LIGHT FIDELITY (LI-FI)

TECHNOLOGY

JAYACHANDRAN J PS7-ECE-20

LMCST

CONTENTS

ж ISSUES REGARDING RADIO SPECTRUMж INTRODUCTIONж PRINCIPLE OF LI-FI TECHNOLOGYж VISIBLE LIGHT COMMUNICATIONж CONSTRUCTION and WORKING OF Li-Fiж COMPARISON BETWEEN LI-FI AND WI-FIж FUTURE APPLICATIONSж CHALLENGES FOR LI-FIж CONCLUSIONж REFERENCES

ISSUES REGARDING THE USE OF RADIO SPECTRUM

CAPACITY

EFFICIENCY SECURITY

AVAILABILITY

ж Light–Fidelity (Li-Fi) technology came into existence in 2011.

ж The term was f irst used by Harald Haas in his TED Global talk on Visible Light Communication.

ж In October 2011 a number of companies and industry groups formed the Li-Fi consortium, to promote high-speed optical wireless systems.

ж 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.

INTRODUCTION

INTRODUCTION (contd..)

ж It allows wireless communication without the use of radio waves, which can be dangerous in places like oil platforms, underwater and on planes

ж Li-Fi can be thought of as a light-based Wi-Fi.

HARALD HAAS

PRINCIPLE OF LI-FI TECHNOLOGY

ж Heart of Li-Fi technology is high brightness LED’s.

ж The LED bulb will hold a micro-chip that will do the job of processing the data.

ж The on-off activity of LEDs enables a kind of data transmission using binary codes.

ж Switching on an LED is a logical ‘1’;switching it off is a logical ‘0’.

ж A light sensitive device (photo detector) receives the signal and converts it back into original data.

fig(i)..Sending of data [2]

VISIBLE LIGHT COMMUNICATION

ж Li-Fi is a faster and cheaper version of Wi-Fi, which is based on visible light communication (VLC).

ж 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.

WHY VLC ?

ж Gama rays,X-rays,Ultraviolet rays are harmful for the human body.

ж Infrared rays are also dangerous, due to eye safety regulation, and can only be used with low power.

ж 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 .

Radio Waves

Infrared Rays

Visible Rays

Ultraviolet Rays X- Rays Gama

Rays

Devices used in visible light communication

ж Devices which are used for transmission purpose in VLC are visible light LED and fluorescent lamp.

ж This technology uses fluorescent lamps to transmit signals at 10bit/s, or LED’s for up to 500 Mbit/s.

ж Devices which are used for reception purpose in visible light communication are photo diodes and image sensors.

CONSTRUCTION and WORKING OF Li-Fi

ж Li-Fi is implemented using white LED light bulbs at downlink transmitter.

ж By fast variations of the current, optical output can be made to vary at extremely high speeds.

ж An overhead lamp fitted with an LED with signal processing technology streams data embedded in its beam at ultra high speeds to the photodiodes.

ж 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.

fig(ii)..Working of Li-Fi [1]

fig(iii)..Illustration of data transfer in Li-Fi [3]

COMPARISON BETWEEN LI-FI AND WI-FISl.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

FUTURE APPLICATIONS

ж Li-Fi can be used in sensitive areas such as aircraft for data transmission without causing interference.

ж It can be used in places where it is difficult to lay optical fibres like operation theaters .

ж In traffic scenario, Li-Fi can be used to communicate with the LED lights of cars and might alert drivers when other vehicles are too close so accident numbers can be decreased.

ж It will improve conditions for those working in underwater oil rigs where radio waves can’t propagate.

FUTURE APPLICATIONS(contd..)

ж Thousands and millions of street lamps can be transferred to Li-Fi lamps to transfer data.

ж It can be used in petroleum and chemical plants where other transmission or frequencies could be hazardous.

CHALLENGES FOR LI-FI

ж Presence of Light is essential.ж Li-Fi requires line of sight.ж It is easily blocked by somebody simply

walking in front of LED source.ж The grand vision: “LED lights with added

microchips will let us transmit thousands of data streams in parallel, enabling us to access the Internet on smartphones wherever there is a light source”.[1]

CONCLUSION

ж Researchers are developing micron sized LED .ж 1000 micron sized LED can fit into area

required by 1sq. mm large single LED.

ж A 1 sq.mm sized array of micron sized LED’s could therefore communicate 1000×1000 (i.e. a million) times as much information as a single 1mm LED.

ж Li-Fi consortium believes it is possible to achieve more than 10Gbps, theoretically allowing a high definition film to be downloaded in 30 seconds.

REFERENCES

[1] NEW EPOCH OF WIRELESS COMMUNICATION: LIGHT FIDELITY

Authors: Megha Goyal, Dimple Saproo, Asha Bhagarshra,Journal:  International Journal of Innovative Research in Computer and Communication Engineering ISSN/EISSN: 23209798 23209801 Year:2013 Volume: 1 Issue: 2 http://ijircce.com/upload/2013/april/52_New%20Epoch.pdf

[2] Li-Fi (Light Fidelity)-The future technology In Wireless communicationhttp://www.ripublication.com/ijaer.htm

[3] 'Li-Fi' provides a light bulb moment for wireless web - CNN.com

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