Visible Light Communication Technology Research Articles

A Review of Cognitive Hybrid Radio Frequency/Visible Light Communication Systems for Wireless Sensor Networks.

The development and growth of Wireless Sensor Networks (WSNs) is significantly propelled by advances in Radio Frequency (RF) and Visible Light Communication (VLC) technologies. This paper endeavors to present a comprehensive review of the state-of-the-art in cognitive hybrid RF-VLC systems for WSNs, emphasizing the critical task of seamlessly integrating Cognitive Radio Sensor Networks (CRSNs) and VLC technologies. The central challenge addressed is the intricate landscape of this integration, characterized by notable trade-offs between performance and complexity, which escalate with the addition of more devices and increased data rates. This scenario necessitates the development of advanced cognitive radio strategies, potentially facilitated by Machine Learning (ML) and Deep Learning (DL) approaches, albeit introducing new complexities such as the necessity for pre-training with extensive datasets. The review scrutinizes the fundamental aspects of CRSNs and VLC, spotlighting key areas like Energy Efficient Resource Allocation, Industrial Scenarios, and Energy Harvesting, and explores the synergistic amalgamation of these technologies as a promising pathway for enhanced spectrum utilization and network performance. By delving into the integration of cognitive radio technology with visible light, this study furnishes valuable insights into the potential for innovative applications in wireless communication, presenting a balanced overview of the current advancements and prospective avenues in the field of cognitive hybrid RF/VLC systems.

Research on Resource Allocation Strategy of Indoor Visible Light Communication and Radio Frequency Systems Integrating Orthogonal Frequency-Division Multiple Access Technology

Aiming at the problem of resource allocation strategies limiting the system transmission rate in indoor visible light communication and radio frequency (VLC/RF) systems, a new resource allocation method is proposed, and orthogonal frequency-division multiple access (OFDMA) technology is introduced. The capacity of the communication system is effectively increased. In the VLC/RF system model based on OFDMA, the Lyapunov optimization method is used to transform the time averaging problem into a series of single-slot online problems to reduce its computational complexity, the optimization problem is decomposed into three independent subproblems, and the Lagrange relaxation method and convex optimization theory are used to solve the subproblems to maximize the average transmission rate of the system, and the Lyapunov drift is used to ensure the stability of the system. Simulation verifies that the Lyapunov optimization algorithm does not require iteration, which improves the optimization speed to a high extent. The simulation results show that the proposed resource allocation strategy effectively balances the system queue length and transmission rate, improves the average transmission rate of the system to the greatest extent under the premise of ensuring the stability of the system, and compares with other algorithms from the aspects of system stability and transmission rate, which proves the effectiveness of the Lyapunov optimization algorithm.

The Performance Comparison of SC-PPM Receiver Models

Visible light communication (VLC) technology has arisen as promising candidate to solve the critical challenges of wireless communication networks. In particular, the evolving explosion in use of internet services requiring high bandwidth will soon become a great potential problem among the service provider. Meanwhile, this paper describes a physical layer solution to provide data transmission in the VLC networks. In the paper, it is aim to examine the performance comparison of SC-PPM (Subcarrier Pulse Position Modulation) demodulator schemes. It is considered three receiver techniques to assemble the demodulator techniques to SC-PPM receiver system. Firstly, the traditional PPM (T-PPM) demodulator has been applied on the SC-4PPM receiver system to estimate the slot that includes high frequency signal that is referred to as subcarrier signal. To successfully detect the bits by using traditional PPM receiver, it must be known the dimming level of received SC-4PPM signal. This is a serious problem to ensure data transmission in the real-time VLC systems due to challenge of providing the variable dimming level knowledge at the receiver side. In another receiver model that is referred to as PD (Peak Detector), it is aim to detect peak values of slot with high frequency signal. The disadvantage of this system is that BER (Bit Error Rate) performance depends the difference between peak and bottom values of subcarrier filled slot. Hence, second method is improved to achieve the similar BER performance at all dimming levels between 12.5% and 87.5%. This receiver model is called as IPD in the paper. In brief, it is reported for the first time, it has been employed the PD and the IPD algorithms for the SC-PPM receiver schemes. In addition to this, it is given a theoretical framework for both the traditional PPM and the improved receiver schemes in VLC-SC-PPM schemes. Moreover, it has been investigated how the SC-PPM receiver schemes are affected by brightness level.

Fibre optic-VLC versus laser-VLC: a review study

The exponential increase in the demand for a fast and reliable wireless mobile network motivates the need for researchers to engage more actively in visible light communication (VLC) technology. This increase happens in parallel with the augmentation of the population to be accommodated. As a result, the radio frequency spectrum is overcrowded. VLCs, which are part of optical wireless communications, are unregulated ultra-wideband spectrums that offer an alternative to solve RF bandwidth exhaustion. The OWC has demonstrated, among others, a throughput of 100 Gbps and is capable of offloading large data traffic from RF networks. One of the VLC main backdrops is the distance for which light signals can be transmitted, which is generally short in nature. However, this is overcome by its combination with other technologies, such as fibre optics (FO) and laser technologies, to mention only a few, which form a cascaded system with VLC. The data offloaded is fed to the cascaded system of FO-VLC and laser-VLC. In this paper, we provide a comparative review of cascaded FO-VLC and laser-VLC systems. We survey the technology that can provide optimized communication and high bandwidth. The choice of cascaded system to be used or considered is dependent on the area of application. A comparison is conducted from the simulated results of both cascaded systems considering parameters such as the gain and throughput. The FO-VLC cascaded system shows that system gain always decreases as distance increases for a range of reflection coefficient, rho, and slightly decreases with attenuation coefficient, alpha. The gain of the laser-VLC cascaded system decreases with an increase in transmission distance for a given range of floor and ceiling reflection coefficient and decreases slightly with attenuation intensity, gamma. From our investigation, it is clear that FO-VLC and laser-VLC are outstanding optical cascaded systems, which can be exploited in applications with a harsh environment. This research also highlights standardization efforts, advanced modulation schemes and coding techniques so far for VLC, FO and laser system and their promising applications.

High-performance n – Si/p – SeO2 /p – SiO2 heterojunction photodetectors for potential application in visible light communication technology

High-performance n – Si/p – SeO2 /p – SiO2 heterojunction photodetectors for potential application in visible light communication technology

Threefold layered optical wireless network: illumination, communication, and positioning.

Visible light communication (VLC) technology has traditionally emerged as a complementary solution to radio frequency, due to its huge available bandwidth and high data rates. Relying on visible spectrum, VLC allows both illumination and communication, thus representing a green technology with reduced energy impact. However, VLC can also be exploited for localization, and thanks to its huge bandwidth it can reach very high accuracy (i.e., <0.1 m). In this paper, we deal with a VLC network intended as a fully integrated indoor system providing at the same time both illumination, communication, and positioning tasks. Three different optimization problems are presented, aiming to seek for the minimum number of white LEDs that can achieve different constraints of illumination, data rate, and localization accuracy. Different types of LEDs are considered, according to which tasks they are intended to pursue. We consider traditional white LEDs aiming to provide illumination, communication, and positioning; otherwise, we distinguish between devices designed for localization-only and communication-only. Such distinction results in different optimization problems, and related solutions, as confirmed through extensive simulation results.

Addressing Multi-User Interference in Vehicular Visible Light Communications: A Brief Survey and an Evaluation of Optical CDMA MAC Utilization in a Multi-Lane Scenario.

Visible Light Communications (VLC) are developing as an omnipresent solution for inter-vehicle communications. Based on intensive research efforts, the performance of vehicular VLC systems has significantly improved in terms of noise resilience, communication range, and latencies. Nevertheless, in order to be ready for deployment in real applications, solutions for Medium Access Control (MAC) are also required. In this context, this article provides an intensive evaluation of several optical CDMA MAC solutions and of their efficiency in mitigating the effect of Multiple User Interference (MUI). Intensive simulation results showed that an adequately designed MAC layer can significantly reduce the effects of MUI, ensuring an adequate Packet Delivery Ratio (PDR). The simulation results showed that based on the use of optical CDMA codes, the PDR can be improved from values as low as 20% up to values between 93.2% and 100%. Consequently, the results provided in this article show the high potential of optical CDMA MAC solutions in vehicular VLC applications, reconfirm the high potential of the VLC technology in inter-vehicle communications, and emphasize the need to further develop MAC solutions designed for such applications.

Performance Analysis of Unslotted CSMA/CA Based On Channel Dedicated For VLC Networks

Due to the advantages of rich frequency band, security and confidentiality, visible light communication technology is gradually regarded as an effective solution to the exhaustion of radio frequency(RF) spectrum resources. This paper designs a channel dedicated unslotted CSMA/CA algorithm, and analyzes the impact of collision probability, retransmission times, access failure probability, and normalized throughput on the network performance when transmitting non-real-time traffic. The results show that the collision probability is inversely proportional to the terminal payload packet arrival rate λ, as the number of terminals increases, the saturation collision probability of λ =1 is 0.501 and λ =2 is 0.382, The access failure probability increases nonlinearly with the increasing terminals numbers, but when the number of terminals exceeds 5, the access failure probability increases sharply, the normalized throughput decreases continuously and tends to saturate when the total channel traffic reaches the physical limit of bandwidth.

Audio Transmission Using Visible Light Communication Technology with Pre-Equalization Technique

Abstract: The Visible Light Communication (VLC) is the emerging technology that aims to offer high speed internet access in indoor environment. This technology basically uses intensity modulation of current lighting infrastructure, which is provided by Light Emitting Diodes. During the implementation of this technology there may be Inter Symbol Interference (ISI) and power loss in free space channel, in order to overcome this problem and to utilize white light spectrum fully for effective transmission of data several techniques are followed. In this paper, the pre-equalization technique is chosen and implemented for audio transmission. The Pre-equalization of data is performed using MATLAB 2022a Graphical User Interface (GUI) and then feed to designed real-time VLC system. Pre-equalization of audio data improves sound quality and maintained it throughout the transmitting distance which is in Line Of Sight. The optical power distribution of the signal at an indoor environment for chosen white LED for audio transmission is also observed.

A Review of Two Types of New Key Technologies of 6G

The increasing need of future 6G wireless communication of higher transmission rate, larger network capacity, higher energy efficiency has been calling for the development of new key technologies. Among them, the two most popular and promising technologies are new spectrum access technology and efficient wireless transmission technology. New spectrum access technology intends to achieve the utilization of more available spectrum resources with higher frequency and wider bandwidth so that it can highly improve the data transfer rate and expand the network capacity. It includes Terahertz communication technology and visible light communication technology. Efficient Wireless Transmission technology aims to make new breakthroughs in traditional signal transmission mode and achieve larger channel capacity so that network coverage and security can be improved, and signal transmission loss can be decreased. It contains IRS technology and Spatial multiplexing technology. Properties of each technology, such as principles, advantages, application scenarios, are discussed in this paper. In chapter 2, new spectrum access technology is introduced, and efficient wireless transmission technology is introduced in chapter 3.

Recent Advances in Optical Injection Locking for Visible Light Communication Applications

The introduction of visible light communication (VLC) technology could increase the capacity of existing wireless communication systems towards 6G networks. In practice, VLC can make good use of lighting system infrastructures to transmit data using light fidelity (Li-Fi). The use of semiconductor light sources, including light-emitting diodes (LEDs) and laser diodes (LDs) are essential to VLC technology because these devices are energy-efficient and have long lifespans. To achieve high-speed VLC links, various technologies have been utilized, including injection locking. Optical injection locking (OIL) is an optical frequency and phase synchronization technique that has been implemented in semiconductor laser systems for performance enhancement. High-performance optoelectronic devices with narrow linewidth, wide tunable emission, large modulation bandwidth and high data transmission rates are desired for advanced VLC. Thus, the features of OIL could be promising for building high-performance VLC systems. In this paper, we present a comprehensive review of the implementation of the injection-locking technique in optical communication systems. The enhancement of characteristics through OIL is elucidated. The applications of OIL in VLC systems are discussed. The prospects of OIL for future VLC systems are evaluated.

Exploring the Effects of LED-Based Visible Light Communication on Reading and Color Perception in Indoor Environments: An Experimental Study.

Visible light communications (VLC) is a technology that enables the transmission of digital information with a light source. VLC is nowadays seen as a promising technology for indoor applications, helping WiFi to handle the spectrum crunch. Possible indoor applications range from Internet connection at home/office to multimedia content delivery in a museum. Despite the vast interest of researchers in both theoretical analysis and experimentation on VLC technology, no studies have been carried out on the human perceptions of objects illuminated by VLC-based lamps. It is important to define if a VLC lamp decreases the reading capability or modifies the color perception in order to make VLC a technology appropriate for everyday life use. This paper describes the results of psychophysical tests on humans to define if VLC lamps modify the perception of colors or the reading speed. The results of the reading speed test showed a 0.97 correlation coefficient between tests with and without VLC modulated light, leading us to conclude that there is no difference in the reading speed capability with and without VLC-modulated light. The results of the color perception test showed a Fisher exact test p-value of 0.2351, showing that the perception of color is not influenced by the presence of the VLC modulated light.

High Bandwidth Semi-Polar InGaN/GaN Micro-LEDs With Low Current Injection for Visible Light Communication

Micro-light-emitting diodes (micro-LEDs) with high modulation rates and low power consumption could attract growing attention as visible light communication (VLC) technology advances. The designed and fabricated semi-polar micro-LEDs have achieved high bandwidth at low current injection due to the reduced quantum-confined Stark effect (QCSE), which was significantly greater than that of typical c-plane at the same current injection. Semi-polar green micro-LEDs got a −3 dB bandwidth that surpasses 500 MHz and 1 GHz at low current densities of 43.8 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 120.6 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , while blue micro-LEDs exceed 500 MHz at low current densities of 76.6 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , respectively. Additionally, the free space VLC system has shown semi-polar blue and green micro-LED transmission data rates of 3.495 Gbps (433 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and 3.483 Gbps (402 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) respectively. Semi-polar micro-LEDs, which can achieve low power consumption and high bandwidth, are anticipated to play a significant role in the development of energy-efficient VLC in the future.

A Comprehensive Survey on MIMO Visible Light Communication: Current Research, Machine Learning and Future Trends

Visible light communication (VLC) has contributed new unused spectrum in addition to the traditional radio frequency communication and can play a significant role in wireless communication. The adaptation of VLC technology enhances wireless connectivity both in indoor and outdoor environments. Multiple-input multiple-output (MIMO) communication has been an efficient technique for increasing wireless communications system capacity and performance. With the advantages of MIMO techniques, VLC can achieve an additional degree of freedom. In this paper, we systematically perform a survey of the existing work based on MIMO VLC. We categorize the types of different MIMO techniques, and a brief description is given. Different problem-solving approaches are given in the subsequent sections. In addition, machine learning approaches are also discussed in sufficient detail. Finally, we identify the future study direction for MIMO-based communication in VLC.

OCDMA Performance on FSO Turbulent Weather Channel on Li-Fi Systems

&nbsp;Because of advances in Light-Emitting Diodes LEDs and visible-light communication (VLC), future technology is light fidelity. The interference problems with radio frequency (RF) communication was overcome by using visible light communication (VLC) technology, which has higher bandwidth and greater security. On the other hand, the FSO link is affected by complex weather, Where Different atmospheric conditions affect the optical power of the FSO system very significantly, decreasing significantly. The effects of turbulent weather on OCDMA technology are examined in this paper and compared with and without using this technology at different distances in L-Bands in light of the increased number of users. There are various challenges that Li-Fi technology faces in maintaining the system performance with the increase in the number of users. These issues will cause a decrease in the system’s performance parameters, such as BER. Further, the challenges that exist are the total bandwidth usage and the number of users without affecting the system. Finally, security should be maintained at the highest level at the lowest cost. With the best results, the research shows that Optical Code division multiple access OCDMA technologies enhance system performance and stability, especially over long distances. On the contrary, the system will fail to function correctly over the same distance if the technology mentioned above is not utilized. For example, the heavy dust, the system achieved approximately from 1.02 * 10-12 to 9.5 * 10-11 with our proposed technology, whereas it achieved approximately from 2.8 * 10-7 to 4 * 10-4 without the proposed technology at a distance ranging from 60m to 160m.&nbsp; the system was tested during heavy fog weather, considered the most challenging situation, with an n attenuation of 340dB/M. The results revealed that the system achieved roughly 1.11*10-12 to 9.25*10-11, but without OCDMA technology, it achieved between 3.8*10-8 and 1.4*10-4 at 20 m to 120 m. These include heavy dust, fog, and moderate attenuation of 340, 242, and 85 dB/m, which have been used.

Novel AlGaN/GaN HEMT pH Sensor for Real-Time Monitoring Based on Visible Light Communication Technology

This work reports a novel real-time high sensitivity pH monitoring system based on light signal acquisition of visible light communication technology (VLCT). The pH monitoring system is composed of LED as signal transmission and AlGaN/GaN high electron mobility transistor (HEMT) as pH sensor. The luminescence of LED is regulated by HEMT when monitoring pH. The luminescence intensity of the LED varies with the current change of sensor and it will be captured by CCD or optical power meter to realize pH monitoring. The sensor shows excellent sensing characteristics with a maximum sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$285.7 ~\mu \text{A}$ </tex-math></inline-formula> /pH and a resolution of 0.14 pH at the range of pH from 2 to 12.45.

Enhancement of Vehicular Visible Light Communication Using Spherical Detector and Custom Lens Combinations

Vehicular Visible light communication (VLC) technology has recently attracted much interest from researchers and scientists. This technology enables connectivity between vehicles and infrastructures along the road by using vehicles’ headlights and taillights as wireless transmitters. The reliability of vehicle-to-vehicle (V2V) VLC systems is affected by several factors, such as car mobility, optics system design, and visibility conditions, where the first two have the most impact on the VLC system performance. This paper, therefore, focuses on the relative positions of the cars and the design of the optics, especially on the receiving end, which has been proposed with the use of a polar detector instead of the rectangular detectors commonly used in the literature. We investigate the achievable gain compared to the conventional detector for different vehicle locations, utilizing a professional optical system design and ray tracing approach. Then, to improve the performance, we introduce the utilization of an imaging receiver by integrating the polar detector with different optical commercial lens combinations, such as Fresnel and Aspherical lenses. To further improve the V2V system performance, we propose a novel optical lens combination design by integrating double-convex lens with half-Plano-concave lens, which allows the correction of more optical aberrations, such as chromatic and spherical aberration. Utilizing the non-sequential ray tracing tools, we designed these VLC systems and perform a realistic channel modeling study considering the typical 3D CAD models of vehicles and roads as well as the possibility of horizontal and vertical movement between the vehicles. Based on the channel impulse responses (CIRs) obtained from the ray tracing simulations, we analyzed the performance of V2V VLC systems with all lens combinations at different vehicle positions on the road. We further investigated the impact of different system parameters on the overall V2V system performance, such as receiver diameter and bandwidth. The obtained results demonstrated that with a carefully chosen system and lens parameters, the proposed system design of lens combination provides an enhancement of up to 7 dB in total received power compared to the case without a lens. Our results also revealed that the proposed system design outperforms the benchmark ones for all lateral displacements and longitudinal distances.

Characteristic of Line-of-Sight in Infrastructure-to-Vehicle Visible Light Communication Using MIMO Technique

Visible Light Communication (VLC) technology is aggressive research for the next generation of communication. Currently, Radio Frequency (RF) communication has crowed spectrum. An Intelligent Transportation System (ITS) has been improved in the communication network for Vehicle-to-Vehicle (V2 V), Vehicle-to-Infrastructure (V2I), and Infrastructure-to-Vehicle (I2 V) by using the visible light spectrum instead of the RF spectrum. This article studies the characterization of Line-of-Sight (LOS) optical performance in an Outdoor Wireless Visible Light Communication (OWVLC) system employing a Multiple-Input Multiple-Output (MIMO) technique for I2 V communications in ITS regulations. We design the new configuration of the OWVLC-I2 V system, which is an alternative approach to communication for I2 V system at nighttime. The results show the Channel Impulse Response (CIR) of the LOS links in visible light communication for I2 V system in ITS by investigating the receiver on the vehicle moving along the coverage communication area. Furthermore, the OWVLC-I2 V system using the MIMO technique depicts the performance of throughput and Bit Error Rate (BER) vs. vehicle speed while the vehicle passes a street light.

A comprehensive review of visible light communication (VLC)

Visible Light Communication (VLC) represents a revolutionary approach in the realm of wireless communication, capitalizing on the dual functionality of Light Emitting Diodes (LEDs) for both illumination and high-speed data transmission. The advent of LEDs has not only transformed lighting systems but has also paved the way for innovative communication technologies. The seamless integration of illumination and data transmission in VLC offers a unique solution to the growing demand for efficient and high-speed wireless communication. In recent years, the field of visible light communication has witnessed remarkable progress, fueled by the exploration and refinement of its constituent elements. Researchers have been actively addressing challenges associated with VLC, such as signal interference, mobility issues, and the need for standardized protocols. This ongoing pursuit of solutions has led to the development of increasingly robust VLC systems, positioning them as promising contenders for future communication technologies. This paper endeavors to provide a comprehensive overview of VLC, delving into the intricacies of its underlying challenges and the innovative solutions that researchers have proposed to overcome them. By examining recent research trends, the paper aims to highlight the evolving landscape of VLC technology, showcasing its potential for revolutionizing optical wireless communication. As VLC continues to mature, it is essential to explore the current state of the technology, anticipate future advancements, and contribute to the collective knowledge shaping the trajectory of visible light communication.

Secrecy Sum-Rate Enhancement for NOMA-VLC System With Pseudo User

Non-orthogonal multiple access (NOMA) enabled visible light communication (VLC) system is vulnerable to malicious eavesdropping, mainly because of the inherent broadcast nature of VLC technology. To this end, this letter proposes a novel concept called pseudo user (PU), which obstructs the successive interference cancellation (SIC) procedures of the eavesdropper. The minimum-feasible (MF) power allocation policy toward the PU is obtained under different power allocation strategies. Then, the secrecy sum-rate and user fairness along with the sum-rate are evaluated under both perfect SIC (pSIC) and imperfect SIC (ipSIC) scenarios. Results show that compared with the benchmark scheme without PU, the secrecy sum-rate and user fairness are both greatly enhanced with slight sum-rate loss. Furthermore, this letter proves that with much lower computations, the proposed scheme yields close-to-optimum secrecy sum-rate and user fairness performance provided by the exhaustive search algorithm in the pSIC scenario.