Distributed Two-Way Switch and Stay Combining with a Single Amplify-and-Forward Relay

This letter considers a two-phase two-way relay network (TWRN) consisting of two sources and a single amplify-and-forward (AF) relay. In order to efficiently exploit the direct link between sources for achieving full diversity order, we propose to utilize a distributed switch and stay combining (DSSC) in the two-phase TWRN. In DSSC, one branch out of the direct and relay branches is activated, and the branch switching occurs when the minimum end-to-end signal-to-noise ratio (SNR) of bidirectional communication falls below a preset threshold. We analyze the system performance over Rayleigh fading channels, by deriving the lower bounds and asymptotic expressions for the outage probability and symbol error rate (SER). It is shown that the DSSC preserves the same spectral efficiency as pure analogy network coding (ANC) protocol, while can concurrently achieve full diversity order as the optimal selection (OS) with less channel estimation complexity and lower switching rate. Numerical and simulation results demonstrate the proposed studies.