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Presenter: Dr. T. Aaron Gulliver - Professor and Acting Chair, Dept. of Electrical and Computer Engineering, University of Victoria
Supervisor:

Date: Thu, December 11, 2003
Time: 14:30:00 - 15:30:00
Place: EOW 430

ABSTRACT

Abstract

It is well known that there has been a tremendous surge in demand for wireless and mobile communications services, such as wireless local area networks (LANs), digital video broadcasting (DVB), digital audio broadcasting (DAB), mobile satellite services, wireless data networks and wireless asynchronous transfer mode (ATM) networking, etc.

Present generation cellular systems (2G-3G) have shaped the modern communications world, as has wireless local area networks such as those based on the IEEE 802.11 standards. The demand for better services, faster, cheaper, with assured quality-of-service (QOS) and enhanced security, requires the development of new communications systems with better spectrum efficiency and higher cellular capacity. These systems must overcome one of the main problems with the reception of normal radio signals, namely, fading caused by multipath propagation, that is, multiple versions of the signal arriving at the receiver. Typical measures of performance are error rate and channel capacity.

Among all the technologies available to combat the effects of fading, diversity is one of the most important. It can greatly improve performance by providing the receiver with multiple signals generated by the same underlying data. Recently space-time coding (STC) has gained much attention as an effective transmit diversity technique.

The capacity and error probability of space-time block coding (STBC) will be presented for PAM/PSK/QAM modulation in Rayleigh, Ricean and Nakagami fading channels. The extension to a Direct Sequence Code Division Multiple Access (DS-CDMA) system employing STBC will also be considered. In addition, this presentation will show the performance degradation in a correlated fading channel.

As wireless products become smaller and faster to meet portability and usage requirements, interference becomes a major concern. Industry measurements have shown that the surrounding electronics contribute greatly to the ambient noise power, and can often lead to an unacceptable noise floor in the receiver. Localized noise and interference is a significant problem in multiple-input multiple-output (MIMO) systems because it spatially correlates the received data which degrades STBC receiver performance through the loss of transmit diversity. An interference suppression solution is considered in conjunction with turbo coding. This is based on a Gaussian noise and interference approximation whereby the STBC detector acquires and refines channel and noise covariance matrices. The performance of both coherent and noncoherent STBC systems will be considered.