Honglei Li

High Bandwidth Visible Light Communications Based on a Post-Equalization Circuit

A research in extending bandwidth of the visible light communication (VLC) system that uses phosphorescent white LED has been reported in this letter. Slow response of the phosphorescent component limits the modulation bandwidth of white LED to the lower MHz range. In this letter, we present a post-equalization circuit that contains two passive equalizers and one active equalizer. With blue-filtering and the post-equalization circuit, a bandwidth of 151 MHz has been achieved in our VLC system, which allows OOK-NRZ data transmission up to 340 Mb/s. The VLC link operates at 43 cm using a single one Watt white LED, and the bit-error-ratio was below 2×10-3, which is within the forward error correction limit.

A 550 Mbit/s real-time visible light communication system based on phosphorescent white light LED for practical high-speed low-complexity application

In this paper, we first experimentally demonstrate a 550 Mbit/s real-time visible light communication (VLC) system based on nonreturn-to-zero on-off keying (NRZ-OOK) modulation of a commercial phosphorescent white light LED. The 3-dB modulation bandwidth of such devices is only a few megahertz. We proposed an analog pre-emphasis circuit based on NPN transistors and an active post-equalization circuit based on an amplifier to enhance the 3-dB bandwidth of VLC link. Utilizing our proposed pre-emphasis and post-equalization circuits, the 3-dB bandwidth of VLC link could be extended from 3 to 233 MHz with blue-filter, to the best of our knowledge, which is the highest ever achieved in VLC systems reported. The achieved data rate was 550 Mbit/s at the distance of 60 cm and the resultant bit-error-ratio (BER) was 2.6 × 10(-9). When the VLC link operated at 160 cm, the data rate was 480 Mbit/s with 2.3 × 10(-7) of BER. Our proposed VLC system is a good solution for high-speed low-complexity application.

An analog modulator for 460 MB/S visible light data transmission based on OOK-NRS modulation

This article describes an analog modulator that contains modulation, a MOSFET drive, and pre-emphasis circuits for a high-speed VLC application system based on a commercial phosphorescent white LED. We propose a small signal modulation model that is implemented by an AC-coupled N-channel MOSFET circuit and present a pre-emphasis circuit to enhance the 3 dB bandwidth of a VLC link. Utilizing our proposed analog modulator combined with blue filtering, the 3 dB bandwidth of a VLC system could be extended from 3 to 175 MHz, which allows OOK-NRZ data transmission up to 460 Mb/s with BER below 10-9 under a 1 m radial distance. With a simple analog modulator based on the simplest OOK-NRZ modulation scheme, a high-speed VLC system could be realized. The VLC link with the proposed analog modulator is a good solution for a high-speed low-complexity and low-cost practical VLC application system.

10 Mbps Ethernet Access for Indoor Personal Local Area Network based on a Phosphorescent White LED

This paper reports a visible light communication application system realizing 10 Mbps Ethernet access for indoor personal area network based on a phosphorescent white LED, operating with high signal to noise ratio (>45 dB).