How a
mobile phone makes a call,
of
mobile communications?
Let's explore the technology behind
mobile communications.
MOBILE COMMUNICATION
When you speak on your phone,
your voice is picked up by your
phone's microphone.
The microphone turns your voice into
a digital signal
with the help of MEMS sensor and IC.
The digital signal contains your
voice
in the form of zeros and ones.
An antenna inside the phone receives
these zeros and ones
and transmits them in the form of
electromagnetic waves.
Electromagnetic waves transmit the
zeros and ones
by altering the wave
characteristics,
such as the amplitude, frequency,
phase,
or combinations of these.
For example, in the case of
frequency,
zero and one are transmitted
by using low and high frequencies
respectively.
So, if you could find a way
to transmit these electromagnetic
waves
to your friend's phone,
you would be able to establish a
call.
However, electromagnetic waves
are incapable of traveling long
distances.
They lose their strength due to the
presence
of physical objects, electrical
equipment,
and some environmental factors.
ENVIORNMENTAL FACTORS
In fact, if there were no such
issues,
even then, electromagnetic waves
would not carry on forever,
due to the Earth's curved structure.
To overcome these issues, cell
towers were introduced,
using the concept of cellular
technology.
CELLULAR TECHNOLOGY
In cellular technology,
a geographic area is divided into
hexagonal cells
with each cell having its own tower
and frequency slot.
Generally, these cell towers are
connected through wires,
or more specifically, optical fiber
cables.
These optical fiber cables are laid
under the ground
or the ocean,
to provide national or international
connectivity.
The electromagnetic waves produced
by your phone
are picked up by the tower in your
cell
and convert them into high frequency
light pulses.
These light pulses are carried to
the base transceiver box,
located at the base of the tower
for further signal processing,
After processing, your voice signal is
routed
towards the destination tower.
Upon receiving the pulses,
the destination tower radiates it
outwards
in the form of electromagnetic
waves,
and your friend's phone then
receives the signal.
This signal undergoes a reverse
process,
and your friend hears your voice.
So, it's true that mobile
communications
are not entirely wireless,
they do use a wired medium too.
This is how mobile communications
are carried out.
However, there was a big issue
that we intentionally left
unanswered.
Mobile communication is only
successful
when your tower transfers the signal
to your friends tower.
But how does your tower know
in which cell tower area your friend
is located?
Well, for this process, the cell
tower gets help
from something called a mobile
switching center.
MOBILE SWITCHING CENTER (MSC)
The MSC is the central point of a
group of cell towers.
Before moving further,
let's explain more information about
the MSC.
When you purchase a SIM card,
all the subscription information
is registered in a specified MSC.
This MSC will be your home MSC.
The home MSC stores information such
as service plans,
your current location, and your
activity status.
If you move outside the range of
your home MSC,
the new MSC, which serves you
instead,
is known as a foreign MSC.
As you enter a foreign MSC region,
it communicates with your home MSC.
In short, your home MSC always knows
which MSC area you are in.
To understand in which cell location
the subscriber is
LOCATION UPDATE
within the MSE area,
the MSC uses a few techniques.
One way is to update the subscriber
location
after a certain period.
Now, let's discuss why the frequency
spectrum
FREQUENCY SPECTRUM
is quite important in mobile phone
communications.
To transfer zeros and ones in
digital communication,
each subscriber is allocated a
frequency range.
However, the frequency spectrum
available
for cellular communications is quite
limited,
and there are billions of
subscribers.
This issue is solved with the help
of two technologies,
one frequency slot distribution,
1. FREQUENCY SLOT DISTRIBUTION
and two, multiple access technique.
In the first technique,
different frequency slots are
carefully allocated
to different cell towers.
In the multiple access technique,
this frequency slot is efficiently
distributed
amongst all the active users in the
cell area.
Now, the big question.
MOBILE GENERATIONS
Why are there different generations
of mobile phone technologies?
1G originally allowed users, for the
first time,
FIRST GENERATION
to carry a phone without a cable
attached to it.
But 1G suffered from two major problems.
The first problem was that the
wireless transmission
was in an analog format.
Analog signals that are easily
altered by external sources.
So, it provided poor voice quality
and poor security.
The second problem was that it used
the frequency division multiple
access technique,
which used the available spectrum in
an inefficient way.
These factors paved the way for the
second generation
SECOND GENERATION
of mobile communications,
2G used digital multiple access
technologies, namely TDMA,
or CDMA technology.
The second generation
also introduced a revolutionary data
service, SMS,
and internet browsing.
3G technology was focused
THIRD GENERATION
on giving a higher data transfer
speed.
It used a WCD multiple access
technique,
along with an increase in bandwidth.
To achieve this, the 3G speed of two
Mbps
allowed the transfer of data for
uses
such as GPS, videos, voice calls, et
cetera.
3G was a huge step in the
transformation
of the basic phone to a smartphone.
Next came 4G, which achieved speeds
of 20 to 100 Mbps.
This was suitable for high
resolution movies and television.
This higher speed was made possible
due to the OFD multiple access
technology,
and MIMO technology.
MIMO uses multiple transmitter
receiver antennas
inside both the mobile phone and the
towers.
The next generation of mobile
communication, 5G,
FIFTH GENERATION
to be rolled out soon,
will use enhanced MIMO technology
and millimeter waves.
It will provide seamless
connectivity
to support the internet of things,
such as driverless cars and smart
homes.
Thank you.
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