Intercept outage probability analysis of cognitive relay networks in presence of eavesdropping attack

In this paper, we study the physical-layer security of amplify-and-forward relaying networks under a spectrum-sharing mechanism over independent non-identically distributed Rayleigh fading channels. Relay selection is presented to select the best relay, which can guarantee the security performance by minimizing the received signal-to-noise ratio at the eavesdropper. In order to guarantee the quality-of-service of primary networks, both the maximum tolerable peak interference power at the primary users and maximum allowable transmit power at secondary users are considered. Closed-form lower and upper bounds as well as asymptotic expressions for the intercept outage probability (OP) are derived. From the asymptotic expressions, it can be observed that the diversity order of intercept OP equals to two. Our analysis results are validated by Monte-Carlo simulation.