User Assignment for MIMO-OFDM Systems with Multiuser Linear Precoding

Recent work has developed single-carrier linear precoding for the multiuser downlink for multiple-input multiple-output (MIMO) systems. This paper addresses the problem of user selection in orthogonal frequency division multiplexing (OFDM) based MIMO systems using such multiuser precoding. We propose an effective scheme to assign multiple users, chosen from a larger set, to individual subcarriers. The scheme is developed in the context of a previously proposed single-carrier MIMO linear precoding scheme to minimize the sum mean squared error (SMSE) over multiple users. We further simplify the implementation of the proposed algorithm exploiting the inherent channel correlation between adjacent OFDM subcarriers. Simulations show that the proposed user assignment algorithm exhibits near optimal performance and that reducing the computational load causes minimal performance loss.