A multiple transmit antenna, single receive antenna (per receiver) downlink channel with limited channel feedback is considered. Given a constraint on the total system-wide channel feedback, the following question is considered: is it preferable to get low-rate feedback from a large number of receivers or to receive high-rate/high-quality feedback from a smaller number of (randomly selected) receivers. Acquiring feedback from many users allows multi-user diversity to be exploited, while highrate feedback allows for very precise selection of beamforming directions. It is shown that systems in which a limited number of users feedback high-rate channel information significantly outperform low-rate/many user systems. The marginal benefit of channel feedback is very significant up to the point where the CSI is essentially perfect.
Krishna, G.Vamshi; Kumar, Ch. Suresh; Kiran, U.; and Reddy, K. Rajesh
"Multi User Diversity Evaluation in MIMO HSDPA Downlink Channels,"
International Journal of Communication Networks and Security: Vol. 1
, Article 6.
Available at: https://www.interscience.in/ijcns/vol1/iss3/6