Coding for Wireless Systems with Multiple Transmit and Receive Antennas

Dr. Tolga Duman

Dept. of Electrical Engineering
Arizona State University
Tempe, Arizona

Monday, April 16th, 11:00 AM, ENS 637

Abstract

The demand for voice and data transmission over wireless channels is increasing as a tremendous pace. Unfortunately, the characteristics of the wireless channel (e.g., fading and interference) impose obstacles for satisfying this demand. The single most effective technique to accomplish reliable communication over a fading channel is "diversity" that attempts to provide the receiver with independently faded copies of the transmitted signal with the hope that at least one of these replicas will be received correctly. Diversity may be realized in many ways including frequency diversity, time diversity, antenna diversity, modulation diversity, etc. Channel coding may also be used to provide (a form of time) diversity for immunization against impairments of the wireless channel. In addition, various diversity techniques may be combined to further improve the system performance in a wireless environment. Space--time coding which combines channel coding with space diversity (i.e., antenna diveristy) is a recent example of combining different diversity techniques and has proven to be effective in providing high data rates over fading channels.

Currently performance evaluation of the space-time codes over the quasi-static fading channels is performed exclusively by simulation. The usual union bound, even expurgated version diverges since there is no dominant error event. In the first part of the talk, we present a method for obtaining the bit error rate bounds for the ususal space time codes. The performance bounds are based on the idea of expurgation and limiting of the bound before averaging over the fading statistics. We show that this technique provide useful performance bounds as opposed to the standard union bound which diverges. In the second part of the talk we will devise a method of using turbo coded modulation schemes as an alternative to space-time codes. We will illustrate their performance over block fading channels via simulations, and suggest directions of theoretical performance analysis.

Biography

Tolga M. Duman received the B.S. degree from Bilkent University, Turkey, in 1993, and M.S. and Ph.D. degrees from Northeastern University, Boston, in 1995 and 1998, respectively, all in electrical engineering. He joined the Electrical Engineering faculty of Arizona State University as an assistant professor in August 1998. Dr. Duman's current research interests are in digital communications, wireless and mobile communications, channel coding, turbo codes, coding for recording channels, and coding for wireless communications.

Dr. Duman is the recipient of the National Science Foundation CAREER Award, IEEE Third Millennium medal, and IEEE Benelux Joint Chapter best paper award (1999). He is a member of IEEE Information Theory and Communication Societies.

A list of Telecommunications and Signal Processing Seminars is available at from the ECE department Web pages under "Seminars". The Web address for the Telecommunications and Signal Processing Seminars is http://anchovy.ece.utexas.edu/seminars