Covert Communication in Integrated Satellite Aerial Terrestrial Networks: A NOMA-Enhanced Framework With Practical Constraints

Abstract

Integrated satellite aerial terrestrial networks (ISATNs) are characterized by their wide-area coverage, which, while enabling massive connectivity, also renders the network more vulnerable to eavesdropping attacks. This inherent security threat necessitates the design of covert communication (CC) schemes to safeguard transmission privacy. Meanwhile, the limited spectrum resource severely restricts the number of accessible users. To tackle this challenge, this paper investigates CC enhanced by non-orthogonal multiple access (NOMA) under practical system imperfections, including hardware impairments (HIs) and channel estimation errors (CEEs). Considering the wide coverage of the satellite beams and the presence of multiple aerial nodes, a threshold-based link selection scheme is proposed to balance system performance and complexity. Closed-form and asymptotic expressions for the detection error probability (DEP), covert outage probability (COP), and the covert transmission rate (CTR) are derived and verified through the Monte Carlo (MC) simulations.