nonorthogonal multiple access (NOMA)-aided cognitive satellite aerial terrestrial integrated networks (CSATINs) are considered revolutionary and key technologies for 6G Internet of Things (6G-IoT), offering enhanced connectivity, high spectral efficiency, and broad coverage. In this article, we first establish trustworthy CSATINs with multiple aerial relays, aiming to achieve reliable communication in the presence of an eavesdropper. Then, to enhance the system’s covert performance, we propose an autonomous aerial vehicle (UAV) scheduling scheme. Moreover, based on the established covert system model, we derive the closed-form expressions of detection error probability (DEP), covert outage probability (COP), and effective covert rate (ECR). Particularly, an optimization is proposed to enhance the covert performance of the considered system. Finally, Monte Carlo simulations are given to validate the correctness of the theoretical analysis, demonstrating that the reliability and covertness of the proposed system can be simultaneously enhanced by appropriately adjusting the power allocation coefficients, jamming power, and the transmission power of the satellite and UAVs.

Integrated satellite multiple terrestrial relay network (ISMTRN) is a new network architecture that combines satellite communication with terrestrial communication. It both utilizes the advantages of the two systems and overcomes their shortcomings. However, security issues inevitably arise in the ISMTRN resulting from the broad coverage of the satellite beams and the openness of wireless communication. One of the promising methods to achieve secure transmission is covert communication technology, which has been a hot discussion topic in recent years. In this paper, we investigate the performance of covert communication in the ISMTRN with partial relay selection. Particularly, when the satellite transmits its signal to the user, we consider the scenario that the selected relay opportunistically sends covert information to the destination. Furthermore, the closed-form error detection probability and average covert communication rate are derived. Finally, numerical simulation results are provided to reveal the impact of critical parameters on system covert performance.

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.

We explore the influence of cooperative jamming on covert communication for integrated satellite–terrestrial relay networks (ISTRN) in this article, where one full-duplex relay is utilized to support communications and acts as a jammer to confuse eavesdroppers. A cooperative scheme is first proposed to efficiently achieve covert communication in this specific scenario. Further, the probability of detection error (PDE) is derived. Subsequently, the minimum PDE is calculated using the optimal detection threshold. Moreover, a closed-form expression of outage probability (OP) is acquired to quantify the system’s covert performance. Based on this, we design a power optimization algorithm to enhance the effective covert rate under covertness constraints. Lastly, numerical simulation results are given to verify the efficiency of our cooperative jamming scheme when interrupting the eavesdroppers. Notably, an optimal power allocation factor can be obtained, leading to a higher effective covert rate.

This works investigates the covert performance for the satellite aerial–ground integrated network with imperfect limitations, i.e., channel estimation errors (CEEs), nonideal hardware (NIH) and co-channel interference (CCI). To enhance the covert transmission, an autonomous aerial vehicles is applied to forward the signal from the satellite source to the destination. Particularly, the detection error probability (DEP), outage probability (OP) and the covert transmission rate (CTR) are further studied in the presence of closed-form expressions and asymptotic expressions. Finally, some representative Monte Carlo simulations are proposed to verify our theoretical analysis. Derived from the results, the NIH, the CEEs and the CCI have great impacts on the covert performance. Particularly, when the system is under NIH, a suitable power allocation scheme is needed for the interference to gain the lowest DEP. Moreover, the OP has a lower bound in the case of NIH. What’s more, the CTR also has an upper bound when the system is under NIH. In addition, to have a better covert performance, the channel state information should be accurate enough by allocating much power for the channel estimations. The finding results are essential for the practical system for they can promote the engineering design.

Tocompensate for the insufficient number of visible satellites in global navigation satellite systems (GNSS), an integrated navigation and communication (INAC) network utilizing a relay satellite with rate splitting multiple access (RSMA) is proposed. In this system, an MEO satellite transmits navigation signals to both the geostationary earth orbit (GEO) satellite and ground users. When the MEO satellite is blocked, the GEO relay satellite decodes and forwards (DF) both navigation and communication signals. All information is spread and transmitted using RSMA, where the public stream carries navigation information, and the private stream carries communication data. To further reduce interference between navigation and communication signals, a zero-forcing and maximum ratio transmission (ZF-MRT) precoding is introduced. At the receiver, the navigation signal is first decoded for pseudorange accuracy using a code tracking loop (CTL), and then the communication signal is decoded using successive interference cancellation (SIC). Channel models are first established for both direct links and multi-antenna relay links. Then, signal-to-interference-plus-noise ratio (SINR) expressions under ZF-MRT precoding are derived, from which analytical results for outage probability (OP) and pseudorange accuracy are derived. Simulation results show that the proposed scheme, benefiting from ZF-MRT precoding for enhanced diversity gain, outperforms single-antenna RSMA and NOMA in both OP and positioning accuracy. In addition, increasing transmit power or spreading code length can effectively enhance navigation signals and improve communication reliability, while increasing the Rician factor has a limited effect on positioning accuracy. Finally, despite some loss in spectral efficiency (SE) due to the use of spread spectrum, this network still serves as a valuable reference for the design of future INAC systems.