City Environment Radiation Modeling Based On The Uniform Theory Of Diffraction

The uniform geometrical theory of diffraction and ray tracing together constitute a high-precision modeling method for radio propagation in wireless communication systems.This paper uses image method of ray tracing to search point-to-point paths,and employs GO and UTD to calculate the electric field at the receiving point.The wave propagation analysis and wireless channel path loss calculation of the urban environment are completed.The main works of this dissertation include:1.Ray optical representation of high frequency electromagnetic field and geometrical optics reflection law are derived in detail.The expression of the geometrical optical reflection field is established and the GTD and UTD are introduced exhaustively.The image method is introduced and extended which is able to apply to GTD or UTD.Some examples show accurations of ray tracing and field calculation.2.The space volumetric partitioning(SVP)of ray tracing acceleration method is studied deeply and the octree structure is used to optimized the SVP.In this paper,bottom-up approach is used to achieve the finding octree neighborhood nodes in the ray tracing process.3.A reverse ray tracing algorithm based on the mirror source tree is implemented.From the perspectives of graphics and electromagnetism,the optimization methods of mirror source tree are designed,such as backcrossing,occlusion culling and reflection visible area,diffraction visible area.The paths of multiple reflections and ones including diffraction or ground reflection are searched.4.In order to verify the correctness of the wave propagation model realized in this paper,taking the typical urban environments as examples,the results of this paper compare with the FEKO and measurements respectively and they are in good agreement,if taking into account the randomness of the environments.The modeling method of this paper can provide the basis for the prediction of radio propagation and network planning in urban environments.