• Journal of Convergence for Information Technology
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• v.11 no.2
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• pp.25-30
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• 2021

In this paper, we studied the coding technique for flicker mitigation and BER performance improvement in visible light communication system. In order to increase the transmission speed of visible light communication, a multi-transmission multi-LED transmission system using a plurality of LEDs is being actively studied. However, when data is transmitted through N LEDs in a multi-LED visible light communication system using N LEDs, there is a continuous zero section in which 0 is transmitted simultaneously according to the data sequence, and since the transmission section of 1 is different, flickering Or, a phenomenon in which the dimming level changes occurs. The visible light communication system is a communication system that simultaneously performs communication and lighting functions. Therefore, transmission efficiency of communication and brightness of lighting must be considered at the same time. To solve this problem, we proposed a flicker reduction mapping that can alleviate flicker and dimming level problems, improve error detection and BER performance through coding mapping of each LED data sequence.

• Journal of Industrial Convergence
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• v.22 no.2
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• pp.55-62
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• 2024

Visible light communication, which transmits information using visible light, has advantages such as ultra-high speed, ultra-delay, and ultra-connectivity, so research is being conducted as a way to complement 6G communication. In this paper, a study was conducted to overcome the performance degradation caused by the RGB mixing ratio in visible light communication. In a visible light communication system using LED lighting, the role of lighting is an important function, and when used for communication, the performance difference according to the RGB mixing ratio inevitably occurs. In particular, if the intensity of light is below a certain standard, the problem of deteriorating the performance of the entire system occurs. In this study, when a certain performance or less occurs in the communication system caused by the difference in the mixing ratio among the three RGB channels, the remaining two signals except the LED with the best performance are transmitted to STBC (Space-Time Block Coding) to ensure the quality of communication. A computer simulation was performed to verify the performance of the proposed system, and it can be seen that the performance of the proposed system is improved compared to the existing system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.140-146
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• 2018

Recently, VLC(Visible Light Communication) fusing with LED(Light Emitting Diode) used in indoor lighting and wireless communication technology has attracted attention. However, the VLC can communicate only within the coverage to measure the optical signal and the communication disconnection phenomenon is occur in the NLoS(Non-Line-of-Sight) area. In this paper, we propose VLC relay module to extend the coverage of VLC and improve the communication disconnection phenomenon in NLoS area. The proposed VLC relay module transmits the packet received from the transmitter to the VLC relay module and receiver. The experiment was carried out by installing one VLC transmitter and three VLC relay modules, communication coverage expansion and the improvement of communication disconnection phenomenon in the NLoS were confirmed by the increase of the VLC relay module. Also, we confirmed that the optical signal measurement performance is improved 2.4 times by using the dual sampling method.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.32-36
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• 2016

In this paper, a transceiver of VLC (Visible Light Communication) using LED white lighting has been implemented. We analyzed differences between conventional wireless communication and VLC with high-speed data transmission in a variety of environments, and confirmed symbols which passed through a channel using QAM. In order to get a high data rate, we found some variables that should be considered essentially though experiments. In addition, we set a bandwidth and found an optimal gain according to the distance between transmitter and receiver. We analyzed proposed system model through Labview and finally showed a system performance and to efficient data transmission and detection for VLC, we apply the orthogonal sequences to VLC system.

• 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 Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.73-79
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• 2014

Visible light communication is a communication method using an LED having a high-speed ON / OFF rate data to be transmitted, it is used as a wireless high speed data transmission. VLC system evolves, the problem of basic research is intended to improve performance and ensure reliability of the communication. The nature of the visible light communication, communication is performed only in the reach of the light, which indicates a big difference by the emission angle of the light. Therefore, in this paper, in the case of indoor environments generally, with the attributes of the multiple LED is equipped, was applied to a MIMO (Multiple Input Multiple Output) communication system. and analyzed SNR performance and total power can be obtained on the reception side by changing the emission angle of the transmitter. As a result of the simulation was run against this, it was confirmed that there is a significant impact on the performance of BER and SNR performance by the emission angle of the transmitter.

• Review of Korean Society for Internet Information
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• v.10 no.1
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• pp.85-92
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• 2009

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.397-397
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• 2004

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.283-288
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• 2019

LPWA (Low Power Wide Area) networks have been considered as one of the technologies which can be implemented in IoT (Internet of Things) applications by providing less power and longer communication range compared with existing wireless technologies. In this paper, we investigate LoRa which is one of representative technologies for LPWA networks. First, we present general properties and several technologies of LPWA networks. Then, the technical specification, properties, and pros/cons of LoRa are studied. Finally, we discuss analysis of LoRa's performance and its ehancement technologies by focusing on physical layer and MAC (Medium Access Control) layer.

• Korean Journal of Optics and Photonics
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• v.29 no.2
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• pp.77-84
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• 2018

We analyze the link availability of terrestrial free-space optical (FSO) communication systems in Korea. For this purpose, we utilize several theoretical models to calculate the power losses induced by absorption and scattering in the atmospheric channel, using five-year meteorological data for three major cities in Korea (Seoul, Busan, and Daejeon). Also, we estimate the power variations at the receiver caused by scintillation in the data. Those power losses and variations are used to estimate the availability of FSO links in the three cities. The results show that link availability is estimated to be over 95% in Daejeon for a 3.5-km FSO link, when the transmitter power and receiver diameter are greater than 10 dBm and 7 cm respectively. Slightly worse link availabilities are obtained for Busan and Seoul.