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