Study On Ray Tracing Algorithm In Microcellular Wave Propagation Prediction

As the demand for cellular radio services has increased dramatically in recent years, new cellular systems are needed to accommodate much more users. This has resulted in the development of microcellular systems. The successful implementation of these systems requires the exact understanding of electromagnetic wave propagation mechanism such as path loss and delay spread characteristics. Uniform geometrical theory of diffraction and ray tracing techniques are often employed as a theoretical prediction model to characterize the microcell propagation. For this purpose, a propagation prediction model based on a new ray tracing algorithm, which can predict propagation characteristics for various microcellular environments, is proposed in this paper. The main works are as follows:1. The principle of ray tracing algorithm, which includes the uniform geometrical theory of diffraction and electromagnetic theory, is comprehensively analyzed. Meanwhile, the theory of electric field calculation is also presented in this paper.2. Propagation models based on ray tracing techniques can be classified into two categories: image concept and “brute force” ray tracing. The basic principle for those two algorithms and the advantages or disadvantages of them are discussed in detail.3. A fast ray tracing algorithm, which is based on uniform geometrical theory of diffraction, is presented and overcome the disadvantage by the other ray tracing method. It can be applied to any complex propagation environment. All propagation paths from a transmitter to a receiver can be found extensively with very high computation efficiency. Our proposed method is a point-to-point tracing method, so reception tests are not required and can guarantees high accuracy.4. Acceleration techniques of ray tracing are the most concerned problems in the field of ray tracing. In this paper, the methods for speeding up ray tracing mainly aim at reducing the size of the input database and the number of rays to be handled. Hence, a great computation time can be reduced without sensibly affecting the accuracy of the prediction.