A Lower Bound to the Sum-Rate of MIMO Broadcast Channels with Limited-Rate Feedback

This paper investigates the sum-rate performance of a multiuser multi-antenna downlink system. Assuming limited channel state information at the base station and a large number of single antenna users in a cell, we investigate a semi-orthogonal user selection scheme with a total feedback rate constraint. The sum-rate performance of the proposed scheme is analyzed under zero-forcing linear precoder at base station, and a lower bound to the sum-rate of broadcast channels with quantized channel direction information and channel quality information is derived. This lower bound is used to evaluate the performance of broadcast channels with finite-rate feedback of channel state information and semi-orthogonal user selection. Numerical examples show that our analytical results agree with Monte Carlo simulations.