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Aug 4th, 2011
LEDs serve as optical WLAN to transfer video
Scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) in Berlin, Germany, as part of the OMEGA project of the EU, have developed a new visible light communication (VLC) data transfer technology for video data that uses light from the LEDs in the overhead lights to serve as the transfer medium turning regular LEDs into optical WLAN with only a few additional components.
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In the future data will be transferred to laptops with the help of LEDs.
In the future data will be transferred to laptops with the help of LEDs.

According to researchers, the lights are not just lighting up, they also transfer data. They send films in HD quality to your iPhone or laptop, with no loss in quality, quickly and safely

At the end of May, the scientists were able to present the results of the project in Rennes, France. They were able to transfer data at a rate of 100Mb/s without any losses, using LEDs in the ceiling that light up more than 10sq.m (90sq.feet). The receiver can be placed anywhere within this radius, which is currently the maximum range. "This means that we transferred four videos in HD quality to four different laptops at the same time," says Anagnostis Paraskevopoulos from the HHI.

"The fundamentals of visible light communication (VLC) were developed together with the industry partners Siemens and France Telecom Orange Labs," said the expert. At HHI, the team of project manager Klaus-Dieter Langer is now further developing the new technology. "For VLC the sources of light—in this case, white-light LEDs—provide lighting for the room at the same time they transfer information. With the aid of a special component, the modulator, we turn the LEDs off and on in very rapid succession and transfer the information as ones and zeros. The modulation of the light is imperceptible to the human eye. A simple photo diode on the laptop acts as a receiver." As Klaus-Dieter Langer explains, "The diode catches the light; electronics decode the information and translate it into electrical impulses, meaning the language of the computer." 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 gets between the light and the photo diode (for example, when someone holds his hand over the diode) the transfer is impaired. Laptops, Palm devices or mobile telephones are all potential end devices.

The scientists emphasise that VLC is not intended to replace regular WLAN, PowerLAN or UMTS. It is said to be 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.

This transmission technology is said to be suitable for hospitals, for example, because radio transmissions are not allowed there. Despite this fact, high data rates must be transmitted without losses and unzipped, according to the experts. If part of the communication occurs via the light in the surgical room, this would make it possible to control wireless surgical robots or transmit x-ray images. In airplanes, each passenger could view his own entertainment programme on a display, saving aircraft manufacturers miles of cables. Another possible venue for the application of this technology includes production facilities, where radio transmissions very often interfere with the processes.

Currently the scientists are developing their systems towards higher bit rates. "Using red-blue-green-white light LEDs, we were able to transmit 800Mbit/s in the lab," said Klaus-Dieter Langer. "That is a world record for the VLC method." The HHI scientists will showcase how videos are transmitted by light in Hall 11.1, Booth 8 at the International Telecommunications Fair IFA (Internationale Funkausstellung IFA) in Berlin from September 2-7, 2011.

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