Abstract
Underground mining is an industry that preserves the miners' safety and efficiency in their work using wireless communication systems as a tool. In addition to communication links characterized by radio frequency signals, optical links in the visible light spectrum are under intense research for underground mining applications due to their high transmission rates and immunity to electromagnetic interference. However, the design of a robust visible-light communication (VLC) system for underground mining is a challenging task due to the harsh propagation conditions encountered in mining tunnels. To assist researchers in the design of such VLC systems, we present in this paper a novel channel model that incorporates important factors that influence the quality of the VLC link in underground mines. Features such as an arbitrary positioning and orientation of the optical transmitter and receiver, tunnels with irregular walls, shadowing by large machinery, and scattering by dust clouds are considered. These factors are integrated into a single modeling framework that lends itself for the derivation of compact mathematical expressions for the overall DC gain, the impulse response, the root mean square delay spread, and the received power of the proposed VLC channel model. Our analytical results are validated by computer simulations. These results show that the rotation and tilt of the transmitter and receiver, as well as the tunnels' irregular walls have a notorious influence on the magnitude and temporal dispersion of the VLC channel's line of sight (LoS) and non-LoS components. Furthermore, results show that shadowing reduces the LoS component's magnitude significantly. Our findings also show that scattering by dust particles contributes slightly to the total VLC channel gain, although it generates a large temporal dispersion of the received optical signal.
Highlights
The inherent working environment of underground mines is considered as very dangerous and unsafe due to inherentssThe associate editor coordinating the review of this manuscript and approving it for publication was Qiong Wu.characteristics of the tunnels [1], as well as numerous external agents generated by regular mine operation such as dust, toxic components, sewage water, among others [2]
Based on an extensive review of the state of art, and in an effort to design better underground mining communication systems, we present a visible-light communication (VLC) channel model that considers physical features that will have an effect in mining tunnels
PROPOSED STATISTICAL SHADOWING MODEL Based on the work presented in [30], we statistically model the entry of obstructions into the underground mining environment and, the shadowing produced considering the following statistical assumptions: (1) We assume that there are not obstructions in the scenario at the beginning time
Summary
There are several studies on the effect of scattering and shadowing in typical VLC indoors environments, in the authors’ opinion, these phenomena have not been widely and properly analyzed in underground mining environments In this context, only a few VLC channel modeling manuscripts for underground mines consider blocking and dust particles. In contrast to the studies reported in the literature, we included in the mathematical expressions of the LoS and non-LoS components of the proposed underground mining VLC channel model a weighting function to adequately describe the shadowing effect This function is based on a Poisson process [30], which randomly describes the entry of objects in the underground mining VLC environment.
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