Science Interviews


Thu, 7th Feb 2013

LiFi: Using light to send information

Jane Reck, EPSRC, Professor Harald Haas, University of Edinburgh, Professor Martin Dawson, University of Strathclyde

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Chris -   Youíve probably heard of wireless communications or Wi-Fi.  They use radio waves and microwaves to send information.  A spinoff of that Wi-Fi is a Li-Fi.  This is a system that uses visible light to send information into mobile devices and computers.  But now, a consortium of UK universities is working on a way to take Li-Fi to a whole new level.  The EPSRCís Jane Reck has been talking to the scientists behind this project.

Harald -   Imagine that where we have light sources Ė street lamps, traffic lights, shopping windows.  Light is everywhere and letís imagine a scenario that all these light bulbs are sort of high speed wireless transmitters that connect either humans with humans or systems with systems.

Harald -   This whole area of Li-Fi, of using visible light for communications is based on the very recent emergence of light emitting diode technology as the source of lighting.

Jane -   Tiny LEDs are being developed that could simultaneously do many LEDtasks such as deliver internet connections, display information, and provide lighting.  Itís the next stage in research to use visible light to transmit information.  Professor Harald Haas from the University of Edinburgh is one of the partners in project.

Harald -   Li-Fi stands basically for light fidelity and what it essentially means is that we take the new generation of energy saving light bulbs which are made of light emitting diodes (LEDs) and we use them for illumination and data transmission.  And not only data transmission, but very high data transmission.  So, we envisage that these light bulbs will Ė in the future Ė achieve one gigabit per second and that is several times faster than a typical Wi-Fi system in a home can provide.

Jane -   The tiny LEDs being developed are made from gallium nitride.  A man-made semi-conductor material whose properties are ideal for high power, high frequency use.

Herald -   The name, itís called ultra-parallel.  It means we have a parallel transmission and the idea is sort of take many small devices where each small device is capable of transmitting very high amount data, much, much higher than a single LED, a large LED can do, take these sort of high performance little LEDs and put them into large areas so that parallel transmission is on-going.

Jane -   Professor Martin Dawson from the University of Strathclyde is leading the project.  He explains more about the novel aspects of this research and how Li-Fi will complement our existing communication systems.

Martin -   One of the benefits that Li-Fi gives is itís bringing in a new region of the spectrum.  So, itís adding spectrum to the available bandwidth for communications.  Wi-Fi is clearly very, very successful technology, but there's been a raised concern about possible health issues.  I should emphasise, there's been no evidence of any negative effect from this, but it remains a concern.  If you're communicating with lights, with visible light then there is no concern about that.  This is one of the aspects.  

There's also the security aspects.  It is possible to tap into microwave and radio broadcasts in a way that you cannot with visible light.  It can also be deployed in situations where itís not safe to have microwave or radio waves present, and that could be in an operating theatre for example.  It could be in a submarine or in an aircraft.  So, if you look at the light emitting diode that might be on your Christmas tree or in a torch for example, if you looked at that under a microscope, you would see that the size of the chip in there is about a millimetre square.  Itís a sizable component.  What weíre talking about is basically dividing up that active area into many thousands of much smaller elements.  These individual elements that we call micro LEDs or micro heads are human hair size individually.  They're on the micron, micrometre scale and when you shrink down the size of the devices; there are effects that come in to play that offer you the possibility of switching them on and off much more quickly.  And it increases the bandwidth with the on and off switching capability and speed, but some other beneficial characteristics start to come into play as well.  When you do that, you give the possibility of sending independent communications from each individual element in the array.  You not only have many, many hundreds or potentially thousands of separate individual lighting or communications channels that you can start to play with independently, but you also have a means to communicate optical images at the same time.  This is the key element of novelty here.

Jane -   With each tiny LED, acting as a separate communication channel, Martin explains more about the sort of tasks that could be carried out simultaneously.

Martin -   If you are sitting at an aircraft with a light above you, if you're in a meeting room with lights above the meeting table, then those lights are a means of broadcasting and communicating information, a potential supplement or replacement to Wi-Fi, and weíre expecting this to come in relatively quickly.  Thereíve been a number of demonstrations of this already all over the world.  Our devices offer a potential means to increase the data handling capability in that type of application.  We still have the capability to do lighting, but a means to communicate much higher quantities of information, so to download video information very quickly for example.

Jane -   This consortium of researchers also involves the Universities of Cambridge, Oxford and St. Andrews with funding from the Engineering and Physical Sciences Research Council.  The project brings together expertise from areas of electronics, computing, and materials.  Itís thought that Li-Fi could be in wide spread use within a decade.



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As the world moves away from incandescent lights to alternatives such as LEDs, this would be an excellent time to consider LED lighting, and LED networking.  One of the issues, of course, is competition with sunlight.  Many commercial buildings use a lot of light inside during the daytime.  But, I would hope they would also consider alternative energy sources such as skylights and light tubes, at least for shorter structures.

I could imagine our future room lighting being more colorful, with red lights, green lights, blue lights, and etc, each transmitting on a different channel.  Fortunately, one could likely balance multiple narrow spectrum lights to give the appearance of white light, although colored objects might not show up with the true colors.

Flickering might be a problem, but much greater frequencies would be chosen than flicker fusion of about 60 HZ.

I'm not sure about security.  If the room had no light escaping, then the transmission couldn't be intercepted.  However, if light was allowed to escape, I would think that an ordinary telescope would be able to pick up the signals quite well, even at a great distance, and with very precise localization.  One could, of course, attempt to drown out the signal with a false signal, but the fake signal would have to have an overlapping spectrum, and have sufficient randomness that it couldn't easily be subtracted out.
CliffordK, Tue, 12th Feb 2013

well the li-fi tech is for sure a new way of data transporting, but i would like to rise some problems. 1. the light have low penetrating power, so a phone equipped with li-fi will have no data reception in a purse or pocket. 2 if so, should fabric or watch or sth we wear on top be equipped with the li-fi signal recevier and transmitter instead of the molibe devices? 3. if so, will people be dress in glowing clothes just like what we saw in tron? twitte_king, Mon, 18th Feb 2013

and about CliffordK con cern of security, i personally think thats a problem of encrpyting the signal rather than the spectrum of EM wave used twitte_king, Mon, 18th Feb 2013

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