Tata Institute of Fundamental Research

Scheduling Multi-Antenna Broadcast Systems with Heterogeneous Users

Seminar
Speaker: Krishna Jagannathan Massachusetts Institute of Technology Room 31-011 Cambridge MA 02139 United States of Ame
Date: Thursday, 10 Dec 2009 (all day)
Venue: AG-69

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Abstract:  Information-theoretic results indicate that multi-user multi-antenna systems provide potentially huge capacity gains. However, these results assume sophisticated coding techniques and perfect channel state information which may require a prohibitive amount of feedback. We show that transmitting to just a few suitably selected users is asymptotically optimal as the user population grows large, while dramatically reducing the feedback overhead and operational complexity. Specifically, we consider a multi-antenna broadcast system with M transmit antennas, and a heterogeneous user population. we tackle the problem of maximizing a weighted sum rate quantity. We establish a novel upper bound for the weighted sum capacity, which we then use to show that the maximum expected weighted sum rate can be asymptotically achieved by transmitting to a suitably selected subset of at most MC users, where C denotes the number of distinct user classes. Numerical experiments indicate that the asymptotic results are remarkably accurate and that the proposed schemes operate close to absolute performance bounds, even for a moderate number of users.