Wireless network using visible light

In a ten-year research project, US scientists at Boston University, Rensselaer Polytechnic Institute and the University of New Mexico plan to develop (PDF) optical data-transfer communications which would be used like current radio-based wireless LANs (WLANs) – and which in some roles might even replace them.

The system would use very rapidly-switched individual LEDs, which would also provide normal room lighting. The researchers have incorporated both transmitters and receivers into their prototype LED access point. Tom Little, head of the Smart Lighting Engineering Research Center research project, told heise Networks that only ceiling LEDs operating as access points require sufficient luminance for room lighting. Data transfer to devices such as PDAs or laptops does work with scattered light, but works best with a direct line-of-sight connection – this, according to Little, represents one of the main challenges for the researchers. One possible solution would be a receiver which was, like many microphones, omnidirectional. It is possible to adjust transfer rates depending on direction, with slower rates for omnidirectional reception and higher rates for unidirectional transmitted and receivers. This behaviour is suited to the uses of such devices, explained Little – if they’re in a bag or under the desk, then they aren't being used.

The researchers even see the limited range of their light-based network as a security feature: the signal doesn't penetrate walls or doors. The transfer rates will be adjustable depending on the time of day. In the first stage of the project, the researchers hope to achieve speeds of between 1 and 10 Mbps.

(lghp)