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Li-Fi networks: using LEDs and visible light for broadband

Posted By TelecomTV One , 31 January 2013 | 3 Comments | (0)
Tags: M2M IoT Li-Fi LEDs Optical Broadband

Li-Fi uses LEDs and 'visible' light to transmit data through the air as an alternative to short-range radio. Now a UK consortium claims it's got a killer idea that will give the concept the lift it's looking for - why not combine Li-Fi with traditional lighting? By I.D. Scales.

A research effort led by the University of Strathclyde and involving several UK universities and an injection of government funding, is working on combining data transmission with the conventional  "illuminating" application in the home and in public places.  

“Imagine an LED array beside a motorway helping to light the road, displaying the latest traffic updates and transmitting internet information wirelessly to passengers’ laptops, netbooks and smartphones," explains Professor Martin Dawson, of Strathclyde, who is leading the four-year initiative. This "energy-saving parallelism" is the key to getting Li-Fi developed and supported, he says. "We believe our pioneering technology could deliver.”
It's one of those difficult ones, isn't it?  At first read the combined light and data concept sounds utterly plausible, inevitable even.  But then the doubts set in - too good to be true?  Just one example: about 15 years ago we all got excited by the idea of low earth orbit (LEO)  satellites replacing or at least enhancing cellular.  But then..  nothing much happened.  Could we be in LEO territory?
Here's why it might work. Proponents say that the use of light-emitting diodes (LEDs) in everyday lighting is expected to become dominant over the next 20 years. The pertinent thing about LEDs is that they actually work as lights by flicking on and off thousands of times a second - in other words they have a bearer signal already.
 Clearly by tinkering with the length and state of the flickers it will be possible to encode data.
So instead of developing Li-Fi LEDs around 1mm2 in size, which other researchers around the world are concentrating on, the  UK funded team is developing tiny, micron-sized LEDs which potentially offer a number of  advantages, according to the Universities...
"Firstly, the tiny LEDs are able to flicker on and off 1,000 times quicker than the larger LEDs, meaning they can transmit data more quickly. Secondly, 1,000 micron-sized LEDs would fit into the space occupied by a single larger 1mm2 LED, with each of these tiny LEDs acting as a separate communication channel. A 1mm2 sized array of micron-sized LEDs could therefore communicate 1,000 x 1,000 – or, in other words, one million – times as much information as one 1mm2 LED.
"Each micron-sized LED would also act as a tiny pixel. This means one large LED array display – for example, used to light a living room, a meeting room or the interior of an aircraft – could also be used as a screen displaying information, at exactly the same time as providing internet communications and lighting.
"Eventually, it could even be possible for the LEDs to incorporate sensing capabilities too. For example, a mobile phone could be equipped with a flash that – when pointed at a shop display in which every item has been given an electronic price tag – could display the price of these items." 

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(1) 31 January 2013 16:59:04 by Melvyn Hunt

"A 1mm2 sized array of micron-sized LEDs could therefore communicate 1,000 x 1,000 – or, in other words, one million – times as much information as one 1mm2 LED."
Well only if the signals from the individual LEDs can be separately decoded. I think the only way that that would work better than multiplexing on a single LED is if the LEDs emitted light at 1000 different frequencies and the receiver could split them up before demodulating each one. Sounds unlikely.

(2) 31 January 2013 18:07:13 by Francis McInerney

Ian, This is an area of huge opportunity. The best part about it is that it works with the lights "off" to human eyes and is secure -- you have to be in the room being lit to get the signal. It is also efficient: you can use existing, unlicensed visible spectrum and reuse it over and over again room by room.

The benefits are exceptional and the downside minimal. Rethinking the economics of LEDs is a no brainer.

(3) 31 January 2013 22:33:30 by TelecomTV One

It is a fascinating prospect as you say Francis. I'm not sure about the outside/motorway example given (seems to me that LTE and beyond could do that). We hope to video interview the University of Strathclyde so hopefully will be able to offer more info - including an answer to Melvyn's point about how you separate out the light sources in the array