A

Seminar Report On

“DATA TRANSMISSION THROUGH

ILLUMINATION”Submitted In Partial Fulfillment of the Requirement

For The Award of Degree of Bachelor of Engineering

In Computer Science & Engineering

North Maharashtra University, Jalgaon

Submitted By

Mr. Pravin Ahirwar

Computer Science & Engineering

Shri Sant Gadge Baba

College of Engineering and Technology, Bhusawal

North Maharashtra University, Jalgaon

2014-15

Shri Sant Gadge Baba

College of Engineering and Technology,

Bhusawal 425203

Certificate

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

ACKNOWLEDGEMENT

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

that arose.

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

them.

PRAVIN AHIRWAR

T.E CSE

ABSTRACT

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.

INDEX

Title Page No.

Abbreviations i

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

7.1Alternative to radio waves in electromagnetic

spectrum15

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

References

ABBREVIATIONS

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

1. INTRODUCTION

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[1]. 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 [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 [3].

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

2.1HISTORY

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

systems.

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 [3].

2.2 REVIEW OF PAPERS

A. H. Elgala , "A Study on the Impact of Nonlinear Characteristics of LEDs on Optical

OFDM," PhD Thesis, 2010[4].

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[5] .

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

modulation techniques.

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[6]

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

Communication”[7]

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 [2]. Typical example of visible light communication is given in fig.1

below.

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:

a) Bulb

b) RF power amplifier circuit (PA)

c) Printed circuit board (PCB)

d) Enclosure

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

Fig.4.1 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[8].

Fig 4.2 shows the bulb sub-assembly

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[9]. 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

techniques[2].

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

modulation.

5.1 WORKING

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

through LEDs.

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.

Fig 5.1: Working Of Li-Fi

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

categorized as,

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

detectors.

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 [10].

Fig. 6.1 OSI reference model for VLC communication

7. Issues with Radio Waves

Capacity:

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.

Efficiency:

Million of work station consume huge amount of energy for transmitting radio

waves.

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

base station.

Availability:

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.

Security:

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 [11].

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

communication.

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

Ultra-violet rays are good for getting a sun-tan but exposure for long duration is

dangerous.

Infrared rays are bad for our eyes and are therefore used at low power levels.

We have already seen the shortcomings of Radio waves.

So we are left with only Visible Light Spectrum.

Also if we see the spectrum band of visible light than we will find that it is 10000

times more than that of radio waves [11].

Fig 7.1: Electromagnetic Spectrum

8. Overcoming the Issues of Radio Wave

Capacity:

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.

Efficiency:

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.

Highly efficient.

Availability:

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.

Security:

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 [11].

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[13] :

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

complimentary[1].

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

connectivity[14].

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 FIEDILITY1 Speed for data transfer Faster transfer speed(>1Gbps) Data transfer speed(150

Mbps)2 Medium through which

data transfers occursUse 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 use light.

Costly in comparison to Li-fi because it uses radio spectrum.

5 Power consumption It consumes less power It consumes high power6 Standard IEEE 802.15 IEEE 802.117 Security It is highly secure It is less secure than Lifi8 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

utilized.

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

on.

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

access point.

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

spectrum.

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[14].

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

area.

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

automated procedures.

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

street corner.

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[15].

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[16].

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

contrast.

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

[16]. 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.

15. CONCLUSION

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.

REFERENCES

[1] Megha Goyal, Dimple Saproo, and Asha Bhagashra “New Epoch of wireless

communication: Light Fidelity”. IJIRCCE, vol 1, issue 2, April 2013.

[2] M. Mutthamma,” A survey on Transmission of data through illumination - Li-Fi”

International Journal of Research in Computer and

Communication Technology, Vol 2, Issue 12, December- 2013

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

[4] H. Elgala, "A Study on the Impact of Nonlinear Characteristics of LEDs on Optical

OFDM," PhD Thesis, 2010

[5] 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 .

[6] 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

[7] Jacqueline J.George1, Mohammed Hayder Mustafa, Nada Mahjoub Osman, Nuha

Hashim Ahmed, Da’ad Mohammed Hamed “A Survey on Visible Light

Communication”.

[8] Rahul R. Sharma, Raunak, Akshay Sanganal, “Li-Fi Technology Transmission of data

through light” Int.J.Computer Technology & Applications,Vol 5 (1),150-154

[9] Jyoti Rani, Prerna Chauhan, Ritika Tripathi,”Li-Fi (Light Fidelity)-The future

technology In Wireless communication”. International Journal of Applied

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

[10] C. S. Patil , R. B. Bhamare, M. I. Rangrez “A study of visible light communication

with LiFi Technology”,International Journal Of Advanced Electronics &

Communication Systems Approved by CSIR-NISCAIR ISSN NO: 2277-7318

[11] Kanchan, Gupta Kajal, Ashish Saini , “Lifi- Light Fidelity Technology- A Review”

International Journal of Research (IJR) Vol-1, Issue-10 November 2014 ISSN 2348-

6848

[12] Jacqueline J.George, Mohammed Hayder Mustafa, Nada Mahjoub Osman, Nuha

Hashim Ahmed, Da’ad Mohammed Hamed, “ A Survey on Visible Light

Communication”, International Journal Of Engineering And Computer Science

ISSN:2319-7242 Volume 3 Issue 2, February 2014 Page No. 3805-3808

[13] Light bulbs could replace your Wi-Fi router By Joshua Sherman,

http://www.digitaltrends.com/mobile/light-bulb-li-fi-wirelessinternet/#ixzz3UfUjPPye

[14] Dhakane Vikas Nivrutti, Ravi Ramchandra Nimbalkar “Light-Fidelity: A

Reconnaissance of Future Technology”,International Journal of Advanced Research

in Computer Science and Software Engineering, Volume 3, Issue 11, November 2013

[15] Dinesh Khandal, Sakshi Jain “Li-Fi (Light Fidelity): The Future Technology in

Wireless Communication”, International Journal of Information & Computation

Technology. ISSN 0974-2239 Volume 4, Number 16 (2014)

[16] Golthi Tharunn, G Dixith Reddy, Virisha Timmaraju “Li-Fi: The Future of Wireless

Technology”, International Journal of Advanced Engineering and Global Technology

I Vol-03, Issue-02, February 2015