On the user selection for MIMO broadcast channels

In this paper, we consider a downlink communication system, in which a base station (BS) equipped with M antennas communicates with N users each equipped with K receive antennas. We propose an efficient suboptimum algorithm for selecting a set of users in order to maximize the sum-rate throughput of the system. For the asymptotic case of N -> infinity, it is shown that by using a very simple precoding scheme of zero-forcing beam-forming, the optimum sum-rate which behaves like M log log N can be achieved. The complexity of our algorithm is investigated in terms of the required amount of feedback from the users to the base station, as well as the number of searches required for selecting the users. It is shown that the proposed method is capable of achieving a large portion of the sum-rate capacity, with a very low complexity.