Research On UAV Air-to-Ground Channel Modelling Based On Stochastic Geometry

Unmanned Aerial Vehicle(UAV)communication has been widely used in the fields of wireless coverage and communication because of its low cost and high flexibility,and thus becomes a new hotspot of wireless communication research.In order to design and evaluate the UAV wireless communication system effectively and reliably,it is of vital importance to describe the UAV air-to-ground channel accurately,and then establish an accurate,reliable and easy-to-use UAV air-to-ground channel model.In the absence of a large amount of measurement data for UAV air-to-ground channels,the geometry-based stochastic model(GBSM)helps to understand channel characteristics in depth and can provide a certain reference for channel measurement.However,most of the current UAV air-to-ground GBSM do not completely analyze the spatial characteristics of the corresponding scattering areas when the signal arrives at the UAV and the ground station,nor do they derive the corresponding probability density function of the angle of arrival.Therefore,this thesis proposes a three-dimensional air-to-ground channel model based on cylinder geometry to describe the UAV scattering environment.The probability density functions of the angles of arrival and departure are derived in detail,and then the spatial-temporal correlation characteristics of the channel are studied and analyzed based on the obtained probability density functions.Specifically,the main work of this thesis includes:(1)A geometry-based stochastic model for UAV air-to-ground channel is proposed,which assumes that the scatterers around the ground station are distributed in a cylinder.Then,to cope with the problem that the distribution assumptions of the angles of arrival and departure in existing UAV air-to-ground channel models are too ideal to describe the spatial statistical property of the corresponding propagation environment precisely,the spatial geometric characteristics of scattering regions are investigated analytically as corresponding to the angles of arrival and departure in both elevation and azimuth planes,which are further used to derive the probability density function of the distribution of each angle.Finally,the influence of various parameters on probability density function is studied by simulation.(2)Based on the proposed UAV air-to-ground channel model and the derived spatial angle distribution characteristics,the spatial-temporal statistical characteristics of the channel model are further derived,that is,the spatial-temporal correlation functions(STCF)in the case of uniform distribution and Gaussian distribution of scatterers.Then the influence of various channel environment parameters on the spatial-temporal correlation function of the channel is analyzed through simulation,and the results can provide a theoretical reference for the design and performance evaluation of the UAV communication system.