Covert Communications for Energy-Efficient ISTRNs With Opportunistic Scheduling and Cooperative Jamming

Secure transmission as well as green communication has been the focus of research in the wireless networks. In order to secure wireless transmissions, we study covert communications for integrated satellite-terrestrial relay networks (ISTRNs) with multiple deployed relays and public users, where users are used as covert receivers and cooperative jammers. By considering that direct links are unavailable due to the environmental and hostile blocking, the satellite tries to send own covert information to the users via one specific relay. Meanwhile, a warden intends to judge whether covert transmission exists. Thus, a covert opportunistic scheduling scheme with the max-min user selection (MM-COS) is proposed to keep the transmission covert and energy-efficient. Then, the minimum probability of detection errors in each time slot is derived. Further, we obtain the closed-form expressions of outage probability (OP) and effective covert rate (ECR). Besides, a transmit power optimization problem is addressed to obtain the maximum ECR. Finally, numerical results are presented, which illustrate that for this MM-COS scheme, either the introduction of more users or the deployment of more relays can significantly enhance covert performance when their numbers are small, and they each yield similar gains.