Secrecy Energy Efficiency Maximization for UAV-Enabled FDMA systems

In this paper, we consider an unmanned aerial vehicle (UAV), which serves multiple legitimate ground users with frequency division multiple access (FDMA) approach in the presence of a potential eavesdropper (EV) with uncertain location information. We also assume that UAV must also avoid flying over the no-fly-zone (NFZ). We aim to maximize the secrecy energy efficiency (SEE) by the robust joint design of the rotary-wing UAV three dimensional (3D) trajectory, bandwidth allocation, and transmit power. However, the optimization problem becomes challenging to solve optimally due to the non-convexity of the problem and the imperfect location information of the EV. We develop an efficient iterative algorithm to obtain its high-quality suboptimal solution. The numerical results indicate that our proposed joint optimization algorithm outperforms the benchmark schemes, resulting in significant enhancement of the energy efficiency of the system.