• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.71-78
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• 2017

Visible light communication (VLC) offers communication function in addition to illumination. Because the signal communication capacity per cable is 1,000 times compared to the power line communication (PLC), optical fiber is being advertised as the basis of the information and communication. Also dimming control of LED is an important component needed to provide energy savings and quality of life. This study configured multi-hop VLC system model in a building using optical fiber and analyzed the power performance of two of modulations using dimming techniques. The transmission power and received power were used to compare the power performance in multi-hop VLC environments.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.203-209
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• 2012

Visible light communications (VLC) use modern solid-state light-emitting diodes (LEDs) to broadcast information. Emerging white-light LEDs allow the combination of lighting and optical wireless communication in one optical source. In this paper, a new LED lighting design using one-chip-type white LEDs is proposed for efficient illumination and optical wireless communications under the existence of several obstacles. Lighting and communication performance are analyzed to show the effectiveness of the proposed LED lighting. Specifically, the signal-to-noise ratio considering intersymbol interference and the bit-error rate of variable pulse position modulation (VPPM) with dimming control are considered.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.127-134
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• 2015

VLC(Visible Light Communication) is the technology to send and receive data by using visible light that LED emits. The basic principle of VLC is the communication by using flashing(ON/OFF) of the light from the LED that changes electricity to light in short time. As the recent advances in LED technology, VLC is also received a lot of attention and the research about it is in progress actively. Especially, the interest about indoor VLC system is increasing because the visible light can't pass through the wall. In this paper, we compose the indoor SISO VLC system with NRZ-OOK and VPPM modulation schemes. Also, we apply SR-ARQ, a kind of re-transmission error control schemes, to the VLC system. And then, we compare and analyze the performance of communication according to the location of receiver and the type of modulation by using BER, the number of transmission and throughput.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.63-69
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• 2014

Visible light communication is a communication method using an LED's blinking(ON/OFF), it has a feature of light because of the limit of perception by the human's optic nerve. LED' dimming control used in the VLC system is important factor needed to provide energy saving and life benefits. With advances in VLC system, MIMO technology has received much attention in that it can be obtain channel capacity proportionate to the number of antenna. Therefore, in this paper, with RC method which is one of the MIMO style in VLC system, it is compared communication performance using RZ-OOK, VPPM, MPPM and OPPM. As a result of the simulation was run against this, MPPM works well in terms of Power requirement and OPPM works well in terms of Spectral efficiency and Bandwidth requirement, also it was confirmed that there is a significant impact on the communication performance of each modulation scheme according to the dimming.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.277-283
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• 1995

For the development of low NO$_{x}$ gas burners aimed for absorption chiller/heater unit, three proto type burners of different capacity (265000, 498000, and 664000 kcal/h) have been manufactured through a combustion method of step-by-step air injection. In order to characterize the overall features of the flame and the properties of the emission gas, the temperature of the flame and the concentration of NO$_{x}$ and CO were determined. The main factors in the design of burners (the area of primary air injection, the diameter of secondary air injection hole, fuel nozzle diameter) were observed to increase linearly with the scale-up of burner capacity. The flame temperature profiles of the burners were observed to be almost similar, irrespective of their capacity. However, as their capacity increased, the flame temperature slightly increased and the hot region of the flames moved to ward the flame tip along with the expansion to the direction of radius. From the proto type units, the amount of their NO$_{x}$ emission was determined to be around 25 - 30 vppm(3% )$_{2}$) and the CO emission was less than 19 vppm (3% $O_{2}$).TEX>).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1276-1291
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• 2014

In the field of visible light communication (VLC), light-emitting diodes (LEDs) are used for transmitting data via visible light. In this study, we analyze pulse dual slope modulation (PDSM) as a means of delivering information in VLC. PDSM involves the modulation of symmetrical slope pulses to encode binary 0s and 1s, and owing to the moderately increasing and decreasing pulse shapes that are created, this method enables more spectral efficiency than the variable pulse position modulation (VPPM) technique currently adopted in IEEE 802.15.7. In particular, PDSM allows for the avoidance of intra-frame flicker by providing idle pulses in a spectrum-efficient way. A simple detection scheme is proposed for PDSMsignals, and its bit error rate (BER) is analyzed mathematically at varying slopes to validate the process through simulation. The BER performance of PDSM detection using dual sampling is compared to the performances of PDSM and VPPM using correlation detection. It is found that, when the probability of idle pulse transmission is less than 0.08 and higher than 0, the BER of dual sampling PDSM is lower than that of PDSM using correlation detection over the entire light intensity range.

• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.116-120
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• 2014

Visible Light Communication is one of the promising technologies for wireless communication due to the possibility to use existing LED lightening infrastructure to transmit data. LED has the ability to turn on and off very fast enough that our human eyes can't recognize so it can be used to transmit data via visible light along with illumination. But it faces flicker problem due to the brightness discrepancies between '1' and '0' bit patterns inside a data frame. Various run length limited (RLL) coding scheme like Manchester code, 4B6B, 8B10B or VPPM can be used to solve flickering problem. So we propose pseudo Manchester codding which can transmit data without modifying LED modulator and demodulator circuit as well as solve flickering problem.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.2
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• pp.75-82
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• 2016

Visible light communication (VLC) using LED lamps is suitable for implementing an indoor positioning system in an indoor environment where the global positioning system (GPS) signal does not reach. In this paper, we present an indoor positioning system for mobile robots using a VLC beacon and fuzzy rules. This system consists of an autonomous mobile robot, VLC modules, and device application software. Fuzzy rules are applied to plan the global and local paths along which the mobile robot navigates indoors. The VLC transmitter modules are attached to the wall or the ceiling as beacons to transmit their own location information. The variable pulse position modulation (VPPM) algorithm is used to transmit data, which is a new modulation scheme for VLC providing a dimming control mechanism for flicker-free optical communication. The mobile robot has a receiver module to receive the location information while performing its mission in the environment where VLC transmitters are deployed.

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.6-12
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• 2018

In this paper, a 32-variable pulse position modulation (32-VPPM) scheme is proposed to support a red-green-blue light-emitting-diode (RGB-LED)-based optical camera communication (OCC) system. Our proposed modulation scheme is designed to enhance the OCC data transmission rate, which is targeted for the wearable biomedical data monitoring system. The OCC technology has been utilized as an alternative solution to the radio frequency (RF) wireless system for long-term self-healthcare monitoring. Different biomedical signals, such as electrocardiograms, photoplethysmograms, and respiration signals are being monitored and transmitted wirelessly from the wearable biomedical device to the smartphone receiver. A common 30 frames per second (fps) smartphone camera with a CMOS image sensor is used to record a transmitted optical signal. Moreover, the overall proposed system architecture, modulation scheme, and data demodulation are discussed in this paper. The experimental result shows that the proposed system is able to achieve > 9 kbps using only a common smartphone camera receiver.