GaN-Based Micro-LED Visible Light Communication: Line-of-Sight VLC with Active Tracking and None-Line-of-Sight VLC Demonstration

abstract: Visible light communication (VLC) is the promise of a high data rate wireless network for both indoor and outdoor uses. It competes with 5G radio frequency (RF) system as well. Even though the breakthrough of Gallium Nitride (GaN) based micro-light-emitting-diodes (micro-LEDs) enhances the -3dB modulation bandwidth dramatically from tens of MHz to hundreds of MHz, the optical power onto a fast photo receiver drops exponentially. It determines the signal to noise ratio (SNR) of VLC. For full implementation of the useful high data-rate VLC link enabled by a GaN-based micro-LED, it needs focusing optics and a tracking system. In this dissertation, we demonstrate a novel active on-chip monitoring system for VLC using a GaN-based micro-LED and none-return-to-zero on-off keying (NRZ-OOK) modulation scheme. By this innovative technique without manual focusing, the field of view (FOV) was enlarged to 120° and data rates up to 600 Mbps at a bit error rate (BER) of 2.1×10⁻⁴ were achieved. This work demonstrates the establishment of a VLC physical link. It shows improved communication quality by orders, making it optimized for real communications. This dissertation also gives an experimental demonstration of non-line-of-sight (NLOS) visible light communication (VLC) using a single 80 μm gallium nitride (GaN) based micro-light-emitting diode (micro-LED). IEEE 802.11ac modulation scheme with 80 MHz bandwidth, as an entry level of the fifth generation of Wi-Fi, was employed to use the micro-LED bandwidth efficiently. These practical techniques were successfully utilized to achieve a demonstration of line-of-sight (LOS) VLC at a speed of 433 Mbps, and a bit error rate (BER) of 10⁻⁵ with a free space transmit distance 3.6 m. Besides this, we demonstrated directed NLOS VLC links based on mirror reflections with a data rate of 433 Mbps and a BER of 10⁻⁴. For non-directed NLOS VLC using a print paper as the reflective material, 195 Mbps data rate and a BER of 10⁻⁵ was achieved.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Connected cars: communication between vehicles and infrastructure through visible light

Dissertação para obtenção do Grau de Mestre em Engenharia de Electrónica e TelecomunicaçõesDevido ao aumento da procura de tráfego, a banda de radiofrequência (RF) esta actualmente em baixa oferta. Uma vez que a Visible Light Communication (VLC) emprega o espectro de luz visível para transmitir e codificar dados, e uma potencial tecnologia sem fios alternativa a considerar. Nos últimos anos, este tipo de tecnologia tem mudado e avançado. Esta tese visa caracterizar e testar ligações de comunicação baseadas em VLC para utilização em sistemas de gestão de tráfego. A infraestrutura primaria para regular o acesso as estradas, semáforos, será em breve substituída por outras mais eficazes para melhorar a gestão do tráfego. Os LEDs brancos Tetrachromatic servem como transmissores da ligação VLC e são utilizados tanto para a transmissão de dados como para a iluminação. O recetor e construído em fotodiodos SiC:H/a-Si:H, que tem sensibilidade de espectro seletivo. A modulação On-Off Keying (OOK) e utilizada para transmitir a mensagem num cenário de intersecção de sete células com uma estrutura de 64 bits e LEDs em cada canto criando uma célula de nove pés de impressão. Utilizando uma ferramenta de simulação, foram obtidas as pegadas de cada célula e o mapa de cobertura. Para demonstrar como a estrutura da moldura e construída e enviada, foi testada uma trajetória com o veículo a viajar de Este para Sul.Due to increased traffic demand, Radio Frequency (RF) band is currently in low supply. Since Visible Light Communication (VLC) employs the visible light spectrum to transmit and encode data, it is a potential alternative wireless technology to consider. In recent years, this kind of technology has changed and advanced. This thesis aims to characterize and test VLC-based communication links for use in traffic management systems. The primary infrastructure for regulating access to roads, traffic lights, will shortly be replaced by more effective ones to enhance traffic management. Tetrachromatic white LEDs serve as the VLC link’s transmitters and are used for both data transmission and lighting. The receiver is built on SiC:H/a-Si:H photodiodes, which have selective spectrum sensitivity. Modulation On-Off Keying (OOK) is used to transmit the message in a sevencell intersection scenario with a 64-bit frame structure and LEDs at each corner creating a nine-footprint cell. Using a simulation tool, the footprints of each cell and the coverage map were obtained. To demonstrate how the frame structure is constructed and sent, a trajectory was tested with the vehicle travelling from East to South.N/

Využití softwarově definovaného rádia v oblasti SMART technologii

Modern telecommunication systems are rapidly evolving. This rapid development requires constant research and fast prototyping. This dissertation thesis focusses on deployment of software defined radio (SDR) in multiple application areas, including SMART technologies. SDR itself is a tool behind many breakthroughs in modern telecommunications, due to its major adaptability. It offers a comprehensive way of fast prototyping, which rely on suitable software platform. The field of telecommunications is ever-changing, due to the constant pressure on innovation. For this reason, it is desirable to test some of the alternative communication technologies. Visible light communication (VLC) system based on combination of virtual instrumentation and software defined radios was chosen for experimentation. This dissertation focusses on multiple versions of VLC system that were developed over the years. Each version is further discussed, and their advantages and disadvantages are presented. A draft of fourth and newest version is mentioned along with possible directions of the research. Results from multiple application areas are presented, which show the adaptability of the whole platform to different use cases including but not limited to: SMART technologies, automotive, nuclear waste disposal sites, or industry. It is demonstrated that the newest version of the system, which is based on OFDM modulation, can communicate up to 50 meters in closed environments and up to 35 meters in outdoor scenarios. This opens further research directions such as truck platooning or underwater communications.Moderní komunikační systémy jsou jednou z nejrychleji se rozvíjejících oblastí. Takového markantního posunu lze dosáhnout pouze skrze nový vývoj a aplikaci metodiky fast prototypingu. Tato disertace se zaměřuje na nasazení technologie softwarově definovaného rádia (SDR) v různých aplikačních oblastech. Samotné SDR je díky své adaptabilitě nástrojem, který stál na pozadí rozvoje mnoha moderních telekomunikačních systémů. Jedná se o ucelenou platformu pro fast prototyping, která se opírá o robustní softwarovou základnu. Právě telekomunikace jsou oblastí, kde je takové zařízení nedocenitelné, právě kvůli neustálému tlaku na inovace. Právě to je důvodem, proč je vhodné také testovat různé alternativní technologie pro přenos dat. Jednou z takových je komunikace viditelným spektrem světla (VLC), která je náplní této práce. Součástí praktické části je vývoj a popis několika verzí VLC systému založených na virtuální instrumentaci a SDR, které vznikly během autorova studia. Každá verze je samostatně popsána včetně výhod a nevýhod, které poskytují. Součástí je též první náčrt čtvrté verze, která bude součástí budoucího výzkumu. Prezentované výsledky z různých aplikačních oblastí jasně ukazují, že je celou platformu možné použít v různých aplikačních oblastech, včetně SMART technologií, automotive, úložišti jaderného odpadu anebo Průmyslu 4.0. Součástí jsou též výsledky z poslední verze, které dokazují, že je systém ve vnitřních prostorech komunikovat až na vzdálenost 50 metrů, zatímco ve venkovních podmínkách je to 35 metrů. Díky tomu je možné vytyčit nové oblasti výzkumu jako je například platooning (tandemová jízda) anebo podvodní komunikace.450 - Katedra kybernetiky a biomedicínského inženýrstvívyhově

Komunikace viditelným světlem (VLC) pro LED veřejné osvětlení a další venkovní aplikace

This diploma thesis focuses on visible light communications, mainly in outdoor appliances. Whole text is divided into two blocks. First segment serves as a research, focusing on experiments carried by different university teams all over the world, which are published as IEEE conference papers. Another half discuss our own VLC prototyping, its limitations and possible upgrade paths.Tato práce se zabývá problematikou komunikace viditelným spektrem světla. Celý text je rozvržen do dvou velkých bloků, přičemž první slouží jako rešerše prací jiných týmů ze všech koutů světa, publikovaných na IEEE konferencích. Druhá část pojednává o samotném měření a prototypu komunikačního řetězce. Zmíněna je konstrukce, limitace i možnosti budoucích vylepšení.440 - Katedra telekomunikační technikyvýborn

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.Scopu

Sistemas de comunicação por luz visível aplicados para assistência ao tráfego automóvel

Motivated by the topic of promoting traffic safety applications and information systems, this work aims to bring a study on VLC outdoor application scenarios. The developed topic is part of intelligent transportation systems (ITS) that aim at the delivery of traffic safety and information amongst other safety functions. VLC technology in traffic communication applications gains interest due to some advantages it presents. The use of LEDs in traffic signaling infrastructures and vehicle headlights started to be a growing standard. With the combination of illuminating proprieties and communication in the same device, VLC becomes a very attractive technology for the implementation of outdoor communication systems for traffic information and control. Outdoor VLC channels present variable ambient conditions, with the presence of different optical sources. One major problem in this communication channel is the presence of shot-noise, generated by optical background radiance from different light sources. This dissertation presents two different communication scenarios for traffic information systems, the first being directed at the infrastructure to car (I2C) link and the second one for car to car (C2C) communication. In order to simulate the communication link performance with variable ambient channel conditions, several models for optical propagation, emitter, receiver and noise sources were implemented in MATLAB. Models for different optical sources were also implemented, with field measurements on the illuminance incident on a photo detector and their impact on the noise generated. In the simulation’s performance of the VLC link, several baseband modulation schemes were considered, aiming at the assessment of link performance, based on the traditional digital modulation performance metrics.Motivado em promover o tópico de segurança rodoviária e sistemas de informação, este trabalho providência um estudo dedicado a sistemas de comunicação por luz visível (VLC) para aplicação em cenários de exterior. O tópico desenvolvido faz parte de sistemas de transporte inteligentes (ITS) cujo propósito é a disseminação de sistemas de segurança no tráfego e transferência de informação, para aplicações de segurança. A tecnologia VLC aplicada a sistemas de comunicação de tráfego rodoviário suscita elevado interesse devido a vantagens que esta apresenta. O uso de LED’s em semáforos e faróis de carros começa a ser bastante comum. Com a combinação de diferentes valências, como iluminação e transferência de dados no mesmo dispositivo, a tecnologia VLC torna-se muito atrativa para a implementação em sistema de comunicação exterior dedicados a sistemas de informação e controlo de tráfego. O canal de comunicação VLC exterior apresenta condições variáveis, devido ao fato de existirem condições ambientais diferentes. Um grave problema neste tipo de canal de comunicação é a presença de ruido Shot, que é normalmente gerado devido á radiância causada por diferentes fontes de luz de fundo. Nesta dissertação estão presentes dois tipos de cenários para sistemas de informação de tráfego, em que o primeiro dedica-se á comunicação semáforo-carro (I2C) e o segundo cenário para a comunicação entre carros (C2C). Para simular o desempenho do canal de comunicação com diferentes condições ambientais, foram implementados em MATLAB modelos para a propagação ótica, descrição do emissor, recetor e fontes de ruido. Também foram incluídos modelos para diferentes fontes óticas de radiação, com medições de campo da iluminância incidente num foto recetor e modulado o impacto na geração de ruido. Nas simulações de desempenho da comunicação por luz visível, foram considerados diferentes esquemas de modulação da informação com o intuito de avaliar o desempenho da ligação, a qual foi feita recorrendo a métricas clássicas de desempenho de modulações digitais.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined

Testing V2X Visible Light Communications in Real Driving Scenarios

Tato diplomová práce se zabývá komunikací viditelným světlem v automobilové dopravě. Teoretická část popisuje problematiku zmiňované technologie v běžném provozu. Následně zkoumá výsledky experimentů, které již byly v minulosti provedeny. V rámci praktické části byl do vozidel implementován prototyp technologie V2X-VLC-SDR a provedeny experimenty v statických i dynamických scénářích. Byly zkoumány propustnosti systému a limitní komunikační vzdálenosti pro jednotlivé nastavené parametry.This thesis is concerned with the communication of the visible light within the automobile transportation. The theoretical part describes previously mentioned technologies in the regular traffic. Then it examines the results of experiments that were concluded in the past. In the practical part of the thesis, a prototype of the V2X-VLC-SDR technology was implemented into the vehicles and experiments were carried out within dynamic and static scenarios. Permeability of the system and limiting communication distance were examined, for individual set parameters.440 - Katedra telekomunikační technikyvýborn

Visible light communication system based on software defined radio: Performance study of intelligent transportation and indoor applications

In this paper, our first attempt at visible light communication system, based on software defined radio (SDR) and implemented in LabVIEW is introduced. This paper mainly focuses on two most commonly used types of LED lights, ceiling lights and LED car lamps/tail-lights. The primary focus of this study is to determine the basic parameters of real implementation of visible light communication (VLC) system, such as transmit speed, communication errors (bit-error ratio, error vector magnitude, energy per bit to noise power spectral density ratio) and highest reachable distance. This work focuses on testing various multistate quadrature amplitude modulation (M-QAM). We have used Skoda Octavia III tail-light and Phillips indoor ceiling light as transmitters and SI PIN Thorlabs photodetector as receiver. Testing method for each light was different. When testing ceiling light, we have focused on reachable distance for each M-QAM variant. On the other side, Octavia tail-light was tested in variable nature conditions (such as thermal turbulence, rain, fog) simulated in special testing box. This work will present our solution, measured parameters and possible weak spots, which will be adjusted in the future.Web of Science84art. no. 43