Optimization of Tomlinson-Harashima Precoding for Joint Suppression of Interference and Power Loss in MU-MIMO Downlinks

In 5G mobile communication systems, downlink MU-MIMO (Multi-User Multiple-Input Multiple-Output) can schedule multiple users at the same time-frequency resources, which can increase the throughput significantly. Interference between users is the key factor restricting system performance. Further, precoding is one of the effective methods to solve the interference. THP (Tomlinson-Harashima Precoding) is a type of non-linear precoding algorithm with good performance and low complexity. Due to the modulo and feedback filtering operations in THP, the interference between users will increase, and the transmitted power efficiency will reduce. In this paper, a THP optimization algorithm is proposed. By using the lattice reduction algorithm and adjusting the interference of complex signals, the interference among the users is reduced, while the power efficiency is increased. According to the simulation results, the BER performance of the proposed algorithm is increased by 2dB and power loss is reduced by 24% compared with those of traditional THP.