Research Of Wave Propagation Characteristic In Curved Tunnel Based On Ray Tracing Simulation

People’s demands of spiritual and physical are higher and higher as high-speed economic development in society. Improving communication and optimizing user’s experience is an inevitable trend, and it has been the goal that people want to reach all the time.The rapid expansion of city means more and more people coming into big cities, so traffic pressure has been an eternal topic. The use of subway, high-speed rail and other confined space greatly eases the traffic congestion and creates a convenient and efficient way for people’s life. In the field of communication, confined space is different from open space. The properties of radio wave propagation in confined space have been changed. So figuring out the characteristics of radio wave propagation in curved tunnel is the main purpose of this paper. For decades, there have been some scholars to study the characteristics of wave propagation in straight tunnels and they have worked out very important theories and models. But the research of the characteristics of wave propagation in curved tunnel is still not enough. Therefore, the propagation characteristics in curved tunnel are the emphases in this paper. Path loss generated by wave propagation in curved tunnel is larger than that generated by radio wave propagate in straight tunnel. The innovation of this paper is extraction, analysis and modeling the extra loss of wave propagation in curved tunnels.The main work in this paper is as follows:(1) Obtain desired data by simulation of different cross-sections of tunnels such as rectangular cross-section tunnel, arched cross-section tunnel (’Type1tunnel’in this paper) and the horseshoe cross-section tunnel (Type2tunnel’in this paper). At the same time, different transmission frequencies, Rx locations in tunnels and radius of curved tunnels have been simulated to provide data for the following research.(2) Calculate loss exponent with the obtained simulation data to explore the influence of different factors on loss exponent which is generated by the radio wave propagation in tunnels. Some conclusions are as follows:the smaller the radius of the curved tunnel, the larger the loss exponent, that means waveguide effect has been decreased by curved tunnel; the higher the tunnel’s radius of curvature, the higher the loss exponent; besides, this paper talks about the influence of Rx location and cross-section of the tunnel. (3) Calculate extra loss with the obtained simulation data to explore the different influence of different factors on extra loss in curved tunnels. Extra loss is a relative concept, which is the difference between path loss in curved tunnel and path loss in straight tunnel. According to the observed properties of extra loss, analysis by stages is proposed to promote the accuracy of extra loss modeling. And there are three stages in the whole distance of tunnel. Some conclusions are as follows:in the first and second stage, the higher the frequency, the larger the extra loss, but in the third stage, the character is different; besides, the bigger the tunnel’s radius of curvature, the smaller the extra loss; in this part, the paper also found that the extra loss which in the environment of Rx located near the inner wall of curved tunnel is larger than that in the environment of Rx located near the outer wall of curved tunnel in the second and third stage, but in the first stage, the character is opposite.In summary, this paper builds a radio wave propagation model for different types of curved tunnels in theory and provides a precise guidance for the network design of curved tunnels in engineering application...