• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.85-90
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• 2014

In this paper, we propose a novel UE(User Equipment) position tracking algorithm of visible light signals, and analyze BER performance when optical beamforming scheme is applied in VLC(Visible Light Communications) system. The optical beamforming scheme as an interference mitigation method provides good optical channel conditions between UE(Rx) and LED light(Tx), and lead to better BER performance because UE is able to get a better RSSI(Received Signal strength indication) value. For the system BER, the proposed UE position tracking method for optical beamforming transmission demonstrates the performance enhancement compared to a system not applied the optical beamforming transmission scheme, and up to about 5~6dB SNR performance gain is achieved. The results of the paper can be applied to design of various VLC and LBS applications for ubiquitous home network systems.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.247-256
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• 2013

According to the complete standard document for PHY/MAC layer of visible light communication through the IEEE 802.15.7 WG on Sept. 2011, visible light communication lays a good foundation for developing a variety of application services. Thus, visible light communication moves to the advanced research period for developing application services, but most of applications are limited only to PtP service model. However, PtMP communication environment for VLC is required to accommodate more various applications. In this paper, we analyze an effect of key parameters on network performance in the star topology based visible personal area network system. We implement a simulator with considering attributes of PHY and MAC layer which are defined by IEEE 802.15.7 standard documents, and analyze the VLC performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.480-483
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• 2018

In this paper, we study the interference canceling and image sensing processing technology of multiple light sources for high speed transmission in CMOS sensor based visible light communication system. To improve transmission capacity in optical camera communications via image sensors, different data must be transmitted simultaneously from each LED. However, multiple LED light source environments for high-speed transmission can cause interference between adjacent LEDs. In this case, since the visible light communication system generally uses intensity modulation, when a plurality of LEDs transmit data at the same time, it is difficult to accurately detect the respective LEDs due to the light scattering interference of the adjacent LEDs. In order to solve this problem, the ON / OFF state of many LEDs of the light source is accurately recognized by using a dual CMOS sensor, and the spectral estimation technique and the pixel image signal processing technique of each LED are proposed. This technique can accurately recognize multiple LED pixels and improve the total average bit error rate and throughput of a MISO-VLC system.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.32-36
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• 2016

In this paper, a transceiver of VLC (Visible Light Communication) using LED white lighting has been implemented. We analyzed differences between conventional wireless communication and VLC with high-speed data transmission in a variety of environments, and confirmed symbols which passed through a channel using QAM. In order to get a high data rate, we found some variables that should be considered essentially though experiments. In addition, we set a bandwidth and found an optimal gain according to the distance between transmitter and receiver. We analyzed proposed system model through Labview and finally showed a system performance and to efficient data transmission and detection for VLC, we apply the orthogonal sequences to VLC system.

• 한국디지털정책학회:학술대회논문집
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• 2004.05a
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• pp.609-616
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• 2004

본 논문에서는 주파수 자원의 고갈로 인하여 차세대 정보통신 시스템으로 사용의 가능성이 예상되는 가시광통신의 개요와 응용기술 및 발전동향에 대하여 알아 보고자한다.

• Review of Korean Society for Internet Information
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• v.10 no.1
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• pp.85-92
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• 2009

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.473-477
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• 2015

In this paper, a commercial phosphorescent white light-emitting diode (WLED) visible light communication (VLC) system with an equalization circuit to achieve the high modulation bandwidth was designed and demonstrated. An analytical method to examine the performance of the equalizer was carried out using a general circuit-simulator, PSpice. The equalization circuit was composed of two passive filters with resisters and a capacitor and an active filter with an op-amp. Utilizing our post-equalization technology, the ~3.5 MHz bandwidth of phosphor WLED could be extended to ~25 MHz without using an optical blue-filter. In this VLC system with a single round-type WLED and a single PIN photo-diode, ASK data transmission up to 35 Mbps at a 1m free space distance was obtained. The resulting bit-error-rate was $7.6{\times}10^{-4}$, which is less than the forward error correction (FEC) limit of $3.8{\times}10^{-3}$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.99-105
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• 2018

This paper proposes multiple access method for smart doorlock system using VLC(Visible Light Communication) with color grid modulation method. The proposed method is to connect multiple visible light signals using color grid modulation method in order to recognize and authenticate multiple users accessing doorlock. In order to enable visible light multiple access with existing infrastructure, the symbol energy interval of signal should be maximized. Thus, performance of system in VLC channel is measured by modulating symbols based on the proposed method. We confirm the actual channel test results of the modulated signal to implement doorlock system that recognizes the number of multiple access users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.755-762
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• 2014

In recent year, along with the rapid development of LED technology, many applications using LEDs with Visible Light Communication(VLC) have been researched. Since it is easy to provide LOS communication environment along with cheap deployment cost, the indoor positioning system based on VLC has been actively studied. In this paper, we propose an accurate indoor positioning algorithm using a stereo image sensor and white-light LEDs with the visible light communication. Indoor white-light LEDs are located at the ceiling of a room and broadcast their position information by VLC technology. Mobile receiver with stereo image sensor receives LED position information by VLC and estimates its position and angle information. Simulation results are given to show the efficiency of proposed indoor positioning algorithm.