Channel Modeling of Wireless Networks in Tunnels

The propagation characteristics of electromagnetic (EM) waves in tunnels are significantly different from those in terrestrial environment. However, the current tunnel channel models cannot provide an analytical solution for both near and far region of the sources. In this paper, the Multimode model is proposed to completely characterize the wireless channel of tunnels in roads/subways as well as underground mines. The new model provides an analytical expression for the path loss and delay spread at any position in a tunnel. This theoretical model is validated by comparing results with experiment measurements. Our channel model reveals that: the mode attenuation is mostly determined by the tunnel size and operating frequency, while the mode intensity is governed by the position of the transmission antenna. Physical factors, such as, humidity, pressure and temperature of the tunnel air, as well as the material of tunnel walls have little influence on the signal propagation in tunnels.