Interference-Limited Two-Way DF Relaying: Symbol-Error-Rate Analysis and Comparison

The average symbol-error-rate (SER) performances for the three-phase two-way relaying (TWR) protocols are analyzed and compared in Rayleigh fading channels, where the terminals and relay are interfered with by a finite number of cochannel interferers. The relay is assumed to operate in the decode-and-forward (DF) mode. Three TWR protocols where the terminals adopt different combining methods on the received signals from a relay link and a direct link are considered, and the tight approximate expressions of average SERs for these protocols are theoretically derived. Based on the analytic results, the SER performances of the three TWR protocols are compared in the interference-limited scenario. The results show that the TWR protocol where the terminals employ selection combining on the received signals from the relay and direct links can achieve good tradeoff between the average SER performance and computational complexity at the terminals. Moreover, we show that the three-phase TWR protocol outperforms the two-phase TWR protocol significantly in SER performance.