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.