Physical Layer Security for NOMA Transmission in mmWave Drone Networks

The non-orthogonal multiple access (NOMA) and millimeter-wave (mmWave) transmission enable the unmanned aerial vehicle (UAV) assisted wireless networks to provide broadband connectivity over densely packed urban areas. The presence of malicious receivers, however, compromise the security of the UAV-to-ground communications links, thereby degrading secrecy rates. In this work, we consider a NOMA-based transmission strategy in a mmWave UAV-assisted wireless network, and investigate the respective secrecy-rate performance rigorously. In particular, we propose a protected-zone approach to enhance the secrecy-rate performance by preventing the most vulnerable subregion (outside the user region) from the presence of malicious receivers. The respective secrecy rates are then derived analytically as a function of the particular protected zone, which verifies great secrecy rate improvements through optimizing shape of the protected zone in use. Furthermore, we show that the optimal protected zone shape for mmWave links appears as a compromise between protecting the angle versus distance dimension, which would otherwise form to protect solely the distance dimension for sub-6 GHz links. We also numerically evaluate the impact of transmission power, protected-zone size, and UAV altitude on the secrecy-rate performance improvement for the sake of practical deployments.

Automated summary

This work investigates the secrecy-rate performance of a NOMA-based transmission strategy in mmWave UAV-assisted wireless networks. A protected-zone approach is proposed to enhance secrecy-rate performance by preventing the presence of malicious receivers. Numerical evaluations consider the impact of transmission power, protected-zone size, and UAV altitude on secrecy-rate performance improvements for practical deployments.