The researchers used a micro-LED light bulb to transmit 3.5Gbit/s via each of the three primary colours – red, green, blue – that make up white light.
Li-fi is an emerging technology that could see specialised LED lights bulbs providing low-cost wireless internet connectivity almost everywhere.
EPSRC’s Ultra-parallel visible light communications (UP-VLC) project is running from October 2012 to September 2016. The vision is built on the unique capabilities of gallium nitride (GaN) optoelectronics to combine optical communications with lighting functions, and especially on the capability to implement new forms of spatial multiplexing, where individual elements in high-density arrays of GaN based light emitting diodes (LEDs) provide independent communications channels, but can combine as displays. We envisage ultra-high data density – potentially Terabit per second per square millimeter – arrays of LEDs driven via CMOS control electronics in novel addressing and encoding schemes and in compact and versatile forms.
The tiny micro-LED bulbs, developed by the University of Strathclyde, Glasgow, allow streams of light to be beamed in parallel, each 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.
Using a digital modulation technique called Orthogonal Frequency Divisional Multiplexing (OFDM), researchers enabled micro-LED light bulbs to handle millions of changes in light intensity per second, effectively behaving like an extremely fast on/off switch.
This allows large chunks of binary data – a series of ones and zeros – to be transmitted at high speed.
Earlier this year, Germany’s Fraunhofer Heinrich Hertz Institute claimed that data rates of up to 1Gbit/s per LED light frequency were possible in laboratory conditions.
And this month, 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.
Li-fi promises to be cheaper and more energy-efficient than existing wireless radio systems given the ubiquity of LED bulbs and the fact that lighting infrastructure is already in place.
Visible light is part of the electromagnetic spectrum and 10,000 times bigger than the radio spectrum, affording potentially unlimited capacity.
Another advantage, Prof Haas argues, is that evenly spaced LED transmitters could provide much more localised and consistent internet connectivity throughout buildings.
The disadvantage of traditional wi-fi routers is that the signal weakens the further you are away from it, leading to inconsistent connectivity within offices and homes.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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