On the achievable outage probability of opportunistic relaying with decode-and-forward

Based on decode-and-forward strategy, we investigate the achievable outage probability of opportunistic relaying, in which there is a single source-destination transmission pair with the help of one of multiple relays. In two-hop scenario, based on adaptive decode-and forward strategy, the achievable diversity-multiplexing tradeoff with the knowledge of channel state amplitudes is analyzed. We show that opportunistic relaying has the same diversity-multiplexing tradeoff as the relaying with distributed space-time coding. We then present the expression in a closed form and find a suboptimal power allocation for the achievable outage probability of opportunistic relaying with decode-and-forward. Simulation results are provided to demonstrate the validity of our analysis and the applicability of the optimum results to select a single ´good´ relay.