Performance evaluation of amplify-and-forward relaying cooperative vehicular networks under physical layer security

In this paper, we address the physical layer security of a cooperative vehicular network in the presence of a passive eavesdropper vehicle, where the communication from a fixed source node to a fixed destination node is assisted by an amplify-and-forward relay vehicle and by direct link, in two transmission phases. Based on the security of the first transmission phase, we consider two scenarios for the cooperative vehicular networks. In Scenario I, the first phase is secure (ie, the direct link between source and eavesdropper is not available) and the eavesdropping occurs only in the second phase. In Scenario II, the first phase is not secure (ie, the direct link between source and eavesdropper is present) and the eavesdropping occurs during both the first and second phases. We assume that source-to-destination, source-to-relay vehicle, relay vehicle-to-destination, and source-to-eavesdropper vehicle channels are modeled as Rayleigh fading, whereas the channel between relay and eavesdropper vehicles is modeled by double-Rayleigh fading. Under such channel modeling, we deduce the new tight closed-form expressions for the secrecy outage probability (SOP) under both Scenario I and Scenario II. We also investigate the effective secrecy diversity order in the high main-to-eavesdropper ratio (MER) regime. The numerical and simulation results corroborate our theoretical analysis and findings and show the occurrence condition for SOP floor phenomenon and influences of channel conditions and relay and eavesdropper locations on the SOP performance. Our results also reveal that the presence of source-to-eavesdropper link has significant impact on the SOP performance and relay location.