Based On The Ray Tracing Method Of Arbitrary Shape Tunnel Field Intensity Forecast Method Research

Since fast and accurate estimation of the characteristics of wave propagation is fundamental to the design of wireless communication network, research of this area has been paid more and more attention in these years. Specifically, the propagation characteristic in the tunnel is very unique.It’s hard to get the accurate result in arbitrarily shaped tunnels for traditional method. An improved method, Ray Density, based on Geometric Optical and Ray Tracing is proposed to overcome the shortcomings of traditional ways in these applications. Instead of trying to avoid the existence of multiple rays, it is a priori assumed that several multiple (or dependent) rays are present on each physical propagation path. After that, the divergence transfer factor can be denoted by ray density. The magnitude of electromagnetic power can be denoted by the sum of all the p0wer components which can be received by the antenna.The main purposes of this paper are modeling the radio wave propagation in tunnels, as well as studying the characteristics of millimeter radio wave propagation in subway tunnels by simulations and experimentations. To conquer the disadvantages of traditional ray tracing, a concept of Ray Density is introduced. This method gives birth to a new simulation program which is written by C++. The model of tunnel was built in C++environment. Besides, the "classes" which would be used in the model were built. By the simulation program, the propagation characters of electromagnetic field in the tunnel can be analyzed. The simulation result was compared with the measurement of the9th tunnel in ShangHai to prove the new method. And the transmission power distribution of38GHz EM field along the tunnel is obtained by applying the verified algorithm to a mixed type tunnel.