Final program

Abstract

s of Presented Talks Monday August 12, 2002 8:30-9:30 Room : 101 Plenary Talk Bruce Hajek (University of Illinois) A Basket of System Theoretic Problems in Communications Researchers are currently faced with a rich set of problems in the design and analysis of wireless communication systems and high-speed communication networks. The purpose of this talk is to survey several significant open problems which system theory could play a role in solving. The problems include: (a) Providing delay constraints in a large communication network in a distributed way, using delay calculus based on the max-plus algebra, (b) Finding the capacity of cellular networks (will survey the recent use of the theory of large random matrices and related free probability theory), (c) Predicting efficiency and fairness, and designing allocation mechanisms, for the Internet, as thousands of autonomous systems interact through self-interested pricing and congestion, and (d) Distributing limited routing information in a large amorphous network, such as a peer-to-peer network or ad hoc sensor array, to facilitate position location. 9:30-10:30 Room : 101 Invited Talk Roger Brockett (Harvard University) Optimal System Identification for NMR Applications In a wide variety of settings, the measurement of nuclear magnetic resonance (NMR) effects has proven to be a remarkably effective for investigating unknown structures on both large and small scales. Over the years a large body of technique has been developed for improving the sensitivity and resolution of NMR measurements and many recent advances in biochemistry and medicine are dependent on the sophisticated signal processing techniques now used routinely. From a system theoretic perspective, problems in this area can be thought of as identification problems involving bilinear systems. They are distinguished from linear system identification problems by the fact that the quality of the identification is strongly dependent upon the form of the excitatory input applied to the system. Many ingenious techniques, such as the “two dimensional” Fourier transform procedure have been developed based on particular types of input patterns. Because of the low signal to noise ratios inherent in NMR, the optimization of such methods requires the use of stochastic models for the dynamics and measurement processes. In this talk we take a fresh look at problems in this area with a view toward finding computational procedures that will determine the inputs which will optimize specific performance measures. In particular, we explore performance measures related to conditional entropy, and in this way develop a formalism for establishing the mathematical limits on what can be accomplished with better input design. 9:30-10:30 Room : 102 Invited Talk Hans-Andrea Loeliger (ETH) Factor Graphs, Least Squares and Kalman Filtering Factor graphs are graphical models with origins in coding theory and with close relations to Willems-type behavioral system theory. The sum(mary)-product algorithm, which operates by message passing in the factor graph, subsumes a great variety of algorithms in coding, signal processing, and artificial intelligence. In this talk, we apply Forney-style factor graphs to linear models with quadratic cost functions and we show how general versions of Kalman filtering and recursive least squares algorithms arise as instances of the sumproduct algorithm. (An ”isomorphism” of such factor graphs with electrical networks is presented in a separate talk.) 9:30-10:30 Room : 136 Invited Talk Sjoerd Verduyn Lunel (University of Leiden) Control and Stabilization of Systems with Time Delays For dynamical systems governed by feedback laws, time delays arise naturally in the feedback loop to represent effects due to communication, transmission, transportation or tern effects. The introduction of time delays in a system of differential equations results in an infinite dimensional state space. In this paper we give an overview of the basic theory and discuss recent developments concerning the control and stabilization of systems with delays.