• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.623-629
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• 2018

Smart Factory is a concept of automatic production system of machines by the fusion of ICT and manufacturing. As a base technology for realizing such a smart factory, there is an increasing interest in a low-power environmentally friendly LED lighting system, and researches on so-called optical ID related application technologies such as communication using a LED and position recognition are actively underway. In this paper, We have proposed a system that can reliably identify logistics location and additional information without being affected by electromagnetic interference such as high voltage, high current, and generator in the plant. Through the basic experiment, we confirmed the applicability of the color ID recognition rate from 98.8% to 93.8% according to the eight color variations in the short distance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.6296-6302
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• 2014

A new technique, which can increase the channel bandwidth in an optical wireless orthogonal frequency division multiplexing (OFDM) link based on a light emitting diode (LED), is proposed. The technique uses adaptive sampling to convert an OFDM signal to a sparse waveform. In compressive sensing (CS), a sparse signal that is sampled below the Nyquist/Shannon limit can be reconstructed successively with sufficient measurements. The data rate of the proposed CS-based visible light communication (VLC)-OFDM link increases from 30.72 Mb/s to 51.2 Mb/s showing an error vector magnitude (EVM) of 31 % at the quadrature phase shift keying (QPSK) symbol.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.8-14
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• 2020

Recently, there was an increasing demand for an integrated access control system which is capable of user recognition, door control, and facility operations control for smart buildings automation. The market available door lock access control solutions need to be improved from the current level security of door locks operations where security is compromised when a password or digital keys are exposed to the strangers. At present, the access control system solution providers focusing on developing an automatic access control system using (RF) based technologies like bluetooth, WiFi, etc. All the existing automatic door access control technologies required an additional hardware interface and always vulnerable security threads. This paper proposes the user identification and authentication solution for automatic door lock control operations using camera based visible light communication (VLC) technology. This proposed approach use the cameras installed in building facility, user smart devices and IoT open source controller based LED light sensors installed in buildings infrastructure. The building facility installed IoT LED light sensors transmit the authorized user and facility information color grid code and the smart device camera decode the user informations and verify with stored user information then indicate the authentication status to the user and send authentication acknowledgement to facility door lock integrated camera to control the door lock operations. The camera based VLC receiver uses the artificial intelligence (AI) methods to decode VLC data to improve the VLC performance. This paper implements the testbed model using IoT open-source based LED light sensor with CCTV camera and user smartphone devices. The experiment results are verified with custom made convolutional neural network (CNN) based AI techniques for VLC deciding method on smart devices and PC based CCTV monitoring solutions. The archived experiment results confirm that proposed door access control solution is effective and robust for automatic door access control.

• Current Optics and Photonics
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• v.1 no.4
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• pp.289-294
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• 2017

A high-performance time-division multiplexing (TDM) -based multiuser (MU) multiple-input multipleoutput (MIMO) system for efficient indoor visible-light communication (VLC) is presented. In this work, a MIMO technique based on RGB light-emitting diodes (LEDs) with selection combining (SC) is utilized for data transmission. That is, the proposed scheme employs RGB LEDs for parallel transmission of user data and transmits MU data in predefined slots of a time frame with a simple and efficient design, to schedule the transmission times for multiple users. Simulation results demonstrate that the proposed scheme offers an approximately 6 dB gain in signal-to-noise ratio (SNR) at a bit error rate (BER) of $3{\times}10^{-5}$, as compared to conventional MU single-input single-output (SISO) systems. Moreover, a data rate of 66.7 Mbps/user at a BER of $10^{-3}$ is achieved for 10 users in indoor VLC environments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.9
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• pp.1237-1242
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• 2018

Photodynamic therapy has been suggested as an alternative treatment to current cancer therapy which resulting in a variety of side effects because photodynamic therapy targets specific cancer cells and does not have a significant effect on normal cells. Typically, laser was used as a photodynamic therapy, but this was limited due to high cost and heat reaction. However, compact light emitting diodes that can emit light of various wavelengths have been developed at a low cost, which has a great influence on the low cost development of photodynamic therapy equipment. On the other hand, in the study of photodynamic therapy, the data on the direct effect of visible light are relatively small. Therefore, in this paper, we propose a novel cancer therapeutic module by developing a cancer cell proliferation inhibition module based on an Arduino that is relatively inexpensive, and able to use light of various wavelengths.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1136-1151
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• 2018

This paper proposes a new hybrid scheme to decrease the high peak to average power ratio (PAPR) of optical orthogonal frequency division multiplexing (OFDM) signals in visible light communication (VLC) systems. The PAPR causes nonlinear signal distortions and high power requirements for the VLC transmitter (light emitting diode, LED). The proposed method is applicable for both direct current-biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM). In the proposed scheme, the PTS method is firstly modified to fit both optical OFDM approaches transmission and then combined with signal clipping method for further PAPR reduction and bit error rate (BER) improvement of the VLC system. The performance of hybrid scheme has been evaluated and compared with the original OFDM based VLC system, conventional PTS and clipping methods. The results show that the hybrid scheme outperforms other methods in terms of both the PAPR reduction and BER performance.

• International journal of advanced smart convergence
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• v.7 no.4
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• pp.50-56
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• 2018

The Internet of Things (IoT) and Visible Light Communication (VLC) is opening up new services in lighting industry by integrating sensory network features in addition to standard illumination functionality. In this progressive developments, the next generation lighting devices for smart homes are capable to sense the environmental conditions and transfer the captured data through lights to gateway controller to access remotely. The smart home environmental sensor information's are few kbps only so VLC systems need to built-in with low rate light connectivity to transfer data to the gateway. To provide error free communication, the quality of a received light signal is important to be considered when designing an VLC receiver. Therefore, this paper proposes the design of robust low rate IoL receiver design using NCP302 voltage detector for micro controller to adapt the IoT/IoL front end module for system integration. To evaluate the proposed system performance, the Arduino UNO based IoT/IoL controller designed with lighting, sensors and lights connectivity interfaces. The experimental result shows that the robust interference rejection is feasible on proposed VOL receiver and possible to have an error-free communication up to 10 kbps at a low SNR using OOK modulation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2207-2210
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• 2005

Guest guidance system based on the compact battery-less information terminal, Aimulet, which has been developed by the authors of the National Institute of Advanced Industrial Science and Technology (AIST), Japan. Conventional Aimulet, which is Aimulet ver.1 or CoBIT, has features of location and direction sensitive information service device without batteries. On the other hand, the Aimulet has two subjects, one is multiplex and demultiplex of some contents, and the other is operation under sunshine. Former subject is of solved by the wavelength multiplex technique using LED emitter with different wavelength and dielectric optical filters. Latter subject is solved by new micro spherical solar cells with a visible-light-eliminating optical filter and a new design of light irradiation. These techniques are applied to the EXPO 2005, Aichi Japan and introduced in public. Aimulet GH is Former technique is applied on Aimulet GH, which is used in Orange Hall of the Global House, scientific museum with a fossil of a frozen mammoth.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.2
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• pp.41-54
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• 2000

Photochemical modulation of Bragg-reflection wavelengths based on isomerization of an azobenzene (Azo) and subsequent change in reflectance was investigated in cholesteric liquid crystals (ChLCs) which reflect light in visible wavelength region. Irradiation at 366 nm, which causes an efficient transcis isomerization of Azo, led to change in reflected color of ChLCs toward shorter wavelengths with a concomitant lowering of phase transition. Reversible change in color was induced all-optically by alternate irradiation at effective wavelengths for reversible isomerization of Azo. A considerable variation in reflectance was also observed when the photoinduced change in color was measured by a probe light with the same handedness as the ChLCs. The spectral Position of selective light reflection in the initial states played an important role to produce a normal-mode and a reverse-mode switching in photoinduced modulation of reflectance of the ChLCs with respect to the probe light.