Bjorn Bjerke

Multiple-Antenna Systems for Wireless Communications"

Date: Thursday, May 17, 2001 3:00 p.m. Room 141 Ryder

Abstract

Recent research in information theory has shown that the capacity of wireless systems can be dramatically improved by using multiple antennas at both the transmitter and the receiver. With N transmit antennas and M receive antennas, N spatial channels can be supported simultaneously in the same frequency band when the multipath scattering is sufficiently rich. By transmitting data in parallel through these channels, the data rate can be increased by a factor of N, assuming that the fading in the channels between pairs of transmit and receive antennas is statistically independent. Ideally, the M receiving antennas can provide M'th order diversity reception for each of the transmitted signals in addition to whatever implicit diversity the channel has to offer. Another recent advance in communication theory has occurred with the development of iterative decoding algorithms for concatenated codes. The discovery of these so-called turbo decoding algorithms is considered to be a small revolution in digital communcations, as these techniques allow for reliable communications at very low signal-to-noise ratios. The purpose of this dissertation is to combine and further develop the ideas of multiple-antenna systems and iterative decoding. In particular, we aim to analyze and design receiver structures for multiple-antenna systems in multipath fading channels. We begin by considering an uncoded system, and define optimal and suboptimal receiver structures for this system in Rayleigh fading with and without intersymbol interference. Next, we consider coded systems and study receiver structures which combine the demodulation and decoding processes in an iterative manner, analogous to turbo decoding of serially concatenated codes. We evaluate the performance of these receivers analytically as well as through simulations. Finally, in a somewhat separate work, we investigate the use of transmit and receive diversity schemes for use on the downlink of third generation cellular systems.

Thesis Committee:
Prof. John G. Proakis
Advisor Prof. Masoud Salehi
Dr. Zoran Zvonar, Analog Devices, Inc.