Systems and Control Research Group

Second Summer
Systems and Control Workshop 
Communications and Control
Year 2004

Invited Speakers, Titles and Abstracts

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Speaker: Professor Tamer Basar, University of Illinois, Urbana-Champaign, USA

Title: Resource Management and Control in Large-Scale Communication Networks.

Abstract: Today's communication networks, and particularly the Internet, can be seen as super-fast expressways, transporting packets from sources to destinations along most efficient routes, while respecting priorities and quality-of-service specifications. They are heterogeneous, in terms of both the traffic they can accommodate and the services they offer. The quest for regulating traffic in such a medium, with utmost efficiency, has been and still is the driving force behind the technological advances in this area. Some of this regulation is done by the network itself (speciffically, the service providers), through fast switch and router designs, protocol designs, capacity expansions, and admission policies, and some of it is done by the individual users under incentives or disincentives provided by the network (such as price structures), aimed at achieving a certain pattern of usage of the available resources (such as the bandwidth). The users are faced with a multitute of issues, among which are (i) at what rate to inject packets into the network, and (ii) how to adjust these rates in response to (delayed) congestion information received from the network. Occasionally, users are also faced with the task of making decisions on routing, again based on information received from the network. The overall system is a very complex one, involving a very large number of \players" with little if any cooperation, and operating under minimal information.

Several branches of engineering (particularly, control, communications, and computing) as well as economics (particularly, game theory) provide the conceptual, analytical and technological tools necessary for architecting such networks and ensuring that they operate harmoniously in spite of their heterogeneity. Control theory plays a particularly important and relevant role here, as an eĆective architecture requires the design of robust distributed feedback loops that would function under decentralized, delayed information. This talk will describe the underlying issues in such a design for the Internet, discuss what the current technology offers, and present some new architectures for both source and link dynamics, which provide improved performance over the current TCP structures (such as TCP Reno) and active queue management (AQM) schemes (such as RED).

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Speaker: Professor R. Evans, University of Melbourne

Title: Entropy, Information and Control

Abstract: It has long been conjectured that the solution to a number of difficult open problems in control theory are in some way connected to an appropriate theory of information for controlled dynamical systems. In this talk we review the status of modern control theory and discuss recent progress towards the synthesis of information theory and control.

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Speaker: Dr. Girish Nair, University of Melbourne

Title: Towards an Information Theory for Networked Control Systems

Abstract: In emerging applications such as micro-electromechanical systems, sensor networks and mobile telephone power control, the object is to control one or more dynamical systems by feeding back measurements over networks with low data rates. The achievable controller performance can be severely affected by the communication resources available, making it vital to understand how the communication and control objectives interact. This talk aims to give a sketch of several recent, fundamental results in the field of networked control. Motivated by the role of information theory in communications, the emphasis is on delineating ultimate bounds, without restriction to specific schemes such as memoryless A-D conversion or linear coders and controllers. In particular, the focus is on characterising the smallest feedback data rate above which various types of dynamical system can be stabilised, using tools from information theory, quantisation and dynamical systems theory. The extension of these results to multiterminal control systems and noisy channels still remains a pressing open question.

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Speaker: A/Prof. Predrag Rapajic, University of New South Wales

Title: Adaptive Receivers in Time Variable Multiuser Channels

Abstract: Time variable communication channels are inherent to multiuser
Mobile Communication Systems. The talk will address implementation
of Kalman filtering technique in adaptive multiuser detection.

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Speaker: Professor Andrey Savkin, University of New South Wales

Title: An Analogue of Shannon Information Theory for Networked Control Systems

Abstract: Recent unpublished results on state estimation and stabilization of linear control systems via noisy discrete communication channels. These results can be viewed as an analogue of the Shannon theorems for Networked Control Systems.

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Speaker: Professor Patrick Senac, University of New South Wales

Title: Towards the formal modeling of multimedia applications and protocols.

Abstract: Based on a formal approach, this talk introduces the problematic of multimedia application QoS needs and its implications on transport protocols services and mechanisms. The work introduced in this talk has influenced application layer standards defined by the W3C such as the SMIL 2.0 language as well new generation transport protocols currently defined in the framework of the IETF.