Robust Tomlinson-Harashima Precoder Design with Random Vector Quantization in MIMO Systems

In this letter, we propose a robust design for a two-stage Tomlinson- Harashima precoder (THP) multiple-input multiple-output (MIMO) system, where the THP cascaded with a unitary precoder is deployed at the transmitter and a linear minimum mean-square error decoder is adopted at the receiver. With the random vector quantization (RVQ) feedback scheme, only the channel direction information (CDI) is quantized and fed back to the transmitter. Applying the THP directly at the transmitter will cause unavoidable interference at the destination due to the quantization error. We herein design a robust THP with the minimum mean-squared error (MMSE) criterion by taking the quantization error into account to mitigate the effect of the quantization error. Simulation results show that the proposed robust THP scheme provides the better performance compared to the non-robust one.