Systems Seminar
A Virtual Representation for Multi-Antenna Wireless Channels
Prof. Akbar Sayeed
UW ECE Department
Abstract
The use of multiple-antenna arrays has emerged as a promising technology
for dramatically increasing the information capacity and reliability of
wireless communication systems. Accurate yet tractable channel modeling
is critical to realizing the potential of antenna arrays. The underlying
physical channel exhibits complex characteristics due to signal scattering
over multiple paths, each path associated with a propagation delay, a
Doppler shift (due to motion), directional angles, and a complex path gain.
Current modeling philosophies are exemplified by two extremes: idealized
but unrealistic statistical models and detailed physical (ray tracing) models
that directly capture the multipath propagation but are difficult to
incorporate in system design. The key premise of our work is that it is not
the physical channel by itself but a fundamental understanding of its
interaction with the signal space that is critical from a communication
theoretic viewpoint. I will present a four-dimensional Karhunen-Loeve-like
virtual representation for space-time channels that captures the essence of
such interaction in time, frequency and space and exposes the intrinsic
degrees of freedom in the channel. The virtual representation is essentially
a Fourier series dictated by the finite array apertures, signaling duration
and bandwidth and corresponds to a uniform, fixed sampling of the
angle-delay-Doppler scattering space. It yields a simple geometric
interpretation of the effects of scattering on channel statistics and capacity.
The talk will discuss various insights into the structure of space-time
channels afforded by the virtual representation as well its applications in
capacity assessment, space-time code design, and wireless networks.
Time and Place: Mon., Feb. 3, at 4:00 pm in 4610 Engr. Hall.
*** NOTE SPECIAL DAY AND TIME ***
SYSTEMS SEMINAR WEB PAGE:
http://www.cae.wisc.edu/~gubner/seminar/