Intelligent Reflecting Surfaces (IRS) enhance spectral efficiency by adjusting reflection phase shifts, while Non-Orthogonal Multiple Access (NOMA) increases system capacity. Consequently, IRS-assisted NOMA communications have garnered significant research interest. However, the passive nature of the IRS, lacking authentication and security protocols, makes these systems vulnerable to external eavesdropping due to the openness of electromagnetic signal propagation and reflection. NOMA’s inherent multi-user signal superposition also introduces internal eavesdropping risks during user pairing. This paper investigates secure transmissions in IRS-assisted NOMA systems with heterogeneous resource configuration in wireless networks to mitigate both external and internal eavesdropping. To maximize the sum secrecy rate of legitimate users, we propose a combinatorial optimization graph neural network (CO-GNN) approach to jointly optimize beamforming at the base station, power allocation of NOMA users, and phase shifts of IRS for dynamic heterogeneous resource allocation, thereby enabling the design of dual-link or multi-link secure transmissions in the presence of eavesdroppers on the same or heterogeneous links. The CO-GNN algorithm simplifies the complex mathematical problem-solving process, eliminates the need for channel estimation, and enhances scalability. Simulation results demonstrate that the proposed algorithm significantly enhances the secure transmission performance of the system.

Satellite-terrestrial integrated network is regarded as an effective solution to address the issues of network coverage blind spots in remote areas and uneven distribution of network resources. However, the limited spectrum resources fail to meet the ever-growing user demands, and satellite-to-ground communications are susceptible to obstruction and shadowing effects, which compromise signal transmission quality. To this end, this article investigates a satellite-aerial-terrestrial integrated network (SATIN) enhanced by reconfigurable intelligent surfaces (RISs) and uncrewed aerial vehicles (UAVs) to bolster communication reliability and coverage capabilities. To reduce signaling overhead and transmission delay, the satellite employs a grant-free nonorthogonal multiple access (GF-NOMA) protocol for user communications. Considering that cochannel interference (CCI) is inevitable in practical communication scenarios, exact analytical expressions for the outage probabilities of near user (UN) and far user (UF) are derived under which the shadowed Rician fading model and Nakagami- $m$ fading model are employed for the satellite link and terrestrial link, respectively. Furthermore, an expression for the system outage probability and energy efficiency (EE) has been provided to facilitate further evaluation of the system performance. Simulation results demonstrate that increasing the number of RIS reflecting elements effectively mitigates the adverse impact of CCI on system outage performance. Even when satellite links are more severely affected by shadowing effects, the proposed system maintains excellent outage performance, verifying its robustness and applicability in complex environments. In addition, to achieve optimal system EE, it is crucial to dynamically adjust the configuration parameters of the number of RIS reflecting elements and transmit power of UAV based on specific application scenarios.

With the rapid growth in the number of communication devices, there is a sharp increase in the demand for quality of service in wireless networks. To meet the requirements of high stability, low latency, and high reliability in wireless communications, unmanned aerial vehicle (UAV) communication has become a critical solution for enhancing performance of future wireless networks. Addressing the demands for fast response of communication devices and flexible coverage in complex, diverse, and flexible emerging communication scenarios, a multi-source multi-UAV cooperative relay communication system with co-channel interference is studied in the presence of direct links between source nodes and destination nodes. To enhance the interference resilience for the system understudy, two receiver diversity combining techniques, namely maximum ratio combining (MRC) and selection combining (SC), are proposed to combine the signals received by the direct link and UAV link at the destination node. Based on the two-step source-relay selection protocol, optimal source node is firstly selected to broadcast signals to multiple UAV relays and destination nodes, and then the optimal UAV relay is selected according to the selection cooperation scheme for improving the robustness of UAV cooperative relay systems. Performance analysis of considering multi-source multi-UAV cooperative communication system is conducted by providing closed-form expressions for the exact outage probability, asymptotic outage probability, and ergodic capacity. Numerical simulations are provided to validate the theoretical analysis, and the results show that the multiple user diversity gain and cooperative diversity cannot be obtained due to the presence of co-channel interference. However, the damage caused by co-channel interference to the communication system can be compensated by increasing the number of source nodes or UAV relays.

This paper investigates a multiple users cooperative cognitive non‐orthogonal multiple access (NOMA) network with energy harvesting. Primary transmitter and secondary sources serving as energy‐constrained nodes harvest energy from the power beacon PBS. In primary network, primary transmitter sends signals towards primary receiver. In order to make full use of spectrum resources, the secondary network access the licensed spectrum of primary network with overlay mode, where the best secondary source with maximum transmission signal‐to‐noise ratio between primary transmitter and secondary sources act as relays to forward signal via NOMA principle. In this context, two cooperative transmission protocols, namely, traditional NOMA cooperative transmission and adaptive NOMA cooperative transmission are proposed. For NOMA cooperative transmission, relays use NOMA to forward the superimposed signal of primary signal and secondary signal without any constrain. However, for adaptive NOMA cooperative transmission, relays use NOMA by judging whether the transmission between primary transmitter and primary receiver is successful or not. Primary receiver merges signals received from two transmission slots by selection combining. Finally, exact and asymptotic outage probability of primary network and secondary network with two cooperative transmissions are derived and simulated. It is shown that outage performance is improved for the proposed adaptive NOMA cooperative transmission.

In this paper, we investigate the performance of cooperative non-orthogonal access (NOMA) network with energy harvesting, where, source node and relay node serving as energy-constrained nodes harvest energy from the power beacon PBS. Source sends the superposed message towards the nearly-located user and relay via NOMA principle. The relay superposes and forwards the decoded signal and its own signal to the far-located user and the destination according to NOMA protocol. To measure the performance of the system quantitatively, we derive the exact closed form expressions for the outage probabilities of the near user, far user, and destination respectively over Rayleigh fading channels. Simulation results show that the reasonable power distribution coefficient and the increasing of transmission power of the power beacon improve the performance of cooperative NOMA network.