Systems Seminar
Wireless Communication and Sensing in Time, Frequency, and Space
Prof. Akbar Sayeed
UW ECE Department
Abstract
Multipath signal propagation, the most salient feature of wireless channels,
results in detrimental signal fading and yet it is also a key source of
diversity (e.g., spatial, spectral, multiuser) for increasing the capacity
and reliability of wireless communication systems. While technological
advances in agile RF front-ends are enabling new ways to exploit multipath
diversity, there are significant gaps in our current understanding of the
communication-theoretic limits of such channels. To this end, I will first
present a virtual modeling framework for multipath channels that
characterizes channel diversity, and its dual, channel coherence, at a
resolution commensurate with the signal space dimensions (number of antennas,
bandwidth, signaling duration). A key new insight is that channel diversity
scales sub-linearly with the signal space dimensions and as a result the
channel becomes progressively more coherent as dimensions increase.
In particular, I will discuss adaptive-resolution beamforming that exploits
spatial coherence and promises a dramatic increase in capacity in the
wideband/low-SNR regime. In the second part of the talk, I will introduce
Active Wireless Sensing (AWS) -- a promising new approach for rapid and
energy-efficient information retrieval in wireless sensor networks.
AWS has two primary attributes: i) the sensors are "dumb" in that they have
limited computational ability, and ii) a "smart" information retriever
interrogates the sensors with wideband space-time waveforms to elicit
desired information. The communication architecture in AWS is inspired by
virtual modeling of the underlying sensing channel: sensors act as activescatterers to generate a multipath response to interrogation signals.
Time and Place: Wed., Nov. 16, at 3:30 pm in 4610 Engr. Hall.
SYSTEMS SEMINAR WEB PAGE:
http://www.cae.wisc.edu/~gubner/seminar/