Dimmable visible light communications based on multilayer ACO-OFDM

This paper proposes a dimmable scheme for a visible light communication (VLC) system based on multilayer asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM), which is able to support a wide dimming range for different illumination requirements. In the proposed scheme, multiple layers of ACO-OFDM occupying different subcarriers are combined so that almost all of the subcarriers can be used for data transmission. The polarities of different layers of ACO-OFDM are varied to obtain flexible time-domain waveform, which can fully exploit the dynamic range of light-emitting diodes (LEDs) and achieve better performance. The scaling factor and modulation order for each layer, as well as the dc bias, are optimized for different dimming requirements to achieve improved spectral efficiency. Simulation results demonstrate that the proposed scheme can support communication over a wide dimming range and achieve higher spectral efficiency, compared with existing methods under different dimming requirements

Dimming control in visible light communication using RPO-OFDM and concatenated RS-CC

Increasing wireless data traffic is creating pressure on the conventional dwindling radio frequency spectrum. A new and reliable communication medium becomes a necessity. Visible Light Communication (VLC), a subset of optical wireless communication uses the visible light spectrum between 400 and 800 THz as a medium for communication. VLC utilizes the illumination of LED to establish a communication medium. The research focused on achieving a successful VLC communication link at low intensities of light without affecting the speed, accuracy and efficiency of VLC. The achievement of the paper was to devise a method to reduce the LED brightness, reducing energy consumption and most importantly maintain a reliable, efficient and successful VLC communication link at low intensities of LED. The research comprises of a Reverse Polarity Optical-Orthogonal Frequency Division Multiplexing (RPO-OFDM) modulator, a Forward Error Correction (FEC) encoder block that uses concatenated Reed Solomon - Convolutional Coding, a digital PWM dimming control circuit, an RPO-OFDM demodulator and a FEC decoder. The decoding is performed using the Berlekamp-Massey algorithm and the Viterbi algorithm. Extensive research on various modulation schemes, coding and error correction techniques along with various driver circuit design for dimming control in VLC were thoroughly investigated to conclude the best reliable solution for dimming control in VLC

Theoretical-practical evaluation of the performance of modulation schemes compatible with VLC technology

Visible Light Communications (VLC) is a technology that has emerged in recent years proposing some improvements over traditional radio communications. The objective of this project is to evaluate the bit error rate of different modulations schemes and the requirements of optical communications are described. It is discussed which of them is better to set VLC transmissions. For this, the work has been divided into three sections. The first section describes the communication systems in visible light, as well as the modulations schemes that could be used, more specifically, those that are based on OFDM. In the second section, the MATLAB simulations performed are detailed, representing the bit error rate graph of each of the modulations, varying an added noise. In the third section, the simulations are moved into a real case. For this, two computers and two USRPs modules are used. One of the PC will act as a transmitter and the other as a receiver. The USRPs work as analog-digital/digital-analog converters and are connected to each other by a cable that introduces attenuation. The objective of this configuration is to estimate the bit error rate, varying the noise. Finally, the system is evaluated by replacing the cable that used to connect both USRPs with a LED and a photodetector. In this way, a real practical case of a system based on visible light communications is shown, its performance is studied, and the conclusions are presented

On the Performance of Single- and Multi-carrier Modulation Schemes for Indoor Visible Light Communication Systems

In this paper, we investigate and compare the performance of single- and multi-carrier modulation schemes for indoor visible light communication (VLC). Particularly, the performances of single carrier frequency domain equalization (SCFDE), orthogonal frequency division multiplexing (OFDM) and on-off keying (OOK) with minimum mean square error equalization (MMSE) are analyzed in order to mitigate the effect of multipath distortion of the indoor optical channel where nonlinearity distortion of light emitting diode (LED) transfer function is taken into account. Our results indicate that SCFDE system, in contrast to OFDM system, does not suffer from high peak to average power ratio (PAPR) and can outperform OFDM and OOK systems. We further investigate the impact of LED bias point on the performance of OFDM systems and show that biasing LED with the optimum value can significantly enhance the performance of the system. Bit-interleaved coded modulation (BICM) is also considered for OFDM and SCFDE systems to further compensate signal degradation due to inter-symbol interference (ISI) and LED nonlinearity.Comment: 6 Pages, IEEE Globecom conference 201

Indoor Visible Light Communication:A Tutorial and Survey

Abstract With the advancement of solid-state devices for lighting, illumination is on the verge of being completely restructured. This revolution comes with numerous advantages and viable opportunities that can transform the world of wireless communications for the better. Solid-state LEDs are rapidly replacing the contemporary incandescent and fluorescent lamps. In addition to their high energy efficiency, LEDs are desirable for their low heat generation, long lifespan, and their capability to switch on and off at an extremely high rate. The ability of switching between different levels of luminous intensity at such a rate has enabled the inception of a new communication technology referred to as visible light communication (VLC). With this technology, the LED lamps are additionally being used for data transmission. This paper provides a tutorial and a survey of VLC in terms of the design, development, and evaluation techniques as well as current challenges and their envisioned solutions. The focus of this paper is mainly directed towards an indoor setup. An overview of VLC, theory of illumination, system receivers, system architecture, and ongoing developments are provided. We further provide some baseline simulation results to give a technical background on the performance of VLC systems. Moreover, we provide the potential of incorporating VLC techniques in the current and upcoming technologies such as fifth-generation (5G), beyond fifth-generation (B5G) wireless communication trends including sixth-generation (6G), and intelligent reflective surfaces (IRSs) among others

Visible Light Communication (VLC)

Visible light communication (VLC) using light-emitting diodes (LEDs) or laser diodes (LDs) has been envisioned as one of the key enabling technologies for 6G and Internet of Things (IoT) systems, owing to its appealing advantages, including abundant and unregulated spectrum resources, no electromagnetic interference (EMI) radiation and high security. However, despite its many advantages, VLC faces several technical challenges, such as the limited bandwidth and severe nonlinearity of opto-electronic devices, link blockage and user mobility. Therefore, significant efforts are needed from the global VLC community to develop VLC technology further. This Special Issue, “Visible Light Communication (VLC)”, provides an opportunity for global researchers to share their new ideas and cutting-edge techniques to address the above-mentioned challenges. The 16 papers published in this Special Issue represent the fascinating progress of VLC in various contexts, including general indoor and underwater scenarios, and the emerging application of machine learning/artificial intelligence (ML/AI) techniques in VLC