On the Performance of Selection Cooperation with Outdated CSI and Channel Estimation Errors

We analyze the effect of feedback delay and channel estimation errors in a decode-and-forward (DF) relay selection scenario. Amongst all the relays that decode the source information correctly, only one relay with the best relay-to-destination (R → D) channel quality is selected. More specifically, the destination terminal first estimates the relay-destination channel state information (CSI) and then sends the index of the best relay to the relay terminals via a delayed feedback link. Due to the time varying nature of the underlying channel model, selection is performed based on the old version of the channel estimate. In this paper, we investigate the performance of the underlying selection scheme in terms of outage probability, average symbol error rate (ASER) and average capacity. Through the derivation of an ASER expression and asymptotic diversity order analysis, we show that the presence of feedback delay reduces the asymptotic diversity order to one, while the effect of channel estimation errors reduces it to zero. Finally, simulation results are presented to corroborate the analytical results.