• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.83-90
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• 2009

White LEDs(Light Emitting Diode) offer advantageous properties such as high brightness, improved reliability, lower power consumption, and long lifetimes. An LED is an electronic device that converts an electrical signal into a tight signal and is used not only in Optical Communication Indoor wireless optical illuminating rooms, but also for wireless optical communication systems. Currently, studies about these white LEDs have been being progressed, and in this raper, we discuss the multiplex and the multiple access method of VLC(Visible Light Communication) systems using white LEDs. In proposed system, CDMA(Code Division Multiple Access) apples to VLC system to reduce interference of VLC system, and improve capacity. The superiority of OOK modulation is presented in analysis of results by comparing VLC-CDMA communication system using OOK(On-off keying) modulation and BPSK modulation in AWGN(Additive White Gaussian Noise) channel and Diffuse channel. And we investigate the significance of a solution of interference by multipath by comparing BER in multipath channel and AWGN channel. In the proposed system, we assume Directed LOS(Line Of Sight) and Diffuse Link, and suppose VLC-CDMA using OOC(Optical Orthogonal Code) as methods to increase efficiency of system by removing ISI(Inter Symbol Interference) caused by multiple access, optical spreading code, and also present an analysis of its performance.

• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.656-659
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• 2017

In this paper, we propose a digital method for transmitting audio signals using LED visible light communication system. In the proposed method, we compare the method for transmitting audio signal in analog signal and the method for transmitting by digital signal. When amplifying the audio sound and transmitting the analog signal using the LED visible light communication, attenuation corresponding to the transmission distance occurs, and there is a disadvantage that it is noisy. In order to overcome this, we propose a method for transmitting digital audio signals. The proposed method has the advantage of reducing the influence of noise, but it turned out that it is affected much by the LED blinking speed. Various methods to overcome this need to be continuously studied.

• Electronics and Telecommunications Trends
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• v.23 no.5
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• pp.32-39
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• 2008

반도체 LED가 조명 인프라를 바꾸는 신성장 기술로 급부상하고 있다. LED는 백열전등에 비하여 전기 절감 효과가 높고, 형광등에 비하여 수은을 사용하지 않아 친환경적이다. 통신 및 조명 환경 변화에 부응한 기술로서, LED 조명과 동시에 통신을 할 수 있는 가시광 무선통신 융합 기술이 등장하였다. 본 고에서는 조명과 통신의 전혀 다른 산업이 융합된 기술로 탄생하게 된 기술적 배경, 가시광 무선통신의 국내 및 국제 표준동향, LED 조명통신 융합 기술에 의한 융합 서비스를 설명한다. 가시광 무선통신 기술은 눈으로 확인하는 통신, 빛 색에 따른 선별통신, LOS 통신 보안을 보장해주는 것이 특징이다. 또한, 조명통신 융합에 의해 광 ID, 광센서, 초정밀 실내 측위, M2M 등의 신규 융합 서비스도 제공할 수 있다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.108-111
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• 2001

ZnO thin films on (001) sapphire substrates have been deposited by pulsed laser deposition(PLD) technique for light emitting device applications. We have controlled the emission intensity of UV and visible light, depending on film thickness and various post-annealing time. UV emission became strong as the thickness of ZnO thin films increased. The intensity of visible light was strong as post-annealing temperature increased. The optical properties of the ZnO thin films were characterized by PL(photoluminescence) and the structural properties of the ZnO were characterized by XRD for the application of ZnO light emission device.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.9
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.108-111
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• 2001

ZnO thin films on (001) sapphire substrates knave been deposited by pulsed laser deposition(PLD) technique for light emitting device applications. We have controlled the emission intensity of UV and visible light, depending on film thickness and various post-annealing time. UV emission became strong as the thickness of ZnO thin films increased. The intensity of visible light was strong as post-annealing temperature increased. The optical properties of the ZnO thin films were characterized by PL(photoluminescence) and the structural properties of the ZnO were characterized by XRD for the application of ZnO light emission device.

• Journal of Advanced Information Technology and Convergence
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• v.8 no.2
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• pp.147-157
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• 2018

In this study, we analyzed an outdoor visible light communication system and implemented it through a simulation. We designed a Reed-Solomon encoder, a variable interleaver structure, and set it to the Institute of Electrical and Electronics Engineers (IEEE) 802.15.7 PHY I specification mode. We also analyzed the performance of an additive white gaussian noise (AWGN) channel environment using a root-raised-cosine (RRC) filter, implemented a MATLAB simulation and analyzed its performance. The results showed a requirement for an additional signal-to-noise ratio (SNR) of approximately 1.5 dB in a 3-ray multipath visible light channel environment than in an AWGN environment.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.69-74
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• 2010

In this paper, we present an indoor positioning system based on light emitting diode (LED). Because LED is a semiconductor light emitting device, we can easily switch and modulate electrical signals into lightwave signals at high speed using LEDs. We assigned unique 8-bit ID address to each LED lights. Photo diode receives data from 16-LED lights and takes correlation coefficient beteween received data and each LED-ID. Using correlation coefficient, proposed positioning system shows resolution of 50 cm in dimensions of $4\;m\;{\times}\;4\;m\;{\times}\;2\;m$.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.69-72
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• 2014

Recently, lighting systems using audio signal of audible frequency and frequency spectrum of visible lighting are studied. And various related products are being sold and released commercially. Also demands of emotional matching algorithm and system which includes effective and methodical designs are being increased. And the importance related with this scheme has increased. In this Paper, we configures a system for digital sound source based LED color control. And we develop algorithm to control LED color for the system configuration. Also we demonstrated the usefulness of the algorithm through experiment with simulation using LED color control system. We expected to be useful in a variety of fields and applications using proposed digital music based LED color control system.