Multi-user Aware Limited Feedback for MIMO Systems

Consider a wireless communication system where the base station has multiple antennas and users have a single antenna. For both the multiple access and broadcast channels, the sum capacity scales at best linearly with the number of antennas at the base station and double logarithmically with the number of users as the user pool grows asymptotically. Achieving this optimal capacity scaling potentially requires feedback of channel state information (CSI) from all users, leading to overflow of the feedback channel. This paper proposes a limited feedback strategy that provides feedback control such that a sum CSI feedback rate constraint is satisfied. It is proved that a wireless multi-antenna system using the proposed limited feedback strategy achieves the optimal capacity scaling for both the multiple access and the broadcast channels despite the sum feedback rate constraint.