Performance analysis of cognitive cooperative communication system based on optimal relay selection scheme

Since the electromagnetic spectrum resource is becoming more and more scarce, a new communication scheme is proposed for the cognitive cooperative system. In this scheme, to avoid harmful interference with primary users, the transmit power of the secondary source and relays are limited with respect to the interference power constraints at primary users and coefficients of fading channels. Moreover, the optimal relay selection scheme is exploited to further enhance the system performance. Based on the closed-form distribution function of the end-to-end signal-to-noise ratio obtained herein, the outage probability of the system under study is analytically investigated. Then we compare the performance in terms of outage probability of the use of fixed transmit power (FTP) and adaptive transmit power (ATP). Our results show that system performance is dominated by the quantity of the relays and the power constraints. In addition, the outage performance of the system with ATP is better than the system with FTP, especially at the large SNR district. However, the use of FTP requires less signaling overhead than the use of ATP. Finally, all analytical results are exhibited and corroborated by simulation results. © 2014 Engineering and Technology Publishing.