Li-Fi is a wireless optical networking technology that uses light-emitting diodes (LEDs) for data transmission. It provides higher speeds and more bandwidth than Wi-Fi. Li-Fi works by switching LEDs on and off faster than the human eye can detect, allowing them to transmit digital signals. It has several advantages over Wi-Fi including increased speed and bandwidth availability, lower energy use, and improved security since light does not pass through walls. Potential applications of Li-Fi include use in hospitals, aircraft, traffic lights, and street lamps to provide wireless internet access.

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LIGHT FIDELITY
By Sanu Thomas V

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INTRODUCTION TO LI-FI
LI-FI IS A TECHNOLOGY THAT USES THE LIGHT
EMITTING DIODES TO TRANSMIT THE DATA
WIRELESSLY.
LI-FI IS FAST AND CHEAP OPTICAL VERSION OF WI-FI
,BASED ON VISIBLE LIGHT COMMUNICATION(VLC).
VLC IS A DATA COMMUNICATION MEDIUM,WHICH
USES THE VISIBLE LIGHT BETWEEN 400 THz (780 nm)
and 800 THz (375 nm) AS OPTICAL CARRIER FOR
DATA TRANSMISSION

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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
HE DEMONSTRATED IT IN THE
YEAR 2012.
HARALD HASS

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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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OVERCOMING THE FOUR ISSUES
WITH RW IN LI-FI
1. CAPACITY
• 10000 TIMES MORE SPECTRUM THAN RW.
LIGHT BOXES ARE ALREADY PRESENT, SO
INFRASTRUCTURE IS AVAILABLE ALREADY
AND INSTALLED.
2. EFFICIENCY
• HIGHLY EFFICIENT BECAUSE LED CONSUMES
LESS ENERGY.

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3. AVAILABLITY
• LIGHT IS PRESENT EVERYWHERE.
• DATA IS PRESENT WHERE LIGHT IS PRESENT.
4. SECURITY
• LIGHT WAVES DOESNOT PENETRATE
THROUGH WALLS.
• HENCE THEY CAN’T BE INTERCEPTED.

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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.
HENCE WE LEFT WITH THE ONLY THE VISIBLE -
LIGHT SPECTRUM.

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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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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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ADVANTAGES OF LI-FI
• YOU CAN USE LI-FI IN HOSPITALS AND
AIRCRFTS ALSO.
• CHEAPER THEN WIFI , SINCE VISIBLE LIGHT
SPECTRUM IS A FREE SPECTRUM BAND.
• NO LICENSE NEEDED.
• THOUSANDS AND MILLIONS OF STREET
LAMPS CAN BE COVERTED TO LI-FI SPOTS.

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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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