Simulation of Radio Wave Propagation in Arched Cross-section Tunnels

Since several years, wireless communication systems are developed for train to infrastructure communication needs related to railway or mass transit applications. The systems should be able to operate in specific environments like tunnels. In this context, specific radio planning tools have to be developed to optimise system deployment. Realistic tunnels geometries are generally of rectangular cross-section or arched shape. Furthermore, they are mostly curved. In order to calculate electromagnetic wave propagation in such tunnels, specific models have to be developed. Several works dealt with retransmission of GSM or UMTS [1], [2]. Few theoretical or experimental works focused on 2.4 GHz or 5.8 GHz bands. In this paper, we will propose an approach to model radio wave propagation in these frequency bands in arched shape crosssection straight tunnels using tessellation in multi-facets. The model will be based on a Ray-Tracing tool using images method. Work reported in this paper will also show the propagation loss variations according to the shape of tunnels. A parametric study on the size of facets to model the cross-section will be realized. Finally, the influence of some parameters like the dimensions of tunnels and the frequency of signals will be examined.