i

SEMINAR

ON

Light-Fidelity

(LI-FI)

By:

Ramandeep Singh (C.S.E-1/2011-2015)

Department Of Computer Science and Engineering

Guru Tegh Bahadur Institute of Technology

Guru Gobind Singh Indraprastha University, Dwarka New Delhi

Year-2011-2015

ii

ABSTRACT

Today’s majority of data technique uses Radio Spectrum. But the major drawback of data

technique using radio spectrum is that it is very congested and the demand for wireless data

double each year. Every one, it seems want to use wireless data but the capacity is drying up.

Light –Fidelity is the transmission of data through illumination .It comprises of sending data

through a Light Emitting Diode which varies in intensity faster than human eye can follow .It

uses the fact that light travels at a such a high speed which is faster than human eye to catch.

Therefore when we vary the intensity of light emitting source it become impossible for the

humans to catch that sensation. It leads to very high speed data transmission, which is for

superior to current technologies.

iii

LIST OF TABLES

Table No. Table Name Page No.

1.1 Issues with various Division of Electromagnetic spectrum 3

3.1 Difference between Li-Fi and Wi-Fi 12

iv

LIST OF Figures

Table No. Table Name Page No.

1.1 Issues with various Division of Electromagnetic spectrum 4

3.1 Working of Li-Fi 11

v

CONTENTS

Chapter Page No.

Title Page i

Abstract ii

List of Tables iii

List of Figures iv

Table of Content v

1. Introduction 1

1.1 Existing Technology 1

1.2 Issues with various divisions of electromagnetic spectrum 4

1.3 Widely Used Spectra 5

2. Technology Used Behind 6

2.1 Visible Light Communication 7

2.2History Behind Visible light Communication 8

3. Facts and Working 9

3.1 Important facts about Li-Fi 10

3.2 Illustration of working of Li-Fi 11

3.3 Difference between Li-Fi and other technologies 12

3.4 Difference between Li-Fi and Wi-Fi 12

4. Advantages 13

5. Limitations 15

6. Applications 17

vi

7. Future Scope 19

8. References 21

vii

Chapter One

Introduction

viii

INTRODUCTION

Light –Fidelity is the transmission of data through illumination .It comprises of sending data

through a Light Emitting Diode which varies in intensity faster than human eye can follow .It

uses the fact that light travels at a such a high speed which is faster than human eye to catch.

Therefore when we vary the intensity of light emitting source it become impossible for the

humans to catch that sensation. It leads to very high speed data transmission, which is for

superior to current technologies.

The major advantages of using Light-fidelity is that it uses the visible light spectra which is

still unexplored and have a large bandwidth to use. More advantages including are ,it is harmless,

cheap and have a high capacity.

1.1 Existing Technology

Existing technologies comprises of using different-different spectra of electromagnetic spectrum.

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic

radiation. The "electromagnetic spectrum" of an object has a different meaning, and is instead

the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular

object. The electromagnetic spectrum extends from below the low frequencies used for

modern radio communication to gamma radiation at the short-wavelength (high-frequency) end,

thereby covering wavelengths from thousands of kilometers down to a fraction of the size of

an atom. The limit for long wavelengths is the size of the universe itself, while it is thought that the

short wavelength limit is in the vicinity of the Planck length. Until the middle of last century it was

believed by most physicists that this spectrum was infinite and continuous.

Most parts of the electromagnetic spectrum are used in science for spectroscopic and other probing

interactions, as ways to study and characterize matter. In addition, radiation from various parts of the

spectrum has found many other uses for communications and manufacturing. But today’s majority

of data transmission technique uses Radio Spectrum. It uses the frequency range of radio

waves that is 3 kHz to 300 GHz.

ix

Table 1.1 Division of Electromagnetic spectrum

Region of the

spectrum Main interactions with matter

Radio

Collective oscillation of charge carriers in bulk material (plasma oscillation).

An example would be the oscillatory travels of the electrons in an antenna.

Microwave through far

infrared Plasma oscillation, molecular rotation

Near infrared Molecular vibration, plasma oscillation (in metals only)

Visible

Molecular electron excitation (including pigment molecules found in the

human retina), plasma oscillations (in metals only)

Ultraviolet

Excitation of molecular and atomic valence electrons, including ejection of

the electrons (photoelectric effect)

X-rays

Excitation and ejection of core atomic electrons, Compton scattering (for

low atomic numbers)

Gamma rays

Energetic ejection of core electrons in heavy elements, Compton

scattering (for all atomic numbers), excitation of atomic nuclei, including

dissociation of nuclei

High-energy gamma

rays

Creation of particle-antiparticle pairs. At very high energies a single photon

can create a shower of high-energy particles and antiparticles upon

interaction with matter.

x

1.2 ISSUES WITH VARIOUS DIVISION OF ELECTROMAGNETIC SPECTRA

Fig1.1 Issues with various Division of electromagnetic spectra

xi

1.3 SPECTRUM WHICH IS USED MOST OUT OF ALL THE

PREVIOUSLY MENTIONED IS: RADIO SPECTRUM

1.3.1 Radio Spectrum: Today’s majority of data transmission technique uses Radio Spectrum.

It uses the frequency range of radio waves that is 3 kHz to 300 GHz. The major drawback is that

it is very congested and the demand for wireless data double each year. But the bigger loophole

behind is that every one, it seems want to use wireless data but the capacity is drying up.

1.3.2 Drawbacks of Using Radio Spectrum

Availability: It is available within the range of Base stations and unavailable in aircrafts.

Capacity: Radio spectra have a less amount of band width therefore it is very vulnerable

to get used up in near future.

Efficiency: Consumes huge amount of energy for transmitting radio waves and to cool

the base station cabins

Security: Less secure as it can also pass through walls. So there is greater chance of

interference by others.

xii

Chapter Two

Technology Used Behind

xiii

TECHNOLOGY USED BEHIND

2.1 Visible Light Communication

Light-Fidelity uses the VLC Technology for its operation to be carried out. VLC stands for

Visible Light Communication (VLC) on which scientists including Dr.Gorden Povey, Prof

Harald Hass and Dr.Mostafa Afgani at University Of Edinburgh developed Li-fi.

Visible light communication can be understood as a data communication medium using visible

light between 400 and 800 THz (780-375 nm).Using visible light is less dangerous for high

power applications because humans can perceive it and act to protect their eyes from damage.

Visible light communication is a subset of the optical wireless communication technology.

The devices are normally used for illumination by applying a constant current through the LED.

These devices use fluorescent lamps (ordinary lamps,not special communications devices ) to

transmit signals at 10 kb/s to 500 MB/s currently which would enhance further in the coming

future. Low rate data transmission from 1 and 2 kilometers were demonstrated by Professor

Harald Hass.

Specially designed electronic devices generally containing a photodiode receive signals from

light sources, although in some cases a cell phone,camera or a digital camera will be sufficient .

The image sensor used in these devices is in fact an array of photodiodes. Such a sensor may

provide either multi-channel communication or a spatial awareness of multiple light sources.

The VLC standardization process is conducted within IEEE Wireless Personal Area networks

working group. Recently VLC based indoor positioning system has become an attractive topic

.VLCs can be used for providing security also.VLC can be used as a communication medium for

ubiquitious computing, because light –producing devices (such as indoor/outdoor lamps, car

headlights, etc.) are used everywhere.

Li-fi is the term used for fast and cheap light based Wi-Fi which uses the concept of Visible light

communication. It could make possible the data transmission cheap and fast than the

conventional data transmission technique.

xiv

2.2 HISTORY BEHIND VISIBLE LIGHT COMMUNICATION

The history behind the visible light communication dates back to the 1880s in Washington D.C

when the Scottish born scientist Alexander Graphm Bell invented the photphone, which

transmitted speech on modulated sunlight over several hundred meters .This pre dates the

transmission of speech by radio.

More recent work began in 2003 at Nakagawa laboratory in Keio University,Japan using LEDs

to transmit data by visible light. Since then there have been numerous research activities focused

on VLC ,notably by Smart Lighting Engineering Centre ,Omega Project and work at Oxford

University.

In 2006, researchers from CICTR at Penn State proposed a combination of power line

communication (PLC) and white light LED to provide broadband access for indoor appliactions.

This research suggested that VLC could be deployed as a perfect last mile solution in future.

In January 2010 a team of researchers from Siemens and Fraunhofer Institute for

telecommunications demonstrated transmission at 500 Mb/s with a white LED over a distance of

5 metres and 100 Mb/s over longer distance using five LEDs.

The VLC standardization process is conducted within IEEE Wireless Personal Area

networks working group. Recently VLC based indoor positioning system has become an

attractive topic .VLCs can be used for providing security also.VLC can be used as a

communication medium for ubiquitious computing, because light –producing devices (such as

indoor/outdoor lamps, car headlights, etc.) are used everywhere.

In December 2010 St,Cloud ,Linnesto, signed a contract with LVX Minnesto and became the

first to commercially deploy this technology.

In July 2011 a live demonstration of high definition video being transmitted from a statndard

LED lamp was shown at Ted Global.

Recently ,VLC based indoor positioning system has become an attractive topic. Another recent

application is in the world of toys ,thanks to cost effective and low complexity implementation

,which only requires one microcontroller and one LED as optical front end.More over it has been

also used as optical transreceviers to build up VLc communication which links upto 10 MB/s

xv

Chapter Three

Facts and Working

xvi

3.1 IMPORTANT FACTS ABOUT Li-Fi

Light –Fidelity is the transmission of data through illumination .It comprises of sending data

through a Light Emitting Diode which varies in intensity faster than

human eye can follow .It uses the fact that light travels at a such a high speed which is faster

than human eye to catch.

Therefore when we vary the intensity of light emitting source it become impossible for the

humans to catch that sensation. It leads to very high speed data transmission, which is for

superior to current technologies.

The major advantages of using Light-fidelity is that it uses the visible light spectra which is

still unexplored and have a large bandwidth to use. More advantages including are ,it is harmless,

cheap and have a high capacity.

Some important facts about Light-Fidelity are:

Li-fi is now part of VLC PAN IEEE 802.15.7 standards.

It comprises of sending data through a Light Emitting Diode which varies in intensity faster

than human eye can follow

It uses the fact that light travels at such a high speed which is faster than human eye to

catch.

Instead of Wi-Fi modems, it would use LED lamps that can receive as well as transmit

information.

This technology uses a part of the electromagnetic spectrum that is still not greatly utilized-

Visible Light.

Li-fi has already achieved high speeds in the labs.

Although the maximum speed obtained by researchers is 500 megabytes per second, it is

currently very capable of transmitting 100 megabytes per second.

xvii

3.2 ILLUSTRATION OF WORKING OF Li-Fi

Working of Li-fi is very simple.

If the LED is on, you transmit a 1 and when the LED is off you transmit a 0.

The LED can be switched on and off very quickly, which gives nice

opportunities for transmitting data.

There would be a photo detector (light sensor) on the other end to receive

data.

Fig 3.1 Working of Li-Fi

xviii

3.3 Difference between Li-Fi and other technologies

Li-Fi differs from other technologies as following:

Li-fi is based on LEDs for the transfer of data.

The transfer of data can be with the help of all kinds of light ,no matter the part of spectrum

that they belong to.

The speed of the internet is incredibly high and one can download movies ,games ,etc. in just

a few minutes.

It also removes the limitation to be in a region where Wi-Fi is only present.

We can simply stand under any form of light and surf the internet as the connection is made

in case of any light presence .

3.4 Difference between Li-Fi and other Wireless Fidelity

Table 3.1

Parameters Light Fidelity Wireless Fidelity

Medium Uses light as a carrier Uses radio spectrum

Spectrum range Visible light Spectrum Radio frequency

spectrum

Speed for Data Transfer Future prospect predict

speed>500 Mbps

Data transfer speed>150

Mbps

Cost Cheaper because free

band does not need

Expensive as it uses

radio spectrum.

xix

license and it uses only

light

Operating frequency Hundreds of THz Usually 2.4 GHz.

xx

Chapter Four

Advantages

xxi

Advantages of Li-fi

Higher Bandwidth (almost 10000 times more) :Light fidelity works in the

Electromagnetic range of 430 terahertz to 730 terahertz. This range is far more than

which we currently use in the radio spectra. .The major drawback is that it is very

congested and the demand for wireless data double each year. But the bigger loophole

behind is that every one, it seems want to use wireless data but the capacity is drying up.

Availability: Visible light is available in quite good amount .Therefore it is very easy to

utilize that.

Efficiency: The efficiency can be measured by the input applied to output ,in the case of

Li-Fi the input we give is small amount of constant current but his is very small as

compared to the high speed we get for the data transmission from it.

High Security: One of the drawback of wireless fidelity was security but Li-fi has

reduced this ,as light cannot pass through opaque objects therefore it is more secure than

Wi-Fi.

Easy to use : It could be the most easy to use technology as it just need to switch from on

to off and off to on and data will be transmitted.

Fast data transfer: Li-Fi can provide speed upto 500 Mb/s.This is huge in comparision to

currently available to us.

Harmless: As only visible light is used and it is not harmful to any humans as compared

to x-rays or gamma rays.

Low cost: Li-Fi technology will be cost effective as free band does not need license and

it uses only light. And if compared to wireless fidelity which Expensive as it uses radio

spectrum it will a more edge than before.

High capacity: As the visible light has the maximum bandwidth it have a high capacity

as compared to others.

xxii

Chapter Five

Limitations

xxiii

5.1 Limitations of Li-Fi Technology

Opacity: As Light cannot pass through objects so on one side where it provide security

but it may also lead to limit its capability if it is be used on two different floors.It only

work in direct line of sight.

A major challenge facing Li-fi is hoe the receiving device will transmit back to the

transmitter. So this issue has to be resolved such that practicality of Li-Fi is feasible.

High initial cost of VLC systems: Since some initial cost is necessary for installing Li-Fi

equipment therefore it is a big issue to deal with.

Interferences from external light sources like sun, normal lights and opaque materials can

cause disturbance and even stopping of the light signals .

Well till now these are the only limitations that came forward in front of light fidelity and if these

are overcome we can except a lot of revolution in the field of high data transmission .And Li-Fi

will play a key role in data transmission.

xxiv

Chapter Six

Applications

xxv

6.1 Applications of Li-Fi in human life

6.1.1 In House Communication: Giga shower

For Giga speeds technologies, the Li-fi consortium has defined Giga Shower, Giga MIMO and

Giga Spot. It provides unidirectional data services via several channels to multiple users .This is

like watching TV channels or listening to different radio stations where no uplink channel is

needed.

6.1.2 Traffic Lights

Traffic lights can communicate to each other and vehicles. Cars, Traffic lights and other vehicles

too have LED-based headlights so data can be easily transmitted to each other.

6.1.3 In Aircraft cabins

This is one of the advantage of li-fi as it could be used in aircrafts because Wi-Fi cannot be

used there.

6.1.4 Hospitals

In hospitals li-fi can be used in those instruments which are capable of light emitting and used

for data transmission.

6.1.5 Petroleum Stations

Li-fi can be used in petroleum stations as it provide a great source of light emitting sources like

vehicles.

6.1.6 Street lamps as free access points

As there are millions of street lamps deployed each of them can be used as free access points for

internet and fast data transmission also.

xxvi

Chapter Seven

Future Scope

xxvii

7.1 Future Scope

Further enhancements can be made in this like using an array of LEDs for parallel data

transmission or mixtures of red, green and blue LEDs to alter the light’s frequency encoding a

different channel.

Such development promise a theoretical speed of 10 Gbps-meaning one can download a full

high-definition film in just few seconds. The possibilities are numerous and can be explored

further. If this technology can be used to practicality, every bulb can be used for something like a

Wi-Fi hotspots to transmit wireless data.

Li-Fi can be used in the places where it is difficult to lay the optical fiber . The concept of Li-fi is

currently attracting a great deal of interest ,not because it may offer a genuine and very efficient

alternative to radio –based wireless . As a growing number of people and their many devices

access wireless internet ,the airwaves are becoming increasingly clogged ,making it more

difficult to get a reliable ,high-speed signal. This may solve issues such as the shortage of radio-

frequency bandwidth and also allow internet where traditional radio based wireless isn’t allowed

such as aircraft or hospitals .

xxviii

Chapter Eight

References

xxix

8.1 References

[1] “Visible-light communication : Tripping the light fantastic :A Fast and cheap optical version

of Wi-fi is coming”, Economist, dated 28 Jan 2013

[2] Ritika Tripathi,”Li-Fi (Light Fidelity)-The future technology in wireless communication”,

International Journal of Applied Engineering Research, ISSN 0973-4562 Vol.7 No.11 (2012)

[3] http://en.wikipedia.org/wiki/Li-Fi

[4] www.lificonsortium.org/

[5] www.ijacc.org

[6] www.the-gadgeteer.com/2011/08/29/li-fi-internet-at-the-speed-of-light.html