In this paper, we derive PDF and CDF expressions for the end-to-end SNR of an opportunistic relaying amplify-and-forward (AF) cooperative diversity over independent and non-identically distributed (i.ni.d.) Rayleigh fading links with outdated channel state information (CSI). Based on those expressions, we find the analytical capacity and outage probability for four adaptive transmissions techniques, namely, optimal power and rate adaptation (OPRA), constant power with optimal rate adaptation (ORA), channel inversion with fixed rate (CIFR) and truncated channel inversion with fixed rate (TIFR). Numerical evaluations results are also presented showing the impact of outdated CSI and i.ni.d. links on the performance of each adaptive technique in AF opportunistic relaying systems. In particular, it is shown that among the considered techniques CIFR technique is the most sensitive to the outdated CSI and optimal power allocation doesn't significantly improve the performance as the number of relays increases.
Published December 2012 , 16 pages