@conference {
	title = {Effects of Topology in Networked Systems: Stochastic Methods and Small Worlds},
	author = {Baras, John S., Hovareshti, Pedram.},
	year = {2008},
	month = {12/2008},
	abstract = {The topology of a networked control system has critical consequences for its performance. We provide first substantial examples on the effects of topology. Then we proceed to develop a rigorous evaluation of topology effects using stochastic methods inspired from statistical physics and Markov chains. This analysis leads us to proofs on faster convergence of distributed algorithms in networked systems for certain topologies and especially small-world topologies, which are~given an {\textquoteleft}efficiency{\textquoteright} characterization. Finally, these results lead to the development of self-organization of such systems in hierarchies that provably improve performance and response.},
	address = {Cancun, Mexico},
	booktitle = {47th IEEE Conference on Decision and Control},
	pages = {pp. 2973-2978}
}
@conference {
	title = {Average Consensus over Small World Networks: A Probabilistic Framework},
	author = {Hovareshti, Pedram., Baras, John S., Gupta, Vijay.},
	year = {2008},
	month = {12/2008},
	abstract = {It has been observed that adding a few long range edges to certain graph topologies can significantly increase the rate of convergence for consensus algorithms. A notable example is the class of ring-structured Watts-Strogatz small world graphs. Building on probabilistic methods for analyzing {\textquoteleft}small-world phenomena{\textquoteright}, developed in our earlier work, we provide here a probabilistic framework for analyzing this effect. We investigate what graph characteristics lead to such a significant improvement and develop bounds to analyze consensus problems on randomly varying graphs.},
	address = {Cancun, Mexico},
	booktitle = {47th IEEE Conference on Decision and Control},
	pages = {pp. 375-380}
}
@conference {
	title = {Almost Sure Convergence to Consensus in Markovian Random Graphs},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {12/2008},
	abstract = {In this paper, we discuss the consensus problem for a network of dynamic agents with undirected information flow and random switching topologies. The switching is determined by a Markov chain, each topology corresponding to a state of the Markov chain. We show that in order to achieve consensus almost surely and from any initial state the sets of graphs corresponding to the closed positive recurrent sets of the Markov chain must be jointly connected. The analysis relies on tools from matrix theory, Markovian jump linear systems theory and random processes theory. The distinctive feature of this work is addressing the consensus problem with {\textquotedblleft}Markovian switching{\textquotedblright} topologies.},
	address = {Cancun, Mexico},
	booktitle = {47th IEEE Conference on Decision and Control},
	pages = {pp. 3535-3540}
}
@conference {
	title = {Power Allocation Tradeoffs in Multicarrier Authentication Systems},
	author = {Yu, Paul L., Baras, John S., Sadler, Brian M.},
	year = {2008},
	month = {12/2008},
	abstract = {Physical layer authentication techniques exploit signal characteristics to identify radios. We describe how multicarrier systems may use such techniques to stealthily authenticate while maintaining high levels of security and robustness. We show that with channel state information (CSI) at the transmitter and receiver, multicarrier authentication systems can further improve performance by carefully allocating the authentication power on each carrier.},
	address = {Orlando, FL},
	booktitle = {26th Army Science Conference},
	pages = {pp.1-5}
}
@conference {
	title = {A Lightweight Certificate-based Source Authentication Protocol for Group Communications in Hybrid Wireless/Satellite Networks},
	author = {Roy-Chowdhury, Ayan., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {In this paper, we describe an efficient authentication protocol for group communication in hybrid wireless networks with a satellite overlay. The proposed protocol uses a new class of lightweight, symmetric-key certificates called TESLA certificate. The certificates bind the identities of the senders to the anchor elements of their key chains; messages from the senders are authenticated by MACs computed with keys from the chain. The satellite is used as the Certificate Authority to generate the certificates. The satellite also acts as the proxy for the senders in disclosing the MAC keys to the receivers in the network. Due to the use of symmetric MAC functions, the proposed protocol is much less expensive in terms of node processing power and energy compared to digital signatures. The use of the satellite as the CA and the proxy allows strong security mechanisms and fast message verification. Through analysis, we show that the protocol is secure against malicious adversaries. We also estimate of the performance of the protocol in comparison to public key-based digital signatures.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-6}
}
@conference {
	title = {Aerial Platform Placement Algorithm to Satisfy Connectivity and Capacity Constraints in Wireless Ad-hoc Networks},
	author = {Perumal, Senni., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {In this paper, we address the problem of establishing full connectivity and satisfying required traffic capacity between disconnected clusters in large wireless ad-hoc ground networks by placing a minimum number of advantaged high flying Aerial Platforms (APs) as relay nodes at appropriate places. We formulate the problem of providing both connectivity and required capacity between disconnected ground clusters as a constrained clustering problem with complexity costs. The basic requirement for connectivity between the ground clusters and APs is converted into a summation form distortion function. The additional requirement for connectivity between the various APs is encoded by adding a new (summation form) constraint to the distortion function. In order to satisfy the required capacity out of each cluster to all other clusters, we add a cost function that depends on the assignment probabilities of the APs and relate~the source (prior) probabilities of each cluster to the required capacity out of this cluster. The cost function produces solutions which are load balanced, i.e., the capacities supported through each AP are nearly equal. We solve the resultant clustering problem using Deterministic Annealing in order to find (near) globally optimal solutions for the minimum number and locations of the APs to establish full connectivity and provide required traffic capacity between disconnected clusters. We establish the validity of our algorithm by comparing it with optimal exhaustive search algorithms and show that our algorithm is near-optimal for the problem of establishing connectivity and satisfying capacity requirements between disconnected clusters.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {Performance Metric Sensitivity Computation for Optimization and Trade-off Analysis in Wireless Networks},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas.},
	year = {2008},
	month = {11/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics for multihop wireless networks, including MANETs. We introduce an approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model takes into account effects of the hidden nodes, scheduling algorithms, IEEE 802.11 MAC and PHY layer transmission failures and finite packet transmission retries at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models, and develop a methodology for sensitivity analysis, parameter optimization and trade-off analysis for key wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {Trust Credential Distribution in Autonomic Networks},
	author = {Jiang, Tao., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {Autonomic networks are networks that are self-organized, and controlled and managed in a decentralized way. Peers/nodes in such networks rely on co-operation of each other. Thus, accurate trust establishment and maintenance is essential for secure and reliable operations in autonomic networks. Trust management in autonomic networks is a much more challenging problem than in traditional server-based networks. In traditional networks, centralized trusted servers provide necessary trust credentials for trust establishment. However, such servers are not available in autonomic networks, where trust credentials are distributed among users in the network. In this paper, we design a distributed scheme for efficiently distributing trust credentials, which requires no global information exchanges. Our scheme is inspired from network coding, where trust credentials are combined by the intermediate nodes during distribution.},
	address = {New Orleans, LA},
	booktitle = {IEEE Global Communications Conference (IEEE Globecom 2008)},
	pages = {pp. 1-5}
}
@conference {
	title = {Intrusion Detection of In-Band Wormholes in MANETS Using Advanced Statistical Methods},
	author = {Zheng, Shanshan., Jiang, Tao., Baras, John S.},
	year = {2008},
	month = {11/2008},
	abstract = {Due to the dynamics and mobility of mobile ad hoc networks (MANETs), intrusion detection techniques in MANETs must be adaptive. In this work, we propose detection schemes that are suitable to detect in-band wormhole attacks. The first detection scheme uses the Sequential Probability Ratio Test (SPRT). The SPRT has been proven to be an optimal detection test when the probability distributions of both normal and abnormal behaviors are given. Furthermore, we introduce non-parametric methods, which require no training and are more adaptive to mobile scenarios. The proposed detection schemes are implemented and evaluated using a 48-node testbed and a mobile ad-hoc network emulator at the Army Research Lab. The performance and the~detection accuracy of various schemes are compared, especially in the presence of congestion. We provide a quantitative analysis of tradeoffs among detection latency and probabilities of false alarms and missed detection.},
	address = {San Diego, CA},
	booktitle = {Milcom: 08 Assuring Mission Success},
	pages = {pp. 1-7}
}
@conference {
	title = {Loss Network Models and Multiple Metric Performance Sensitivity Analysis for Mobile Wireless Multi-Hop Networks},
	author = {Baras, John S., Perumal, Senni., Tabatabaee, Vahid., Somasundaram, Kiran K., Purkayastha, Punyaslok.},
	year = {2008},
	month = {11/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics of mobile wireless multi-hop networks, including MANETs. The method utilizes approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model considers effects of the hidden nodes, node scheduling algorithms, MAC and PHY layer failures and unsuccessful packet transmission attempts at the MAC layer in~arbitrary time-varying network topologies where multiple paths share nodes. The method then applies Automatic Di{\textregistered}erentiation (AD) to these implicit performance models, to compute sensitivities of various performance metrics with respect to net- work parameters. We demonstrate the method by applying it to time-varying mobile network topologies, including reduced connectivity instances, with both random access MAC (contention mode of the 802.11) as well as reservation-based MAC (USAP TDMA based protocol). We analyze throughput, delay and packet loss as metrics and investigate metric optimization and tradeoff analysis. Finally, we provide numerical results for realistic mobile networks with time-varying topologies.},
	address = {Maui, Hawaii},
	booktitle = {Fourth International Wireless Internet Conference (WICON 2008)}
}
@conference {
	title = {Aerial Platform Placement Algorithms to Satisfy Connectivity, Capacity and Survivability Constraints in Wireless Ad-hoc Networks},
	author = {Perumal, Senni., Baras, John S., Graff, Charles J., Yee, David G.},
	year = {2008},
	month = {11/2008},
	abstract = {In this paper, we address the problem of establishing full connectivity and satisfying required traffic capacity between disconnected clusters in large wireless ad-hoc ground networks by placing a minimum number of advantaged high flying Aerial Platforms (APs) as relay nodes at appropriate places. We also extend the connectivity solution in order to make the network survivable to a single AP failure. The problem of providing both connectivity and required capacity between disconnected ground clusters is formulated as a summation-form clustering problem with inter-AP distance constraints that make the AP network fully connected and with complexity costs that take care of cluster to AP capacity constraints. The resultant clustering problem is solved using Deterministic Annealing to find (near) globally optimal solutions for the minimum number and locations of the APs to establish full connectivity and provide required traffic capacity between disconnected clusters. In order to make the network single AP survivable, the connectivity solution is extended so that each AP connects to at least two neighboring APs and each ground cluster connects to at least two APs. We establish the validity of our algorithms by comparing it with optimal exhaustive search algorithms and show that our algorithms are near-optimal for the problem of establishing connectivity between disconnected clusters.},
	address = {San Diego, CA},
	booktitle = {Milcom: 08 Assuring Mission Success},
	pages = {pp. 1-7}
}
@conference {
	title = {Constrained Coalitional Games and Networks for Autonomous Agents},
	author = {Baras, John S.},
	year = {2008},
	month = {10/2008},
	address = {Athens, Greece},
	booktitle = {Inter-Perf 2008: Workshop on Interdisciplinary Systems Approach in Performance Evaluation and Design of Computer \& Communication Systems}
}
@conference {
	title = {Performance Evaluation and Trade-Offs of Optimal Back-Off Misbehavior Detection Schemes in Wireless Networks in the Presence of Interference},
	author = {Radosavac, Svetlana., Baras, John S.},
	year = {2008},
	month = {10/2008},
	abstract = {In this work, we evaluate the impact of interference caused by concurrent transmissions of neighboring stations on the performance of quickest detection schemes for detection of back-off misbehavior in the IEEE 802.11 MAC. We evaluate the trade-offs that both the adversary and the detector face under such conditions using a game theoretic framework. Furthermore, we evaluate the worst-case scenarios under which the given detector can efficiently operate under the predetermined conditions and show by both mathematical analysis and simulation how the presence of uncertainty affects the performance of the detector. Finally, we conclude that in the presence of (i) adaptive intelligent adversaries and (ii) variable environment conditions, the adoption of a static detection system is not advisable and propose employment of an adaptive detection system in order to maintain satisfying performance under a wide range of conditions.},
	address = {Athens, Greece},
	booktitle = {Valuetools 2008},
	pages = {pp. 1-10}
}
@conference {
	title = {Performance Modeling of Hybrid Satellite/Wireless Networks Using Fixed Point Approximation and Sensitivity Analysis of the Performance Models for Network Design},
	author = {Roy-Chowdhury, Ayan., Tabatabaee, Vahid., Baras, John S.},
	year = {2008},
	month = {09/2008},
	abstract = {In this work, we propose a new analytical method for modeling and estimating the performance of hybrid networks that are comprised of terrestrial wireless networks interconnected by a satellite overlay. We take advantage of the natural hierarchy present in the hybrid architecture to split the network into multiple levels based on the node and link characteristics. For the lower level of terrestrial wireless nodes, we use a simple approximate (throughput) loss model that couples the physical, MAC and routing layers. The model provides quantitative statistical relations between the loss parameters used to characterize multiuser interference and physical path conditions on the one hand and traffic rates between origin-destination pairs on the other. For the higher layer consisting of the terrestrial gateway nodes interconnected by the satellite overlay, we use a simple satellite channel bit error loss model coupled with a channel access protocol, to derive a similar relationship between traffic arrival rate and the link loss. We use the technique of hierarchical~reduced loss network model, adapted for packet-switched networks, to create a reduced load network model for the hybrid network that connects the packet arrival rates in the different levels with the associated physical and link loss rates. We then apply a fixed point approximation approach for this set of relations to derive a solution that converges to a fixed point for the given set of parameters, while satisfying all the equations in the set. The result is an implicit model of the selected performance metric parameterized by the design variables. We apply the technique of Automatic Differentiation to the performance models obtained through the fixed point approximation and analyze the sensitivity of the performance metrics to variations in the selected network parameter. We thus develop a methodology for parameter optimization and sensitivity analysis of protocols to aid in the design of hybrid networks. We demonstrate the effectiveness of our approach through simulation results, compared with results from discrete event simulations on identical network topology.},
	address = {Matera, Italy},
	booktitle = {Ka and Broadband Communications Conference},
	pages = {pp. 245-253}
}
@conference {
	title = {Dynamic Network Security Deployment Under Partial Information},
	author = {Theodorakopoulos, George., Baras, John S., Le Boudec, Jean-Yves.},
	year = {2008},
	month = {09/2008},
	abstract = {A network user{\textquoteright}s decision to start and continue using security products is based on economic considerations. The cost of a security compromise (e.g., worm infection) is compared against the cost of deploying and maintaining a sufficient level of security. These costs are not necessarily the real ones, but rather the perceived costs, which depend on the amount of information available to a user at each time. Moreover, the costs (whether real or perceived) depend on the decisions of other users, too: The probability of a user getting infected depends on the security deployed by all the other users. In this paper, we combine an epidemic model for malware propagation in a network with a game theoretic model of the users{\textquoteright} decisions to deploy security or not. Users can dynamically change their decision in order to maximize their currently perceived utility. We study the equilibrium points~and their dependence on the speed of the learning process through which the users learn the state of the network. We find that the faster the learning process, the higher the total network cost.},
	address = {Monticello, IL},
	booktitle = {Forty-Sixth Annual Conference on Communication, Control and Computing},
	pages = {pp. 261-267}
}
@conference {
	title = {Multi-hop Mobile Wireless Network Design: Implicit Cross-layer Loss Models and Performance Sensitivities},
	author = {Baras, John S.},
	year = {2008},
	month = {09/2008},
	address = {San Francisco, CA},
	booktitle = {MobiCom 2008}
}
@conference {
	title = {Trust in Social, Economic, Communication and Web-based Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {08/2008},
	address = {Samos, Greece},
	booktitle = {12th Pan-Hellenic Conference on Informatics (PCI2008)}
}
@conference {
	title = {Constrained Coalitional Games and Networks of Autonomous Agents},
	author = {Baras, John S.},
	year = {2008},
	month = {08/2008},
	address = {Lund, Sweden},
	organization = {Department of Automatic Control, Lund University}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {08/2008},
	address = {Athens, Greece},
	organization = {National Technical University of Athens}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {07/2008},
	address = {Chania, Crete},
	organization = {Technical University of Crete}
}
@conference {
	title = {Physical Layer Authentication},
	author = {Baras, John S.},
	year = {2008},
	month = {07/2008},
	address = {Herakleion, Greece},
	organization = {University of Crete, Department of Electrical Engineering and FORTH Institute for Computer Science}
}
@conference {
	title = {Dynamic Trust, Reputation and Recommender Systems for Web-based Social Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {07/2008},
	address = {Patras, Greece},
	booktitle = {18th European Conference on Artificial Intelligence (ECAI{\textquoteright}08)},
	organization = {University of Patras}
}
@conference {
	title = {Optimal Linear Quadratic Regulator for Markovian Jump Linear Systems, in the Presence of One Stop-Time Step Delayed Mode Observations},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {07/2008},
	abstract = {In this paper, we provide the solution to the optimal Linear Quadratic Regulator (LQR) paradigm for Markovian Jump linear Systems, when the continuous state is available at the controller instantaneously, but the mode is available only after a delay of one-time step. This paper is the first to investigate the LQR paradigm in the presence of such mismatch between the delay in observing the mode and the continuous state at the controller. We show that the optimal LQR policy is a time-varying matrix gain multiplied by the continuous component of the state, where the gain is indexed in time by the one-step delayed mode. The solution to the LQR is expressed as a collection of coupled Riccati iterations and equations, for the finite and the infinite horizon cases respectively. In the infinite horizon case, the solution of the coupled Riccati equations or a certificate of infeasibility is obtained by solving a set of linear matrix inequalities. We also explain the difficulties of solving the LQR problem when the mode is observed by the controller with a delay of more than one step. We show that, with delays of more than one time-step, the optimal control will be a time-varying nonlinear function of the continuous state and of the control input, without presenting an exact solution.},
	address = {Seoul, Korea},
	booktitle = {17th IFAC World Congress},
	pages = {pp. 8056-8061}
}
@conference {
	title = {Main Issues in Defining and Maintaining Trust: Vision for the Future},
	author = {Baras, John S.},
	year = {2008},
	month = {06/2008},
	address = {Berlin, Germany},
	booktitle = {Future of Trust in Computing Conference}
}
@conference {
	title = {A Policy-Based Routing Scheme for Multi-Robot Systems},
	author = {Purkayastha, Punyaslok., Hovareshti, Pedram., Baras, John S.},
	year = {2008},
	month = {06/2008},
	abstract = {In this paper, we consider a policy-based routing scheme for a wireless communication network consisting of a set of robots as nodes. Our scheme provides a communication infrastructure that enables the multi-robot system to accomplish its assigned tasks. Our scheme is adaptive and can be implemented in a distributed manner by the nodes of the network. The scheme makes estimates of link and path costs in the network and uses these estimates to construct probabilistic routing tables in the nodes. We use ideas from the literature on simulation methods for approximate dynamic programming to compute, in a distributed manner, the cost estimates.We propose two schemes that update the probabilistic routing tables at the nodes of the network. One of the schemes is an adaptation of the Linear Reward Inaction rule found in studies of stochastic learning automata. Our other scheme is a modification of an Ant-Based Routing algorithm. We assume a simple model of the link behavior in the wireless network - a message transmission on a wireless link is assumed to be successful with a certain probability and is lost otherwise. We also analyze our algorithms and show that our probabilistic update schemes direct packets along paths with low costs.},
	address = {Ajaccio, France},
	booktitle = {16th Mediterranean Conference on Control and Automation},
	pages = {pp. 970-975}
}
@conference {
	title = {Multicarrier Authentication at the Physical Layer},
	author = {Yu, Paul L., Baras, John S., Sadler, Brian M.},
	year = {2008},
	month = {06/2008},
	abstract = {Authentication is the process where claims of identity are verified. Though authentication mechanisms typically exist above the physical layer, physical layer methods have recently been introduced that do not require extra bandwidth. In this paper, we propose a multi-carrier extension to the work and consider the stealth and robustness tradeoffs. We conclude by discussing the power-reliability tradeoff and the applicability to cross-layer security.},
	address = {Newport Beach, CA},
	booktitle = {IEEE Workshop on Security and Privacy in Wireless Networks (IEEE SPAWN 2008)},
	pages = {pp. 1-6}
}
@conference {
	title = {Optimal State Estimation for Discrete-Time Markovian Jump Linear Systems, in the Presence of Delayed Mode Observations},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {06/2008},
	abstract = {In this paper, we investigate an optimal state estimation problem for Markovian Jump Linear Systems. We consider that the state has two components: the first component of the state is finite-valued and is denoted as mode, while the second (continuous) component is in a finite dimensional Euclidean space. The continuous state is driven by a deterministic control input and a zero mean, white and Gaussian process noise. The observable output has two components: the first is the mode delayed by a fixed amount and the second is a linear combination of the continuous state observed in zero mean white Gaussian noise. Our paradigm is to design optimal estimators for the current state, given the current output observation. We provide a solution to this paradigm by giving a recursive estimator of the continuous state, in the minimum mean square sense, and a finitely parameterized recursive scheme for computing the probability mass function of the current mode conditional on the observed output. We show that the optimal estimator is nonlinear on the observed output and on the control input. In addition, we show that the computation complexity of our recursive schemes is an exponential function of the mode observation delay.},
	address = {Seattle, Washington},
	booktitle = {2008 Automatic Control Conference},
	pages = {pp.  3560-3565}
}
@conference {
	title = {Wireless Network Design: Implicit Loss Models, PHY Feedback, Performance Sensitivities},
	author = {Baras, John S.},
	year = {2008},
	month = {05/2008},
	address = {Los Angeles, California},
	booktitle = {USC Workshop on Wireless Networks}
}
@conference {
	title = {Optimal State Estimation for Discrete-Time Markovian Jump Linear Systems, in the Presence of Delayed Output Observations},
	author = {Matei, Ion., Martins, Nuno C., Baras, John S.},
	year = {2008},
	month = {05/2008},
	abstract = {In this paper, we investigate the design of optimal state estimators for Markovian Jump Linear Systems. We consider that the state has two components: the first component is finite-valued and is denoted as mode, while the second (continuous) component is in a finite dimensional Euclidean space. The continuous state is driven by a zero mean, white and Gaussian process noise. The observation output has two components: the first is the mode and the second is a linear combination of the continuous state observed and zero mean white Gaussian noise. Both output components are affected by delays, not necessarily equal. Our paradigm is to design optimal estimators for the current state, given the current output observation. We provide a solution to this paradigm by giving a recursive estimator for the continuous state, in the minimum mean square sense, and a finitely parameterized recursive scheme for computing the probability mass function of the current mode conditioned on the observed output. We show that when the mode is observed with a greater delay than the continuous output component, the optimal estimator nonlinear in the observed outputs.},
	address = {Porto, Portugal},
	booktitle = {IEEE Information Theory Workshop (ITW 2008)},
	pages = {pp. 237-242}
}
@conference {
	title = {Wireless Network and Network Protocol Design: A Components and Optimization Based Approach},
	author = {Baras, John S.},
	year = {2008},
	month = {04/2008},
	organization = {DoCoMo Labs USA}
}
@conference {
	title = {Fault-Tolerant Extension of Hypercube for Secure and Reliable Group Communications},
	author = {Striki, Maria., Baras, John S., Manousakis, Kyriakos.},
	year = {2008},
	month = {04/2008},
	abstract = {Securing group communications in resource constrained, infrastructure-less Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless networking and security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security, on the other hand, is becoming an indispensable requirement of our modern life for all these applications. The inherent limitations of MANETs impose major difficulties on establishing a suitable secure group communications framework. We contribute to the latter by extending Hypercube, an existing key agreement (KA) scheme - all parties contribute equally to the group key - to tolerate multiple member failures with low cost. We achieve this by enhancing Hypercube with a novel adaptively proactive algorithm. Members are assumed to be already authenticated via some underlying mechanism and we only focus on the design and analysis of a fault-tolerant scheme. Our algorithm has been evaluated and compared with the existing approach. Through our analysis and simulations, we demonstrate its superiority in terms of robustness and efficiency.},
	address = {Cancun, Mexico},
	booktitle = {Seventh International Conference on Networking (ICN 2008)},
	pages = {pp. 223-231}
}
@conference {
	title = {New Algorithms for the Efficient Design of Topology-Oriented Key Agreement Protocols in Multi-hop Ad Hoc Networks},
	author = {Striki, Maria., Baras, John S., Manousakis, Kyriakos.},
	year = {2008},
	month = {03/2008},
	abstract = {Securing group communications in resource constrained, infrastructure-less environments such as Mobile Ad Hoc Networks (MANETs) has become one of the most challenging research directions in the areas of wireless network security. MANETs are emerging as the desired environment for an increasing number of commercial and military applications, addressing also an increasing number of users. Security, on the other hand, is an indispensable requirement of our modern life for all these applications. The inherent limitations of such dynamic and resource-constraint networks impose major difficulties in establishing a suitable secure group communications framework. This is even more so for the task of Key Agreement (KA), under which all parties contribute equally to the group key. The logical design of efficient KA protocols has been the main focus of the related research to-date. Such a consideration, however, gives only a partial account on the feasibility and actual performance of a KA protocol in a real multi-hop network. This is because protocols have been evaluated only in terms of the group key related messaging in isolation from the underlying network functions that interact with the logical scheme and support its correct execution (i.e. routing). In this work, we contribute towards efficiently extending a number of Diffie-Hellman (DH)-based group KA protocols in wireless multi-hop ad-hoc networks, and measuring their actual performance over these networks. Towards this end, we introduce a number of new algorithms that intelligently blend the logical protocol design with the underlying routing and network topology, to produce schemes that substantially improve on the metrics of interest. Indeed, the resulting protocols accomplish this goal, as our analytical and simulation results indicate.},
	address = {Berlin, Germany},
	booktitle = {6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt{\textquoteright}08)},
	pages = {pp. 384-393}
}
@conference {
	title = {Modelling and Optimization for Multi-hop Wireless Networks Using Fixed Point and Automatic Differentiation},
	author = {Baras, John S., Tabatabaee, Vahid., Papageorgiou, George., Rentz, Nicolas.},
	year = {2008},
	month = {03/2008},
	abstract = {We develop and evaluate a new method for estimating and optimizing various performance metrics of multi-hop wireless networks, including MANETs. We introduce a simple approximate (throughput) loss model that couples the physical, MAC and routing layers effects. The model provides quantitative statistical relations between the loss parameters that are used to characterize multiuser interference and physical path conditions on the one hand and the traffic rates between origin-destination pairs on the other. The model considers effects of the hidden nodes, node scheduling algorithms, MAC and PHY layer failures and unsuccessful packet transmission attempts at the MAC layer in arbitrary network topologies where multiple paths share nodes. We apply Automatic Differentiation (AD) to these implicit performance models~and develop a methodology for sensitivity analysis and parameter optimization for wireless protocols. Finally, we provide simulation experiments to evaluate the effectiveness and performance estimation accuracy of the proposed models and methodologies.},
	address = {Berlin, Germany},
	booktitle = {6th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt{\textquoteright}08)},
	pages = {pp.  295 -300}
}
@conference {
	title = {Clustering Characteristics of Millimeter Wave Indoor Channels},
	author = {Neekzad, Behnam., Sayrafian, Kamran., Baras, John S.},
	year = {2008},
	month = {03/2008},
	abstract = {Temporal-Angular channel sounding measurements of an indoor millimeter wave channel (60 GHz) is analyzed to determine whether ray arrivals at the receiver form clusters in the two-dimensional time-angle space. The channel behavior for directional antennas (with various 3dB beamwidths) at the transmitter is discussed and geometric interpretation of the results is provided.},
	address = {Las Vegas, Nevada},
	booktitle = {IEEE Wireless Communications \&amp; Networking Conference},
	pages = {pp. 1217-1222}
}
@conference {
	title = {Constrained Coalitional Games and Networks of Autonomous Agents},
	author = {Baras, John S., Jiang, Tao., Purkayastha, Punyaslok.},
	year = {2008},
	month = {03/2008},
	abstract = {We develop a unifying analytical and optimization based framework for the design, operation and performance evaluation of networks of dynamic autonomous agents. The fundamental view is that agents in such a network are dynamic entities that collaborate because via collaboration they can accomplish objectives and goals much better than working alone, or even accomplish objectives that they cannot achieve alone at all. Yet the benefits derived from such collaboration require some costs (e.g. communications), or equivalently, the collaboration is subject to constraints. Understanding and quantifying this tradeoff between the benefits vs the costs of collaboration, leads to new methods that can be used to analyze, design and control/operate networks of agents. Although the inspiration for the framework comes from social and economic networks, the fundamental ideas and in particular the methodology of dynamic constrained coalitional games (DCCG) can unify many concepts and algorithms for networks in various areas: social networks, communication networks, sensor networks, economic networks, biological networks, physics networks. We then analyze a specific instance of such tradeoffs arising in the design of security-aware network protocols. We extend network utility maximization (NUM) so as to encompass security metrics such as {\textquotedblleft}trust{\textquotedblright}. The trust values assigned to nodes are based on interaction history and community-based monitoring. The effect of these trust values on the resulting protocols is that in routing and media access scheduling node trustworthiness is automatically considered and used. We develop a distributed algorithm for the joint physical-MAC-routing protocol design. Our extension to NUM with security concerns leads to resilient networks.},
	address = {St. Julians, Malta},
	booktitle = {Third International Symposium on Communications, Control and Signal Processing},
	pages = {pp. 972-979}
}
@conference {
	title = {Trust and Reputation in Communication, Social and Other Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {San Diego, CA},
	organization = {Department of ECE and CALIT Center, University of California San Diego}
}
@conference {
	title = {Trust and Reputation in Communication, Computer and Social Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {Sunnyvale, CA},
	organization = {Fujitsu Labs of America}
}
@conference {
	title = {Dynamic Iterations on Partially Ordered Semirings with Applications to Trust Evaluation in Networks},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {Lausanne, Switzerland}
}
@conference {
	title = {Path Problems, Network Optimization and Applications to Networked Systems},
	author = {Baras, John S.},
	year = {2008},
	month = {02/2008},
	address = {Lausanne, Switzerland},
	organization = {Telecommunications Laboratory, EPFL}
}
