LEDs Deliver Speedy Wi-Fi Signals


Home wireless networks use routers that transmit data via radio waves, usually at a few hundred megabits per second. Years from now the routers might use LEDs, sending data at ten times that speed for a fraction of the cost.

A laboratory in the U.K. has demonstrated the technology with a device that transmits data in the flickering light of an LED at 10 gigabits per second. It’s called the Ultra-parallel visible light communications (UP-VLC) project, a joint venture between several British universities and partly government-funded.

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For years, engineers have been exploring the use of light as a medium for transmitting data because it offers more channels to broadcast on. That could work better in situations where lots of people are trying to access the same network to send information — say, at a conference. Currently, in these situations, when a room full of people try to access a Wi-Fi connection at the same time, their collective use of the same wireless router slows the Internet connection. Using LEDs would mean less interference.

To send a signal, the LEDs change intensity millions of times per second. This is exactly the same thing that regular wireless routers and AM radios do, except with visible light rather than radio waves.

To further boost the data-carrying capacity, the researchers transmitted the data on three different wavelengths of light: red, blue and green. Each carried 3.5 gigabits per second. To the eye, the three signals just looked like a white light. The light actually flickered, but it was too fast for humans to see.

Germany’s Fraunhofer Institute demonstrated LED-based data transmission as well, at speeds up to 3 Gbits/s. Chinese and American teams have also shown that LED transmission and receiving can be done — there’s at least one company called Visible Light Communications promoting slower versions of the technology.

As with any new technology there’s a down side. One issue with visible light is that it is line-of-sight. Unlike radio waves, light from LEDs doesn’t bend around corners easily. Light waves also don’t penetrate solids, whereas a wireless router works even in another room. And it won’t be easy to make this work in bright sunlight, as the sun would overwhelm the receivers.

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Visible light would, however, work better than radio in places with lots of interference, like a trade show in which thousands of cell phone conversations and wireless connections are happening at once. Because the flickering of the LEDs is so fast, people can’t see it and so the signal could be integrated into a room’s overhead lights.

via BBC, University of Edinburgh

Credit: University of Edinburgh

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