Scientists create wireless network with LED room light

German researchers have demonstrated how regular LEDs can be turned into an optical WLAN with only a "few additional components."

Lights are no longer just for lighting up.

Scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) in Berlin, Germany, have developed a new kind of optical WAN with enough throughput to allow four people in a room to watch a film from the Internet on their laptops, in HD quality.

The technology can potentially be used on both laptops and mobile telephones.

Credit: Fraunhofer HHI

Credit: Fraunhofer HHI

The researchers say they've achieved a transfer data 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). This area also marks the radius in which the receiver -- a simple photo diode on the laptop -- can be placed before it is out of range.

In lab tests, the team pushed speeds even further using red-blue-green-white light LEDs. Those transmitted data at a blistering 800 Mbit/s, setting a record for VLC or visible light communication.

Klaus-Dieter Langer, the project leader said:  “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 system works because the modulation of the light is imperceptible to the human eye. Langer explains: "The diode catches the light, electronics decode the information and translate it into electrical impulses, meaning the language of the computer.“

While rigging a system to turn LEDs into a transfer medium may not require many components, sending data over light waves is not without challenges. The key one is that whenever on object (like a hand) comes between the light and the photo diode the transfer is impaired.

The HHI scientists stress that the optical WAN is not intended to replace other networks, but rather serve as an additional and low-invasive option in environments where radio transmission networks are not desired or not possible, such as hospital surgical rooms.

"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," notes a release.

The scientists will demonstrate how videos are transmitted by light at the International Telecommunications Fair IFA (Internationale Funkausstellung IFA) in Berlin from September 2-7, 2011.


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