Professor Harald Haas [HH]
Light is everywhere, street lamps, traffic lights, shopping windows. Imagine a scenario that all these light bulbs are high speed wireless transmitters that connect either humans with humans or systems with systems.
Professor Martin Dawson [MD]
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.
Tiny LED’s are being developed that could simultaneously do many tasks such as deliver internet connections, display information and provide lighting. It’s 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 the project.
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. We envisage that these light bulbs will in the future achieve one gigabyte per second and that is several times faster than a typical Wi-Fi system in the home can provide.
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.
The name is called ultra-parallel. It means we have a parallel transmission and the idea is to take many small devices where each device is capable of transmitting a very high amount of data, much higher than a single LED, a large LED, can do, take these high performance little LEDs and put them into large areas so that parallel transmission is on-going.
Professor Martin Dawson from the University of Strathclyde is leading the project. He explained more about the novel aspects of this research and how Li-Fi will complement our existing communications systems.
One of the benefits that Li-Fi gives is its bringing in a new region of the spectrum, so it’s adding spectrum to the available bandwidth for communications. Wi-Fi is clearly a very successful technology, but there has been concerns raised about possible health issues due to exposure of the brain so close to a microwave transmitter system. I should emphasise there has been no evidence of any negative effects from this, but it remains a concern. If you are communicating with light, with visible light, then there is no concern about that, so this is one of the aspects. There are also 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 it is not safe to have microwave or radio waves present and that could be in an operating theatre, for example, in a submarine or in an aircraft. So if you are looking at the light emitting diode that might be on your Christmas tree or in a torch, for example, under a microscope, you would see that the size of the chip in there is about a millimetre square, it’s a sizable component. What we are talking about is basically dividing up that active area into many thousands of much smaller elements. These individual elements that we call micro LEDs are human hair size. They’re on the micrometre scale and when you shrink down the size of the devices, there are effects that come into play that offer you the possibility of switching them on and off much more quickly. So this is the basis of our approach, that we can basically divide up a large area device into many thousands of much smaller area devices and it increases the bandwidth, the on 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 signals from each individual element in the array, you not only have 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.
With each tiny LED acting as a separate communication channel, Martin explained more about the sort of tasks that could be carried out simultaneously.
If you are sitting in an aircraft with a light above you, if you are 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. We are expecting this to come in relatively quickly and there have been a number of demonstrations of this already all over the world. Our devices offer a potential to increase the data handling capability in that type of application. By ganging together many small light sources rather than one big light source, we still have the capability to do lighting above your seat in the plane or above a meeting table, for example, but also a means to communicate much higher quantities of information, so to download video information very quickly for example.
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 the areas of electronics, computing and materials. It’s thought that Li-Fi could be in wide spread use within a decade.