Physical Layer Secrecy of NOMA-Based Hybrid Satellite-Terrestrial Relay Networks

In this paper, we investigate the physical layer security of a non-orthogonal multiple access (NOMA) based downlink hybrid satellite-terrestrial relay network where the satellite communicates with terrestrial NOMA users in the presence of an eavesdropper via an amplify-and-forward relay. To analyze the secrecy performance of this network, we derive new closed-form expressions of secrecy outage probability (SOP) and the probability of positive secrecy capacity by adopting shadowed-Rician fading for the satellite link and Nakagami-m fading for terrestrial links. To get more insights, we further derive the closed-form expression for asymptotic SOP and illustrate the behavior of SOP at high signal-to-noise ratio regime. The analytical results are corroborated through Monte-Carlo simulations.