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- 2018
- imgae sensor
- internet of things
- drone
- visible light ID
- Signal-to-Noise Ratio (SNR)
- Infinite Gain Multiple Feedback (IGMF)
- Visible Light Communications (VLC)
- LED
- Trans-Impedance Amplifier (TIA)
- Optoelectronic Information Science and Engineering
- Tohoku University
- University of Northumbria
- University of Huddersfield
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An Overview of OFDM-Based Visible Light Communication Systems From the Perspective of Energy Efficiency Versus Spectral Efficiency
摘要： In this paper, the energy ef?ciency and the spectral ef?ciency for orthogonal frequency division multiplexing (OFDM)-based visible light communication schemes are studied, which is crucial for practical application with limited energy resources. The conventional schemes, including asymmetrically clipped optical OFDM (ACO-OFDM), pulse-amplitude-modulated discrete multitone, and direct current biased optical OFDM, are compared in terms of energy ef?ciency and spectral ef?ciency relationship. The in?uence of power allocation for asymmetrically clipped dc biased optical OFDM and hybrid ACO-OFDM is also investigated. The energy ef?ciency and spectral ef?ciency of layered ACO-OFDM with a variable layer number are calculated and their relationship is also formulated. These conventional and hybrid modulation schemes are analyzed and compared through computer simulations, which should be considered in practice according to the requirements of illumination and transmission.
关键词： visible light communication (VLC),spectral ef?ciency,orthogonal frequency division multiplexing (OFDM),Energy ef?ciency
更新于2025-09-09 09:28:46
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Fast electron transfer and enhanced visible light photocatalytic activity by using poly-o-phenylenediamine modified AgCl/g-C3N4 nanosheets
摘要： Exfoliation of bulk graphitic carbon nitride (g-C3N4) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g-C3N4 nanosheets (CN) have larger specific surface areas and more reaction sites. In addition, poly-o-phenylenediamine (PoPD) can improve the electrical conductivity and photocatalytic activity of semiconductor materials. Here, the novel efficient composite PoPD/AgCl/g-C3N4 nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach. The obtained photocatalysts have larger specific surface areas and could achieve better visible-light response. However, silver chloride (AgCl) is susceptible to agglomeration and photocorrosion. The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density, which is three times that of CN. Obviously enhanced photocatalytic activities of PoPD/AgCl/g-C3N4 are revealed through the photodegradation of tetracycline. The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly. Furthermore, ?O2? and h+ are the main active species, which are confirmed through a trapping experiment and ESR spin-trap technique. Therefore, the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst, in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles. This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues.
关键词： AgCl,Visible light irradiation,Poly-o-phenylenediamine,g-C3N4 nanosheets,Photocatalytic
更新于2025-09-09 09:28:46
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[IEEE 2018 Condition Monitoring and Diagnosis (CMD) - Perth, WA (2018.9.23-2018.9.26)] 2018 Condition Monitoring and Diagnosis (CMD) - Infrared and Visible Image Fusion of Electric Equipment Using FDST and DC-PCNN
摘要： Multi-sensor image fusion leads to more abundant details and a better description of the electric equipment monitoring scene. To improve the accuracy of overheating fault localization, a novel image fusion method based on Finite Discrete Shearlet Transform (FDST) and Dual-Channel Pulse Coupled Neuron Network (DC-PCNN) is proposed for fusing infrared and visible images of electric equipment. Firstly, FDST is utilized to decompose the source images. Then, two modi?ed-spatial-frequency motivated DC-PCNNs with different linking strengths are used to fuse low-frequency and high-frequency subbands. Finally, the ?nal fused image is reconstructed from the fused subbands by inverse FDST. Experimental results demonstrate the proposed method can achieve a remarkable improvement in preserving detail information and outperform other typical fusion methods in both overall visual performance and objective criteria.
关键词： infrared and visible images,electric equipment,DC-PCNN,image fusion,FDST
更新于2025-09-09 09:28:46
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - Performance Comparison of MIMO CAP Receivers in Visible Light Communication
摘要： Multiple-input, multiple-output (MIMO) techniques have recently been proposed to improve the spectral ef?ciency of the conventional carrierless amplitude and phase (CAP) implementation modulation scheme while maintaining its simplicity in visible light communication (VLC). The proposed MIMO CAP uses the optimum Maximum Likelihood (ML) detection scheme which has high computational complexity. As a result, four practical, low-complexity detection schemes are investigated for MIMO CAP in this work and their performances are compared with that of ML. It is found that the minimum mean square error detection with optimally-ordered successive interference cancellation (MMSE-OSIC) offers the best choice between complexity and bit-error rate (BER) performance. To achieve a spectral ef?ciency of 8 bits/s/Hz at BER of 10?4 in a 4 × 8 MIMO CAP system, the signal-to-noise ratio (SNR) requirement of the MMSE-OSIC is 5 dB higher than that of the optimum ML receiver. However, the ML receiver’s complexity is an order of magnitude higher than that of the MMSE-OSIC.
关键词： spatial multiplexing (SM),visible light communication (VLC),carrierless amplitude and phase modulation (CAP),optical communication,MIMO
更新于2025-09-09 09:28:46
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Deployment Issues and Performance Study in a Relay-Assisted Indoor Visible Light Communication System
摘要： This paper investigates the deployment issues and analyzes the performance of a relay-assisted indoor visible light communications (VLC) system with dc-biased optical orthogonal frequency division modulation (DCO-OFDM). The study considers two light sources in an office environment. One light source works as the information source and is located at the ceiling while the other one works as the relay terminal, which usually is a desk light or a floor light. We analyze the general blockage in a room, discuss the path loss of the VLC channel, and compare received signal power from a line of sight (LOS) link and a non-LOS link. The constraints on the relay height in order to achieve LOS connection are investigated. Simplified optimal power allocation under illumination and blockage constraints is proposed. Bit error rate performance is analyzed and the required signal power is derived for the relay-assisted DCO-OFDM VLC system. The study shows that in a relay-assisted VLC system, the blockage of source to destination link has trivial influence on the overall system performance if relays are properly deployed.
关键词： indoor,visible light communications (VLC),dc-biased optical orthogonal frequency division modulation (DCO-OFDM),relay,Channel model,power allocation
更新于2025-09-09 09:28:46
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Fabrication of Novel ZIF-8@BiVO4 Composite with Enhanced Photocatalytic Performance
摘要： In this work, a novel metal-organic framework (MOF) and BiVO4 (BVO) composite photocatalyst was successfully synthesized by an in-situ growth method. The characterization of obtained samples was done by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, N2 adsorption, and photoluminescence spectroscopy. The photocatalytic performance of ZIF-8@BiVO4 composite was evaluated by the degradation of methylene blue (MB) under simulated visible light irradiation. Compared with the mixture of BVO and ZIF-8, the composite photocatalyst exhibited superior photodegradation ef?ciency, which could be attributed to the synergistic effect between BVO and ZIF-8. The reduced recombination of photogenerated electrons and holes was considered to be an important reason for the enhancement of photocatalytic performance. This design demonstrates a rational method to improve the photocatalytic performance by combining photocatalysts with MOFs.
关键词： photocatalyst,BiVO4,MOFs,visible light
更新于2025-09-09 09:28:46
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Photo Protection against Visible Light Induced Pigmentation
摘要： This paper presents in vivo an in vitro studies demonstrating the induction of pigmentation in human skin by visible light which can be blocked by using formulation containing the correct amount of yellow iron oxide (YIO). An in vitro absorption method was developed to determine the protection provided by a test formulation containing 4.5% YIO using an IPD UVA-VIS action spectrum. Following the development of the in vitro method and in vivo study with 10 normal healthy volunteers with Fitzpatrick skin phototypes IV to VI was conducted to verify if the predictive model. The in vitro model for visible light protection provided a protection factor of 2.5 using the in vitro absorption spectrum of 4.5% of YIO with a very similar result from the in vivo study with a protection factor of 3.0. Multiple daily exposures of visible light have shown increase in skin pigmentation and the application of YIO provide less development of pigmentation when compared to unprotected skin. In vitro testing of the absorbance of the pigmented formulation using a proposed action spectrum for immediate pigment darkening (IPD) response in the visible light range supports the in vivo protection observations for persistent pigment darkening (PPD) and can be used as predictor for skin pigmentation induced by visible light.
关键词： visible light,in vitro,in vivo,yellow iron oxide,pigmentation
更新于2025-09-09 09:28:46
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Visible Light Communications (Theory and Applications) || VLC for Indoor Positioning
摘要： As the world has become an increasingly connected ecosystem, data demand has continually pushed the limits of our wireless networks. Each generation of wireless technology has added extensive wireless capacity; however, novel use cases and technological adoption have continually raised the demand at rates previously unseen. This trend continues today as massive data downloads, video streaming, augmented reality, and the Internet of Things push the limits of 4G networks. Furthermore, increasing application complexity and demand per device is paired with an increasing number and density of wireless devices. Hence, the wireless communications industry is challenged to meet an extreme growth in data traffic in the coming years—a demand growth that is unlikely to be met with iterative modifications to the current infrastructure. With this in mind, the world mobile and wireless infrastructure community is looking toward the 5th generation of mobile telecommunications, or 5G, with the expectation that new technologies will be adopted which drastically alter the conventional view of wireless networks.
关键词： Visible Light Communications,Software Defined VLC,RF/VLC HetNets,VLC,5G
更新于2025-09-09 09:28:46
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Visible Light Communications (Theory and Applications) || Lighting and Communications: Devices and Systems
摘要： An important step in the design of a visible light communications (VLC) system is to comprehend the limitations arising from the optical wireless channel. Accurate channel characterization is an important prerequisite to set the system parameters appropriately in order to establish a high-quality link since it permits better exploitation of the available energy and spectral resources in view of optimizing the system design. An accurate channel model is also necessary to precisely predict the performance of VLC systems. In this chapter, we address channel modeling for VLC systems mainly focusing on indoor systems. We introduce different sources of impairment in VLC systems arising from beam propagation or transmitter (Tx)/receiver (Rx) devices. Indeed, the latter could be attributed to the “global channel” comprising the blocks between the signal Tx and signal detection at the Rx. After this introduction, we give an overview of different propagation modes in Section 3.2. In addition, we explain methods for numerical channel simulation. Analytical channel modeling for the cases of single- and multiple-source systems is presented in Section 3.3. Then, in Section 3.4, we outline the limitations arising from the aggregate channel while focusing on the problem of intersymbol interference (ISI) and how it affects the link performance particularly in the absence of a line of sight (LOS). This could be due to multipath-induced channel time dispersion, that is, multiple reflections from people and objects within an indoor environment, the lack of sufficient bandwidth of the transmitting device, most commonly a light-emitting diode (LED), the photodetector (PD), and the cabling used for lighting installations. Limitations due to the LED nonlinear characteristics could also be considered as an impairment of the global channel, which is the subject of Section 3.5 where channel distortion modeling is investigated. Finally, channel modeling for multiple-input multiple-output (MIMO) VLC systems will be presented next in Section 3.6.
关键词： Channel Modeling,Intersymbol Interference,Multiple-Input Multiple-Output,Optical Wireless Channel,Visible Light Communications
更新于2025-09-09 09:28:46
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Photoelectrocatalytic Reduction of Carbon Dioxide to Methanol using CuFe2O4 Modified with Graphene Oxide under Visible Light Irradiation
摘要： Photoelectrocatalytic reduction of CO2 into valuable products can provide energy in a sustainable way with levelling off the concentration of CO2 in our environment. In this study, graphene oxide (GO) incorporated with copper ferrite (CuFe2O4) has been employed to enhance photoelectrocatalytic CO2 reduction under visible light. The TEM and XPS characterization indicated a strong interaction between the CuFe2O4 and GO in the hybrid catalyst. The GO incorporation reduced the e-/h+ recombination in the hybrid catalyst by trapping the photoexcited electrons from CuFe2O4 leading to high methanol yield of 28.8 μmole/Lcm-2 at 20.5% quantum efficiency. The incident photon current efficiency (IPCE) and Faradaic efficiency for methanol formation were observed 8.02% and 87% respectively. The results showed that the photoelectrocatalytic activity for CO2 reduction can be improved by incorporating GO with CuFe2O4 and it provides a universal platform to fabricate GO-CuFe2O4 based hybrid photocatalyst with promising applications in CO2 reduction.
关键词： Visible light irradiation,CuFe2O4,CO2,Graphene oxide,Photoelectrocatalytic reduction,Methanol
更新于2025-09-09 09:28:46