Equalizer Design to Maximize Bit Rate in ADSL Transceivers

Prof. Brian L. Evans

Department of Electrical and Computer Engineering
The University of Texas at Austin, Austin, TX 78712

Friday, February 21st, 3:00 PM, ENS 637

bevans@ece.utexas.edu

Abstract

Equalizer design is the key to maximizing bit rate in an ADSL modem. The equalizer shortens the channel impulse response to a preset length and corrects for frequency distortion. This talk reviews several methods for channel shortening in the context of ADSL transceiver design. Channel shortening, however, has many applications in both wired and wireless communications.

In particular, this talk describes three ADSL equalizer structures and design methods for them. For the conventional equalizer, channel shortening is performed by a single finite impulse response (FIR) filter. We describe two channel shortening methods developed at UT Austin that attempt to maximize bit rate. We also describe the dual-FIR equalizer, and the per-tone equalizer. The per-tone equalizer resembles a filter bank. We compare the tradeoff in achievable bit rate vs. implementation complexity in conventional and per-tone equalizers.

We have implemented dozens of design methods for conventional, dual-path, and per-tone equalizers in a Matlab toolbox that is available on our ADSL transceiver design project page at

http://www.ece.utexas.edu/~bevans/projects/adsl/index.html

Biography

Brian L. Evans is an Associate Professor in the Department of Electrical and Computer Engineering at The University of Texas at Austin. His research and teaching efforts are in embedded real-time signal and image processing systems. Recent work in signal processing includes developing the first channel shortening algorithm that maximizes bit rate and is realizable in real-time fixed-point software. Recent work in imaging includes the design, analysis, and quality assessment of image halftoning by error diffusion in desktop printers and monitors. Dr. Evans has published over 100 refereed conference and journal papers. His B.S.E.E.C.S. (1987) degree is from the Rose-Hulman Institute of Technology, and his M.S.E.E. (1988) and Ph.D.E.E. (1993) degrees are from the Georgia Institute of Technology. He received a 1997 National Science Foundation CAREER Award.

A list of Wireless Networking and Communications Seminars is available at from the ECE department Web pages under "Seminars". The Web address for the Wireless Networking and Communications Seminars is http://signal.ece.utexas.edu/seminars