Li-Fi is a technology that uses light from LED bulbs to transmit data wirelessly. It works by varying the intensity of light faster than the human eye can detect, allowing binary data to be encoded and transmitted similar to Wi-Fi but using visible light instead of radio waves. The technology was pioneered in the 1990s but recent demonstrations have achieved speeds over 100Mbps. Potential applications of Li-Fi include use in traffic lights, airplanes, underwater and public internet hotspots provided through street lamps. However, challenges include light not passing through solid objects and interference from other light sources.

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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.

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WHAT IS LI – FI ?
• LI-FI is transmission of data through
illumination ,ie sending data through a LED
light bulb that varies in intensity faster than
human eye can follow
• LI FI- LIGHT FIDEALITY

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HISTORY-
The technology truly began
during the 1990's in countries
like Germany, Korea, and
Japan where they discovered
LED's could be retrofitted to
send information. Harald
Haas continues to wow the
world with the potential to
use light for communication
HARALD HASS

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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 TEDGlobal, Haas demonstrated a data rate of
transmission of around 10Mbps -- comparable to a fairly good
UK broadband connection. Two months later he achieved
123Mbps.
Back in 2011 German scientists succeeded in creating
an800Mbps (Megabits per second) capable wireless network
by using nothing more than normal red, blue, green and yellw
0

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PRESENT SCENARIO
1.4 Million 5 Billion
Radio Spectrum is congested but the demand for
wireless data double each year .Every thing, it seems
want to use wireless data but the capacity is drying
up.

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Radio
Waves
Infrared
Rays
Visible
Rays
Ultraviolet
Rays
X- Rays
Gama
Rays
 Gama rays cant be used as they could be
dangerous.
X-rays have similar health issues.
Ultraviolet light is good for place without
people, but other wise dangerous for the
human body.
Infrared, due to eye safety regulation, can
only bse used with low power.

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LED ie Light emitting diode can be switched on and
off faster since operating speed of LED is less than 1
μs, than the human eye can detect, causing the light
source to be appear continuously. This invisible on-
off activity enables a kind of data transmission using
binary codes. Switching on and LED is a logical ‘1’,
switching it off is a logical ‘0’.It is possible to
encode data in the light by varying the rate at which
LED’s flicker on and off to give different strings of
1s and 0s. Modulation is so fast that human eye
doesn’t notice

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How LI-FI Works ?
operational procedure is very simple, if the led is on, you
transmit a digital 1, if its 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 us
required is some LEDS and a controller that code data into
those LEDs. We have to just vary the rate at which the LED’s
flicker depending upon the data we want to encode
Thus every light source will
works as a hub for data
transmission

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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 high-
definition film in just 30 seconds

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For giga-speed technologies, the Li-Fi Consortium defined
GigaShower, GigaSpot and GigaMIMO models

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GigaShower and Giga-MIMO are the other models for in-
house communication. There a transmitter or receiver is
mounted into the ceiling connected to, for example, a
media server
GigaShower provides unidirectional data services via several
channels to multiple users with gigabit-class com-munication
speed over several metres. This is like watching TV channels
or listening to different radio stations where no uplink
channel is needed. In case GigaShower is used to sell books,
music or movies, the connected media server can be accessed
via Wi-Fi to process payment via a mobile device. GigaSpot
and GigaMIMO are optical wireless single- and multi-channel
HotSpot solutions offering bidirectional gigabit-class
communication in a room, hall or shopping mall for example.

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LI FI CONSTRUCTION-
The LI FI product consists of 4 primary sub-assemblies:
• Bulb
• RF power amplifier circuit (PA)
• Printed circuit board (PCB)
• Enclosure
3-The PCB controls the electrical inputs and outputs of the lamp and
houses the microcontroller used to manage different lamp functions.
2- An RF (radio-frequency) signal is generated by the solid-state PA and
is guided into an electric field about the bulb. The high concentration of
energy in the electric field vaporizes the contents of the bulb to a plasma
state at the bulb’s center; this controlled pasma generates an intense
source of light. All of these subassemblies are contained in an aluminum
enclosure.

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POTENTIAL APPLICATION OF LI-FI
Li Fi technology is still in its infancy .However some areas
where it seems perfectly applicable are:-
1- TRAFFIC LIGHTS
 Traffic lights can communicate to the car and
with each other. Cars have LED-based headlights,
LED-based cack lights, and cars can
communicate with each other and prevent
accidents in by exchanging information.

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2-INTRINSICALLY SAFE
ENVIRONMENT
Visible Light is more safe than RF, hence it can
be used in places where RF can't be used such as
petrochemical plants .


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3- Airlines
Whenever we travel through airways we face the problem in
communication media ,because the whole airways communication
are performed on the basis of radio waves. To overcomes this
drawback on radioways , li-fi is introduced.

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4- ON OCEAN BEDS
Li-Fi can even wok underwater were Wi-Fi fails
completely, thereby throwing open endless
opportunities for military/navigation operations.

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There are millions of street lamps deployed around
the world.
Each of these street lamps could be a free access
point.
 PUBLIC INTERNET HOTSPOTS

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It will reduce your electricity bill
and maintainance bill

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Limitations 0r challenges-
# light can't pass through objects
#. Interferences from external light sources like sun
light, normal bulbs, and opaque materials in the path
of transmission will cause interruption in the
communication.
#High installation cost of the VLC systems
#A major challenge facing Li-Fi is how the receiving
device will transmit back to transmitter.

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CONCLUSION
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 hotspots to
transmit wireless data.

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REFRENCES
1..http://www.electronicsforu.com/electronicsforu/ci
rcuitarchives/view_article.asp?sno=778&title%20=
%20Li-
Fi%3A+A+New+Paradigm+in+Wireless+Communi
cation&b_type=new&id=12042
2. http://en.wikipedia.org/wiki/Li-Fi
3. International Journal of advances in computing
& communications, vol 1, 2013,page no-12
www.ijacc.org

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