Li fi report

2013

Li-Fi

Acknowledgement

I take this opportunity to express my deep sense of gratitude and thankfulness to my project guide, Ms. Sarita Das andMs. Nalini Prabha Behera(HOD, CSE) under whose able guidance I have been successful in finishing the project work.

Vivek Kumar JhaRegd. No – 1001215240

Branch – CSEEAST

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CertificateThis is to certify that Master Vivek Kumar Jha, 6th Sem, CSE Branch has completed & duly submitted his seminar report hard copy correctly within the stipulated time. His work was found to be genuine & correct.

Ms. N.P. Behera Ms. Sarita Das Ms. S. Mishra

(H.O.D, CSE) (Project Guide) (Principal, EAST)

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Contents

Acknowledgement_____________________________1 Certificate____________________________________2 Abstract_____________________________________3 Introduction__________________________________4 System Design________________________________6 Present Scenario______________________________15 Issues with Radio Waves_______________________16 Li-Fi as an alternative__________________________17 Light for wireless Communication________________19 Implementation_______________________________19 Achieving Communication through light___________25 Overcoming the issues_________________________26 Application__________________________________27 Conclusion__________________________________28 Reference___________________________________29

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Abstract

hether you’re using wireless internet in a coffee shop,stealing it from the guy next door, or competing for bandwidth at a conference, you have

probably gotten frustrated at the slow speeds you face when more than one device is tapped into the network. As more and more people and their manydevices access wireless internet, clogged airwaves are going tomake it.

W

One German physicist, Harald Haas has come up with asolution he calls “data through illumination” –taking the fibberout of fiber optic by sending data through an LED light bulbthat varies in intensity faster than the human eye can follow.It’s the same idea band behind infrared remote controls but farmore powerful.

Haas says his invention, which he calls D-Light,can produce data rates faster than 10 megabits persecond, which is speedier than your average broadbandconnection. He envisions a future where data for laptops,smart phones, and tablets is transmitted through the light in aroom. And security would be snap – if you can’t see the light,you can’t access the data.

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Introduction to Li-Fi

i-Fi is transmission of data through illumination by taking thefiber out of fiber optics by sending data through a LED lightbulb that varies in intensity faster

than the human eye canfollow.L

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“At the heart of this technology is a newgeneration of high brightness light-emitting diodes”, saysHarald Haas from the University of Edinburgh, UK.”Verysimply, if the LED is on, you transmit a digital 1, if it’s offyou transmit a 0,”Haas says, “They can be switched on and offvery quickly, which gives nice opportunities for transmitteddata.”

It is possible to encode data in the light by varying therate at which the LEDs flicker on and off to give differentstrings of 1s and 0s.The LED intensity is modulated so rapidlythat human eye cannot notice, so the output appears constant.

More sophisticated techniques could dramatically increaseVLC data rate. Terms at the University of Oxford and theUniversity of Edinburgh are focusing on parallel datatransmission using array 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 frequency encoding adifferent data channel.

Li-Fi, as it has been dubbed, has alreadyachieved blisteringly high speed in the lab. Researchers at theHeinrich Hertz Institute in Berlin, Germany have reached datarates of over 500 megabytes per second using a standardwhite-light LED.

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System Design

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.

This very property of optical current is used in Li-Fi

setup.The operational procedure is very simple-,data from

the internet and local network is used to modulate the

intensity of the LED light source if any undetectable to the

human eye. The photo detector picks up signal, which is

converted back into a data stream and sent to the client.

The client can communicate through its own LED output or

over the existing network. An overhead lamp fitted with an

LED with signal-processing technology streams data

embedded in its beam at ultra-high speeds to the photo-

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detector. A receiver dongle then converts the tiny changes in

amplitude into an electrical signal, which is then converted

back into a data stream and transmitted to a computer or

mobile device.

Data Transmission Using LED

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Methods of Visible Light

Communication Devices used for Visible Light Communication

Communication using Image Sensors

Devices used for Visible Light

Communication

Transmitter Device Receiver Device

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Visible Light

Methods of Visible Light

CommunicationTransmitter device of visible light communication

Visible Light LED

LED light intensity is modulated by controlling its

current.

Data rate: low speed to very high speed (up to several

hundred Mbps)

Visible Light LED

Fluorescent Lamp FSK modulation of high frequency fluorescent light.

Data rate: up to several kilo bps.

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Fluorescent Lamp

Receiver device of visible light

communication

PIN photo diode:

A PIN diode is a diode with a wide, lightly doped 'near'

intrinsic semiconductor region between a p-type

semiconductor and an n-type semiconductor region. The p-

type and n-type regions are typically heavily doped because

they are used for Ohmic contacts.

The wide intrinsic region is in contrast to an ordinary PN

diode. The wide intrinsic region makes the PIN diode an

inferior rectifier (one typical function of a diode), but it

makes the PIN diode suitable for attenuators, fast switches,

photo detectors, and high voltage power electronics

applications.

Operation:

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A PIN diode operates under what is known as high-level

injection. In other words, the intrinsic "i" region is flooded

with charge carriers from the "p" and "n" regions. Its

function can be likened to filling up a water bucket with a

hole on the side. Once the water reaches the hole's level it

will begin to pour out. Similarly, the diode will conduct

current once the flooded electrons and holes reach an

equilibrium point, where the number of electrons is equal to

the number of holes in the intrinsic region. When the diode is

forward biased, the injected carrier concentration is typically

several orders of magnitude higher than the intrinsic level

carrier concentration. Due to this high level injection, which

in turn is due to the depletion process, the electric field

extends deeply (almost the entire length) into the region.

This electric field helps in speeding up of the transport of

charge carriers from P to N region, which results in faster

operation of the diode, making it a suitable device for high

frequency operations.

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PIN photodiode

Avalanche photo diode

An avalanche photodiode (APD) is a highly sensitive

semiconductor electronic device that exploits

the photoelectric effect to convert light to electricity. APDs

can be thought of as photo detectors that provide a built-in

first stage of gain through avalanche multiplication. From a

functional standpoint, they can be regarded as the

semiconductor analog to photo multipliers.By applying a high

reverse bias voltage (typically 100-200 V in silicon), APDs

show an internal current gain effect (around 100) due

to impact ionization (avalanche effect). However, some

silicon APDs employ alternative doping and beveling

techniques compared to traditional APDs that allow greater

voltage to be applied (> 1500 V) before breakdown is

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reached and hence a greater operating gain (> 1000).In

general, the higher the reverse voltage the higher the gain.

Figure-2.6: Avalanche photo diode

APD applicability and usefulness depends on many

parameters. Two of the larger factors are: quantum

efficiency, which indicates how well incident optical photons

are absorbed and then used to generate primary charge

carriers; and total leakage current, which is the sum of the

dark current and photocurrent and noise. Electronic dark

noise components are series and parallel noise. Series noise,

which is the effect of shot noise, is basically proportional to

the APD capacitance while the parallel noise is associated

with the fluctuations of the APD bulk and surface dark

currents. Another noise source is the excess noise factor, F.

It describes the statistical noise that is inherent with the

stochastic APD multiplication process.

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Image sensorAn image sensor is a device that converts an optical

image into an electronic signal. It is used mostly in digital

cameras, camera modules and other imaging devices. Early

analog sensors were video camera tubes; most currently used

are digital charge-coupled device (CCD) or complementary

metal–oxide–semiconductor (CMOS) active pixel sensors.

Image sensor

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Communication using Image

Sensors

Principles of communication using image

sensor

Principles of Communication Using Image Sensor

Camera (receiver) continuously takes images of a scene with

an LED light and a receiver detects the optical intensity at a

pixel where the LED light is focused on.

Even if multiple visible light sources send data

simultaneously, an image sensor is able to receive and

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demodulate all the data simultaneously without any

interference between them.

Merits of communication using image sensor

Number of signal: Multiple.

Robustness: no cross talk/no Interference.

Distance: Very Long (2km).

Space Resolution: Each pixel.

Areas to which visible light communication technology may

be applied

Applications that do personal area communication.

Applications that enable users to know users locations

in several meter accuracy.

Applications that enable users to know users locations

in several millimeter accuracy.

Applications that use augmented reality.

Applications that cannot be achieved by radio-wave

technology.

Present Scenario

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We have 1.4million cellular mast radio waves base stations deployed.

We also have over 5 billions of mobile phones. Mobile phone transmits more than 600 Tb of data. Wireless communication has become a utility like

electricity & water. We use it in our everyday life, in our private life,

business life. Currently Wi-Fi uses Radio Waves for communication. It is important to look into this technology which has

become fundamental to our life.

Four Issues with Radio Waves

1. Capacity: Radio waves are limited. Radio waves are scarce and expensive. We only have a certain range of it. With the advent of the new generation

technologies like 2.5G, 3G, 4G and so on we are running out of spectrum.

2. Efficiency: There are 1.4 million cellular radio base stations. They consume massive amount of energy. Most of this energy is not used for transmission but

for cooling down the base stations.

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Efficiency of such a base station is only 5%.

3. Availability: Availability of radio waves is another cause of

concern. We have to switch off our mobiles in aero planes. It is not advisable to use mobiles at places like

petrochemical plants and petrol pumps.

4. Security: Radio waves penetrate through walls. They can be intercepted. If someone has knowledge and bad intentions then

he may misuse it.

Alternative to Radio Waves in electromagnetic Spectrum

There are four major concerns i.e., capacity, efficiency,

availability and security related with Radio waves.

But on the other hand we have 40 billions of light box

already installed and light is the part of

electromagnetic spectrum.

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Gamma rays are simply very dangerous and thus can’t be used for our purpose of communication.

X-rays are good in hospitals and can’t be used either. Ultra-violet rays are good for getting a sun-tan but exposure for

long duration is dangerous. Infrared rays are bad for our eyes and are therefore used at low

power levels. We have already seen the shortcomings of Radio waves.

So we are left with only Visible Light Spectrum.

Also if we see the spectrum band of visible light than we will find that it is 10000 times more than that of radio waves.

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Light for Wireless Communication Light has been around for millions of years.

It has created us created life and has created all stuffs of

life.

Visible light Communication (VLC) uses rapid pulses of

light to transmit information wirelessly. Now it may be

ready to compete with conventional Wi-Fi.

So it is inherently safe to use for wireless communication.

IMPLEMENTATION

This brilliant idea was first showcased by Harald Haas from

University of Edinburgh, UK, in his TED Global talk on VLC.

He explained,” 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.” So what you require at

all are some LEDs and a controller that code data into those

LEDs. We have to just vary the rate at which the LED’s

flicker depending upon the data we want to encode. Further

enhancements can be made in this method, like using an

array of LEDs for parallel data transmission, or using

mixtures of red, green and blue LEDs to alter the light’s

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frequency with each frequency encoding a different data

channel.

Such advancements promise a theoretical speed of

10Gbps– meaning you can download a full high-definition film

in just 30 seconds. Simply awesome! But blazingly fast data

rates and depleting bandwidths worldwide are not the only

reasons that give this technology an upper hand. Since Li-Fi

uses just the light, it can be used safely in aircrafts and

hospitals that are prone to interference from radio waves.

This can even work underwater where Wi-Fi fails completely,

thereby throwing open endless opportunities for military

operations.

Imagine only needing to hover under a street lamp to get

public internet access, or downloading a movie from the lamp

on your desk. There's a new technology on the block which

could, quite literally as well as metaphorically, 'throw light

on' how to meet the ever-increasing demand for high-speed

wireless connectivity. Radio waves are replaced by light

waves in a new method of data transmission which is being

called Li-Fi. Light-emitting diodes can be switched on and off

faster than the human eye can detect, causing the light

source to appear to be on continuously. A flickering light can

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be incredibly annoying, but has turned out to have its upside,

being precisely what makes it possible to use light for

wireless data transmission. Light-emitting diodes (commonly

referred to as LEDs and found in traffic and street lights, car

brake lights, remote control units and countless other

applications) can be switched on and off faster than the

human eye can detect, causing the light source to appear to

be on continuously, even though it is in fact 'flickering'. This

invisible on-off activity enables a kind of data transmission

using binary codes: switching on an LED is a logical '1',

switching it off is a logical '0'. Information can therefore be

encoded in the light by varying the rate at which the LEDs

flicker on and off to give different strings of 1s and 0s. This

method of using rapid pulses of light to transmit information

wirelessly is technically referred to as Visible Light

Communication (VLC), though it’s potential to compete with

conventional Wi-Fi has inspired the popular characterization

Li-Fi.

Visible light communication “A

potentialsolution to the global wireless

spectrum shortage ”

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Li-Fi (Light Fidelity) is a fast and cheap optical version of Wi-

Fi, the technology of which is based on Visible Light

Communication (VLC).VLC is a data communication medium,

which uses visible light between 400 THz (780 nm) and 800

THz (375 nm) as optical carrier for data transmission and

illumination. It uses fast pulses of light to transmit

information wirelessly.

The main components of this communication system are

a high brightness white LED, Which acts as a

communication source and

a silicon photodiode which shows good response to

visible wavelength region serving as the receiving

element.

LED can be switched on and off to generate digital strings of

1s and 0s.

Data can be encoded in the light to generate a new data

stream by varying the flickering rate of the LED. To be

clearer, by modulating the LED light with the data signal, the

LED illumination can be used as a communication source. As

the flickering rate is so fast, the LED output appears constant

to the human eye. A data rate of greater than 100 Mbps is

possible by using high speed LEDs with appropriate

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multiplexing techniques. VLC data rate can be increased by

parallel data transmission using LED arrays where each LED

transmits a different data stream. There are reasons to prefer

LED as the light source in VLC while a lot of other

illumination devices like fluorescent lamp, incandescent bulb

etc. are available.

COMPARISION BETWEEN Li-Fi & Wi-FiLI-FI is a term of one used to describe visible light

communication technology applied to high speed wireless

communication. It acquired this name due to the similarity to

WI-FI, only using light instead of radio. Wi-Fi is great for

general wireless coverage within buildings, and Li-Fi is ideal

for high density wireless data coverage in confined area and

for relieving radio interference issues, so the two

technologies can be considered complimentary.

Technology Speed Data density

Wireless (current)

Wi-Fi – IEEE 802.11n 150 Mbps *

Bluetooth 3 Mbps **

IrDA 4 Mbps ***

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Wireless (future)

WiGig 2 Gbps **

Giga-IR 1 Gbps ***

Li-Fi >1Gbps >1Gbps ****

Comparison between current and future wireless technology

The table also contains the current wireless technologies that

can be used for transferring data between devices today, i.e.

Wi-Fi, Bluetooth and IrDA. Only Wi-Fi currently offers very

high data rates. The IEEE 802.11.n in most implementations

provides up to 150Mbit/s (in theory the standard can go to

600Mbit/s) although in practice you receive considerably less

than this. Note that one out of three of these is an optical

technology.

How it is different?Li-Fi technology is based on LEDs for the transfer of

data. The transfer of the data can be with the help of all

kinds of light, no matter the part of the spectrum that they

belong. That is, the light can belong to the invisible,

ultraviolet or the visible part of the spectrum. Also, the speed

of the internet isincredibly high and you can download

movies, games, music etc in just a few minutes with the help

of this technology. Also, the technology removes limitations

that have been put on the user by the Wi-Fi. You no more

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need to be in a region that is Wi-Fi enabled to have access to

the internet. You can simply stand under any form of light

and surf the internet as the connection is made in case of any

light presence. There cannot be anything better than this

technology.

What we have to do?

We have to replace inefficient fluorescents with this new

dignitary of LED lights.

The LED will hold a micro-chip that will do the job of

processing the data.

Light intensity can be modulated at very high speeds to

send data by tiny changes in amplitude.

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Achieving Communication through LightLet’s start with the foremost communication device which everyone has in their homes i.e., a Remote Control. A remote control has an Infrared-LED. It creates a single data stream and the data rate achieved is around 10000b/s to 20000b/s. Now if we replace the remote control with a light box, we are able to transmit 1000’s of data stream in parallel at high speeds. This technology is termed as Spatial Modulation.

Remote Control Data via LED

Is it a Proven Technology?Yes, this is already proven.

Harald Haas demonstrated his invention using an ordinary table lamp that successfully transmitted data at speeds exceeding 10Mbps using light waves from LED light bulbs to a computer located below the lamp.

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To prove that the light bulb was the source of the data

stream, he periodically blocked the beam of light, causing the

connection to drop.

Overcoming the four issues with RW

in Li-Fi

1. Capacity:

10000 times more spectrum than RW.

LEDs are already present.

So we have the infrastructure available and

already installed.

2. Efficiency:

Data through illumination and thus data

transmission comes for free.

LED light consumes less energy

Highly efficient

3. Availability

Light is present everywhere.

4. Security:

Light waves don’t penetrate through walls.

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Data is present where there is light.

Applications of Li-Fi

At present its applications are beyond imagination but still if

to think about few then they are:

Can be used in places where it is difficult to lay the

optical fiber like hospitals. In operation theatre Li-Fi can

be used for modern medical instruments.

In traffic signals Li-Fi can be used which will

communicate with LED lights of the cars and accident

numbers can be decreased.

Thousand and millions of street lamps can be transferred

to Li-Fi Lamps to transfer data.

In aircraft Li-Fi can be used for data transmission.

It can be used in petroleum or chemical plants where

other transmission or frequencies could be hazardous.

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Conclusionhe possibilities are numerous and can be explored

further. If this technology can be put into practical

use, every bulb can beused something like a Wi-Fi

hotspot to transmit wireless dataand we will proceed toward

the cleaner, greener, safer andbrighter future. The concept

of Li-Fi is currently attracting agreat deal of interest, not

least because it may offer a genuineand very efficient

alternative to radio-based wireless. As agrowing number of

people and their many devices accesswireless internet, the

airwaves are becoming increasinglyclogged, making it more

and more difficult to get a reliable,high-speed signal. This

may solve issues such as the shortageof radio-frequency

bandwidth and also allow internet wheretraditional radio

based wireless isn’t allowed such as aircraftor hospitals. One

of the shortcomings however is that it onlywork in direct line

of sight.

T

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References

http://en.wikipedia.org/wiki/Li-Fi

http://teleinfobd.blogspot.in/2012/01/what-is-lifi.html

www. lifi consortium.org/

Will Li-Fi be the new Wi-Fi?, New Scientist, byJamie

Condliffe, dated 28 July 2011

http://www.digplanet.com/wiki/Li-Fi

“Visible-light communication: Tripping the lightfantastic:

A fast and cheap optical version of Wi-Fi iscoming”,

Economist, dated 28Jan 201

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