• Journal of Sensor Science and Technology
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• v.24 no.5
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• pp.342-347
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• 2015

We introduce an indoor broadcasting system using light-emitting diode (LED) lamps coupled with a 220 V power line. Two couplers connected to the power line constitute a power line communication (PLC) link. The transmission path from an LED lamp to a photodetector forms a visible light communication (VLC) link in free space. When the LED lamp is coupled to the power line, a composite PLC-VLC link is formed, making it possible to transmit a VLC signal beyond line-of-sight. In experiments, a 4 kHz analog signal modulated with a 100 kHz carrier was sent to the power line by a PLC coupler, and LED lamps coupled to the power line detected the signal and radiated it to multiple VLC receivers in the room. This configuration is useful in expanding an indoor VLC sensor network to adjacent rooms or constructing a voice broadcasting system in a building or apartments with existing power lines.

• 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.

• Journal of Environmental Health Sciences
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• v.30 no.2
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• pp.92-97
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• 2004

Three methods for VOCs emissions control in indoor air are reduction at the source, ventilation between indoor and outdoor, and removal. The best alternative should be to replace highly emitting sources with sources having low emissions, but the pertinent information on VOCs is not always available from manufactures. Other ways of improving indoor air quality are needed. It is to increase the outside fresh-air flow to dilute the pollutants, but this method would generally provide only a dilution effect without destruction in residence. An ideal alternative to existing technologies would be a chemical oxidation process able to treat large volumes of slightly contaminated air at normal temperature without additional oxidant such as ozone generator and ion generator. Photocatalytic oxidation(PCO) represents such a process. It is characterized by a surface reaction assisted by light radiation inducing the formation of superoxide, hydroperoxide anions, or hydroxyl radicals, which are powerful oxidants. In comparison with other VOCs removal methods, PCO offers several advantages. The purpose of this study was to explore the possibilities for photocatalytic purification of slightly contaminated indoor air by using visible light such as flurescent visible light(FVL). In this study, a PCO of relatively concentrated benzene using common FVL lamps was investigated as batch type and total volatile organic compounds(TVOCs) using a common FVL lamp and penetrated sun light over window. The results of this study shown the possibility of TiO$_2$ photocatalyst application in the area of indoor air quality control.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1363-1370
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• 2018

In visible light (VL) positioning based on angle of arrival (AOA) estimation for smart indoor service, the AOA parameters obtained at the receiver has sometimes a random and distributed angle form instead of a point angle form due to the multipath transfer of the actual visible light and short positioning distance. The AOA estimation of a VL signal with a random and parametric distributed angle form may give incorrect AOA parameter estimates, which may result in poor VL positioning performance. In this paper, we classify the AOA parameters of the received VL signal into three forms according to the actual positioning channel environment and consider the short-range VL positioning method. We propose a subspace-based AOA parameter estimation technique and a data fusion method, and analyzed the proposed method by simulation and the measurement of the real VL channel characteristics.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.852-857
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• 2010

In this paper, we proposed and demonstrated an indoor visible-light communication system using an array of light-emitting diodes (LEDs). The main idea is based on that the LEDs can be used not only for lighting but also for free-space optical communications. Because LEDs offer advantageous properties such as high brightness, reliability, lower power consumption and long lifetime, the indoor visible-light communication systems are going to provide high quality of service by the high radiation power of the LED lighting. Prototype of simplex channel for audio and the full-duplex channel for text message were developed. Results indicates the viability of creating inexpensive free-space optical communication transceivers that might be embedded in commercial light products to supports indoor wireless networking.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.5
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• pp.61-69
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• 2018

The goal of this study is to compare the evaluation results of indoor daylight environment for each certification and propose improvement points. As the importance of indoor daylight environment has increased, foreign countries have been aware of this and have changed the light environmental certification items. On the other hand, Korea environmental certification systems have not been able to follow the current situation. In order to improve this, this study intended to find evaluation criteria for each category by comparing and analyzing indoor daylight environment certification items in Korea's G-SEED, LEED in the United States, BREEAM in the UK, and CASBEE in Japan. After that, this study simulated 3D models of three spaces about classroom, reading room and club room of Yanghyun elementary School which is scheduled to be constructed for the evaluation of indoor daylight environment, and the results were analyzed to suggest for improvement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.8
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• pp.672-678
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• 2013

In the recent year, along with the rapid development of LED technology, many applications using LEDs have been researched and indoor positioning is one of them. In particular, previous indoor positioning systems based on visible light communication combine triangulation manner such as AoA, ToA TDoA. But most of them needs transmitting unique ID of each LED panel. In this paper, we propose an non LED-ID based indoor positioning system in which the visible light radiated from LEDs is used to locate the position of receiver. Compared to current indoor positioning systems using LED light, our system has the advantages of simple implementation, low cost and high accuracy. Through the computer simulation, our system can achieve a high estimation accuracy of 3.6cm in average in the $5{\times}5{\times}3m^3$ room.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.1
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• pp.16-23
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• 2019

Fine particulate matter known as PM 2.5 refers to the atmospheric particulate matter that has a diameter less than 2.5 micrometer identified as dangerous element for human health and its concentration can provide us a clear picture about air dust concentration. Humans stay indoor almost 90% of their life time and also there is no official indoor dust concentration data, so our study is focused on measuring the indoor air quality. Indoor dust data monitoring is very important in hospital environments beside that other places can also be considered for monitoring like classrooms, cements factories, computer server rooms, petrochemical storage etc. In this paper, visible light communication system is proposed by Manchester encoding technique for electromagnetic interference (EMI)-free indoor dust monitoring. Important indoor environment information like dust concentration is transferred by visible light channel in wide range. An average voltage-tracking technique is utilized for robust light detection to eliminate ambient light and low-frequency noise. The incoming light is recognized by a photo diode and are simultaneously processed by a receiver micro-controller. We can monitor indoor air quality in real-time and can take necessary action according to the result.

• Journal of the Optical Society of Korea
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• v.19 no.4
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• pp.351-356
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• 2015

Visible light communication (VLC) is considered to be an attractive scheme to realize the broadband wireless communication for an indoor environment. We present a room division multiplexing (RDM) mechanism for an indoor multi-room VLC network, which utilizes the spatial position of the LED lamp in different rooms as a novel dimension of network resource for multiplexing, and thus the network capacity is increased. In such a network, the service interruption caused by user cross-room movement is an important problem, and we propose a double-area-positioning based cross-room switch solution. An experimental platform demonstrates the RDM-deployed VLC network, and validates the performance of the presented switch mechanism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.9
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• pp.775-780
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• 2013

Localization, or positioning, is gaining the increasing attention of researchers around the world. The location information, especially the indoor location, is important for navigation systems, heating and air conditioning systems, illumination adjustment, humidity control, robot service, and so on. In this paper, we propose a three-dimensional indoor localization technique using visible light. The main goal of our proposed scheme is to improve the accuracy of VLC-based indoor localization by utilizing multiple VLC transmitters. The simulation results validate the performance of our proposed scheme.