Researchers use light from LEDs to send data wirelessly

Speeds of 230Mbit/sec. reported

Light coming from lamps in your home could eventually be used to encode a wireless broadband signal, according to German researchers.

Researchers at the Fraunhofer Institute for Telecommunications at the Heinrich-Hertz Institute in Berlin experimented with using visible light from commercial light-emitting diodes to carry data wirelessly at speeds of up to 230Mbit/sec.

Research into wireless data communications using LEDs has been going on for years, but the 230Mbit/sec. speed is considered a record when using a commercial LED, according to the Optical Society of America, an organization for optics professionals.

It could also be a potential answer to the shortage of radio spectrum bemoaned by the U.S. Federal Communications Commission and others, optical communications researchers say.

One of the German researchers on the project, Jelena Vucic, said there would be an advantage in using light to carry data over Wi-Fi or another system because the lights are already in a room. Her group's findings will be presented at the Optical Fiber Communication Conference and Exposition/National Fiber Optic Engineers Conference on March 25 in San Diego.

A signal from an LED is generated by slightly flickering all the lights in unison at a rate millions of times faster than the human eye can detect, the OSA statement said. Commercial LEDs have a limited bandwidth of a few megahertz, but Vucic's team was able to increase the amount tenfold by filtering out all but the blue part of the LED spectrum. The team built a visible wireless system in their lab to download data at 100Mbit/sec. and then upgraded the system to get 230Mbit/sec. Vucic said the team should be able to double the data rate again with some modulation adjustments.

In 2008, a separate team of U.K. researchers also explored using visible-light LEDs for wireless communications.

Sending data over fiber-optic cable at enormous speeds has been going on for decades. However, taking data transmission to an open environment such as a living room over light from a lamp would be an enormous step, and a challenging one, said Jack Gold, an analyst at J.Gold Associates.

Gold said the German research seems to show data transmission via light only in one direction and only in one room. In comparison, Wi-Fi and other radio transmissions are bidirectional and can pass through walls.

One practical concern in using visible wireless would be getting the data signal to the light itself, Gold said.

Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen or subscribe to Matt's RSS feed. His e-mail address is mhamblen@computerworld.com.

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