While Wi-Fi uses radio waves, Light Fidelity (Li-Fi) employs modulated visible light from a light-emitting diode (LED) to transmit data. Li-Fi technology was originated in 2011 by Professor Harald Haas of the University of Edinburgh who coined the term Li-Fi during a TED Talk in 2011. Haas pointed out that since the visible light spectrum is 1,000 times larger than the entire 300 GHz of radio, microwave and mm wave radio spectrum, there is a big untapped reservoir of resources for wireless systems.
With light there is no concern about being limited to a set of radio frequencies. Li-Fi works by taking advantage of the characteristics of an LED. Basically, when a constant current is applied to an LED light bulb a constant stream of photons are emitted from the bulb which is observed as visible light. But because an LED light bulb is a semiconductor light source, the constant current of electricity supplied can be adjusted up and down and at extremely high speeds. Indeed, by affixing a microchip to a LED light bulb it can be made to flicker millions of times a second, a bit like high-tech morse code, and at a rate so fast that it is not visible to the human eye.
Fig. 1: Li-Fi combines two essential functions--illumination and communications—a cost-saving measure that makes more efficient use of existing infrastructure. (Source: PureLiFi)
While Li-Fi is clearly faster than traditional Wi-Fi, there have been widely published reports on the Web that it is “100x faster than Wi-Fi.” Not so. The latest Wi-Fi standard (IEEE 802.11ad--otherwise known as Wi-Gig) operating in the 60 GHz frequency band supports data rates of 7 Gbps. For Li-Fi to be 100 times faster it would have to achieve 700 Gbps and that has not been achieved. The type of light source (large LED, small LED or laser) directly impacts the speed that can be achieved by a Li-Fi solution. Phosphor- coated white LEDs, which are mostly used in all commercial lighting devices, can deliver about 100 Mbps and the more expensive red, green, blue (RGB) LEDs can deliver anywhere from 3 to 5 Gbps. Note that this is still fast enough for a typical HD movie to be downloaded in seconds.
Wi-Fi does have its advantages. By using radio waves Wi-Fi signals can pass through walls and ceilings. Li-Fi signals cannot pass through walls; in order to enjoy connectivity in each room at home, Wi-Fi capable LED bulbs will need to be placed throughout the house. On the other hand, an intruder or hacker, positioned outside of a building can still tap into Wi-Fi data communications that leak from inside the building. Data communicated via Li-Fi is inherently more secure in that it can only be accessed where there is LED illumination. Put another way the would-be hacker would have to be in the same room with you to tap into the network.
One disadvantage of traditional Wi-Fi routers is that multiple devices in a room can interfere with each other. But there can be tens or more Li-Fi light bulbs in a room without interference. Wi-Fi also creates Electromagnetic Interference (EMI), known to interfere with airplane instruments and equipment in hospitals. Li-Fi uses light instead of radio waves and does not create EMI.
Fig. 2: LiFi-X, the world's first Li-Fi dongle, was introduced at Mobile World Congress 2016.
pureLiFi, and Lucibel, a French company that specializes in the design of new-generation lighting solutions based on the LED technology, are in the process of co-developing and marketing Europe’s first, fully industrialized Li-Fi luminaire. The first installation of this Li-Fi luminaire will be at the Sogeprom’s headquarters in the La Defense section of Paris. Sogeprom, a subsidiary of Societe Generale and a major property developer, is looking at Li-Fi to provide the next generation of wireless connectivity for its customers.
