Limited Feedback Scheme for Tomlinson-Harashima Precoding in Close-Loop MIMO Systems

In this paper, a novel limited feedback scheme, based on scalar quantization, is proposed for Tomlinson-Harashima precoding (THP) in multi-user multiple-input multiple-output (MU-MIMO) systems. Due to the sensitivity of THP to erroneous channel state information (CSI), the conventional codebook-based channel vector quantization (CVQ) is no longer suitable since its complexity grows exponentially with the increase of feedback bits. This paper combines the optimum Gaussian scalar quantization (GSQ) with THP to improve the accuracy of CSI for the flat Rayleigh fading channel. Simulation results show that the GSQ-THP scheme provides a very high capacity and a good bit error rate (BER) performance.