Flickering lights are annoying but they may have an upside. A system that uses rapid pulses of light called Visible Light Communication (VLC), can transmit information wirelessly. Now it may be ready to compete with conventional Wi-Fi.
“At the heart of this technology is a new generation of high-brightness light-emitting diodes,” says Harald Haas, from the University of Edinburgh, UK. “Very simply, if the LED is on, you transmit a digital ‘one’, if it’s off you transmit a ‘zero’,” Haas says. “They can be switched on and off very quickly, which gives nice opportunities for transmitting data.”
It is possible to encode data in the light by varying the rate at which the LEDs flicker on and off to give different strings of ones and zeros. The LED intensity is modulated so rapidly that human eyes cannot notice, so the output appears constant.
More sophisticated techniques could dramatically increase VLC data rates. A team at the University of Oxford focuses on parallel data transmission using arrays of LEDs , where each LED transmits a different data stream. Other groups use mixtures of red, green and blue LEDs to alter the light’s frequency, with each frequency encoding a different data channel.
Li-Fi, as it has been dubbed, has already achieved blisteringly high speeds in the lab. Researchers at the Heinrich Hertz Institute in Berlin, Germany, have reached data rates of over 500 megabytes per second using a standard white-light LED. And Haas has set up a spin-off firm to sell a consumer VLC transmitter that is due for launch next year. It is capable of transmitting data at 100 MB/s – faster than most UK broadband connections.
Once established, VLC could solve some major communication problems. In 2009, the US Federal Communications Commission warned of a looming spectrum crisis: because our mobile devices are so data-hungry we will soon run out of radio-frequency bandwidth. Li-Fi could free up bandwidth, especially as much of the infrastructure is already in place.