UAV-Assisted Multi-User Secure Communication Based on Hybrid DF and AF Protocol

Aiming at the threat of eavesdropping in unmanned aerial vehicle (UAV)-assisted communication networks, multiuser secure communication with multi-relay nodes and multi-eavesdropping threats is investigated in this paper. By deploying a dual-antenna UAV relay node, a hybrid decode-and-forward (DF) and amplify-and-forward (AF) protocol is considered to transmit data. In addition, cooperative jamming techniques are used in order to improve the performance of the secure confidential communication. The secure communication problem is formulated as an optimization problem. The goal is to maximize the minimum secrecy transmission rate subject to UAV transmitting power, user transmitting power, and channel bandwidth. By introducing a grey wolf optimizer (GWO), the suboptimal solution is obtained. Simulation results show that the GWO has higher secrecy transmission rate than the firefly algorithm and the average bandwidth and fixed transmitting power method.