On the performance of cognitive relay networks with cooperative spectrum sensing

In this paper, with multiple relays available for cooperative sensing and data transmission, we investigate the performance of primary user (PU) and secondary user (SU) in the hybrid interweave and underlay cognitive relay networks. For the cooperative sensing phase, all the relays independently sense the spectrum with energy detection, and hard fusion is deployed to achieve the final sensing result by a distributed manner. Subsequently, for the data transmission phase, when cooperative sensing results assume there exists a spectrum hole, the SU transmitter and the selected relay transmits the message with maximum transmission power. Otherwise, to guarantee the PU´s transmission quality, the SU transmits the message under a peak power constraint at the PU receiver. It is noted that the selected relay can decode the SU´s message correctly and has the largest signal to noise ratio (SNR) or signal to interference and noise ratio (SINR) at the SU receiver. In this case, considering the interference caused by the PU, we derive the outage probability of SU under Rayleigh fading channels. In addition, the impact of cooperative sensing on the PU are discussed. Finally, simulation results verify our analysis.