What are the advantages of a visible light communication system built with LEDs

Some time ago, a paper published in "Electronics" attracted widespread attention. Researchers used experiments to demonstrate the modulation scheme of a full-duplex LED-to-LEDVLC visible light communication system with LEDs as transmitters and receivers, through wavelength dependence. Compared with performance such as bit error rate, the result shows that VLC has obvious advantages over traditional radio frequency wireless communication.

Visible light communication (VLC), also known as nm wave communication, is a communication technology that uses the visible light spectrum of 380 to 740 nm as an information carrier. Because of its high efficiency, long life and fast response characteristics, LEDs are more suitable for wireless communication than other visible light sources.

Compared with traditional radio frequency (RF) wireless communication, VLC has the following advantages:

◆VLC has an unlicensed bandwidth of about 400THz and abundant spectrum resources.

◆VLC is easy to implement, just add a microcontroller to build a network with existing LED equipment.

◆VLC uses visible light as the carrier, which will not cause electromagnetic interference to other electronic equipment.

◆VLC link can easily set high-speed communication link above 10Gb/s.

Therefore, research on VLC has been extensively carried out, including the formulation of the IEEE802.15.7 VLC standard. In this experiment, the researchers measured the rise time and signal-to-noise ratio (SNR) of the transmitter and receiver LED colors, and summarized the dependence of the performance of the LED-to-LEDVLC on the wavelength of the transmitter and receiver LEDs.

In previous studies, on-off keying (OOK) is the simplest and most traditional modulation method in optical communications, which has the advantages of low complexity and sufficient bandwidth. The IEEE802.15.7VLC standard proposes pulse position modulation (PPM) to support dimming. PPM is another modulation scheme that can achieve higher power efficiency than OOK. However, PPM requires a more complex system and bandwidth consumption.

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier modulation scheme that exhibits high frequency efficiency. It can also send data through high-frequency sub-carriers, so that the system has strong resistance to low-frequency ambient light from other lighting sources. Robustness. In order to overcome the shortcomings of low data rate and susceptibility to other lighting sources in LED-to-LEDVLC, the researchers adopted the best LED color set setting and applied quadrature amplitude modulation (QAM) in the full-duplex LED-to-LEDVLC experiment. And direct current bias optical orthogonal frequency division multiplexing (DCO-OFDM) modulation scheme.

In addition, the researchers also analyzed the distortion and signal loss in the full-duplex LED-to-LEDVLC system. In the full-duplex LED-to-LEDVLC system, 32-QAMDCO-OFDM modulation and reverse bias circuit are used to achieve a maximum data rate of 49kbps with a bit error rate of <2.5×10-4. They believe that LED-to-LED VLC technology will contribute to the widespread popularization of VLC technology.