Performance Analysis of SNR-Based Decode-and-Forward Opportunistic Relaying in the Presence of Cochannel Interference

Opportunistic relaying (OR) for cooperative communications has been proposed as a technique to provide remarkable gains in multiple-relay cooperative networks. In this paper, we study the effect of cochannel interference (CCI) in the decode-and-forward (DF) OR scheme under independent but not necessarily identically distributed (i.n.i.d) Rayleigh fading channels. In particular, we consider the OR scheme with a signal-to-noise ratio (SNR)-based selection criterion and with the destination-performing maximal ratio combining of the signals from the source and the best relay. We derive approximate but tight closed-form expressions for the outage probability (OP) of the SNR-based OR in the presence of CCI. Moreover, we investigate the asymptotic behavior of the OP of the SNR-based OR. The asymptotic OP for OR with a signal-to-interference-plus-noise ratio (SINR)-based selection criterion is also provided. We examine the diversity orders and coding gains of both criteria under CCI. The result shows that the SNR-based OR is more susceptible to interference at the relays than interference at the destination. We further analytically compare the SNR- and the SINR-based OR schemes. Finally, to verify the analytical results, Monte Carlo simulations are performed, in which more benefits can be gained by using the SINR-based OR when more relays are used.