A path loss channel model for visible light communications in underground mines

Due to the ability to support communication and illumination simultaneously, visible light communication (VLC) system is considered as a potential access to realize effective communication in underground mines. In order to achieve this goal, it is necessary to understand the underlying physical propagation phenomenon in underground mines. Accurate and efficient channel models including large-scale fading characteristics are crucial for the design and performance evaluation of VLC systems. However, the characteristics of the underlying VLC channels have not been sufficiently investigated yet. In this paper, based on the recursive channel model, a path loss channel model is proposed precisely with the path loss exponent determined by three different trajectories in the mining roadway and working face environments. Taking different numbers of transmitters into account, both line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios are considered. Our results demonstrate that the path loss exhibits a linear behavior in log-domain when curve fitting technique is applied. An expression for path loss as a function of distance is derived. Finally, root mean square (RMS) delay spread has been investigated and analyzed.