Memory-based opportunistic multi-user beamforming

A scheme exploiting memory in opportunistic multiuser beamforming is proposed. The scheme builds on recent advances realized in M. Sharif and B. Hassibi, 2005, in the area of multi-user downlink preceding and scheduling based on partial transmitter channel state information (CSIT). Although the preceding and scheduling done in M. Sharif and B. Hassibi, 2005 is optimal within the set of unitary precoders, it is only so asymptotically for large number of users. Secondly, this scheme is unable to exploit potential time correlation of the channel. In this paper, we show (1) that exploiting memory in the transmitter allows to fill the gap to optimality for fixed (even low) number of users for time correlated channels, (2) how such schemes can be extended to take fairness into account in the proportional fair sense