Research On Hybrid Beamforming Technology For Millimeter Wave Communication Of UAV

With the rapid growth of communication service demand in modern society,UAV millimeter-wave communication has attracted more and more attention due to its high flexibility,strong security and wide bandwidth.It has become an important solution to seamless coverage in 5G communication.The research shows that the array antenna technology can produce narrow beams with large gain,thus overcoming the huge loss in millimeter wave wireless propagation process.The traditional beamforming technology of multi-antenna system is based on full digital coding in baseband.Although all-digital system has the advantages of high flexibility and strong beam gain,its high cost and large energy consumption make this method face enormous limitations in UAV millimeter-wave communication system.To solve this problem,this paper proposes to use hybrid beam coding technology to generate vectors approximating the full digital form,so as to reduce the cost and energy consumption.The main work of this paper is listed as follows:1.According to the sparse characteristics of millimeter wave,this paper transforms the hybrid beamforming problem into the reconstruction of sparse matrix.Orthogonal Matching Pursuit(OMP),Gradient Pursuit(GP)and Greedy Geometry(GG)are introduced to iterate.The simulation results show that the GG algorithm has the best iteration efficiency and the GP algorithm has the lowest complexity.2.To solve the mutual coupling problem caused by the small distance of millimeter wave array elements,this paper firstly studies the mechanism of mutual coupling effect,explores the beam distortion under mutual coupling effect,then establishes the equivalent channel model of mutual coupling effect,and finally designs the hybrid precoding of beams based on this model,which effectively improves the communication rate loss caused by beam distortion.3.To solve the problem of periodic beam deflection caused by wind speed and airframe vibration in millimeter-wave communication of UAV,firstly this paper establishes an equivalent channel model based on the set communication scenario,then it calculates the ideal beam coding vector according to the channel model,and finally uses the sparse reconstruction algorithm to decompose the hybrid coding.In that case,the approximate ideal beam design scheme for the above problems is presented.The simulation results show that the proposed beam coding scheme based on hybrid beamforming system can effectively solve the above practical problems and improve the millimeter-wave communication performance of UAV.In addition,this paper also explores the performance of different beam shapes in gain,robustness and anti-jamming,which lays a foundation for future researchers to solve related problems.