Li fi report

Li-Fi
2013
Li-Fi:
The latest tech in Wireless Communication
A Seminar Project Report submitted by: Vivek Kumar Jha
in partial fulfillment for the award of the degree of
Bachelor in Technology in Computer Science & Engg.
under the able guidance of Ms. Sarita Das (Project
Guide) & Ms. Nalini Prabha Behera (HOD, CSE).

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Acknowledgement
I take this opportunity to express my deep sense of gratitude
and thankfulness to my project guide, Ms. Sarita Das
andMs. Nalini Prabha Behera(HOD, CSE) under whose
able guidance I have been successful in finishing the project
work.
Vivek Kumar Jha
Regd. No – 1001215240
Branch – CSE
EAST

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Certificate
This is to certify that Master Vivek Kumar Jha, 6th Sem, CSE Branch
has completed & duly submitted his seminar report hard copy
correctly within the stipulated time. His work was found to be
genuine & correct.
Ms. N.P. Behera Ms. Sarita Das Ms. S. Mishra
(H.O.D, CSE) (Project Guide) (Principal, EAST)

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Contents
Acknowledgement_____________________________1
Certificate____________________________________2
Abstract_____________________________________3
Introduction__________________________________4
System Design________________________________6
Present Scenario______________________________15
Issues with Radio Waves_______________________16
Li-Fi as an alternative__________________________17
Light for wireless Communication________________19
Implementation_______________________________19
Achieving Communication through light___________25
Overcoming the issues_________________________26
Application__________________________________27
Conclusion__________________________________28
Reference___________________________________29

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Abstract
hether you’re using wireless internet in a coffee
shop,stealing it from the guy next door, or competing for
bandwidth at a conference, you have probably gotten
frustrated at the slow speeds you face when more than one device is
tapped into the network. As more and more people and their
manydevices access wireless internet, clogged airwaves are going
tomake it.
One German physicist, Harald Haas has come up with asolution he
calls “data through illumination” –taking the fibberout of fiber optic by
sending data through an LED light bulbthat varies in intensity faster
than the human eye can follow.It’s the same idea band behind infrared
remote controls but farmore powerful.
Haas says his invention, which he calls D-Light,can produce data rates
faster than 10 megabits persecond, which is speedier than your average
broadbandconnection. He envisions a future where data for
laptops,smart phones, and tablets is transmitted through the light in
aroom. And security would be snap – if you can’t see the light,you can’t
access the data.
W

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Introduction to Li-Fi
i-Fi is transmission of data through illumination by taking
thefiber out of fiber optics by sending data through a LED
lightbulb that varies in intensity faster than the human eye
canfollow.
“At the heart of this technology is a newgeneration of high brightness
light-emitting diodes”, saysHarald Haas from the University of
L

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Edinburgh, UK.”Verysimply, if the LED is on, you transmit a digital 1,
if it’s offyou transmit a 0,”Haas says, “They can be switched on and
offvery quickly, which gives nice opportunities for transmitteddata.”
It is possible to encode data in the light by varying therate at which the
LEDs flicker on and off to give differentstrings of 1s and 0s.The LED
intensity is modulated so rapidlythat human eye cannot notice, so the
output appears constant.
More sophisticated techniques could dramatically increaseVLC data
rate. Terms at the University of Oxford and theUniversity of Edinburgh
are focusing on parallel datatransmission 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 adifferent data channel.
Li-Fi, as it has been dubbed, has alreadyachieved blisteringly high
speed in the lab. Researchers at theHeinrich Hertz Institute in Berlin,
Germany have reached datarates of over 500 megabytes per second
using a standardwhite-light LED.

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System Design
Li-Fi is typically implemented using white LED light bulbs at the
downlink transmitter. These devices are normally used for illumination
only by applying a constant current. However, by fast and subtle
variations of the current, the optical output can be made to vary at
extremely high speeds. This very property of optical current is used in
Li-Fi setup.The operational procedure is very simple-,data from the
internet and local network is used to modulate the intensity of the LED
light source if any undetectable to the human eye. The photo detector
picks up signal, which is converted back into a data stream and sent to
the client.
The client can communicate through its own LED output or over the
existing network. An overhead lamp fitted with an LED with signal-
processing technology streams data embedded in its beam at ultra-high
speeds to the photo-detector. A receiver dongle then converts the tiny
changes in amplitude into an electrical signal, which is then converted
back into a data stream and transmitted to a computer or mobile
device.

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Methods of Visible Light Communication
Devices used for Visible Light Communication
Communication using Image Sensors
Devices used for Visible Light Communication
Transmitter Device Receiver Device
Methods of Visible Light Communication
Transmitter device of visible light communication
Visible Light LED
LED light intensity is modulated by controlling its current.
Data rate: low speed to very high speed (up to several hundred
Mbps)
Visible Light

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Visible Light LED
Fluorescent Lamp
FSK modulation of high frequency fluorescent light.
Data rate: up to several kilo bps.
Fluorescent Lamp
Receiver device of visible light communication
PIN photo diode:
A PIN diode is a diode with a wide, lightly doped 'near' intrinsic
semiconductor region between a p-type semiconductor and an n-type
semiconductor region. The p-type and n-type regions are typically
heavily doped because they are used for Ohmic contacts.
The wide intrinsic region is in contrast to an ordinary PN diode. The
wide intrinsic region makes the PIN diode an inferior rectifier (one
typical function of a diode), but it makes the PIN diode suitable for

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attenuators, fast switches, photo detectors, and high voltage power
electronics applications.
Operation:
A PIN diode operates under what is known as high-level injection.
In other words, the intrinsic "i" region is flooded with charge carriers
from the "p" and "n" regions. Its function can be likened to filling up a
water bucket with a hole on the side. Once the water reaches the hole's
level it will begin to pour out. Similarly, the diode will conduct current
once the flooded electrons and holes reach an equilibrium point, where
the number of electrons is equal to the number of holes in the intrinsic
region. When the diode is forward biased, the injected carrier
concentration is typically several orders of magnitude higher than the
intrinsic level carrier concentration. Due to this high level injection,
which in turn is due to the depletion process, the electric field extends
deeply (almost the entire length) into the region. This electric field
helps in speeding up of the transport of charge carriers from P to N
region, which results in faster operation of the diode, making it
a suitable device for high frequency operations.

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PIN photodiode
Avalanche photo diode
An avalanche photodiode (APD) is a highly sensitive
semiconductor electronic device that exploits the photoelectric effect to
convert light to electricity. APDs can be thought of as photo
detectors that provide a built-in first stage of gain through avalanche
multiplication. From a functional standpoint, they can be regarded as
the semiconductor analog to photo multipliers.By applying a high
reverse bias voltage (typically 100-200 V in silicon), APDs show an
internal current gain effect (around 100) due to impact
ionization (avalanche effect). However, some silicon APDs employ
alternative doping and beveling techniques compared to traditional
APDs that allow greater voltage to be applied (> 1500 V) before
breakdown is reached and hence a greater operating gain (> 1000).In
general, the higher the reverse voltage the higher the gain.

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Figure-2.6: Avalanche photo diode
APD applicability and usefulness depends on many parameters.
Two of the larger factors are: quantum efficiency, which indicates how
well incident optical photons are absorbed and then used to generate
primary charge carriers; and total leakage current, which is the sum of
the dark current and photocurrent and noise. Electronic dark noise
components are series and parallel noise. Series noise, which is the
effect of shot noise, is basically proportional to the APD capacitance
while the parallel noise is associated with the fluctuations of the APD
bulk and surface dark currents. Another noise source is the excess
noise factor, F. It describes the statistical noise that is inherent with the
stochastic APD multiplication process.
Image sensor
An image sensor is a device that converts an optical image into
an electronic signal. It is used mostly in digital cameras, camera
modules and other imaging devices. Early analog sensors were video
camera tubes; most currently used are digital charge-coupled

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device (CCD) or complementary metal–oxide–semiconductor
(CMOS) active pixel sensors.
Image sensor
Communication using Image Sensors
Principles of communication using image sensor

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Principles of Communication Using Image
Sensor
Camera (receiver) continuously takes images of a scene with an LED
light and a receiver detects the optical intensity at a pixel where the
LED light is focused on.
Even if multiple visible light sources send data simultaneously, an
image sensor is able to receive and demodulate all the data
simultaneously without any interference between them.
Merits of communication using image sensor
Number of signal: Multiple.
Robustness: no cross talk/no Interference.
Distance: Very Long (2km).
Space Resolution: Each pixel.

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Areas to which visible light communication technology may be
applied
Applications that do personal area communication.
Applications that enable users to know users locations in
several meter accuracy.
Applications that enable users to know users locations in
several millimeter accuracy.
Applications that use augmented reality.
Applications that cannot be achieved by radio-wave technology.
Present Scenario
We have 1.4million cellular mast radio waves base stations
deployed.
We also have over 5 billions of mobile phones.
Mobile phone transmits more than 600 Tb of data.
Wireless communication has become a utility like electricity &
water.
We use it in our everyday life, in our private life, business life.
Currently Wi-Fi uses Radio Waves for communication.
It is important to look into this technology which has become
fundamental to our life.

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Four Issues with Radio Waves
1.Capacity:
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.
2. Efficiency:
There are 1.4 million cellular radio base stations.
They consume massive amount of energy.
Most of this energy is not used for transmission but for
cooling down the base stations.
Efficiency of such a base station is only 5%.
3. Availability:
Availability of radio waves is another cause of concern.
We have to switch off our mobiles in aero planes.
It is not advisable to use mobiles at places like petrochemical
plants and petrol pumps.
4. Security:
Radio waves penetrate through walls.
They can be intercepted.

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If someone has knowledge and bad intentions then he may
misuse it.
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.

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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.

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Light for Wireless Communication
Light has been around for millions of years.
It has created us created life and has created all stuffs of life.
Visible light Communication (VLC) uses rapid pulses of light to
transmit information wirelessly. Now it may be ready to compete
with conventional Wi-Fi.
So it is inherently safe to use for wireless communication.
IMPLEMENTATION
This brilliant idea was first showcased by Harald Haas from University
of Edinburgh, UK, in his TED Global talk on VLC. He explained,” Very
simple, if the LED is on, you transmit a digital 1, if it’s off you transmit
a 0. The LEDs can be switched on and off very quickly, which gives nice
opportunities for transmitting data.” So what you require at all are
some LEDs and a controller that code data into those LEDs. We have to
just vary the rate at which the LED’s flicker depending upon the data
we want to encode. Further enhancements can be made in this method,
like using an array of LEDs for parallel data transmission, or using
mixtures of red, green and blue LEDs to alter the light’s frequency with
each frequency encoding a different data channel.
Such advancements promise a theoretical speed of 10Gbps–
meaning you can download a full high-definition film in just 30

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seconds. Simply awesome! But blazingly fast data rates and depleting
bandwidths worldwide are not the only reasons that give this
technology an upper hand. Since Li-Fi uses just the light, it can be used
safely in aircrafts and hospitals that are prone to interference from
radio waves. This can even work underwater where Wi-Fi fails
completely, thereby throwing open endless opportunities for military
operations.
Imagine only needing to hover under a street lamp to get public
internet access, or downloading a movie from the lamp on your desk.
There's a new technology on the block which could, quite literally as
well as metaphorically, 'throw light on' how to meet the ever-increasing
demand for high-speed wireless connectivity. Radio waves are replaced
by light waves in a new method of data transmission which is being
called Li-Fi. Light-emitting diodes can be switched on and off faster
than the human eye can detect, causing the light source to appear to be
on continuously. A flickering light can be incredibly annoying, but has
turned out to have its upside, being precisely what makes it possible to
use light for wireless data transmission. Light-emitting diodes
(commonly referred to as LEDs and found in traffic and street lights,
car brake lights, remote control units and countless other applications)
can be switched on and off faster than the human eye can detect,
causing the light source to appear to be on continuously, even though it
is in fact 'flickering'. This invisible on-off activity enables a kind of data
transmission using binary codes: switching on an LED is a logical '1',

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switching it off is a logical '0'. Information can therefore be encoded in
the light by varying the rate at which the LEDs flicker on and off to give
different strings of 1s and 0s. This method of using rapid pulses of light
to transmit information wirelessly is technically referred to as Visible
Light Communication (VLC), though it’s potential to compete with
conventional Wi-Fi has inspired the popular characterization Li-Fi.
Visible light communication “A potentialsolution
to the global wireless spectrum shortage”
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 components of this communication system are
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.

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Data can be encoded in the light to generate a new data stream by
varying the flickering rate of the LED. To be clearer, by modulating the
LED light with the data signal, the LED illumination can be used as a
communication source. As the flickering rate is so fast, the LED output
appears constant to the human eye. A data rate of greater than 100
Mbps is possible by using high speed LEDs with appropriate
multiplexing techniques. VLC data rate can be increased by parallel
data transmission using LED arrays where each LED transmits a
different data stream. There are reasons to prefer LED as the light
source in VLC while a lot of other illumination devices like fluorescent
lamp, incandescent bulb etc. are available.
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.

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Technology Speed Data density
Wireless (current)
Wi-Fi – IEEE 802.11n 150 Mbps *
Bluetooth 3 Mbps **
IrDA 4 Mbps ***
Wireless (future)
WiGig 2 Gbps **
Giga-IR 1 Gbps ***
Li-Fi >1Gbps >1Gbps ****
Comparison between current and future wireless technology
The table also contains the current wireless technologies that can be
used for transferring data between devices today, i.e. Wi-Fi, Bluetooth
and IrDA. Only Wi-Fi currently offers very high data rates. The IEEE
802.11.n in most implementations provides up to 150Mbit/s (in theory
the standard can go to 600Mbit/s) although in practice you receive
considerably less than this. Note that one out of three of these is an
optical technology.
How it is different?
Li-Fi technology is based on LEDs for the transfer of data. The
transfer of the data can be with the help of all kinds of light, no matter
the part of the spectrum that they belong. That is, the light can belong
to the invisible, ultraviolet or the visible part of the spectrum. Also, the
speed of the internet isincredibly high and you can download movies,
games, music etc in just a few minutes with the help of this technology.

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Also, the technology removes limitations that have been put on the
user by the Wi-Fi. You no more need to be in a region that is Wi-Fi
enabled to have access to the internet. You can simply stand under any
form of light and surf the internet as the connection is made in case of
any light presence. There cannot be anything better than this
technology.
What we have to do?
We have to replace inefficient fluorescents with this new dignitary
of LED lights.
The LED will hold a micro-chip that will do the job of processing
the data.
Light intensity can be modulated at very high speeds to send data
by tiny changes in amplitude.

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Achieving Communication through Light
Let’s start with the foremost communication device which everyone has
in their homes i.e., a Remote Control. A remote control has an
Infrared-LED. It creates a single data stream and the data rate
achieved is around 10000b/s to 20000b/s. Now if we replace the
remote control with a light box, we are able to transmit 1000’s of data
stream in parallel at high speeds. This technology is termed as Spatial
Modulation.
Remote Control Data via LED
Is it a Proven Technology?
Yes, this is already proven.
Harald Haas demonstrated his invention using an ordinary table lamp
that successfully transmitted data at speeds exceeding 10Mbps using
light waves from LED light bulbs to a computer located below the
lamp.
To prove that the light bulb was the source of the data stream, he
periodically blocked the beam of light, causing the connection to drop.

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Overcoming the four issues with RW in Li-Fi
1.Capacity:
10000 times more spectrum than RW.
LEDs are already present.
So we have the infrastructure available and already
installed.
2.Efficiency:
Data through illumination and thus data transmission
comes for free.
LED light consumes less energy
Highly efficient
3.Availability
Light is present everywhere.
4.Security:
Light waves don’t penetrate through walls.
Data is present where there is light.

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Applications of Li-Fi
At present its applications are beyond imagination but still if to think
about few then they are:
Can be used in places where it is difficult to lay the optical fiber
like hospitals. In operation theatre Li-Fi can be used for modern
medical instruments.
In traffic signals Li-Fi can be used which will communicate with
LED lights of the cars and accident numbers can be decreased.
Thousand and millions of street lamps can be transferred to Li-Fi
Lamps to transfer data.
In aircraft Li-Fi can be used for data transmission.
It can be used in petroleum or chemical plants where other
transmission or frequencies could be hazardous.

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Conclusion
he possibilities are numerous and can be explored further. If this
technology can be put into practical use, every bulb can beused
something like a Wi-Fi hotspot to transmit wireless dataand we will
proceed toward the cleaner, greener, safer andbrighter future. The
concept of Li-Fi is currently attracting agreat deal of interest, not least
because it may offer a genuineand very efficient alternative to radio-
based wireless. As agrowing number of people and their many devices
accesswireless internet, the airwaves are becoming
increasinglyclogged, making it more and more difficult to get a
reliable,high-speed signal. This may solve issues such as the shortageof
radio-frequency bandwidth and also allow internet wheretraditional
radio based wireless isn’t allowed such as aircraftor hospitals. One of
the shortcomings however is that it onlywork in direct line of sight.
T

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References
http://en.wikipedia.org/wiki/Li-Fi
http://teleinfobd.blogspot.in/2012/01/what-is-lifi.html
www.lificonsortium.org/
Will Li-Fi be the new Wi-Fi?, New Scientist, byJamieCondliffe,
dated 28 July 2011
http://www.digplanet.com/wiki/Li-Fi
“Visible-light communication: Tripping the lightfantastic: A fast
and cheap optical version of Wi-Fi iscoming”, Economist, dated
28Jan 201

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