ADSL System Design: Challenges and Opportunities

Dr. Murtaza Ali

Manager, Wireline Communications Branch
Communications Lab
DSPS R&D Center
Texas Instruments
P.O. Box 660199, MS 8653, Dallas, TX 75266-0199

Friday, November 30th, 3:00 PM, ENS 637

mali@ti.com


Abstract

There are three main broadband access methodologies being developed. These are ADSL over normal telephone lines, cable modems over existing cable topology and fixed wireless. The two front runners are the ADSL and cable modems with the telephone operators deploying the former and the cable operators pushing the latter. ADSL works over dedicated phone line using the discrete multi-tone (DMT) modulation that is a variation of orthogonal frequency division multiplexing (OFDM) technique. In real deployment, ADSL systems face a variety of noise environments including cross-talk, radio frequency ingress, long channel response etc. Each of these environments provide unique challenges to ADSL system design. In this talk, we will provide a review of these impairments and describe how they impact the choice of the system including the analog front-end and signal processing algorithms. We will specially discuss the choice of echo cancelled (EC) versus frequency duplex (FDD) based systems as well as the equalization algorithms. Finally, we will describe research opportunities in ADSL system design to improve performance and stability in presence of various impairments.

Biography

Murtaza Ali was born in Dhaka, Bangladesh. He received his B.Sc. in Electrical Engineering from Bangladesh University of Engineering and Technology in 1989 and his M.S and Ph.D. in Electrical Engineering from University of Minnesota in 1993 and 1995 respectively. In 1995 after graduation from University of Minnesota, he joined Texas Instruments. At Texas Instruments, Dr. Ali was initially involved in audio and speech processing. He worked on wavelet based audio compression and noise suppression. He was also involved in developing technology related to acoustic echo cancellation. Since 1998, Dr. Ali concentrated his activities in the area of communication systems. He was involved in the standardization of several communication technologies including V.90 in the ITU-T, Home phoneline Networking modems in the HPNA organization and the powerline home networking systems under Home Plug consortium. For his contributions to TI, Dr. Ali became a Distinguished Member of Technical Staff in 2001. He is currently managing the ADSL research activities within the Digital Signal Processing Solutions (DSPS) R&D Center at Texas Instruments. His current interests include system and algorithm designs for OFDM and DMT based communication techniques, compatibility of different communication services especially in the wired medium.

Dr. Ali holds 3 patents and has published more than 20 papers in international journals and conferences and has written over 30 internal reports.


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