On the Secrecy Performance of Cooperative Cognitive Vehicular Relay Networks

In this paper, we study the secrecy performance of underlay cooperative cognitive relaying network, where a secondary source communicates with a secondary destination with the cooperation of an amplify-and-forward (AF) secondary relay in the presence of a passive eavesdropper, taking into consideration the interference from primary user (PU). We assume that the nodes in the secondary network are mobile, whereas the PU is a fixed infrastructure node. Therefore, we model the channels for mobile-to-mobile links as double-Rayleigh fading, while the channels between mobile-to-fixed links are modeled as Rayleigh fading. Considering such a realistic scenario, in particular, we derive a tight lower bound expression of secrecy outage probability (SOP) in closed-form, whereas an important asymptotic SOP expression is presented in the high signal-to-noise ratio (SNR) regime. The asymptotic results reveal that the presence of eavesdropper causes irreducible error floors in the SOP curves at high SNR and hence reduces the secrecy diversity order to zero. Finally, numerical and simulation results demonstrate the correctness of our analytical findings.