Time-Domain Equalization for ADSL Transceivers

Prof. Brian L. Evans
Department of Electrical and Computer Engineering
The University of Texas at Austin

Friday, September 7th, 3:00 PM, ENS 127

bevans@ece.utexas.edu

Key Graduated Ph.D. Students: Guner Arslan (Cicada), Biao Lu (Schlumberger)

Key Graduate Students: Ming Ding, and Milos Milosevic

Key Seniors: Wade Berglund, Jerel Canales, David Love, Scott Margo, and Jeff Wu

Other Key Collaborators: Lloyd Clark (Schlumberger) and Sayfe Kiaei (ASU)

Talk

Abstract

G.DMT and G.lite Asymmetric Digital Subscriber Line (ADSL) modems rely on discrete multitone modulation (DMT). DMT divides a broadband channel into many narrowband subchannels and modulates encoded signals onto the narrowband subchannels by using the fast Fourier transform (FFT). An ADSL receiver employs a finite impulse response filter, known as a time-domain equalizer (TEQ), to shorten the effective duration of the channel impulse response. Some TEQ design methods explicitly reduce inter-symbol interference (ISI).

The talk presents four new methods for time-domain equalizer (TEQ) design to increase the bit rate:

  1. an optimal Maximum Bit Rate method
  2. a near-optimal Minimum ISI method
  3. two suboptimal divide-and-conquer greedy algorithms
One surprising result is that a three-tap TEQ designed by the Minimum ISI method can achieve 96-98% of the matched filter bound on bit rate. This three-tap TEQ gives a higher bit rate than 32-tap minimum mean-squared error TEQs in current use in some commercial ADSL transceivers.

The slides for this talk, as well as dissertations, papers, a Matlab toolbox, and software releases for the Minimum ISI methods on the TI C6000 and C5000 digital signal processors, are available at

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

Biography

Brian L. Evans is a tenured Associate Professor in the Department of Electrical and Computer Engineering at The University of Texas at Austin. He focuses his research and teaching efforts on embedded real-time signal and image processing systems. Dr. Evans has published over 90 refereed conference and journal papers in these fields. His current research interests include the design and real-time implementation of ADSL/VDSL transceivers, desktop printer pipelines, video codecs, and 3-D sonar imaging systems. 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 is an Associate Editor of the IEEE Transactions on Image Processing, a member of the Design and Implementation of Signal Processing Systems Technical Committee of the IEEE Signal Processing Society, and a Senior Member of the IEEE. He is a recipient of a 1997 National Science Foundation CAREER Award.

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://signal.ece.utexas.edu/seminars