Fuzzy Relay Selection Scheme for a Cognitive Cooperative Network

We propose a relay selection scheme based on fuzzy logic for a cognitive cooperative network. Our goal is to maximize the throughput of the secondary network while minimizing the interference of the selected relay on the primary network. The instantaneous channel state information (CSI) between the relays and the primary destination, and between the relays and the secondary destination are used as inputs to the fuzzy logic- based scheme, whose output is a relay selection degree, which assumes values between zero and one. Then, each relay waits for a time inversely proportional to this degree before transmitting; thus, the relay with the largest degree is the relay selected to transmit. Monte Carlo simulations are carried out to evaluate the throughput and the average interference level of the proposed scheme. Our results show that the proposed scheme has lower interference on the primary destination than other schemes based solely on the CSI between the relay and the secondary destination, with the same performance in terms of throughput.