Outage Behavior of Cooperative Diversity with Relay Selection

Cooperative diversity is a useful technique to increase reliability and throughput of wireless networks. To analyze the performance gain from cooperative diversity, outage capacity is an important figure of merit that captures the inherent diversity-multiplexing trade-off in cooperative diversity schemes. In this paper we derive the outage capacity for several cooperative diversity schemes in decode-and-forward relay networks with a finite number of relay nodes. The obtained expressions are simple and applicable to arbitrary network topologies and signal-to-noise ratios in Rayleigh fading channels. The analysis shows that there exists a signal-to-noise ratio threshold, below which some cooperative diversity schemes are better than direct communication. We propose a new diversity scheme, which, compared to the conventional counterpart, offers improved performance and requires protocol overhead.