Optimal User Pairing for Multiuser MIMO

In this paper we show how the capacity of the uplink of a multiuser system can be increased by a scheduling strategy, which pairs the transmission of users in different time/frequency/code slots according to the channel quality. The optimal scheduling strategy is equivalent to a combinatorial optimization problem. We show how this problem can be solved efficiently by using the Hungarian method. We then show that, by using the proposed scheduling scheme, the performance of minimum mean square error detection approaches the one of maximum likelihood detection, as the number of users increases.