Li-Fi is a wireless optical networking technology that uses light-emitting diodes (LEDs) for data transmission. It is a visible light communication system that is a supplement to RF communications. Li-Fi can transmit data at much higher speeds than Wi-Fi and has advantages in terms of security, availability, and efficiency. Li-Fi works by varying the intensity of light from an LED to transmit digital signals and can be used anywhere that visible light is already in use, such as in homes, offices, street lights, and traffic signals. While Li-Fi has been demonstrated and is being implemented in some places, it also faces limitations around line of sight transmission and interference from other light sources.

1. Li-FiLi-Fi
Light FidelityLight Fidelity
Post WiFi technology using Visual Light
Communication
SRUJAN A,
BT10CSE004

2. What is Li Fi?
● LiFi is an alternative to WiFi that transmits data using
Visible Light Communication rather instead of radio
frequency waves.
● It is a complement of RF Communication and it solves
RF Bandwith limitations.
● In Layman's terms,Li-Fi is transmitting data using actual
light bulbs. We can use internet on our device just when
the light bulb in our room is switched on.

3. Life of Li Fi
● Professor Harald Haas coined the term Li Fi and is the founder
of this technology, in 2011 TED global talk.
● The promotion of idea through TED helped to start a company
pureLiFi.
● PureLiFi, formerly pureVLC, is an original equipment
manufacturer firm set up to commercialize Li-Fi products for
integration with existing LED-lighting systems.
● In Oct'11, few companies and industry groups formed Li-Fi
Consortium to promote this high-speed optical wireless
systems.
● LiFi is verified experimentally and also is used in few places
already.

4. LiFi vs WiFi
● Both Wi-Fi and Li-Fi transmit data over the electromagnetic
spectrum, but whereas Wi-Fi utilises radio waves, Li-Fi uses
visible light. This is a distinct advantage in that the visible light is
far more plentiful than the radio spectrum (10,000 times more in
fact) and can achieve far greater data density.
● Data receiver using Li-Fi would have to be in sight of the
transmitter-bulb as visible light does not penetrate solid
materials, which is not the case of Wi Fi.
● Li-Fi is more secure than Wi-Fi with hackers unable to access
unsecured internet connections from out of sight of the
transmitter.

5. LiFi vs WiFi

6. Are Radio waves not fine?
● Capacity: 3G,4G making us running out of spectrum and
hence, radio waves are costly. Radio waves are also limited.
● Efficiency: 1.4 million cellular radio base stations each with
efficiency of just 5%. Most of the energy is used for cooling
down the base station rather than for transmission.
● Security: Radio waves can be transmitted through obstacles
and hence viable for security breach. So far, several successful
attempts were made in hacking.
● Availability: We cannot use our mobile phones which work with
the help of radio waves everywhere. Ex. To be switched off in
aircrafts.

7. Why only Visible Light?
● Gamma rays are dangerous for communication.
● X-rays can't be used for communication as they are to be used
in controlled environment and is costly.
● Ultravoilet rays are useful for skin to some extent but when
used for communication for long time, they are dangerous.
● Infrared rays are to be used at low power levels as their effects
on human eye.
● Radio waves shortcomings have been discussed earlier.
● Visible light has no above mentioned issues,is safe for human
and is faster.

8. How does LiFi work?

9. ● On one end all the data on the internet will be
streamed to a lamp driver.
● When the LED is turned on the microchip converts this
digital data in the form of light.
● On the other end this light is detected by photo
sensitive devices.
● Next this light is amplified and processed and then fed
to the device.
● The heart of this technology is a new generation high
brightness led’s.
● These led’s varies in intensity (that is gets on and off)
so fast that a human eye cannot detect it.
● If led is on , then we transmit a digital signal 1,and if
the led is off , then we transmit a digital signal 0.
● A controller is connected at the back side of these led
bulbs to code data to these leds.

10. Li Fi construction
The LiFi product consists of 4 primary sub-assemblies:
1. 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 plasma generates
an intense source of light.
2. The Printed Circuit Board (PCB) controls the electrical inputs and outputs
of the lamp and houses the microcontroller used to manage different lamp
functions.
3. An RF (radio-frequency) signal is generated by the solid-state PA and is
guided into an electric field about the bulb.
4. All of these sub-assemblies are contained in an aluminum enclosure.

11. Illustration

12. Is it just theoritical?
● No, Herald had successfully demonstrated it using a table lamp.
● The first Li-Fi smartphone prototype was presented at the
Consumer Electronics Show in Las Vegas from January 7–10 in
2014. The phone uses CONNECT, a technique that converts
light waves into usable energy, making the phone capable of
receiving and decoding signals without drawing on its battery.A
clear thin layer of crystal glass can be added to small screens
like watches and smartphones that make them solar powered.
Smartphones could gain 15% more battery life during a typical
day. This first smartphones using this technology should arrive
in 2015. This screen can also work to receive Li-Fi signals and
so can the smartphone camera.The cost of these screens per
smartphone is between $2 and $3, much cheaper than most
new technologies.

13. ● Philips lighting company has developed a Li-Fi system for
shoppers at stores. They have to download an app on their
smartphone and then their smartphone works with the LEDs in
the store. The LEDs can pinpoint where they are at in the store
and give them corresponding coupons and information based
on where aisle they are on and what they are looking at.
● The technology is ready right now. It's being installed in
museums and businesses across France, and is being
embraced by EDF, one of the nation's largest utilities.

14. Where can it be used?
● Everywhere in every field as we use Visible light extensively
including hospitals,aircrafts,etc without bothering about any
harm.
● It can be used in home, office, businesses, museums, etc which
can be used as light, security and data transmission as well.
● It can be used in traffic control (pic demonstrated.)
● Having them on street lights takes the internet usage to a
higher level.

15. Traffic Control

16. Limitations
● There should be line of sight between sender and receiver (This has been
proved to be not necessary experimentally but yet to verify in daily life)
● Visible light cannot penetrate through solid objects
● Interference with other electromagnetic waves makes the transmitting data
to distort.
● Light cannot approach the range of radio waves
● A major challenge facing Li-Fi is how the receiving device will transmit
back to transmitter.
● Interferences from external light sources like sun light, normal bulbs, and
opaque materials in the path of transmission will cause interruption in the
communication.

17. Open for
Questions &
Discussion