Research On Channel Estimation And Hybrid Precoding In MMWAVE MIMO System

The goal of future wireless communication is to provide higher transmission rate,larger system capacity,and meet the communication needs among all things.It is not realistic to achieve this goal at the traditional low-frequency spectrum,communication must be extended to the millimeter-wave frequency.The physical properties of millimeter-wave determines that it need to be combined with MIMO technology to provide good service.The use of large-scale antenna arrays in millimeter-wave systems,while improving performance,has also posed problems in economic cost and circuit design.If using digital precoding method,we need to configure the same number of antennas with the RF link,which is very difficult.In order to solve this problem,the hybrid precoding architecture is proposed.In the RF domain,analog precoder is composed of phase shifters,and in the baseband still use the traditional digital precoder.This structure can significantly reduce the number of RF links in the system.Hybrid-architecture millimeter-wave MIMO systems have a lot to be studied in terms of channel estimation and precoding.First,the antenna array size is larger,so the channel estimation scale also increased.It is necessary to study the new channel estimation method.Second,the improvement of channel estimation accuracy is also a goal.Third,the analog precoder consists of phase shifters that only can adjust the phase of signal but cannot adjust the amplitude.This physical constraint determines the need to study the precoding method that is suitable for hybrid architecture systems.On these problems,this paper has carried out some research.In this paper,we first study the propagation characteristics of millimeter-wave in the scattering space,and discuss the time domain sparsity and angular sparsity of millimeterwave channel.Based on the sparsity of the channel,this paper uses the cluster model to model the millimeter-wave narrowband channel.The mathematic representation model of hybrid-architecture millimeter-wave MIMO system is established.In view of the sparsity of the millimeter-wave channel,this paper studies the channel estimation method based on sparse signal reconstruction.Firstly,the knowledge of compressive sensing and sparse signal reconstruction is introduced,and the OMP and CoSaMP reconstruction algorithms are discussed.Based on these two algorithms,this paper designs channel estimation methods based on OMP and CoSaMP algorithm,and carries on the simulation analysis,and compares the advantages and disadvantages of these two methods.On this basis,an improved sparse signal reconstruction algorithm is proposed,which is different from OMP in that multiple sensing atoms are selected in each match.The simulation results show that the performance of the newly channel estimation method is better than that of the OMP based channel estimation method,and the computational complexity is not higher obviously.Finally,this paper studies the precoding method for hybrid-architecture millimeterwave systems.The mathematical model of hybrid precoding problem is established,and the optimization objective function of the problem is discussed.On this basis,two hybrid precoding matrix optimization methods based on alternating optimization algorithm are studied.The simulation results show that the proposed methods can achieve good performance and the implementation complexity of these two methods are low.