What is Li-Fi?

A look at the Wi-Fi alternative that uses visible light to transfer data at staggering speeds

Li-Fi

Light fidelity (Li-Fi) is a form of wireless communication technology that relies on light to transmit data.

The concept was first introduced by Professor Harald Haas as part of a TED talk in 2011, where he showed how it was possible to maintain high data speeds over the light spectrum.

The technology, considered part of the visual light communications (VLC) umbrella, has been designed as an alternative to Wi-Fi, which relies on radio frequency to transmit data, although some similarities exist such as data transmission being bi-directional.

It works by fluctuating the current going through an LED bulb, reducing and increasing its visible light at a speed far faster than the human eye is able to register. The fluctuating intensity of the beam is then picked up by a photoreceptor, which then passes its readings into a remote processor capable of converting the minute amplitude changes into a data stream. This data is then sent along to the various devices connected to the network.

The technology has some distinct advantages over Wi-Fi. First of all, Li-Fi is capable of sending data far faster than current technology, 224Gbits/sec (more on that below). Not only that, the light spectrum is 10,000 times larger than radio frequency, meaning it's effectively impossible to reach its capacity.

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Although visible light can't travel through walls, this makes it far more secure than Wi-Fi as access can be maintained within a secure environment. What's more, light can be bounced off walls and surfaces while still maintaining high speeds, so direct line of sight is not always necessary.

Li-Fi vs Wi-Fi: Speed

Being able to get access to the internet via an LED light bulb sounds fantastic, but users really only care about the speed and reliability of their network, and the security of their connection. So how does Li-Fi stack up against common Wi-Fi?

In lab tests, Li-Fi connections have shown to be capable of reaching 224 Gbits/sec, although it's unlikely that these speeds will be replicated widely once the technology is rolled out. Still, that's significantly faster than the theoretical maximum speed of an 802.11ac Wi-Fi network, which is just under 7 Gbits/sec.

Ofcom's late 2018 Connected Nations report said that around 860,000 UK premises still cannot get broadband with a download speed of at least 10 Mbit/sec and an upload speed of at least 1 Mbit/sec, the specification for the UK Government's broadband Universal Service Obligation (USO). Ofcom defines superfast broadband as download speeds of 30 Mbit/sec or higher, and ultrafast as download speeds of 300 Mbit/sec or higher.

Even if Li-Fi's 224 Gbits/sec never quite reaches the real world, the speeds we do get will almost certainly make current technology obsolete.

Li-Fi vs Wi-Fi: Spectrum, security and reach

Just like Wi-Fi, Li-Fi relies on available spectrum. There is good news here is there's a lot more spectrum available for it - in fact, the visible light spectrum is 10,000 times larger than the radio frequency spectrum.

While the radio spectrum, which supports Wi-Fi, is highly regulated, the visible light spectrum is not, which means the same licencing rules do not apply. The hope is that Li-Fi could alleviate the strain on the current radio spectrum and free up space for spectrum-hungry 5G.

Li-Fi has a number of security pluses when compared to Wi-Fi. Because it relies on light, it's unable to travel through walls and doors - so access to the network can be controlled for more easily. It also doesn't create electromagnetic interference, so it can be used in places like hospitals and even in aircraft, where such interference might cause problems for equipment - and for people.

Its inability to move through walls and doors is also a downside of Li-Fi, as this reduces its range and increases the complexity of setting up a network. However, because it can bounce off surfaces rather than go through them, you can create a network that reaches every part of an office or home using strategically placed Li-Fi bulbs. Of course, the bulbs need to be switched on for this to work, but they can be dimmed below the level at which the human eye can see the light.

When will I get Li-Fi at work or at home?

The concept of Li-Fi is relatively young. It was first explained in a TED talk in 2011 by its inventor Professor Harald Haas, who is now Director of the LiFi Research and Development Center at the University of Edinburgh.

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But there is a great deal of work going into the technology, and some products are currently available. To give just two examples, PureLiFi has been deploying Li-Fi products around Europe, and Signify (what used to be called Philips Lighting) is busy working away on Li-Fi too. And of course, the LiFi Research and Development Center is also working on the tech.

If the technology is able to reach mass adoption, we might one day have a mix of 5G, Wi-Fi and Li-Fi supporting data transfer, depending on the speeds we require.

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