ZF-THP Combined with Receive Beamforming for Multi-User MIMO Downlinks

In this paper, a method of Tomlinson-Harashima precoding (THP) combined with receive beamforming for the multi-user MIMO broadcast channel is proposed. When the base station and user terminals all have multiple antennas, each user´s receiver maximizes the system sum rate with receive beamforming, and the base station use THP based on zero forcing criteria to cancel multiuser interferences (MUI). Simulation results show that the proposed method, THP-BF, has better BER performance than traditional THP and some linear precoding methods such as block diagonalization (BD) and zero forcing (ZF). The sum rate of ZF-THP at asymptotically high SNR is computed, and the computation results are consistent with simulation results. Simulation results reveal that ZF-THP has higher sum rate than linear precoding methods (such as ZF and BD) due to its more degrees of freedom of MIMO channels, and that THP-BF also has higher sum rate than traditional THP at low and moderate SNR.