Tomlinson-Harashima Precoding in Multiuser MIMO Systems with Imperfect Channel State Information

In this paper, the investigation of Tomlinson-Harashima precoding (THP) in downlink multiuser multiple- input multiple-output (MIMO) systems with imperfect channel state information (CSI) is carried out, including two basic structures according to the positions of the diagonal weighted filter: decentralized at the receivers or centralized at the transmitter, which are named as dTHP or cTHP, respectively. The interference power in layers caused by imperfect CSI is first derived, then the comparison between these two THP structures and the linear zero-forcing (ZF) precoding is performed, in terms of interference power and system capacity. Moreover, the independence of the interference powers among layers is presented. Simulation results indicate that with imperfect CSI, THP leads to smaller interference power than linear-ZF, and dTHP leads to larger system capacity than cTHP and linear-ZF.