LEDs transfer data to mobile devices

Ashley N. Paddock, ashley.paddock@photonics.com

Regular LEDs in overhead lighting are being turned into an optical wireless area network that transfers high-speed data from the Internet directly to laptops and other mobile devices – safely and with no loss in quality.

Under the European Union’s Omega project, scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) demonstrated visible-light communication (VLC) technology that transfers information wirelessly. Their collaborators were industry partners Siemens and France Telecom Orange Labs.

The new technology eliminates the need to install a different setup in the home to reap the benefits of VLC-enabled data transfer; the LEDs used for room lighting multitask by acting as data transmitters. With the aid of a modulator, the LEDs are turned off and on in rapid succession – imperceptible to the human eye – to transfer information. A simple photodiode on the laptop acts as the receiver.

In the future, data may be transferred to laptops with the help of LEDs. Images courtesy of Fraunhofer HHI.

Using overhead LEDs that can light an area of about 10 sq m, HHI scientists demonstrated actual data transfer at a speed of 100 Mb/s without any loss. The scientists say that, to work, the receiver could be placed anywhere within the 10-sq-m radius. They were successful in transferring four high-definition videos to four laptops simultaneously.

One advantage of the technology is its simplicity: Preparing the LEDs to function as transfer media takes only a few components. A disadvantage is that as soon as something comes between the light and the photodiode – for instance, someone’s hand held over the diode – the transfer is impaired.

The scientists emphasize that VLC is not intended to replace regular wireless area networks, PowerLAN or the universal mobile telecommunications system, but rather to serve as an additional option for data transfer where radio transmission networks are not desired or not possible. The technology is suitable for hospitals, airplanes and production facilities, where radio transmissions often interfere with processes.

“In the short term, we expect some interesting applications in settings for which electromagnetic waves are either undesirable or merely cannot be transmitted,” said Dr. Anagnostis Paraskevopoulos of HHI. “Those settings could be situated in the industry, but in a hospital or an airplane cabin as well. In midterm, depending on the success of LEDs in home applications, one can imagine the add-on effect.”

The scientists are developing their systems toward higher bit rates. When using a combination of red, blue, green and white LEDs, they were able to transmit 800 Mb/s in the lab – a world record for the VLC method.

“Current research focuses on the system optimization toward higher data rates, but aims as well to develop data transmission demonstrators, which are easy to integrate in already existing settings (e.g., Ethernet signal transmission),” Paraskevopoulos said.

Two such demonstrations were shown in September at the International Telecommunications Fair in Berlin.