TITLE: Capacity Limits of Wireless Channels with Multiple Antennas: Challenges, Insights, and New Mathematical Methods
SPEAKER:
Andrea Goldsmith
Department of Electrical Engineering
Stanford University
DATE: 3:00-4:00 P.M., Friday, May 16, 2003
LOCATION: Half Dome, 3L (PA)
HOST: Vinay Deolalikar
ABSTRACT:
Wireless systems of the future must support ubiquitous multimedia
communications between people as well as devices. There are many
research challenges associated with such systems, including limited
bandwidth, random variations in the wireless channel, and battery
constrants in small radio transceivers. Many of these challenges can be
overcome with multiple antennas at the transmitters and receivers of
the wireless network, since these antennas both increase data rate
and reduce channel randomness. However, traditional methods for determining
Shannon capacity fail for channels with multiple antennas, especially
when there are multiple users, channel variations over time, or channel
memory.
We present several new mathematical techniques to study Shannon capacity
of multiantenna wireless channels with these properties, including
duality, dirty paper coding, and Lyapunov exponents for products of
random matrices. These techniques provide new tools for solving open
capacity problems. In addition, duality and dirty paper coding yield
much insight into optimal transmissions strategies and the relationship
between broadcast and multiple access channels. Lyapunov exponents
expose an intriguing connection between entropy, capacity, and
dynamic systems theory.
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