A Practical Cooperative Diversity Scheme Based on Opportunistic Relaying with Acknowledgement and Random Backoff

By using a single relay with best channel quality for cooperative diversity, opportunistic relaying achieves the same diversity gain as that achieved by more complex space-time coding. However, the failure probability of the best relay selection may become unacceptable when the number of relays increases. We propose a modified practical best relay selection scheme in this paper. The source is required to send an acknowledgement to the best relay, while contending relays will backoff when collision occurs. Simulation results show that the failure probability of relay selection is reduced by 2~3 orders with an extra overhead less than 2%.