A Hybrid VLCRF Portable Phasor Measurement Unit for Deep Tunnels In this manuscript we propose a hybrid Visible Light Communication and Radio Frequency (VLCRF) scheme for the implementation of a portable Phaser Measurement Unit (PMU) for deep underground tunnels. Through computer simulations and laboratory measurements we are capable of providing Coordinated Universal Time (UTC) to the PMUs, as well as high accuracy positioning in a Global Positioning System (GPS) denied environment. The estimated PMU position, time stamp, and electrical power system measurements are sent to a central monitoring station using a radio frequency uplink with a data rate of hundreds of Kbps. Simulations and experimental measurements show that the proposed scheme can be used to control a large number of VLCRF PMU devices inside a tunnel. The tests demonstrate the viability of the hybrid prototype, which will improve performance compared to commercial PMUs that lack these features.

Interference Mitigation for Visible Light Communications in Underground Mines Using Angle Diversity Receivers This paper proposes two solutions based on angle diversity receivers (ADRs) to mitigate intercell 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 lineofsight (LoS) and reflections of nonlineofsight (NLoS) links is considered, as well as thermal and shot noises. The design and mathematical models of a pyramid distribution and a new hemidodecahedral distribution are addressed in detail. The performances of these approaches, accompanied by signal combining schemes, are evaluated with the baseline of a single photodiode in reception. Results show that the minimum lighting standards established in both scenarios are met. As expected, the rootmeansquare delay spread decreases as the distance between the transmitters and receivers increases. Furthermore, the hemidodecahedron 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 bitnoise power of 32 dB and 23 dB, respectively, when the bit error rate corresponds to     10  xe2x88x92 4     , and finally, values of 120 dB in mining roadway and 118 dB in mine working face for signaltointerferenceplusnoise ratio are observed in a cumulative distribution function.