Channel Modeling And Analysis Of Massive MIMO System

The mobile internet and the Internet of Things will become the main driving forces of mobile communication development towards 2020 and beyond.To meet the requirements of future explosive mobile data traffic growth,massive device connections,continuous emergence of new services and scenarios,and ultra-high data rate,the next generation mobile communication system has become the focus of global attention.In this context,the massive MIMO(Multi-Input Multi-Output)technology has attracted wide attentions from academia and industry because it can greatly improve the spectral efficiency of the system without increasing the spectrum resources and the total transmitting power.Massive MIMO technology has many advantages such as improving system capacity,spectrum efficiency,user experience data rate,energy saving and so on.Therefore,massive MIMO technology is regarded as the core technology of future mobile communication system such as the fifth generation(5G)mobile communication system,the next generation Wifi,B5G(beyond 5G)and 6G(6th Generation)mobile communication system.As the basis of performance analysis of wireless mobile communication system,wireless mobile channel is also the most important part for massive MIMO system research.To understand and master the channel characteristics of the massive MIMO system and to establish the channel model of the massive MIMO system are essential for choosing appropriate system architecture,a reasonable communication scheme,and improving system performance.Therefore,this paper summarizes the existing massive MIMO system channel models,and analyzes the shortcomings of the existing massive MIMO system channel modeling research.Then,this paper carries out research aiming at the shortcomings of the existing works.The main contents and contributions are as follows:(1)This paper first considers the case of few antennas(less than 10 antennas)to model and analyze the channel of MIMO system.This paper uses geometric method to establishe a new three-dimensional geometrical channel model for MIMO system,and derives the antenna correlation and channel capacity based on geometric parameters.The relationship between channel parameters and system performance is analyzed.This model not only has azimuth angle information,but also contains elevation angle information,which is more suitable for the actual transmission scenario.It is also easy to be extended to massive MIMO system channel modeling of different antenna configurations.Then,in order to reduce the correlation between antennas and miniaturize the equipment,the polarization characteristic is introduced into the MIMO system channel model to establish three-dimensional multi-polarized MIMO system channel model.Compared with other multi-polarized MIMO system channel models,the proposed model considers the effects of antenna cross-polarization isolation,channel depolarization,antenna tilt and other parameters on the system performance at the same time,and the simulation results are compared with measured data,which is more in line with the actual situation.(2)This paper increases the number of antennas of the proposed MIMO system channel model to a large number(tens or even hundreds),and then establish a three-dimensional geometrical channel model for massive MIMO system.The model considers both the horizontal and vertical azimuth,which characterizes the scattering information in the vertical direction.This paper considers both the non-stationarity property of the array and the spherical wave effect.Aiming at the fact that the current channel models are point-to-point,the proposed model considers multi-user massive MIMO system.Aiming at the problem of high complexity of geometric model,according to the actual application scenarios of massive MIMO system,this model considers the geometric propagation of the base station without describing the specific location information of the users,thus greatly reducing the complexity of the channel model.(3)In view of the fact that the existing channel models only support uniform linear array or just one kind of antenna arrays,this paper changes the geometric structure of the antennas to model the massive MIMO system channel with different antenna configurations.Three popular antenna configurations,namely,uniform linear array,uniform circular array and uniform rectangular array,whose performances are analyzed and compared with measured data.(4)Aiming at the problem of the huge array of antennas in massive MIMO system and the lack of multi-polarized massive MIMO system channel modeling,this paper implements the polarization characteristic to massive MIMO system to improve space efficiency and establish three-dimensional multi-polarized massive MIMO system channel model.Also,the effects of antenna cross-polarization isolation,channel depolarization and antenna tilt on the system performance have been considered.By considering the random tilt of the user antenna and its polarization mismatch,this paper makes the model more suitable for the actual communication scenario.Then this paper changes the antenna configuration structure to establish different multi-user multi-polarized massive MIMO system schemes and channel models,and compares the simulation results with measured data.(5)The proposed model in this paper includes a variety of communication environment and antenna parameters,which also has low complexity and is easily adjusted according to the communication environment.The model can be used to simulate and study the polarization mismatch caused by the antenna tilt at the users' side,the cross-polarization isolation of antennas,and the depolarization of wireless mobile channel,which is not available in the existing massive MIMO system channel models.In view of the fact that the lack of performance comparison and analysis of multi-user multi-polarized massive MIMO systems with different antenna configurations,the effects of parameters on channel orthogonality,channel condition number and channel capacity are analyzed to adjust parameters to improve system performance.