Indoor Visible Light Communication Link Research Articles

Visible light communication for intelligent transportation systems: A review of the latest technologies

In seeking to improve traffic congestion and safety on roads and highways, there has been an increased interest in intelligent transportation systems (ITS). The emerging visible light communication (VLC) technology is a new candidate to enable wireless access in ITS. The purpose of this study is to present a comprehensive review of the current studies related to VLC. Since VLC facilitates illumination and data communication simultaneously, it reduces energy consumption significantly. Additionally, VLC is immune to electromagnetic interference, provides high data security, and utilizes unregulated visible light spectrum, showing promise as a potentially cheaper alternative to existing radio frequency (RF) based technology. Moreover, recent advances in semiconductor materials and solid-state technologies have enabled the development of efficient light-emitting diodes (LEDs) and laser diodes (LDs) which are used as transmitters in a VLC system. Although 10 s of Gbits/s data rate has been demonstrated in indoor VLC links, successful implementation of it in outdoor environments requires further research to overcome the challenges presented by environmental factors, unwanted lights, non-line of sight communication, directional radiation pattern, frequent fragmentation, and so on. Besides, in recent years, semiconductor LDs have been garnering more attention since they can transmit more data over longer distances due to their high quantum efficiency and modulation bandwidth compared to LEDs. As a result, urban planners, policy-makers, transportation engineers, and vehicle manufacturers are considering LD-based VLC to facilitate vehicle-to-vehicle and vehicle-to-infrastructure communication. Thus, this paper reviews and compares the most recent developments in VLC technologies, identifies their benefits and potential use in ITS applications, discusses the probable barriers for their implementation in our existing transportation infrastructure, and suggests future research directions and recommendations to overcome these challenges. • Recent developments in visible light communication (VLC) technology and its potential use in ITS applications are reviewed. • Light-emitting diodes (LEDs) and laser diodes (LDs) can be used as transmitters in VLC systems. • The overall performance of LDs is superior to that of the LEDs. • LDs can transmit more data over longer distances due to their high quantum efficiency and modulation bandwidth. • It is recommended to focus more on LD-based illumination in V2V and V2I communications.

On the Effect of Multipath Reflections in Indoor Visible Light Communication Links: Channel Characterization and BER Analysis

Owing to its several advantages over other wireless schemes, visible light communication (VLC) shall be at the forefront of optical wireless communication technology. However, due to multipath reflections and spatial distribution of light-emitting diode (LED) transmitters, there is an inherent delay spread in the VLC channels. We perform a comprehensive quantitative study on the effect of several practical factors like LED semi-angle, wall reflectivity, number of reflections, number of LED panels, room size, and user locations on the channel delay parameters, namely RMS delay spread and coherence bandwidth of the channel. We present the detailed derivation of the multipath VLC channel model and incorporate the effect of inter-symbol interference in bit error rate (BER) performance of the multipath VLC system. We analyze the average BER of the system under different practical scenarios and determine the penalty in signal to noise ratio entailed by a change in the system parameters mentioned above. We conclude that it is sufficient to model up to three reflections in the VLC channel to emulate the effect of multipath propagation on the channel characterization and BER analysis of the system. The results and analyses presented herein provide critical insights into the effect of multipath reflections in indoor VLC links, particularly the BER performance and channel delay characteristics. We also provide some key recommendations for the design of practical VLC systems by outlining the data rates that can be served under different system configurations.

Modeling and analysis of multi-channel gigabit class CWDM-VLC system

Wavelength Division Multiplexing (WDM) is one possible solution to increase the data rate for Visible Light Communication (VLC). Coarse WDM (CWDM) was used to increase data rate in traditional optical fiber systems. In this work, we propose CWDM for a VLC system using multiple LEDs with different monochromatic colors in the full visible spectrum. Besides, optical filters are used to separate different wavelengths from received signals and to maximize their performance, while minimizing crosstalk. Spacing between the channels is 20 nm, and the combination of channels produce white light for indoor illumination. The simulation results show very good performance in terms of bit error rate (BER) and improve data rate for an indoor VLC link. This VLC-CWDM system can achieve a data rate of 3.2 Gb/s and 7.2 Gb/s for 10 and 20 channels, respectively. Comparatively, the current WDM-VLC system can achieve 1.97 Gb/s data rate with the same simulation parameters.

Development of an Audio Transmission System Through an Indoor Visible Light Communication Link

Development of an Audio Transmission System Through an Indoor Visible Light Communication Link

室内可见光通信系统的光源布局优化及性能分析

In the indoor visible light communication (VLC) system based on white light-emitting diode (LED), considering the primary reflection of the wall, the layout schemes of different LED topology are studied. By adjusting the topological distribution, the square array combined with the circular ring layout model is proposed to reduce the power consumption of system, and the dynamic range compressions of illuminance and signal-to-noise ratio (SNR) of the receiving plane are realized by power distribution under the indoor lighting requirements. The illuminance distribution, received power distribution, SNR distribution and bit error rate (BER) performance of the square array combined with the circular ring layout model based on power distribution are simulated and analyzed. The simulation results show that the number of light sources used in the square array combined with the ring layout is reduced by 48 compared with the traditional square array layout, but the performance is still improved. At the same time, the relationships between bandwidth, BER, distance and SNR of indoor VLC link system are given, which can provide reference for users to build VLC links. © 2019, Chinese Lasers Press. All right reserved.

Modulation and Demodulation Techniques in Indoor Visible Light Communication System

Visible light communication technology is a emerging wireless and optical communication technology developed after invention and application of white LED.In this paper, we have a research based on indoor visible light communication system of lighting white LED,discuss of the visible light communication channel characteristics,detailedly analysis of the indoor visible light communication link. This paper focuses on the modulation and demodulation method applied to visible light communication. In the past visible light communication is mainly used off keying modulation,however, the data transfer speed is limited due to the influence of ISI .This paper presents a solution based on OFDM modulation and demodulation, to reduce the impact brought from inter-symbol string under high data transfer speed.Based on data analysis and computer simulation,the program presented in this paper can be used as indoor lighting and high-speed data transmission.Finally, give scheme to achieve visible light communication modulation and demodulation,provide a theoretical basis for further experiments.