An opportunistic-based protocol for bidirectional cooperative networks

In this paper, a new opportunistic source selection (OSS) protocol is studied in bidirectional cooperative networks. Unlike existing protocols, this protocol exploits multiuser nature of the bidirectional cooperative networks and it opportunistically supports two traffic flows based on instantaneous channel conditions. This makes the OSS protocol much more reliable than existing protocols. We derive a lower bound of the outage probability of the OSS protocol. This lower bound is extremely tight and it also indicates that the OSS protocol achieves full diversity order two in a bidirectional cooperative network with two sources and one relay. Then an optimum power allocation scheme is developed for the OSS protocol. This scheme can optimize the outage probability and mutual information of the OSS protocol at the same time.