Spectrally Efficient Cooperative Visible Light Communication with Adaptive Power Sharing for a Generalized System

A number of binary modulation schemes are proposed for LED based Visible Light Communication (VLC) systems to jointly achieve data transmission and brightness control. These binary modulation based solutions are spectrally inefficient because they consider the LED light source as single device. We observe that most of the commercial LED lights use more than one LED per light source and the possibility of individual current control of these LEDs would provide better brightness control resolution as well as higher data transmission rates. To achieve this we propose multi-level multi-pulse position modulation block coding scheme to jointly control multiple LEDs providing flicker free VLC link. The brightness level of the light source is controlled based on the number of LEDs switched on simultaneously. New algorithms are developed for symbol encoding/decoding as well as to enumerate the maximum number of symbols that can be encoded for the selected brightness level and the number of levels. Improvement in spectral efficiency is analyzed and compared with the contending binary modulation schemes.

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.

Visible Light Communication (VLC) has emerged as a powerful technique for wireless communication systems. Providing high data rate and increasing capacity are the major problems in VLC. Recent evidence suggests that Multiple Input Multiple Output (MIMO) technique can offers improved data rates and increased link range. This paper describes the design and implementation of visible light communication system in indoor environment exploring the benefits of MIMO. The specific objective of this research was to implement a 4×4 Multiple Input (LEDs) Multiple Output (photodetectors)-VLC communication system, where a 16 white power LEDs in four arrays are setting up at transmitter and four RX modules are setting up at receiver side without the need for additional power or bandwidth as well as analyze a mathematical model for a VLC- 4×4 MIMO with different modes such as the suitable angles to cover the entire room. The research designs practically an electronic circuit for the transmitter and receiver with inexpensive components. The power distribution of different propagation modes is calculated for Single Input Single Output (SISO) and MIMO channels in typical room dimensions. The results in this paper indicate that the power is distributed uniformly for entire room when implemented VLC-MIMO as compared to VLC-SISO. Furthermore, a 4×4 MIMO implementing VLC is compared in term of BER vs. SINR with SISO communication system for both Line of Sight (LOS) and Non Line of Sight (NLOS) propagation modes. Comparing the two results of LOS and NLOS, it can be seen that a 4×4 MIMO implementing VLC for LOS perform better than the same system with NLOS due to decreasing in the received power resulted from the multipath effect.

Visible light communication (VLC) is an emerging technology for public street lighting. The paper comprises two parts. A spatial scaled simulation model for Signal to Noise Ratio (SNR) analysis and a spatial scaled experiment are elaborated to evaluate the VLC propagation channel model in an inhomogeneous street lighting channel. As a first result, a minor improved non Line of Sight (NLoS) ceiling bounce simulation substantially agrees with the measurement. The model is sufficient adequate for a path loss estimation in a larger spatial dimension. As a second result, the receiver requires a huge aperture of 10 to 30 cm diameter for a communication performance of wireless sensor networks between the lights. The Line of Sight (LoS) link requires nearly a quarter of the surface but pointing errors are likely due to the rural outdoor environment. Furthermore, the spatial simulation resolution considering a small Field of View (FOV) influences the gain of up to 5 dB and has therefore been identified as a new error source in the NLoS propagation model whereby the influence is negligible at medium distances.

Due to directional propagation of light signals, visible light communication (VLC) channel quality is sensitive to the distance and the angle between a VLC access point (AP) and a VLC terminal. When a terminal is mobile, VLC channel gain varies with the position of the terminal. Considering rotations of a terminal during mobility, channel variations are even more severe. As a result, data rates need to be adapted according to variable link qualities. The commonly used feedback-based adaptive modulation and coding (AMC) scheme cannot catch up with channel variations in VLC, resulting in staircase-shaped adaptation results. Smoother adaptation can be achieved by the seamless rate adaptation (SRA) scheme via rate compatible modulation (RCM). However, SRA does not provide an effective way to increase symbol distances, so the improvement on spectral efficiency is small. To address the shortcomings in the existing schemes, rateless adaptation (RLA) is developed for VLC systems in this paper based on spinal codes. With RLA, smooth rate adaptation is accomplished without channel state information (CSI) feedback, and spectral efficiency is also greatly improved. Simulation results show that, in mobile scenarios, RLA achieves at least 46% improvement over AMC and 19% improvement over SRA in terms of spectral efficiency.

Visible light communication (VLC) is a subset of OWC. VLC deliberates line of sight (LOS) connections as well as different reflections from different paths. In a practical condition, LOS links could be affected due to the existence of the obstruction between LED transmitter and PD receiver. However, it is possible to create the wireless link in a non-line of sight (NLOS) scenario when the reflected light paths are present. Nevertheless, in terms of received signal strength indication (RSS), there is still a probability of demolishing the system performance. This paper presents a new and unique indoor visible light communication-based power maximization of received signal under the condition of NLOS. Based on a white light emitting diode, a photo-detector and evolutionary algorithm, genetic algorithm (GA) is a one type of evolutionary algorithm. In this paper, we have used GA which performs the maximization of the received power. Simulation result reflects the feasibility of the proposed methodology. The maximization of VLC-based power in NLOS condition can benefit smarter indoor communication in near-future VLC domain.KeywordsGenetic algorithmNon-line of sightOptical communicationVisible light communication

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.

Machine-to-machine (M2M) visible light communication (VLC) is a communication architecture that makes it possible for heterogeneous devices to interact without human intervention using visible light modulated at certain frequency to enable communication. M2M VLC based is one of the feasible applications of internet of things (IoTs). This paper proposed a machine type communication (MTC) for M2M VLC based with an incorporation of energy harvesting system using a power transfer unit (PTU) with a centralized VLC access point (AP) with a probabilistic model, where an investigation is performed to show the signal to noise ratio (SNR) distribution with a semi angle at half power of a chosen link. This is done by varying some parameters.This model considers the channel analysis and light emitting diodes (LEDs) are place at the ceiling showing how bit rate can be effected for VLC AP with equal separation for a mobile devices or users. Such network aims at interconnecting billions of devices while investing the throughput performance of the M2M VLC based where a cluster of energy harvesting devices communicating with a VLC AP. This paper aims at proposing a design at the physical layer using various modulation schemes, demodulation, synchronization, error correction and so forth to ensure optimal communication can be made to the internet. Both LEDs-based analog transceiver devices and photo-detectors are exploited. The method is implemented in simulation and considering the performance and flexibility of the system.

Visible light communication(VLC), which combines communication and illumination, is regarded as a potential wireless communication. For illumination requirements of VLC systems, dimming control is a significant function. Many schemes have been proposed for multi-input multi-output (MIMO) VLC systems or dimmable VLC systems, but few schemes combine the two. The dimming control scheme that has been proposed for MIMO-VLC systems in the reference still has a probability for improvement in spectral efficiency and error performance. This paper proposes a dimming control scheme that utilizes the constant weight space-time codes (CWSTC) to improve spectral efficiency and error performance for MIMO-VLC systems. Simultaneously, we also present the codeword structure and a low implementation complexity detection algorithm for the scheme. Finally, performance analysis and simulation results provide comparisons between the proposed scheme and other existing dimming control schemes.

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,.

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 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.

The integration of intelligent transportation systems (ITS) has become a common approach for reducing traffic congestion and enhancing the safety of roadways and underground tunnels. Visible light communication (VLC) has emerged as a promising alternative for vehicular environments, offering unlicensed optical spectrum, high data rates, and immunity to radio frequency (RF) interference. This study examines the performance of an orthogonal frequency division multiplexing (OFDM)-based VLC system employing Bose–Chaudhuri–Hocquenghem (BCH) coding for error correction, aiming to explore the physical layer characteristics of VLC systems in a vehicular tunnel environment. By utilizing MATLAB as a simulation tool, the channel model was analyzed by incorporating the line of sight (LOS) and non-line of sight (NLOS) propagation models, dynamic speed, and various data rates. At a vehicle speed of around 50 km/h, the simulated scenario was capable of attaining a bit error rate (BER) of 3.5 × 10−5 when the data rate was 1.5 Mbps. However, for a data rate of 2.4 Mbps, the BER value was 0.18 %, with a significant increment when exhibiting high speed due to the instant change in the channel conditions. The results offer valuable insights into the feasibility of VLC in underground tunnels and highlight the critical trade-offs between data rate, mobility, and link reliability in dynamic vehicular environments.

• Core Innovation & Objective • Developed a novel, integrated system architecture combining a modified USRP X310 software-defined radio platform with a custom-designed high-power LED optical transceiver. • Achieved high-speed, low-latency, and highly reliable audio-video transmission over Visible Light Communication (VLC) for intelligent transportation and vehicle-to-vehicle (V2V) applications, particularly in electromagnetically sensitive environments. • Key Technical Breakthroughs • LED Bandwidth Extension: Designed an innovative active pre-equalization circuit (based on a 4th-order high-pass RC bypass and op-amps) that dramatically increased the 3dB modulation bandwidth of a commercial 15W LED from 3 MHz to 120 MHz. • High-Speed Modulation: Successfully implemented 64QAM-OFDM modulation/demodulation using GNU Radio on the USRP, enabling spectrally efficient data transmission. • Advanced Optical Design: Custom-designed optical lenses (transmitter and receiver) and a high-power Bias-T circuit for efficient AC/DC coupling, ensuring the LED operates in its linear region and maximizing optical power transfer. • Stable Link Performance: Incorporated an Automatic Gain Control (AGC) circuit at the receiver, stabilizing the output voltage between 1.2V - 2.0V and maintaining a modulation signal-to-noise ratio (SNR) > 23 dB over varying distances. • Outstanding System Performance • The experimentally demonstrated performance metrics are exceptional for a VLC system: • Peak Data Rate: 500 Mbps • Communication Distance: 0 - 110 meters • Bit Error Rate (BER): As low as 1.74 × 10⁻⁵ (far below the 1 × 10⁻⁴ target) • End-to-End Latency: < 0.1 s • Beam Angle: 11.5° (Transmitter) • Field of View (FOV): ≤ 18° (Receiver) • System Integration and Design • Hardware-Software Co-Design: Seamless integration of the USRP X310 (handling digital baseband processing) with the custom analog optical front-end. • Compact and Practical: The system is designed for external mounting on vehicles, offering a practical solution for real-world deployment. • Simulation-Guided Design: Used LightTools for optical design and Optisystem for communication link simulation to validate the design before implementation. • Significance and Application Value • Solves Critical Challenges: Provides a high-speed, secure, and EMI-free communication alternative to traditional RF in environments like military operations, petroleum facilities, and intelligent transportation systems. • 6G Potential: Serves as a practical reference for the development of VLC as a complementary technology in 6G networks. • Demonstrates Feasibility: Successfully proves the viability of using commercial LEDs and USRP platforms for building high-performance, medium-to-long-range optical communication systems. • This work represents a significant step forward in practical high-speed VLC system design, combining theoretical innovation with robust engineering to achieve state-of-the-art performance. Existing vehicular VLC systems suffer from limited bandwidth, short transmission distances, low data rates, and support only a narrow range of communication services. To address these issues, this paper proposes a vehicle-mounted high-speed LED visible light communication (VLC) system based on Universal Software Radio Peripheral (USRP). Leveraging 64QAM-OFDM digital modulation, an improved USRP X310 hardware platform, and a PC, we establish a novel architecture comprising digital baseband and optical transceiver modules. The baseband module eliminates traditional spectrum-shifting circuits and antennas, retaining only FPGA and ADC/DAC units. Audio/video files undergo 64QAM-OFDM modulation directly on the PC, with modulated signals output via DAC to a custom-designed wide-bandwidth LED transceiver. A broadband hardware equalization network based on a fourth-order RC bypass circuit was designed expands the 3dB bandwidth of high-power LEDs from 3 MHz to 120 MHz. Combined with automatic gain control (AGC), this achieves an optical transceiver with 12–15 W output power, >23 dB optical modulation signal-to-noise ratio (SNR), and stable receiver output voltage (1.2–2.0 V). The resulting compact system delivers low latency, high data rates, and high reliability. Under aligned optical path conditions, the system achieves >1 Mbit/s at 110 m (BER 0.49 × 10⁻⁵, delay 0.009-0.05s) and a peak rate of 500 Mbit/s at 10 m (BER 7.4 × 10⁻⁵), with an 11.5° transmit angle and a receiver field of view (FOV) of less than 18°. This work demonstrates the feasibility of high-power LED-based 64QAM-OFDM communication using USRP X310 for medium- to long-range vehicular links, providing a reference for intelligent transportation systems.

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.