The Prediction Of Propagation Based On Ray Tracing

With the rapid development in personal communication technology, the microcell covering range is becoming smaller and smaller in order to accommodate more users with limited resource of frequency. In this kind of mobile communication systems, the height of transmitter and receiver are always lower than the surrounding buildings. And it makes the traditional propagation prediction models for macrocells can not be used any more. Accordingly ray tracing model for microcells propagation prediction has become an important subject.This paper discussed the characteristic of propagation in symmetrical atmosphere on the earth, and introduced several kinds of traditional path loss propagation model in land mobile communication system, also pointed out the localization of these models based on experiential methods. With that, emphases were be put on the basic principle,methods and its advantages in the study on the characteristic of the microcell based on ray tracing method of determinate analysis means.A quasi-three-dimensional propagation model has been presented for path-loss prediction in a typical urban site, based on ray tracing with quad-tree method of subarea. The model takes into account numerous rays that undergo reflections from ground and wall surfaces and diffraction from corners or rooftops of buildings. The exact location of reflection and diffraction points is essential in order to calculate the polarization components of the reflected and diffracted fields and their trajectories. Then, a vector addition of the received fields is carried out to obtain the total received field strength and, subsequently, the path loss along a predetermined route. The model computes the contributions of various categories of rays, as selected, in a flexible manner. It can be used in any complex environment except rotunda. Finally, an instance is given, and comparisons with measured data are presented.