Joint Relay Selection and Network Coding Using Decode-and-Forward Protocol in Two-Way Relay Channels

In this paper, we analyze the bit error rate (BER) performance of a single relay selection with network coding (S-RS-NC) scheme in two-way relay channels. In this scheme, two source nodes first broadcast their information to the relays sequentially. A single relay which optimizes the system performance is selected. The selected relay decodes the received signals from two sources, performs network coding on two symbol estimates and then forwards them to two source nodes. Equivalent signal-to-noise-ratio (SNR) of the whole source-relay-destination link is analyzed and its high SNR approximation is derived. Closed-form BER expressions are then derived and the results are verified through Monte-Carlo simulations which show that the derived analytical expressions offer a tight bound for the average BER. It is shown that this S-RS-NC scheme can achieve a full diversity order as if all relays were used. Simulation results show that the S-RS-NC scheme can bring considerable gains over the all-participation relaying scheme when the source transmission power is larger than or equal to the relay transmission power. However, when the relay transmission power is greater than the source power, the single relay selection scheme could be inferior to the all-participation relaying scheme. This is quite different from the conventional relay selection scheme in one way relay network, where the relay selection always outperforms the all participation relaying scheme.