Research On The Analog-digital Hybrid Receiving For Inter-user Interference Suppression In Millimeter Wave Multi-antenna Systems

With the rapid growth of wireless communication data,people put forward higher requirements for wireless transmission rate.However,limited by spectrum resources and spectrum efficiency,the existing fourth generation mobile communication technology cannot meet people's communication needs.The millimeter wave works in the frequency band above 30 GHz and can provide the communication frequency band above 10 GHz,which greatly alleviates the limitation of spectrum resources.With the use of massive multiple input multiple output(MIMO)technology,the base station is equipped with the large antenna array,which alleviates the limitation of spectrum efficiency.Therefore,researchers turned their attention to millimeter wave and massive MIMO technology.In addition,the short wave length characteristic of the millimeter wave allows the large antenna array to be integrated into a limited space,and the path gain provided by the antenna array can well compensate for the path loss of the signal during transmission.Therefore,the combination of millimeter wave and massive MIMO technology has great potential and is the key technology of the fifth generation mobile communication technology standard.The main content of this paper is the research on the analog-digital hybrid receiving for inter-user interference suppression in millimeter wave multi-antenna systems.Actually,there are many types of millimeter wave multi-antenna systems,so this paper takes the millimeter wave massive MIMO system as an example to analyze.In addition,the focus of the research on the analog-digital hybrid receiving is the design of the hybrid beamforming at the base station.Therefore,the research focus of this paper is the hybrid beamforming design of millimeter wave massive MIMO systems at the base station.Aiming at the inter-user interference problem in multi-user millimeter wave massive MIMO systems,two interference suppression algorithms are proposed: maximizing minimum phase difference based hybrid beamforming algorithm and grouping optimization based hybrid beamforming algorithm.The main work of this paper is as follows:Firstly,this paper introduces the research background and significance of millimeter wave massive MIMO systems.Then,the research status of hybrid beamforming technology in millimeter wave massive MIMO systems is introduced in detail,as well as the research content and achievements of this paper.Secondly,this paper introduces MIMO technology,massive MIMO technology and millimeter wave technology.And,the development process and principle of beamforming technology are introduced.Then,we introduce the precoding technology of millimeter wave massive MIMO systems,the traditional digital precoding and the hybrid precoding of millimeter wave massive MIMO systems.Then,the multi-user millimeter-wave massive MIMO system is introduced.The all-digital zero forcing algorithm as a performance reference and the hybrid beamforming algorithm based on schmidt orthogonalization are introduced,respectively.Thirdly,a hybrid beamforming algorithm based on maximizing the minimum phase difference is proposed for millimeter-wave massive MIMO multiuser systems.The proposed algorithm uses the channel gain threshold and the correlation characteristic of the array response vectors to select vector sets that provide higher signal power from an analog beamforming vector codebook.Then,inter-user interference is measured by the phase difference between the analog beamforming vector and the main propagation path array response vector.Additionally,the criterion of maximizing the minimum phase difference is proposed to suppress the strongest inter-user interference.Analysis and simulation results show that the proposed algorithm can provide higher system sum rate with lower computational complexity than traditional approaches.Fourth,we propose a low complexity grouping optimization based hybrid beamforming algorithm.Specifically,we group users according to user channel correlations and a correlation threshold.Users with strong correlations are grouped into a group.Then,with the goal of maximizing capacity,the low-dimensional exhaustive algorithm is used in each group to select the base station analog beamforming vector.Moreover,the influence of the analog beamforming vectors of the previous groups is considered,and a greedy algorithm is adopted.Simulation results show that the system sum rate of the grouping optimization hybrid beamforming algorithm is higher than that of the existing algorithms.And compared with the maximizing the minimum phase difference hybrid beamforming algorithm,when the signal to noise ratio is 10 d B,the system sum rate of the grouping optimization hybrid beamforming algorithm is 1.5 times than the maximizing the minimum phase difference hybrid beamforming algorithm,but the cost is the higher computational complexity.Finally,we summarize the content of the article,and prospect the future research work.