Another optical WLAN project has demonstrated the potential for using LED lighting as a method of data transmission, with University of Edinburgh professor Harald Haas showing the 10 MBit/sec in action. Presenting a prototype anglepoise lamp at TED this month – you can watch the video after the cut – Haas illustrated how rapidly flickering the LED – faster than the human eye can discern – can allow it to embed the data for streaming video playback. Meanwhile, the technology – which Haas has dubbed D-Light, and hopes to commercialize under the new VLC (Visible Light Communications) brand – could also have applications in mobile location and positioning services.
As with the Fraunhofer Institute LED networking system we wrote about earlier this month, D-Light relies on a tiny photo diode in the receiving gadget that can decode the flickering message from the light itself. Haas suggests that the integrated cameras found in many mobile devices – such as phones and laptops – could be upgraded to support faster refresh times, and thus double as photoreceptors for the D-Light system.
Currently, the D-Light demo runs at 10 MBit/sec, but Haas expects that to scale to 100 MBit/s by the end of this year and possibly up to 1 GBit/s in the future. Although it demands line-of-sight, the researcher bills that as a potential security benefit: since you can see where the light is reaching, it’s easy to adjust coverage so that data is only transmitted where you want it to go, unlike the more blanket approach of WiFi.
As for positioning and location, Haas suggests that the relatively small coverage area of each light network node means an embedded identity code – transmitted along with the other data – would be more useful for indicating where a device was physically. Signal strength (light intensity) and time-of-arrival calculations (where three simultaneously-transmitted signals arrive at the device at slightly different points, based on where you stand in relation to those transmitters) could then pinpoint the location of the receiver, and even the height. Alternatively angle-of-reception could be used.
Unlike GPS, D-Light based positioning could be used indoors and also be a source of network connectivity. Haas sees anything with lighting being upgraded, not so much replacing WiFi in our smartphones and laptops but adding interconnectivity between traffic lights and car lights, between hospital equipment, and turning each streetlamp into a “Li-Fi” access point. When VLC will actually begin shipping products remains to be seen, however.