Symbol error probability of incremental relaying with distributed/centralized relay selection

In this paper, we derive the Symbol Error Probability (SEP) of cooperative systems with incremental relaying and Distributed Relay Selection (DRS). The relays remain idle when the Signal to Noise Ratio (SNR) between the source and destination is larger than T. Otherwise, we activate a relay using DRS. Relay nodes transmit only if their SNR is larger than threshold β. If the SNRs of more than two relays is larger than β, there is a collision and the destination uses only the received signal from the source. If all relays have SNR less than β, no relay is chosen. Threshold β is optimized to yield the lowest SEP at the destination. Our results are compared to centralized relay selection using opportunistic Amplify and Forward (OAF), Partial and Reactive Relay Selection (PRS and RRS). We compare our results to computer simulations for Rayleigh fading channels.