A Study on Radio Propagation Channel Modelling for Tunnels

The tunnel environment is a semi-enclosed space, the electromagnetic wave propagation characteristics are very different from the typical outdoor and indoor environments. Propagation model of electromagnetic waves in tunnels plays an important role in designing advanced wireless communication systems. In this paper, we firstly establish narrowband channel model for the tunnel in Line-of-sight (LoS) and obstructed line-of-sight (OLoS) scenarios, such as the path loss model, small-scale fading model. Then, we analyze the power delay profile (PDP) and root-mean-square (RMS) delay spread in the tunnel. Results show that the PDP can be well modeled by a single exponential decay with a statistically distributed decay-time constant. In addition, it is shown that the generalized extreme value (GEV) distribution has better fit for the cumulative distribution function (CDF) of RMS delay spread than Lognormal distribution in LoS scenarios. In general, RMS delay spreads in LoS scenarios is smaller than OLoS scenarios.