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- 摘要
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[IEEE 2018 International Conference on Advanced Technologies for Communications (ATC) - Ho Chi Minh City, Vietnam (2018.10.18-2018.10.20)] 2018 International Conference on Advanced Technologies for Communications (ATC) - Demonstration of A Visible Light Receiver Using Rolling-Shutter Smartphone Camera
摘要： Visible Light Communication (VLC) which has a mass of applications is getting much attention in both academic field and industry. Specifically, light-to-camera (LTC) communications in which information is transmitted to user through visible light signals; whereas, rolling-shutter camera-based receivers are utilized to capture and decode transmitted signals. In this paper, we present a demonstration of LTC communications system which includes a pair of transmitter and receiver. We have used an Arduino Genuino board to implement VLC transmitters which can transmit the identification (ID) messages through light-emitting diodes (LEDs)-based front-ends. At the receiver, we have developed an Android application which utilizes the CMOS image sensor (CIS) of the smartphone camera to receive the light signals. Besides, some practical problems of our LTC prototype and their solutions are also introduced in this paper.
关键词： Optical Camera Communication,Light-to-Camera,Rolling Shutter,Visible Light Communications (VLC)
更新于2025-09-23 15:23:52
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Layered Adaptive Collaborative Constellation for MIMO Visible Light Communication
摘要： In this paper, we propose a novel technique to effectively design a channel adaptive collaborative constellation called the layered adaptive collaborative constellation (LACC) for multiple-input multiple-output visible light communications. Recently, a channel-adaptive space-collaborative constellation (CASCC) that designs the constellation with the consideration of channel into the model to improve the receiver mobility and enhance the error performance. However, this scheme only considers into optimization four constellation points that form a diamond shape in the receiver space. Our proposed scheme effectively exploits the layered structure of collaborative constellation and overcomes the aforementioned drawbacks of CASCC. Furthermore, an improved low-complexity maximum likelihood (ML)-based detector is derived. Simulation results show that the LACC can achieve some performance gain, compared with previous constellation design schemes for different scenarios, especially really high-correlation channels and under imperfect channel state information. Moreover, the proposed detector drastically reduces computational complexity while maintaining the same performance as a traditional ML detector.
关键词： maximum likelihood (ML) detection,multiple-input multiple-output (MIMO),Visible light communications (VLC),space collaborative constellation
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on Internet of Things and Intelligence System (IOTAIS) - BALI, Indonesia (2018.11.1-2018.11.3)] 2018 IEEE International Conference on Internet of Things and Intelligence System (IOTAIS) - Optical Internet of Things within 5G: Applications and Challenges
摘要： The fifth generation (5G) telecommunications standards are being developed to meet the growing demands for high-speed wireless networks (i.e., few tens of Gigabits per second). The 5G standard stems largely from an increasing number of users and plethora of different devices, collectively referred to as smart devices, connecting to a network as part of Internet-of-Things (IoT). A few potential technologies have emerged for 5G such as millimeter waves, massive multiple-input multiple-output, and small cell communications. Although these technologies would satisfy the requirements of 5G, there is a complementary alternative wireless technology of optical wireless communications (OWC), which is being considered. As part of OWC, visible light communications (VLC) and optical camera communications (OCC) are the most attractive options for 5G networks and beyond. VLC with huge frequency spectrum integrated with IoT can open up a wide range of indoor and outdoor applications as part of future smart environments. This paper provides an overview of the all-optical IoT (OIoT) focusing on VLC and OCC based potential applications and challenges as part of 5G standards.
关键词： light emitting diodes (LEDs),visible light communications (VLC),Internet of things (IoT),Optical wireless communications (OWC),optical camera communications (OCC)
更新于2025-09-23 15:22:29
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Design of PAM-DMT-based Hybrid Optical OFDM for Visible Light Communications
摘要： In this letter, a pulse-amplitude-modulated based hybrid optical orthogonal frequency division multiplexing (PHO-OFDM) scheme is proposed. We use the high order quadrature-amplitude-modulation to replace the one-dimensional pulse-amplitude-modulated on the even subcarriers for compensating the data capacity weakness of the conventional pulse amplitude modulated discrete multitone (PAM-DMT). The combined time-domain PHO-OFDM signal has a larger amplitude range than the original PAM-DMT but with a reduced peak-to-average power ratio (PAPR). Besides that, a flexible power allocation method is introduced to the proposed PHO-OFDM systems to fully exploit the whole dynamic range of LEDs. The simulation results show that, under the same average bit rate, the proposed PHO-OFDM scheme has a better bit error rate performance compared with the conventional PAM-DMT scheme, thus demonstrating its application potential in visible light communications.
关键词： visible light communications (VLC),pulse-amplitude-modulated discrete multitone (PAM-DMT),optical orthogonal frequency division multiplexing (O-OFDM)
更新于2025-09-23 15:22:29
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Indoor Localization Using K-Pairwise Light Emitting Diode Image-Sensor-Based Visible Light Positioning
摘要： A great deal of research has been devoted to studying indoor localization schemes for the development of location-based services. This study investigated an indoor localization system, including subsystems of non-line-of-sight (NLOS) image-sensor-based visible light communications (IS-VLC) and the proposed ??-pairwise light emitting diode (LED) image-sensor-based visible light positioning (IS-VLP), in a unified lighting environment. A smartphone received multiple LED identifiers through the designed NLOS IS-VLC and successfully performed the proposed ??-pairwise LED IS-VLP with ?? = 3 to achieve localization, with maximum localization errors of 2.92 cm and 3.54 cm being obtained for ceiling heights of 100 cm and 150 cm, respectively.
关键词： visible light communications (VLC),Image-sensor-based visible light positioning (VLP),light emitting diode (LED)
更新于2025-09-23 15:21:21
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Sub-carrier Loading Strategies for DCO-OFDM LED Communication
摘要： LEDs, particularly those used for Visible Light Communications (VLC), have a limited bandwidth, while above their 3 dB bandwidth, the roll-off is relatively gentle. If the modulation bandwidth would be limited to the 3 dB LED bandwidth, the achievable rate would be unacceptably constrained. Hence, effective communication systems need to optimize the use of bandwidth significantly above this 3 dB point. Orthogonal Frequency Division Multiplexing (OFDM) is a popular method to fine-tune the amount of power and constellation as a function of the channel response over different frequencies. Various power and bit loading strategies have been proposed and simulated in literature, but their performance was not captured in expressions. This manuscript derives these for optimal waterfilling, uniform and pre-emphasized power loading for the LED channel, that severely attenuates high frequencies. We also investigate the influence of practical discrete constellations and verify our new results experimentally. Interestingly, simple uniform loading only falls less than 1～2% short of the throughput achieved by waterfilling, but when we restrict OFDM to discrete QAM constellation sizes, the penalty for uniform loading is 1.5 dB. Inspired by the good performance of uniform power loading, we propose an algorithm to find the best discrete bit loading for uniform power within an optimized band. As pre-emphasis is nonetheless attractive because a flattened channel does not need adaptive sub-carrier loading, we quantify its penalty. This can be modest provided that the system can adapt its transmit bandwidth, thereby adaptively switching upper sub-carriers to zero power.
关键词： Orthogonal Frequency Division Multiplexing (OFDM),pre-emphasis,power loading strategies,LED channel,QAM constellation sizes,uniform loading,waterfilling,Visible Light Communications (VLC)
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE Energy Conversion Congress and Exposition (ECCE) - Baltimore, MD, USA (2019.9.29-2019.10.3)] 2019 IEEE Energy Conversion Congress and Exposition (ECCE) - An Energy Efficient Li-Fi Transmitter with Single Inductor Multiple Output LED Driver
摘要： High-Efficiency Light-Fidelity (Li-Fi) transmitter for simultaneous illumination and Visible Light Communications (VLC) using LED lighting is presented in this work. The proposed transmitter is based on Single Inductor Multiple Output (SIMO) buck converter with two independently controllable outputs or channels, namely lighting channel and communications channel for enabling flicker free illumination without affecting high-speed modulation of LEDs. By this approach, power converter switching frequency is decoupled from modulation frequency of LEDs, thereby optimizing SIMO converter switching frequency for efficiency and the VLC modulator frequency for high speed data transfers. GaN devices are used to realize VLC modulator for high speed modulation to further enhance the efficiency. Light output with high Color Rendering Index (CRI) is achieved by controlling white LEDs as primary illumination source at lighting channel and red color LEDs at communication channel. Simulations and experimental results to validate the proposed transmitter are presented.
关键词： Single Inductor Multiple Output Converters,Color Rendering Index(CRI),Light-Fidelity(Li-Fi),High Brightness Light Emitting Diodes(HB-LED),Visible Light Communications (VLC),IoT (Internet of Things)
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 2nd International Conference on Circuits, System and Simulation (ICCSS) - Guangzhou, China (2018.7.14-2018.7.16)] 2018 IEEE 2nd International Conference on Circuits, System and Simulation (ICCSS) - Application of an Infinite Gain Multiple Feedback Filter in VLC Link Range Extension
摘要： This paper presents a visible light communication (VLC) link range extension, achieved by establishing a VLC system using simple, low-cost, and reliable electronic circuitry, and employing a design of a highly resonant frequency selective active band pass filter (infinite gain multiple feedback filter) at the receiver section of the system. The filter was designed for a specific center (resonant) frequency with high Quality factor and gain. An outline of the relationship between Signal-to-Noise ratio (SNR) and transmission distance for three different center frequencies was presented. Results show that by utilizing an IGMF filter at the receiver, a signal-to- noise ratio above 10dB at a distance beyond 1.5 meters can be achieved without any form of lensing at either the transmitter or receiver.
关键词： Signal-to-Noise Ratio (SNR),Infinite Gain Multiple Feedback (IGMF),Visible Light Communications (VLC),LED,Trans-Impedance Amplifier (TIA)
更新于2025-09-10 09:29:36
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Design of Polar Codes for Run-Length Limited Codes in Visible Light Communications
摘要： In this paper, we proposed a design of polar codes for run-length limited (RLL) codes by using frozen bit indexes in visible light communications. Thanks to generator matrix structure and channel selection procedures of polar codes, pre-determined frozen indexes are defined to produce different number of segments. The indexes are used to make different a priori probabilities in RLL decoding to improve bit error rate (BER) performance. Simulation results show that the proposed algorithm provides better BERs than referenced schemes.
关键词： visible light communications (VLC),run-length limited (RLL) codes,polar codes
更新于2025-09-10 09:29:36
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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