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In this paper, we propose and experimentally demonstrate HyperSight, which is a precise image decoding algorithm for the mobile-phone camera based visible light communication (VLC) system. The conventional algorithms have to select an appropriate column matrix, and then decode the image according to the fitting curve. The selection of the column matrix and the fitting of the function are not only time-consuming but also error-prone, leading to low decoding efficiency and high bit error rate (BER). While HyperSight calculates characteristic grayscale matrix to avoid column matrix selection and uses critical grayscale to replace the function fitting to decode the image. As expected, our algorithm not only reduces the BER, but also improves the processing performance. The experimental results show that, the BER can be reduced by two orders of magnitude on average compared with the conventional scheme. For the $4.8\,$ kbps data rate, our algorithm can achieve the transmission distance of $50\,$ cm under the $7\%$ forward error correction (FEC) threshold with the low illuminance of $702\,$ lux.

In this article, a novel method for constructing a pre-equalizer by optimized filter synthesis with vector fitting is proposed to broaden the bandwidth of a visible light communication (VLC) system. By using the proposed method, an active-passive hybrid equalization circuit is constructed, and it is demonstrated that the 3-dB bandwidth of the VLC system with commercially available phosphorescent white LED is extended from 30 MHz to 600 MHz. A 1.35 Gb/s NRZ-OOK VLC transmission over 12 cm free space transmission distance is experimentally realized, achieving a bit error rate (BER) of $\text{8.8} \times \text{10}^{-\text{5}}$ . To the best of the authors knowledge, this is the largest reported 3-dB bandwidth and real-time data rate achieved in the VLC system with a single commercially phosphorescent white LED.

An overall bit rate of 625 Mb/s real-time multi-access VLC system is presented in this paper. In order to decrease the effect of ambient light and deal with the non-linearity of LED, we propose a new algorithm to get orthogonal codes which is suitable for OOK modulation. By employing a single white LED and three photo diodes, three users are provided access to the VLC system individually at the same time. A data frame and CRC32 are adopted to realize a reliable and continuous data interaction between Ethernet and VLC system. All the numerical calculations are implemented by FPGAs so as to provide a practical high-speed transmission.

In the paper, a mixed-interval multi-pulse position modulation (MI-MPPM) scheme for visible light communication (VLC) system is theoretical proposed and implemented on field programmable gate array (FPGA). It has better bandwidth efficiency than PPM and MPPM. And it has better anti-jamming than MPPM. A real-time VLC link based on phosphorescent white LED is also built to measure the performance of the proposed MI-MPPM scheme. The data rate of 104 Mbps in our VLC system under the distance of 60 cm could be achieved, and bit error rate is 3 . 81 × 1 0 − 5 . As far as we know, it is the highest data rate that can be achieved in continuous real-time VLC system with phosphorescent white LED based on PPM and its derivative modulation. The performance of VLC system under different distances, advantages and the possible application scenarios of MI-MPPM are also discussed.

Silicon photocell acts as the detector and energy convertor in the VLC system. The system model was set up and simulated in Matlab/Simulink environment. A 10 Hz square wave was modulated on LED and restored in voltage mode at the receiver. An energy gathering and signal detecting system was demonstrated at the baud rate of 19200, and the DC signal is about 2.77 V and AC signal is around 410 mV.

In order to ensure stable, correct and real-time high-speed transmission of indoor visible light communication (VLC), the key modulation and demodulation technologies of orthogonal frequency division multiplexing (OFDM) are studied in this paper. The time-domain synchronization, frequency synchronization and channel equalization of receiver are analyzed and optimized by utilizing short and long training preamble. Moreover, field programmable gate array (FPGA) development board (Xilinx Kintex-7) and Verilog hardware description language are used to realize the design of proposed OFDM-VLC system. Simulation and experiment both verify the feasibility of the hardware designs of this system. The proposed OFDM-based VLC system can process signal in real-time, which can be used in actual VLC application systems.

Nowadays the yellow emissive YAG:Ce phosphors play an important role in fabricating white light-emitting diodes (WLEDs). However, they are deficient in red emission so we proposed polymer dot phosphors to compensate this poor photometric property. The polymer dot phosphors exhibited broad emission bands under excitation of a blue LED chip with weak reabsorption. We demonstrated hybrid white light-emitting diodes with commendable color rendering index (85–95), widely variable color temperatures (3050–7295 K) and high luminous efficacy (72–80 lm W−1 operated at 20 mA) by combining green and red emitting polymer dots on YAG:Ce-based WLEDs. The optical properties suggest the polymer dot phosphors are the suitable color converting materials, which may enable their application in WLED lighting.

We propose and experimentally demonstrate a multi-channel uplink visible light communication (VLC) system for the first time, which is based on three commercially available white light emitting diodes (LED) and only one photo-diode (PD). By employing independent Xilinx field programmable gate arrays (FPGA), we realize the real-time data transmission. The on–off keying (OOK) modulation and time division multiple access (TDMA) techniques are combined together to offer a reliable multiple uplink access for three users. The electrical idle signal is designed to deal with serious inter-symbol interference (ISI) caused by the overlap of different LED signals at the receiver side, as well as to provide a stable illuminating environment. The experiment results indicate that our scheme has a great potential for the indoor practical VLC system implementation.

This paper reports a high-speed OOK-NRZ visible light communication system using red, green and blue LDs, data rates of 1940Mb/s, 2660Mb/s and 2670Mb/s are obtained over distance of ∼1.5m. All the BERs are below 10-9.

The bandwidth of white light emitting diodes (WLEDs) is an important factor that affects most of the system performances in visible light communication (VLC). It is mainly limited by the down-conversion phosphors. We propose in this paper to employ nanomaterial phosphors with short fluorescence lifetime and high quantum yield in VLC. The white-emitting device of bandwidth-based lifetime was fabricated by using several kinds of nanophosphors with different fluorescence lifetimes. Moreover, we proposed two theoretical models to analyze the factors that affect bandwidth. Compared with the commercial YAG-based WLEDs, the bandwidth of nanophosphor-based WLEDs can be improved over three times and close to the blue excitation sources. Our study indicates that nanophosphors can become promising fluorescent materials in VLC, and provides a new direction for developing wide-bandwidth VLC systems.

Quantum dot white light-emitting diodes (QD-WLEDs) were fabricated from green- and red-emitting AgInS2/ZnS core/shell QDs coated on GaN LEDs. Their electroluminescence (EL) spectra were measured at different currents, ranging from 50 mA to 400 mA, and showed good color stability. The modulation bandwidth of previously prepared QD-WLEDs was confirmed to be much wider than that of YAG:Ce phosphor-based WLEDs. These results indicate that the AgInS2/ZnS core/shell QDs are good color-converting materials for WLEDs and they are capable in visible light communication (VLC).

Visible light communication (VLC) is an emerging technology in optical wireless communication (OWC) that has attracted worldwide research in recent years. VLC can combine communication and illumination together, which could be applied in many application scenarios such as visible light communication local area networks (VLANs), indoor localization, and intelligent lighting. In recent years, pioneering and significant work have been made in the field of VLC. In this paper, an overview of the recent progress in VLC is presented. We also demonstrate our recent experiment results including bidirectional 100 Mbit/s VLAN or Li-Fi system based on OOK modulation without blue filter. The VLC systems that we proposed are good solutions for high-speed VLC application systems with low-cost and low-complexity. VLC technology shows a bright future due to its inherent advantages, shortage of RF spectra and ever increasing popularity of white LEDs.