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In this paper, a new multiple access scheme suitable
for the forward link transmission in a multiuser MIMO
system is introduced. Unlike traditional MIMO multiple
access schemes, which rely on orthogonal-temporal channels
(e.g. TDMA), the proposed scheme, namely the spread
space-spectrum multiple access (SSSMA), exploits the
space-domain for multiuser multiplexing. As its name
suggests, SSSMA utilizes the available degrees of freedom
offered by the spread-spectrum and those by the multiple
transmit antennas to perform multiple access. At the
base-station transmitter, each coded data stream corresponding
to a unique user-channel is modulated with a user specific
two-dimensional spreading sequence and added together
with other channels·modulated signals. At each
user? receiver, the multiple-access-interference (MAI)
generated from the same base station is mitigated through
iterative multiuser detection and decoding. We focus
on the performance of SSSMA in two different environments,
(1) local point-to-multipoint network such as LAN, (2)
a power-controlled cellular system. It is shown that
not only does the SSSMA offer near-theoretic-capacity
performance in both environments, it is able to exploit
a new form of diversity, namely the space-interferers-diversity,
in an ideal power controlled network while other MIMO
multiple access schemes fail to do so. This scheme essentially
introduces spread spectrum concepts into MIMO systems
and holds great promise for cellular-type systems that
employ universal frequency re-use.
Biography
Elvino S. Sousa received his B.A.Sc. in engineering
science, and the M.A.Sc. in Electrical Engineering from
the University of Toronto in 1980 and 1982 respectively,
and his Ph.D. in electrical engineering from the University
of Southern California in 1985. Since 1986 he has been
with the department of Electrical and Computer Engineering
at the University of Toronto where he is now a Professor
and BUL Chair in Computer Engineering. He has performed
research in spread spectrum systems and CDMA since 1983.
His current interests are in the areas of high-speed
CDMA systems, smart antenna systems, software radio,
ad-hoc networks, and wireless system concepts for 4th
generation networks. At the University of Toronto he
is the director of the wireless lab, which has undertaken
research in CDMA wireless systems for the past 16 years.
He has been invited to give lectures and short courses
on spread spectrum, CDMA, and wireless communications
in a number of countries, and has been a consultant
to industry and Governments in the area of wireless
systems internationally. He was the technical program
chair for PIMRC 95, and vice-technical program chair
for Globecom '99, and has been involved in the technical
program committee of numerous international conferences.
He was the past chair of the IEEE Technical committee
on Personal Communications. He has spent sabbatical
leaves at Qualcomm and Sony CSL/ATL, where he was the
holder of the Sony sabbatical chair. Currently he is
the holder of the Bell University Labs Chair in Computer
Engineering with a mandate for research in wireless
communications.
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