Interference Mitigation for Visible Light Communications in Underground Mines Using Angle Diversity Receivers

Abstract

This paper proposes two solutions based on angle diversity receivers (ADRs) to mitigate inter-cell interference (ICI) in underground mining visible light communication (VLC) systems, one of them is a novel approach. A realistic VLC system based on two underground mining scenarios, termed as mining roadway and mine working face, is developed and modeled. A channel model based on the direct component in line-of-sight (LoS) and reflections of non-line-of-sight (NLoS) links is considered, as well as thermal and shot noises. The design and mathematical models of a pyramid distribution and a new hemi-dodecahedral distribution are addressed in detail. The performances of these approaches, accompanied by signal combining schemes, are evaluated with the baseline of a single photo-diode in reception. Results show that the minimum lighting standards established in both scenarios are met. As expected, the root-mean-square delay spread decreases as the distance between the transmitters and receivers increases. Furthermore, the hemi-dodecahedron ADR in conjunction with the maximum ratio combining (MRC) scheme, presents the best performance in the evaluated VLC system, with a maximum user data rate of 250 Mbps in mining roadway and 120 Mbps in mine working face, received energy per bit/noise power of 32 dB and 23 dB, respectively, when the bit error rate corresponds to 10 − 4 , and finally, values of 120 dB in mining roadway and 118 dB in mine working face for signal-to-interference-plus-noise ratio are observed in a cumulative distribution function.

A Visible Light Communication Channel Model for Agronomic Environments

“…Since LEDs are an artificial source of direct light, we initially present a mathematical model to calculate LEDs' illuminance. Therefore, to calculate this parameter, we define the luminous flux Q as the optical power that the human eye can receive in the following expression [15,16]:…”

“…where V (λ) is the sensitivity function of the human eye and S(λ) is the distribution of the radiation spectrum. The relationship between Q and the illuminance I(φ) on the PD is given by [15,16]…”

“…Assuming that each LED has the same generalized Lambertian radiation pattern, and since this model is widely used for the light emission distribution of the LEDs Figure 1 The geometry of the LoS and NLos propagation model in the agronomic greenhouse. [15,16], the radiation intensity pattern S(φ) is given as [15,16]…”

“…Therefore, the LoS link depends on LEDs and PDs parameters as seen above. The direct current (DC) gain of the LoS optical wireless channel is formulated by merging (1) and (5) as follows [15,16]:…”

Noise-Adaptive Visible Light Communications Receiver for Automotive Applications: A Step Toward Self-Awareness

“…However, after the initial purpose was mainly focused on providing record breaking wireless data rates, in the subsequent step, part of the efforts was focused on identifying new prospective applications. Thus, the VLC technology is envisioned for usage in a wide variety of applications such as device-to-device connections [ 4 ], internet of things applications [ 5 ], communications in underground mines [ 6 ], distance estimation [ 7 ], indoor localization [ 8 , 9 ], or even in intruder tracking [ 10 ].…”