Modeling the influence of wall roughness on tunnel propagation

Abstract

At the ultra-high frequencies (UHF) common to portable radios, a mine tunnel is often modeled as a hollow dielectric waveguide. The roughness condition of the tunnel walls has an influence on radio propagation and therefore should be taken into account when accurate power predictions are required. In this paper, we derive a general analytical formula for modeling the influence of the wall roughness. The formula can model practical tunnels formed by four dielectric walls, with each having an independent roughness condition. It is found that different modes are attenuated by the same wall roughness in a different way, with higher order modes being significantly more attenuated compared to the dominant mode. The derivation and findings are verified by numerical results based on both ray tracing and modal methods.

Modeling and measurement of wireless channels for underground mines

“…It is known that these fast fluctuations are caused by multiple modes interacting with each other. The observation that the measured power decay profiles are smoother than the corresponding simulation results can be explained by the roughness effect investigated in [6]. It should be noted that for simplicity, surface roughness has not been considered in the simulated results shown in Fig.…”

“…2. Based on the analytical roughness model given in [6], simulations were revised by adding a Root Mean Square (RMS) roughness of 10 cm to each surface. A comparison of the simulation results with and without surface roughness at 2.45 GHz is shown in Fig.…”

Measurement and modeling of radio propagation from a primary tunnel to cross junctions

“…Radio propagation in tunnel environments such as underground mines has gained renewed interest [1][2][3], partially due to the Mine Improvement and New Emergency Response Act (MINER Act) of 2006, which requires all US underground coal mines to install communications and tracking systems [4]. Most of the published work, however, has focused on the line-of-sight (LOS) propagation scenario where the tunnel is straight and there are no obstructions between the transmitter and the receiver.…”

“…In this paper, we extend the modal method that has been successfully used for predicting power distribution in straight tunnels [2,3] to model around-corner coupling in underground mines. The uniform theory of diffraction (UTD) is used to calculate mode coupling coefficients from a main tunnel to cross-cut tunnels (cross junctions).…”