Performance Analysis of Centralized Relay Selection with Unreliable Control Information

The potential of relay selection (RS) has been well appreciated. However if the control channels, conveying information on the selected relay node (RN), are unreliable, the gains of RS diminish. This is because the transmitting RN might not be the one maximizing the employed utility function. Furthermore, more than one of the RNs might end up transmitting, an event that could be performance degrading. It is also likely that no RN transmits, which is very undesirable. In this paper we assume decode-and-forward and present closed form expressions for the outage probability (OP) under Rayleigh fading when two potential RNs are available and the control information related to RS is corrupted by errors. We show that when control channels are unreliable, the OP performance degrades significantly and reaches a floor as the signal-to- noise ratio of the RN-to-destination data channel grows. Furthermore when control channels are very unreliable, suboptimal schemes not requiring control information, like repetition coding, outperform RS.