Incandescent light bulbs have been providing good and loyal service for a century, but now banned on the European continent, they have given way to LEDs, which consume ten times less energy and last thirty times longer than conventional bulbs. An additional advantage is that their applications are not limited to lighting: "intelligent" products with additional functions are emerging, including the possibility of connecting to the Internet, whether on a laptop or a smartphone. Forget wifi, long live LIFI (or Light Fidelity) !
En reality, the idea of using light to create a wireless network is not new. Everyone has heard about the smoke signals used by shipwrecked people to try to attract attention. What is less well known is that in Napoleon's time, much of Europe was dotted with smoke signals. optical telegraphsknown as semaphores.
Alexander Graham Bell, the inventor of the telephone, believed that his most important invention was the photophoneThe device was a device whose mirror directed the vibrations created by speech to a beam of light.
Just as spacing (or modulating) smoke volutes can form an SOS in Morse code, visible light communication quickly modulates the intensity of the light signal to encode data in binary, zero and ones. However, lifi transceivers do not blink, as the modulations are too fast to be perceived by the naked eye.
wifi versus lifi
The growing demand for wireless data is putting today's wifi technology - which uses the radio frequency and microwave spectrum - under enormous pressure. It is estimated that the number of mobile devices, which is growing exponentially, will exceed ten billion by 2019. By that date, the volume of information exchanged is expected to be approximately thirty-five quintillion (10
One of the fundamental principles of communications is that, at its maximum volume, data transfer is proportional to the width of the band available for electromagnetic frequencies. As radio spectrum is heavily used and highly regulated, there is simply not enough additional space to meet the growing demand. However, the lifi has the capacity to replace wifi by radio waves and microwaves.
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The potential of the visible light spectrum for communications is enormous, especially since it is neither exploited nor regulated. LED light can be modulated very quickly: researchers from the Ultra-Parallel Visible Light CommunicationsThe EPSRC (Engineering and Physical Sciences Research Council in the United Kingdom) funded study found throughput rates of up to 3.5 Gb/s (gigabits per second) with a single blue LED, and up to 1.7 Gb/s with white light.
Unlike wifi transmitters, optical telecommunications are confined to the walls of a single room. This restriction offers a key advantage: the security of the data transmitted in lifi. Once the curtains are drawn, no one is able to spy on you from outside. A series of lights fixed to the ceiling can send different signals to different users. The energy from the transmitter can be localized, exploited more efficiently, and does not interfere with nearby lifi sources. This lack of interference is another advantage over wifi. Visible light communications are therefore naturally secure, and could save air travellers from having to switch to airplane mode.
Another advantage is that the lifi uses existing power lines, so no new infrastructure is required.
Connecting the Internet of Things
L’Internet of Things is a very ambitious vision, that of a hyper-connected world where objects communicate with each other autonomously. For example, your fridge will be able to inform your smartphone that you're out of milk, and even order some for you. Sensors in your car will alert you directly by text message if your tyres are too worn or under-inflated.
Given the number of "objects" that can be covered with sensors and control devices, then connected to the network and connected, the throughput required to allow all these devices to communicate is very important. Advanced technology research and consulting firm Gartner predicts that 25 billion devices of this type will be connected by 2020. Knowing that the majority of the information will only have to be transmitted over a short distance, the lifi is the ideal - if not the only - solution to make this happen.
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Several companies already offer products for visible light communications. The Li-1st of pureLiFi, an Edinburgh-based company, is marketing a solution Plug-and-Play a simple, point-to-point Internet connection of 11.5 Mbps, comparable to first generation wifi. Another example: French Oledcommwhich exploits the secure nature of the lifi to equip hospitals.
Many technological challenges remain, but the lifi is on its way to becoming a reality. In the future, pressing the switch won't just give you light!
Pavlos ManousiadisResearch Fellow, University of St Andrews;
Graham TurnbullProfessor, Head of the School of Physics and Astronomy, University of St Andrews
Ifor SamuelProfessor of Polymer Optoelectronics, University of St Andrews