Opportunistic relaying with time-division broadcast in bidirectional cooperative networks

We propose a reactive opportunistic relaying (OR) scheme for time-division broadcast (R-TDBC) in a bidirectional cooperative network. In the proposed R-TDBC, a subset of relays that reliably decode both signals from the sources is determined reactively after two source-transmissions; then a single relay among the determined set is selected by maximizing the achievable rate of the broadcast phase. A somewhat surprising result is that the proposed R-TDBC achieves identical outage performance as its proactive counterpart in bidirectional cooperative networks with the direct link. We then derive the exact outage probability, tight closed-form bounds, and the diversity-multiplexing tradeoff (DMT) for the R-TDBC.