Study On Ray Tracing Algorithm For Radio Propagation In Urban Microcell Based On Preprocessing Technique Of Digital Map

Ray-tracing and uniform theory of diffraction techniques are already widely applied to site-specific radio propagation modeling for wireless applications. In view of the fact that the digital map of the urban microcellular is important to the ray tracing algorithm for mobile communications and taking into account the characteristic of the quasi three-dimension ray-tracing algorithm. The technology of extracting geometrical information of buildings and preprocessing the digital map has been proposed.This technology can extract geometrical information of buildings with high precision and speed,and contribute to eliminate geometrical factors which have little influence on prediction results, then reduce computation time. Therefore, a microcellular wave propagation prediction model with the advantages of practicality, high speed and high accuracy. Thus, the accuracy and efficiency of the microcellular wave propagation prediction model have been improved.A novel quasi 3-D ray-tracing model by considering the advantages of both the image theory and shooting-and-bouncing ray methods has been presented. This new model is based on preorder-creating a new visibility virtual source tree together with modified polar sweep algorithm and balanced binary tree. As it is fundamentally a point-to-point ray tracing method and efficient acceleration techniques are introduced, all possible ray paths in the environment microcell can be found and the reduction of the numbers of intersection calculation can also be achieved. Meanwhile, the proposed method can avoid memory leaks and increase the accuracy of the prediction. Our theoretical results of the signal path loss along the streets are compared with those measurements which have been reported for city streets in Ottawa for various values of the propagation parameters. The good agreement with these measurements indicates that our prediction model works well for such microcellular environments. The proposed method can provide the reliable theory basis for radio-wave propagation prediction and network palnning in urban microcellular environments.