Physical-layer network coding and precoding for end nodes using Alamouti scheme

This paper proposes a novel STBC-based transmit diversity scheme for physical-layer network coding (PNC) aided two-way relay networks, where two end nodes are equipped with two transmit-antenna. To directly decode network-coded signals from the received superimposed signals at the relay, the two end nodes in this proposed system use reciprocal channel state information (CSI) to precode their respective transmitted signals before STC coding. The corresponding maximum a-posterior probability (MAP) and an approximated threshold-decision (TD) decodings are introduced, based on which the relay can remain the same transmit diversity gain in the multiple-access (MA) stage as the conventional STBC-based network-coding (STBC-NC) scheme. Considering BPSK and QPSK used at the end nodes, simulation results illustrate that the proposed STBC-PNC shows symbol error rate (SER) performance no worse than the STBC-NC, and significantly outperforms the single-input-single-output (SISO)-PNC and the previous PNC-aided STBC schemes.