Research Projects

This page lists the major research projects in which I am currently involved. As you will see, a common theme of my research is the use of tools and techniques from information theory, communications theory and statistical signal processing to draw insights into the behaviour of wireless communications networks. If you are a prospective postgraduate student with an interest in this type of work please send me an email or drop by my office.

My research is supported primarily by the Australian Research Council through ARC Discovery Grants and my involvement the ARC Special Research Centre for Ultra-Broadband Information Networks (CUBIN). CUBIN is an affiliated program of National ICT Australia (NICTA).

Further information can be obtained by looking at my journal publications.

Optimal Deployment of Wireless Sensor Networks

Wireless sensor networks consist of coordinated sensing devices that offer us new ways to understand and interact with the physical world. For a given technology, the key to both optimising the quality of area monitoring and minimising the cost of a sensor network lies in deciding how best to deploy the sensors. We aim to develop powerful new methods to get the best performance from a planned sensor network. This work is supported by an ARC Discovery Project jointly held with Prof. Doreen Thomas and Dr. Marcus Brazil.

Estimation, Control and Communications

Wireless sensor networks have the potential to dramatically improve the way we do many things, from monitoring the environment and human health to managing complex defence systems. At the heart of all of these monitoring and management tasks lie the fundamental problems of estimation and control. When sensors and controllers are scattered throughout space and share a common communication medium, the estimation and control problems must be tackled taking into account the inherent communication constraints. This project will lead to a deeper understanding of the rich interplay between estimation, control and communications that is integral to the application of wireless sensor networks. This work is supported by an ARC Discovery Project jointly held with A/Prof. Subhrakanti Dey and Dr. Girish Nair.

Cooperation and Macrodiversity

A major current focus of my research is on the role of cooperation in wireless networks. Traditional cellular networks are designed so that at any given time, users are connected to one base station only. Each user will cause interference at other base stations (on the uplink) or at other mobile terminals (on the downlink) and this interference limits capacity. A more modern view is to see the network of base stations as a single spatially distributed transmitter and receiver. On the downlink a number of base stations can transmit a signal intended for a particular mobile while on the uplink, the signal transmitted by a mobile is received at a number of base stations. While this idea of base stations cooperating to transmit and receive information is present to a limited extent in existing cellular networks, there is much more to be gained from more extensive exploitation of “macrodiversity”. We seek to quantify the potential gains from exploiting macrodiversity and to design efficient algorithms for achieving these gains. This work draws upon results from information theory and statistical inference in Bayesian networks and is intimately related to iterative detection and decoding algorithms. This work was supported by an ARC Discovery Project jointly held with A/Prof. Stephen Hanly and Prof. Alex Grant.

Multiuser MIMO and OFDM

Advanced communication techniques allow high spectral efficiencies to be achieved over wireless links. Two of the most important techniques revolve around the use of multiple antennas at both transmitters and receivers (MIMO, space-time coding) and the use of many parallel frequency bands for each user (OFDM). While the performance gains of these techniques have been well demonstrated for point-to-point links, the application of these techniques in multiuser environments such as mobile cellular networks is relatively immature. It is crucially important to understand the performance limitations of these advanced communication techniques in multiuser environments and that is the aim of this project. This work was supported by an ARC Discovery Project jointly held with Dr. Stephen Hanly and Prof. Alex Grant.

Analysis and Design of Multiuser Receivers

In CDMA-based wireless networks, performance measures of interest, such as signal-to-interference ratio, are functions of the signature sequences assigned to each user in the system. This dependence leads to ungainly expressions for network performance indicators and to complex design problems. Recently, a powerful tool has emerged for performance analysis and parameter optimization of CDMA systems. Large system analysis is based on modeling the signature sequences as random quantities and examining the behaviour of the network as the spreading gain and the number of users grows large. In this regime, key performance measures depend on the eigenvalue distributions of large random matrices. Importantly, in many cases of interest, the limiting spectral distributions have a simple form that only depends on the ratio of the number of users to the spreading gain. The end results are performance measures and design rules that are independent of the signature sequences and solely dependent on the key system parameters. In collaboration with colleagues and students, I have employed large system analysis to analyse the performance of multiuser receivers for fading channels and in the design of efficient implementations of linear multiuser detectors.