Department of

ELECTRONICS AND COMMUNICATION ENGINEERING

SEMINAR REPORT SUBMITTED
By
SHANMUGAPRIYAN.P
REGISTER NO: 20TCL010
B.Tech – Seventh Semester
REPORT WORK FOR
EC P73 – SEM

Submitted to
PONDICHERRY UNIVERSITY
PUDUCHERRY
NOVEMBER 2023
 College of Engineering and Technology

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

BONAFIDE CERTIFICATE

This is to certify that this Seminar Report is the bonafide work by

SHANMUGAPRIYAN (20TCL010) who carried out the seminar entitled
“LI-FI” under my supervision from 2023-2024

Co-Ordinator Head of the Department

Mr. S. S. Karthik., Dr. S.ANANDALATCHOUMY.,
M.Tech., M.Tech., Ph.d., M.I.S.T.E.,
Senior Assistant Professor Professor and Head
 ACKNOWLEDGEMENT

My deep sense of gratitude goes to our Chairman & Managing Director

Dr. S. R. S. Paul, who provided all facilities and necessary encouragement during
the course of study. I extended my gratitude and sincere thanks to our beloved
Principal Dr. A. Sivakumar., for his support.

With great pleasure, I would like to express my deep thanks to Professor

Dr. S. Anandalatchoumy., Head of the Department of Electronics and
Communication Engineering for her long-lasting encouragement and
constructive appreciation throughout this seminar work.

I would like to express my unbounded gratefulness to my co-ordinator Professor

S. S. Karthik., Senior Assistant Professor of Electronics and Communication
Engineering for his valuable guidance and encouragement. Also, he has been a
constant source of inspiration and has provided consistent succour and precious
suggestions throughout this seminar work.

I thank all Faculty members and supporting staff for the help they extended, in
completing this seminar work. I also express my sincere thanks to my family
members and all my friends for their continuous support

SHANMUGAPRIYAN. P
 CONTENT

CHAPTER TITLE PAGE NO

1 INTRODUCTION
1.1 INTRODUCTION
1.2 STANDIZATION
1.3 VISUAL LIGHT COMMIUNICATION

2 GENEIES OF LI-FI
2.1 GENEIES OF LIFI
2.2 ISSUES REGRADING RADIO-SPECTRAM
2.3 VLC VS RF COMMUNICATION

3 WORKING OF LI-FI
3.1 WORKING OF LIFI
3.2 TECHNOLOGY BERIF

4 HOW IT DIFFERENT
4.1 HOW IT DIFFERENT
4.2 COMPARISON OF LIFI AND WIFI

5 APPLICATION IN PROBLEM SOLVING

5.1 ECONOMIC VALUE
5.2 LIMITATION
5.3 APPLICATION AREA OF LI-FI TECHNOLOGY

CONCLUSION
REFERENCE
 LIST OF FIGURES
FIG NO DESCRIPTION PAGE NO

A PROF HARLD HASS

B PROTOTYPE OF LI-FI
C BLOCK DIAGRAN OF HOW IT WORK
D HOW IT WORK
E
F AVALANCHE PHOTO DIODE AND SENSOR
G AIRWAYS
H ELECTROMAGNETIC SPECTRUM
I LIGHTING POINT
J SMART POWER PLANT
K UNDER WATER
L TRAFFIC SIGNAL
M NETWORK CONNECTION
N MULTIUSER SUPPORT
O SHADOWING SIGNALS

LIST OF TABLE

TABLE NO DESCRIPTION PAGE NO

1 COMPARISON OF VLC, IR AND RF

COMMUNICATION TECHNOLOGIES
 ABSTRACT
Whether you’re using wireless internet in a coffee shop, stealing it from the guy next door, or
competing for bandwidth at a conference, you’ve 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 many devices access wireless internet, clogged airwaves are going to make it increasingly
difficult to latch onto a reliable signal. But radio waves are just one part of the spectrum that
can carry our data. What if we could use other waves to surf the internet? One German
Physicist, DR. Harald Haas, has come up with a solution he calls “Data Through
Illumination”—taking the fibre out of fiber optics by sending data through an LED light bulb
that varies in intensity faster than the human eye can follow. It’s the same idea behind infrared
remote controls, but far more powerful. Haas says his invention, which he calls D-Light, can
produce data rates faster than 10 megabits per second, which is speedier than your average
broadband connection. He envisions a future where data for laptops, smart phones, and tablets
is transmitted through the light in a room. And security would be a snap—if you can’t see the
light, you can’t access the data.

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 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’.
 1

CHAPTER 1
INTRODUCTION
1.1 Introduction

LiFi (Light Fidelity) is a fast and cheap optical version of Wi-Fi, the technology of which
is based on Visible Light Communication (VLC). 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 wirelesscommunication 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 meters.

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 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 10 Gbps, theoretically allowing a high-definition film to be downloaded in 30
seconds.
 2

In simple terms, Li-Fi can be thought of as a light-based Wi-Fi. That is, it uses light instead
of radio waves to transmit information. And instead of Wi-Fi modems, Li-Fi would use
transceiver-fitted LED lamps that can light a room as well as transmit and receive
information. Since simple light bulbs are used, there can technically be any number of
access points.

This technology uses a part of the electromagnetic spectrum that is still not greatly
utilized- The Visible Spectrum. Light is in fact very much part of our lives for millions
and millions of years and does not have any major ill effect. Moreover, there is 10,000
times more space available in this spectrum and just counting on the bulbs in use, it also
multiplies to 10,000 times more availability as an infrastructure, globally.

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 eyes cannot notice, so the output appears constant.

Li Fi is now part of Visible Light Communication (VLC) PAN IEEE 802.15.7 Standard.
More sophisticated techniques could dramatically increase VLC data rates. Team of
scientists including Dr. Gorden Povey, Prof. Harald Hass and Dr. Mostafa Afgani at
University of Edinburgh and the University of Oxford are focusing on parallel data
transmission using arrays 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's frequency,
with each frequency encoding a different data channel.

Li-Fi, as it has been dubbed, has already achieved blisteringly high speeds 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. Haas has set up a spin-
off firm to sell a consumer VLC transmitter that is due for launch next year. It is capable
of transmitting data at 100 MB/s - faster than most UK broadband connections. Li-Fi
stands for ‘Light Fidelity’.

Li-Fi is the terms have been used to label the fast and cheap wireless communication
system, which is the optical version of Wi –Fi.

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
 3

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.

1.2 Standardization

VLC communication is modeled after communication protocols established by the IEEE

802 workgroup. This 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 count of the optical transmission mobility, its
compatibility with artificial lighting present in infrastructures, the defiance which may be
caused by interference generated by the ambient lighting. The MAC layer allows using
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.

• 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 modulations 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. This is an important point because the DC component allows to avoid the
light extinction in case of an extended line of logic 0.

The Li-Fi Consortium has also been established to work on standardizing VLC
communications, but the rapid evolution of the technology minimizes the impact of any
standardization effort. Both the IEEE 802 workgroup and the Li-Fi Consortium fail to
account for the emergence of optical orthogonal frequency division multiplexing
 4

(O-OFDM) systems which provide significant benefits with regard to data rates, multiple-
access and energy efficiency.

1.3 Visible Light Communications

“Visible light Communication (VLC) is a modern communication technology which

employs visible solid-state light sources (LEDs) for transmitting data wirelessly as they
are used for general illumination at the same time."

VLC Characteristics

The merits and demerits of this technology become apparent once we go through the
characteristics of visible light communication technology:

Human Safety: VLC poses no health hazards to human body. Thus, the transmission
power can be kept high if needed.

High Data Rates: VLC inherits high data rates from optical communications. Thus, it can
be used for very high speed wireless communications.

Bandwidth: Visible light communications exploits the visible region of electromagnetic

spectrum. Thus it much larger frequency band ( 300 THz) compared to that available in
RF communications ( 300GHz).

Ubiquitous Nature: We have a well-established lighting infrastructure throughout the

world. In addition to it, LED based lighting devices are getting widespread acceptance
round the globe. Since VLC uses the already available visible light sources for wireless
communications, so it is expected to become a ubiquitous technology in near future.

Security: As VLC involves line of sight communication, so it is impossible to tap the

communication without breaking the link. So it a very secure communication and can be
used in high security military areas where RF communication is prone to eavesdropping.

Visibility: It is aesthetically pleasing to see data being communicated by colored lights.

Thus, VLC is also used in many entertainment related activities like silent concerts,
decoration systems, etc.

Unlicensed Spectrum: As VLC uses the visible region of electromagnetic spectrum, so it

is free of cost. Contrary to it, the RF communication band is regulated
 5

Fig:1.1 Prof. Harald Haas

Li-Fi technology represents a groundbreaking approach to wireless communication,

harnessing the power of light to transmit data at unprecedented speeds. With its potential to
revolutionize various industries and address the limitations of traditional wireless
technologies, Li-Fi is a technology to watch as it continues to evolve and find its place in the
rapidly advancing landscape of connectivity.

Li-Fi's potential applications extend beyond traditional wireless communication scenarios. In

environments where radio frequency communication is restricted, such as hospitals or aircraft,
Li-Fi could offer a viable solution. Its use in underwater communication is also being explored,
as radio waves are quickly attenuated in water, while light can travel more effectively.
 6

CHAPTER 2
GENESIS OF LI-FI

2.1 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.

Fig 2.1: Li-Fi Prototype

 7

At the heart of Li-Fi's brilliance is its ability to achieve unprecedented data transfer speeds.
Unlike traditional Wi-Fi, which relies on radio waves, Li-Fi utilizes the visible light spectrum.
Light waves inherently have higher frequencies than radio waves, allowing for significantly
faster data transmission. The potential data transfer rates of Li-Fi can reach several gigabits per
second, enabling near-instantaneous communication and data exchange. This speed advantage
positions Li-Fi as a frontrunner in meeting the escalating demands of our data-centric world.

Another key aspect of Li-Fi's genius is its capacity to address the issue of spectrum congestion.
With the proliferation of wireless devices, Wi-Fi networks are increasingly contending for
space within the limited radio frequency spectrum. This congestion leads to interference and
diminished performance. Li-Fi operates in the vast and relatively unexplored realm of the
visible light spectrum, offering a larger bandwidth and reduced interference. This not only
enhances the efficiency of data transmission but also mitigates the challenges associated with
crowded frequency bands.

Li-Fi's ingenious integration of LED technology further underscores its brilliance. Light-
emitting diodes serve a dual purpose in Li-Fi setups, providing illumination while
simultaneously serving as data transmitters. This dual functionality is not only efficient but also
environmentally friendly, as it capitalizes on the widespread adoption of energy-efficient LED
lighting. The seamless integration of communication technology into existing lighting
infrastructure is a testament to the elegance of Li-Fi's design.

The security features embedded in Li-Fi contribute to its genius, addressing concerns
associated with data privacy and interception. The nature of light waves restricts Li-Fi's signal
propagation, making it challenging for unauthorized users to intercept data without physical
access to the light source. In environments where security is paramount, such as government
facilities or financial institutions, Li-Fi's inherent resistance to signal leakage through walls
provides a valuable layer of protection.
 8

Li-Fi's versatility and adaptability showcase its genius in meeting diverse communication
needs. While it excels in scenarios where high-speed data transfer is crucial, such as in
streaming high-definition videos or supporting virtual reality applications, Li-Fi also
demonstrates promise in specialized environments. Its potential applications in healthcare,
underwater communication, and secure facilities where traditional wireless technologies face
limitations highlight the broad spectrum of possibilities that Li-Fi opens.

Despite its brilliance, Li-Fi is not without challenges. The line-of-sight limitation, where the
receiver must be in direct view of the transmitter, poses hurdles in certain scenarios.
Researchers are actively exploring solutions, including the use of multiple light sources and
advanced tracking mechanisms, to overcome this limitation and expand the practical
applications of Li-Fi.

In conclusion, the genius of Li-Fi technology lies in its innovative use of light to transmit data,
offering unparalleled speed, enhanced security, and adaptability to diverse communication
needs. Professor Harald Haas's pioneering work in introducing and advancing Li-Fi has
sparked a wave of exploration and excitement in the realm of wireless communication. As Li-
Fi continues to evolve, its genius holds the promise of transforming the way we connect and
communicate in the digital age.

2.2 Issues Regarding Radio-spectrum

Radio Spectrum is congested but the demand for wirelesses data double each year. Everything,
it seems want to use wireless data but the capacity is drying up.

Capacity: In LI-FI the Bandwidth is 10000 times more than radio wave. That provides huge
range of spectrum bandwidth.

Efficiency: Millions of base stations for radio wave transmission and receiving on the earth
consume huge amount of energy for transmitting the radio waves and to cool the base station
cabins. It gives only 5% Efficiency. In case of LI-FI it does not consume energy as compare to
other waves. It is very cheap.
 9

Availability: Radio waves are available within the range of Base stations which make it limited
availability. It is unavailable in aircrafts because of interference of wave cause crash. But LI-
Fi does not produce interference and provide user a perfect communication channel for
accessing internet telephone, watching movies online.

Security: Radio wave penetrates walls which cause security laps. Any one access to the private
network of any one and use their data, login to their secure region.

2.3 VLC vs RF Communication

• Limited Transmission Power: In RF communications, the electric transmission power cannot

be increased beyond a prescribed level as it poses serious health hazards for human body.

• Regulated Spectrum: Due to the radio wave restriction, there is no room to use more radio
frequencies. In addition, the use of radio spectrum is regulated.

• Banned in Sensitive Areas: The radio wave cannot be used in hospitals and Space stations
because it adversely acts the performance of precision instruments. These radio wave problems
above are easily solved by use of the visible light communications.

All these problems can be solved using visible light communications. This can be accredited
to the high available bandwidth, high data rates, high transmission power, health-friendly
operation and lower implementation costs of this technology.
 10

CHAPTER 3

WORKING OF LI-FI

3.1 WORKING OF LI-FI

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
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,
 11

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 Is and Os. 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.

Fig: Block diagram of How it Work

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

 12

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. 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.

fig: How it works

 13

3.2 TECHNOLOGY BRIEF

LI-FI CONSTRUCTION:

The LI-FI™ 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 sub assemblies are contained in an aluminum enclosure.

Transmitters:

The following components are used at the transmitting side

1. Coloured LEDs

2. Mosfets

3. RS232 line driver IC

4. USB to RS232 converter cable

5. Voltage Regulator

• Coloured LEDs

An array of Red, Green and Blue LEDs are used at the transmitter end as visible light sources.
They are connected as loads in the transistor circuitry. They are high power and emit a focused
beam. Each col or is used to carry a different data stream.
 14

• MOSFETs

A high speed N-type power MOSFET IRF 520 is used to modulate the LEDs using OOK (On
off Keying). The serial output from the computer is converted into TTL Compatible form and
is then applied to the gate of the transistor. Thus, it switches the load (LEDs) on and off in
accordance with the input data 4.3.1.3 RS232 line driver.

Since the output of computer is RS232 compatible, a 16 pin RS232 line driver IC MAX 232 is
used to make the computer output TTL level compatible to drive the transistor circuit carrying
through LED load.

• USB to RS232 converter cable

In laptops, serial port is not available. Since data is to be transmitted serially between the two
computers, a USB to RS232 converter cable is used to interface the serial output from MAX
232 IC to the laptop using the built-in USB port. This cable contains an embedded controller
to conform the RS232 compatible data into USB protocol compatible form.

• Voltage Regulator

A voltage regulator is used to supply constant voltage (5V) to MAX232 IC. A 3 pin 7805 IC
is used to serve the purpose.

Every kind of light source can theoretically be used as transmitting device for VLC. However,
some are better suited than others. For instance, incandescent

lights quickly break down when switched on and o_ frequently. These are thus not
recommended as VLC transmitters. More promising alternatives are fluorescent lights and
LEDs. VLC transmitters are usually also used for providing illumination of the rooms in which
they are used. This makes fluorescent lights a particularly popular choice, because they can
flicker quickly enough to transmit a meaningful amount of data and are already widely used
for illumination purposes. However, with an ever-rising market share of LEDs and further
technological improvements such as higher brightness and spectral clarity. LEDs are expected
to replace fluorescent lights as illumination sources and VLC transmitters. The simplest form
of LEDs is those which consist of a bluish to ultraviolet LED surrounded by phosphorus which
is then stimulated by the actual LED and emits white light. This leads to data rates up to 40
Mbit/s. RGB LEDs do not rely on phosphorus any more to generate white light. They come
with three distinct LEDs (a red, a blue and a green one) which, when lighting up at the same
 15

time, emit light that humans perceive as white. Because there is no delay by stimulating
phosphorus rust, Data rates of up to 100 M Bit/s can be achieved using RGB LEDs. In recent
years the development of resonant cavity LEDs (RCLEDs) has advanced considerably. These
are similar to RGB LEDs in that they are comprised of three distinct LEDs, but in addition they
are fitted with Bragg mirrors which enhance the spectral clarity to such a degree that emitted
light can be modulated at very high frequencies. In early 2010, Siemens has shown that data
transmission at a rate of 500MBit/s is possible with this approach.

It should be noted that VLC will probably not be used for massive data transmission. High data
rates as the ones referred to above, were reached under meticulous Set ups which cannot be
expected to be reproduced in real-life scenarios. One can expect to see data rates of about 5
kbit/s in average applications, such as location estimation. The distance in which VLC can be
expected to be reasonably used ranges up to about 6 meters.

Fig: Solid state LED and fluorescent bulb used as transmitted

Receivers:

The following components are used at the receiving side:

1. Optical Receiver

2. Optical Filters

3. Voltage Regulator
 16

4. RS232 line driver IC

5. USB to RS232 converter cable

• Optical Receiver: A 6 pin fiber optic receiving module TORX 173 is used as the light
sensing device. On receiving light pulses, it gives a high output whereas the output goes low
in the absence of light.

• Optical Filters: Red, green and blue light filters are used at the receiver to de
multiplex the multiple data streams. These are sharp narrowband filters. A red light filter allows
the frequency band corresponding to red colour to pass through it and blocks all other
wavelengths. Thus, when a red-light filters is placed in front of the optical receiver, only the
data stream carried by the red beam falls at the receiver while the other streams are blocked.
Similarly, blue or green light filters can be used to allow the desired data stream to reach the
receiver.

• Voltage Regulator: A voltage regulator is used to supply constant voltage (5V) to

TORX 173.A 3 pin 7805 IC is used to serve the purpose.

• RS232 line driver: Since the output of TORX 173 is TTL level compatible, a 16 pin
RS232 line driver IC MAX 232 is used to make the output RS232 compatible so that the
receiving module can be interfaced to the computer.

• USB to RS232 converter cable: In laptops, serial port is not available. Since data is
to be transmitted serially between the two computers, a USB to RS232 converter cable is used
to interface the serial output from MAX 232 IC to the laptop using the built-in USB port. This
cable contains an embedded controller to conform the RS232 compatible data into USB
protocol compatible form

The most common choice of receivers are photodiodes which turn light into electrical
pulses. The signal retrieved in this way can then be demodulated into actual data. In more
complex VLC-based scenarios, such as Image Sensor Communication even CMOS or CCD
sensors are used (which are usually built into digital cameras).
 17

Fig: Receiver such as Avalanche Photo Diode and Image sensor

Modulation:

In order to actually send out data via LEDs, such as pictures or audio files, it is necessary to
modulate these into a carrier signal. In the context of visible light communication, this carrier
signal consists of light pulses sent out in short intervals.

How these are exactly interpreted depends on the chosen modulation scheme, two of which
will be presented in this section. At first, a scheme called subcarrier pulse position modulation
is presented which is already established as VLC-standard by the VLCC. The second
modulation scheme to be addressed is called frequency shift Keying, commonly referred to as
FSK. They also explore how to combine pulse-position modulation with illumination control.
 18

CHAPTER 4

HOW IT’S DIFFERENT?

4.1 How It’s Different?

LI-FI technology is base on LEDs for transfer of data. The transfer of data can be with the help
of all kinds of light can belong to the invisible, ultraviolet or the visible part of the spectrum.
The speed of internet is incredibly high and we can download movies, games, music etc in just
a few minutes with the help of this technology. Also, this technology removes limitation that
has been put on the user by the Wi-Fi. We don’t need to in a region that is WI-FI enabled to
have access to the internet. We 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.

Another notable difference is the availability of the spectrum. The radiofrequency spectrum,
which Wi-Fi operates on, is becoming increasingly crowded as more devices connect to
wireless networks. This congestion can lead to interference and reduced performance. Li-Fi,
on the other hand, taps into the vast and unutilized spectrum of visible light, providing a
potentially less congested and more reliable communication channel.

Li-Fi technology also offers enhanced security features. Since light waves don't pass through
walls like radio waves do, Li-Fi signals are more contained and less susceptible to unauthorized
access from outside a physical space. This characteristic makes Li-Fi inherently more secure
for certain applications, such as in environments where data confidentiality is critical.

Additionally, Li-Fi can be particularly beneficial in areas where electromagnetic interference

is a concern. Places like hospitals and aircraft cabins, where radiofrequency signals can
interfere with sensitive equipment, could potentially benefit from Li-Fi's interference-free
nature.

However, it's essential to acknowledge the limitations of Li-Fi. One of the primary challenges
is its range and coverage. Li-Fi signals are confined to the range of the light source, making
them suitable for localized communication within a room or specific area. This limitation
contrasts with Wi-Fi, which can cover larger spaces.
 19

Moreover, Li-Fi requires a direct line of sight between the transmitter and receiver, hindering
its ability to penetrate obstacles. This characteristic makes Li-Fi less practical for scenarios
where seamless mobility is crucial.

In conclusion, Li-Fi's differentiation from other technologies stems from its use of visible light
for data transmission, offering higher speeds, increased security, and reduced interference
compared to traditional Wi-Fi. While it presents exciting possibilities for specific use cases, its
limitations, such as range and line-of-sight requirements, highlight the need for careful
consideration of its application in various scenarios. As technology continues to evolve, Li-Fi
may find niche roles alongside existing wireless communication technologies.

4.2 COMPARISON OF LI-FI AND WIFI

Wi-Fi and Li-Fi are two distinct wireless communication technologies, each with its own set
of characteristics, advantages, and limitations. Let's explore a compressed comparison of Wi-
Fi and Li-Fi:

Medium of Transmission:

Wi-Fi: Uses radio waves in the 2.4 GHz and 5 GHz frequency bands for data transmission.

Li-Fi: Utilizes visible light waves, typically through LED bulbs, for data communication.

Data Transfer Speed:

Wi-Fi: Offers data transfer speeds ranging from several megabits to gigabits per second.

Li-Fi: Can achieve higher data transfer speeds, potentially reaching several gigabits per
second, owing to the higher frequency of visible light.

Interference and Congestion:

Wi-Fi: Susceptible to interference and congestion, especially in densely populated areas due
to shared radio frequency spectrum.

Li-Fi: Operates in the less crowded visible light spectrum, reducing interference and
congestion issues.
 20

Security:

Wi-Fi: Uses encryption protocols for security but may be susceptible to unauthorized access
and signal interception.

Li-Fi: Offers enhanced security as light waves do not penetrate through walls easily, making
it more challenging for unauthorized users to intercept data.

Range:

Wi-Fi: Typically has a longer range compared to Li-Fi, with signals capable of penetrating
walls.

Li-Fi: Relies on line-of-sight communication, and its range is limited by obstacles blocking
the light path.

Environmental Impact:

Wi-Fi: Requires dedicated radio frequency infrastructure, which may contribute to

electromagnetic pollution.

Li-Fi: Can be integrated with existing LED lighting infrastructure, promoting energy
efficiency and reducing the need for separate communication hardware.

Practical Applications:

Wi-Fi: Widely used for general wireless networking in homes, offices, and public spaces.

Li-Fi: Shows potential in scenarios requiring high-speed and secure data transfer, such as
hospitals, aircraft, and environments where radio frequency communication faces challenges.

Limitations:

Wi-Fi: Vulnerable to interference, congestion, and security concerns.

Li-Fi: Limited by line-of-sight communication, necessitating solutions for scenarios with

obstacles or moving devices.
 21

Table : Comparison of VLC, IR and RF communication technologies

 22

CHAPTER 5
APPLICATION IN PROBLEM SOLVING

5.1 Economic value

• A free band that does not need license.
• High installment cost but very low maintenance cost.
• Cheaper than Wi-Fi.
• Theoretical speed up to 1 GB per second : Less time & energy consumption.
• No more monthly broadband bills.
• Lower electricity costs.
• Longevity of LED bulb: saves money.
• Light doesn't penetrate through walls: secured access.

5.2 Limitations
The main problem is that light can't pass through objects, so if the receiver is inadvertently
blocked in any way, then the signal will immediately cut out. "If the light signal is blocked, or
when you need to use your device to send information -- you can seamlessly switch back over
to radio waves", Harald says. Reliability and network coverage are the major issues to be
considered by the companies while providing VLC services.

Interferences from external light sources like sun light, normal bulbs; and opaque materials in
the path of transmission will cause interruption in the communication. High installation cost of
the VLC systems can be complemented by large-scale implementation of VLC though
Adopting VLC technology will reduce further operating costs like electricity charges,
maintenance charges etc.

5.3 Application area of LI-FI technology:

It can be used in the places where it is difficult to lay the optical fibres like hospitals. In
operation theatre Li Fi can be used for modern medical instruments.

Airways
 23

Whenever we travel through airways we face the problem in communication media, because
the whole airways communication are performed on the basis of radio waves. To overcome this
drawback on radio wave, li-fi is introduced.

Fig: Airways

Green information technology

Green information technology means that unlike radio waves and other communication waves
affects on the birds, human body etc. Li-Fi never gives such side effects on any living thing

Increase Communication Safety:-

Due to visual light communication, the node or any terminal attach to our network is visible
to the host of network.

Multi User Communication:-

Li-Fi supports the broadcasting of network; it helps to share multiple things at a single instance
called broadcasting.
 24

Free From Frequency Bandwidth Problem:-

Li-fi is a communication media in the form of light, so no matter about the frequency bandwidth
problem. It does not require the any bandwidth spectrum i.e. we don’t need to pay any amount
for communication and license.

Fig: Electromatic spectrum

It Could Keep You Informed and Save Lives

Say there’s an earthquake or a hurricane. Take your pick — it’s a wacky city. The average
people 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. It can be used in petroleum or chemical plants where other transmission or frequencies
could be hazardous.

Lightings Points Used as Hotspot in Smart Homes and Offices: Any lightings device is
performed as a hotspot it means that the light device like car lights, ceiling lights, street lamps
etc area able to spread internet connectivity using visual light communication. This helps us
 25

to low cost architecture for hotspot. Hotspot is a limited region in which some amount of
device can access the internet connectivity.

Fig: Lighting point

Secure Communication:
Li-Fi is more secure than Wi-Fi because light waves cannot penetrate walls, reducing the risk
of unauthorized access. This makes it suitable for applications where data security is crucial.

Education:
Implementing Li-Fi in educational institutions can provide high-speed internet access to
students while ensuring a secure and controlled network environment.

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, interconnected 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
 26

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.

Fig: Smart power plant

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 free 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.

Light propagates better in water compared to radio waves, which are quickly absorbed. Li-Fi
takes advantage of this property to achieve more reliable and efficient data transmission
underwater.
 27

Li-Fi technology can be employed for underwater environmental monitoring, allowing

researchers to gather data on ocean conditions, marine life, and other parameters with increased
accuracy and efficiency.

Fig: Underwater
Traffic Signals In traffic signals Li Fi 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 Li-Fi lamps to transfer data.

Fig: Traffic signal

 28

5.4 Challenging Problems

Connectivity while moving

Multiuser support

Dimming

Shadowing

Limited Range and Coverage:

One of the significant challenges facing Li-Fi is its limited range and coverage. Light waves
cannot penetrate solid objects, limiting the effective range of Li-Fi signals. Overcoming this
challenge requires strategic placement of Li-Fi transmitters to ensure sufficient coverage in
larger areas.

Line-of-Sight Communication:

Li-Fi communication relies on a direct line of sight between the transmitter and receiver.
Obstacles such as walls or physical barriers can disrupt the signal, posing a challenge for
widespread adoption, especially in environments where maintaining a clear line of sight is
difficult.

Interference from Ambient Light:

Ambient light sources, such as sunlight or strong indoor lighting, can interfere with Li-Fi
signals. This interference may impact the reliability of communication, especially in
environments where controlling ambient light conditions is challenging.

Standardization and Compatibility:

Establishing global standards for Li-Fi technology is crucial for its widespread adoption.
Currently, there is a need for standardized protocols to ensure compatibility between different
Li-Fi devices and networks, facilitating seamless integration and interoperability.
 29

Cost of Implementation:

While Li-Fi can leverage existing lighting infrastructure, the initial cost of implementing Li-
Fi technology, including the installation of compatible LED bulbs and transmitters, may be a
barrier to widespread adoption. As the technology matures and economies of scale come into
play, the cost is expected to decrease.

5.5 Solutions to Challenging problem

Solution for connectivity This problem is similar to the connectivity problem in cellular
network when you move from one area of the city to another area while speaking with cell-
phone. The solution is called “handover”, using which the user is transferred from one BS to
another Handover is done in the area that two BS’s have common coverage. Similar solution
can be used in signal processing domain for VLC. The user can be transferred from one light
source to another in the area that is under the coverage of both

Fig: Network connection

Solution for multiuser support

In this problem one solution is time division multiplexing (TDM). Each frame is divided into
equal time slots. Each user transmits data in one time slot in a predefined order. The other
solution is code division multiple access (CDMA). Codes are assigned to users. Each user
transmits its data using the assigned signature pattern.
 30

It is used in 3G and 4G cellular networks. CDMA has been adopted and developed for optical
systems. Optical orthogonal codes (OOC) are used as signature pattern for users.

Fig: Multiuser support

Solution for shadowing

As shown before, the impulse response in VLC systems has two parts. When the line-of-sight
(LOS) part (which is received via direct path) is blocked, the impulse response is only the
second part. Then the data can be recovered using the second part which is indeed the received
data from the indirect paths (multipath signal

Fig: shadowing signals

 31

High Data Transfer Rates:

One of Li-Fi's primary advantages is its potential for significantly higher data transfer rates
compared to Wi-Fi. The use of light waves allows for faster communication, making Li-Fi an
ideal solution for scenarios where high-speed data transmission is crucial, such as in dense
urban environments or data-intensive applications.

Reduced Electromagnetic Interference:

Li-Fi operates in the visible light spectrum, reducing the electromagnetic interference that
Wi-Fi can experience from other electronic devices. This can result in a more stable and
reliable wireless communication environment, particularly in settings with numerous
electronic devices.

Enhanced Security:

Li-Fi offers improved security as light waves do not pass through walls, making it harder
for unauthorized users to intercept the signal. This characteristic makes Li-Fi particularly
attractive for applications where data security is paramount, such as in financial transactions
or sensitive data transfer.

Utilization in Radio-Frequency Sensitive Environments:

Li-Fi can be deployed in environments where radio frequency transmissions are restricted
or prohibited, such as in hospitals or aircraft. Its use of light waves instead of radio waves
enables communication without interfering with critical RF-sensitive equipment.

Integration with Existing Lighting Infrastructure:

Li-Fi technology can be seamlessly integrated into existing lighting infrastructure, allowing
for cost-effective deployment. This ease of integration makes Li-Fi an attractive option for
retrofitting buildings and upgrading communication capabilities without extensive
infrastructure changes
 32

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 ϯϳ 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.
 33

REFERENCES
1. en.wikipedia.org/wiki/Li-Fi
2. teleinfobd.blogspot.in/2012/01/what-is-lifi.html
3. technopits.blogspot.comtechnology.cgap.org/2012/01/11/a-lifi-world/
4. www.lificonsortium.org/
5. the-gadgeteer.com/2011/08/29/li-fi-internet-at-thespeed-of-light/
6. www.macmillandictionary.com/buzzword/entries/Li-Fi.html
7. dvice.com/archives/2012/08/lifi-ten-ways-i.php
8. Will Li-Fi be the new Wi-Fi?, New Scientist, by Jamie Condliffe, dated 28 July 2011
9. http://www.digplanet.com/wiki/Li-Fi
10.” Visible-light communication: Tripping the light 11. fantastic: A fast and cheap optical
version of Wi-Fi is coming”, Economist, dated 28Jan 2012