Secrecy Outage Probability of Minimum Relay Selection in Multiple Eavesdroppers DF Cognitive Radio Networks

In this paper, we investigate the secrecy outage probability in a dual-hop decode-and-forward (DF) secondary cognitive radio network, which is equipped with one source, one destination, multiple eavesdroppers (EAVs) and multirelay. The direct links from the source to the destination and the EAVs are considered because of the moderate shadowing environment. All channels experience the Rayleigh fading. To analyse the system performance, we consider the minimum relay selection, where the most annoying eavesdropper is selected first according to the maximum signal-to-noise ratio (SNR) of the direct links from the source to the EAVs. Then, the best relay is selected according to the minimum SNR from the selected EAV to relays. The selection combining (SC) technique is also employed in our system. The circumstance that the relays can or not deliver the information is considered. We evaluate the system performance through the closed-form accurate and asymptotic secrecy outage probability. The simulation results are also derived by Monte Carlo Simulations to verify the numerical results.