• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.107-111
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• 2009

The properties of the chirped fiber Bragg grating (CFBG) as a chromatic dispersion compensator in differential phase-shift-keyed (DPSK) transmission are analyzed. Comparisons of a performance of a CFBG in between DPSK and On-Off Key (OOK) are shown by simulations using the commercial numerical modeling software, $OptSim^{TM}$. In the simulation, we compared the performance of the CFBG when they were used in the RZ-OOK 40 Gbps and the RZ-DPSK 40 Gbps transmission. The simulation results show the performance of an overall transmission with a CFBG in DPSK is inferior to the case of OOK, although DPSK generally has a 3 dB higher SNR (signal-to-noise ratio) than OOK.

• 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.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.114-120
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• 2009

In outdoor visible light communication channels and LED road illumination communications for the intelligent transport systems (ITS), inter symbol interference (ISI) due to multipath propagation prevents high data rate transmission. Indoor wireless optical communication systems utilizing white LED lights and on the road illumination have been studying about it. Generally, plural lights are installed in room and considered to the traffic information system using existing LED traffic lights. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses on-off keying, return-to-zero (OOK-RZ) coding and the other uses optical orthogonal frequency division multiplexing(OFDM).

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.7-11
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• 2008

Future electric lights will be composed of white LEDs (Light Emitting Diodes). Indoor wireless optical communication systems utilizing white LED lights have been studying about it. Generally, plural lights are installed in room. Therefore, their optical path difference must be considered. In this paper, the influence of an optical path difference has been investigated and two approaches against this problem are introduced. One uses OOK-RZ (On-Off Keying, Return-to-Zero) coding and the other uses optical OFDM (Orthogonal Frequency Division Multiplexing). From the results of computer simulations, we have found that these approaches are feasible for the wireless optical communication systems utilizing white LED lights.

• 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.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.169-180
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• 2018

White light-emitting diodes (LEDs) are more economical than fluorescent lights, and provide high brightness, a high lifetime expectancy, and greater durability. As LEDs are closely connected with people's daily lives, dimming control of LED is an important component in providing energy savings and improving quality of life. In visible light communications systems using these LEDs, multiple input multiple output (MIMO) technology has attracted a lot of attention, in that it can attain the channel capacity in proportion to the number of antennas. This paper analyzes the power performance of three kinds of modulation in visible light communications (VLC) systems applied space-time block code (STBC) techniques. The modulation schemes are return-to-zero on-off keying (RZ-OOK), variable pulse position modulation (VPPM), and overlapping pulse position modulation (OPPM), and dimming control was applied. The power requirements and power consumption were used as metrics to compare the power efficiency in $2{\times}2$ STBC-VLC environments under the three kinds of modulation. We confirm that dimming control affects the communications performance of each modulation scheme. VPPM showed greater consumption among the three modulations, and OPPM showed energy savings comparable to VPPM.