Outage minimization by opportunistic cooperation

We consider a wireless relay network where communication is constrained by delay and average power limitations. We assume that partial channel state information is available at the transmitters while the receivers have the perfect channel state information, and consider the system performance in terms of outage probability. We propose an opportunistic user cooperation protocol that utilizes the channel state information to decide when and how to cooperate. We show that compared to fixed type cooperation schemes, our protocol improves the outage performance significantly and performs very close to the half-duplex lower bound while reducing the resources used by the relay.