About Li-Fi

About Li-Fi
Li-Fi is a label for wireless-communication systems using light as a carrier instead of traditional radio frequencies, as in Wi-Fi.
Genesis of LI-FI:
Harald Haas, a professor at the University of Edinburgh who began his research in the field in 2004, gave a debut demonstration of
what he called a Li-Fi prototype at the TED Global 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 behind him. During the event he
periodically blocked the light from lamp to prove that the lamp was indeed the source of incoming data. At TED Global,
Haas demonstrated a data rate of transmission of around 10Mbps -- comparable to a fairly good UK broadband connection.
Two months later he achieved 123Mbps.
TED (Technology, Entertainment, Design) VLC (visible light communication)
About LiFi
LiFi is a new wireless communication technology which enables a wireless data transmission through LED
light. LiFi is based on a unique ability of solid state lighting systems to create a binary code of 1s and 0s
with a LED flickering that is invisible for human eyes. Data can be received by electronic devices with
photodiode within area of light visibility.
This means that everywhere where LEDs are used, lighting bulbs can bring not only the light but wireless
connection at the same time. With increasing demand for wireless data, lack of radio spectrum and issues
with hazardous electromagnetic pollution, LiFi appears as a new greener, healthier and cheaper alternative
to WiFi.
Moreover LiFi makes possible to have a wireless Internet in specific environments (hospitals, airplanes
etc.) where WiFi is not allowed due to interferences or security considerations.
How Li-Fi Works?
Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter. These devices are 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. This very property of optical current is used in Li-Fi setup. The operational
procedure is very simple-, if the LED is on, you transmit a digital 1, if it’s off you transmit a 0. The LEDs can be switched on
and off very quickly, which gives nice opportunities for transmitting data. Hence all that is required is some LEDs and a
controller that code data into those LEDs. All one has to do is to vary the rate at which the LED’s flicker depending upon the
data we want to encode. 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. Such advancements promise a theoretical speed of 10 Gbps – meaning one can download a full highdefinition film in just 30 seconds.
TTo further get a grasp of Li-Fi consider an IR remote.(fig 3.3).
It sends a single data stream of bits at the rate of 10,000-20,000 bps.
Now replace the IR LED with a Light Box containing a large LED array.
This system, fig 3.4, is capable of sending thousands of such streams at very fast rate.
Light is inherently safe and can be used in places where radio frequency communication is often deemed problematic, such as in
aircraft cabins or hospitals. So visible light communication not only has the potential to solve the problem of lack of spectrum
space, but can also enable novel application. The visible light spectrum is unused, it's not regulated, and can be used for
communication at very high speeds.
Introduction of Li-Fi Technology
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.
And instead of Wi-Fi modems, Li-Fi would use transceiver-fitted LED lamps that can light a room as well as transmit and receive
information. Since simple light bulbs are used, there can technically be any number of access points.
This technology uses a part of the electromagnetic spectrum that is still not greatly utilized- The Visible Spectrum. Light is in fact
very much part of our lives for millions and millions of years and does not have any major ill effect. Moreover there is 10,000
times more space available in this spectrum and just counting on the bulbs in use, it also multiplies to 10,000 times more
availability as an infrastructure, globally.
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.
More sophisticated techniques could dramatically increase VLC data rates. Teams at the University of Oxford and the University of
Edinburgh are focusing on parallel data transmission using arrays of LEDs, where each LED transmits a different data stream.
Other groups are using mixtures of red, green and blue LEDs to alter the light's frequency, with each frequency encoding a
different data channel.
Li-Fi, as it has been dubbed, has already achieved blisteringly high speeds in the lab. Researchers at the Heinrich Hertz Institute in
Berlin, Germany, have reached data rates of over 500 megabytes per second using a standard white-light LED. Haas has set up a
spin-off firm to sell a consumer VLC transmitter that is due for launch next year. It is capable of transmitting data at 100 MB/s faster than most UK broadband connections.
1 High speed, as high as 500mbps or 30GB per minute
2. Li- Fi uses light rather than radio frequency signals,
3. VLC could be used safely in aircraft,
4. Integrated into medical devices and in hospitals as this technology does not deal with radio waves, so it
can easily be used in such places where Bluetooth, infrared, Wi-Fi and internet are banned. In this way, it
will be most helpful transferring medium for us.
5. Under water in sea Wi-Fi does not work at.
6. There are around 19 billion bulbs worldwide, they just need to be replaced with LED ones that transmit
data. We reckon VLC is at a factor of ten, cheaper than WI-FI.
7. Security is another benefit, he points out, since light does not penetrate through walls.
8. In streets for traffic control. Cars have LED based headlights, LED based backlights, and Car can
communicate each other and prevent accidents in the way that they exchange Information. Traffic light can
communicate to the car and so on.
9. By implementing the Technology worldwide every street lamp would be a free access point.
10. Li-Fi may solve issues such as the shortage of radio frequency bandwidth.
The full-featured local Li-Fi cloud
- Local optical communication network
- with local data cloud structure and in house server/router
- including "on the move" data transfer at 100 Mbit/s
- including GigaSpeed datatransfer and reception up to10 Gbit/s
- including security features
- including energy saving/environmental features
- controlled, for example, by optical smart phone
- connects all office and entertainment equipment
- controls all data and entertainment equipment via smartphone
- displays all files on any screen (TV,PC, etc.)
- supports file access from any point + and via any device
- stores all data in one central server/computer
- supports data transfer and reception at 10 Gbit/s
- supports "on the move" data transfer at 100 Mbit/s
- monitors the entire optical network area
- detects motion in the entire optical network area if wanted
- controls all security features via smart phone
- controls lighting via smart phone
- supports control of heating
- supports control of any connected electrical equipment
- supports energy saving/environmental features via smart phone
- bridges disparate data formats
- connects your local cloud to external line (fiberoptic, GigE, ADSL, etc.)
5 Reasons to Promote Li-Fi
1. Distance - The sheer range of transmitting information could be worth the decrease in data speeds. The RONJA project in
the Czech Republic can transmit a 10 Mbit/s Ethernet-type link just under a mile. As developments of this aspect continue,
the range could be entirely up to the strength of the light which is emitting the information. Although the speeds are less
than what they are for gigabit Ethernet, the power of the beam can allow DVD-quality streaming of video to any location
connected to the Li-Fi device.
2. Cost - Instead of running close to a mile worth of cable, the LED-powered Li-Fi connection could be used to beam the
information directly to the destination. Using a point-to-point array, office buildings can stay connected to each other
without the use of additional cables being laid from one access point to another. The only problem the two buildings would
be faced with is obstruction by solid objects or dense weather patterns such as heavy fog or snow.
3. Traffic Updates - Could you imagine having a car that uses a GPS system that receives information from traffic lights
informing you of accidents and/or delays up ahead? There is a kind of system like that already in play for GPS navigational
systems, but the traffic lights could be updating drivers using basic information or streaming video directly from news
4. Game Consoles - An innovative idea would be to put sensors on a television in order to receive information from game
consoles. This would allow the unit to be place literally anywhere within the room as long as there is a direct line of sight to the
sensor. Could you imagine a game system like the Xbox using a Kinect and all of it being completely wireless except for the power
going into the unit? That will be tackled once wireless energy is perfected for practical home use.
5. Television Interaction - Instead of using apps or additional installations, you could theoretically hold your phone up as you sit
on the couch and have every piece of information regarding the show or movie you are currently watching sent to your display –
even recording directly to your mobile device. Of course, this may spawn some kind of copyright lawsuit because you are illegally
copying a movie or television show, but you still get the idea. There are a number of reasons why investing in Li-Fi technology can
have a great benefit to the future of wireless networking. Although there are a few aspects that need to be ironed out before it
can be introduced on a wide scale of practicality, the future looks to be very promising. Even if the technology was merely
developed as a small scale indoor application to “beam” information directly to a computer system without the use of Ethernet
cable being strewn about the floor, visible-light communications could set the benchmark higher for wireless transmissions.

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