On the Secrecy Outage Performance of Cooperative NOMA-Assisted Hybrid Satellite-Terrestrial Networks

Abstract

This paper investigates the secrecy outage performance of a downlink cooperative nonorthogonal multiple access- (NOMA-) assisted hybrid satellite-terrestrial network, where a satellite source communicates with two terrestrial users based on NOMA, in the presence of a terrestrial eavesdropper. We assume that there is no direct link between the satellite source and the far terrestrial user, and the near terrestrial user acts as a relay to forward the information to the far terrestrial user. The near user is assumed to support both half-duplex mode and the full-duplex mode for information relaying. We derive the closed-form exact expressions for the secrecy outage probability (SOP) of the near user, as well as the closed-form approximate expressions for the SOP of the far user based on the Gaussian-Chebyshev quadrature. Theoretical results are validated by conducting simulations. The impacts of various system parameters on the performance comparison between the half-duplex mode and full-duplex mode are investigated. Particularly, the full-duplex mode is shown to outperform the half-duplex mode when the received signal-to-noise ratio (SNR) at the near user is low or the residual self-interference is low.