Outage analysis for adaptive two-way relaying

This paper analyzes the outage performance of cooperative protocols for the two-way relaying model in which a halfduplex relay assists in the bi-directional communications of two terminals. We first define the outage events of conventional nonadaptive Amplify-and-Forward (AF) and Decode-and-Forward (DF) two-way relaying protocols and derive closed form results for their respective outage probabilities. Then we propose a simple adaptive protocol which switches between AF and DF depending on the number of data streams successfully decoded at the relay. We derive the outage probability for this adaptive scheme in closed form and show that it outperforms the nonadaptive schemes. It is noted that the closed form results are applicable to arbitrary channel gains between terminals.