Physical layer network coding using THP for Bi-directional MIMO relay systems

Bi-directional relaying has been demonstrated to raise transmission throughput intensively as large as twice in throughput by applying physical layer network coding (PNC) when a pair of terminals exchange information via relay. With the aim to enhance the performance of relay system based on decode-and-amplify (DF) strategy, we propose a PNC scheme using Tomlinson-Harashima precoding (THP). Assuming the same broadcast scheme, our proposed scheme shows better performance than conventional linear precoding scheme. To reduce the transmission power without increasing bit error rate (BER), we further introduce a power controlling (PC) structure. It is proved that the transmission power and BER can both be reduced with the power controlling method.