Optimal Design Of Energy-Efficient Secure Transmission In Full-Duplex MmWave UAV Relay Communication Systems

In recent years,unmanned aerial vehicle(UAV)communication have received considerable attention from domestic and foreign researchers by its unique advantages,such as high maneuverability,fast and flexible deployment control,large coverage of high-altitude operations,and convenient updating of communication equipment,especially the UAVs can be used as full-duplex relay platform to improve the spectrum efficiency based on expanding the coverage of communication systems.Meanwhile,with the development of millimeter-wave(mm Wave)technology,the application of mm Wave equipment which has a smaller size and higher frequency to the UAV communication system can effectively solve the problems of limited UAV load and shortage of frequency spectrum resource.Despite the above advantages,the inherent high energy problem of mm Wave high-frequency transmission is still a bottleneck problem that needs to be solved urgently for UAV with the space and energy constraints.In addition,due to the broadcast characteristics of wireless transmission,UAVs are extremely vulnerable to illegal eavesdropping from malicious users in the process of performing relay transmission tasks,which seriously threatens the security of UAV data transmission.Therefore,in view of the energy efficiency and security of the full-duplex mm Wave UAV relay communication system,this paper designs an energy-efficient secure transmission optimization scheme for the UAV full-duplex relay communication system based on the definition of secrecy energy efficiency.The specific research contents are as follows:(1)For the quasi-static rotary-wing UAV that is performing the relay transmission task,by deploying the UAV hovering position and optimizing the relay beamforming weight vector,the secrecy energy efficiency performance of the system is maximized in the case of limited hovering time.Firstly,the air-ground link channel model and the full-duplex self-interference model are constructed based on a mm Wave planar array,the signal model of the communication system is deduced,and the concept of system secrecy energy efficiency is proposed.The joint optimization problem of UAV position and decoding and forwarding beamforming is proposed,and a convex approximation conversion scheme based on Sequential Convex Approximation(SCA)and penalty function method is proposed to obtain the convex approximation form of the original optimization problem.And designed an iterative algorithm with good convergence performance,which can effectively obtain the global optimal approximate solution of the UAV relay beamforming weight vector and hovering position under finite iterations.The simulation results verify the effectiveness and superiority of the proposed iterative algorithm.(2)According to the charging requirements of rotary-wing UAVs in practical application scenarios,by optimizing the design of the UAV’s trajectory from the charging station to the mission area and the beamforming weight vector of each flight time slot,the system total secrecy energy efficiency maximization in the mission cycle are realized by this design.Firstly,according to the characteristics of the millimeter-wave air-ground link,the time slot-based channel model,signal model and UAV propulsion power consumption model are constructed.Secondly,the total secrecy energy efficiency maximization optimization problem is established based on the UAV propulsion power consumption constraint.The original optimization problem is decomposed into two sub-problems of beamforming optimization and trajectory optimization by using Block Coordinate Descent(BCD)method,and the convex approximation form of the sub-problem is derived by introducing auxiliary variables and SCA method.The joint iterative algorithm of point to point can obtain the global optimal trajectory of the UAV and the beamforming weight vector of each flight time slot.The simulation results verify the effectiveness of the proposed algorithm,and reflect the advantages of the proposed total secrecy energy efficiency maximization scheme at the same time.