THP-UO Algorithm for Multi-User mmWave MIMO Systems

This paper presents an enhanced nonlinear hybrid Tomlinson-Harashima precoding method based on user ordering for millimeter wave (mmWave) massive multi-user mutiple-input multiple-out (MU-MIMO) systems, named as THP-UO algorithm. In the proposed method, making use of the fact that the performance of THP strongly depends on the ordering of precoding symbols, the enhanced THP solution is derived via the minimum mean square error (MMSE) criterion, which can obtain an optimal ordering of precoding symbols by rearranging the user ordering. Then, a digital precoding matrix can be given by THP method directly. It can further eliminate the influence of inter-user interference. Simulation results verify that the proposed hybrid THP-UO algorithm can reduce the bit error rate (BER) effectively, which is closer to the performance of the fully digital precoder than the previous algorithms.