LED lighting system transfers online data from ceiling lamps

A practical form of LED lighting that acts as a wireless internet transmitter could be a step closer thanks to new research.

Scientists from the Fraunhofer Institute for Telecommunications in Berlin have developed a way of transferring data from ceiling lamps to a networked device below at a rate of 100Mbit/sec using visible light communication (VLC).

This could be particularly useful in locations where traditional radio-frequency wireless transmitters are not allowed because they interfere with other equipment, for example, hospitals, aircraft or broadcast production facilities.

‘For VLC, the sources of light — in this case, white-light LEDs — provide lighting for the room at the same time they transfer information,’ said project manager Klaus-Dieter Langer.

‘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.’

This switching is so rapid that it cannot be seen by the human eye but can transmit data within a range of 10m2 to any device, such as a laptop or smartphone equipped with a photo diode to act as a receiver.

‘The diode catches the light, electronics decode the information and translate it into electrical impulses, meaning the language of the computer,’ said Langer.

The LED lamps can be turned into transmitters using a small number of components. The Fraunhofer team was able to transfer four high-definition videos to four different laptops at the same time using one transmitter.

But there must be a clear path between the light and the receiver for the transfer to work properly. If the diode is blocked by a user’s hand it will impair the transmission.

The scientists emphasise that VLC is not intended to replace regular wireless networks but is best suited as an additional option for data transfer where radio-transmission networks are not desirable or not possible.

For example, it could be used in hospitals to control wireless surgical robots or transmit X-ray images, or to play videos on aircraft entertainment systems without the need to connect each screen with wires.

The team is now working on improving the transfer rate and in the lab has achieved 800Mbit/sec using red-blue-green-white light LEDs — a world record for VLC.