• Title/Summary/Keyword: VLC

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Flicker-Free Visible Light Communication System Using Byte-Inverted Transmission (바이트반전 전송방식을 이용한 플리커 방지 가시광통신시스템)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.26 no.6
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    • pp.408-413
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    • 2017
  • In this paper, we newly developed a byte-inverted transmission method for flicker-free visible light communication (VLC). The VLC transmitter sends original data in the former half period of the clock, and inverted data and in the latter half period of the clock. The VLC receiver receives the original data in the in the former half period of the clock. In this system, we used 480Hz clock that was generated from the 60Hz power line. The average optical power of the LED array in the transmitter is constant, thus flicker-free, in the observation time longer than the period of the clock that is about 2ms. This period is shorter than the maximum flickering time period (MFTP) of 5ms that is generally considered to be safe. This configuration is very useful in constructing indoor wireless sensor networks using LED light because it is flicker-free and does not require additional transmission channel for clock transmission.

Flicker Prevention Through Transition-Frequency Modulation in Visible Light Communication (가시광통신에서 천이주파수 변조를 이용한 플리커 방지)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.29 no.4
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    • pp.243-248
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    • 2020
  • In this study, we applied transition-frequency modulation to prevent the flickering of light-emitting diodes (LEDs) in visible light communication (VLC). In the VLC transmitter, rectangular waveforms with transition frequencies of four and two in each bit time were used for the high and low bits, respectively, in the non-return-to-zero data. In the VLC receiver, an RC-high-pass filter (HPF) was used to eliminate the interference of the 120 Hz noise light from the adjacent lighting lamps, and an SR-latch circuit was used to recover the transmitted signal using spikes from the output of the RC-HPF. This configuration is useful for constructing VLC systems that are flicker-free and resistant to adjacent noise light interference.

Implementation of Transceiver for Optical Wireless Communication System (광무선통신 시스템의 송수신기 구현)

  • Lee, Sun Yui;Kim, Jin Young
    • Journal of Satellite, Information and Communications
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    • v.8 no.1
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    • pp.71-76
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    • 2013
  • In this paper, a transceiver of VLC (Visible Light Communication) using LED white lighting has been implemented. The transmitted waveforms of LED and PD (Photo Diode) of the received signal are analyze to restore VLC data. Audio signal was successfully transmitted to demonstrate possibility and potential of optical wireless communication systems. Various modulation formats are considered to evaluate and compare performance in diverse channel conditions.

High-performance TDM-MIMO-VLC Using RGB LEDs in Indoor Multiuser Environments

  • Sewaiwar, Atul;Chung, Yeon-Ho
    • Current Optics and Photonics
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    • v.1 no.4
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    • pp.289-294
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    • 2017
  • A high-performance time-division multiplexing (TDM) -based multiuser (MU) multiple-input multipleoutput (MIMO) system for efficient indoor visible-light communication (VLC) is presented. In this work, a MIMO technique based on RGB light-emitting diodes (LEDs) with selection combining (SC) is utilized for data transmission. That is, the proposed scheme employs RGB LEDs for parallel transmission of user data and transmits MU data in predefined slots of a time frame with a simple and efficient design, to schedule the transmission times for multiple users. Simulation results demonstrate that the proposed scheme offers an approximately 6 dB gain in signal-to-noise ratio (SNR) at a bit error rate (BER) of $3{\times}10^{-5}$, as compared to conventional MU single-input single-output (SISO) systems. Moreover, a data rate of 66.7 Mbps/user at a BER of $10^{-3}$ is achieved for 10 users in indoor VLC environments.

Overview of LED Communication Networks

  • Huynh, Vu Van;Le, Nam-Tuan;Uddin, Muhammad Shahin;Choi, Sun-Woong;Jang, Yeong-Min
    • Information and Communications Magazine
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    • v.28 no.12
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    • pp.50-60
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    • 2011
  • Visible light communication(VLC) is one type of short-range, optical, and wireless communication system utilizing light emitting diode(LED) and laser diode(LD) as optical source. In a VLC system, visible light is used as a transmission medium and used to illuminate. Using VLC has a lot of advantages: it is harmless to human body; it transmits with high power, and it has excellent security, a high data rate, and a license free frequency band. With such a unique blend of communication and illumination in one system, the most common application would be an indoor environment. We aim at reviewing key issues in VLC network such as : FOV(field of view), priority MAC, cooperative MAC, link switching, LED-ID technique, cell site diversity, and link recovery.

Internet of Things based on Visible Light Communications: Testbed Experimentations (가시광 통신 기반 사물인터넷 환경 구축 및 실험)

  • Kim, So-Yong;Kim, Cheol-Min;Kim, Byung-Oh;Koh, Seok-Joo
    • Proceedings of the Korea Information Processing Society Conference
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    • 2018.10a
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    • pp.939-942
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    • 2018
  • 최근 LED 조명을 활용한 가시광 통신(VLC: Visible Light Communications)기술이 주목을 받고 있다. 가시광 통신 기술은 Bluetooth, ZigBee 등과 함께 새로운 인터넷 접속 기술로 활용될 수 있으나 전송 용량의 한계 때문에 실제 적용이 힘든 상황이다. 본 논문에서는 이 문제를 해결하기 위해 키-값 데이터베이스 패러다임을 적용한 가시광 통신 기반의 사물인터넷(IoT: Internet of Things) 모델을 제시한다. 제안하는 IoT 환경은 플렛폼 서버, 게이트웨이, VLC 송신기 및 VLC 수신기로 구성된다. IoT 통신을 위한 각 장비의 기능 및 프로토콜 스텍을 설계하고 실험 환경에서 각 장치의 초기화 절차 및 데이터 전송 과정을 검증하였다. 실험결과, 각 장비의 초기 구동 시간을 포함하여 1분 이내에 VLC 기반의 IoT 환경 구축이 가능함을 확인하였다.

Dimming Control in Visible Light Communication Using Subcarrier Modulation of Manchester Code (맨체스터 코드의 부반송파 변조를 이용한 가시광통신의 조명제어)

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.28 no.3
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    • pp.191-197
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    • 2019
  • In this study, we propose a dimming control method for a visible light communication (VLC) system, in which the subcarrier on-off keying (OOK) modulation of Manchester code is used for data transmission. In the VLC transmitter, non-return-to-zero (NRZ) code data is transformed to Manchester code, which is OOK modulated with a subcarrier. Manchester code is used for flicker-free lighting; the duty factor is changed for dimming control, and the subcarrier is used for preventing the adjacent noise light interference. In the experiments, the dimming control was carried out from about 8%-92% of the continuous wave (CW) LED light. This configuration is simple and effective in constructing a VLC system for indoor wireless sensor networks with flicker-free illumination and dimming control capability without adjacent noise light interference.

Indoor Location-based Emergency Call Service System for Ships using VLC Technology (가시광통신을 이용한 선박 내 위치 기반 응급호출 시스템)

  • Hong, Seung-Beom;Lee, Kyou-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.12
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    • pp.2836-2843
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    • 2015
  • Due to metallicity of materials, a vessel has a limitation to adopt RF-based wireless communication technologies for the inner communication means. Visible Light Communication(VLC) can be a sound alternative to dissolve such a limitation. Using a visual light as a transmission medium, VLC is free from radio interferences and restriction of radio usages which are typically related to RF-based wireless communications. In addition, VLC can not only require the facility cost relatively low because of being possibly converged with existing LED illumination, but also be harmless to the human body. This paper proposes an indoor location-based emergency call service system solution for ships using the VLC technology that supports 256Kbps data rate and 5m transmission distance. This paper presents real implementation and testing results of the solution which verifies the propriety of the proposal.

Investigation of visible light communication transceiver applicable to both of illumination and wireless communication (조명 및 무선통신이 동시에 가능한 가시광 송수신기에 관한 연구)

  • Song, Seok-Su;Kong, Young-Sik;Park, Jin-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.4A
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    • pp.219-226
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    • 2012
  • We investigated the performance of a visible light communication (VLC) transceiver applicable to both of illumination and wireless communication. we considered the visibility of VLC, the easy connection for wireless communication and high-speed transmission and implemented VLC transceiver based on edge-emitting laser diode and silicon photodiode. The proposed VLC transceiver is designated to operate in a full duplex mode at high speed of 120 Mbit/s. The shielding method that is employed as a means to reduce the light cross coupling effect inside the VLC transceiver is proposed and its performance is experimentally measured. We also applied optical antenna to have the larger angle of field of view (FOV) to novel structure of VLC transceiver and examined and analyzed their bit error rate performance, photometric result with respect to the transmission distance, the coverage range and the tilt degree as transmission link characteristic between two transceivers without optical antenna and with optical antenna.

Development of Visible Light Communication (VLC) System Technology Based on High Brightness LED light (고휘도 LED 조명 기술을 이용한 고속 가시광통신 시스템 기술 개발)

  • Lee, Jong-Hyeok;Jang, Kyung-Soon;Kim, Byung-Gyu;Kim, Jin-Ho
    • Convergence Security Journal
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    • v.14 no.7
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    • pp.29-36
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    • 2014
  • In this study, we design and develop a VLC test-bed system which has been recently issued and focused as good convergence technology in the world. We classify the developed system into transmission part including analog LED driver module, digital signal modulation module, and receiver part with light sensing module and signal demodulation module. Then we introduce important characteristics and components. We analyze some factors for each module. To validate the communication of the designed VLC system, we develop a VLC sender-receiver simulator which can control the dimming factor and flicker-free effect. From the developed system, we observed about 12Mbps of data transmission rate with 0.5m~1m of distance, without packet loss. We verified the real-time communication with multimedia streaming which can be considered as very high date rate. The developed system and technology will be useful for some converged data services like indoor positing, home appliances, and indoor parking system.