MIMO Broadcast Channels with Partial CSI: Throughput, Fairness, and Delay

SPEAKER: Mr. Masoud Sharif, CalTechABSTRACT: The downlink scheduling in a cellular system has to deal with two conflicting goals, namely maximizing the throughput yet at the same time maintaining fairness among the users and minimizing the delay. Information-theoretic results on broadcast channels yield schemes that only maximize the throughput, irrespective of the delay and fairness. In this talk, we first obtain the scaling laws of the sum-rate capacity (throughput) in terms of the number of receive/transmit antennas and the number of users n, under different channel state information (CSI) assumptions. It turns out that the sum-rate capacity heavily depends on the availability of CSI at the transmitter. In cellular systems, the number of users is typically large and obtaining full CSI from all users may not be practically feasible. Therefore, we propose a scheme that only requires partial CSI yet attains the same throughput scaling law as that of full CSI. We show that if the number of transmit antennas is large enough, our scheduling becomes fair, irrespective of the path-loss of users. We further show that the expected worst case delay when using throughput optimal scheduling is log n times worse than the minimum achievable delay. Finally, we look into the trade-offs between the throughput and the worst case delay.BIO: Masoud Sharif was born in 1977. He received the BS (with honors) and MS degrees in electrical engineering from Sharif University of Technology, in 1999 and 2001, respectively. He is currently working towards the Ph.D. degree in the Department of Electrical Engineering, California Institute of Technology, Pasadena, CA.HOST: Dr. Keith M. Chugg, x.07294, chugg@usc.edu

Location: Hughes Aircraft Electrical Engineering Center (EEB) - -248

Audiences: Everyone Is Invited

Contact: Mayumi Thrasher