Li-Fi (Light Fidelity) is a new technology that uses visible light communication for wireless transmission of data using light-emitting diodes (LEDs). LEDs can be switched on and off at extremely high speeds to transmit digital signals. A controller is connected to LED bulbs to encode data onto the light. Researchers have achieved data rates over 500 megabytes per second using white LED lights. Li-Fi provides higher speeds, is more secure, has a larger spectrum range than Wi-Fi, and has applications for vehicles, traffic lights, street lamps, airplanes, and hospitals.

1. LI-FI
TECHNOLOGY
PRESENTED BY
Dr. SK. Mastan Vali

2. Li-Fi (Light Fidelity)
• Li-Fi (Light Fidelity) can be thought of as a light-based Wi-Fi
Technology uses The Visible Spectrum
• The term was first used by Harald Haas in his TED
Global talk on Visible Light Communication in 2011
• In October 2011 a number of companies and industry
groups formed the Li-Fi consortium, to promote high-speed
optical wireless systems.
• 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.

3. LI-FI ENVIRONMENT

4. PRINCIPLE OF LI-FI TECHNOLOGY
• The heart of this technology is a new generation high
brightness led’s.
• Visible Light Communication.
• 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 led’s.

5. If led is on , then we transmit a digital signal 1,
and if the led is off , then we transmit a digital signal
0.

6. VISIBLE LIGHT COMMUNICATION
• Li-Fi is a faster and cheaper version of Wi-Fi, which is based on visible light communication
(VLC).
• The visible light communication is a data communication technique using visible light between
400 THz and 800 THz as an optical carrier for data transmission.
Visible
Rays
Radio
Waves
Ultraviolet
Rays
X-rays
Gamma
rays
• Gama rays,X-rays,Ultraviolet rays are harmful for the human body.
• Infrared rays are also dangerous, due to eye safety regulation, and can only be used with low
power.
• Radio waves are expensive and they are less secure.
• Hence we are left with only the VISIBLE - LIGHT SPECTRUM which is not harmful for humans .

8. CONSTRUCTION and WORKING OF Li-Fi
• Li-Fi is implemented using white LED light bulbs at downlink transmitter.
• By fast variations of the current, optical output can be made to vary at extremely
high speeds.
• An overhead lamp fitted with an LED with signal processing technology streams
data embedded in its beam at ultra high speeds to the photodiodes.
• A receiver dongle then converts the tiny changes in amplitude into an electrical
signal, which is then converted back into a data stream & transmitted to a computer
or mobile device.

9. Sl.No Parameters Light Fidelity Wireless Fidelity
1 Speed for data transfer Faster transfer speed (>1 Gbps) Data Transfer speed (150 Mbps)
2 Medium through which
data transfers occurs
Used Light as a carrier Used Radio spectrum
3 Spectrum Range Visible light spectrum has 10,000 time
broad spectrum in comparison to radio
frequency
Radio frequency spectrum range is
less than visible light spectrum.
4 Cost Cheaper than Wi-Fi because free band
doesn’t need license and it use light.
Expensive in comparison to Li-Fi
because its uses radio spectrum.
5 Network topology Point to point Point to point
6 Operating frequency Hundreds of Tera Hz (THz) 2.4 GHz
COMPARISON BETWEEN LI-FI AND WI-FI

10. FUTURE APPLICATIONS
In vehicles and traffic lights, reducing accidents and traffic
congestion

11. Street lamps(as free access points)

12. In Airplanes' And Underwater

13. Hospitals

14. Availability Efficiency Harmless
High
Security
Ease of use Fast Data
Transfer
Low Cost
ADVANTAGES

15. DISADVANTAGES
•Light can't pass through objects.
•A major challenge facing Li-Fi is how the receiving
device will transmit back to transmitter.
•High installation cost of the VLC systems
•Interferences from external light sources like
sun , light , normal bulbs , opaque materials .

16. CONCLUSION
• The possibilities are numerous and can be explored further.
• In spite of disadvantages if this technology can be put into
practical use, every bulb can be used something like a Wi-Fi
hotspot to transmit wireless data and we will proceed toward the
cleaner, greener, safer and brighter future.

17. • Jyoti Rani1, Prerna Chauhan2, Ritika ripathi3,1Student,
,2Student,ad ,3Assistant Professor, ECE, Dep't. " Li-Fi (Light
Fidelity)-The future technology In Wireless communication"
ISSN 0973-4562 Vol.7 No.11 (2012)
• Shailander kaushik, System Analytic,Nuclear Software export
Ltd, "An overview of technical aspects for wifi networks
technology " ,ISSN-2277-1956.
• Visible Light Communications Consortium,www.vlcc.net, 2008
REFERENCES