October 29, 2013…UK researchers have reported achieving 3.5Gbit/s transmission of data via “li-fi” using each of the three primary colored ( red, blue, and green) groups of micro LEDs. The research, known as the ultra-parallel visible light communications project, is a joint venture between the universities of Edinburgh, St Andrews, Strathclyde, Oxford, and Cambridge, and funded by the Engineering and Physical Sciences Research Council. The project used tiny micro-LED bulbs, developed by the University of Strathclyde, Glasgow, that allow parallel streams of light that effectively multiplying the amount of data that can be transmitted at any one time.
“If you think of a shower head separating water out into parallel streams, that’s how we can make light behave,” said Prof Harald Haas, an expert in optical wireless communications at the University of Edinburgh and one of the project leaders.
The transmission used a digital modulation technique called Orthogonal Frequency Divisional Multiplexing (OFDM). This technique enabled micro-LED light bulbs to handle millions of changes in light intensity per second, effectively behaving like an extremely fast on/off switch. Therefore large chunks of binary data – a series of ones and zeros – could be transmitted at high speed.
Researchers from around the world are attempting to reach faster and faster transmission speeds. Germany’s Fraunhofer Heinrich Hertz Institute earlier this year claimed that data rates of up to 1Gbit/s per LED light frequency were possible in laboratory conditions. In October, Chinese scientists reportedly developed a microchipped LED bulb that can produce data speeds of up to 150 megabits per second (Mbps), with one bulb providing internet connectivity for four computers.
Professor Harald Haas of the University of Edinburg a pioneer of “Li-Fi”, is one of the researchers on the project. He is Chair of Mobile Communications in the Institute for Digital Communications (IDCOM) at the University of Edinburgh and he currently is the CSO of a university spin-out company pureVLC Ltd. He coined the term “light fidelity” or li-fi – also known as visual light communications (VLC) – and set up a private company, PureVLC, to exploit the technology. Haas argues that visible light is part of the electromagnetic spectrum and 10,000 times bigger than the radio spectrum, affording potentially unlimited capacity.
Prof Haas also contends that evenly spaced LED transmitters could provide much more localized and consistent internet connectivity throughout buildings. Whereas the signal from traditional wi-fi routers weakens the further you are away from it, leading to inconsistent connectivity within offices and homes. Prof Haas also asserts that light’s inability to penetrate walls makes VLC technology potentially more secure than traditional wi-fi connectivity.