Research On Hybrid Beamforming In Millimeter-Wave MIMO System

With the development of the mobile communication technology,the demand of the wireless communication transmission rate is becoming higher and higher.At the same time,the exponential growth of wireless users also poses a severe challenge to wireless communications.The millimeter-wave(mmWave) MIMO communication system can provide rich spectrum resource and improve transmission rate.The significant characteristic of mmWave communication is that the path loss is serious.Therefore,hybrid beamforming technology was considered to resist path loss during signal transmission.Based on the above analysis,the hybrid beamforming algorithm for single user and multi-user mmWave MIMO system are designed respectively in this thesis,and the performance of proposed algorithm is close to that of fully digital beamforming algorithm.The emphasis of this thesis is as follows:1.The physical characteristics and transmission characteristics of mmWave are analyzed,and wireless channel model suitable for the mmWave communication is constructed.The classical single-user and multiuser fully digital beamforming algorithms in low frequency MIMO system are researched,which provide theoretical knowledge for the study of hybrid beamforming technology.2.In order to further improve the spectrum utilization of single user MIMO(SU-MIMO) system and obtain stable system performance,an alternating minimum mean square error(Alt-MMSE) hybrid beamforming algorithm is proposed,which uses fully digital matrix to update the analog matrix,and the obtained analog matrix is used as the initial condition for the next iteration,the mixed digital/analog beamforming matrix is obtained through several iterations.The simulation results show that the performance of proposed Alt-MMSE algorithm is obviously superior to that of Orthogonal Matching Pursuit(OMP) hybrid beamforming algorithm.Compared with the Matrix Decomposition based Hybrid Processing(MD-HP) algorithm,the performance of Alt-MMSE is more close to that of fully digital beamforming scheme.3.A hybrid beamforming algorithm based on block diagonalization is proposed for mmWave multi-user MIMO(MU-MIMO) system to solve multi-user interference.Firstly,obtaining the global solution of the analog matrix by designing analog matrix set,then constructing equivalent channel matrix,and finally obtains the digital matrix by using block diagonalization.In addition,a hybrid beamforming based on Minimum Euclidean Distance is proposed to minimize the Euclidean distance between digital/analog matrix and fully digital matrix.The simulation results show that the performance of the proposed BD-Hy algorithm and the ME-Hy algorithm are better than that of OMP multiuser hybrid beamforming algorithm,and BD-Hy algorithm can significantly reduce inter-user interference,ME-Hy algorithm can significantly improve the spectrum efficiency with the assumption of zero inter-user interference.