Research

28 pages, 3071 KiB

Open AccessArticle

Two-Phase Framework for Indoor Positioning Systems Using Visible Light ^†

by Gregary B. Prince and Thomas D. C. Little

Sensors 2018, 18(6), 1917; https://0-doi-org.brum.beds.ac.uk/10.3390/s18061917 - 12 Jun 2018

Cited by 11 | Viewed by 3846

Recently with the advancement of solid state lighting and the application thereof to Visible Light Communications (VLC), the concept of Visible Light Positioning (VLP) has been targeted as a very attractive indoor positioning system (IPS) due to its ubiquity, directionality, spatial reuse, and [...] Read more.

Recently with the advancement of solid state lighting and the application thereof to Visible Light Communications (VLC), the concept of Visible Light Positioning (VLP) has been targeted as a very attractive indoor positioning system (IPS) due to its ubiquity, directionality, spatial reuse, and relatively high modulation bandwidth. IPSs, in general, have four major components: (1) a modulation, (2) a multiple access scheme, (3) a channel measurement, and (4) a positioning algorithm. A number of VLP approaches have been proposed in the literature and primarily focus on a fixed combination of these elements and moreover evaluate the quality of the contribution often by accuracy or precision alone. In this article, we provide a novel two-phase indoor positioning algorithmic framework that is able to increase robustness when subject to insufficient anchor luminaries and also incorporate any combination of the four major IPS components. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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13 pages, 3837 KiB

Open AccessArticle

Time-Sharing-Based Synchronization and Performance Evaluation of Color-Independent Visual-MIMO Communication

by Tae-Ho Kwon, Jai-Eun Kim and Ki-Doo Kim

Sensors 2018, 18(5), 1553; https://0-doi-org.brum.beds.ac.uk/10.3390/s18051553 - 14 May 2018

Cited by 11 | Viewed by 3247

Abstract

In the field of communication, synchronization is always an important issue. The communication between a light-emitting diode (LED) array (LEA) and a camera is known as visual multiple-input multiple-output (MIMO), for which the data transmitter and receiver must be synchronized for seamless communication. [...] Read more.

In the field of communication, synchronization is always an important issue. The communication between a light-emitting diode (LED) array (LEA) and a camera is known as visual multiple-input multiple-output (MIMO), for which the data transmitter and receiver must be synchronized for seamless communication. In visual-MIMO, LEDs generally have a faster data rate than the camera. Hence, we propose an effective time-sharing-based synchronization technique with its color-independent characteristics providing the key to overcome this synchronization problem in visual-MIMO communication. We also evaluated the performance of our synchronization technique by varying the distance between the LEA and camera. A graphical analysis is also presented to compare the symbol error rate (SER) at different distances. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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18 pages, 75395 KiB

Open AccessArticle

Efficient Visible Light Communication Transmitters Based on Switching-Mode dc-dc Converters

by Juan Rodríguez, Diego G. Lamar, Daniel G. Aller, Pablo F. Miaja and Javier Sebastián

Sensors 2018, 18(4), 1127; https://0-doi-org.brum.beds.ac.uk/10.3390/s18041127 - 07 Apr 2018

Cited by 22 | Viewed by 6048

Abstract

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting [...] Read more.

Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMC_dc-dc) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency. However, the new requirements related to the communication, especially the high bandwidth that the LED driver must achieve, converts the design of the SMC_dc-dc into a very challenging task. In this work, three different methods for achieving such a high bandwidth with an SMC_dc-dc are presented: increasing the order of the SMC_dc-dc output filter, increasing the number of voltage inputs, and increasing the number of phases. These three strategies are combinable and the optimum design depends on the particular VLC application, which determines the requirements of the VLC transmitter. As an example, an experimental VLC transmitter based on a two-phase buck converter with a fourth-order output filter will demonstrate that a bandwidth of several hundred kilohertz (kHz) can be achieved with output power levels close to 10 W and power efficiencies between 85% and 90%. In conclusion, the design strategy presented allows us to incorporate VLC into SSL, achieving high bit rates without damaging the power efficiency of LED lighting. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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16 pages, 2122 KiB

Open AccessArticle

Mobile User Connectivity in Relay-Assisted Visible Light Communications

by Petr Pešek, Stanislav Zvanovec, Petr Chvojka, Manav R. Bhatnagar, Zabih Ghassemlooy and Prakriti Saxena

Sensors 2018, 18(4), 1125; https://0-doi-org.brum.beds.ac.uk/10.3390/s18041125 - 07 Apr 2018

Cited by 23 | Viewed by 5018

Abstract

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The [...] Read more.

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The focus of the paper is on analysis of the behavior of the mobile user acting as a relay while considering a realistic locations of the receivers and transmitters on a standard mobile phone, more specifically with two photodetectors on both sides of a mobile phone and a transmitting LED array located upright. We also investigate dependency of the bit error rate (BER) performance on the azimuth and elevation angles of the mobile relay device within a typical office environment. We provide a new analytical description of BER for AF and DF-based relays in VLC. In addition we compare AF and DF-based systems and show that DF offers a marginal improvement in the coverage area with a BER < 10^–3 and a data rate of 100 Mb/s. Numerical results also illustrate that relay-based systems offer a significant improvement in terms of the coverage compared to direct non-line of sight VLC links. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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17 pages, 13649 KiB

Open AccessArticle

Discrete Indoor Three-Dimensional Localization System Based on Neural Networks Using Visible Light Communication

by Itziar Alonso-González, David Sánchez-Rodríguez, Carlos Ley-Bosch and Miguel A. Quintana-Suárez

Sensors 2018, 18(4), 1040; https://0-doi-org.brum.beds.ac.uk/10.3390/s18041040 - 30 Mar 2018

Cited by 42 | Viewed by 4681

Abstract

Indoor localization estimation has become an attractive research topic due to growing interest in location-aware services. Many research works have proposed solving this problem by using wireless communication systems based on radiofrequency. Nevertheless, those approaches usually deliver an accuracy of up to two [...] Read more.

Indoor localization estimation has become an attractive research topic due to growing interest in location-aware services. Many research works have proposed solving this problem by using wireless communication systems based on radiofrequency. Nevertheless, those approaches usually deliver an accuracy of up to two metres, since they are hindered by multipath propagation. On the other hand, in the last few years, the increasing use of light-emitting diodes in illumination systems has provided the emergence of Visible Light Communication technologies, in which data communication is performed by transmitting through the visible band of the electromagnetic spectrum. This brings a brand new approach to high accuracy indoor positioning because this kind of network is not affected by electromagnetic interferences and the received optical power is more stable than radio signals. Our research focus on to propose a fingerprinting indoor positioning estimation system based on neural networks to predict the device position in a 3D environment. Neural networks are an effective classification and predictive method. The localization system is built using a dataset of received signal strength coming from a grid of different points. From the these values, the position in Cartesian coordinates

(x, y, z)

is estimated. The use of three neural networks is proposed in this work, where each network is responsible for estimating the position by each axis. Experimental results indicate that the proposed system leads to substantial improvements to accuracy over the widely-used traditional fingerprinting methods, yielding an accuracy above 99% and an average error distance of 0.4 mm. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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10 pages, 8040 KiB

Open AccessArticle

Volterra Kernel Estimation of White Light LEDs in the Time Domain

by Grzegorz Stepniak, Marcin Kowalczyk and Jerzy Siuzdak

Sensors 2018, 18(4), 1024; https://0-doi-org.brum.beds.ac.uk/10.3390/s18041024 - 29 Mar 2018

Cited by 7 | Viewed by 3801

Abstract

In this paper, we present a time domain method for extracting coefficients of nonlinear Volterra-series kernels for white light-emitting diodes (LED) used both for illumination and visible light communications. We show that this method may have several advantages over the thus far more [...] Read more.

In this paper, we present a time domain method for extracting coefficients of nonlinear Volterra-series kernels for white light-emitting diodes (LED) used both for illumination and visible light communications. We show that this method may have several advantages over the thus far more popular frequency domain method. We successfully apply the measured kernel coefficients up to the 3rd order for the modeling of nonlinear distortion impact on advanced modulation formats: pulse amplitude modulation, carrierless amplitude phase and orthogonal frequency division multiplexing. The impact of blue filtering on dynamic nonlinearity is also presented. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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9 pages, 43941 KiB

Open AccessArticle

An Experimental Study of a Micro-Projection Enabled Optical Terminal for Short-Range Bidirectional Multi-Wavelength Visible Light Communications

by Hsi-Hsir Chou, Cheng-Yu Tsai and Jhih-Shan Jiang

Sensors 2018, 18(4), 983; https://0-doi-org.brum.beds.ac.uk/10.3390/s18040983 - 26 Mar 2018

Cited by 1 | Viewed by 3682

Abstract

A micro-projection enabled short-range communication (SRC) approach using red-, green- and blue-based light-emitting diodes (RGB-LEDs) has experimentally demonstrated recently that micro-projection and high-speed data transmission can be performed simultaneously. In this research, a reconfigurable design of a polarization modulated image system based on [...] Read more.

A micro-projection enabled short-range communication (SRC) approach using red-, green- and blue-based light-emitting diodes (RGB-LEDs) has experimentally demonstrated recently that micro-projection and high-speed data transmission can be performed simultaneously. In this research, a reconfigurable design of a polarization modulated image system based on the use of a Liquid Crystal on Silicon based Spatial Light Modulator (LCoS-based SLM) serving as a portable optical terminal capable of micro-projection and bidirectional multi-wavelength communications is proposed and experimentally demonstrated. For the proof of concept, the system performance was evaluated through a bidirectional communication link at a transmission distance over 0.65 m. In order to make the proposed communication system architecture compatible with the data modulation format of future possible wireless communication system, baseband modulation scheme, i.e., Non-Return-to-Zero On-Off-Keying (NRZ_OOK), M-ary Phase Shift Keying (M-PSK) and M-ary Quadrature Amplitude Modulation (M-QAM) were used to investigate the system transmission performance. The experimental results shown that an acceptable BER (satisfying the limitation of Forward Error Correction, FEC standard) and crosstalk can all be achieved in the bidirectional multi-wavelength communication scenario. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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4084 KiB

Open AccessArticle

Study and Validation of Eavesdropping Scenarios over a Visible Light Communication Channel

by Ignacio Marin-Garcia, Victor Guerra and Rafael Perez-Jimenez

Sensors 2017, 17(11), 2687; https://0-doi-org.brum.beds.ac.uk/10.3390/s17112687 - 21 Nov 2017

Cited by 17 | Viewed by 5546

Abstract

The security and privacy provided by Visible Light Communication (VLC) technologies is an area that has been slightly addressed due to the misconception that, since light does not go through solid objects like walls, VLC-based communications cannot be eavesdropped on by outside observers. [...] Read more.

The security and privacy provided by Visible Light Communication (VLC) technologies is an area that has been slightly addressed due to the misconception that, since light does not go through solid objects like walls, VLC-based communications cannot be eavesdropped on by outside observers. As an upcoming technology, VLC is expected to be used in multiple environments were, due to radio frequency RF overuse or limitations, RF solutions cannot or should not be employed. In this work, we study the eavesdropping characteristics of a VLC-based communication. To evaluate these concerns, a two-step process was followed. First, several simulations of a standardly used scenario were run. Later on, experimental tests were performed. Following those tests, the results of the simulations and the experimental tests were analyzed. The results of these simulations and tests seemed to indicate that VLC channels can be eavesdropped on without considerable difficulties. Furthermore, the results showed that sniffing attacks could be performed from areas outside the expected coverage of the VLC infrastructure. Finally, the use of the simulation such as the one implemented in this work to recognize places from which sniffing is possible helps determine the risk for eavesdropping that our VLC-based network has. Full article

(This article belongs to the Special Issue Visible Light Communication Networks)

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