Sum Capacity of Opportunistic Scheduling for Multiuser MIMO Systems with Linear Receivers

We analyze the sum capacity achieved by linear receivers in a multiple-input multiple-output broadcast channel. We consider a simple and practical opportunistic scheduling algorithm, based on the signal to interference noise ratio (SINR) feedback from each user. Each transmit antenna sends data to a particular user, selected based on SINR. Under this scheduling scheme, we derive new accurate approximations for the sum capacity, for the cases of maximum ratio combining, zero forcing, and minimum mean-squared error receivers. We also derive capacity scaling laws, which reveal that the capacity of all three linear receivers converge to the same value for a large number of users. Our results are confirmed through comparison with Monte Carlo simulations.