Research On Hybrid Precoding Technology In Millimeter Wave Massive MIMO Systems

5G provides efficient and reliable communication services for a large number of end users,and brings great convenience to people's communication and lifestyle.5G adopts five key technologies to achieve its ultra-high performance.Among them,the millimeter-wave frequency band is rich in resources,which can realize high-speed data transmission,and the Massive Multiple-input Multipleoutput(m MIMO)technology can ensure the reliability of the transmission system.This thesis mainly does the following work on how to design hybrid precoding technology in mm Wave massive MIMO scenarios:The introduction focuses on the five key technologies that support the high performance of 5G,elaborates the research status of precoding technology,and briefly analyzes the advantages and disadvantages of the existing hybrid precoding schemes.The second chapter introduces the basic principles of different MIMO systems,expounds the characteristics of millimeter-wave channels and the channel modeling process,analyzes the design principles and design processes of several classic hybrid precoding schemes in detail,and compares their performances through simulation.In Chapter 3,a hybrid precoding scheme based on Equivalent Channel Gain MaximizationHybridly Connected(ECGM-HC)is proposed for the millimeter-wave massive MIMO system with hybrid connection structure in downlink.First,the original channel matrix and the analog precoding matrix are used to form an equivalent channel matrix,and it is decomposed into sub-arrays.The blocks are combined diagonally to obtain the analog precoding matrix,and finally the digital precoding matrix is obtained column by column using the idea of successive interference cancellation.The proposed algorithm can flexibly set the structure of the transmitter array,and has wider application scenarios and better performance.In chapter 4,a hybrid precoding scheme based on channel candidate vector matrix is designed in a system where both transceivers are fully connected.According to the idea of channel "hardening",the transmitter uses the product of the left unitary matrix and the diagonal matrix after singular value decomposition of the channel conjugate transpose matrix as the candidate vector matrix of the analog precoding matrix.The minimum Euclidean distance between the coding matrix product and the optimal hybrid precoding matrix is the objective function,the optimal analog precoding matrix is updated and iterated from the candidate vector matrix,and finally the optimal digital precoding matrix is obtained according to the equivalent channel.The combination matrix is designed with the same idea.Simulation analysis shows that the algorithm can achieve good performance in both perfect channel and imperfect channel state information,and it is better than the orthogonal matching pursuit algorithm.Finally,the shortcomings of the thesis and the direction of follow-up work are analyzed,and some open questions and prospects for follow-up research are proposed.