Research

21 pages, 3942 KiB

Open AccessArticle

Noise Resilient Outdoor Traffic Light Visible Light Communications System Based on Logarithmic Transimpedance Circuit: Experimental Demonstration of a 50 m Reliable Link in Direct Sun Exposure

by Sebastian Andrei Avătămăniței, Alin-Mihai Căilean, Adrian Done, Mihai Dimian and Marius Prelipceanu

Sensors 2020, 20(3), 909; https://doi.org/10.3390/s20030909 - 08 Feb 2020

Cited by 22 | Viewed by 3172

Abstract

The usage of Visible Light Communications (VLC) technology in automotive applications is very promising. Nevertheless, in outdoor conditions, the performances of existing VLC systems are strongly affected by the sun or other sources of light. In such situations, the strong parasitic light can [...] Read more.

The usage of Visible Light Communications (VLC) technology in automotive applications is very promising. Nevertheless, in outdoor conditions, the performances of existing VLC systems are strongly affected by the sun or other sources of light. In such situations, the strong parasitic light can saturate the photosensitive element and block data communication. To address the issue, this article analyzes the usage of an adaptive logarithmic transimpedance circuit as an alternative to the classical linear transimpedance circuit. The simulation and experimental evaluation demonstrate benefits of the proposed technique, as it significantly expands the communication distance and optical noise functionality range of the VLC systems and reduces the possibility of photoelement saturation. As a result, this approach might enable outdoor VLC sensors to work in strong sun conditions, the experimental results confirming its validity not only in the laboratory but also in outdoor conditions. A reliable 50 m communication distance is reported for outdoor sunny conditions using a standard power traffic light VLC emitter and a PIN photodiode VLC sensor. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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17 pages, 2619 KiB

Open AccessArticle

A Hybrid VLC-RF Portable Phasor Measurement Unit for Deep Tunnels

by Ismael Soto, Rafael Nilson Rodrigues, Gabriel Massuyama, Fabian Seguel, Pablo Palacios Játiva, Cesar A. Azurdia-Meza and Nicolas Krommenacker

Sensors 2020, 20(3), 790; https://doi.org/10.3390/s20030790 - 31 Jan 2020

Cited by 8 | Viewed by 3086

Abstract

In this manuscript we propose a hybrid Visible Light Communication and Radio Frequency (VLC-RF) 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 [...] Read more.

In this manuscript we propose a hybrid Visible Light Communication and Radio Frequency (VLC-RF) 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 VLC-RF 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. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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Graphical abstract

15 pages, 13877 KiB

Open AccessArticle

Experimentally Derived Feasibility of Optical Camera Communications under Turbulence and Fog Conditions

by Vicente Matus, Elizabeth Eso, Shivani Rajendra Teli, Rafael Perez-Jimenez and Stanislav Zvanovec

Sensors 2020, 20(3), 757; https://doi.org/10.3390/s20030757 - 30 Jan 2020

Cited by 23 | Viewed by 2946

Abstract

Optical camera communications (OCC) research field has grown recently, aided by ubiquitous digital cameras; however, atmospheric conditions can restrict their feasibility in outdoor scenarios. In this work, we studied an experimental OCC system under environmental phenomena emulated in a laboratory chamber. We found [...] Read more.

Optical camera communications (OCC) research field has grown recently, aided by ubiquitous digital cameras; however, atmospheric conditions can restrict their feasibility in outdoor scenarios. In this work, we studied an experimental OCC system under environmental phenomena emulated in a laboratory chamber. We found that the heat-induced turbulence does not affect our system significantly, while the attenuation caused by fog does decrease the signal quality. For this reason, a novel strategy is proposed, using the camera’s built-in amplifier to overcome the optical power loss and to decrease the quantization noise induced by the analog-digital converter of the camera. The signal quality has been evaluated using the Pearson’s correlation coefficient with respect to a reference template signal, along with the signal-to-noise ratio that has been empirically evaluated. The amplification mechanism introduced allows our system to receive the OCC signal under heavy fog by gradually increasing the camera gain up to 16 dB, for meteorological visibility values down to 10 m, with a correlation coefficient of 0.9 with respect to clear conditions. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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12 pages, 2200 KiB

Open AccessArticle

A Low-Cost IEEE 802.15.7 Communication System Based on Organic Photodetection for Device-to-Device Connections

by Pablo Corral, Fernando Rodríguez-Mas, José Luis Alonso, Juan Carlos Ferrer and Susana Fernández de Ávila

Sensors 2020, 20(3), 714; https://doi.org/10.3390/s20030714 - 28 Jan 2020

Cited by 5 | Viewed by 2914

Abstract

In this article, we compare two different kinds of commercial light-emitting diodes (LEDs) in transmission and organic photodetectors based on poly(3-hexylthiophene) (P3HT) and a phenyl-C61-butyric acid methyl ester (PCBM) blend used as active layer in reception. Photovoltaic cells based on massive heterojunctions of [...] Read more.

In this article, we compare two different kinds of commercial light-emitting diodes (LEDs) in transmission and organic photodetectors based on poly(3-hexylthiophene) (P3HT) and a phenyl-C61-butyric acid methyl ester (PCBM) blend used as active layer in reception. Photovoltaic cells based on massive heterojunctions of semiconductor polymers have focused the attention of researchers due to their several potential advantages over their inorganic counterparts, such as their simplicity, low cost, and ability to process large area devices, even on flexible substrates. Furthermore, in logistics, storage management systems require the implementation of technological solutions that allow the control of merchandise in real time by means of light-emitting diode signals that send information about the product. However, the slow response time of these organic photodetectors should not be critical for this application, where the light intensity changes are very slow, which limits the speed of data transmission compared to inorganic based systems that use wireless optical communications. Finally, we show a low-cost visible light communication system based on organic photodetectors with a frame based on on-off keying with Manchester encoding to support device-to-device connections. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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16 pages, 7488 KiB

Open AccessArticle

Investigation of 3 dB Optical Intensity Spot Radius of Laser Beam under Scattering Underwater Channel

by Wei Wang, Xiaoji Li, Sujan Rajbhandari and Yanlong Li

Sensors 2020, 20(2), 422; https://doi.org/10.3390/s20020422 - 11 Jan 2020

Cited by 4 | Viewed by 2280

Abstract

An important step in the design of receiver aperture and optimal spacing of the diversity scheme for an underwater laser communication system is to accurately characterize the two-dimensional (2D) spatial distribution of laser beam intensity. In this paper, the 2D optical intensity distribution [...] Read more.

An important step in the design of receiver aperture and optimal spacing of the diversity scheme for an underwater laser communication system is to accurately characterize the two-dimensional (2D) spatial distribution of laser beam intensity. In this paper, the 2D optical intensity distribution and 3 dB optical intensity spot radius (OISR) are investigated due to the dominating optical intensity of laser beam being within the 3 dB OISR. By utilizing the Henyey–Greenstein function to compute the scattering angles of photons, the effects of the scattering underwater optical channel and optical system parameters on 3 dB OISR are examined based on the Monte Carlo simulation method. We have shown for the first time that in the channel with a high density of scattering particles, the divergence angle of the laser source plays a negligible role in 3 dB OISR. This is an interesting phenomenon and important for optical communication as this clearly shows that the geometric loss is no longer important for the design of receiver aperture and optimal spacing of the diversity scheme for the underwater laser communication system in the highly scattering channel. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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29 pages, 7728 KiB

Open AccessArticle

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

by Pablo Palacios Játiva, Milton Román Cañizares, Cesar A. Azurdia-Meza, David Zabala-Blanco, Ali Dehghan Firoozabadi, Fabian Seguel, Samuel Montejo-Sánchez and Ismael Soto

Sensors 2020, 20(2), 367; https://doi.org/10.3390/s20020367 - 09 Jan 2020

Cited by 45 | Viewed by 4392

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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15 pages, 7411 KiB

Open AccessArticle

Delta-Sigma Modulated Visible Light Communication Illumination System Using a Projector with the Digital Micro-Mirror Device

by Motoi Kodama and Shinichiro Haruyama

Sensors 2019, 19(24), 5512; https://doi.org/10.3390/s19245512 - 13 Dec 2019

Cited by 1 | Viewed by 3358

Abstract

There is a unique transmission method of visible light communication (VLC) that can transmit multiple data in multiple directions simultaneously by using a projector with the digital micro-mirror device (DMD). Previously, we proposed a method of transmitting data from the projector that transmits [...] Read more.

There is a unique transmission method of visible light communication (VLC) that can transmit multiple data in multiple directions simultaneously by using a projector with the digital micro-mirror device (DMD). Previously, we proposed a method of transmitting data from the projector that transmits digitally modulated VLC signal from each pixel, and in this paper, we propose an extension of the method to transmit audio signal by using a special type of modulation called delta-sigma-modulation (DSM). The DSM-VLC system employs a simple receiver that comprises simple analog electric circuits, which contribute to low power consumption. We made a DSM-VLC prototype and verified that the prototype was able to send four different waves to different directions. Additionally, the experiments’ results agree very well with the simulation results. Furthermore, we designed two types of DSM: pulse width modulation (PWM) and pulse density modulation (PDM), and we verified that the PDM-VLC is better than the PWM-VLC regarding the DMD switching frequency’s efficiency. Our proposed DSM-VLC can be used for such applications as voice information guidance systems with direction-selective messages. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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14 pages, 2151 KiB

Open AccessArticle

Indoor Intruder Tracking Using Visible Light Communications

by Farah M. Alsalami, Zahir Ahmad, Stanislav Zvanovec, Paul Anthony Haigh, Olivier C. L. Haas and Sujan Rajbhandari

Sensors 2019, 19(20), 4578; https://doi.org/10.3390/s19204578 - 21 Oct 2019

Cited by 10 | Viewed by 3305

Abstract

This paper proposes a comprehensive study of indoor intruder tracking using visible light communication (VLC). A realistic indoor VLC channel was developed, taking into consideration reflections, shadowing, and ambient noise. The intruder was considered smart and aiming to escape tracking. This was modelled [...] Read more.

This paper proposes a comprehensive study of indoor intruder tracking using visible light communication (VLC). A realistic indoor VLC channel was developed, taking into consideration reflections, shadowing, and ambient noise. The intruder was considered smart and aiming to escape tracking. This was modelled by adding noise and disturbance to the intruder’s trajectory. We propose to extend the application of minimax filtering from state estimation in the radio frequency (RF) domain to intruder tracking using VLC. The performance of the proposed method was examined and compared with Kalman filter for both VLC and RF. The simulation results showed that the minimax filter provided marginally better tracking and was more robust to the adversary behavior of the intruder than Kalman filter, with less than 0.5 cm estimation error. In addition, minimax was significantly better than Kalman filter for RF tracking applications. Full article

(This article belongs to the Special Issue Free-Space Optical and Visible Light Communications)

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