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Posted August 3, 2016

Cables are history; all communication between all our various electronic devices is now to be wireless. Today, our devices communicate via radio signals in the free frequency band (2.4 GHz). The advantage of this wavelength is that everyone can transmit on it; the drawback is that it offers only a limited range, so the numerous wireless devices often disrupt one another. Simply put, more bandwidth is required—and this is precisely what is available through LED lights.

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Electronic signals consists of a series of 1s and 0s, which are altered (modulated) so that they can be transmitted and decoded. Modulation can be performed in radio waves, which we know as ‘Wi-Fi’. A few years ago, however, the Scottish engineer Harald Haas demonstrated that it was also possible to transfer the signals through an ordinary household lamp by having it flash at a frequency invisible to the human eye, while still providing normal illumination.

This method for transferring information has actually proved to be many times faster than Wi-Fi, but it is subject to several physical limitations. For example, the light must of course shine directly on the receiving device, and communication is only possible in one direction: from lamp to receiver. For two-way communication to be possible, the light must be supplemented by the well-known radio waves. So the optimistic name ‘Li-Fi’ that the phenomenon has been given may be a little misleading. Nevertheless, there is huge potential in the technology known as ‘Visible Light Communication’.

DTU Fotonik is currently working with several aspects of the phenomenon: from optimization of the light sources themselves, their efficiency and service life, to development of detectors and control electronics for the LED lights. The researchers have received a comprehensive briefing from companies, local authorities and hospitals on the subject of potential uses for the communicative lights when major investments in LED lights are being planned.

However, there is still a long way to go before Li-Fi becomes a common form of communication, as Professor Las Dittmann emphasizes:

“A few systems are already available on the market, but these are what are known as ‘link systems’, i.e. one-way communication. Our test platform in Doll Living Lab in Albertslund features a number of lamp-posts that support Li-Fi, but we need to develop receiving equipment as well. Apple may be including some kind of Li-Fi support in its next iPhone. They have already demonstrated that you can use the camera as a receiver, but it is difficult to get the light to hit the camera aperture precisely. So it seems they are working with other solutions that are better at receiving the light.”

However, even though Li-fi is limited to one-way communication, Lars Dittmann has no difficulty identifying numerous opportunities in the technology. These are presented in the graphics on this page.

Source: DTU

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