Switch-and-stay Combing for Two-way Relay Networks with Multiple Amplify-and-forward Relays

This paper considers a two-phase two-way relay network (TWRN) with two sources and multiple amplify-and-forward (AF) relays, where the direct link between the sources exists and one best relay is chosen for data communication to maximize the minimum signal-to-noise ratio (SNR) of bidirectional communication. To efficiently exploit the direct link within two phases, a switch-and-stay combining (SSC) protocol is employed. In SSC, one branch out of the relay and direct branches is activated for data communication, and the branch switching occurs when the end-to-end SNRs fall below the given thresholds. We analyze the system performances over the independent but not necessarily identically distributed (i.n.i.d.) Rayleigh fading channels, by deriving lower bounds and asymptotic expressions with high SNR for the outage probability and bit error rate (BER). It is shown that SSC can preserve the same spectral efficiency as analog network coding (ANC), while can concurrently achieve the full diversity order as the optimal selection (OS) with less implementation complexity. Numerical and simulation results verify the proposed studies.