Secure Communication in NOMA-Assisted Millimeter-Wave SWIPT UAV Networks

Future wireless networks have requirements of large connections, low power consumption, high reliability, and strong security. Considering the abundant available bandwidth of millimeter wave (mmWave) and the large line-of-sight (LOS) link probability of air–ground channel, in this article, we develop a framework to study security, reliability and energy coverage performance of the downlink mmWave simultaneous wireless information and power transfer (SWIPT) unmanned aerial vehicle (UAV) networks under nonorthogonal multiple access (NOMA) and orthogonal multiple access (OMA) schemes, where a UAV serves two types of authorized Internet of Things (IoT) devices in the presence of multiple passive eavesdroppers. Directional modulation (DM) is also used to improve the physical layer security (PLS) performance. First, the analytical expressions for connection outage probability (COP), secrecy outage probability (SOP), and effective secrecy throughput (EST) of the users with high rate security requirement (HRSR) under NOMA and OMA schemes are derived using stochastic geometry. Then, we optimize the active antenna selection of DM using adaptive genetic simulated annealing algorithm (AGSA) to further improve the secrecy performance based on the obtained analytical results. Finally, the closed-form expressions for the COP and energy-information coverage probability (EICP) of the energy-constrained users with low-rate requirement (ECLR) under NOMA and OMA schemes are obtained. The numerical and simulation results provide interesting insights into the influence of various parameters on the tradeoff between the reliability and security for the HRSR user, and the tradeoff between the reliability and energy coverage for the ECLR user. Moreover, the EST of the NOMA scheme outperforms OMA at low transmit power and high codeword transmission rate.