Study On The Prediction Of Wireless Coverage In Irregular Terrain By The Ray Tracing

Ray tracing is a technology that is widely applied in mobile communication for predicting the propagation characteristics of wireless radio wave.In this paper,terrain modeling methods,the prediction of wireless coverage in irregular terrain with different mesh sizes and acceleration methods of ray tracing in irregular terrain are mainly studied based on the ray tracing algorithm and the digital elevation model(DEM).First,methods for terrain modeling and the realization of ray tracing algorithm in irregular terrain are studied.A triangular network model for terrain based on the DEM is built for electromagnetic simulation.On this foundation,the effect of different mesh sizes on the prediction accuracy and the simulation time is analyzed.In addition,to improve the speed of simulation,methods for irregular terrain dynamic modeling according to multi-resolution triangular mesh are studied further.The aim of this paper is to establish a fast and accurate ray tracing propagation model for irregular terrain environment.The main works of the paper are as follows: 1.The image method and an efficient algorithm of ray-triangle intersection are used for finding reflected paths in irregular terrain environment.Based on this,an acceleration method of tracing effective paths is studied.What is more,the procedure of the ray tracing algorithm is described.2.Terrain modeling methods and building modeling methods are studied.The data format and modeling idea of DEM and traditional digital map are analyzed,and then the DEM is used for building the model of terrain.Besides,the algorithm of converting the traditional digital map into the DEM is given.Furthermore,terrain modeling based on the triangular grid digital elevation model is finished.Computer algorithms are employed to extract and interpolate the DEM data,so as to generate the regular triangular grids.Then the terrain can be showed by a large number of connected triangles for ray tracing electromagnetic simulation.3.In order to analyze the effect of different modeling precision on the wireless coverage,three different mesh sizes of the terrain model: bilinear interpolation grids,original data grids and large grids are created based on the DEM,and then simulation was performed based on the ray tracing algorithm in the irregular terrain scenario.4.To improve the speed of simulation,methods for terrain dynamic modeling according to multi-resolution triangular mesh are studied.The main idea is to mesh the area with dramatic fluctuation into fine triangles while the flat area into larger triangles.The number of triangular patches is reduced by this method while the basic features of terrain is maintained.Through analysis of the calculation accuracy and time under different thresholds,the most appropriate threshold value is found.Moreover,according to the position of the sources and the receivers,to mesh the main transmission area into fine triangles while other areas into larger triangles.According to the results,the simulation speed of these developed methods is increased by 80% while maintaining the accuracy.