Performance analysis of incremental-relaying cooperative-diversity networks over Rayleigh fading channels

Cooperative-diversity has recently been proposed as an efficient technique to form virtual antenna arrays without using collocated multiple antennas at the transmitters or receivers. Cooperative-diversity networks use the neighbour nodes to assist the source by sending the source information to the destination for achieving spatial diversity. Regular cooperative-diversity networks make an inefficient use of the channels because relays forward the source signal to the destination every time regardless of the channel conditions. Incremental-relaying cooperative-diversity has been proposed to save the channels by restricting the relaying process to the bad channel conditions only. Incremental-relaying cooperative-diversity networks exploit limited feedback from the destination terminal, for example, a single bit indicating the success or failure of the direct transmission. If the destination provides a negative acknowledgment via feedback, in this case only, the relay retransmits the source signal in an attempt to exploit spatial diversity by combining the signals received at the destination from the source and the relay. In this study, the authors study the end-to-end performance of un-coded incremental-relaying cooperative-diversity networks using decode-and-forward and amplify-and-forward relaying over independent non-identical Rayleigh fading channels. Closed-form expressions for the bit error rate, the signal-to-noise ratio (SNR) outage probability and average achievable rate are determined. Results show that the un-coded incremental-relaying cooperative-diversity can achieve the maximum possible diversity, compared with the regular cooperative-diversity networks, with higher channel utilisation.