Nested PPM for Visible Light Communication With Heterogeneous Optical Receivers

With the recent successful standardization of broadband power line communication (PLC) (IEEE 1901, ITU-T G.9960/61) and visible light communication (VLC) (IEEE 802.15.7), there is an excellent opportunity to consider their integration. In particular, there is inherent benefit to leveraging existing power line infrastructure to provide connectivity while exploiting energy-efficient LED illumination systems for wireless downlink. The ubiquity of LED lighting together with power line networks leads us to conclude that VLC will be a strong complementary wireless technology to indoor PLC much in the way that Wi-Fi currently supports broadband Ethernet connections. This paper will survey some aspects of both PLC and VLC and present new proposals for their integration.

While visible light communication (VLC) is expected to have a wide range of applications in the near future, the security vulnerabilities of this technology have not been well understood so far. In particular, due to the extremely short wavelength of visible light, the VLC channel presents several unique characteristics than its radio frequency counterparts, which impose new features on the VLC security. Taking a physical-layer security perspective, this paper studies the intrinsic secrecy capacity of VLC as induced by its special channel characteristics. Different from existing models that only consider the specular reflection in the VLC channel, a modified Monte Carlo ray tracing model is proposed to account for both the specular and the diffusive reflections, which is unique to VLC. A deep neural network model is also proposed to describe the spatial VLC channel response based on a limited number of channel response samples calculated from the ray tracing model. Based on these models the upper and the lower bounds of the VLC secrecy capacity are derived, which allow us to evaluate the VLC communication confidentiality against a comprehensive set of factors, including the locations of the transmitter, receiver, and eavesdropper, the VLC channel bandwidth, the ratio between the specular and diffusive reflections, and the reflection coefficient. Our results reveal that due to the different types of reflections, the VLC system becomes more vulnerable at specific locations where strong reflections exist.

Visible light communication technology is a wireless optical communication technology based on LED lighting. [1] Making use of the high speed response characteristic of LED, visible light communication technology can realize the dual functions of lighting and communication. As a new way of data access and a supplement to radio frequency communication, visible light communication has been widely concerned. This paper is based on the development of application-oriented visible light communication system based on intelligent terminal, in order to accelerate the practical process of visible light communication. By changing the traditional visible light receiving scheme and using smart phone as the receiving device of the visible light system, a visible light communication system based on intelligent terminal is built [2]. Through the research on the existing receiving algorithm, a new receiving algorithm is proposed to improve the adaptability and BER performance of the system.

Visible light positioning (VLP) is an emerging positioning technique that utilizes indoor light sources to broadcast archer locations through visible light communication (VLC). Benefited by the densely deployed light lamps, VLP holds the promise for more accurate positioning accuracy than RF based approaches, and thus enables interesting applications such as retail navigation and shelf-level advertising in supermarkets and shopping malls. However, we observe that in existing VLP systems, receiving devices are heavily burdened in handling light flickering for VLC. In order to prevent human from being disturbed, the VLC transmitter lamps have to transmit pulses in a high rate (over 1kHz). Since the pulse rate far exceeds the cameras' sampling capability (30fps), receiver design either requires customized light sensor with cumbersome calibration on receiving signal strength [2] or processing high resolution images to leverage rolling shutter effect of the CMOS camera to decode message [1]. The heavy burden on receiving devices motivated us to try getting rid of light flickers. Since human eyes normally can not perceive changes in polarization, the idea is to modulate polarization instead of intensity for communication. In this demo, we demonstrate the VLC system in our VLP design [3] which realizes this idea. It enables lightweight VLC that is even affordable in wearables (Google Glass), without incurring hardware modification or computation off-loading. Moreover, it also makes other types of illuminating light beyond LED light (even sun light) possible to construct communication, therefore eliminates the barrier for deploying future VLC-based applications. As detailed in the full paper [3], our design was inspired by the liquid crystal display (LCD), from which we borrowed polarizer and liquid crystal. Liquid crystal has the property to change the polarization of bypassing polarized light according to the applied voltage. We use polarizer to polarize illuminating light and leverage liquid crystal to modulate bits through changing the light's polarization. The receiver can thus detect changes in polarization with a polarizing film, through which different polarizations result in different intensities. Since the SNR of such communication channel may significantly vary with the mobility of receiving device, we propose to add a dispersion filter to the transmitter. The dispersion filter can cast different frequency of lights into different polarization directions so that SNR in different receiving directions are evened. With the above techniques, VLC transmitter generates signal in low baud rate and mobile devices can perform VLC through camera directly. The communication is long in distance and lightweight enough for resource-constrained devices since the information is carried in intensity changes rather than certain image patterns in rolling shutter approaches. In this demo, we will illustrate the prototype implementation of the VLC communication system. We use incandescent lamps as illuminating light sources. The transmitter consists of a polarizing film, a liquid crystal layer, a dispersor and a control board. The receiver is demonstrated in Android smartphone with polarizing film in front of the camera.

Recently, visible light communication (VLC) system has gained attention due to its higher data rate, wider spectrum, higher security, lower weight, extensive lifespan of LEDs, smaller sizes of apertures and lower power consumption, lower cost, and no health issues etc. The VLC is used to strengthen the radio frequency (RF) communication and it also improves the communication performance in short range such as homes, offices, corridors, hospitals, aircrafts etc. The VLC provides dual functionality, that is, illumination and communication through the same LED simultaneously. It needs fast switching of LED (which is not detectable by human eyes) along with some appropriate modulation schemes for VLC to provide communication and illumination simultaneously. Meanwhile, LED should be powered on for the duration of communication, which conversely creates two challenges. First, the LED would consume more electrical power, which makes the system expensive. Second, LED can also be used in a dimming mode to save the power. Dimming of LED decreases the data rate. The data rate is inadequate due to modulation bandwidth of high brightness LED. The power and the data rate can be achieved by using different modulation schemes or line encoding schemes. There are a number of other factors such as interference of sun light, reflection of mirror or other fluorescent or candescent light disturbing the communication due to visible light usage in communication, interference to other VLC devices, integration of VLC with existing architecture of communication system, that is, Wi-Fi. The rest of the chapter is organized as follows. Section 1.1 gives an overview of VLC, followed by the brief discussion on the VLC system architecture in Section 1.2. Section 1.3 highlights the applications of the VLC. The general modulation schemes are given in Section 1.4. Then, Section 1.5 discusses the power efficient techniques, spectral efficient techniques are covered in Section 1.6, and Section 1.7 demonstrates the interference cancellation techniques. This chapter also discusses a comparison of different modulation techniques in terms of power efficiency, spectral efficiency, and interference cancellation and concludes with the best suited technique for power, spectrum, and interference.

Fluoride-based thulium-doped visible light fiber amplifier (TmVLFA), which can be used to amplify the blue light signal for a visible light communication (VLC) system, is theoretically demonstrated for the first time according to the best of our knowledge. The transition rate equations and power propagation equations are solved to predict the dependence of the gain and noise figure on fiber parameters. The numerical results show that with the pump wavelength 1150nm and pump power 800mW, 2.75m long thulium-doped fiber can amplify blue light (480nm) signal up to 33.3dB, and the noise figure is in the range from 3.0 to 3.5 dB. The model and numerical results encourage the use of fiber amplifier in VLC system for blue light amplification to extend the range of VLC.

To transfer audio data using Visible Light Communication (VLC), Light Fidelity (Li-Fi) technology has been designed. This project aims to develop a system for faster and more secure transmission of data. At present, Bluetooth and Wi-Fi are two major short-range wireless technologies used for different wireless application. There are different disadvantages of these current technologies, such as costlier, higher power consumption, and data insecurity. There is a great demand, therefore, for a technology which can resolve all the disadvantages of current technology. VLC is an efficient alternate emerging. As a mode of transmission, this upcoming technology uses light. The visible light spectrum is operated by Li-Fi that is ten thousand times as many as the spectrum of radio wave. It uses visible light, rather than traditional radio waves, as a mode of transmission. Thus, it can be used in places where it is prohibited to use radio waves. Given its very high speed (3 to 108 meter/second), light is a source for high-speed communication needs. Light is always in straight line, but the atmospheric change bringing off the light rays deflection. The data rates in Multiple-Gigabit-per-second over a short distance could be provided with bandwidth of 300 THz available for VLC. Here, a VLC prototype is being developed with a significant increase in distance of transmission and an enhancement in channel capacity. An overview of audio transmission in VLC is provided by this prototype. Real-time audio broadcast prototype utilizing commercial Light Emitting Diode (LED) lamps is proposed in this paper. Experimental findings show that it is possible to provide realtime audio with a maximum distance of 2ft accomplished by proper layout of LED sources and concentration improvement effects. The lighting model is built and simulated within the room setting, which it shows a close relationship between light source layout and distribution of illuminance.

The Visible Light Communication (VLC) has the potential to provide dense and fast connectivity at low cost. In this paper, we propose WSWDC, a novel VLC enabled wireless small-world data center. It employs VLC links to achieve a fully wireless data center network (DCN) across racks for the first time. The using of VLC links eliminates hierarchical switches and inter-rack cables, and thus reducing hardware investment, as well as maintenance cost. More precisely, to simplify the configuration and control operations, we propose three DCN design rationales: (1) fully-wireless, all inter-rack links are wireless; (2) easy-deployable, it is not necessary to change the existing infrastructure inside data center; (3) plug-and-play, no extra centralized control operations are required. Previous proposals, however, cannot achieve the three rationales simultaneously. To this end, we first use regular VLC links to interconnect racks as a regular grid DCN. To further exploiting the benefits of VLC links, a few random VLC links are carefully introduced to update the wireless grid DCN as a wireless small-world DCN. To avoid the potential interference among VLC links, we deploy VLC transceivers at different height on the top of each rack. In this way, VLC links would not interfere with others at each height level. Moreover, we design a greedy but efficient routing method for any pair of racks using their identifiers as inputs. Comprehensive evaluation results indicate that our WSWDC exhibits good network performance.

Visible Light Communication (VLC) is a way of communication that uses visible light as information carrier to transmit optical signal in the air without wired channels. VLC is attracting more and more attention from the industry because of its good performance in electromagnetic radiation, environment and safety. However, it’s still a tough challenge to achieve high accuracy in real applications, due to the complexity of the environment and the limitations of devices and technology of VLC system. In this paper, the VLC systems’ developments and applications in indoor positioning are summarized, providing a reference to the further study of VLC systems.

Visible light communications (VLC) are gaining an important role in 6G network deployment scenarios. Although 6G networks are planned to deliver incredibly high throughput and fulfill new applications, present frequency bands may be insufficient. Furthermore, 6G will provide improved coverage by merging terrestrial networks with underwater, air, and space networks. So VLC is used instead of the standard wireless communications which is incapable of providing such high-data rates for the non-terrestrial networks. VLC is a power-efficient and safe wireless communication system that operates in the visible light spectrum. In addition, VLC overcomes RF communication bandwidth limitations. In this paper, the overall aggregated throughput, data rate, power, and spectrum-efficiency in VLC systems will be improved by promoting a novel unipolar system titled improved aggregated rate for optical orthogonal frequency division multiplexing (IARO-OFDM). Moreover, introducing the precoding peak to average power ratio (PAPR) reduction technique to get a power efficient system and enhance the VLC system performance. Also, the authors provide a mathematical description and evaluation for the proposed IARO-OFDM system, in addition to comparing the proposed one with other current approaches which demonstrate that IARO-OFDM has a high data rate ratio (43.75%) with an acceptable system bit error rate system performance compared to other existing schemes.

In the work, proposals have been developed for building a stand using GNU Radio for researching data transmission technology using visible light technology. Visible light communication (VLC) can be used to build high-bandwidth, high-speed wireless access networks. The main advantage of visible light communication is that RF signals are not obstructed. This makes it possible to use visible light communication in hospitals, on space stations, and so it makes it possible to communicate underwater. Security, simple implementation procedures and range characteristics, license-free, also increase the use of visible light communication for a variety of applications. The aim of this work is to provide guidance on the design and implementation of a visible light communication test bench using software-defined radio. The article describes the architecture of VLC, presents the possibilities of using Software Defined Radio as a starting point for developing commercial VLC applications SDR technology provides a framework that can help drive programs to market, generate interest from industry players, and shorten the time to market for future compliant products. The key issues in the implementation of the VLC system is to ensure the ability to transmit data for an LED luminaire with minimal changes in its lighting characteristics and production costs. Thus, this implementation can be improved by narrowing the gap between the industry and the research community. A prototype for visible light transmission was designed using software-defined radios to communicate between analog devices and the computer on which the signal is processed. Using this concept provides the system with sufficient flexibility and modularity to incorporate new features into a prototype without requiring a long development time. Conducted testing of this platform, during which it was possible to transfer a text file. It is concluded that this implementation of the visible light transmission stand can serve as a starting point for the development of low to medium bit rate commercial VLC applications.

Wireless communications refer to data transmissions in unguided propagation media through the use of wireless carriers such as radio frequency (RF) and visible light (VL) waves. The rising demand for high data rates, especially, in indoor scenarios, overloads conventional RF technologies. Therefore, technologies such as millimeter waves (mmWave) and cognitive radios have been adopted as possible solutions to overcome the spectrum scarcity and capacity limitations of the conventional RF systems. In parallel, visible light communication (VLC) has been proposed as an alternative solution, where a light source is used for both illumination and data transmission. In comparison to RF links, VLC links present a very high bandwidth that allows much higher data rates. VLC exhibits also immunity to interference from electromagnetic sources, has unlicensed channels, is a very low power consumption system, and has no health hazard. VLC is appealing for a wide range of applications including reliable communications with low latency such as vehicle safety communication. Despite the major advantages of VLC technology and a variety of its applications, its use has been hampered by its cons such as its dependence on a line of sight connectivity. Recently, hybrid RF/VLC systems were proposed to take advantage of the high capacity of VLC links and better connectivity of RF links. Thus, hybrid RF/VLC systems are envisioned as a key enabler to improve the user rates and mobility on the one hand and to optimize the capacity, interference and power consumption of the overall network on the other hand. This paper seeks to provide a detailed survey of hybrid RF/VLC systems. This paper represents an overview of the current developments in the hybrid RF/VLC systems, their benefits and limitations for both newcomers and expert researchers.

The proposed Q-learning optimized Internet of Things (IoT) integrated VLC system is highly suitable for indoor environments where electromagnetic interference (EMI), device density and real-time data transmission are critical challenges. Visible Light Communication (VLC) serves as an effective alternative to traditional RF communication by utilizing existing LED lighting infrastructure for dual-purpose illumination and data transmission. In such indoor settings the system enables real-time monitoring and secure transmission of vital information such as environmental data to an IoT-based cloud platform. The use of VLC in the visible light spectrum eliminates EMI making it ideal for environments where Radio Frequency (RF) communication is either restricted or unreliable. To adapt to dynamic indoor conditions such as human movement or changing light intensities the system employs Q-learning to continuously optimize transmission parameters like modulation index and power levels. This reinforcement learning approach ensures enhanced link reliability, reduced Bit Error Rate (BER) and stable communication under fluctuating indoor conditions. Additionally, the incorporation of Enhanced Asymmetrically Clipped Duty-Cycled Optical OFDM (EACDO-OFDM) improves spectral efficiency and power utilization thus making the solution energy-efficient and scalable for large-scale indoor IoT deployments. By integrating adaptive machine learning techniques with VLC and IoT the system delivers robust, intelligent and energy-conscious communication, well-suited for smart building automation, indoor sensing and real-time monitoring applications.

Visible Light Communication (VLC) has emerged as an attractive alternative to radio frequency (RF) communication, due to cost-effectiveness and being license free. It has also proved its applicability in automotive applications, as an alternative and/or a complement to the traditional RF-based communications. We investigate the suitability of VLC in Intelligent Transportation Systems (ITS) and discuss its advantages in terms of safety enhancement and improved efficiency of the ITS. In this thesis, a VLC-based Vehicle-to-Vehicle (V2V) system in practical environments, considering both Line-of-Sight (LOS) and Non-Line-of-Sight (NLOS) paths are presented. The thesis investigates robust communication between a Light Emitting Diodes (LEDs) based VLC emitter and Photodiodes (PDs) based VLC receiver. For consideration of a V2V communication system, we consider transmitter on vehicle headlights and receivers on taillight making 2 _ 2 Multiple-Input-Multiple-Output (MIMO) communication link. A closed-form expression of the Channel Impulse Response (CIR) is derived and the effect of various channel parameters is analyzed. Optical-Orthogonal Frequency Division Multiplexing (O-OFDM) with adaptive modulation schemes is proposed for system improvement. Its performance is evaluated in terms of Inter Symbol Interference (ISI) mitigation, and data rate improvement. Moreover, the effect of sunlight on the V2V-VLC Two denoising schemes are proposed and evaluated as a solution to combat the effect of the solar irradiance on the VLC signal. Firstly, we use a differential receiver for denoising purposes followed by k-Nearest Neighbour (kNN) based adaptive _ltering algorithm, which is a supervised Machine Learning (MLE) technique. The shadowing effect is also studied. Moreover, an application of VLC in Foglet based ITS is described. The simulation validation of the VLC-based V2V system is performed under various environmental conditions and scenarios. Obtained results emphasize the suitability of VLC technology for automobile applications,.

As a candidate wireless communication technology for future indoor scenarios, visible light communication (VLC) not only has the function of green illumination, but also can transmit data at high speed without occupying licensed spectrum resources. Therefore, it can offload the data traffic from the existing radio-frequency (RF) network. However, due to the rectilinear propagation of the visible light, the VLC coverage cannot always satisfy the traffic service. Several factors such as transmitted power, number of users, transmitted/received angle, and multiple access schemes affect the VLC coverage probability. In this paper, we utilize the user quality of experience (QoE) as the evaluation metric, and further, propose a new coverage model named as QoE probability coverage model which is defined as the LED coverage area projecting on the ground that the user can achieve a satisfying QoE with a certain probability. We investigate how the factors including non-orthogonal multiple access (NOMA) scheme, number of user, user density etc. affect the QoE probability coverage area. The research results may guide the design of the VLC network deployment, multiple access protocol and handover schemes.