Research On Non-stationary Channel Model For Unmanned Aerial Vehicles MIMO Communication Systems

With the rapid development of wireless communication technology,Unmanned aerial vehicle(UAV)has been applied in military,agricultural and daily life in various aspects,UAV communication link research has become a research hotspot.The characteristics of communication link determine the performance of UAV communication system,such as transmission capacity,bit error rate,throughput,etc.During UAV operation,due to the interaction of direct,reflection and scattering of electromagnetic waves,the communication system quality is often not guaranteed due to the influence of obstacles and its own movement.Multiple input multiple output(MIMO)technology can realize space division multiplexing.Configuring MIMO technology on UAV can not only improve the channel capacity of the system,but also improve the data transmission rate.Channel model is the basis of accurate description of signal propagation characteristics and system performance analysis.Therefore,it is very important to establish appropriate UAV channel model for UAV-MIMO communication system application.Because of the moving characteristics of UAV,scatterer and TMS,the propagation characteristics of UAV-MIMO channel is a non-stationary process.In order to accurately describe the propagation properties of UAV channel in the real environment,it is necessary to study the non-stationary UAV-MIMO channel model.This paper studies the time-varying propagation characteristics of the UAV-MIMO channel(such as time-varying distance parameter,time-varying azimuth and time-varying elevation parameter).A three-dimensional(3-D)non-stationary UAV-MIMO channel model is proposed,including the 3-D UAV-MIMO channel model based on spherical wave and flat wave.This paper mainly does the following work:(1)A non-stationary 3-D UAV-MIMO channel model based on plane waves assumptionFirstly,considering the far-field effect of the scatterers,a non-stationary 3-D UAV-MIMO channel model based on the plane waves assumption is proposed in this paper.Considering the stationary scatterers and moving scatterers,and that the moving scatterers and TMS have the similar height,three-dimensional(3-D)cylinder and two-dimensional ring are used to simulate the stationary and moving scatterers,respectively.In order to describe the random distribution characteristics of the moving scatterer,this paper assumes that the moving scatterers are non-uniform distributed in the 2-D ring;Secondly,considering the motion direction and velocity of UAV,scatterer and TMS to the effect of propagation characteristics of 3-D UAV-MIMO channel,the non-stationary properties of proposed UAV-MIMO channel model are described by time-varying parameters,such as time-varying distance between the receiver and the scatterer,time-varying departure azimuth,time-varying elevation and time-varying Doppler frequency;Finally,the space-time correlation function of the proposed channel model is obtained,and the influence of the dynamic characteristics of the scatterer on the statistical characteristics of the proposed channel model is analyzed in detail,and the rationality of the proposed channel model is verified by the measurement data.(2)A non-stationary 3-D UAV-MIMO channel model based on spherical waves assumptionConsidering the near-field effect of scatterers,a non-stationary 3-D UAV-MIMO channel model based on spherical waves assumption is proposed in this paper.Firstly,considering the stationary and moving scatterers around TMS,the surface area of 3-D cylinder and 3-D sphere is used to describe the stationary and moving scatterers.In this paper,the azimuth and elevation angles of scatterers are assumed to be independent of each other,and von Mises probability density function(PDF)and Laplacian PDF are used to describe the distribution of azimuth and elevation;Secondly,in order to accurately describe the non-stationary characteristics of 3-D UAV-MIMO channel,this paper uses 3-D vector form to describe the time-varying distance,azimuth and elevation parameters between UAV and TMS;Finally,the space-time correlation function of the proposed channel model is obtained to verify the proposed 3-D The effectiveness of the UAV-MIMO channel model,this paper uses the spatial correlation function of the 3-D UAV-MIMO channel model and the comparison of the measured data,the numerical results show that the proposed channel model can more truly describe the actual propagation environment of the 3-D UAV-MIMO channel.Based on the comparative analysis of data,the two non-stationary channel model assumptions proposed in this paper can describe the 3-D UAV-MIMO channel model more realistically.