Relay selection on dual hop AF MIMO with OSTBC over asymmetric fading channels

This paper investigates optimal relay selection schemes for orthogonal space-time block coded multiple-input multiple-output system with non-coherent amplify-and-forward relays, where channel state information is not available at the source and relays. The source-relay and relay-destination channels undergo Rayleigh and Rician fading, respectively. Two possible relay selection schemes are proposed, and both are statistically characterised by deriving exact closed form expression for the cumulative distribution function and probability density function of the instantaneous signal-to-noise ratio (SNR) at the destination. In the first relay selection method, maximizing instantaneous SNR at the destination is considered to select the best relay. In the second scheme, maximizing relay-destination channel is considered. The derived statistical results are used to analyse the performance of the system with outage probability, average bit error rate and ergodic capacity. Finally, we compare both relay selection schemes with respect to the relay pool size and Rician factor.