• Current Optics and Photonics
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• 제3권2호
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• pp.105-110
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• 2019

The visible-light communication (VLC) system is a promising candidate to fulfill the present and future demands for a high-speed, cost-effective, and larger-bandwidth communication system. VLC modulates the visible-light signals from solid-state LEDs to transmit data between transmitter and receiver, but the broadcasting and the line-of-sight propagation nature of visible-light signals make VLC a communication system with a limited operating range. We present a novel architecture to increase the operating range of VLC. In our proposed architecture, we guide the visible-light signals through the fiber and amplify the dissipated signals using visible-light fiber amplifiers (VLFAs), which are the most important and the novel devices needed for the proposed architecture of the VLC. Therefore, we design, analyze, and apply a VLFA to VLC, to overcome the inherent drawbacks of VLC. Numerical results show that under given constant conditions, the VLFA can amplify the signal up to 35.0 dB. We have analyzed the effects of fiber length, active ion concentration, pump power, and input signal power on the gain and the noise figure (NF).

• 한국위성정보통신학회논문지
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• 제10권2호
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• pp.46-53
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• 2015

Visible Light Communication (VLC)은 Light Emitting Diode (LED)를 사용하여 조명의 역할과 통신의 기능을 동시에 구현할 수 있는 효과적인 방법이다. VLC는 통신 가능 영역인 Field Of View (FOV)를 가져 높은 보안성을 가지고, 가시광을 이용해 고속의 데이터 전송이 가능하다. VLC 시스템에서 RGB 채널에 데이터를 분할하여 전송하는 방법은, RGB 채널에 동일한 데이터를 전송하는 방법에 비해 빠른 데이터 전송 속도를 가지고 있으나, 가시광의 산란 및 반사로 인한 데이터의 burst 에러가 발생할 시 복원이 불가능하여 BER 성능의 열화가 발생한다는 단점이 존재한다. 이러한 문제를 해결하기 위해 VLC에서 빠른 데이터 전송률을 가지면서 BER 성능 향상을 만족하는 2-step 인터리빙 기법을 제안한다. 제안 시스템의 Cyclic 인터리빙과 convolutional 인터리빙을 통해 RGB 채널의 성능 평준화 및 데이터 에러율의 감소로 전체 시스템의 BER 성능이 향상됨을 확인 할 수 있다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.273-276
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• 2008

This article describes a LED illumination infrastructure for ubiquitous society based on the Visible Light Communication technology. The VLC is one of the advanced communication system using "Visible Light". The VLC system has a lot of advantageous features and can be used in various places for the next future generation. So, we analyzed ubiquitous service model based on the VLC system and some applications. And we renewed discussion about LED illumination infrastructure for u-Society.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1502-1519
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• 2020

Recently, new devices have been developed for the Internet of Things concept. The devices commonly use RF (Radio Frequency) based wireless communication. With the increase in the number of devices, the space allocated for the radio frequency band in wireless communication fills rapidly. Visible Light Communication (VLC) is an alternative, secure and economical communication technology that uses light instead of radio frequencies. While Web of Things (WoT) is the adaptation of the experience and knowledge acquired from the web into the internet of things ecosystems. By combining these two technologies, the development of the Visible Light Communication for Web of Things (VLC4WoT) system, which can use VLC and WoT technologies, has been our motivation. In our study, microcontroller control circuit was created for VLC4WoT system. Control of the circuits over the internet was performed. VLC based receiver and transmitter units have been developed for wireless communication. Web based interface was created for control. The test apparatus consisting of four objects with four outputs and a transfer unit was carried out. In this test, communication was achieved successfully. It was presented in the study that VLC can be used in the web of things architecture. In the future, it is envisaged to use this system as a safe and economical system in indoor environments.

• 한국통신학회논문지
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• 제38C권9호
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• pp.797-801
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• 2013

Visible light communication (VLC) is a rapidly growing area of research and applications, due to the potential and predicted high efficiency of bandwidth. One of the key challenges in VLC technology is the choice of devices which are going to be deployed VLC features. Smartphone rationally uses the most widely deployed visible light sensor i.e. image sensor in camera, which could be used to receive the intensity modulated data. Image sensor based VLC system would be the most deployable scenario but initially the capacity was not much attractive compared with photodetector based VLC system. Here, the spatial multiplexing is proposed in MIMO based VLC system to increase the system capacity by utilizing the property of spatial separation of optical light sources in smartphone's camera module. The active pixels of imaging plane act as the multiple receivers which could be able to use on MIMO spatial multiplexing to enhance the system performance.

• 한국정보통신학회논문지
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• 제22권1호
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• pp.140-146
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• 2018

최근 실내조명으로 사용하는 LED(Light Emitting Diode)와 무선통신 기술을 융합한 가시광통신이 주목받고 있다. 하지만 가시광 통신은 광 신호를 측정할 수 있는 커버리지 내에서만 통신이 가능하고, 비가시선 영역에서 통신이 단절되는 현상이 발생한다. 본 논문에서는 가시광 통신의 커버리지 확장과 비가시선 영역에서 통신 단절 현상 개선을 위해 VLC(Visible Light Communication) 릴레이 모듈을 제안한다. 제안하는 VLC 릴레이 모듈은 송신기로부터 전달받은 패킷을 VLC 릴레이 모듈 및 수신기로 전송한다. 1개의 VLC 송신기와 3개의 VLC 릴레이 모듈을 설치하여 실험을 진행하였으며, VLC 릴레이 모듈의 증가에 따른 통신 커버리지 확장과 비가시선 영역에서 통신 단절 현상 개선을 확인하였다. 또한, 이중 샘플링 기법을 사용하여 광 신호 측정 성능이 2.4배 향상됨을 확인하였다.

• Current Optics and Photonics
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• 제2권4호
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• pp.308-314
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• 2018

Visible light communication (VLC) is considered a strong future candidate for indoor wireless communication. However, its performance seems to be relatively unsatisfactory when compared to wireless local area network (WLAN) communication using millimeter waves. To improve the performance of VLC, numerous technologies have been proposed so far, in both electrical and optical domains. Among the proposals, optical beamforming (OB) is an optical-domain technology that can concentrate light in a specific direction or on a target spot. It can significantly improve VLC performance and can be widely used, because it does not depend on electrical modulation schemes. Therefore, this review discusses the concept, principle, and types of OB, the structure of a VLC system using OB, performance results of OB, and the combination of OB with electrical signal modulation in VLC. OB is expected to be one of the key techniques in future VLC implementations, similar to radio-frequency beamforming in millimeter-wave communication.

• 센서학회지
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• 제24권3호
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• pp.145-150
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• 2015

We introduce a new method of time-division visible light communication (VLC) using LED lamp light for the generation of synchronizing pulses. The LED lamp, driven by an AC 220-V power line, radiates light that has a 120-Hz frequency component. The pulse generator in each VLC system receives the LED lamp light and generates the synchronizing pulses that are required for time-division transmission of multiple VLC channels. The pulse period is subdivided into several time slots for VLC channels. In experiments, 120-Hz synchronizing pulses were generated using LED lamp light, and three VLC channels were transmitted independently without interfering with each other in a condition where the VLC signals overlapped in space. This configuration is useful in constructing multiple wireless sensor networks that are safe and without interference in locations where LED lamps are used for illumination.

• 전자공학회논문지SC
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• 제48권5호
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• pp.1-6
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• 2011

LED(Light Emitting Diode) 소자는 현대 기술의 발달로 형광등이나 전구보다 수명이 길고 전력소모가 작으며 제어가 쉽다는 장점을 가지고 있다. 이러한 이유로 LED 소자를 이용한 조명이 많이 사용되고 있다. 최근 LED 소자의 고속응답특성을 이용한 통신기법인 가시광통신(Visible Light Communication, 이하 VLC)이 주목받기 시작하였다. VLC의 경우 전파를 사용하지 않아 주파수 할당이 필요가 없으며, 데이터전송에 ISM(Industrial Scientific Medical band)과 같은 간섭 또한 존재하지 않는다. 그렇기 때문에 VLC에 관한 연구 결과가 많이 나오고 있다. 본 논문에서는 기존의 LED 조명을 사용한 VLC와 수중환경에서의 VLC에 대한 survey를 진행하고 활용방법을 살펴보았다.

• 센서학회지
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• 제22권3호
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• pp.212-218
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• 2013

In this paper, we introduce a new method to reduce the inter-channel crosstalk in visible light communication (VLC) systems using the synchronizing pulses transmitted through the power lines. Synchronizing pulses are simultaneously transmitted to multiple VLC transmitters and receivers through the 220V power line. Each VLC transmitter modulates an LED and each VLC receiver demodulates the signal light in the time slot that is allocated with reference to the synchronizing pulses. This method is very simple and effective to prevent the inter-channel crosstalk in VLC systems for sensor networks because every VLC system can easily get the synchronizing pulses from the nearby power line.