {04/2010},
	abstract = {We consider the consensus problem of a group of dynamic agents whose communication network is modeled by a directed time-varying graph. In this paper we generalize the asymptotic consensus problem to convex metric spaces. A convex metric space is a metric space on which we define a convex structure. Using this convex structure we define convex sets and in particular the convex hull of a (finite) set. Under minimal connectivity assumptions, we show that if at each iteration an agent updates its state by choosing a point from a particular subset of the convex hull generated by the agent{\textquoteright}s current state and the states of his/her neighbors, then the asymptotic agreement is achieved. In addition, we give bounds on the distance between the consensus point(s) and the initial values of the agents. As application example, we use this framework to introduce an iterative algorithm for reaching consensus of opinion. In this example, the agents take values in the space of discrete random variable on which we define an appropriate metric and convex structure. For this particular convex metric space we provide a more detail analysis of the convex hull generated by a finite set points. In addition we give some numerical simulations of the consensus of opinion algorithm.}
}
@techreport {
	title = {Distributed Topology Control for Stable Path Routing in Mobile Ad Hoc Networks},
	author = {Somasundaram, Kiran K., Jain, Kaustubh., Tabatabaee, Vahid., Baras, John S.},
	year = {2010},
	month = {03/2010},
	abstract = {In this paper, we introduce the stable path topology control problem for routing in Mobile Ad Hoc Networks (MANETs). We formulate the problem as a constrained multiagent optimization problem with only local neighborhood information. We develop and prove local pruning strategies that solve this problem. We also introduce the notion of distorted pruning, which offers a systematic method to trade path stability off against the hop count metric. Finally, we quantify the performance of our pruning algorithms using several simulation scenarios.}
}
@techreport {
	title = {Path Optimization Techniques for Trusted Routing in Mobile Ad-Hoc Networks: An Interplay Between Ordered Semirings},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2010},
	month = {02/2010},
	abstract = {In this paper, we formulate the problem of trusted routing as a transaction of services over a complex networked environment. We present definitions from service-oriented environments which unambiguously capture the difference between trust and reputation relations. We show that the trustworthiness measures associated with these relations have a linear order embedded in them. Identifying this order structure permits us to treat the trusted routing problem as a bi-objective path optimization problem. Further, we present polynomial time solutions to obtain the optimal routing paths in various biobjective settings. In developing these algorithms, we identify an interesting semiring decomposition principle that yields a distributed solution.}
}
@techreport {
	title = {Pareto Nash Replies for Multi-Objective Games},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {11/2009},
	abstract = {We observe the notions of Pareto Nash strategies and their relations to multiparametric linear programming has made repeated appearances the game theory literature. . What we contribute . We feel that the theory of MOG has significant potential to model several practical scenarios especially in the context of networked communications}
}
@techreport {
	title = {Convergence Results for Ant Routing Algorithms via Stochastic Approximation},
	author = {Purkayastha, Punyaslok., Baras, John S.},
	year = {2009},
	month = {10/2009},
	abstract = {In this paper, we provide convergence results for an Ant-Based Routing (ARA) Algorithm for wireline, packet-switched communication networks, that are acyclic. Such algorithms are inspired by the foraging behavior of ants in nature. We consider an ARA algorithm proposed by Bean and Costa [2]. The algorithm has the virtues of being adaptive and distributed, and can provide a multipath routing solution. We consider a scenario where there are multiple incoming data traffic streams that are to be routed to their respective destinations via the network. Ant packets, which are nothing but probe packets, are introduced to estimate the path delays in the network. The node routing tables, which consist of routing probabilities for the outgoing links, are updated based on these delay estimates. In contrast to the available analytical studies in the literature, the link delays in our model are stochastic, time-varying, and dependent on the link traffic. The evolution of the delay estimates and the routing probabilities are described by a set of stochastic iterative equations. In doing so, we take into account the distributed and asynchronous nature of the algorithm operation. Using methods from the theory of stochastic approximations, we show that the evolution of the delay estimates can be closely tracked by a deterministic ODE (Ordinary Differential Equation) system, when the step-size of the delay estimation scheme is small. We study the equilibrium behavior of the ODE system in order to obtain the equilibrium behavior of the routing algorithm. We also explore properties of the equilibrium routing probabilities, and provide illustrative simulation results.}
}
@techreport {
	title = {Distributed subgradient method under random communication topology - the effect of the probability distribution of the random graph on the performance metrics},
	author = {Matei, Ion., Baras, John S.},
	year = {2009},
	month = {09/2009},
	abstract = {In this note we study the performance metrics (rate of convergence and guaranteed region of convergence) of a multi-agent subgradient method for optimizing a sum of convex functions. We assume that the agents exchange information according to a communication topology modeled as a random graph, independent of other time instances. Under a strong convexity type of assumption, we express the performance metrics directly as functions of the estimates of the optimal decision vector. We emphasize how the probability distribution of the random graph affects the upper bounds on the performance metrics. This provide a guide for tuning the parameters of the communication protocol such that good performance of the multi-agent subgradient method is ensured. We perform the tuning of the protocol parameters for two communication scenarios. In the first scenario, we assume a randomized scheme for link activation with no-error transmissions while in the second scenario we use a pre-established order of transmissions but we consider the interference effect. Both these scenarios are applied on a small world type of topology.}
}
@techreport {
	title = {Semiring Pruning for Information Dissemination in Mobile Ad Hoc Networks},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {08/2009},
	abstract = {Link state routing mechanisms have shown good convergence behaviour with mobile hosts. Pruning methods such as those used in Optimized Link State Routing (OLSR) have showed good throughput behaviour when compared to traditional link-state approaches which suffered from broadcast storm problems. In this paper, we show that the pruning function is a fundamental component of link-state routing protocols for mobile networks. We also show that this component architecture aids in interpreting both distance vector and link-state approaches under a common framework. We develop a class of pruning methods for many of the most commonly used routing objectives and show that these pruning methods are a special case of the semiring distribution property.}
}
@techreport {
	title = {Path Optimization Techniques for Trusted Routing in Tactical Mobile Ad-Hoc Networks},
	author = {Somasundaram, Kiran K., Baras, John S.},
	year = {2009},
	month = {03/2009},
	abstract = {Over the past decade a lot of research effort has been invested in trying to understand security principles for Mobile Ad-Hoc Networks (MANETs). Among the various problems that the research community has focussed, a particularly interesting problem is that of trusted routing in MANETs. Unlike in traditional networks like the Internet, the information flow in a MANET is not restricted to a certain class of routing nodes. The MANETs are different in this sense, because every node acts as a potential relay node. Thus for the proper functioning of any higher layer protocols in MANETs it is of paramount importance that the mobile ad hoc nodes co-operate in routing and forwarding. In many practical scenarios where MANETs are deployed, it might be advantageous for individual nodes not to participate in this forwarding game. Thus one might expect under an unsupervised or unmonitored scenario, the network essentially breaks into components with similar interest groups. This raises the major issue of connectivity in a MANET which is a primitive requirement for the routing layer. Thus securing the network from self-interest groups is inherently coupled with the security of the routing layer. This particular observation has spawned several interesting works in the recent past.}
}
@techreport {
	title = {Sensor Scheduling using Smart Sensors},
	author = {Hovareshti, Pedram., Gupta, Vijay., Baras, John S.},
	year = {2007},
	month = {07/2007},
	abstract = {The sensor selection problem arises when multiple sensors are jointly trying to estimate a process but only a subset of them can take and/or use measurements at any time step. In a networked estimation situation, sensors are typically equipped with some memory and processing capabilities. We illustrate that utilization of these capabilities can lead to significant performance gains in the sensor selection problem for improved inference. Further, it also leads to significant pruning of the search tree that yields the optimum sensor schedule. We also present a periodicity result for the case where the decision is whether the sensor should transmit or not.}
}
@techreport {
	title = {Multiple Sampling for Estimation on a Finite Horizon},
	author = {Rabi, Maben., Moustakides, George V.},
	year = {2006},
	month = {01/2006},
	abstract = {We discuss some multiple sampling problems that arise in real-time estimation problems with limits on the number of samples. The quality of estimation is measured by an aggregate squared error over a finite horizon. We compare the performances of the best detereministic, level-triggered and the optimal sampling schemes. We restrict the signal to be either a Wiener process or an Ornstein-Uhlenbeck process. For the Wiener process, we provide closed form expressions and series expansions. For the Ornstein Uhlenbeck process, we provide procedures for numerical computation. Our results show that level-triggered sampling is almost optimal when the signal is stable.},
	number = {Number: ISR TR 2006-7}
}
@techreport {
	title = {Efficient Sampling for Keeping Track of an Ornstein-Uhlenbeck Process},
	author = {Rabi, Maben., Moustakides, George V.},
	year = {2006},
	month = {01/2006},
	abstract = {We consider estimation and tracking problems in sensor networks with constraints in the hierarchy of inference making, on the sharing of data and inter-sensor communications. We identify as a typical representative for such problems tracking of a process when the number and type of measurements in constrained. As the simplest representative of such problems, which still encompasses all the key issues involved we analyze efficient sampling schemes for tracking an Ornstein-Uhlenbeck process. We considered sampling based on time, based on amplitude (event-triggered sampling) and optimal sampling (optimal stopping). We obtained the solution in each case as a constrained optimization problem. We compare the performance of the various sampling schemes and show that the event-triggered sampling performs close to optimal. Implications and extensions are discussed.},
	number = {Number: ISR TR 2006-3}
}
@techreport {
	title = {Consensus Problems on Small World Graphs: A Structural Study},
	author = {Hovareshti, Pedram.},
	year = {2006},
	month = {01/2006},
	abstract = {Consensus problems arise in many instances of collaborative control of multi-agent complex systems; where it is important for the agents to act in coordination with the other agents. To reach coordination, agents need to share information. In large groups of agents the information sharing should be local in some sense, due to energy limitation, reliability, and other constraints. A consensus protocol is an iterative method that provides the group with a common coordination variable. However, local information exchange limits the speed of convergence of such protocols. Therefore, in order to achieve high convergence speed, we should be able to design appropriate network topologies. A reasonable conjecture is that the small world graphs should result in good convergence speed for consensus problems because their low average pairwise path length should speed the diffusion of information in the system. In this paper we address this conjecture by simulations and also by studying the spectral properties of a class of matrices corresponding to consensus problems on small world graphs.},
	number = {Number: ISR TR 2006-10}
}
@techreport {
	title = {Detection of Greedy Individual and Colluding MAC Layer Attackers},
	author = {Radosavac, Svetlana., Cardenas, Alvaro A., Moustakides, George V.},
	year = {2006},
	month = {01/2006},
	abstract = {Selfish behavior at the Medium Access (MAC) Layer can have devastating side effects on the performance of wireless networks, with effects similar to those of Denial of Service (DoS) attacks. In this paper we consider the problem of detection and prevention of node misbehavior at the MAC layer, focusing on the back-off manipulation by selfish nodes. We propose an algorithm that ensures honest behavior of non-colluding participants. Furthermore, we analyze the problem of colluding selfish nodes, casting the problem within a minimax robust detection framework, providing a detection rule of optimum performance for the worst-case attack. Finally, we compare the effects of colluding attackers with a single attacker in terms of the detection delay. Although our approach is general and can serve as a guideline for the design of any probabilistic distributed MAC protocol, we focus our analysis on the IEEE 802.11 MAC.},
	number = {Number: ISR TR 2006-8}
}
@techreport {
	title = {Interactive Data Services in Wireless Access Networks: Capacity Planning and Protocols},
	author = {Zhou, Xiaoming., Raissi-Dekhordi, Majid.},
	year = {2005},
	month = {01/2005},
	abstract = {In this paper, we study the capacity planning in wireless access network for interactive data services such as web browsing. A closed queuing model has been developed which can capture the bottleneck effects in both the forward and the reverse channels. The model can be used to calculate the average throughput, the average response time and the number of users the system can support. We evaluate the performance of several MAC protocols such as slotted Aloha, static TDMA, Aloha/periodic stream and combined free demand assignment multiple access (CFDAMA) using realistic web traffic models. Based on the performance evaluation, we propose a new MAC protocol and a new transport layer protocol. Our new MAC protocol called combined polling free demand assignment multiple access (CPFDAMA) explores the correlation between forward channel data packets and reverse channel acknowledgement packets. Our new transport layer protocol called RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion management. RWBP can eliminate congestion losses inside the wireless networks. Our protocol suite outperforms the proposed protocols in term of both channel utilization and response time. Our results can be used for service providers to dimension their networks and provide quality of service to a certain number of users.},
	number = {Number: CSHCN TR 2005-5}
}
@techreport {
	title = {Fault-Tolerant Extension of Hypercube Algorithm for Efficient, Robust Group Communications in MANETs},
	author = {Striki, Maria.},
	year = {2005},
	month = {01/2005},
	abstract = {Securing multicast communications in Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless networking and security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security on the other hand, is becoming an indispensable requirement of our modern life for all these applications. However, the limitations of the dynamic, infrastructure-less nature of MANETs impose major difficulties in establishing a secure framework suitable for group communications. The design of efficient key management (KM) schemes for MANET is of paramount importance, since the performance of the KM functions (key generation, entity authentication, key distribution/agreement) imposes an upper limit on the efficiency and scalability of the whole secure group communication system. In this work, we contribute towards efficient, robust and scalable, secure group communications for MANETs, by extending an existing key agreement (KA) scheme (where all parties contribute equally to group key generation) {\textendash}Hypercube - to tolerate multiple member failures with low cost, through its integration with a novel adaptively proactive algorithm. We assume that the participating users have already been authenticated via some underlying mechanism and we focus on the design and analysis of a fault-tolerant Hypercube, with the aim to contribute to the robustness and efficiency of Octopus-based schemes (an efficient group of KA protocols for MANETs using Hypercube as backbone). We compare our algorithm with the existing approach, and we evaluate the results of our analysis. Through our analysis and simulation results we demonstrate how the new Hypercube algorithm enhances the robustness of the Octopus schemes maintaining their feasibility in MANETs at the same time.},
	number = {Number: CSHCN TR 2005-108}
}
@techreport {
	title = {Hybrid Networks with a Space Segment - Topology Design and Security issues},
	author = {Roy-Chowdhury, Ayan., Hadjitheodosiou, Michael., Rentz, Nicolas.},
	year = {2005},
	month = {01/2005},
	abstract = {In this paper we investigate a hybrid network topology that is suitable for supporting interplanetary communications. We define an architecture comprised of a network of sensor nodes on a remote planetary surface, connected to a hybrid terrestrial network of wired and wireless LANs through a series of satellite relays. All the nodes in the network are IPaddressable and support public and symmetric key cryptography. The resulting network forms a hierarchical hybrid mesh that connects users on Earth to networks on or around a remote planetary surface. We describe the design of the network and present preliminary simulation results illustrating the network performance for various parameters. We also discuss how algorithms for user authentication, message integrity and data confidentiality can be incorporated in the network infrastructure for secure end-to-end communication.},
	number = {Number: CSHCN TR 2005-6}
}
@techreport {
	title = {Network Tomography},
	author = {Gavilanez, Franklin. , Berenstein, Carlos A., Baras, John S.},
	year = {2005},
	month = {01/2005},
	abstract = {While conventional tomography is associated to the Radon transform in Euclidean spaces, electrical impedance tomography or EIT is associated to the Radon transform in the hyperbolic plane. We discuss some recent work on network tomography that can be associated to a problem similar to EIT on graphs and indicate how in some sense it may be also associated to the Radon transform on trees.},
	number = {Number: ISR TR 2005-70}
}
@techreport {
	title = {A Certificate-Based Light-Weight Authentication Algorithm For Resource-Constrained Devices},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2005},
	month = {01/2005},
	abstract = {In this work, we analyze and extend a recently proposed design of digital certificates called TESLA certificates. Certificates are a necessary tool in today{\textquoteright}s secure networks to certify the identity of nodes taking part in communication. Most prevalent certificate technologies make use of public-key cryptography. Messages generated by the user are signed using its private key, and the signature can be verified by any node who knows the user{\textquoteright}s public key via its certificate. Signature generation and verification using public-key cryptography is computationally expensive for devices with limited computation power and energy resources. In this situation TESLA certificates can be very useful to certify identity, since they rely on symmetric cryptography which is computationally much more efficient. In this paper we explain the concept of TESLA certificates and provide a preliminary description of proposed modifications to the original algorithm to strengthen its security. We extend the original proposal by combining hash chains with TESLA certificates and come up with an efficient source and message authentication protocol based on symmetric key certificates. We also propose a new type of TESLA certificates called Group Certificates for use in multicast group communication. Through analysis, we show that our protocol is secure against malicious adversaries. We also give an initial estimate of the performance of our algorithm and the related comparison to public-key signatures, and we highlight network scenarios where the TESLA certificates could be particularly useful.},
	number = {Number: CSHCN TR 2005-4}
}
@techreport {
	title = {A Robust, Distributed TGDH-based Scheme for Secure Group Communications in MANETs},
	author = {Striki, Maria.},
	year = {2005},
	month = {01/2005},
	abstract = {Through our analysis and results we shed more insight on the actual feasibility of these protocols for MANETs and provide more realistic and {\textquotedblleft}fair{\textquotedblright} comparison results that more accurately advocate the pros and cons of each protocol over the environment of interest.},
	number = {Number: CSHCN TR 2005-9}
}
@techreport {
	title = {An Analysis of Delay-Constrained Opportunistic Scheduling for Cellular Wireless Systems},
	author = {Srinivasan, Roshni.},
	year = {2004},
	month = {01/2004},
	abstract = {In this work, we focus primarily on the trade-off between the realization of multiuser diversity gain and the provision of delay guarantees. Our main contribution is an analytical characterization of the distributions of the delay and rate offered by an opportunistic scheduler. The scheduling metric used in the algorithm combines the rate requested by the user and scheduling delay in a general form. Our analysis of a wireless system with a finite number of users in discrete time is strongly supported by system simulations of a time-slotted cellular downlink shared by multiple mobile users with independent, fading channels. We also compute closed form expressions for the scheduler statistics using a continuous approximation. The results in this paper can be used to evaluate system performance and provision resources to support Quality of Service (QoS) guarantees in broadband wireless networks.},
	number = {Number: CSHCN TR 2004-2}
}
@techreport {
	title = {Web access over a multiple access channel: evaluations and improvements},
	author = {Zhou, Xiaoming., Liu, Nelson X.},
	year = {2004},
	month = {01/2004},
	abstract = {We evaluate web browsing performance over a multiple access satellite channel for three different MAC layer protocols. A web user behavior model is used to generate realistic source traffic. A new transport layer protocol called RWBP is proposed to solve the TCP problems inside satellite networks. RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion control. We compare its performance with TCP over the three multiple access protocols. Our simulation results show that RWBP can reduce the multiple access channel load and at the same time improve the web page response time when driven by realistic web traffic. For the MAC layer protocols, combined free demand assignment multiple access (CFDAMA) always performs better than the other two protocols.},
	number = {Number: CSHCN TR 2004-10}
}
@techreport {
	title = {Multicast-aware Power Allocation in Multiple Spot-Beam Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We address the problem of optimizing resource sharing and flow control in a multiple spot-beam broadband satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and direct access to large number of users, clearly have an inherent advantage in supporting multicast applications. In order to remain competitive against other broadband technologies, however, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that, in a multiple spot-beam system, a high load variation across spot-beam queues may force lower allocated session rates for active flows, and be perceived as unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization framework for balancing the spot-beam queue service rates such that the sum of the rate variances of all active multicast flows is minimized. This is achieved through the re-distribution of system power among spot-beam queues, by taking into account the load on the queues and the channel states. We conclude that it is possible to increase the average session rates of multicast flows by up to 16\%, and the rates of unicast flows by up to 4\% after this optimization is applied.},
	number = {Number: CSHCN TR 2004-19}
}
@techreport {
	title = {A Multichannel Random Access Protocol for Multislot Short Messages with Delay Constraints},
	author = {Zhou, Xiaoming.},
	year = {2004},
	month = {01/2004},
	abstract = {A multichannel random access protocol called FMCSA for multislot short messages is proposed in this paper to be used in access networks with large propagation delay. This protocol combines random access with the use of packet level forward error correction coding for new messages and scheduled retransmissions for partially received messages. Analytical and simulation results show that FMCSA can achieve a higher throughput and lower delay than slotted Aloha. When the system is operating at the low load region, the short messages can be delivered in their first attempts with very high probability. With the load increasing, more messages will be received partially in their first attempts and the scheduled retransmission scheme will guarantee the partially received messages to be recovered in their second attempts. Therefore the delay performance of FMCSA is much more robust to the load fluctuation than slot Aloha.},
	number = {Number: CSHCN TR 2004-14}
}
@techreport {
	title = {Load balancing in multi-beam satellite systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We propose an approach to optimize resource sharing and in a multi-beam broadband satellite system that supports both unicast and multicast flows. We show that in this architecture, the load on every spot-beam queue could be different, depending on the type of the flows and the distribution of the receivers across spot-beam coverage areas. This load unbalance may significantly under-utilize the system resources and decrease the system throughput when both unicast and multicast flows are active in the system. In this paper, we formulate an optimization problem for intra- and inter-beam resource sharing such that the variance of the session rates experienced by users of a flow located in different beam coverage areas is minimized. The result of our resource allocation also determines the maximum sustainable rate of each flow. We calculate the beam utilization and maximum sustainable sessions rates with and without optimization and compare the results. We conclude that this method significantly improves the session rates and overall utilization of the system when both unicast and multicast flows are active.},
	number = {Number: CSHCN TR 2004-9}
}
@techreport {
	title = {Power Balancing in Multiple Spot-Beam Satellite Systems for Multicast Support},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {We address the problem of optimizing resource sharing and flow control in a multiple spot-beam broadband satellite system that supports both unicast and multicast flows. Satellite communication systems, with their wide-area coverage and ubiquitous access to large number of users, clearly have an inherent advantage in supporting distributed applications that require concurrent transmission of content to multiple users. In order to remain competitive against other broadband technologies, next generation satellite systems will be required to support both unicast and multicast flows and offer optimal sharing of system resources between these flows. We show that a high load variation across the spot-beam queues may significantly under-utilize the system and be perceived unsatisfactory by potential users when both unicast and multicast flows are active in the system. We propose an optimization based-approach to balance the load in the system and conclude that it is possible to increase the average session rates of all active flows by up to 30\% after this optimization is applied.},
	number = {Number: CSHCN TR 2004-15}
}
@techreport {
	title = {A Multiple Subset Sum Formulation for Feedback Implosion Suppression over Satellite Networks},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2004},
	month = {01/2004},
	abstract = {In this paper, we present a feedback implosion suppression (FIS) algorithm that reduces the volume of feedback information transmitted through the network without relying on any collaboration between users, or on any infrastructure other than the satellite network. Next generation satellite systems that utilize the Ka frequency band are likely to rely on various fade mitigation (compensation) techniques ranging from adaptive coding to dynamic power control, in order to guarantee a service quality that is comparable to other broadband technologies. User feedback would be a valuable input for a number of such components, however, collecting periodic feedback from a large number of users would result in the well-known feedback implosion problem. Feedback implosion is identified as a major problem when a large number of users try to transmit their feedback messages through the network, holding up a significant portion of the uplink resources and clogging the shared uplink medium. In this paper, we look at a system where uplink channel access is organized in time-slots. The goal of the FIS algorithm is to reduce the number of uplink time-slots hold up for the purpose of feedback transmission. Our analysis show that the FIS algorithm effectively suppresses the feedback messages of 95\% of all active users, but still achieves acceptable performance results when the ratio of available time-slots to number of users is equal to or higher than 5\%.},
	number = {Number: CSHCN TR 2004-21}
}
@techreport {
	title = {Providing Full Connectivity in Large Ad-Hoc Networks by Dynamic Placement of Aerial Platforms},
	author = {Karthikeyan Chadrashekar, Raissi-Dekhordi, Majid.},
	year = {2004},
	month = {01/2004},
	abstract = {In this paper we address the problem of providing full connectivity to disconnected ground MANET nodes by dynamically placing unmanned aerial vehicles (UAVs) to act as relay nodes. We provide a heuristic algorithm to find the minimal number of such aerial vehicles required to provide full connectivity and find the corresponding locations for these aerial platforms (UAVs). We also track the movement of the ground nodes and update the location of the UAVs. We describe a communication framework that enables the ground nodes to communicate with its peer ground nodes as well as the UAVs that act as relay nodes. The communication architecture is designed to work with existing MANET routing protocols.},
	number = {Number: CSHCN TR 2004-11}
}
@techreport {
	title = {A Parallel Virtual Queue Structure for Active Queue Management},
	author = {Jou,  Jia-Shiang., Tan, Xiaobo.},
	year = {2003},
	month = {01/2003},
	abstract = {The performance of the Adaptive RED scheme is susceptible to bursty web traffic. In this paper a parallel virtual queue structure is proposed for active queue management at the bottleneck router. Real time connections such as web and UDP, and non-real time connections such as FTP are served in two different virtual queues with drop-tail and Adaptive RED policies, respectively. Both queues share the same physical buffer memory. Simulation shows that file delivery for the web traffic is greatly improved due to shorter packet delay and lower packet loss rate, and that the queue length variation for the FTP traffic is small. To improve the goodput of the non-real time connections, a modified Adaptive RED scheme with dynamic queue length thresholds is also proposed. This scheme is able to keep the packet dropping probability within a desired small region. Stability of the queue length under this scheme is studied through analysis and numerical computation.},
	number = {Number: CSHCN TR 2003-18}
}
@techreport {
	title = {Key Distribution Protocols for Multicast Group Communication in MANETs},
	author = {Striki, Maria.},
	year = {2003},
	month = {01/2003},
	abstract = {In this work we will attempt to combine these protocols with all the possible combinations into a two-layered hybrid scheme that exploits adavantages of both protocols and reduces possibly their overhead. We will develop models of these combinations, redefine their function principles and we will do a mathematical analysis to derive all costs. The analytical formulae of these models will provide us with the tools for comparisons among them, and push the research towards the best behaving models.},
	number = {Number: CSHCN TR 2003-10}
}
@techreport {
	title = {A Reliable Multicast Transport Protocol for Satellite Communication Systems},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we propose a reliable multicast transport protocol for satellite communication systems. Many of the emerging applications in the Internet would benefit from reliable multicast services, and broadband satellite communication systems have attractive characteristics for supporting such services. However, many of the protocols designed primarily for terrestrial networks do not perform well over satellite networks. Therefore, it is necessary to look at the problem of reliable multicast in the solution space of satellite communications. Our protocol makes use of a special form of forward error correcting codes and couples it with an adaptive window based control mechanism to dynamically adjust the number of encoding packets forwarded to the users. Protocol makes very good use of the broadcast nature of the satellite channel and attempts to minimize the feedback from users. We evaluate the protocol performance by extensive computer simulations.},
	number = {Number: CSHCN TR 2003-17}
}
@techreport {
	title = {Detection and Classification of Network Intrusions using Hidden Markov Models},
	author = {Radosavac, Svetlana.},
	year = {2003},
	month = {01/2003},
	abstract = {This paper demonstrates that it is possible to model attacks witha low number of states and classify them using Hidden MarkovModels with very low False Alarm rate and very few FalseNegatives. We also show that the models developed can be used forboth detection and classification. We put emphasis on detectionand classification of network intrusions and attacks using HiddenMarkov Models and training on anomalous sequences. We test severalalgorithms, apply different rules for classification and evaluatethe relative performance of these. Several of the attack examplespresented exploit buffer overflow vulnerabilities, due toavailability of data for such attacks. We emphasize that thepurpose of our algorithms is not only the detection andclassification of buffer overflows; they are designed fordetecting and classifying a broad range of attacks.},
	number = {Number: CSHCN TR 2003-6}
}
@techreport {
	title = {Decentralized Control of Autonomous Vehicles},
	author = {Tan, Xiaobo., Hovareshti, Pedram.},
	year = {2003},
	month = {01/2003},
	abstract = {Decentralized control methods are appealing in coordination ofmultiple vehicles due to their low demand for long-range communication and their robustness to single-point failures. An important approach in decentralized multi-vehicle control involves artificial potentials or digital pheromones. In this paper we explore a decentralized approach to path generation for a group of combat vehicles in a battlefield scenario. The mission is to maneuver the vehicles to cover a target area. The vehicles are required to maintain good overall area coverage, and avoid obstacles and threats during the maneuvering. The gradient descent method is used, where each vehicle makes its moving decision by minimizing a potential function that encodes information about its neighbours, obstacles, threats and the target. We conduct analysis of vehicle behaviors by studying the vector field induced by the potential function. Simulation has shown that this approach leads to interesting emergent behaviors, and the behaviors can be varied by adjusting the weighting coefficientsof different potential function terms.},
	number = {Number: CSHCN TR 2003-8}
}
@techreport {
	title = {Jointly Optimal Quantization, Estimation, and Control of Hidden Markov Chains},
	author = {Tan, Xiaobo., Xi, Wei.},
	year = {2003},
	month = {01/2003},
	abstract = {It is of interest to understand the tradeoff between the communication resource comsumption and the achievable system performance in networked control systems. In this paper we explore a general framework for trade-off analysis and decision making in such systems by studying joint quantization,estimation, and control of a hidden Markov chain. We first formulate the joint quantization and estimation problem, where vector quantization with variable-block length is considered. Dynamic programming (DP) is used to find the optimal quantization scheme that minimizes a weighted combination of the estimation error, the communication cost, and the delay due to block coding. The DP equation issolved numerically and simulation shows that this approach is able to capture the tradeoffs among competing objectives by adjusting the cost weights. We then study the joint quantization and control problem. An example problem is solved analytically, which provides interesting insight into the approach. In both the joint quantization/estimation problem and the joint quantization/control problem, we show that the separation principle holds. The approaches to solving these two problemsshare the same spirit, and can be combined and extended to accomodate more objectives.},
	number = {Number: CSHCN TR 2003-9}
}
@techreport {
	title = {Multicast Routing in Mobile Ad Hoc Networks Using Source Grouped Flooding},
	author = {Chandrashekar, Karthikeyan.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we address the multicast routing problem for mobile ad hoc networks (MANETs). We present the Source Grouped Flooding approach to achieve multicast in MANETs. The protocol creates multiple multicast routes between the source and group members based on hop count distance constraints. We also propose a probabilistic data forwarding mechanism to achieve efficient data dissemination. The protocol aims to achieve the robustness of flooding and data distribution efficiency of tree based protocols. Simulation results verify performance.},
	number = {Number: CSHCN TR 2003-6}
}
@techreport {
	title = {A Feedback Implosion Suppression Algorithm for Satellite Reliable Multicast},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2003},
	month = {01/2003},
	abstract = {In this paper, we propose a knapsack-based feedback suppressionalgorithm for reliable multicast transport protocols operating over asatellite network. A reliable transport protocol needs to identify thepackets which failed to reach a given destination. This is achievedthrough feedback packets returned to the source. For multicastservices, receiver feedback has been shown to lead to thefeedback implosion problem. Feedback implosion is awell-studied problem and various solutions exist in the literature.However, these solutions mainly focus on wireline terrestrial networksand do not take into account the inherent characteristics of thesatellite channel and the architecture of the deployed network.Therefore, we need to revisit the problem and provide a new set ofsolutions for efficient integration to next generation satellitesystems. In this paper, we introduce a feedback implosion suppressionalgorithm, which effectively suppresses the amount of feedback relayedthrough the satellite channel, while ensuring that the criticalinformation is conveyed in a timely fashion. The performance of thealgorithm is evaluated through simulations.},
	number = {Number: CSHCN TR 2003-3}
}
@techreport {
	title = {Congestion management in access networks with long propagation delay},
	author = {Zhou, Xiaoming.},
	year = {2003},
	month = {01/2003},
	abstract = {Satellite networks are going to play an important role in the global information infrastructure. Satellites can be used to provide Internet services to fixed users and to mobile users. However, recent measurements show that the satellite link efficiency is only about 30\%. In order to improve the performance of Internet over satellite, a new protocol called Receiver Window Backpressure Protocol (RWBP) is proposed. RWBP uses per-flow queuing, round robin scheduling and receiver window backpressure for congestion management. Simulation results show that RWBP can maintain high utilization of the satellite link and improve fairness among the competing connections.},
	number = {Number: CSHCN TR 2003-23}
}
@techreport {
	title = {Dynamical Properties of TCP System with AQM Routers},
	author = {Chen, Huigang., Liu, Nelson X.},
	year = {2003},
	month = {01/2003},
	abstract = {In this report we discuss the dynamics of heterogeneous TCP systems with propagation delays. Instead of studying the local linearized TCP dynamics, we study the global stability conditions and obtain the stability regions. Also we provide proof of periodic behavior of a single TCP connection when stability conditions are not met.},
	number = {Number: CSHCN TR 2003-22}
}
@techreport {
	title = {Jitter Analysis of CBR Streams in Multimedia Networks},
	author = {Jou,  Jia-Shiang.},
	year = {2003},
	month = {01/2003},
	abstract = {The performance of real time applications such as video andvoice streams relies on packet delay jitter. Large delay jittercauses buffer overflow or underflow at the receiver end and theuser encounters interrupts. The delay jitter is mainly due to theperturbation of background traffic in the bottleneck router.Fulton and Li provide an analytical approximationfor the first-order and second-order statistics of delay jitter.However, their analysis is based on a Markovian model of thebackground traffic, which is not quite suitable for Internettraffic and requires lots of computational effort. We propose anefficient method to predict the jitter variance of a CBR(constant-bit rate) connection based on the wavelet model of thebackground traffic. The wavelet analysis extracts the statisticalproperties of background traffic and the analysis result can beused to predict an upper bound for the jitter variance of the CBRconnection.},
	number = {Number: CSHCN TR 2003-11}
}
@techreport {
	title = {On QoS Provisioning in ATM Networks},
	author = {Arora, Anubhav.},
	year = {2002},
	month = {01/2002},
	abstract = {A novel framework for QoS management is proposed in this paper to provide QoS guarantees to real-time connections.It comprises of in-service QoS monitoring mechanisms, a hierarchical scheduling algorithm based on dynamicpriorities that are adaptive to measurements, and methods to tune the schedulers at individual nodes based on the endto-end measurements.},
	number = {Number: CSHCN TR 2002-7}
}
@techreport {
	title = {A Multilevel ON/OFF Model for Multifractal Internet Traffic},
	author = {Jou,  Jia-Shiang.},
	year = {2002},
	month = {01/2002},
	abstract = {In this paper, an open-loop multilevel ON/OFF modelis proposed to capture the multifractal behavior of the HTTPtraffic on the Internet. It is assumed that the life time of aTCP session and the active time of a burst within a TCP session have a heavy-tail type distribution. The aggregatetraffic of this model is shown to be multifractal. We analyze itssecond and higher order statistics by the wavelet analysis anddevelop a simple method to estimate the model parameters from areal Internet trace. We show that real and synthesized trafficproduce the same Logscale Diagram with accuracy, for properselection of the model parameter. Finally, we compare using theNS-2 simulator the queueing behavior of FIFO queues fed by realand synthetic traffic demands.},
	number = {Number: CSHCN TR 2002-5}
}
@techreport {
	title = {Alternative Network Architectures for Supporting Communications from the International Space Station},
	author = {Nguyen, Alex T., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {In order to support the communications needs of the International Space Station (ISS), alternative communications architectures to provide broadband support need to be considered. We address three communications options and evaluate an architecture for the direct to ground option, which could serve as an intermediary solution to satisfy near term communications needs of commercial experiments and payloads on the ISS and overcome certain limitations of the current ISS communications infrastructure. We focus on a particular user\&rsquo;s requirements, and examine the system\&rsquo;s communications links, and coverage availability. These parameters, along with high-level cost estimates, are compared to using commercial relay satellites, and an enhanced TDRSS. The direct to ground option is viable for store-and-forward applications and cost comparable to commercial constellations, but TDRSS is the choice for real-time or continuous data applications.},
	number = {Number: CSHCN TR 2002-9}
}
@techreport {
	title = {TCP over Satellite Hybrid Networks: A Survey},
	author = {Zhou, Xiaoming.},
	year = {2002},
	month = {01/2002},
	abstract = {Satellite is going to play an important role in the global information infrastructure. Satellite canprovide direct to home Internet service (i.e. DirecPC from Hughes Network System) and it can alsoserve as traffic trunk in the middle of the network. About 98 percent of the Internet traffic is TCPtraffic. TCP works well in the terrestrial fiber network. However, in the satellite hybrid networks,because of the long propagation delay, large bandwidth-delay product, high bit error rate anddownstream/upstream bandwidth asymmetry, TCP performance degrades dramatically. This paperaddresses the problems of TCP in satellite data networks and reviews the proposed solutions in theliterature. For each solution, the advantages and disadvantages are pointed out. In addition,extensive simulations have been done for the proxy based scheme currently used in the industry tofind out how and to what extent the enhancements, such as connection splitting, window scalingand selective acknowledgement, benefit the TCP throughput.},
	number = {Number: CSHCN TR 2002-15}
}
@techreport {
	title = {IP Multicast via Satellite: A Survey},
	author = {Akkor, Gun., Hadjitheodosiou, Michael.},
	year = {2002},
	month = {01/2002},
	abstract = {Many of the emerging applications in the Internet, such astele-conferencing, distance-learning, distributed games, softwareupdates, and distributed computing would benefit from multicastservices. In many of these applications, there is a need todistribute information to many sites that are widely dispersed fromeach other. Communication satellites are a natural technology optionand are extremely well suited for carrying such services. Despite thepotential of satellite multicast, there exists little support forsatellite IP multicast services. Both Internet Engineering andInternet Research Task Forces (IETF and IRTF) have been involved in aresearch effort to identify the design space for a general purposereliable multicast protocol and standardize certain protocolcomponents as building blocks. However, for satellite multicastservices, several of these components have a different designspace. In this paper, we attempt to provide an overview of the designspace and the ways in which the network deployment and applicationrequirements affect the solution space. We maintain a similartaxonomy to that of the IETF efforts, and identify which keycomponents of a general multicast protocol are affected by two of themost common satellite network deployment scenarios. We also highlightsome of the issues which we think are critical in the development ofnext generation satellite IP multicast services.},
	number = {Number: CSHCN TR 2002-35}
}
@techreport {
	title = {Negotiating Access Control Policies Between Autonomous Domains},
	author = {Bharadwaj, Vijay G.},
	year = {2002},
	month = {01/2002},
	abstract = {Autonomous policy domains often need to share resources to accomplish a common task. To do this they must negotiate a common access control policy to the shared resources. We use mathematical techniques from game theory to show that the outcome of such negotiations can often be predicted from the distribution of power among the participants, independent of the actual mechanics of negotiation. We discuss the axiomatic derivation of some game theoretic solution concepts, and illustrate our techniques with examples.},
	number = {Number: CSHCN TR 2002-3}
}
@techreport {
	title = {INORA- A Unified Signaling and Routing Protocol in Mobile AdHoc networks},
	author = {Dharmaraju, Dinesh., Roy-Chowdhury, Ayan., Hovareshti, Pedram.},
	year = {2002},
	month = {01/2002},
	abstract = {Mobile Ad hoc NETworks(MANET) are characterized by bandwidthconstrained wireless links, multiple hops and highly dynamic topologies.Providing QoS support in MANETs is hence a challenging task. Thispaper presents the design, implementation and evaluation of INORA,which is a network layer QoS support mechanism that makes use of theINSIGNIA in-band signaling mechanism and TORA routing protocol forMANETs. TORA provides multiple routes between a given source and destination.},
	number = {Number: CSHCN TR 2002-18}
}
@techreport {
	title = {Flow Control at Satellite Gateways},
	author = {Zhou, Xiaoming., Liu, Xicheng.},
	year = {2002},
	month = {01/2002},
	abstract = {In this paper we analyze the problems that cause this dramatically degradedperformance. Based on the observation that it difficult for an end-to-end solution to solve these problems in this kind of hybrid networks, we propose a connection splitting based solution. A rate-based protocol is designed for the satellite connections and a flow control scheme at the satellite gateways (SGW) used to couple the two split connections together.},
	number = {Number: CSHCN TR 2002-19}
}
@techreport {
	title = {A Dynamic Optimization Approach to the Scheduling Problem in Satellite and Wireless Broadcast Systems},
	author = {Raissi-Dekhordi, Majid.},
	year = {2002},
	month = {01/2002},
	abstract = {The continuous growth in the demand for access to information andthe increasing number of users of the information delivery systemshave sparked the need for highly scalable systems with moreefficient usage of the bandwidth. One of the effective methods forefficient use of the bandwidth is to provide the information to agroup of users simultaneously via broadcast delivery. Generally,all applications that deliver the popular data packages (trafficinformation, weather, stocks, web pages) are suitable candidatesfor broadcast delivery and satellite or wireless networks withtheir inherent broadcast capability are the natural choices forimplementing such applications.In this report, we investigate one of the most important problemsin broadcast delivery i.e., the broadcast scheduling problem. Thisproblem arises in broadcast systems with a large number of datapackages and limited broadcast channels and the goal is to findthe best sequence of broadcasts in order to minimize the average waiting time of the users.We first formulate the problem as a dynamic optimization problemand investigate the properties of the optimal solution. Later, weuse the bandit problem formulation to address a version of theproblem where all packages have equal lengths. We find anasymptotically optimal index policy for that problem and comparethe results with some well-known heuristic methods.},
	number = {Number: CSHCN TR 2002-34}
}
@techreport {
	title = {Scalable and Efficient Key Agreement Protocols for Secure Multicast Communication in MANETs},
	author = {Striki, Maria.},
	year = {2002},
	month = {01/2002},
	abstract = {In this paper protocols for group key distribution are compared and evaluated from the point of view of Mobile Ad Hoc Networks (MANETs). A MANET is a collection of wireless mobile nodes, communicating among themselves over possibly multihop paths, without the help of any infrastructure such as base stations or access points. So the need to render those networks as autonomous and secure as possible, since no central authorization can be assumed at all times, becomes emergent. Key management is the service that ensures the security of communication among nodes, and the capability of their cooperation as a secure group. It consists of three important services: key generation, user authentication and key distribution. In this work we assume that the participating users have already been authenticated with some mechanism, and we are focused only on studying and comparing protocols for group key establishment in MANETs. We distinguish the protocols in two families, the contributory and non-contributory and we evaluate them from the point of view of MANETs.},
	number = {Number: CSHCN TR 2002-28}
}
@techreport {
	title = {TCP Performance in Wireless Systems with Opportunistic Scheduling},
	author = {Srinivasan, Roshni.},
	year = {2002},
	month = {01/2002},
	abstract = {We use extensive simulations to expose the linkage between scheduling atthe medium access (MAC) layer and TCP performance. The results in thispaper underscore the need for careful design of opportunistic schedulingmechanisms in order to ensure that gains in MAC layer are also realized by TCP.},
	number = {Number: CSHCN TR 2002-22}
}
@techreport {
	title = {On System Designs of Distributed, Extensible Framework for Network Monitoring and Control},
	author = {Li, Hongjun., Yang, Shahan.},
	year = {2001},
	month = {01/2001},
	abstract = {In this paper, we present a distributed, extensible framework for supporting adaptive, dynamic network monitoring and control. We borrow the paradigm of management by delegation [8] and distribute some processing intelligence to network elements. The functionality of the delegated agents, and even that of the native software processes, could be extended dynamically without recompilation. Such procedure is called change of logic and we explain it in the framework of communicating finite state machines for extending native process functionality. We use Java technology and C/C++ dynamic linkage mechanism to achieve the standard hosting infrastructure for these agents and our system designs span a wide scope of applications.},
	number = {Number: CSHCN TR 2001-12}
}
@techreport {
	title = {A New Adaptive Aggregation Algorithm for Infinite Horizon Dynamic Programming},
	author = {Zhang, Chang.},
	year = {2001},
	month = {01/2001},
	abstract = {Dynamic programming suffers the "curse of dimensionality" when it isemployed for complex control systems. State aggregation is used to solvethe problem and acceleratecomputation by looking for a sub-optimal policy. In this paper, a new method, which converges much faster thanconventional aggregated value iteration based on TD(0), is proposed for computing the valuefunctions of theaggregated system. Preliminary results show that the new method increases thespeed of convergence impressively. Aggregation introduces errorsinevitably. An adaptive aggregation scheme employing the newcomputation method isalso proposed to reduce the aggregation errors.},
	number = {Number: CSHCN TR 2001-5}
}
@techreport {
	title = {Performance Evaluation of Run-to-Run Control Methods in Semiconductor Processes},
	author = {Zhang, Chang.},
	year = {2001},
	month = {01/2001},
	abstract = {Run-to-Run (RtR) control plays an important role in semiconductormanufacturing processes. In this paper, RtR control methods are classified and evaluated. The set-valued RtR controllers with ellipsoid approximation are compared with two typical RtR controllers: the Exponentially Weighted Moving Average (EWMA) controller and the Optimizing Adaptive Quality Controller (OAQC) by simulations according to the following criteria: A good RtR controller should be able to compensate for various disturbances, such as small drifts, step disturbances and model errors; moreover, it should be able to deal with bounds, cost requirement and multipletargets that are often encountered in semiconductor processes. Based on our simulation results, suggestions on selection of a proper RtR controller for a semiconductor process are given as conclusions.},
	number = {Number: CSHCN TR 2001-20}
}
@techreport {
	title = {A Framework for Supporting Intelligent Fault and Performance Management for Communication Networks},
	author = {Li, Hongjun.},
	year = {2001},
	month = {01/2001},
	abstract = {For the first question, we define the notion of right diagnosis via the introduction of intervention networks. For the second question, we formulate the decision making procedure using the framework of partially observable Markov decision processes. A heuristic dynamic strategy is proposed to solve this problem and the effectiveness is shown via simulation.},
	number = {Number: CSHCN TR 2001-13}
}
@techreport {
	title = {A Decision-Process Analysis of Implicit Coscheduling},
	author = {Poovendran, Radha., Keleher, P. },
	year = {2000},
	month = {01/2000},
	abstract = {This paper presents a theoretical framework based on Bayesian decision theory for analyzing recently reported results on implicit coscheduling of parallel applications on clusters of workstations. Using probabilistic modeling, we show that the approach presented can be applied for processes with arbitrary communication mixes. We also note that our approach can be used for deciding the additional spin times in the case of spin-yield.Finally, we present arguments for the use of a different notion of fairness than assumed by prior work.},
	number = {Number: CSHCN TR 2000-12}
}
@techreport {
	title = {Fair Bandwidth Allocation and Buffer Management in Hybrid Network Gateways},
	author = {Srinivasan, Roshni., Vaidyanathan, Ravichander.},
	year = {2000},
	month = {01/2000},
	abstract = {In supportof each of these contributions, we report on extensive simulationresults. Our scheme outperforms other resource allocation schemesreported in the literature and in particular, demonstrates significantimprovements in fairness to long RTT connections in the hybrid networkframework.},
	number = {Number: CSHCN TR 2000-11}
}
@techreport {
	title = {A Hierarchical Structure For Finite Horizon Dynamic Programming Problems},
	author = {Zhang, Chang.},
	year = {2000},
	month = {01/2000},
	abstract = {In this paper, we propose a hierarchical structure to solve finite horizon stochastic shortest pathproblems in parallel. In general, the approach reducesthe time complexity of the original problem to a logarithm level, which hassignificant practical meaning.},
	number = {Number: CSHCN TR 2000-19}
}
@techreport {
	title = {On the True Cramer-Rao Lower Bound for the DA Joint Estimation of Carrier Phase and Timing Offsets},
	author = {Jiang, Yimin., Sun, Feng-Wen.},
	year = {2000},
	month = {01/2000},
	abstract = {In this manuscript, we derive a closed-form formula for data-aided CRB fortiming and phase synchronization with respect to arbitrary training sequence. The bound illustrates the close relation between the training sequence and the fundamental limit on timing and phase synchronization. This bound provides additional insights on the sequence design.},
	number = {Number: CSHCN TR 2000-14}
}
@techreport {
	title = {Intelligent Distributed Fault Management for Communication Networks},
	author = {Li, Hongjun.},
	year = {2000},
	month = {01/2000},
	abstract = {In this paper, we present an intelligent, distributed fault management system for communication networks using belief networks as fault model and inference engine. The managed network is divided into domains and for each domain, there is an intelligent agent called Domain Diagnostic Agent attached to it, which is responsible for this domain{\textquoteright}s fault management. Belief network models are embedded in such an agent and under symptoms observation, the posterior probabilities of each candidate fault node being faulty is computed. We define the notion of right diagnosis, describe the diagnosis process based on this concept, and present a strategy for generation of test sequence.},
	number = {Number: CSHCN TR 2000-15}
}
@techreport {
	title = {Hierarchical Modeling for Network Performance Evaluation},
	author = {Liu, Mingyan.},
	year = {2000},
	month = {01/2000},
	abstract = {As networks grow in size, nodes tendto form clusters geographically and hierarchical routing schemes are morecommonly used, and it is important that network modeling methods havescale-up capabilities. Loss networks and reduced load/fixed point modelsare often used toapproximate call blocking probabilities and hence throughput in a circuitswitched network. We use the same idea for estimating connection blockingin a data network with certain QoS routing schemes. However so far most workbeing done in this area is for flat networks with flat routing schemes.},
	number = {Number: CSHCN TR 2000-8}
}
@techreport {
	title = {Maximum Likelihood Slow Frequency-Selective Fading Channel Estimation Using Frequency Domain Approach},
	author = {Jiang, Yimin.},
	year = {2000},
	month = {01/2000},
	abstract = {Traditional works assumed symbol period spaced delay-tapped line model and additive white Gaussian noise (AWGN). Because of pre-filtering in the receiver front end, if the sampling rate is larger than one sample per symbol or sampling epoch is unknown (i.e., timing information is not available), AWGN model is not valid anymore.},
	number = {Number: CSHCN TR 2000-13}
}
@techreport {
	title = {Reliable Multicasting via Satellite: Delay Considerations},
	author = {Payne, Stephen Marshall.},
	year = {2000},
	month = {01/2000},
	abstract = {Many different reliable multicast protocols have been proposed and analyzed in the current literature. Since satellites are naturallya braodcast medium, multicast communications have the potential togreatly benefit from their wide-scale deployment. The performance ofreliable multicast protocols needs to be studied and become betterunderstood over networks including satellite links. Most of the analysisperformed on these protocols has dealt with bandwidth usage, bufferrequirements, and processing delay. Very few studies address thetransmission delay incurred from using reliable multicast protocols. Hybriderror control protocols have been studied in terms of bandwidth and delay.The effects of different estimation schemes coupled with autoparityusage are investigated and results are compared. Simple adaptive mechanismsused with a local recovery scheme are found to offer the best overallresults in terms of reducing recovery latency and satellite bandwidth usage.},
	number = {Number: CSHCN TR 2000-10}
}
@techreport {
	title = {Hierarchical Loss Network Model for Performance Evaluation},
	author = {Liu, Mingyan.},
	year = {2000},
	month = {01/2000},
	abstract = {As networks grow in size, nodes tendto form clusters geographically and hierarchical routing schemes are morecommonly used. Loss network and reduced load models are often used toapproximate end-to-endcall blocking probabilities, and hence, throughput. However so far all workbeing done in this area is for flat networks with flat routing schemes.},
	number = {Number: CSHCN TR 2000-1}
}
@techreport {
	title = {Ship RCS Scintillation Simulation},
	author = {Baras, John S.},
	year = {1978},
	month = {01/1978}
}
