Optimal Relay Selection for Outdated CSI

Consider the scenario of relay selection in an environment where the channel estimates are outdated, yet their reliability is known. For this scenario, we propose the optimal relay selection policy, in a minimum outage probability sense. We show that, if the reliabilities of the channel estimates are dissimilar across the relays, this policy offers a noteworthy improvement in terms of array gain, when compared to conventional selection policies. Analytical outage probability expressions are provided, which are corroborated by simulations.