Secrecy outage probability of cognitive decode-and-forward relay networks

This paper investigates the secrecy performance of cognitive decode-and-forward (DF) relay networks with multiple primary users (PUs) receivers, one secondary user (SU) source, multiple SU relays, one SU destination and one SU eaves-dropper over Nakagami-m fading channels. The opportunistic relay selection transmission strategy is employed to enhance the security performance. We also consider the joint impact of maximum transmit power at secondary source and relays and peak interference temperature at PU receivers. To analyze the secrecy performance of this network, the exact expression of secrecy outage probability (SOP) is derived in closed form. Furthermore, the asymptotic closed-form expressions of SOP are derived, explicitly showing the secrecy diversity order and the secrecy array gain. Results show that the primary network has a negative impact on the SOP, and the number of PUs only affect the secrecy array gain but not the secrecy diversity order, and the SOP improves with increasing the number of secondary relays and the Nakagami fading parameters of the legitimate channel.