Relay selection with time-division broadcast in bidirectional cooperative networks

We study relay selection (RS) for time-division broadcast (TDBC) in a bidirectional network consisting of two different end-sources and multiple relays. By modifying the well-known proactive RS scheme valid only for unidirectional cooperative networks, we propose a proactive RS with TDBC (P-TDBC) for bidirectional cooperative networks. In the P-TDBC scheme, a single best relay is selected proactively before two consecutive source-transmissions by maximizing the bottleneck of the end-to-end maximal achievable rates in both directions. We then derive the exact outage probability of P-TDBC in closed-form for E_s ≤ E_r, and in a single-integral form for E_s >; E_r, where E_s and E_r denote the transmission powers at each end-source and the selected relay, respectively. Moreover, we derive very tight closed-form upper and lower bounds on the outage probability for E_s >; E_r. Finally, we study the diversity-multiplexing tradeoff (DMT) and show that the P-TDBC scheme achieves full diversity.