Joint Relay Selection and Network Coding for Error-Prone Two-Way Decode-and-Forward Relay Networks
Qimin You, Yonghui Li, Zhuo Chen · IEEE Transactions on Communications · 2014
In a two-way relay network (TWRN), the optimal joint relay selection (RS) and network coding (NC) (O-RS-NC) scheme, which searches all the relay combinations to select a best relay subset, requires high computational complexity and significant amount of feedback. To address this issue, two joint RS and NC (RS-NC) schemes, referred to as a joint single RS and NC (S-RS-NC) and a joint dual RS and NC (D-RS-NC), are proposed based on decode-and-forward (DF) protocol for error-prone TWRNs. Specifically, for the S-RS-NC scheme, a single relay is selected to minimize the sum bit error rate (BER) of the TWRN. The S-RS-NC scheme is simple to implement, but it suffers from a relatively large signal-to-noise ratio (SNR) loss compared to the O-RS-NC scheme. To reduce the SNR loss, a D-RS-NC scheme is proposed. In the D-RS-NC scheme, one or two relays are selected to minimize the sum BER of the network. Because the source and relay transmission powers (ESand ER) have different impacts on the equivalent SNR of the TWRN, the RS criterion is designed based on different ratios of ESand ER. BER lower-bounds for these schemes are derived and verified by simulations to be tight asymptotically. Both analytical and simulation results show that the proposed RS-NC schemes are superior to the conventional RS without NC scheme when 2ES>ER. In most practical applications, for example, a wireless sensor network, all the nodes transmit at the same power, where the proposed RS-NC schemes perform better than the conventional RS without NC scheme.