1. ABSTRACT
Whether you’re using wireless internet in a coffee shop, stealing it from the guy next
door, or competing for bandwidth at a conference, you’ve probably gotten frustrated at
the slow speeds you face when more than one device is tapped into the network. As more
and more people and their many devices access wireless internet, clogged airwaves are
going to make it.
One German physicist ,DR. Harald Haas, has come up with a solution he calls ―Data
Through Illumination‖—taking the fiber out of fiber optics by sending data through an
LED light bulb that varies in intensity faster than the human eye can follow. It’s the same
idea behind infrared remote controls, but far more powerful.
Haas says his invention, which he calls D-Light, can produce data rates faster than 10
megabits per second, which is speedier than your average broadband connection. He
envisions a future
where data for laptops, Smartphone’s, and tablets is transmitted through the light in a
room. And security would be a snap—if you can’t see the light, you can’t access the
data.
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2. 1. INTRODUCTION:
Li-fi basically known as ―LIGHT FEDILITY‖ is an outcome of twenty first
century. The basic ideology behind this technology is that the data can be
transmitt ed through LED li ght whose int ensit y varies even faster than the
human eye. As the transmission of the data takes place through the light emitting diodes
(LED’s) the amount is comparatively small .In modern times, it is called as the optimized
version of WI-FI .The advantageous thing is the wireless communication which decreases
the cost enormously. HARALD HASS, who is considered to be the father of Li-fi from
university of Edinburgh, UK says that the heart of this technology lies in the intensity
and the potential of the light emitting diodes. The major reason which lead the modern
man through this invention is that the confinement of Wi-Fi to comparatively small
distance. As there are more and more devices coming up day-by-day the signals are
being clogged up due to heavy traffic, there arised a need for an error free transmission
technology. And the solution to this problem was the Li-fi technology.. It has been
designed in such a way that it overcomes the disadvantages that occurs during the usage
of wi-fi. In general terms, Li- fi works even under water thereby causing a great benefit
to the military operations.
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3. The phycists envisions that this technology would make a great difference between the
assumption and the proof in this case .The demonstration took place using two Casio
smart phones. The data was made to exchange between the phones using light. Even
though the distance was nominal, it is sure that there would be a rapid increase in the
distance of transmission.AS there is a limited amount of Radio based wireless spectrum
available, a number of companies formed a consortium called Li-fi consortium in order
to promote high speed optical wireless systems .The members of this consortium
believes that a speed of 10 Gbps can be achieved in no time. If this would be possible
then a high clarity image would take about 30 seconds to download!!
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4. 2. HISTORY:
Haraald Haas continues to hit the world that there is a possibility for communication
through light.LI-FI technology has the possibility to change how we access the internet,
stream videos, receive emails and much more. The technology truly began during the
1990's in countries like Germany, Korea, and Japan where they discovered LED's
could be Haraald Haas continues to
hit the world that there is a possibility for
communication through light.LI-FI technology has the possibility to change how we
access the internet, stream videos, receive emails and much more. The technology truly
began during the 1990's in countries like Germany, Korea, and Japan where they
discovered LED's could be retrofitted to send information. This type of light would
come in familiar forms such as infrared, ultraviolet and visible light.
Research into VLC has been conducted in earnest since have shown that LEDs can
be electronically adapted to transmit data wirelessly as well as to provide light. VLC
is faster, safer and cheaper than other forms of wireless internet, advocates say -- and so
could eliminate the need for costly mobile-phone radio masts.
Fig 1. Haralad Hass
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5. Haas has a small lab stuffed with equipment, including the now-famous table lamp and
its box of electronics. It was here in 2007 that his research assistant, Mostafa
Afgani, first sent data using light signals. Haas's invention centres on how these
signals are modulated: the information, embedded within visible light emitted from the
LEDs, is trans- mitted by means of many subtle changes made to the intensity of the
light at the ultra-high rate of 100 million cycles per second (100MHz). The photodetector in Haas's box monitors these tiny variations and converts them back into a
digital signal, from which the transmitted information is extracted.
In October 2011 a number of companies and industries formed the Li-Fi
Consortium, to promote high-speed optical wireless system sand to enhance the limited
bandwidth provided by radio-based wireless spectrum available. The consortium
believes it is possible to achieve more than 10Gbpsspeed using this optical wireless
technology also known as Li-Fi. The communication is done by deploying transmit- ter
and receiver in direct line of sight manner. It gets affected if line of sight is not used,
the speed of data transmission will reduce or data transmission will stop. It is also
more secure than other wireless net- works as only photo receptors are used, which
can receive data within transmitted cone of light signals.
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6. 3 .WORKING OF LI-FI
In order to know the working of Li-fi we need to know the necessity for Li-fi .With
the vast development in living the use of gadgets and invention of new gadgets is
increasing which lead to the technological developments.
FIG: 2 Construction of lifi technology
There are many situations in which people get frustrated with the dull performance
signals of Wi-Fi at a place with many network connections in seminars conferences
etc. Li fi fulfills these needs .this fantabulous idea first striked the mind of Harald
Haas from University of Edinburgh, UK, in his TED Global talk on VLC.His idea was
very simple that if the LED is ―on‖ then the digital 1 can be transmitted and if the led
is ―off‖ then the digital 0 can be transmitted. Led’s can be switched on and off very
quick. For transmitting data this way all that we require is LED’s and controller that
code data into Led’s. Parallel data transmission can be done by using array of LED’s
or by using red, green, blue LED’s to alter light frequency with the frequency of
different data channel. Advancements and enhancements in this field generate a speed
of 10 gbps! But amazingly fast data rates and lowering band widths are not the only
reasons that enhance this technology. Lifi usually is based on light and so it can be
probably implemented in articrafts and hospitals that are prone to inference from radio
waves. Unlike Wi-Fi Li-Fi
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can work even under- water which makes it more
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7. advantageous for military operations. Radio waves are replaced by light waves in data
transmission called Li- Fi.
Light emitting diodes can be switched on and off very much faster than the human eye
allowing the light source to appear continuously. The data transmission is done through
binary codes which involve switching on LED can be done by logic 1 and switch off
using logic 0.The encoding of information in light can therefore be identified by
varying the rate at which the LED’s flicker on and off to give strings of 0’s and
1’s.visible light communication is this method of using rapid pulses of light to
transmit information wirelessly.
3.1 Visible Light Communication:
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.
Fast pulses are used for wireless transmission. Communication system components are:
1. A high brightness white LED which acts as a communication source
2. Silicon photo diode which shows good response to visible wavelength region.
LED illumination can be used as a communication source by modulating the LED light
with the data signal. The LED light appears constant to the human eye due to the fast
flickering rate. The high data rate can be achieved by using high speed LED’s and
appropriate multiplexing tech- niques. Each LED transmits at a different data rate which
can be in- creased by parallel data transmission using LED arrays. Many different
reasons exist for the usage of LED light in spite of fluorescent lamp, incandescent bulb
etc which are available.
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8. Fig 3: Transfer of data in the form of 0’s and 1’s
3.2 Present Scenario:
 We have 1.4 million 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 WiFi uses Radio Waves for communication
 It is important to look into this technology which has become fundamental to our life
Four Issues with radio waves
1. Capacity :





We transmit wireless data through radio waves
Radio waves are limited
Radio waves are scar and expensive
We only have a certain range of it
With the advent of the generation technology as of like of 2.5G,3G,4G and so on
we are running out of spectrum.
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9. 2. Efficiency :
 There are 1.4 million cellular radio base stations
 They consume massive amount of energy
 Most of this energy is not use for transmission but for cooling down the
base stations
 Efficiency of such a base station is only 5% and that raise a very big
problem
3. Availability :
 Availability of radio waves or rf singnals causes another 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 penetrates through walls
 They can be intercepted
 If someone has a knowledge and bad intentions than he may misuse it
Alternative to radio waves in Electromagnetic spectrum
 So 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 part of electromagnetic spectrum
 So let’s look up at this in context of EM spectrum
Radio
waves
Infra red
Visible
Ultra violet X rays
Gamma
rays
Electromagnetic spectrum
 Gamma rays are simply very dangerous and thus can’t be used for our purpose of
communication
 X-rays are good in hospital and can’t be used either
 Ultra –violet rays are sometimes good for our skin but for long duration it is
dangerous
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10.  Infra red rays are bad for our eyes and are therefore use at low power levels
 We have already seen shortcoming of radio waves
So we are left with only visible light spectrum.
Light for WiFi communication
 Light has been around for millions of years.
 It has created us, has created life and has created all stuffs of life.
 FLICKERING lights are annoying but they may have an upside. Visible light
communication(VLC) uses rapid pulses of light to transmit information
wirelessly, now it may be ready to compete with conventional WIFI.
 So it is inherently safe use and would be great if we can use it for our wireless
communication.
What we have to do?
 We have to replace inefficient fluorescents lights with this new dignitaries of
LED lights.
 It is a semi conductive e-device.
 The LED bulb will hold a micro chip that will do the job of processing the
data.
 Light intensity can be modulated at very high spends to send data tiny changes
in amplitude.
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11. How we do this?
 Remote control has as IR-led
 It creates a single data stream.
 High speed data rates of 10000 b/s to 20000b/s
 Replace remote control with light box
 With this technology we transmits 1000’s of data stream in parallel at high
speeds.
 We termed this technology as special Modulation.
3.3 comparisons between LIFI AND WIFI:
LIFI 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
wifi,only 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 areas and
for relieving interference issues, so the two technologies can be considered
complimentary.
Technology
Wireless(current)
Wi-Fi- IEEE 802.11n
Bluetooth
IrDA
Wireless(future)
wiGig
Giga-IR
Li-Fi
Speed
Data density
150 Mbps
3 Mbps
4 Mbps
*
*
***
2 Gbps
1 Gbps
>1 Gbps
**
***
****
Comparision table of wifi & lifi technology
The table also contains the current wireless technologies that can be used transferring
data between devices today,i.e Wi-Fi, Bluetooth and IrDA. Only WI-FI currently offers
very data rates. The IEEE 802.11n in most implementations provides up to 150Mbps
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12. although in practice you receive considerably less than this. Note that one out of three of
these are an optional techonology
3.4 Replacement
for others technologies
This technology doesn’t deal with radio waves, so it can easily be used in the places
where Bluetooth, infrared, WIFI and Internet 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.
Li-Fi is the upcoming and on growing technology acting as competent for various
other developing and already invented technologies. Since light is d major source for
transmission in this technology it is very ad- vantageous and implementable in various
fields that can’t be done with the Wi-Fi and other technologies. Hence the future
applications of the Li-Fi can be predicted and extended to different platforms like
education
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13. 4. APPLICATIONS:
There is a wide necessity for data transfer and by the end of the day every field
involves the use of technologies. One such technology is Li-Fi which can have its
applications extended in areas where the Wi-Fi tech- nology lack its presence like
medical
technology, powerplants and various other areas where Li-Fi proved it
excellence of the undersea awesomeness.
At present its applications ate beyond imagination but still if to think about few then
they are :
 Can be used in the places where it is difficult to lay the optical fiber like
hospitals. In operation theatre LiFi can be used for modern medical
instruments.
 In traffic signals LiFi can be used which will communicate with the LED
lights of the cats and accident numbers can be decreased.
 Thousand and millions of street lamps can be transferred to LiFi lamps to
transfer data.
 In aircraft LiFi can be used for data transmission.
 It can be used in petroleum or chemical plants where other transmission or
frequencies could be hazardous.
4.1 Future applications:
4.1.1 Education systems:
As with the advancement of science the latest technology is the LIFI which is the
fastest speed internet access service. so this will leads to the replacement of WIFI at
institutions and at companies so that all the peo- ple can make use of LIFI with same
speed intended in a particular area.
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14. 4.1.2 Extends our life span:
As operation theatres do not allow WIFI due to radiation concerns. Usage of WIFI
at hospitals interferes with the mobile and pc which blocks the signals for
monitoring equipments. Therefore the replacement for this WIFI is Li-Fi as Hass
has mentioned in his TED TALK that LIFI has 10,000 times the spectrum of
WIFI. Because the lights are not only allowed in operation theatres but also the most
dazzling fixtures in the room.
4.1.3 Reduction in accident numbers:
At traffic signals, we can use LIFI in order to communicate with LED lights of the
cars by the number of accidents can be reduced. Data can be easily transferred by
making use of LIFI lamps with the street lamps.
4.1.4 Replacement for others technologies:
This technology doesn’t deal with radio waves, so it can easily be used in the
places where Bluetooth, infrared, WIFI and Internet 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
Li-Fi is the upcoming and on growing technology acting as competent for
various other developing and already invented technologies. Since light is d
major source for transmission in this technology it is very advantageous and
implementable in various fields that can’t be done with the Wi-Fi and other
technologies. Hence the future applications of the Li-Fi can be predicted and
extended to different platforms like education.
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15. 5 .CONCLUSION:
Li-Fi is the upcoming and on growing technology acting as competent for various
other developing and already invented technologies. Since light is d major source for
transmission in this technology it is very advantageous and implementable in various
fields that can’t be done with the Wi-Fi and other technologies. Hence the future
applications of the Li-Fi can be predicted and extended to different plat- forms like
education fields, medical field, industrial areas and many other fields. The
possibilities are numerous and can be explored further. If this technology can be put
into practical use, every bulb can be used something like a Wi-Fi hotspot to transmit
wireless data and we will proceed towards the cleaner, Greener, Safer and Brighter
future.
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16. 6.REFERENCES:
1. http://en.wikipedia.org/wiki/Li-Fi
2. http://www.scribd.com/doc/88377913/Synopsis-on-Lifi-The-latesttechnology-in-wireless-communication.
3. http://www.scribd.com/doc/88340668/Seminar-Report-on-LiFi
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