Abstract
In this demonstration, we propose and experimentally investigate the quaternary-amplitude-shift-keying (4-ASK) modulation with digital filtering to enhance the direct modulation speed of white-light light-emitting-diode (LED) in visible light communication (VLC) system. Here, an ordinary LED commercially available for lighting application with a direct modulation speed of 1 MHz is used. Data rate of 20 Mbit/s can be achieved in a 1 m free space transmission without using optical blue filter. In the previous studies, the transmission rate of LED VLC could only be increased by 2 to 10 times of the direct modulation speed of the white-light LED if using electrical equalization only. Moreover, the adaptive-controlled FIR filter makes the system closer to the matched filtering condition for reducing the inter-symbol-interference (ISI) for the LED VLC. A recorded 20 times enhancement of the direct modulation speed of white-light LED VLC system is demonstrated by using digital filter only and without using optical blue filter.
Highlights
Using high brightness light emitting diode (LED) for the lighting and visible light communication (VLC) simultaneously has attracted much attenuation, since this is costeffective, and can provide electromagnetic-interference (EMI) free, license-free and high signal-to-noise ratio (SNR) link with high security [1,2,3,4,5,6,7,8,9]
When this type of LED is used in the VLC system, the direct modulation speed would be limited to about 1 MHz by the relaxation time of the phosphor
The VLC system using white-light LED can provide the benefits of license-free, EMI-free, and secure wireless communication channel with low extra cost
Summary
Using high brightness light emitting diode (LED) for the lighting and visible light communication (VLC) simultaneously has attracted much attenuation, since this is costeffective, and can provide electromagnetic-interference (EMI) free, license-free and high signal-to-noise ratio (SNR) link with high security [1,2,3,4,5,6,7,8,9]. When this type of LED is used in the VLC system, the direct modulation speed would be limited to about 1 MHz by the relaxation time of the phosphor. This means that by using on-off keying (OOK) direct modulation, the maximum achievable transmission data rate is only up to 1 Mbit/s. According to the previous studies, the transmission data rate of LED VLC could only be increased by 2 to 10 times [6,7,8] of the direct modulation speed of the white-light LED if using electrical equalization only. An important modeling of VLC channel was done in [12]
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