1

CHAPTER 1

INTRODUCTION

LiFi 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. Light is inherently

safe and can be used in places where radio frequency communication is often deemed

problematic, such as in aircraft cabins or hospitals. So visible light communication not only

has the potential to solve the problem of lack of spectrum space, but can also enable novel

application. The visible light spectrum is unused; it's not regulated, and can be used for

communication at very high speeds.

2

Fig.1.1 Li-Fi environment

In October 2011 a number of companies and industry groups formed the Li-Fi Consortium, to

promote high-speed optical wireless systems and to overcome the limited amount of

radiobased wireless spectrum available by exploiting a completely different part of the

electromagnetic spectrum. The consortium believes it is possible to achieve more than 10

Gbps, theoretically allowing a high-definition film to be downloaded in 30 seconds.

1.1 WORKING TECHNOLOGY

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

3

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 each frequency

encoding 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 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 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.

4

Visible light communication (VLC)-“A potential solution to the global

wireless spectrum shortage”

LiFi (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 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.

5

Fig 1.2.Data transmission using LED

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1.2 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 1.1Comparison 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.

7

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 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.

Fig1.3.Working and advantages

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CHAPTER 2

APPLICATION OF LI-FI:-

2.1 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, I don’t know, delegate red light to priority

medical data. Code Red!

2.2 Airlines:

Airline Wi-Fi. Ugh. 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. It’s better than listening to you tell me about your wildly successful son, ma’am.

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

9

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.

2.4 Undersea Awesomeness:

Underwater ROVs, those favorite 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.

2.2 It Could Keep You Informed and Save Lives

Say there’s an earthquake in New York. Or a hurricane. Take your pick — it’s a

wacky city. The average New Yorker 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. Subway 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.

2.3 USES IN VARIOUS AREAS

Can be used in the places where it is difficult to lay the optical fiber like hospitals. In

operation theatre LiFi can be used for modern medical instruments. In traffic signals LiFi can

be used which will communicate with the LED lights of the cars and accident numbers can be

decreased. Thousand and millions of street lamps can be transferred to LiFi lamps to transfer

data. In aircraft LiFi 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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CHAPTER 3

Genesis of LI-FI:

Harald Haas, a professor at the University of Edinburgh who began his research in the field in

2004, gave a debut demonstration of what he called a Li-Fi prototype at the TED Global

conference in Edinburgh on 12th July 2011. He used a table lamp with an LED bulb to

transmit a video of blooming flowers that was then projected onto a screen behind him.

During the event he periodically blocked the light from lamp to prove that the lamp was

indeed the source of incoming data. At TED Global, Haas demonstrated a data rate of

transmission of around 10Mbps -- comparable to a fairly good UK broadband connection.

Two months later he achieved 123Mbps.

3.1 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

11

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.

To further get a grasp of Li-Fi consider an IR remote. It sends a single data stream of bits at

the rate of 10,000-20,000 bps. Now replace the IR LED with a Light Box containing a large

LED array.

Fig 3.1showing transmission in LI-FI technology

3.2 History:

Professor Harald Haas, from the University of Edinburgh in the UK, is widely recognized as

the original founder of Li-Fi. He coined the term Li-Fi and is Chair of Mobile

Communications at the University of Edinburgh and co-founder of pure LiFi.

12

The general term visible light communication (VLC), includes any use of the visible light

portion of the electromagnetic spectrum to transmit information. The D-Light project at

Edinburgh's Institute for Digital Communications was funded from January 2010 to January

2012. Haas promoted this technology in his 2011TED Global talk and helped start a company

to market it. PureLiFi, formerly pureVLC, is an original equipment manufacturer (OEM) firm

set up to commercialize Li-Fi products for integration with existing LED-lighting systems.

In October 2011, companies and industry groups formed the Li-Fi 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. A number of companies offer uni-directional VLC products which is not the same

as Li-Fi.

VLC technology was exhibited in 2012 using Li-Fi. By August 2013, data rates of over

1.6 Gbps were demonstrated over a single color LED. In September 2013, a press release said

that Li-Fi, or VLC systems in general, do not require line-of-sight conditions. In October

2013, it was reported Chinese manufacturers were working on Li-Fi development kits.

One part of VLC is modeled after communication protocols established by

the IEEE workgroup. However, the IEEE 802.15.7 standard is out-of-date. Specifically, the

standard fails to consider the latest technological developments in the field of optical wireless

communications, specifically with the introduction of optical orthogonal frequency-division

multiplexing (O-OFDM) modulation methods which have been optimized for data rates,

multiple-access and energy efficiency have. The introduction of O-OFDM means that a new

drive for standardization of optical wireless communications is required.

Nonetheless, the IEEE 802.15.7 standard defines the physical layer (PHY) and media access

control (MAC) layer. The standard is able to deliver enough data rates to transmit audio,

video and multimedia services. It takes into account the optical transmission mobility, its

compatibility with artificial lighting present in infrastructures, the devience which may be

caused by interference generated by the ambient lighting. The MAC layer allows to use the

link with the other layers like the TCP/IP protocol.

The standard defines three PHY layers with different rates:

The PHY I was established for outdoor application and works from 11.67 kbit/s to 267.6

kbit/s.

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The PHY II layer allows to reach data rates from 1.25 Mbit/s to 96 Mbit/s.

The PHY III is used for many emissions sources with a particular modulation method

called color shift keying (CSK). PHY III can deliver rates from 12 Mbit/s to 96 Mbit/s.

The modulation formats recognized for PHY I and PHY II are the coding on-off

keying (OOK) and variable pulse position modulation (VPPM). The Manchester coding used

for the PHY I and PHY II layers include the clock inside the transmitted data by representing

a logic 0 with an OOK symbol "01" and a logic 1 with an OOK symbol "10", all with a DC

component. The DC component avoids the light extinction in case of an extended line of

logic 0.

The first Li-Fi smartphone prototype was presented at the Consumer Electronics Show in Las

Vegas from January 7–10 in 2014. The phone uses Sun Partner’s Wysips CONNECT, a

technique that converts light waves into usable energy, making the phone capable of

receiving and decoding signals without drawing on its battery.

Li-Fi, or light fidelity, refers to 5G visible light communication systems using light

from light-emitting diodes (LEDs) as a medium to deliver networked, mobile, high-speed

communication in a similar manner as Wi-Fi. Li-Fi could lead to the Internet of Things,

which is everything electronic being connected to the internet, with the LED lights on the

electronics being used as internet access points. The Li-Fi market is projected to have a

compound of 82% from 2013 to 2018 and to be worth over $6 billion per year by 2018.

Visible light communications (VLC) signals work by switching bulbs on and off

within nanoseconds, which is too quickly to be noticed by the human eye. Although Li-Fi

bulbs would have to be kept on to transmit data, the bulbs could be dimmed to the point that

they were not visible to humans and yet still functional. The light waves cannot penetrate

walls which makes a much shorter range, though more secure from hacking, relative to Wi-

Fi. Direct line of sight isn't necessary for Li-Fi to transmit signal and light reflected off of the

walls can achieve 70 Mbps.

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Fig 3.2 showing use of lifi

Li-Fi has the advantage of being able to be used in electromagnetic sensitive areas such as in

aircraft cabins, hospitals and nuclear power plants without causing electromagnetic

interference. Both Wi-Fi and Li-Fi transmit data over the electromagnetic spectrum, but

whereas Wi-Fi utilizes radio waves, Li-Fi uses visible light. While the US Federal

Communications Commission has warned of a potential spectrum crisis because Wi-Fi is

close to full capacity, Li-Fi has almost no limitations on capacity. The visible light spectrum

is 10,000 times larger than the entire radio frequency spectrum. Researchers have reached

data rates of over 10 Gbps, which is more than 250 times faster than superfast broadband. Li-

Fi is expected to be ten times cheaper and more environmentally friendly than Wi-Fi. Short

range, low reliability and high installation costs are the potential downsides.

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3.3 ‘Li-fi' via LED light bulb data speed break through

UK researchers say they have achieved data transmission speeds of 10Gbit/s via "li-fi" -

wireless internet connectivity using light.

The researchers used a micro-LED light bulb to transmit 3.5Gbit/s via each of the three

primary colours - red, green, blue - that make up white light.

This means over 10Gbit/s is possible. Li-fi is an emerging technology that could see

specialised LED lights bulbs providing low-cost wireless internet connectivity almost

everywhere.

Fig 3.3 Micro-LEDs can transmit large amounts of digital data in parallel

3.4 High speed

The research, known as the ultra-parallel visible light communications project, is a joint

venture between the universities of Edinburgh, St Andrews, Strathclyde, Oxford, and

Cambridge, and funded by the Engineering and Physical Sciences Research Council.

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The tiny micro-LED bulbs, developed by the University of Strathclyde, Glasgow, allow

streams of light to be beamed in parallel, each multiplying the amount of data that can be

transmitted at any one time.

"If you think of a shower head separating water out into parallel streams, that's how we can

make light behave," said Prof Harald Haas, an expert in optical wireless communications at

the University of Edinburgh and one of the project leaders.

Using a digital modulation technique called Orthogonal Frequency Divisional Multiplexing

(OFDM), researchers enabled micro-LED light bulbs to handle millions of changes in light

intensity per second, effectively behaving like an extremely fast on/off switch.

This allows large chunks of binary data - a series of ones and zeros - to be transmitted at high

speed.

Earlier this year, Germany's Fraunhofer Heinrich Hertz Institute claimed that data rates of up

to 1Gbit/s per LED light frequency were possible in laboratory conditions. And this month,

Chinese scientists reportedly developed a microchipped LED bulb that can produce data

speeds of up to 150 megabits per second (Mbps), with one bulb providing internet

connectivity for four computers.

3.5 'Light fidelity'

Prof Harald Haas has been in the forefront of "li-fi" research for the last 10 years

In 2011, Prof Haas demonstrated how an LED bulb equipped with signal processing

technology could stream a high-definition video to a computer.

He coined the term "light fidelity" or li-fi - also known as visual light communications (VLC)

- and set up a private company, PureVLC, to exploit the technology.

Li-fi promises to be cheaper and more energy-efficient than existing wireless radio systems

given the ubiquity of LED bulbs and the fact that lighting infrastructure is already in place.

Visible light is part of the electromagnetic spectrum and its bandwidth is 10,000 times bigger

than the radio frequency spectrum used by existing communication systems, affording vastly

greater capacity. Another advantage, Prof Haas argues, is that evenly spaced LED

17

transmitters could provide much more localised and consistent internet connectivity

throughout buildings.

The disadvantage of traditional wi-fi routers is that the signal weakens the further you are

away from it, leading to inconsistent connectivity within offices and homes.

Prof Haas also believes light's inability to penetrate walls makes VLC technology potentially

more secure than traditional wi-fi connectivity.

LED light bulb 'li-fi' closer, say Chinese scientists

If "li-fi" technology takes off, all LED lights could potentially provide internet connectivity.

Wi-fi connectivity from a light bulb - or "li-fi" - has come a step closer, according to Chinese

scientists.

A microchipped bulb can produce data speeds of up to 150 megabits per second (Mbps), Chi

Nan, IT professor at Shanghai's Fudan University told Xinhua News.

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A one-watt LED light bulb would be enough to provide net connectivity to four computers,

researchers say. But experts told the BBC more evidence was needed to back up the claims.

There are no supporting video or photos showing the technology in action.

Li-fi, also known as visible light communications (VLC), at these speeds would be faster -

and cheaper - than the average Chinese broadband connection.

In 2011, Prof Harald Haas, an expert in optical wireless communications at the University of

Edinburgh, how an LED bulb equipped with signal processing technology could stream a

high-definition video to a computer. He coined the term "light fidelity" or li-fi and set up a

private company, PureVLC, to exploit the technology.

"We're just as surprised as everyone else by this announcement," PureVLC spokesman

Nikola Serafimovski told the BBC.

"But how valid this is we don't know without seeing more evidence. We remain sceptical."

This year, the Fraunhofer Heinrich Hertz Institute claimed that data rates of up to 1Gbit/s per

LED light frequency were possible in laboratory conditions, making one bulb with three

colours potentially capable of transmitting data at up to 3Gbit/s.

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Fig 3.4Edinburgh University's Prof Harald Haas coined the term "li-fi"

3.6 Unlimited capacity

Li-fi promises to be cheaper and more energy-efficient than existing wireless radio systems

given the ubiquity of LED bulbs and the fact that lighting infrastructure is already in place.

Visible light is part of the electromagnetic spectrum and 10,000 times bigger than the radio

spectrum, affording potentially unlimited capacity. But there are drawbacks: block the light

and you block the signal. However, this is also a potential advantage from a security point of

view. Light cannot penetrate walls as radio signals can, so drive-by hacking of wireless

internet signals would be far more difficult, if not impossible.

Prof Chi's research team includes scientists from the Shanghai Institute of Technical Physics

at the Chinese Academy of Sciences, the report says. She admitted that the technology was

still in its infancy and needed further developments in microchip design and optical

communication controls before it could go mass market.

Her team is hoping to show off sample li-fi kits at the China International Industry Fair in

Shanghai on 5 November, the report said.

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CHAPTER 4

How LIFI™ Light Sources Work

4.1 INTRODUCTION

LIFI is a new class of high intensity light source of solid state design bringing clean lighting

solutions to general and specialty lighting. With energy efficiency, long useful lifetime, full

spectrum and dimming,

LIFI lighting applications work better compared to conventional approaches. This technology

brief describes the general construction of LIFI lighting systems and the basic technology

building blocks behind their function.

4.2 LIFI CONSTRUCTION

The LIFI product consists of 4 primary sub-assemblies:

• Bulb

• RF power amplifier circuit (PA)

• Printed circuit board (PCB)

• Enclosure

The PCB controls the electrical inputs and outputs of the lamp and houses the microcontroller

used to manage different lamp functions. An RF (radio-frequency) signal is generated by the

solid-state PA and is guided into an electric field about the bulb. The high concentration of

energy in the electric field vaporizes the contents of the bulb to a plasma state at the bulb’s

center; this controlled plasma generates an intense source of light. All of these subassemblies

are contained in an aluminum enclosure.

4.3 FUNCTION OF THE BULB SUB-ASSEMBLY

At the heart of LIFI is the bulb sub-assembly where a sealed bulb is embedded in a dielectric

material. This design is more reliable than conventional light sources that insert degradable

electrodes into the bulb. The dielectric material serves two purposes; first as a wave guide for

the RF energy transmitted by the PA and second as an electric field concentrator that focuses

21

energy in the bulb. The energy from the electric field rapidly heats the material in the bulb to

a plasma state that emits light of high intensity and full spectrum.

The LIFI product consists of 4 primary sub-assemblies:

• Bulb

• RF power amplifier circuit (PA)

• Printed circuit board (PCB)

• Enclosure

The PCB controls the electrical inputs and outputs of the lamp and houses the micro-

controller used to manage different lamp functions.

4.4 Application of LiFi (Light Fidelity) Technology

Li-Fi found its application in Airways, Green information technology, multi user

communication, Underwater ROV etc. and has many advantages which are discussed in

this project report. Use this report on LiFi only for your study and reference purpose.

The design and construction of the LIFI light source enable efficiency, long stable life, full

spectrum intensity that is digitally controlled and easy to use.

PRESENT SCENARIO:

We have 1.4 million cellular radio waves base stations deployed.

We also have over 5 billions of mobile phones.

Mobile phone transmits more than 600TBb of data.

Wireless communication has become a utility like electricity & water.

We use it in everyday life, in our private life, business life.

Currently wifi uses Radio waves for communication.

It is important to look into this technology which has become fundamental to our

life.

22

Four Issues with Radio Waves:

1. Capacity:

We transmit wireless data through radio waves.

Radio waves are limited, scar and expensive.

We only have a certain range of it.

With the advent of the new generation technologies as of

likes of 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.

Efficiency of such a base station is only 5% and that

raise a very big problem.

3. Availability:

We have to switch off our mobiles in aeroplanes.

It is not advisable to use mobiles at places like

petrochemical plants and petrol pumps.

Availability of radio waves causes another concern.

4. Security:

Radio waves penetrate through walls.

They can be intercepted.

If someone has knowledge and bad intentions then

he may misuse it.

5. Alternative to Radio waves in Electromagnetic Spectrum:

23

So there are four major concerns i.e., capacity, efficiency,

availability, security related with Radio waves.

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

already installed and light is part of electromagnetic

spectrum.

So let’s look up at this in context of EM spectrum.

Fig 4.1 showing electromagnetic spectrum

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

communication.

X-rays are good in hospital and can’t be used either.

Ultra-violet rays are sometimes good for our skin but for long duration it is

dangerous.

Infra-red rays are bad for our eyes and are therefore used at low power levels.

We have already seen shortcomings of radio waves.

So we are left with only Visible light spectrum.

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LI-FI HAS AN UPPERHAND DUE TO PARALLEL DATA

TRANSMISSION

Fig 4.2 showing bits transfer

25

Conclusion

The possibilities are numerous and can be explored further. If his 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. 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

many 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.

26

REFERENCES

[1] www.seminarprojects.com/s/seminar-report-on- lifi

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

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

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

[5] www.lificonsortium.org/

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

[7] en.wikipedia.org/wiki/Li-Fi

[8] www.macmillandictionary.com/buzzword/entries/Li-Fi.html

[9] dvice.com/archives/2012/08/lifi-ten-ways- i.php

[10] Will Li-Fi be the new Wi-Fi? New Scientist, by Jamie Condliffe, dated 28 July 2011

[11] http://www.digplanet.com/wiki/Li-Fi

[12]”Visible-light communication: Tripping the light fantastic: A fast and cheap optical

version of Wi-Fi is coming”, Economist, dated 28Jan 2012.