Channel imperfection effects on THP performance in a slowly time varying MIMO channels

Tomlinson-Harashima Precoding (THP) is an attractive solution for a scenario where the transmission system employs multiple transmit antenna and multiple users with single antenna at the receiver. In spite of THP´s good performance, it is very sensitive to erroneous Channel State Information (CSI). In this paper, the effect of channel imperfection on THP performance in a downlink scenario is investigated. An analytical method to calculate an upper bound of sum capacity for (Zero Forcing) ZF-THP in a slowly time varying fading channel is developed. Moreover, an approximate bound for capacity loss is determined that can be used for practical system design in an imperfect CSI scenario.