MIMO broadcast scheduling with limited channel state information

We consider the multiple-input multiple-output (MIMO) broadcast channel in which there arem transmit antennas and n uncoordinated users with a single receive antenna. We examine the maximum throughput in such a system in the scenario when the num-ber of users is much greater than the number of transmit antennas. We derive a lower bound the probability that there exists a set of users such that each user receives a specified rate. We show that through the use of a simple norm-threshold feedback protocol the maximal scaling of the sum rate is achievable and requires channel state information (CSI) about only O(1) users.