Performance analysis of spectrally efficient amplify-and-forward opportunistic relaying scheme for adaptive cooperative wireless systems

In this paper, we propose an adaptive amplify-and-forward (AF) relaying scheme that selects the best relay among the available relay nodes opportunistically to cooperate with a source node for improvement of the spectral efficiency. This improvement can be achieved by introducing a policy that gives the useful cooperative regions and defines a switching threshold signal-to-noise ratio that guarantees the bit error rate (BER) of cooperative transmission is below the target. We model all links as independent non-identically distributed Rayleigh fading channels. We then derive closed-form expressions for the average spectral efficiency, average BER, and outage probability when an upper bound for the signal-to-noise ratio of the end-to-end relay path is applied and adaptive discrete rate is considered. Numerical and simulation results show that the proposed scheme, compared with the outage-based AF incremental relaying, AF fixed relaying, and the conventional direct transmission, can achieve the maximum average spectral efficiency while maintaining the average BER and outage probability. Copyright (c) 2013 John Wiley & Sons, Ltd.