Robust transceiver with Tomlinson-Harashima precoding for QRD-based multiuser MIMO relaying systems

A robust transceiver design with Tomlinson-Harashima precoding (THP) for QR decomposition (QRD)-based multiuser multiple-input multiple-output (MU-MIMO) relaying systems is proposed, which exploits the relationship between QRD and Gram-Schmidt orthogonalization (GSO) to jointly optimize the transmit precoder and receive beamforming vectors of users. Then we propose a correlation-based approach which leads to a significant reduction of forward overhead information from the relay to all MUs. Finally to reduce the computational complexity, a "Best-Last" based user selection scheme is proposed which has a performance close to the optimal global selection approach. Numerical results are presented to demonstrate the advantages of the proposed robust schemes.