Optical WLAN uses LED light for up to 800 Mbit/s networking

Aug 1, 2011
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Networking researchers have used LED lighting to distribute Full HD movies to notebooks, smartphones and other devices, in a system that could join WiFi and PowerLine networks in shuttling high-speed data around the home and office. The optical WLAN co-opts white LEDs used for regular illumination to transmit data at up to 100 Mbit/s, by flickering it more rapidly than the human eye can see.

It's the handiwork of the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute HHI in Berlin, Germany, where researchers have been looking at communications alternatives as part of the EU's OMEGA Home Gigabit Access project. The lighting units - which rely on normal LEDs and a simple modulator to control the flickering - each have a roughly 90 square foot range, while any gadget wanting to receive the signal is outfitted with a simple photo diode.

It's not the first time we've seen LED lighting used for line-of-sight networking. Back in 2008, the US Science Foundation gave an $18.5m grant to researchers at the University of Boston, who were experimenting with something similar. The overall appeal is obvious: the lights can apparently be modified to suit networking at little cost and with only minor adjustment, and can be used in places where traditional radio or wired networking is less feasible, such as in hospitals, on planes or in circumstances where running cables isn't a possibility. There's also no limit on the number of recipients of the data: basically, as many photo diodes as can maintain line-of-sight with the transmitter.

On the flip side, however, the researchers admit that the signal can be easily blocked if the photo diode is covered or shaded. They suggest it would work best as a companion to, rather than a replacement for, existing WiFi, 3G or other methods:

"It is best suited as an additional option for data transfer where radio transmission networks are not desired or not possible – without needing new cables or equipment in the house. Combinations are also possible, such as optical WLAN in one direction and PowerLAN for the return channel. Films can be transferred to the PC like this and also played there, or they can be sent on to another computer."

The next step is boosting transmission speed, with researchers working on increasing the data rate eightfold. "Using red-blue-green-white light LEDs, we were able to transmit 800 Mbit/s in the lab" team member Klaus-Dieter Langer suggests.


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