Professor, A solution to this problem is by the

Professor, Sathyabama University

 Super markets have a variety of
goods. Whether shopkeeper doesn’t know about the product because of don’t have
adequate knowledge in product so we have remedy for how to handle this
situation. Most recently LIFI is new emerging technology in the trend. This technology
is used here for finding out the information of the commodities. Here data
transfer is processed between products and the system. Each and every product
is having LIFI transmitter and it store the encoded data similar to the product
id, cost of product and rest of the details about the product.  After completing the purchase the product is
shown in the LIFI device and product details automatically updated in the
system not only that system also pronounce the product name without help of
shopkeeper.

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Keywords:   Li-Fi transmission .

Introduction:  

Transfer of data from one place to another is one of the most important
day-to-day activities. The current wireless networks that connect us to the
internet are very slow when multiple devices are connected. As the number of
devices that access the internet increases, the fixed bandwidth available makes
it more and more difficult to enjoy high data transfer rates and connect to a
secure network. But, radio waves are just a small part of the spectrum
available for data transfer. A solution to this problem is by the use of Li-Fi.
Li-Fi stands for Light-Fidelity. Li-Fi is transmission of data through
illumination by 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. Li-Fi is the term some have used to label
the fast and cheap wireless communication system, which is the optical version
of Wi-Fi. Li-Fi uses visible light instead of Gigahertz radio waves for data
transfer.

The idea of Li-Fi was introduced by a German physicist, Harald Hass,
which he also referred to as ?data through illumination?. The term Li-Fi was
first used by Haas in his TED Global talk on Visible Light Communication.
According to Hass, the light, which he referred to as D-Light, can be used to
produce data rates higher than 10 megabits per second which is much faster than
our average broadband connection Li-Fi can play a major role in relieving the
heavy loads which the current wireless systems face since it adds a new and
unutilized bandwidth of visible light to the currently available radio waves
for data transfer. Thus it offers much larger frequency band (300 THz) compared
to that available in RF communications (300GHz). Also, more data coming through
the visible spectrum could help alleviate concerns that the electromagnetic
waves that come with Wi-Fi could adversely affect our health. Li-Fi can be the
technology for the future where data for laptops, smart phones, and tablets
will be transmitted through the light in a room. Security would not be an issue
because if you can’t see the light, you can’t access the data. As a result, it
can be used in high security military areas where RF communication is prone to
eavesdropping.

 

Materials & Methodology:

A
key to the commercial adoption of LiFi in applications such as the
Internet-of-Things (IoT), 5G and beyond, light as a service (LaaS) in lighting,
car-to-car communication, security and defence, underwater communication and
wireless interconnects in data centres, is the availability of low cost and low
power miniaturised transceiver technology. It is therefore essential to develop
LiFi ASICs. In this section, to the authors’ best knowledge, a first
transmitter ASIC and receiver ASIC based on complementary metal oxide
semiconductor (CMOS) technology are presented. Both chips have recently been
developed as part of the UK Engineering and Physical Sciences Research Council
(EPSRC) ultra-parallel visible light communication (UPVLC) project.

A. Transmitter chip

Conventional
circuits that support OFDM or PAM involve a DAC to generate high-speed signals.
Typical DAC structures can only deliver up to 30 mA current 30, and they
require an additional stage of current amplifier in order to drive a typical
LED.

          

             An open-drain 8-bit current steering
DAC-based LED driver using CMOS technology has been developed, and it omits the
additional current amplifier. The ASIC is capable of achieving 250 MS=s at a
maximum full-scale current of 255 mA and exhibits a power efficiency of 72%. A
differential optical drive is implemented by employing both current steering
branches of the DAC to drive two different colour LEDs. This doubles the signal
level and efficiency over a single ended approach, and enables the transmitter
configuration described. The chip has four separate driver channels. Each
channel is capable of driving up to two LEDs allowing for CSK, lighting colour-temperature
adjustment and a multiple input multiple output (MIMO) system.

The
distance between the LED and the receiver is 1 m. As expected, an increase in
the full-scale current results in a higher optical output power and, hence,
higher SNR at the receiver. The system is subject to non-linear distortions at
the transmitter and the receiver. Therefore, an SNR of about 25 dB is required
to achieve an uncoded BER of 10.3.The BER does not improve when the current reaches about 250
mA due to saturation effects. It has been shown thatit is possible to transmit
1 Gb=s when using all four driversin parallel in a MIMO configuration.

B. Receiver chip

LiFi
systems are based on IM/DD. As a consequence, the average transmit power is
proportional to the transmit signal amplitude, and not the square of the signal
amplitude. The electrical path loss is hence twice the optical path loss.
Therefore, in order to achieve reasonable distances in an attocell network,
receiver devices with sufficiently high sensitivity are required. Based on
computer modelling, it is indicated that an avalanche photodetector (APD)-based
receiver with a typical input referred noise
density of 10 pA/pHz is necessary for reliable communication. A LiFi receiver
chip composed of 49 APD detectors (a 7 _ 7 detector array) based on 180 _m CMOS
technology has been developed. The size of each APD element is 200 _m _ 200 _m
placed on a 240 _m grid. The responsivity of the nine APDs at the central core
is 2:61 A=W at 450 nm. An APD gain of 10 dB is achieved at a reverse bias
voltage of only 10 V. Each APD is connected to an integrated transimpedance
amplifier (TIA) based on a shuntshuntfeedback topology with fixed gain in order
to obtaingood performance. The APDs achieve a bandwidth of 90 MHz.The APDs
outside the central core exhibit different coloursensitivities. Also, there are
several APDs at the fringe (numbers6, 8 and 42–48) that are exposed to a
specially designedmetal grading structure to achieve enhanced directionality
forangular diversity receiver algorithms.

 

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.

 

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-Fiwith 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
roboticsurgeries 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 1. 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 1. 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 bedecreased 1. Also, LED car lights can alert drivers when other vehicles
are too close.

h) 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.