We've talked about Li-Fi – using modulated LEDs as data channels – before at The Register, but last week's announcements warrant revisiting the idea.
Photons make good communications channels: that's why the Internet's fattest pipes are optical fibre. Even the idea of using ambient light carry data has been around for nearly three decades.
For example, this deployment in 2004 of a technology called ILID (electronic supermarket shelf tags getting their data from modulated fluorescent lights) represented the culmination of work that began in the late 1980s.
What's different about Li-Fi is its speed. In early demonstrations in 2012 it already showed promise, with talk of 130 Mbps speeds. That was borne out in 2013, when Chinese researchers ran 150 Mbps transmissions to four computers simultaneously.
Most recently, Estonian company Velmenni created buzz last week by demonstrating a 1 Gbps implementation of the technology.
The idea behind Li-Fi is seductively simple: we know that LEDs can be modulated at very high speeds, because that's what line-of-sight infrared communications systems use, and they passed the 2 Gbps mark long ago.
The biggest constraint of the technology is also part of its advantage: unlike Wi-Fi signals, Li-Fi doesn't pass through walls. This constrains the reach of the technology – but at the same time, the 150 MHz a light bulb delivers to a user in the office doesn't interfere with the 150 MHz another user is getting in the lounge-room.
Being blocked by walls also means you don't have to worry about a drive-by hacker (although you'd want a deployment model that meant your porch light wasn't broadcasting your private data).
The technology is strictly indoors-application-only (since sunlight blocks it), but the Chinese experiments at the Shanghai Institute of Technical Physics in 2013 also demonstrated that the LEDs can be dimmed to near-darkness and still communicate.
The biggest roadblock to Li-Fi right now is a lack of standards.
The IEEE had a shot at standardising the PHY and MAC layers for visible light communications in 2009, creating the 802.15.7 working group, but those specifications don't cover Li-Fi. ®