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Power Control Strategies for Delay Constrained Channels 

Rohit Negi
Stanford University

March 2, 2000
HH 1112
10:30 a.m.


Astract
    

In this talk, I will introduce and solve problems related to delay
constrained communication channels. Mobile wireless systems suffer
signal degradation due to fluctuations in the received power. These
fluctuations, called channel fading, are directly related to the motion
of the receiver handset. As a result, it becomes hard to guarantee a
specific target performance in such systems, unless it is possible to
"average out" the fluctuations (the notion of "ergodic capacity").

However, several wireless applications, such as voice and real-time
video, have strict delay requirements. They allow a certain time-window
(hence "delay constraint") within which all processing should occur.
They demand a certain target performance within this window. For
example, an application may demand a target data rate of 200
kilobits/sec to be achieved within a delay constraint of 10 millisec,
with high probability.  Within this time-window, the channel  may go
through only a few fades, thus ruling out the possiblity of averaging
them out. Communication systems operate on a power budget, which cannot
be exceeded in delivering the specified performance. The talk will show 
optimal transmission schemes for delay constrained channels. Such
schemes involve controlling the power at the transmitter, as a function
of the channel quality. I will
introduce and solve the problem, derive several interesting extensions,
and address some practical issues related to it.

Bio:


Rohit Negi received a Bachelor of Technology degree (with President of
India gold medal) from the Indian Institute of Technology, Bombay in
1995, and an M.S. from Stanford University in 1996, both in Electrical
Engineering. He is currently working on a Ph.D. in Electrical
Engineering, with Prof. John Cioffi at Stanford University. His research
interests include wireless fading channels, space-time processing, OFDM
systems, and other signal processing aspects of communication systems.