Li-Fi, an emerging technology which uses the visible light spectrum (VLS) to transmit wireless data, has passed the proof-of-concept stage and the first commercial applications are coming to market.
The term Li-Fi is short for light fidelity and is a play on words derived from wireless fidelity or Wi-Fi. It was first used by Edinburgh University professor of mobile communications Harald Hass in a 2011 presentation on visible light communications (VLC), and since then has quickly become part of the vernacular.
Like Wi-Fi, Li-Fi is a means of bidirectional, short-range wireless communication and it is expected to complement RF communications by taking some of the strain off stretched radio spectrum resources, particularly in the unlicensed 2.4 GHz and 5 GHz bands used by Wi-Fi and Bluetooth.
Because it operates in the visible light spectrum, which is at a far higher frequency in the overall electromagnetic spectrum range than RF, there are no spectrum constraints. The VLS is in the upper reaches of the 300 TeraHertz (THz) band and is about 10,000 times larger than the radio part of the electromagnetic spectrum which ends at around 300 GHz. (1THz = 1000 GHz).
Li-Fi development around the world has concentrated on using light-emitting diode (LED) light sources to carry data traffic. Pioneering developers such as pureLiFi, a company spun off from Edinburgh University by Prof Hass to commercialise research work, have concentrated on two-in-one lighting and wireless communications systems where the Li-Fi access point is built into the lighting unit. Ultimately the researchers see large-scale collaboration between wireless service providers and lighting utilities.
The first product became available early in 2014, the Li-1st, to provide two-way communications at 5 MBps at a range of three metres from the LED bulb. The equipment is simple plug-and-play and provides secure wireless point-to-point Internet access. More sophisticated network products, with users able to move seamlessly between multiple access points, followed during the course of the year. And under development is a new LED bulb which will provide a data rate of 4 GGps at a range of up to 10 metres.
One of the constraints with Li-Fi is that it cannot penetrate walls, as Wi-Fi is able to, although line-of-sight is not necessary as it can bounce off walls. This has been addressed by the members of the Li-Fi consortium whose founders are Germany’s research powerhouse the Fraunhofer Institute, Norway’s Ibsen Telecom and Supreme Architecture, a technology start-up with offices in Los Angeles and Tel Aviv.
The consortium has developed a Li-Fi room connector, a replicator which sends the data from connections on one side of the wall to the other via fibre-optic cable.
The ACEMIND research project, which has both commercial and academic members from Germany, France, Greece, the Czech Republic and Turkey, sees LI-Fi being of practical use in electromagnetically-sensitive areas such as hospitals, aircraft cabins and power plants and believes it will be key to the development of the Internet of Things (IoT).
The researchers believe Li-Fi will eventually result in a merger between the lighting industry and the wireless communications industry to create greater value for both, and predict within 25 years light bulbs will have the same processing power as smartphones today. We will just have to wait and see.