Berlin, Germany--By simply modulating the LEDs in an LED lighting fixture, it can become a digital transmitter for an optical wireless local-area network (WLAN). Researchers at Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI), Siemens, and France Telecom Orange Labs are working to make this concept practical, which would allow simultaneous transmission of multiple video to photodiode-equipped computers and mobile phones.
By the end of May this year, the scientists were able to deomonstrate the transfer ot data at a rate of 100 Mbit/s without losses, using ceiling LEDs in the ceiling that illuminate ten square meters or more. The receiver can be placed anywhere within this area. “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 scientists are working on 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 visible-light-communication (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.
Uses include VLAN in hospitals, for example, where radio transmissions are not allowed. Despite this fact, high data rates must be transmitted without losses. If communication occured via light in the surgical room, it would be 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 often interfere with industrial processes.
One disadvantage is that as soon as something gets between the light and the photodiode (for example, when someone holds a hand over the diode) the transfer is impaired.
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 transfer where radio transmission networks are not desired or not possible--without requiring new cables or equipment. Combinations are also possible, such as optical WLAN in one direction and PowerLAN for the return channel.
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