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Physical Layer Security of a Multiantenna-Based CR Network With Single and Multiple Primary Users

In this paper, we present a method of utilizing channel diversity to improve the secrecy outage probability and the intercept probability in a cognitive radio (CR) network. With the presence of channel diversity, an intended receiver can achieve a relatively better secrecy outage probability and intercept probability. We consider a CR network in which a single antenna, which maximizes the secrecy capacity, is selected at the CR transmitter. To demonstrate the advantages of our proposed framework, we derive new exact closed-form expressions for the secrecy outage probability and the intercept probability of the secondary network in Rayleigh fading. The positive impact of the number of receive antennas and the negative impact of the number of primary users on the secondary network are shown. The derived secrecy outage probability is found to be in precise agreement with simulation results. The numerical results strongly support our conclusion that maximal-ratio combining of channel diversity can enhance the physical layer security of a multiantenna based CR network. Furthermore, the numerical results reveal the impact of the primary network on the secondary network in the presence of a multiantenna wiretap channel.