Research On Highly Energy-efficient Secure Millimeter-wave Robust Beamforming Technology With UAV Jittering

As an important part of the space-air-ground integrated communication network,unmanned aerial vehicle(UAV)communication benefiting from low cost,flexible deployment and strong airto-ground line-of-sight(Lo S)transmission link has been extensively applied to improve the coverage and capacity of the wireless network.Millimeter-wave(mm Wave)communication technology with its abundant spectrum resources can meet the high-throughput and low-latency requirements of various UAV application scenarios,so it has been widely used in UAV communication systems.However,the broadcast nature of wireless channels makes UAV communication vulnerable to various attacks,and the high-frequency characteristic of mm Wave brings more energy consumption to the UAV with limited airborne energy,so UAV communication is faced with severe security and energy consumption challenges.In addition,the unique jitter feature of UAVs results in imperfect channel state information,which causes a non-negligible influence on air-to-ground communication links.Therefore,this thesis aims to study the robust and secure energy-efficient beamforming schemes for UAV mm Wave communication with UAV jittering,as follows:(1)To maximize the secrecy energy efficiency of the UAV mm Wave communication system,a robust digital beamforming scheme against UAV jittering is proposed.Considering the impact of UAV jittering on imperfect angle-of-departure(Ao D)estimation of the air-to-ground channel,a worst-case secrecy energy efficiency(SEE)maximization problem is formulated subject to the UAV transmit power constraint.Due to the difficulty in solving this problem arising from the Ao D uncertainties and the non-convex structure of objective function,we first adopt the discretization method to simplify Ao D uncertainties to a deterministic form and then exploit the successive convex approximation approach with auxiliary variables to convert the problem into a convex one.Finally,an iterative algorithm is designed to obtain the suboptimal solution.Numerical results are provided to confirm the effectiveness and superiority of the proposed robust digital beamforming scheme compared to some benchmark schemes.(2)To maximize the secrecy energy efficiency of the UAV mm Wave communication system,a robust hybrid beamforming scheme against UAV jittering is proposed.Considering the constraints for the total transmit power and the constant-modulus constraint of the analog beamforming matrix,an optimization problem with UAV jittering is formulated to maximize the worst-case secrecy energy efficiency.To get the optimal solution to the optimization problem,the discretization method combined with the theory of convex hull,H(?)lder inequality and Cauchy-Schwarz inequality is applied to eliminate the Ao D uncertainties.Then,the optimization problem is decomposed into two sub-problems of digital beamforming optimization and analog beamforming optimization,and the convex approximation forms of the sub-problems are derived by the successive convex approximation method.Finally,an alternating iterative beamforming algorithm with updated weighted coefficients is proposed to complete the robust hybrid beamforming design.Simulation results show that the proposed robust hybrid beamforming scheme can effectively against UAV jittering and significantly improve the secrecy energy efficiency of the system.