Decode-and-forward two-way relaying protocol with one retransmission

This paper investigates the decode-and-forward two-way relaying channel without direct link and proposes a protocol based on the physical-layer network coding (PNC) protocol. The proposed protocol (termed ORT) introduces one retransmission into PNC, aiming at enhancing its outage performance. To manifest the merits of ORT, we compare it with PNC and the time-division broadcast (TDBC) protocol, in terms of outage performance, expected rate, and diversity-multiplexing tradeoff (DMT). Firstly, we derive the outage probability of the three protocols and then the expected rate. Secondly, asymptotic analysis is conducted to shed light on the diversity and coding gains. Finally, the DMT is obtained for the three protocols. The numerical results reveal the following: (i) that ORT performs better than PNC in both outage and expected rate performance when the nodes transmit with different powers. However, it has the same DMT performance with PNC; (ii) that ORT possesses improved DMT performance over TDBC whereas its expected rate is only better than the latter at medium to high signal-to-noise ratio. Copyright (c) 2012 John Wiley & Sons, Ltd.