Study On The Prediction Of Characteristics Of Radio Wave Propagation In The Complex Land/Ocean Environments With Large Area

In recent years,with the rapid development of wireless communication technology,the research of radio wave propagation in complex electromagnetic environment has become a very important topic,attracting the extensive attention of scholars at home and abroad.The existing research methods on the characteristics of radio wave propagation mainly include theoretical research,experimental observation and numerical simulation,but a complete and comprehensive radio wave propagation estimation system has not yet been formed.Therefore,it is very important to establish an effective propagation model and predict the characteristics of radio wave propagation in the complex land/ocean environments with large area.In the prediction of radio wave propagation in indoor and outdoor cellular scenes,the empirical model usually has low accuracy because it cannot consider the specific information of propagation environment.As a deterministic algorithm,ray tracing(RT)combines geometrical optics and the uniform theory of diffraction.Through the calculation of multipath,it can give the information of received field strength,time delay and arrival angle.It has become an alternative tool of traditional empirical model and is widely used.However,in RT model,it is usually difficult to deal with the undulating terrain.Therefore,in this dissertation,the parabolic equation(PE)method will be used to solve the problem of wave propagation over irregular terrain.Compared with the existing radio wave propagation model,the PE method itself can reflect the refraction and diffraction effect of radio wave propagation,and fully consider the influence of complex environment such as irregular surface structure and inhomogeneous medium on radio wave propagation.Therefore,it is very suitable for solving the radio wave propagation characteristics in the environment such as undulating terrain and atmospheric waveguide above the sea surface.In this dissertation,a reasonable scene modeling is carried out for a large area of land-ocean environment,and based on RT method and PE method,the problem of radio wave propagation in complex scenes is studied.The main research works are as follows:1.The map modeling method,path search algorithm and the calculation of diffraction in RT model are improved,and on this basis,the radio wave propagation problems in outdoor,single room and multi-floor indoor scenarios are studied respectively.Based on the principle of virtual source tree,a new algorithm for searching ray paths is proposed,and according to the improved diffraction coefficient,the higher-order diffraction field and the continuous diffraction field are solved.In the outdoor scene,the map modeling method is improved,and the digital elevation map is used to model the buildings and vegetation in the scene,which solves the disadvantage that non cylindrical object cannot be modeled in traditional maps.Considering the specific characteristics of the environment,a reasonable and efficient storage standard of indoor database is designed for single room and multi-floor scenes.In addition,the power coverage in different floors is also studied,which provides a new idea and reference for the problem of radio wave propagation in the multi-floor indoor environment.2.By using different approximation methods,the 2D narrow angle and wide angle PE models are established respectively,and the key steps and specific processes of numerical solution are given as well as the correctness of the model is verified by comparing with other models.Besides,the existing terrain processing algorithms are given,and a hybrid terrain method is proposed,which can be applied to the actual terrain processing.Furthermore,the propagation characteristics of radio wave in complex land-ocean environment is studied and the influence of offshore islands,coastal cities,evaporation ducts and other factors on radio wave propagation is analyzed,which provides a theoretical reference for the application of marine radar detection.3.From the 3D wave equation,the 3DPE is derived,and the detailed solution method and key steps are given.The correctness of the model is verified by comparing the simulation results with other models in the lossy flat ground scenario and the knife edge scenario.A new processing method for 3D irregular terrain is proposed,and then the 3D Gauss undulating terrain and the real terrain are simulated respectively,and the results are compared and verified with the 2D model.In addition,in the 3D urban environment,the boundary conditions for vertical and oblique incidence of electric waves on the building surface are derived.The simulation is carried out for PEC and lossy media respectively,and the simulation results are compared and analyzed with the measured data.4.The modeling of 3D marine troposphere environment and the prediction of radio wave propagation in atmospheric duct under this environment are studied.Firstly,the 3D model of atmospheric refractive index is established,and the generation and storage method of 3D rough sea surface is given.On this basis,the propagation characteristics of radio wave in the atmospheric waveguide on the smooth sea surface and rough sea surface are simulated and analyzed.By changing different simulation conditions,the effects of frequency,wave,wind speed and waveguide height on the propagation in the atmospheric waveguide are analyzed.5.The acceleration method of 3DPE model is studied.CPU parallel acceleration is realized by using Open MP,and the trend of acceleration performance with the number of CPU threads under different solving complexity is analyzed.In addition,according to the characteristics of the 3DPE model itself,combined with CUDA platform,an algorithm suitable for GPU parallel is designed,and the performance comparison and analysis under different thread parameters are given.