Li-Fi is a new wireless technology which provides the connectivity within localized network environment. The main principle of this technology is we can transmit the data using light illumination by using light emitting diodes where radio frequency is media in Wi-Fi and LED bulb light intensity is faster than human eye can follow. One germen phycist-Prof Harald Haas an expert in optical wireless communications at the University of Edinburgh, he demonstrated how an LED bulb equipped with signal processing technology could stream a high-definition video to a computer. By using this technology a one-watt LED light bulb would be enough to provide net connectivity to four computers. He coined the term "light fidelity" or Li-Fi. He visualizes a future where data for laptops, Smartphone, and tablets is transmitted through the light in a room. This technology is still under research and further exploitation could lead to wide applications.
Seminar Report On
“DATA TRANSMISSION THROUGH
Submitted In Partial Fulfillment of the Requirement
For The Award of Degree of Bachelor of Engineering
In Computer Science & Engineering
North Maharashtra University, Jalgaon
Mr. Pravin Ahirwar
Computer Science & Engineering
Shri Sant Gadge Baba
College of Engineering and Technology, Bhusawal
North Maharashtra University, Jalgaon
Shri Sant Gadge Baba
College of Engineering and Technology,
This is to certify that Mr. Pravin Ahirwar has successfully completed
his seminar on “Data Trnsmission Through Illumination” for the partial
fulfillment of the Degree of Bachelor of Engineering in the Computer
Science & Engineering as prescribed by the North Maharashtra University,
Jalgaon during academic year 2014-15.
Guide H.O.D Principal
I feel great pleasure in submitting this Special Study report on “DATA
TRANSMISSION THROUGH ILLUMINATION”. I wish to express true sense of
gratitude towards my Special Study guide, Prof. R.R SINGH who at very discrete step in
study of this Special Study contributed his valuable guidance and help to solve every problem
I would wish to thank our H.O.D., PROF. D. D. PATIL for opening the doors of the
information towards the realization of this Special Study.
Most likely I would like to express my sincere gratitude towards my family for
always being there when I needed them the most. With all respect and gratitude, I would like
to thank all the people, who have helped me directly or indirectly. I owe my all success to
Li-Fi is a new wireless technology which provides the connectivity within
localized network environment. The main principle of this technology is we can transmit
the data using light illumination by using light emitting diodes where radio frequency is
media in Wi-Fi and LED bulb light intensity is faster than human eye can follow. One
germen phycist-Prof Harald Haas an expert in optical wireless communications at the
University of Edinburgh, he demonstrated how an LED bulb equipped with signal
processing technology could stream a high-definition video to a computer. By using this
technology a one-watt LED light bulb would be enough to provide net connectivity to
four computers. He coined the term "light fidelity" or Li-Fi. He visualizes a future where
data for laptops, Smartphone, and tablets is transmitted through the light in a room. This
technology is still under research and further exploitation could lead to wide applications.
Keywords: Wireless, Li-Fi, Wi-Fi, LED, VLC.
Title Page No.
List of figures ii
1 Introduction 1
2 Literature Review 4
2.1 History 4
2.2 Review of papers 5
3 Principle of LIFI 7
4 Construction of Li-Fi System 8
5 Data transmission through Li-Fi 10
5.1 Working 11
6 Communication with VLC 12
7 Issues with Radio Waves 14
Alternative to radio waves in electromagnetic
8. Overcoming the issues of radio waves 16
9. VLC modulation techniques 17
9.1 On Off Keying(OOK) 17
9.2 Pulse With Modulation (PWM) 17
9.3 Pulse Position Modulation (PPM) 17
9.4 Variable Pulse Position Modulation(VPPM) 17
9.5 Color Shift Keying(CSK) 17
9.6 Orthogonal Frequency division Multiplex(OFDM) 18
9.7 Spatial Modulation(SM) 18
10 Comparison between Li-fi and Wi-Fi 19
11 Advantages of Li-Fi 20
12 Limitations Of Li-Fi 21
13 Application of Li-Fi 22
13.1 Education systems 22
13.2 Medical Application 22
13.3 Cheaper Internet in Aircrafts 22
13.4 Underwater Application 22
13.5 Disaster Management 23
13.6 Application in sensitive areas 23
13.7 Traffic Management 23
13.8 GPS Usage 23
13.9 Replace for other technologies 24
14 Future Scope 25
15 Conclusion 26
LED Light-Emitting Diode
LI-FI Light Fidelity
WI-FI Wireless Fidelity
VLC Visible Light Communication
RF Radio Frequency
OEM Original Equipment Manufacturer
PCB Printed Circuit Board
DDL Data Link Layer
MAC Media Access Control
OSI Open Systems Interconnection
OOK On Off Keying
PWM Pulse Width Modulation
PPM Pulse Position Modulation
VPPM Variable Pulse Position Modulation
CSK Color Shift Keying
OFMD Orthogonal Frequency Division Multiplex
SM Spatial Modulation
LIST OF FIGURES
Figure No. Title of Figure
3.1 Example Of VLC
4.1 Block Diagram Of Li-Fi Sub Assemblies
4.2 Shows The Bulb Sub Assemblies
5.1 Working Of Li-Fi
6.1 OSI Reference Model For VLC Communication
7.1 Electromagnetic Spectrum
LIST OF TABLES
Table No. Title of Table
10.1 Comparison Between Li-Fi And Wi-Fi
Now a day’s Wi-Fi is widely used in all the public areas like home, cafes, hotels,
airports. Due to this radio frequency is getting blocked day by day, at the same time usage
of wireless data is increasing exponentially every year. Everyone is interested to use
wireless data but the capacity is going down. Wireless radio frequencies are getting
higher, complexities are increasing and RF interferences continue to grow. In order to
overcome this problem in future, light –fidelity (Li-Fi) technology came into existence
since 2011. Li-Fi is a wireless communication system in which light is used as a carrier
signal instead of traditional radio frequency as in Wi-Fi. Li-Fi is a technology that uses
light emitting diodes to transmit data wirelessly. Visible light communication (VLC) uses
rapid pulses of light to transmit information wirelessly that cannot be detected by human
eye. This paper will focus on Li-Fi technology over Wi-Fi technology and challenges for
the new VLC technology.
Li-Fi can produce data rates faster than 10 megabits per second which is speedier than
your average broadband connection .
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.More sophisticated
techniques could dramatically increase VLC data rates. Teams at the University of
Oxford and the University of Edinburgh 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.
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 2011 TED 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.
LiFi is a wireless optical networking technology that uses light-emitting diodes
(LEDs) for data transmission. LiFi is designed to use LED light bulbs similar to those
currently in use in many energy-conscious homes and offices. However, LiFi bulbs are
outfitted with a chip that modulates the light imperceptibly for optical data transmission.
LiFi data is transmitted by the LED bulbs and received by photoreceptors. LiFi's early
developmental models were capable of 150 megabits-per-second (Mbps). Some
commercial kits enabling that speed have been released. In the lab, with stronger LEDs
and different technology, researchers have enabled 10 gigabits-per-second (Gbps), which
is faster than 802.11ad. ―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. 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. 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.
In addition, Wi-Fi may not be the most efficient way to provide new desired capabilities
such as precision indoor positioning and gesture recognition. The use of the visible light
spectrum for high speed data communication is enabled by the emergence of the light
emitting diode (LED) which at the same time is at the heart of the next wave of energy-
efficient illumination. Terms at the University of Oxford and the University of Edinburgh
are focusing on parallel data transmission using array of LEDs, where each LED
transmits a different data stream. Other groups are using mixtures of red, green and blue
LEDs to alter the light frequency encoding a different data channel.
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. The vision is that a Li-Fi wireless network would complement existing
heterogenous RF wireless networks, and would provide significant spectrum relief by
allowing cellular and wireless-fidelity (Wi-Fi) systems to off-load a significant portion of
wireless data traffic. Optical wireless technologies, sometimes called visible light
communication (VLC), and more recently referred to as Li-Fi (Light Fidelity), on the
other hand, offer an entirely new paradigm in wireless technologies in terms of
communication speed, flexibility and usability.
2. LITERATURE SURVEY
Professor Harald Haas, from the University of Edinburgh in the UK, who began
his research in the field in 2004. He coined the term Li-Fi and is Chair of Mobile
Communications at the University of Edinburgh and co-founder of pureLiFi.
The general term visible light communication (VLC), includes any use of the
visible light portion of the electromagnetic spectrum to transmit information. 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
He 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.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 Gbit/s 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.In April 2014, the Russian company Stins Coman announced the
development of a Li-Fi wireless local network called BeamCaster. Their current module
transfers data at 1.25 gigabytes per second but foresee boosting speeds up to 5 GB/second
in the near future .
2.2 REVIEW OF PAPERS
A. H. Elgala , "A Study on the Impact of Nonlinear Characteristics of LEDs on Optical
OFDM," PhD Thesis, 2010.
In this paper, he gives differences between Radio and Visible Light
Communication and declares that Optical Wireless Communications has had a long
history. Wide spread deployment of solid state lighting (SSL) using LEDs is helping to
drive this technology in the form of Visible Light Communication (VLC). Data from an
experimental systems shows that data density’s of 0.41 bits/second/Hz/m2 is being
achieved from a VLC implementation.
B. Z. Ghassemlooy, Fellow IET, Senior member IEEE, W.O.Popoola, S.Rajbhandari,
M.Amiri,“Modulation Techniques for Wireless Infrared Communication” S. Hashemi
Optical Communications Research Group, NCRLab., Northumbria University, Newcastle
upon Tyne, UK .
In this paper, they have been proposed a number of modulation techniques and
thoroughly analyzed in literature for optical wireless communication systems. Each
modulation technique has its unique attractive features as well as its challenges. Some are
very simple to implement and bandwidth efficient like the On-Off keying (OOK). Pulse
interval modulation (PIM) techniques are reputed for their inherent synchronization pulse,
subcarrier modulation offers increased throughput, resilience to the inter-symbol
interference (ISI) and immunity against the fluorescent-light noise near DC, while pulse
position modulation (PPM) provides the unparalleled power efficiency in line of sight
(LOS) links but the performance degrades severely in dispersed communication channel.
There has been an enormous work on the analysis of these and many more
modulation techniques under different channel and environmental conditions, we
however present here a concise synopsis of the mostly reported wireless infrared
C. Akassh A. Mishra and Neelesh S. Salian,“Internet using Visible Light
Communication” IACSIT International Journal of Engineering and Technology, Vol. 3,
No. 5, October 2011
In this paper, they give the idea of using internet using Visible Light
Communication and also said that wireless communication is the need of the hour. In the
present fast paced life, there is a strong urgency for the improvement in the means of
communication. A Wireless network using Visible Light Communication (VLC) is a
newly emerging trend that can easily pave the way for a comfortable wire-free future.
Such a technology is useful to envision a smarter personal wireless network, underwater
communication and also in applications that provide mobile services. This paper aims to
explain the concept of VLC through its application to provide Wireless Internet. It
elaborates the use of Low Power Light Emitting Diodes (LEDs) for transmission and
reception along with the current and future prospects of this technology. It also deals with
the technical specifications for constructing such a network for real-time purposes. In this
experiment, we found that visible light was indeed an excellent medium to transmit data.
Since we used the low cost LED as our source, we barely had incurred much expenditure
to obtain the hardware components.
D. Jacqueline J.George1, Mohammed Hayder Mustafa, Nada Mahjoub Osman, Nuha
Hashim Ahmed, Da’ad Mohammed Hamed “A Survey on Visible Light
This paper introduces the concept of visible light communication (VLC). Visible-
light communications (VLC) is a technology for wireless communication using light that
can be perceived by the naked eye. VLC uses frequencies other than radio, and they are
unrestricted and licence free. The urgent need of VLC is to overcome the problems faced
in RF communication. Unlike existing methods of wireless communication, the visible
light portion of the electromagnetic frequency spectrum is used in VLC to transmit
information. Visible light communication (VLC) refers to the communication technology
which utilizes the visible light source as a signal transmitter, the air as a transmission
medium, and the appropriate photodiode as a signal receiving component. This paper
provides an overview of applications and design challenges for VLC, compare it with
other existing communication technologies and presents the modulation techniques used.
3. PRINCIPLE OF LI-FI
Heart of Li-Fi technology is high brightness LED’s. The Li-Fi technology
operates under the principle that light can be used to carry signals as an alternative to
traditional radio frequencies; it keeps serving as long as there is no obstruction of any
type, between the Light source and a device. Li-Fi technology is high intensity Light
emitting diodes. Light emitting diodes can be switched on and off faster since operating
speed of LED’s is less than 1 µs, than the human eye can detect, causing the light source
to be appear continuously. This invisible on off activity enables a kind of data
transmission using binary codes. Switching on and LED is a logical ‘1’, switching it off is
a logical ‘0’.It is possible to encode data in the light by varying the rate at which LED’s
flicker on and off to give different strings of 1s and 0s. Modulation is so fast that human
eye doesn’t notice. A light sensitive device (photo detector) receives the signal and
converts it back into original data. This method of using rapid pulses of light to transmit
information wirelessly is technically referred as Visible Light Communication (VLC)
though its potential to compete with conventional Wi-Fi has inspired the popular
characteristics Li Fi . Typical example of visible light communication is given in fig.1
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 .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'.
Fig. 3.1 Example of Visible light communication
4. CONSTRUCTION OF LI-FI SYSTEM
Li-Fi is a fast and cheap optical version of Wi-Fi. It 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 Li-Fi system are as follows:
a) A high brightness white LED which acts as transmission source.
b) A silicon photodiode with good response to visible light as the receiving element.
LEDs can be switched on and off to generate digital strings of different
combination of 1s and 0s. To generate a new data stream, data can be encoded in the light
by varying the flickering rate of the LED. The LEDs can be used as a sender or source, by
modulating the LED light with the data signal. The LED output appears constant to the
human eye by virtue of the fast flickering rate of the LED. Communication rate greater
than 100 Mbps is possible by using high speed LEDs with the help of various
multiplexing techniques. VLC data rate can be increased by parallel data transmission
using an array of LEDs where each LED transmits a different data stream. The Li-Fi
emitter system consists of 4 primary subassemblies:
b) RF power amplifier circuit (PA)
c) Printed circuit board (PCB)
The PCB controls the electrical inputs and outputs of the lamp and houses the
microcontroller used to manage different lamp functions. A 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 (shown in Fig. 2) are contained in an
aluminum enclosure. Fig. 2. Block diagram of Li-Fi sub-assemblies
The bulb sub-assembly is the heart of the Li-Fi emitter. It consists of a sealed bulb which
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. It acts as a waveguide for the RF energy transmitted by the PA. It also acts as
an electric field concentrator that focuses 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. Figure 3 shows the bulb sub-assembly. Fig.3. Bulb sub-
assembly There are various inherent advantages of this approach which includes high
brightness, excellent color quality and high luminous efficacy of the emitter – in the range
of 150 lumens per watt or greater. The structure is mechanically robust without typical
degradation and failure mechanisms associated with tungsten electrodes and glass to
metal seals, resulting in useful lamp life of 30,000+ hours. In addition, the unique
combination of high temperature plasma and digitally controlled solid state electronics
results in an economically produced family of lamps scalable in packages from 3,000 to
over 100,000 lumens.
5. DATA TRANSMISSION THROUGH LI-FI
As WI-FI hotspot and cloud computing are rapidly increasing reliable signal is
bound to suffer. Speed and security are also major concerns. They are vulnerable to
hackers as it penetrates through walls easily. LI-FI is said to overcome this. This new
technology is comparable to infrared remote controls which send data through an LED
light bulb that varies in intensity faster than the human eye can see. In near future we can
see data for laptops, smart phones and tablets transmitted through the light in a room.
Li-Fi (Light Fidelity) is a fast and cheap optical version of Wi-Fi, the technology
of which is based on Visible Light Communication (VLC).VLC is a data communication
medium, which uses visible light between 400 THz (780 nm) and 800 THz (375 nm) as
optical carrier for data transmission and illumination. It uses fast pulses of light to
transmit information wirelessly. The main component of this communication system is a
high brightness white LED, Which acts as a communication source and a silicon
photodiode which shows good response to visible wavelength region serving as the
receiving element. LED can be switched on and off to generate digital strings of 1s and
0s. Data can be encoded in the light to generate a new data stream by varying the
flickering rate of the LED. To be clearer, by modulating the LED light with the data
signal, the LED illumination can be used as a communication source. As the flickering
rate is so fast, the LED output appears constant to the human eye. A data rate of greater
than 100 Mbps is possible by using high speed LEDs with appropriate multiplexing
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. Fig. 4.1 Data transmission using LI-FI LI-FI
technology uses semiconductor device LED light bulb that rapidly develops binary
signals which can be manipulated to send data by tiny changes in amplitude. Using this
innovative technology 10000 to 20000 bits per second of data can be transmitted
simultaneously in parallel using a unique signal processing technology and special
Working of Li-fi is, as shown in fig. 3. The data gathered from internet or any other
source is encoded by lamp driver which is connected to LED lamp (or array of LED’s).
On one end all the data on the internet will be streamed to a lamp driver when the
led is turned on, the microchip controller converts the digital data in form of light
A light sensitive device (photo detector) receives the signal and converts it back
into original data. This method of using rapid pulses of light to transmit
information wirelessly is technically referred as Visible Light Communication
The data can be transferred by two ways either by varying light intensity according to
data pattern or by colors of illumination. Using the mixture of different color LED’s,
with each frequency encoding a different data channel; the system can operate on 10Gbps
speed. The light is modulated in such a way that the flickering light will not annoy the
users. This on off flickering is done as, on for logic ‘1’ and off for logic ‘0’. The
infrastructure needed to implement this technology is already established.
Nowadays, we have LED’s everywhere in the form of lamps. This research to develop
1µm2 LED has been started. Compare to today’s 1mm2 LED’s, the new LED’s are able
to flicker 1000 times faster and will transmits data millions times faster than normal
LED’s. Because of small size, large group of LED’s on a single source is possible.
6. COMMUNICATION WITH VLC
For any communication the two basic parts are sender and receiver. In VLC, a
LED bulb is used as sender. The sender signal is controlled either by fast ON/OFF
switching of LED or by color of light. This flickering is not good for eye safety, hence a
dimming scheme LED illumination or modulation is used control brightness. The photo
diode is used as a receiver to detect this signal. Following fig.2 shows open system
interconnection (OSI) model for VLC. Fig.2 OSI reference model for VLC
communication. The vital layers in VLC OSI model is Physical Layer (PHY)
and Data Like Layer (DLL). These are important for sending and receiving the light
signal. The Media Access Control (MAC) and PHY layers are same for both transmitter
and receiver part.
The Physical Layer: -
In VLC this layer functions same as in the OSI model. It defines the electrical and
physical specifications of hardware used. The communication on Physical layer is done
with small units of data called as packets. According to the data rates the physical layer is
PHY 1: It is low data rate (12 to 267 kbps) physical layer It is used for outdoor operation.
PHY 2: It have moderate data rate of 1.25 to 96 Mbps. It is used for indoor applications.
PHY 3: It is with high data rate of 12 to 96 Mbps. It is used for lightning sources and
The modulation formats used for PHY 1 and PHY 2 are On off Keying (OOK)
and (Variable PPM) VPPM. In case of OOK modulation logic 0 is denoted as 01 and
logic 1 by 10. This is to avoid illumination gap in case of continuous line of logic 0.
The Data Link Layer: -
This layer uses the services of physical layer to send and receive data bits over
communication channel. According to the architecture used in IEEE 802.15.7 project this
layer is divided into two sub-layers as an Optical Wireless Logic Link Control (OWLLC)
and Optical Wireless Media Access Control (OWMAC).
Optical Wireless LLC: It confirms and controls the logical links between devices on a
network. With DLL it allows the interconnection of other technologies and provides
services to network layer.
Optical Wireless MAC: The media of communication may be simplex, half duplex or full
duplex, OWMAC confirms the control over it. With the use of OWMAC protocol
working terminals and connected devices are controlled .
Fig. 6.1 OSI reference model for VLC communication
7. Issues with Radio Waves
Current system makes use of radio wave so day by day number of mobile
connection increase so the availability of the spectrum is getting congested.
Radio waves are limited.
Radio waves are scarce and expensive.
We only have a certain range of it.
With the advent of the new generation technologies like 2.5G, 3G, 4G and so on
we are running out of spectrum.
Million of work station consume huge amount of energy for transmitting radio
Almost 1.4 million cellular radio base stations.
Efficiency of each base station is just 5%.
Most of the energy is not used for transmission but rather used for cooling the
There is so many issues with the availability of radio waves.
Radio waves unavailable in air craft only available in base station.
It is also not suitable to use cell phone at the petrol pumps.
Radio waves can pass through the walls so they are less secure.
They can be intercepted.
If someone has knowledge and bad intentions then he may misuse it .
7.1 Alternative to Radio Waves in electromagnetic Spectrum
There are four major concerns i.e., capacity, efficiency, availability and security
related with Radio waves.
But on the other hand we have 40 billions of light box already installed and light
is the part of electromagnetic spectrum.
Gamma rays are simply very dangerous and thus can’t be used for our purpose of
X-rays are good in hospitals and can’t be used either.
Ultra-violet rays are good for getting a sun-tan but exposure for long duration is
Infrared rays are bad for our eyes and are therefore used at low power levels.
We have already seen the shortcomings of Radio waves.
So we are left with only Visible Light Spectrum.
Also if we see the spectrum band of visible light than we will find that it is 10000
times more than that of radio waves .
8. Overcoming the Issues of Radio Wave
Light is a voluntarily accessible form of energy and so it can cover most of the
portion of the EM spectrum.
Spectrum of visible light is 10000 times more than the spectrum of radio wave.
The data transmission through light can reach up to gigabits per second.
The data spread for a unit energy use is high in the case of light waves.
Here in Li-Fi data bits can be transmitted parallelly thus increasing the efficiency.
LED light consumes less energy.
Light is available in every part of the world so this makes it easy for every person
in airplanes to work on the internet.
There are an expected 14 billion light sources on earth and each can be easily
transformed into a LI FI hotspot.
LEDs are already present.
So we have the infrastructure available and already installed.
Not like radio waves light waves cannot go through solid (wall) objects thus
providing abundance of network privacy.
No other person can split a network unless the holder has allowed them to use it.
Data is present where there is light .
9. VLC Modulation Techniques
There are a number of different methods that can be used to modulate the data over the
visible light spectrum; the main methods are :
9.1 On-off keying (OOK): As the name suggests the data is conveyed by turning the
LED off and on. In its simplest form a digital ‘1’ is represented by the light ‘on’ state and
a digital ‘0’ is represented by the light ‘off’ state. The beauty of this method is that it is
really simple to generate and decode. However, this method is not optimal in terms of
illumination control and data throughput
9.2 Pulse width modulation (PWM): This method conveys information encoded into the
duration of pulses. More than one bit of data can be conveyed within each pulse, but they
may have to be longer pulses than for OOK, so there is no great advantage with this
scheme. It is also possible to transmit data in an analogue format using this scheme which
is also relatively simple to implement
9.3 Pulse position modulation (PPM): For PPM the data is encoded using the position
of the pulse within a frame. Again more than one bit can be transmitted in each pulse,
however the duration of the frame must be longer than for a single OOK bit,
so again it is not necessarily more efficient. It does have the advantage of containing the
same amount of optical energy within each frame
9.4 Variable Pulse Position Modulation (VPPM): This is similar to PPM but allows the
pulse width to be controlled for light dimming support. Pulse amplitude modulation
(PAM), As the name suggests, the information is carried by the amplitude of the pulse. A
number of data bits could be conveyed in a single pulse. e.g. off =00, 1/3 amplitude =01,
2/3 amplitude =10, full amplitude =11. In this example four different amplitude levels are
used to carry two bits of information. PAM can carry more data in each pulse than OOK,
but it is more complex and more susceptible to noise on the optical channel.
9.5 Colour shift keying (CSK): This can be used if the illumination system uses RGB
type LEDs. By combining the different colours of light, the output data can be carried by
the colour itself and so the intensity of the output can be constant. The disadvantage of
this system is the complexity of both the transmitter and receiver.
9.6 Orthogonal Frequency Division Multiplex (OFDM): This modulation scheme has
been widely used for digital TV and radio and also for WiFi. It can be modified for use in
optical communications. OFDM uses a set of sub-carriers each at different but
harmonically related frequencies. There are a number of advantages including good
spectral efficiency but this method is quite complex to implement.
9.7 Spatial Modulation (SM): There are a number of techniques that allow one to
determine the source of an optical signal. If one can determine its source one can either
use the multiple sources of information to convey multiple stream of independent data
(one from each source), or one can use the source of the signal as part of the information
encoding itself. The multiple sources could be multiple LEDs within a single fixture.
10. 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
The table also contains the current wireless technologies that can be used for
transferring data between devices today, i.e. Wi-Fi and Li-Fi. 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.
Li-Fi can only work when your device can detect the light being emitted by the
Li-Fi router, meaning it will only work if you’re in the same room or area the light is
being emitted. This means people passing by cannot connect and piggyback off of your
Internet connection. And did we mention that it’s unaffected by RF-emitting equipment
operating in the same room, such as a microwave or radio.
Li-Fi is also way faster; the latest Wi-Fi standard, 801.11ac, has a maximum
possible speed of about 867 Megabits per second for a typical handheld. Li-Fi,
meanwhile, can reach speeds up to 3.5Gbit/s per color – meaning a typical Red-Green-
Blue (RGB) LED can emit speeds up to 10.5Gbit/s – more than 10 times faster than the
latest Wi-Fi technology. These speeds offer a lot of potential for wireless
What you also may not know is that light already is the most popular means to
transmit data across long distances. Fiber optic cables send data as light through tiny
strands of silicon. Fiber optics are the arteries of much of the modern internet, allowing
fast transmissions of data around the world. Li-Fi uses light just as fiber optics do to
transmit the information, but instead of maintaining it through the thin strand of fiber, it
allows the light to spread out in all directions so devices all over the room can connect.
S.NO. PARAMETERS WIRELESS TECHNOLOGIES
LIGHT FIEDILITY WIRELESS FIEDILITY
1 Speed for data transfer Faster transfer speed(>1Gbps) Data transfer speed(150
2 Medium through which
data transfers occurs
Use light as a carrier Used radio spectrum
3 Spectrum range Visible light spectrum has
10,000 time large spectrum in
comparison to radio frequency.
RF spectrum range is less
than visible light spectrum.
4 Cost Cheaper than Wi-Fi because free
band doesn’t need license and it
Costly in comparison to Li-
fi because it uses radio
5 Power consumption It consumes less power It consumes high power
6 Standard IEEE 802.15 IEEE 802.11
7 Security It is highly secure It is less secure than Lifi
8 Operating frequency Hundreds of Tera Hz 2.4 GHz to 5 GHz
Table 1: Comparison between Li-Fi and Wi-Fi
11. ADVANTAGES OF LI-FI
1. Li-Fi can solve problems related to the insufficiency of radio frequency bandwidth
because this technology uses Visible light spectrum that has still not been greatly
2. High data transmission rates of up to 10Gbps can be achieved.
3. Li- Fi can use light rather than radio frequency signals,
4. Integrated into medical devices and in hospitals as this technology does not deal
with radio waves, so it can easily be used in such places where Bluetooth,
infrared, Wi-Fi and internet are banned. In this way, it will be most helpful
transferring medium for us.
5. There are around 19 billion bulbs worldwide, they just required to be replace with
LED ones that transmit data.VLC is at a factor of ten, cheaper than WI-FI.
6. Security is another benefit, since light does not penetrate through walls.It provides
privacy and security that Wi-Fi cannot.
7. In streets for traffic control. Cars having LED based headlights, LED based
backlights, and Car can communicate each other and prevent accidents in the way
that they exchange Information. Traffic light can communicate to the car and so
8. It is safe for humans since light, unlike radio frequencies, cannot penetrate human
body. Hence, concerns of cell mutation are mitigated.
9. By implementing the Technology worldwide every street lamp would be a free
10. Li-Fi has low implementation and maintenance costs.
11. Li-Fi may solve issues such as the shortage of radio frequency bandwidth.
12. LIMITATIONS OF LI-FI
1. 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.
2. Reliability and network coverage are the major issues to be considered by the
companies while providing VLC services. Interference from external light sources
like sun light, normal bulbs; and opaque materials in the path of transmission will
cause interruption in the communication.
3. High installation cost of the VLC systems can be complemented by large-scale
implementation of VLC though
4. Adopting VLC technology will reduce further operating costs like electricity
charges, maintenance charges etc.
5. This research report categorizes the global VLC technology market; based on
component, applications, and geography. Li-Fi uses light-emitting diodes (LEDs)
which are rapidly gaining in popularity for standard light bulbs and other domestic
and commercial purposes. They are expected to be ubiquitous in 20 years. VLC is
not in competition with Wi-Fi, Prof. Haas says, it is a complimentary technology
that should eventually help free up much needed space within the radio wave
6. We still need Wi-Fi we still need radio frequency cellular systems. You can’t have
a light bulb that provides data to a high-speed moving object or to provide data in
a remote area where there are trees and walls.
13. APPLICATIONS OF LI-FI
There are numerous applications of this technology, from public internet access
through street lamps to auto-piloted cars that communicate through their headlights.
Applications of Li-Fi can extend in areas where the Wi-Fi technology lacks its presence
like medical technology, power plants and various other areas. Since Li-Fi uses just the
light, it can be used safely in aircrafts and hospitals where Wi-Fi is banned because they
are prone to interfere with the radio waves. All the street lamps can be transferred to Li-Fi
lamps to transfer data. As a result of it, it will be possible to access internet at any public
place and street.
Some of the future applications of Li-Fi are as follows:
a) Education systems: Li-Fi is the latest technology that can provide fastest speed
internet access. So, it can replace Wi-Fi at educational institutions and at companies so
that all the people can make use of Li-Fi with the same speed intended in a particular
b) Medical Applications: Operation theatres (OTs) do not allow Wi-Fi due to radiation
concerns. Usage of Wi-Fi at hospitals interferes with the mobile and pc which blocks the
signals for monitoring equipments. So, it may be hazardous to the patient's health. To
overcome this and to make OT tech savvy Li-Fi can be used to accessing internet and to
control medical equipments. This can even be beneficial for robotic surgeries and other
c) Cheaper Internet in Aircrafts: The passengers travelling in aircrafts get access to low
speed internet at a very high rate. Also Wi-Fi is not used because it may interfere with the
navigational systems of the pilots. In aircrafts Li-Fi can be used for data transmission. Li-
Fi can easily provide high speed internet via every light source such as overhead reading
bulb, etc. present inside the airplane.
d) Underwater applications: Underwater ROVs (Remotely Operated Vehicles) operate
from large cables that supply their power and allow them to receive signals from their
pilots above. But the tether used in ROVs is not long enough to allow them to
explore larger areas. If their wires were 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 sending their findings periodically back to the surface. Li-Fi can even work
underwater where Wi-Fi fails completely, thereby throwing open endless opportunities
for military operations.
e) Disaster management: Li-Fi can be used as a powerful means of communication in
times of disaster such as earthquake or hurricanes. The average people may not know the
protocols during such disasters. Subway stations and tunnels, common dead zones for
most emergency communications, pose no obstruction for Li-Fi. Also, for normal periods,
Li-Fi bulbs could provide cheap high-speed Web access to every
f) Applications in sensitive areas: Power plants need fast, inter-connected data systems
so that demand, grid integrity and core temperature (in case of nuclear power plants) can
be monitored. Wi-Fi and many other radiation types are bad for sensitive areas
surrounding the power plants. Li-Fi could offer safe, abundant connectivity for all areas
of these sensitive locations. This can save money as compared to the currently
implemented solutions. Also, the pressure on a power plant‘s own reserves could be
lessened. Li-Fi can also be used in petroleum or chemical plants where other transmission
or frequencies could be hazardous.
g) Traffic management: In traffic signals Li-Fi can be used which will communicate
with the LED lights of the cars which can help in managing the traffic in a better manner
and the accident numbers can be decreased. Also, LED car lights can alert drivers when
other vehicles are too close.
h) GPS usage Satellite navigation has been one of the most important technological
advances of the last 50 years. No matter how good the systems get, they still don’t work
where we spend the majority of our time: the great indoors. Tools have been devised that
cleverly use Wi-Fi triangulation and “hybrid” GPS (say, GPS coordinates combined with
sensor data from a compass, pedometer, and accelerometer), but these are 1692 Dinesh
Khandal, Sakshi Jain inaccurate and generally unreliable. A company called Byte Light is
trying to change this situation with a system that uses LED lighting to provide devices
with accurate location data. Byte Light’s indoor location system works by controlling the
pulses of LEDs so they work in a certain pattern. This pattern is not detectable to the
human eye (it’s working in the range of a hundreds of hertz), but can be picked up by the
camera in a smartphone or tablet. Using the data gleaned from the LED modulation, the
device works with an app and performs client-side calculations to figure out where it is
within the structure. Wi-Fi isn’t needed so networking is not a problem, and the
calculations are performed on the device, so everything happens quickly.
i) Replacement for other technologies: Li-Fi doesn‘t work using radio waves. So, it can
be easily used in the places where Bluetooth, infrared, Wi-Fi, etc. are banned. In this way,
it will be most helpful transferring medium for us.It includes other benefits like:
A very wide spectrum over visible wave length range.
Extremely high colour fidelity.
Instant start time.
Easy terminal Management.
Dynamic dark i.e. brightness Modulation of lamp output to enhance video
Trouble-free integration into existing light engine platform.
14. FUTURE SCOPE
Li-Fi provides a great platform to explore the grounds of transmission of wireless
data at high rates. If this technology is put into practical use, each light bulb installed, is
potential and can be used as a Wi-Fi hotspot to transmit data in a cleaner, greener and
safer manner. The applications of Li-Fi are beyond imagination at the moment. With this
enhanced technology, people can access wireless data with the LED’s installed on the go
at very high rates. It resolves the problem of shortage of radio frequency bandwidth. In
various military applications, where RF based communications are not allowed, Li-Fi
could be a viable alternative to securely pass data at high rates to other military vehicles
. Also LEDs can be used effectively to carry out VLC in many hospital applications
where RF based communications could be potentially dangerous. Since light cannot
penetrate through walls, it could be a limitation to this technology. Nevertheless, given its
high rates of data transmission and applications in multiple fields, Li-Fi is definitely the
future technology in wireless communication.
Li-Fi has great potential in the field of wireless data transmission. It is a promising
alternative to conventional methods of wireless communications that use radio waves as
data carrier. Many enhancements can be made to the existing technology. For example,
encoding and decoding can be implemented directly in the transmitter and receiver part of
the circuit. This would reduce error in transmission. Also, by using fast-switching LEDs,
data transmission rates can be further enhanced. The driving speed of the circuit can be
improved by using fast-switching transistors. If this technology is put into full-fledged
practical use, every LED can be used like a Wi-Fi hotspot to transmit wireless data. This
can lead us to a safer and greener future.
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I Vol-03, Issue-02, February 2015