Li-Fi is the term nowadays used to label the fast and cheap wireless-communication system and is the proposed optical version of Wi-Fi. Li-Fi is a term often used to describe Visible Light Communications technology applied to high speed wireless communications. LiFi is transmission of data through illumination by taking the fiber out of fiber optics by sending data through a LED light bulb that varies in intensity. This technology uses visible spectrum of light, a part of the electromagnetic spectrum. In fact the technology transfers thousands of streams of data simultaneously, in parallel, in higher speeds. In simple terms, Li-Fi can be thought of as a light-based Wi-Fi. That is, it uses light instead of radio waves to transmit information using transceiver-fitted LED lamps. Interestingly, Li-Fi could transform the everyday LED lighting fixtures into 10 Gbps wireless modems .
KEYWORDS You Must Know
LiFi (Light Fidelity), WiFi (Wireless Fidelity), VLC (Visible Light Communication), LED (Light Emitting Diode), IEEE (Institute of Electrical and Electronics Engineers), RF (Radio Frequency).
The Information Age, also commonly known as the Computer Age or Digital Age, is a period in human history characterized by the shift from traditional industry to an economy based on the information computerization. The onset of the Information Age
is associated with the Digital Revolution. Today, the Internet is far from obscure—it is the center of attention and has spawned industries to emerge as a global cultural phenomenon.
Consumer use of the Internet first became popular through dial-up Internet access in the 1980s and 1990s. By the first decade of the 21st century, many consumers used faster, broadband Internet access technologies.
Taking a closer look at the boom of the Internet and the upcoming of the wireless technology in action in 1990s, Wi-Fi was invented with speeds of 1Mbps/2Mbps in designing standards such as IEEE 802.11b, 802.11a and 802.11g.Wi-Fi is a popular technology that allows an electronic device to exchange data wirelessly (using radio waves) over a computer network based on the IEEE 802.11 standards. WiFi uses the unlicensed 2.4GHz spectrum, which often crowded with other devices, may cause degradation in performance. Inter-operability issues can cause limited connection or lower output speeds.WiFi networks have limited range.
In the near future, the wireless technology is being replaced by a drift from WiFi to LiFi technologies due to the disadvantages offered by WiFi over the innumerable advantages proposed by LiFi. While WiFi is predicated on the availability of a microwave signal, LiFi can hypothetically turn any lamp into a network connection operating at much higher frequencies. LiFi also offers more privacy than WiFi.
WHY SWITCH TECHNOLOGY?
Radio spectrum is congested but the demand for wireless data doubles each year with everything desiring for wireless data but the capacity is drying up. Wireless radio frequencies are getting higher, complexities are growing and RF interference continues to grow. So, to carry this excess demand in the future, the solution is Li-Fi. Direct modulation of LED devices is a low cost, secure, and safe way to transmit data, and there is an abundance of free visible light spectrum. High intensity LEDs used in light bulbs, flash lights and cameras can transmit very high data rates, even faster than Wi-Fi!
Besides, Wifi has some drawbacks- it uses microwaves at low intensity which can generate perturbations to medical devices and is often not secure.Its bandwidth decreases dramatically with the distance from the antenna.
For such reasons, Wifi is not very well accepted in healthcare centers .
Lifi, the wireless communication based on infrared light is perhaps the solution as it uses infrared light at very low intensity which is proved to be harmless. It is directional and does not cross the wall which increases the level of security. It does not generate perturbations to most of medical devices since; its bandwidth is very large because of light wavelength.
HISTORY/GENESIS OF Li-Fi
Li-Fi is a label for wireless-communication systems using light as a carrier instead of traditional radio frequencies. The term was first used in this context by Harald Haas in his TED Global talk on Visible Light Communication.
Harald Haas, a professor at the University of Edinburgh who began his research in this field in 2004, gave a debut demonstration of what he called a Li-Fi prototype at the TEDGlobal conference in Edinburgh on 12th July 2011. He used a table lamp with an LED bulb to transmit a video of blooming flowers that was then projected onto a screen. During the event he periodically blocked the light from lamp to prove that the lamp was indeed the source of incoming data. He demonstrated a data rate of transmission of around 10Mbps. Two months later he achieved 123Mbps.
In October 2011, a number of companies and industry groups formed the Li-Fi Consortium, to promote high-speed optical wireless systems and overcome the limited amount of radio-based wireless spectrum available by exploiting a completely different part of the electromagnetic spectrum.
The technology was demonstrated at the 2012 Consumer Electronics Show in Las Vegas using a pair of Casio smartphones to exchange data using light of varying intensity given off from the screens, detectable at a distance of up to ten meters .
Li-Fi has the advantage of being able to be used in sensitive areas such as in aircraft without causing interference.
Later in 2012, PureVLC, a firm was set up to commercialize Li-Fi and to bring about Li-Fi products for firms installing LED-lighting systems.
Li-Fi is a VLC, visible light communication, technology developed by a team of scientists including Dr. Gordon Povey, Prof. Harald Haas and Dr. Mostafa Afgani at the University of Edinburgh.
Li-Fi is now part of the Visible Light Communications (VLC) PAN IEEE 802.15.7 standard. Li-Fi is typically implemented using white LED light bulbs normally used for illumination by applying a constant current through the LED resulting in “Data through Illumination” producing data rates faster than 10 Mbps, which is speedier than our average broadband connection.
IMPLEMENTING THE NOTION
Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter normally used for illumination only by applying a constant current. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds. The LED light bulb is a semi-conductor device. It can blink rapidly to develop binary signals. The light intensity can be manipulated to send data by tiny changes in amplitude. The twin benefit is that the LEDs also provide light as any incandescent bulb. This very property of optical current is used in Li-Fi setup .
The operational procedure is very simple- LED lights flicker on and off thousands of times a second and by altering the length of the flickers we can introduce digital communications. If the LED is on, a digital 1 is transmitted and if it is off a 0 is transmitted. Hence all that is required is some LEDs and a controller that code data into those LEDs and vary the rate at which the LED’s flicker depending upon the data to be encoded . It is possible to encode data in the light by varying the rate at which the LEDs flicker on and off to give different strings of 1s and 0s. The LED intensity is modulated so rapidly that human eyes cannot notice, so the output appears constant .
A new step in the manufacture of this new type of network has been reached by recent research from the University of Strathclyde in Scotland. Professor Martin Dawson and his teams have miniaturized LEDs to a size of 1 mm ² . Thus, these micro LEDs can be more easily integrated into everyday devices.
These smaller micron-sized LEDs are able to flicker on and off around 1,000 times quicker than the larger LEDs. This offers faster data transfers and they also take up less space. Each micron-sized LED would also act as a tiny pixel. This means one large LED array display – such as one that might be used to light a living room or the interior of an aircraft – could also be used as a screen displaying information, at exactly the same time as providing internet communications and lighting.
Further enhancements can be made in this method, like using an array of LEDs for parallel data transmission, or using mixtures of red, green and blue LEDs to alter the light’s frequency with each frequency encoding a different data channel.BREAKTHROUGH FOR Li-Fi
The technology is capable of transferring thousands of streams of data simultaneously, in parallel, at higher speeds, with the help of special modulation, using a unique signal processing technology.
First applications of Li-Fi have been put to use already, for example, in hospitals where RF signals are a threat due to interference problems with medical equipment such as blood pumps and other life supporting instruments since; light is inherently safe and can be used in places where radio frequency communication is often deemed problematic.
In 2011, the “Fraunhofer Institute of Telecommunications” (Heinrich Hertz Institute) succeeded in achieving a data flow rate of 800 Mbps by the use of conventional LED red, blue, green and white.
Another advantage is this LED light bulb can be dimmed to a minimum luminosity so as to transmit the data. LED light bulbs are highly energy efficient, thereby cutting costs. The system can be fitted into and run on the existing infrastructure available for the lighting up the place. The LED bulb will hold a micro-chip that will do the job of processing the data.
Once established, VLC could solve some major communication problems. In 2009, the US Federal Communications Commission warned of a looming spectrum crisis: because our mobile devices are so data-hungry we will soon run out of radio-frequency bandwidth. Li-Fi could free up bandwidth, especially as much of the infrastructure is already in place.
“There are around 14 billion light bulbs worldwide, they just need to be replaced with LED ones that transmit data,” says Haas. These 14 billion lamps in the world will become gradually green mobile internet masts that will permit to respond to the impressive increasing demand of mobile connectivity. Also, this will allow reducing the electromagnetic pollution generated by the numerous radio wave solutions developed until now.
VLC could be used safely in aircraft, integrated into medical devices and hospitals, or even underwater
CHALLENGES FOR Li-Fi
Since LiFi requires line-of-sight, when set up outdoors the apparatus would need to deal with ever changing conditions. Indoors, one would not be able to shift the stationery receiving device. A major challenge facing LiFi is how the receiving device will transmit back to the transmitter .
On the other hand light does have a few other obvious drawbacks as visible light cannot penetrate through most walls and is easily blocked by somebody simply walking in front of the LED source.
APPLICATIONS OF Li-Fi TECHNOLOGY 
- Integrated into medical devices and in hospitals as it can easily be used in such places where Bluetooth, infrared, Wi-Fi and internet are banned.
- Under water in sea where Wi-Fi does not work at all.
- In aircraft, the overhead lights can be used for data transmission. It can be used in petroleum or chemical plants where other transmission or frequencies could be hazardous.
- There are around 14 billion bulbs worldwide, they just need to be replaced with LED ones that transmit data as we reckon VLC at a factor of ten, cheaper than WI-FI.
- In streets for traffic control. Cars have LED based headlights, LED based backlights, and Cars can communicate with each other and prevent accidents in the way that they exchange such information. Traffic light can communicate to the cars and so on.
- By implementing this technology worldwide every street lamp would be a free access point.
- Li-Fi may solve issues such as the shortage of radio frequency bandwidth.
Imagine ourselves walking into a mall where GPS signals are unavailable but the mall is equipped with ceiling bulbs that create their own ‘constellation’ of navigation beacons. As the camera of our cell phone automatically receives these signals, it switches our navigation software to use this information to guide us to the nearest spot we are searching for .
This can be considered as one such scenario where our emerging wireless technology can be put to use.
ADVANTAGES OF Li-Fi OVER Wi-Fi
There are myriad advantages that LiFi has over WiFi .
- While WiFi is predicated on the availability of a microwave signal, LiFi can hypothetically turn any lamp into a network connection. LiFi operates at frequencies much higher than WiFi.
- One of the biggest advantages of LiFi is that it can be used in areas with a lot of RF noise or where RF noise is prohibited, such as hospitals and airplanes.
- LiFi also offers more privacy and security than WiFi because the signal is easily obscured by opaque materials and light does not penetrate through walls.
- LiFi can be used in places where it is difficult to lay optical fibres as in operation theatres.
- Li-Fi has high speeds, provides communications as high as 500 Mbps or 30 GB per minute, so it can easily be used in such places where Bluetooth, infrared, Wi-Fi and internet are banned. In this way, it will be the most helpful transferring medium.
- Li-Fi is a free band that does not need licence. Hence it is cheaper than Wi-Fi.
The world of lighting companies experiences a true revolution with the development of LED lighting devices with reduced energy consumption and a longer lifetime .
Wi-Fi is great for general wireless coverage within buildings and LI-FI is ideal for high density wireless data coverage in confined area and for relieving radio interference issues, so the two technologies can be considered complimentary.
With so many feathers in its cap, Li-Fi has one natural shortcoming. Since light cannot penetrate opaque obstacles, this can prove to be an obvious limitation to the technology’s usage. Nevertheless, given the terrific data rates and use in multiple fields Li-Fi is definitely the road ahead in wireless communication.
The possibilities are numerous and can be explored further. If this technology can be put into practical use, every bulb can be used something like a Wi-Fi hotspot to transmit wireless data and we will proceed toward the cleaner, greener, safer and brighter future. The concept of Li-Fi is currently attracting a great deal of interest, since with this enhanced technology, a growing number of people and their many devices access wireless internet, on one way, transmit data at higher rates and on the other it is very cheap as compared with Wi-Fi .
Professor Martin Dawson, Strathclyde University, explained:
“Imagine a LED array beside a motorway helping to light the road, displaying the latest traffic updates and transmitting internet information wirelessly to passengers’ laptops, notebooks and smartphones. This is the kind of extraordinary, energy-saving parallelism that is believed to be delivered by this pioneering technology.”
 Prof. (Dr.) Y.P. Singh, “A Comparative and Critical technical Study of the Li-Fi – (A Future Communication) V/S Wi-Fi,” International Journal of IT, Engineering and Applied Sciences Research (IJIEASR) ISSN: 2319-4413, Vol. 2, No. 4, April 2013.
 Priyanka Dixit and Kunal Lala– LI-FI the Latest Technology in Wireless; ISBN: 9788175157538.