Data are traveling by light

August 1, 2011, Fraunhofer-Gesellschaft
Data are traveling by light
In the future data will be transferred to laptops with the help of LEDs. (© Fraunhofer HHI)

Regular LEDs can be turned into optical WLAN with only a few additional components thanks to visible light communication (in short, VLC). The lights are then 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.

 Just imagine the following scenario: four people are comfortably ensconced in a room. Each one of them can watch a film from the Internet on his or her laptop, in HD quality. This is made possible thanks to optical WLAN. from the in the overhead lights serves as the transfer medium. For a long time, this was just a vision for the future. However, since scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute HHI in Berlin, Germany, have developed a new transfer technology for video data within the scope of the OMEGA project of the EU, its implementation in real life is getting markedly closer. 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 100 megabits per second (Mbit/s) without any losses, using LEDs in the ceiling that light up more than ten square meters (90 square 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 Dr. 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 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 emphasize that VLC is not intended to replace regular WLAN, PowerLAN or UMTS. It is best suited as an additional option for data 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 new transmission technology is 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 program on a display, saving aircraft manufacturers miles of cables. Another possible venue for the application of this technology are production facilities, where radio transmissions very often interfere with the processes.

Currently the scientists are developing their systems toward higher bit rates. “Using red-blue-green-white light LEDs, we were able to transmit 800 Mbit/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.

Explore further: Siemens Sets New Record for Wireless Data Transfer using White LEDs

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1 / 5 (1) Aug 01, 2011
What happens if I want to watch my movies with the lights off (e.g. because I use a beamer to project the image onto a wall and any light source will seriously impair contrast)?

I could see this working with IR diodes, though, as a fallback.
1 / 5 (1) Aug 01, 2011
Maybe, but IR is going to have a lower max data rate.
1 / 5 (1) Aug 01, 2011
If it reduces the data rate by a factor of two then that's still 2 HD streamed movies - More than anyone is likely to need in one room.
1 / 5 (1) Aug 01, 2011
Hmm.. when i read his article I imagined people lying on the floor with epileptic seizures , but looks like they're modulating the visible light at a rate too fast for the human brain/eye to notice.
not rated yet Aug 01, 2011
About 2 million times faster if the upper limit for seizures is 55Hz and 100Mbits/sec is a 100MHz flicker
1 / 5 (1) Aug 02, 2011
About 2 million times faster if the upper limit for seizures is 55Hz and 100Mbits/sec is a 100MHz flicker

The upper limit for effects on the vgetative nervous system for flickering light is somewhat higher (around 100-200Hz) but still significantly lower than 100MHz.

Maybe it's not even necessary for every light to flicker. If we're talking about LEDs then we might have a light mix of red, blue and green LEDs to get pleasant lighting conditions. If only the blue LEDs do the strobing then the effect might be even less problematic

(actually, best would be low intensity UV LEDs because then you would have the added bonus that it works 'in the dark')
not rated yet Aug 02, 2011
To antialias: Why not just use the projector or beamer as the source itself? It can and does transfer with regular leds, so if you added them on as part of the projector it might work.
1 / 5 (1) Aug 02, 2011
To antialias: Why not just use the projector or beamer as the source itself? It can and does transfer with regular leds, so if you added them on as part of the projector it might work.

Chicken and egg?

I transmit the movie with the beamer which I want to watch via the beamer?

Funny thought, though.

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