Protecting Terrestrial Networks in Cognitive Satellite-Terrestrial Networks: A NOMA-Based Protocol

Fifth-generation (5G) standards have spurred the integration of satellite networks to enhance communication capabilities, yet harmonizing spectrum sharing between ter-restrial and satellite domains remains challenging. cognitive satellite-terrestrial networks (CSTNs) address these challenges by leveraging collaboration between terrestrial base stations (tBSs) and satellite base stations (sBSs). This paper explores a novel non-orthogonal multiple access (NOMA)-based CSTN paradigm where the tBS serves as the primary network (PN) and the sBS as the secondary network (SN). The proposed NOMA-based protocol aims to enhance PN protection and overall network capacity. Through Monte-Carlo simulations, this study derives the ergodic capacity and ergodic sum capacity of the protocol. Results indicate effective protection of PN ergodic capacity by NOMA-CSTN, albeit at the expense of compromised SN ergodic capacity compared to orthogonal multiple access (OMA)-based CSTN protocols.