Lightbulbs delivering internet access 100 times faster than Wi-Fi sounds like science fiction but, as David Crookes explains, Li-Fi is about to become a reality
What is it?
Li-Fi is short for Light Fidelity and is a way of transmitting data at high speed using the visible light spectrum rather than radio waves. The bi-directional technology is built to work with LED lightbulbs, which means it’s very easy to set up and the potential reach is huge.
How does it work?
Li-Fi requires two components: a semiconductor light source - that is, an LED - fitted with a small chip that allows it to process signals: and a device with a photodiode that can receive light signals. The LED bulb is connected to an Ethernet-wired ceiling device and its light intensity is then modulated to make it brighter. This beams out the necessary data stream that can be picked up by the light receivers on various devices so they can translate the signal into internet bandwidth.
Whoa - slow down, egghead! Who on Earth thought this up?
The technology - not to mention the word itself - is the brainchild of Harald Haas, Professor of Mobile Communications at the University of Edinburgh. He brought the idea to light (pardon the pun) in a TED Talk in 2011, but he has since set up a company called PureLiFi, which researches and promotes the concept. You can view his talk on YouTube at bit.ly/harald387.
What are the benefits of Li-Fi?
Using light allows current Li-Fi technology to be 100 times faster than Wi-Fi. Indeed, the speeds are around a gigabit per second, which is pretty astonishing, especially given that Li-Fi doesn’t clash with radio signals. Researchers are working on speeding up the semiconductors further for even faster Li-Fi connections. As it stands, lab tests at the University of Oxford have achieved bi-directional speeds of 224Gbps, which is more than twice the speed of fibre-optic networks. Wi-Fi can ‘only’ reach 600Mbps.
But doesn't fibre optic also use light?
Yes it does, clever clogs, and it allows for broadband speeds that far surpass standard copper-wire connections. But fibre optic is a wired connection whereas Li-Fi is wireless - and no other wireless connection is currently as fast. It beats Wi-Fi because the visible light spectrum is 10,000 times larger than that of the radio spectrum so Li-Fi effectively becomes a very wide virtual pipe through which data can travel. Coming at a time when the traditional radio-wave spectrum is becoming overcrowded, using light will free up resources.
Will I see the flashing lights?
No, the speed is so great that the change is imperceptible to the human eye. Although Li-Fi LEDs will flicker billions of times per second - as opposed to the 20,000 times per second of standard LEDs - the light will appear static. It means there are two benefits: speedy wireless internet and the ability to light up a room. It’s certainly a tidy solution.
What if I don't want the light turned on?
Well, gloomy guts, the LEDs can be dimmed to the point where you wouldn’t notice any light being emitted, while still allowing for continued data transfer that will let you connect your phone, tablet, computer and other devices to the internet. However, experts say that the lower light level may make for a slower connection.
Where can the technology be used?
As we’ve said, because there is no interference with radio signals, you’ll be able to safely use Li-Fi on an aeroplane. It can also be used underwater and there has been some testing of this by the US Navy to see how effective it would be in communication with submarines. A company called Velmenni in Tallinn, Estonia, has recently been testing Li-Fi in an office, which is the first real-world test to have been carried out.
Are there any limitations?
Indeed there are. The light, as you’d expect, cannot penetrate walls, which means that every room needs to have its own lightbulb if you want to wander around without losing connection. Also, direct sunlight interferes with a long-range Li-Fi signal, which makes it difficult to use outdoors.
Is Li-Fi secure, though?
Very much so and far more than Wi-Fi because the receiver has to be close to the transmitter bulb. Someone with a laptop sitting outside your home - or even in the next room - won’t be able to intercept your Li-Fi signal. In that sense, it is quite unlike Wi-Fi, which can easily be intercepted by other people. No wonder intelligence agencies are interested.
What devices are available?
PureLiFi has worked on a couple of products. The first, the Li-lst, was designed to be a testing device. It has a ceiling unit connected to a standard LED bulb and a desktop unit that connects to a laptop via USB. PureLiFi says it was “created to provide a platform for pilot projects”.
The second product, the Li-Flame, is described as the next-generation device with a 10Mbps downlink and a 10Mbps uplink over three metres. It, too, consists of separate ceiling and desktop units and was demonstrated at the Mobile World Congress in Barcelona at the start of 2015.
When can I use it?
According to Deepok Solanki, the CEO of Velmenni, consumer Li-Fi should be available in three to four years. In London, in September 2015, Professor Haus demonstrated sending a video from a standard, off-the-shelf LED lamp to a solar cell connected to a laptop (bit.ly/demo387). Rather than use photodiodes as a receiver, Professor Haus believes using standard, off-the-shelf solar cells and solar panels could receive data at 50 Mbps and speed LiFi to market. He also showed that it could receive data outdoors, even in foggy conditions.
Is Li-Fi set to be lucrative?
Professor Haus is hoping it will boost Scotland’s economy. PureLiFi recently attracted £1.5m in funding from a group of investors led by London & Scottish Investment Partners, and it is currently worth £14m. The market could be worth as much as $9bn (around £6bn) by 2018.
Will it replace Wi-Fi?
It will be a while before it takes over from Wi-Fi, and it may never happen. Professor Haas says Li-Fi is intended to complement Wi-Fi, 4G and 3G rather than replace it, so it certainly won’t be the end of radio-wave data transmission. Even so, Prof Haas says that the more Li-Fi LEDs there are, the less need there will be for radio masts - the number of radio cellular base stations stands at 1.4 million.
HOW LI-FI CAN BE USED
Sport and entertainment
A new sports and entertainment complex is set to be opened by the Golden State Warriors basketball team in 2018. A deal with PureLiFi will see Li-Fi street lamps outside the arena transmitting data to people walking beneath them. A test is planned for the arena’s media room.
Cars
There is a possibility that cars fitted with LED headlamps and tail lights will be able to exchange data with each other using the visible light spectrum. Li-Fi could also be fitted in traffic lights for better traffic management.
Security
Since light is contained within rooms and fewer users can access a Li-Fi access point than a Wi-Fi hotspot, it’s suggested that Li-Fi is perfect for use in meeting rooms and situations where confidential information is handled, such as hospitals.