Introduction and VLC
By 2020, Wi-Fi will connect 1.7 billion devices, according to Cisco. However, by 2025 the growth of wireless data traffic could mean that the radio frequency (RF) spectrum Wi-Fi occupies will not be able to cope with demand. Cue Li-Fi, which uses part of the visible light portion of the electromagnetic spectrum to transmit information at very high speeds. Could Li-Fi takeover from Wi-Fi?
How does it work?
While a Wi-Fi network makes use of radio waves to transmit information across a network, light fidelity – aka Li-Fi – transfers data through light waves. "The concept of Li-Fi came about after an Estonian company called Velmenni conducted a real-world test in which it was able to transfer data at 1Gbps, which is approximately 100 times faster than Wi-Fi," says Albie Attias, managing director of IT hardware reseller King of Servers.
"Similar to the infrared technology found in TVs, Li-Fi works by turning an input command into binary code, which is then transmitted through infrared light waves by the remote's sensor," adds Attias. "The light waves are then decoded and perform the intended action."
Li-Fi tech could be used in cars, planes, solar panels, around schools and lecture theatres, during disasters, on oil rigs and in nuclear power stations, around hospitals, or in homes and workplaces.
What is VLC?
The technology behind Li-Fi is called Visible Light Communication (VLC), and it's akin to Morse code. "It works by controlling the number of photons emitted by LEDs and doing this in a manner that is not detectable by humans even though it uses the visible light spectrum," says Andrew Ferguson, editor of thinkbroadband.com. "Li-Fi is the named adopted for the transmission of data using visible light and thus reflects the shift from the radio frequencies of Wi-Fi – i.e. 2.4GHz and 5GHz – to the visible light spectrum of 430 to 770THz." This carries the potential for very high transmission rates.
Here's one scenario that could make Li-Fi genuinely useful: you want to sync your laptop with a cloud server to download a lot of data – or you want to download a 4K movie to your tablet – so you hold the device in sight of the Li-Fi-enabled light bulb in your living room… for just a couple of seconds.
What would a Li-Fi network look like?
Light bulbs. That's it. Rapid changes in light levels – not visible to the eye – are what transmits the data. "The latest innovation is totally wireless, and can operate with existing LED bulb technology," says Attias, who states that to go mobile, Li-Fi would require smartphones and laptops to be fitted with a photosensor to read incoming light. It could happen to the iPhone. While the Li-Fi industry waits for phone-photosensors, a company called Zero. 1 is using the front and rear cameras on smartphones in a Dubai-based Li-Fi test project at Dubai Silicon Oasis.
Who is promoting Li-Fi?
Li-Fi's biggest advocate is Harold Haas, a professor at the University of Edinburgh who gave a TED talk on Li-Fi, which included a demo, in 2011, then founded pureLi-Fi. The first Li-Fi-enabled light bulb, created by pureLi-Fi and LED maker Lucibel, is expected towards the end of 2016.
Dozens of other companies are involved in Li-Fi research, including Lucibel, Oledcomm, LG, Philips, Samsung, Toshiba, Sharp, Panasonic, Cisco and Rolls Royce, while there are various independent Li-Fi projects, too.
Li-Fi limitations and cost
One of the main limitations of Li-Fi is the need for a line-of-sight link; the device needs to 'see' the light source, which makes it unsuitable for use in smart cities, or over large networks where buildings or other objects could get in the way.
"Its main physical limitation is that visible light is used, so requires photons to be emitted and detected, thus a mobile that is in a shadow may not work," says Ferguson. Li-Fi signals can also be interrupted by bright sunlight, which again makes it less than reliable outdoors. "It can't be used in direct sunlight, or in other conditions with harsh lighting, as the photodetectors will not be able to detect the modulating light waves," adds Attias, who thinks that Li-Fi would require much investment in lighting and wiring infrastructure.
The one-way link
Unlike the IP integration that Wi-Fi creates, Li-Fi's physical limitations mean that it's primarily seen as ideal only for making a one-way data dump, and not as a means of communication. "Li-Fi is generally conceived as a one-way content delivery mechanism, and IP requires two-way communication," says Ferguson.
However, this could mean a hybrid Wi-Li-Fi future is possible. "Utilising Wi-Fi as the upstream from a device may make this less of a problem," adds Ferguson, suggesting that it's much like early satellite broadband that relied on a dial-up connection to send the acknowledgments for receiving data packets.
Could Li-Fi prove expensive?
"Many of the mathematical techniques are similar to those used in existing Wi-Fi systems, but cost will ultimately depend on the volume of sales," says Ferguson, who points out that when it first appeared, Wi-Fi was very expensive. Even now, top-of-the-range 802.11ac Wi-Fi routers are still much more expensive than basic models.
"To keep costs reasonable, it's possible that the first commercial versions of Li-Fi may be a lot slower than the lab demonstrations seen so far," adds Ferguson.
While Li-Fi sits in research labs, Wi-Fi is booming. Capacity problems may loom in the middle-distance, but with the explosion of the IoT, Wi-Fi is doing very nicely. The industry surpassed 10 billion Wi-Fi-enabled devices shipped cumulatively in early 2015, according to ABI Research – over half were dual-band (2.4GHz and 5GHz) – and Wi-Fi gadgets are expected to boom over the next five years thanks to cars and a massive increase in people getting online. Meanwhile, there are other variants of Wi-Fi such as HaLow, WeGig and LTE-U.
Where next for Li-Fi?
So will there be enough room for Li-Fi to see the light? Probably, but it could be a niche product at first. "So far a lot of the chatter is around the technology replacing techniques such as Bluetooth-enabled advertising displays," says Ferguson, but there's a more general advantage in homes, too. "One of the biggest advantages of Li-Fi as a concept is its potential to eradicate congested radio waves and wireless dead zones," says Attias, who thinks it could catch-on where Wi-Fi is restricted.
"Although it will be a considerable amount of time until Li-Fi comes to the forefront, there is a great deal of potential for it to be used on aircrafts and in hospitals," says Attias on what could very well be Li-Fi's 'killer app'. That reading lamp above airline seats could yet prove the death of inflight entertainment – and the birth of a new light-powered internet.