• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1998.10a
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• pp.996-998
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• 1998

• Journal of Convergence for Information Technology
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• v.8 no.5
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• pp.153-158
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• 2018

In this paper, we have studied a dimming level control method to satisfy both lighting and communication performance in visible light communication system. In the case of the most commonly used OOK and RZ-OOK modulation schemes, continuous Burst Zero Duration will seriously degrade the lighting function. This causes not only the illumination but also the performance of the entire system to deteriorate. Through this study, we analyzed the dimming level characteristics of the existing system and proposed the Illegal Pulse Insertion (IPI) algorithm as a technique to increase the dimming level. Through this, it is possible to effectively control the dimming level and improve the QoS of both lighting and communication by resolving the flicker phenomenon and dimming level reduction in the existing modulation and demodulation system.

• 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.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.11-17
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• 2012

The VLC system undertakes both missions of illumination and wireless communication. It is difficult to design a VLC system with optimal performance due to the trade-offs between power consumption and channel quality. In this paper, the VLC system design problem is solved by using multi-objective optimization method. For optimization, the multi-objective function is formulated with respect to power consumption, received power, and SNR under the constraints on the system variables. Through the multi-objective optimization, it is possible to obtain the solutions that satisfies both minimum power consumption and maximum channel quality.

• Electronics and Telecommunications Trends
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• v.25 no.2
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• pp.57-67
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• 2010

최근에 3.5G, 4G 이동통신, WiMax 등 다양한 고속 무선 데이터 서비스의 발달이 급속도로 진행됨에 따라 기지국을 위한 무선 백홀의 전송속도가 현재 보다 급격히 높아질것으로 예상되며, 광 백본망에 연결되지 않은 빌딩들을 위한 광통신망과 빌딩간 'Last Mile' 구간에 대한 경제적인 통신망 확보가 요구되고 있다. 본 고에서는 경제적으로 Gbps급 광 백본망과 가입자를 연결하거나, Gbps급 사설통신망 및 백홀에 이용할 수 있는 E-band 이용 Multi-Gbps급 고정 점대점 통신 시스템과 송수신기 핵심 구성 부품의 기술 개발 동향을 소개하고자 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.113-116
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• 2010

최근 차량 내부의 전자 제어장치에 대한 운전자의 편의성 및 안전성의 요구 수준이 높아지고 있으며 이러한 수요자의 요구를 만족시키기 위하여 자동차 업계에서도 첨단식 편의기능을 갖춘 자동차의 개발에 많은 초점을 모으고 있는 추세이다. 이에 대응해 차량 내부의 전자시스템 사이에 상호 통신을 위한 차량용 네트워크 기술도 빠르게 발전하고 있다. 특히 대용량 데이터를 고속으로 전송할 수 있도록 높은 대역폭을 제공하는 차량용 광 네트워크가 주목 받고 있으며 현재 일부 차량에 도입되어 양산되고 있는 추세이다. 이러한 기술적 변화에 맞춰서 본 연구에서는 차량용 광 통신 네트워크 표준인 "MOST"의 백본망을 구축하여 무선 이동 단말기 보드(MV Board)를 통해 MOST 광 네트워크에 연결되어 있는 여러 장치들에 대한 다양한 정보를 수신할 수 있고 MOST네트워크 동작 및 운영상태를 확인해 볼 수 있는 시스템을 구성하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1045-1052
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• 2011

Recently, because of complex cultural space, underground space are becoming larger. Therefore, the demand for location-based services is growing. VLC (Visible Light Communication) is based on the LED lighting infrastructure so that suitable LBS (Location-based service) is possible for the targeted places in indoor space. To experiment with indoor LBS by VLC, we measure the identification distance according to variable angles between LED and photo diode. We send the different ASCII code for each LED light, then we found the maximum identification distance is 1.75m from LED lights. From the results of this experiment, we show that indoor navigation is possible.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.396-400
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• 2006

We present a weather-insensitive optical free-space communication method supporting optical packet channels. It operates optical fiber amplifiers in gain-saturation regions. When the propagation loss gets too high, it decreases the average packet rate, or the average packet length, or both, to increase the optical power level launched into the free-space. As a demonstration, we transmit $8{\times}10$ Gigabit Ethernet channels over a terrestrial distance of 2.4 km. One gain-saturated free-space optical repeater is used at the halfway point.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.12
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• pp.1219-1224
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• 2016

The current wireless power charge technologies are based on induction coupling, magnetic resonant coupling, electromagnetic wave, etc. However, the current wireless power charge technologies has several disadvantages including short transfer range, electromagnetic interference, etc. In this paper, we investigate and demonstrate a laser wireless power charge technology. A laser source is used in the transmitter to convert from electric power to optical power and a solar cell or a photodiode is used in the receiver to convert from optical power to electric power. The laser wireless power charge technology may be the most efficient wireless power charge technology in the long distance over than 10 meters. Our experimental results show a transfer efficiency of 2.15% at the 70-m long distance with a 100 mW laser transmitter and a photodiode receiver.

• Electronics and Telecommunications Trends
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• v.33 no.6
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• pp.94-106
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• 2018

A quantum key distribution (QKD) provides in principle an unconditional secure communication unlike the standard public key cryptography depending on the computational complexity. In particular, free-space QKD can give a secure solution even without a fiber-based infrastructure. In this paper, we investigate an overview of recent research trends in the free-space QKD system, including satellite and handheld moving platforms. In addition, we show the key components for a free-space QKD system such as the integrated components, single photon detectors, and quantum random number generator. We discuss the technical challenges and progress toward a future free- space QKD system and components.