• 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.

• ETRI Journal
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• v.37 no.4
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• pp.677-684
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• 2015

Recently, orthogonal frequency-division multiplexing (OFDM) was applied to VLC systems owing to its high rate capability. On the other hand, a real-valued unipolar OFDM signal for VLC significantly reduces bandwidth efficiency. For practical implementation, channel estimation is required for data demodulation, which causes a further decrease in spectral efficiency. In addition, the large fluctuation of an OFDM signal results in poor illumination quality, such as chromaticity changes. This paper proposes a spectrally efficient method based on a hidden-pilot-aided precoding technology for VLC with less flickering than a conventional OFDM-based method. This approach can obtain channel information without any loss of bandwidth efficiency while ensuring illumination quality by reducing the flickering effect of an OFDM-based VLC. The simulation results show that the proposed method provides a 6.4% gain in bandwidth efficiency with a 4% reduction in flicker compared to a conventional OFDM-based method.

• 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.