Past Events

Time reversibility plays an important role in disciplinesconcerning dynamical systems, e.g. in physics, statistical mechanics,stochastic processes, and biology. However, its use inproviding information-theoretic fundamental limits appears tobe somewhat limited. Recent developments at the intersectionof information theory and control have demonstrated howdirected information characterizes fundamentallimitations of stochastic systems with dynamics.In this talk, we connect time reversibility of Markov chainsto maximization of directed information for a classof stochastic dynamical systems.

Abstract: Despite its marvelous success over the last three decades, the Global Positioning System (GPS)has two Achilles heels: its signals are weak and|in the case of civil GPS|unauthenticated. At UTAustin's new Radionavigation Laboratory, directed by Assistant Professor Todd Humphreys, we areworking to address both these vulnerabilities.

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Abstract: The geometry of the location of mobiles and/or base stations plays akey role in several classes of wireless communication networks whereit determines the signal to interference ratio for each potentialchannel and hence the possibility of establishing simultaneouslysome set of communications at a given bit rate. Stochastic geometry provides a natural way of defining (and computing)macroscopic properties of such networks, by some averaging overall potential geometrical patterns for e.g. the mobiles.

Abstract:We consider the problem of determining achievable rates inheterogeneous wireless networks. We analyze the impact of location,traffic, and service heterogeneity. Consider a wireless network with nnodes located in a square of area n communicating with each other overGaussian fading channels. Location heterogeneity is modeled byallowing the nodes in the wireless network to be deployed in anarbitrary manner on the square area instead of the usual randomuniform node placement. For traffic heterogeneity, we analyze then*n-dimensional unicast capacity region.

Laboratory-based mobile wireless testbeds such as MeshTest and the CMUWireless Emulator are powerful platforms that allow users to performcontrolled, repeatable, mobile wireless experiments in the lab.Unfortunately such systems can only accommodate 10-20 nodes in anexperiment. We have designed and built a system which uses softwarevirtualization and live migration to facilitate experiments involvinggeographically sparse networks with many multiples of the number ofphysical nodes available on such a testbed.

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Abstract: Cooperative game theory provides a rich set of mathematical tools for modeling cooperative scenarios in various disciplines. In this talk, we introduce cooperative games, namely coalitional games and we discuss their applications in wireless networks. In particular, we provide a novel classification of coalitional games, tailored for wireless networks problems. We focus on introducing the main fundamental concepts for each class of coalitional games, and we describe suitable solution concepts.

TBA

I discuss the family of methods known under the names of BeliefPropagation (BP) in artificial intelligence, Message Passing(MP) in computer science/information theory, and Bethe-Peierls(still BP) approximation in statistical physics. These BP/MPmethods offer efficient and distributed algorithmic solutions,along with rich theoretical guarantees, for variety of problemsin statistical inference and optimization. The power of BP/MPwill be illustrated on examples from error-correction, particletracking in fluid mechanics and switching control over powergrids.