LEDs Transfer Optical Data to Mobile Devices

Common room-illuminating LEDs are now being used to transport HD video from the Internet directly to laptops and other mobile devices. With only a few adjustments, regular LEDs are being turned into optical WLANs — safely shuttling high-speed data wirelessly and with no loss in quality.

Within the scope of the EU's OMEGA project (the Home Gigabit Access project, consisting of 20 European partners from industry and academia), scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) in Berlin, in collaboration with industry partners Siemens and France Telecom Orange Labs, demonstrated VLC (visible light communication) technology that can transfer data wirelessly.

In the future, data will be transferred to laptops with the help of LEDs. (Image: Fraunhofer HHI)

What makes this technology promising is that there is no requirement to install a different setup in the home to reap the benefits of VLC-enabled data transfer. The LEDs used for lighting purposes multitask by acting as transmitters for data transfer. With the aid of a component called a modulator, the LEDs are turned off and on in very rapid succession so that information is transferred. The modulation of the light is imperceptible to the human eye. A simple photodiode on the laptop acts as a receiver.

With the help of overhead LEDs that can light an area of about 90 sq ft, HHI scientists demonstrated actual data transfer at a speed of 100 Mb/s. The data transfer was completed without any loss. The LEDs were used as transmitters, and the receiver’s maximum range was the radius that the LEDs could light up. As of now, scientists are working to increase the range of receivers. Under these conditions, they were successful in transferring four HD-quality videos simultaneously to four different receiving end gadgets (laptops in this case).

“The diode catches the light, electronics decode the information and translate it into electrical impulses, meaning the language of the computer,” said Klaus-Dieter Langer, HHI project manager.

One advantage is that it takes only a few components to prepare the LEDs so that they function as transfer media. One disadvantage is that as soon as something comes between the light and the photodiode (for example, when someone holds his hand over the diode), the transfer is impaired.

Currently, the scientists are developing their systems toward higher bit rates. “Using red-blue-green-white light LEDs, we were able to transmit 800 Mb/s in the lab,” said Langer. “That is a world record for the VLC method.”

The HHI scientists will showcase how videos are transmitted by light at the International Telecommunications Fair IFA in Berlin, to be held from Sept. 2 to 7, 2011.

For more information, visit: www.fraunhofer.de/en