Li-Fi is a technology that uses light from LED bulbs to transmit data wirelessly. It was invented by Professor Harald Haas in 2011 as an alternative to Wi-Fi that uses radio waves. Li-Fi works by varying the intensity of light from an LED bulb faster than the human eye can detect to transmit digital signals. It has applications in traffic lights, underwater communication, and street lamps that can each act as access points. Potential limitations include interruptions from external light sources and higher installation costs compared to Wi-Fi.

1. LI-FI (LIGHT FIDILITY)
TECHNOLOGY
PRESENTED BY:
G . Prasanna

2.  What is li-fi?
 Genesis
 Introduction
 Components
 Construction
 Working
 Applications
 Limitations
 References
INDEX

3. Li-fi is transmission of data
through illumination I e ,
sending data through a LED light
bulb that varies in intensity
faster than human eye can flow
WHAT IS LI-FI ?

4. GENESIS
 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.

5.  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.

6. GENESIS OF LI-FI
HARALD HAAS

7. INTRODUCTION
Present scenario
1.5 million 5 billion (600TB)

8. ISSUES REGARDING
RADIO WAVES
Efficiency
Availability
Security
Capacity

12.  Li-Fi can be thought of as a light-based Wi-Fi.
 Uses light instead of radio waves to transmit
information.
 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.

13.  This technology uses a part of the electromagnetic
spectrum.
 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.

14.  It mainly focus 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.

15. COMPONENTS
RECEIVING
ELEMENT
TRANSMITTING
ELEMENT

16. Li-fi consists of 4 primary sub-assemblies:
1. Bulb
2. Radio frequency(RF)
power amplifier circuit(PA)
3. Printed circuit board(PCB)
4. Enclosure
CONSTRUCTION

17.  PCB controls the electric inputs and outputs of
the lamp
 an RF 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 vaporise the contents of the bulb
to a plasma state at the bulb's center ; this
controlled plasma generates an intense source
of light. All of these sub assemblies are
contained in an aluminium enclosure

18.  In bulb assembly a sealed bulb is embeded
in a di electric material it is used as an
electric field concentrator that focuses
energy in the bulb. The energy from E.F
rapidly heats the material in the bulb to a
plasma state that emits light of high
intensity and full spectrum.

20.  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.
WORKING

21.  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.

22.  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.

24.  To further get a grasp of Li-Fi consider an IR remote.
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 is capable of sending thousands of such
streams at very fast rate.

26. Traffic lights can communicate to the car and with each other.
Cars have LED based headlights and cars can communicate with
each other and prevent accidents in by exchanging information.
APPLICATIONS

27. Whenever we travel through airways we face the problem
in communication media because the whole air ways
communication are performed on the basis of radio waves
to overcome this drawback on radio waves li-fi is
introduced.

28. Li-fi can even work under water where Wi –fi falls
completely there by throwing endless opportunities for
military.

29. There are millions of street lamps around the world.
Each of the street lamp can be free access point.

30. 1. Light can pass through objects.
2. Interferences from external light source like sun
light, normal bulbs and opaque materials in the
path of transmission will cause interruption in the
communication.
3. High installation cost of VLC systems.
LIMITATIONS

31. [1] http://www.slideshare.net/tanshu9871/ppt-on-
lifi-technology
[2]http://www.seminarsonly.com/computer%20scien
ce/Li-Fi-Technology .php
[3] http://www.collegelib.com/t-li-fi-technology-
seminar-report-abstract.html
REFERENCES