Full Diversity Physical-Layer Network Coding in Two-Way Relay Channels With Multiple Antennas

This paper studies a two-way relay channel where two single-antenna users exchange messages via a relay with K antennas. A new physical-layer network coding (PNC) method is proposed, referred to as channel-quantized PNC (CQ-PNC), that can achieve full diversity gain of K. The proposed method converts K received signals at the relay into two signals by a QR decomposition. The first one is a weighted summation of the two users´ messages and the second one is a scaled version of one user´s message. Then, the first signal is quantized at the relay by using the channel coefficient and the quantization error is cancelled by using the side information of the second signal. Finally, a Gaussian-integer weighted summation of the two users´ messages is obtained, mapped to network codeword, and then broadcast to the two users. It is proved that the proposed CQ-PNC can achieve the full diversity gain of K with receiver side channel information, low computational complexity and symbol level synchronization. Simulation results demonstrate that the proposed method obtains optimum performance results with negligible gap.