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.