A New THP Precoding Scheme with Effective Channel Optimization

Recently there is a trend to use Tomlinson-Harashima preceding (THP) to achieve better performance with full channel state information known at transmit side. In general, performance of THP precoding is governed by the the minimum absolute diagonal elements of the triangle matrix which is derived from QR decomposition to the channel matrix. In this paper we propose a new THP precoding scheme in which codebook based precoding is applied to optimize the effective channel after THP precoding with the aim of maximizing the minimum absolute diagonal elements of the triangle matrix. As a result, about 4 to 8 dB gains are obtained by employing codebooks of different sizes. The merits of the proposed scheme are low complexity, flexible tradeoff between complexity and performance by employing codebook with different sizes, and friendly to hardware implementation because of its fixed complexity. The theory analysis on the BER performance of THP precoding scheme is provided in this paper which is close to the simulation results. Numerical simulation results verify our conclusions.