Integrated satellite terrestrial networks (ISTNs) are becoming a hot research topic in recent years due to the capabilities of high quality, high throughput, and seamless coverage. However, the limited spectrum resources are difficult to meet the needs of a large number of users in ISTNs, and the obstacles and shadowing will seriously affect the communication quality of networks. In this regard, cooperative transmission of non-orthogonal multiple access (NOMA)-assisted ISTNs with the help of multiple terrestrial relays are established to enhance the spectrum efficiency and enlarge the transmission coverage. In this paper, we investigate the performance of NOMA-based ISTNs with relay selection and imperfect successive interference cancellation (SIC). Particularly, the partial relay selection (PRS) scheme is used in the considered system to reach the balance of system performance and complexity. Owing to practical constraints, the imperfect SIC is analyzed for the networks. Based on the PRS scheme and imperfect SIC, we obtain the closed-form expressions for the outage probability (OP) and ergodic capacity (EC) of the considered networks. Besides, to get further insights of key system parameters, the asymptotic analysis for the OP is also derived. Finally, numerical and simulation results are presented to validate the correctness of our analytical results.

With the increasing requirements for efficient utilization of satellite resources, both non-orthogonal multiple access (NOMA) scheme and cognitive radio (CR) have been recognized as one of the promising solutions, particularly, for the enhancement of spectrum efficiency. This letter investigates the performance of NOMA-based integrated satellite-terrestrial relay network (ISTRN) in the presence of multiple primary users (PUs) under spectrum sharing environment. Specifically, we derive the closed-form expressions of outage probability (OP) and ergodic capacity (EC) of the considered system under the interference constraint imposed by multiple adjacent PUs. To get further insights, the asymptotic analysis for OP at high signal-to-noise ratios (SNRs) is also obtained. Numerical results are provided to verify our analysis and reveal the impacts of key parameters on system performance.

Satellite and high altitude platform are considered as the key parts of the next generation networks, and specifically for the internet-of-things networks, which are utilized to provide unobstructed connections and massive user access for terrestrial networks. In this paper, we investigate the power allocation and system performance of non-orthogonal multiple access (NOMA)-enabled integrated satellite-high altitude platform-terrestrial systems under practical limitations. Particularly, a practical system model is established by considering the channel estimation errors and imperfect successive interference cancellation at the receiver. To achieve the different quality of service requirements among multiple served users, we propose a novel NOMA-based power allocation scheme. In addition, the analytical and asymptotic expressions for the outage probability of NOMA users are obtained to verify the proposed scheme as well as the ergodic capacity. Finally, numerical results are corroborated with Monte Carlo simulations, which show the correctness of our analytical results, and the benefits of our proposed scheme. The proposed scheme indicates that the HAP relay link plays a significant role in the system performance.

Integrated satellite-high altitude platform-terrestrial networks (IS-HAP-TNs) and non-orthogonal multiple access (NOMA) scheme are considered to be the key components of next generation networks, which can satisfy the demands of high-quality transmission, wide coverage and large-scale connections. In this letter, we analyze the performance of NOMA-based IS-HAP-TNs with transmit antenna selection (TAS) in the presence of imperfect channel state information (CSI) and successive interference cancellation (SIC). Specifically, considering the requirements of different users for spectrum efficiency, two TAS schemes are proposed to balance the system performance and complexity. In addition, the closed-form expressions for the outage probability of the IS-HAP-TNs in the presence of imperfect CSI and SIC are derived to verify the performance of different schemes. Besides, the asymptotic outage behavior and diversity orders at high signal-to-noise ratios are also presented to get further insights. Finally, Monte Carlo simulations manifest the advantages and disadvantages characters of two schemes and reveal the impacts of key parameters on the system performance.

Satellite-high altitude platform (HAP)-terrestrial networks have been considered as an indispensable infrastructure of next-generation networks because they can offer massive access service with high throughput and broad coverage connections. Meanwhile, non-orthogonal multiple access (NOMA) and two-way relaying techniques are considered as potential technologies to enhance the spectrum efficiency and connectivity. Thus, in this paper, the performance of two-way satellite-HAP-terrestrial networks with NOMA, which are subject to imperfect channel state information and successive interference cancellation, is investigated. Closed-form and asymptotic expressions for the outage probability, and ergodic capacity are derived to verify the impact of the system and channel parameters on the considered network. Simulation results indicate that the optimization power allocation factor is independent of the channel fading.

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.