LI-FI TECHNOLOGY

CHAPTER 1

1.1 INTRODUCTION

Li-Fi is transmission of data through illumination by taking the fiber out of fiber

optics by sending data through a LED light bulb that varies in intensity faster than the

human eye can follow. Li-Fi is the term some have used to label the fast and cheap

wireless-communication system, which is the optical version of Wi-Fi. The term was

first used in this context by Harald Haas in his TED Global talk on Visible Light

Communication.At the heart of this technology is a new generation of high brightness

light-emitting diodes, says Harald Haas from the University of Edinburgh, UK. Very

simply, if the LED is on, you transmit a digital 1, if it‘s off you transmit a 0.Haas

says, They can be switched on and off very quickly, which gives nice opportunities

for transmitted data. It is possible to encode data in the light by varying the rate at

which the LEDs flicker on and off to give different strings of 1s and 0s.The LED

intensity is modulated so rapidly that human eye cannot notice, so the output appears

constant. More sophisticated techniques could dramatically increase VLC data rate.

Terms at the University of Oxford and the University of Edingburgh are focusing on

parallel data transmission using array of LEDs, where each LED transmits a different

data stream. Other group are using mixtures of red, green and blue LEDs to alter the

light frequency encoding a different data channel. Li-Fi, as it has been dubbed, has

already achieved blisteringly high speed in the lab. 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. The technology was demonstrated at the

2012 Consumer Electronics Show in Las Vegas using a pair of Casio smart phones to

exchange data using light of varying intensity given off from their screens, detectable

at a distance of up to ten metres In October 2011 a number of companies and industry

groups formed the Li-F Consortium, to promote high-speed optical wireless systems

and to overcome the limited amount of radio based wireless spectrum available by

exploiting a completely different part of the electromagnetic spectrum. The

consortium believes it is possible to achieve more than 10Gbps, theoretically allowing

a high-definition film to be downloaded in 30 seconds.

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Most of us are familiar with Wi-Fi (Wireless Fidelity), which uses 2.4-5GHz

RF to deliver wireless Internet access around our homes, schools, offices and in

public places. We have become quite dependent upon this nearly ubiquitous service.

But like most technologies, it has its limitations.

While Wi-Fi can cover an entire house, its bandwidth is typically limited to

50-100 megabits per second (Mbps) today using the IEEE802.11n standard. This is a

good match to the speed of most current Internet services, but insufficient for moving

large data files like HDTV movies, music libraries and video games.

Figure 1.1 . Linksys 2.4 Ghz Wireless Router

The more we become dependent upon ‗the cloud‘ or our own ‗media servers‘

to store all of our files, including movies, music, pictures and games, the more we will

want bandwidth and speed. Therefore RF-based technologies such as today‘s Wi-Fi

are not the optimal way.

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CHAPTER 2

2.1 VISABLE LIGHT COMMUNICATION

Many people‘s first exposure to optical wireless technology was VLC. This emerging

technology offers optical wireless communications by using visible light. Today, it is

seen as an alternative to different RF-based communication services in wireless

personal-area networks. An additional opportunity is arising by using current state-of-

the-art LED lighting solutions for illumination and communication at the same time

and with the same module. This can be done due to the ability to modulate LEDs at

speeds far faster than the human eye can detect while still providing artificial lighting.

Thus while LEDs will be used for illumination, their secondary duty could

be to‗piggyback‘ data communication onto lighting systems. This will be

particularly relevant in indoor ‗smart‘ lighting systems, where the light is always

‗on.‘

In contrast to infrared, the so-called _what you see is what you send feature

can be used to improve the usability of transmitting data at shorter point-to-point

distances between different portable or fixed devices. There, illumination can be used

for beam guiding, discovery or generating an alarm for misalignment.

Fig 2.1 Electromagnetic spectrum

The premise behind VLC is that because lighting is nearly everywhere,

communications can ride along for nearly free. Think of a TV remote in every LED

light bulb and you‘ll soon realise the possibilities of this technology

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One of the biggest attractions of VLC is the energy saving of LED technology.

Nineteen per cent of the worldwide electricity is used for lighting. Thirty billion

light bulbs are in use worldwide. Assuming that all the light bulbs are exchanged

with LEDs, one billion barrels of oil could be saved every year, which again

translates into energy production of 250 nuclear power plants.

Driven by the progress of LED technology, visible light communication is

gaining attention in research and development. The VLC Consortium (VLCC) in

Japan was one of the first to introduce this technology.

After establishing a VLC interest group within the IEEE 802.15 wireless

personal-area networks working group, the IEEE 802.15.7 task group was established

by the industry, research institutes and universities in 2008. The final standard was

approved in 2011. It specifies VLC comprising mobile-to-mobile (M2M), fixed-to-

mobile (F2M) and infrastructure-to-mobile (I2M) communications. There, the focus is

on low-speed, medium-range communications for intelligent traffic systems and on

high-speed, short range M2M and F2M communications to exchange, for example,

multimedia data. Data rates are supported from some 100 kbps up to 100 Mbps using

different modulation schemes. Other standardisation groups are working on

standardised optical wireless communication (OWC) solutions using visible and

infrared light. The most important groups are IrDA with its new 10 Giga-IR working

group, ISO and ICSA.

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CHAPTER 3

3.1 LIGHT FIDELITY (Li-Fi)

VLC represents only a fraction of what appears to be a much larger movement

towards optical wireless technologies in general. This larger word has been dubbed

‗Li-Fi‘ (Light Fidelity) by Dr Harald Haas of Edinburgh University and organisations

such as the Li-Fi Consortium.

Figure 3.1“Li Fi”- The Term Coined By Dr Harald Haas

Li-Fi is a VLC, visible light communication, technology developed by a team

of scientists including Dr Gordon Povey, Prof. Harald Haas and Dr Mostafa Afgani at

the University of Edinburgh. The term Li-Fi was coined by Prof. Haas when he

amazed people by streaming high-definition video from a standard LED lamp,at TED

Global in July 2011. Li-Fi is now part of the Visible Light Communications (VLC)

PAN IEEE 802.15.7 standard.

Li-Fi is typically implemented using white LED light bulbs. These devices are

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

However, by fast and subtle variations of the current, the optical output can be made

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to vary at extremely high speeds.Unseen by the human eye, this variation is used to

carry high-speed data, says Dr Povey, , Product Manager of the University of

Edinburgh's Li-Fi Program‘D-Light Project’.

Li-Fi is a short term of light fidelity. Just like the more commonly known

wireless fidelity,it aims to transfer data through light. It is a technology based on

LED‘s for the exchange of data. Data will be sent via light, all kinds of light,

regardless the part of the spectrum where they belong. Li-Fi has been developed by

Haas whose expertise is on the mobile communications at Edinburgh University,

known as the head over heels in LED from his teenage years.

In that connection, Li-Fi comprises several optical wireless technologies such

as optical wireless communication, navigation and gesture recognition applied for

natural user interfaces .Thus it provides a completely new set of optical technologies

and techniques to offer users add-on as well as complementary functionalities

compared to well-known and established RF services. This could reach from a new

user experience regarding communication speeds in the gigabit class to bridge the

well-known spectrum crunch, over to precise indoor positioning or controlling video

games, machines or robots with entirely new natural user interfaces. Finally, these and

many more could be merged to a full-featured Li-Fi cloud providing wireless services

for other future applications as well.

Li-Fi comprises a wide range of frequencies and wavelengths, from the

infrared through visible and down to the ultraviolet spectrum. It includes sub-gigabit

and gigabit-class communication speeds for short, medium and long ranges, and

unidirectional and bidirectional data transfer using line-of-sight or diffuse links,

reflections and much more. It is not limited to LED or laser technologies or to a

particular receiving technique. Li-Fi is a framework for all of these providing new

capabilities to current and future services, applications and end users.

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Fig 3.2 Transfer of data through light

Within a local Li-Fi cloud several databased services are supported through a

heterogeneous communication system. In an initial approach, the Li-Fi Consortium

defined different types of technologies to provide secure, reliable and ultra-high-

speed wireless communication interfaces. These technologies included giga-speed

technologies, optical mobility technologies, and navigation, precision location and

gesture recognition technologies.

For giga-speed technologies, the Li-Fi Consortium defined GigaDock,

GigaBeam, GigaShower, GigaSpot and GigaMIMO models to address different

user scenarios for wireless indoor and indoor-like data transfers. While GigaDock is

a wireless docking solution including wireless charging for smartphones, tablets or

notebooks, with speeds up to 10 Gbps, the GigaBeam model is a point-to-point data

link for kiosk applications or portable-to-portable data exchanges. Thus a two-hour

full HDTV movie (5 GB) can be transferred from one device to another within four

seconds. GigaShower, GigaSpot and Giga- MIMO are the other models for in-

house communication.

There a transmitter or receiver is mounted into the ceiling connected to, for

example, a media server. On the other side are portable or fixed devices on a desk

in an office, in an operating room, in a production hall or at an airport. GigaShower

provides unidirectional data services via several channels to multiple users with

gigabit-class communication speed over several metres.

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This is like watching TV channels or listening to different radio stations

where no uplink channel is needed. In case GigaShower is used to sell books, music

or movies, the connected media server can be accessed via Wi-Fi to process

payment via a mobile device. GigaSpot and GigaMIMO are optical wireless single-

and multi-channel HotSpot solutions offering bidirectional gigabit-class

communication in a room, hall or shopping mall for example.

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CHAPTER 4

4.1 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-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.

4.2 Methods of Visible Light Communication

Devices used for Visible Light Communication

Communication using Image Sensors

Devices used for Visible Light Communication

Fig 4.1 Communication system

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Transmitter devices of visible light communication

1.>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)

2.> Fluorescent Lamp

FSK modulation of high frequency fluorescent light.

Data rate: up to several kilo bps.

Receiver devices of visible light communication

1.>PIN 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.

2.>Avalanche photodiode

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

reached and hence a greater operating gain (>1000).In general, the higher the reverse

voltage the higher the gain.

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Communication through image sensors

An 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.

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CHAPTER 5

5.1 WORKING TECHNOLOGY

VLC 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

1) a high brightness white LED, Which acts as a communication source and

2) 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 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.

Very simply, if the LED is on, you transmit a digital 1, if it‘s off you transmit

a 0,Haas says, ―They can be switched on and off very quickly, which gives nice

opportunities for transmitted data.It is possible to encode data in the light by varying

the rate at which the LEDs flicker on and off to give different strings of 1s and 0s.The

LED intensity is modulated so rapidly that human eye cannot notice, so the output

appears constant. More sophisticated techniques could dramatically increase VLC

data rate. Terms at the University of Oxford and the University of Edingburgh are

focusing on parallel data transmission using array of LEDs, where each LED

transmits a different data stream. Other group are using mixtures of red, green and

blue LEDs to alter the light frequency encoding a different data channel. Li-Fi, as it

has been dubbed, has already achieved blisteringly high speed in the lab. 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. The technology was

demonstrated at the 2012 Consumer Electronics Show in Las Vegas using a pair of

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Casio smart phones to exchange data using light of varying intensity given off from

their screens, detectable at a distance of up to ten metres.

Figure 5.1 Working of LI-FI

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 frequency with International Journal of Applied

Engineering Research, ISSN 0973-4562 Vol.7 No.11 (2012)© Research India

Publications; http://www.ripublication.com/ijaer.htm each frequency encoding is a

different data channel. Such advancements promise a theoretical speed of 10 Gbps –

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

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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.

Figure 5.2 Block Diagram

A flickering light can 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 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. 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 characterisation Li-Fi.

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Fig 5.3 Data from internet to user through light

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CHAPTER 6

6.1 COMPARISION BETWEEN LI-FI&WI-FI

LI-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.

Table 6.1Comparison between current and future wireless technologies

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.

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6.2 ISSUES WITH WI-FI USING RADIO WAVES

Fig 6.1 Four aspects of WI-FI

There are four issues with the current wi-fi scenario , which are :-

1.>CAPACITY:

We transmit wireless data is by using electromagnetic waves -- inparticular,

radio waves.

Radio waves are scarce, expensive and we only have a certain range of it.

Due to this limitation one can’t forever hope to cope with the demand of

wireless data transmissions and the number of bytes and data which are

transmitted every month.

2.>EFFICIENCY

There are 1.4 million cellular radio masts deployed worldwide.

Most of the energy consumed, is not used to transmit the radio waves,but is

used to cool the base stations.

The efficiency of such a base station is only at about five percent.

3.>AVAILABILITY

Availability of radio waves or RW signals causes another concern

We have to switch off our mobile devices in aero planes

It is not advisable to use mobiles at places like petrochemical plants and

petrol pumps

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4.>SECURITY

The radio waves penetrate through walls.

They can be intercepted, and somebody can make use of one‘s network.

6.3 LI-FI IS DIFFERENT COMPARE TO WI-FI

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 is incredibly 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 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.

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CHAPTER 7

7.1 FUTURE PROSPECTS

First applications of Li-Fi have been put to use already, for example,in hospitals

where RF signal are a threat due to interference problems with medical equipment

such as blood pumps and other life supporting instruments. Axiomtek Europe

presented such a product at the Embedded World exhibition in Nurnberg, Germany.

The prototype of a mobile phone with an incorporated VLC system was presented by

Casio at the Consumer Electronics Show in Las Vegas in January this year. In the

coming years, we will see more Li-Fi products entering the market, both in the

industrial as well as consumer markets.

Fig 7.1 Anticipated uses of VLC Technology

7.2 APLICATIONS

7.2.1 Enhanced & Exclusive Shopping Experience

Imagine yourself walking into a mall where GPS signals are unavailable but the mall

is equipped with ceiling bulbs that create their own ‗constellation‘ of navigation

beacons. As the camera of your cell phone automatically receives these signals, it

switches your navigation software to use this information to guide you to the ATM

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machine you‘re looking for. You conclude your ATM transaction and notice the

GigaSpot sign for instant digital movie downloads. You pick out that new Tom Cruise

movie using your phone‘s payment facility, and then download within a few seconds

the high-definition movie into the GigaLink flash drive plugged into the USB port of

your smartphone.

As you walk away, your phone notifies you that the leather jacket Tom

featured in the movie is on sale nearby. You walk over towards the show window and

your image comes up on the screen, wearing that coveted jacket. You turn and pose

while the image matches your orientation and body gestures for a _digital fitting.‘

When you walk into the store, the clerk hands you the actual jacket in exactly your

size.

7.2.2 You Might Just Live Longer

For a long time, medical technology has lagged behind the rest of the wireless world.

Operating rooms do not allow Wi-Fi over radiation concerns, and there is also that

whole lack of dedicated spectrum. While Wi-Fi is in place in many hospitals,

interference from cell phones and computers can block signals from monitoring

equipment. Li-Fi solves both problems: lights are not only allowed in operating

rooms, but tend to be the most glaring (pun intended) fixtures in the room. And, as

Haas mentions in his TED Talk, Li-Fi has 10,000 times the spectrum of Wi-Fi, so

maybe we can delegate red light to priority medical data. Code Red!

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Figure 7.2 Use In Medical Field

7.2.3 Airlines

Nothing says captive audience like having to pay for the "service" of dial-up speed

Wi-Fi on the plane. And don‘t get me started on the pricing. The best I‘ve heard so far

is that passengers will "soon" be offered a "high-speed like" connection on some

airlines. United is planning on speeds as high as 9.8 Mbps per plane. Uh, I have twice

that capacity in my living room. And at the same price as checking a bag, I expect it.

Li-Fi could easily introduce that sort of speed to each seat's reading light. I‘ll be the

guy WoWing next to you. Its better than listening to you tell me about your wildly

successful son, ma‘am.

Figure 7.3 Use in airlines

7.2.3 Smarter Power Plants

Wi-Fi and many other radiation types are bad for sensitive areas. Like those

surrounding power plants. But power plants need fast, inter-connected data systems to

monitor things like demand, grid integrity and (in nuclear plants) core temperature.

The savings from proper monitoring at a single power plant can add up to hundreds of

thousands of dollars. Li-Fi could offer safe, abundant connectivity for all areas of

these sensitive locations. Not only would this save money related to currently

implemented solutions, but the draw on a power plant‘s own reserves could be

lessened if they haven‘t yet converted to LED lighting.

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Figure 7.4 Use in power plants

7.2.4 Undersea Awesomeness

Underwater ROVs, those favourite toys of treasure seekers and James Cameron,

operate from large cables that supply their power and allow them to receive signals

from their pilots above. ROVs work great, except when the tether isn‘t long enough to

explore an area, or when it gets stuck on something. If their wires were cut and

replaced with light _say from a submerged, high-powered lamp _then they would be

much freer to explore. They could also use their headlamps to communicate with each

other, processing data autonomously and referring findings periodically back to the

surface, all the while obtaining their next batch of orders.

Figure 7.5 Under sea awesomeness

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7.2.5 It Could Keep You Informed and Save Lives

Say there‘s an earthquake in New Delhi,or a hurricane. Take your pick — it‘s a

wacky city. The average Delhiite may not know what the protocols are for those kinds

of disasters. Until they pass under a street light, that is. Remember, with Li-Fi, if

there‘s light, you‘re online. Metro stations and tunnels, common dead zones for most

emergency communications, pose no obstruction. Plus, in times less stressing cities

could opt to provide cheap high-speed Web access to every street corner

Figure 7.6 Use of li fi in traffic control

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CHAPTER 8

8.1 CONCLUSION

The concept of Li-Fi is currently attracting a great deal of interest, not least because it

may offer a genuine and very efficient alternative to radio-based wireless. As a

growing number of people and their any devices access wireless internet, the airwaves

are becoming increasingly clogged, making it more and 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. One of the shortcomings however is that it

only work in direct line of sight.

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CHAPTER 9

9.1 Bibliography

1. www.wikisedia.co m

2. www.visiblelightcomm.com /

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

4.technopits.blogspot.comtechnology.cgap.org/2012/01/11/a-lifi-world/

5.www.lificonsortium.org/

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