Abstract This paper presents a full‐duplex and multi‐antenna relay‐aided transmission scheme for the user‐oriented perspective in cooperative non‐orthogonal multiple access (NOMA) systems. Relying on the service requirements, two legitimate users with security demands (SU) and quality of service (QoS) demands (QU) are paired for NOMA execution. The security of SU is enhanced through inverse power allocation of the conventional NOMA. The QoS requirements for QU are guaranteed, simultaneously. Then, the precoding design at the multi‐antenna relay has been exploited to improve the reliability demands of SU. Closed‐form expressions for SU's outage probability (OP) and intercepted probability, as well as QU's OP, are derived. The security–reliability trade‐off is also presented. Additionally, performance analysis under the half‐duplex and multi‐antenna scheme is provided as a benchmark for comparison. Finally, numerical simulations are performed to confirm the accuracy of the theoretical derivations under different schemes. Results demonstrate the superiority of the proposed scheme over benchmark schemes in terms of improving the security and reliability of SU, as well as saving power consumption of the system.

The utilization of the aerial base station (ABS) has been treated as a promising solution to the coverage, deployment and cost savings problems in the wireless networks. Different from the terrestrial networks, in the ABS-assisted air-to-ground network, the service positions of ABSs and user association should be jointly optimized, which is challenging due to the unknown propagation environment in the task area. In this article, a binary radio map (BRM) is constructed to grant the ABSs the location-specific channel knowledge within the entire task area. With the assistance of the BRM, a multiple ABS deployment and user association framework is proposed. The framework consists of an offline optimization stage during which the initial ABS deployment position and user association are jointly optimized based on the BRM, and an online refinement stage during which the ABS positions and user association are refined in real time according to both the observed Quality of Service (QoS) and virtual QoS emulated by the BRM. The performance of the proposed framework is examined in a complex urban scenario with mobile users. The results show that higher achievable rate performance and lower on-board energy consumption can be realized when compared with the reference schemes.

Underdetermined blind DOA estimation for linear arrays without the prior knowledge of array configuration is a challenging problem. Two methods are proposed to solve this problem based on a moving platform. The first one exploits the structure of the equivalent array manifold matrix constructed by using several different time intervals for the array motions and utilizes iterative optimization to obtain the estimation of DOAs. By considering secondary time intervals for the array motions further, the other combines the DOA matrix and multistage Wiener filter (MSWF) to estimate DOAs in a more cost-effective way. Simulation results and complexity analysis testify the effectiveness and superiority of the proposed algorithms.

Abstract This paper examines a wireless communication network comprised of a source and multiple relay‐user pairs in face of multiple malicious eavesdroppers. In order to improve the physical layer security of cooperative communication networks, a joint relay‐user pair and friendly jammer selection (JRUPaFJS) scheme is proposed. Apart from the impacts of friendly jammers on the eavesdroppers, that on the legitimate users is also taken into account due to the presence of channel state information estimation errors. The traditional round‐robin (TRR) scheme and traditional pure relay‐user pair selection (TPRUPS) scheme are considered as benchmark schemes. The exact closed‐form expressions of outage probability and intercept probability for the TRR and TPRUPS schemes as well as JRUPaFJS scheme over Rayleigh fading channels are derived. It is verified that the proposed JRUPaFJS scheme outperforms both the TRR and TPRUPS schemes in terms of their SRT, which demonstrates the wireless security and reliability benefits of exploiting JRUPaFJS scheme. Moreover, as the number of relay‐user pairs increases, the SRT of the TPRUPS and JRUPaFJS schemes improve notably, while as the number of eavesdroppers increases, the SRT of all the three schemes become worse.

In this paper, we investigate secure unmanned aerial vehicle (UAV) communication in the presence of multiple UAV adaptive eavesdroppers (AEs), where each AE can conduct eavesdropping or jamming adaptively by learning others’ actions for degrading the secrecy rate more seriously. The one-leader and multi-follower Stackelberg game is adopted to analyze the mutual interference among multiple AEs, and the optimal transmit powers are proven to exist under the existing conditions. Following that, a mixed-strategy Stackelberg Equilibrium based on finite and discretized power set is also derived and a hierarchical Q-learning based power allocation algorithm (HQLA) is proposed to obtain the optimal power allocation strategy of the transmitter. Numerical results show that secrecy performance can be degraded severely by multiple AEs and verify the availability of the optimal power allocation strategy. Finally, the effect of the eavesdropping cost on the AE’s attack mode strategies is also revealed.