Mobile phone function are as below:
brands. This discussion does not include the extra components of a mobile phone like video camera and
its related function, radio, music player and external memory. The topic is limited for mobile
telecommunication only how its works and their interdependence.
There are three major sections inside a mobile phone
A power section deals with power related tasks such as power distribution or charging the battery so
section can be divided into two sub sections like.
A power distribution section is built around an "power IC" it takes 3.6V power from battery and
power and then distributes to the other components used in mobile phone circuit. in some mobile
tech "RF Power amplifier" uses more Power than provided bye mobile phone's battery .i.e. 4.7 V or 5.6 V
some phones. the power Ic with a power boaster coil is used to increase voltages. so we can say that
power IC is used to provide power to other components how much they needed. either less than battery
voltage or more than it.
A charging section works for battery charging purposes.it is often consists a fuse, a coil, a protecting
a filter capacitor and charging IC and some other discreet. the charging section helps battery to be
when it needs and when battery is charged, charging IC reads its state of charge and feels it full charged
and then disconnects charging from it.
A radio section has basically a set of four main functions.wich are.
RF Power Amplification
In the modern mobile phone communication techniques. the frequency of mobile phone
communication is divided into three bands
GSM (operates on 900 MHz)
DCS (operates on 1800 MHz)
PCS (operates on 1900 MHz)
DCS means Distributed control system.Its is state of the art technology to control almost any kind of
process through various controllers.
the third band is used only in USA whereas the first two bands are used in the rest of the world. band
switching is done bye a "ceramic
antenna switch" it reads from the radiation dispersed in the air and then switches to the appropriate
in the very first phase of mobile phones there were single band handsets which operated on single
frequency band but now a days all
the handsets are dual band or tri band in operation.
RF Power Amplifier
RF power amplifier is often called as ".PA" or"Transmitter" its functions is to amplify or boast the power
which is being transmitted to
air, so may it would be able to communicate with long distances. a typical .PA can amplify rf power up to
0.6W or 600mW. This amount
of rf power is sufficient to communicate nearly 20 to 25 kilometers in open area, but all the PA's are
controlled by there rf signal
processor, so if we are near our cell base tower the PA of our phone will transmit low power but if we
are far away it will produce its
A mobile phone's rf section is basically built around an rf IC which is often called rf signal processor
whereas in nokia it is called hagar
IC in some hand sets and in some hand sets it is called Mjoelner. irrespectively of the brands and verity
of names we call it rf signal
processor. this IC works as transmitter and receiver as well. working as transmitter it takes instructions
from phone's computer and
also takes audio data from audio section and creates radio waves then mixes audio data to its radio
waves according to the
instructions given by computer section. this mixer of audio and radio is sent to PA to amplify its strength
A reciver section for rf waves is built in rf IC, as it is said that this IC works for dual purposes first
transmitting and section recieving. in
the recieving section of mobile phones a radio signal is gather from ceramic antenna switch and then it
is filtered and sent to rf IC to
further process. in rf IC signal is detected and then rectified for audio and data which is sent to audio IC
or computer section.
A computer section in mobile phone consists of two main functions
CPU(central processing unit)
Memory (RAM, FLASH, COMBO CHIP)
A CPU is used in mobile phones as a central processing arithematic or controler. the cpu controls various
functions in mobile phones
like signal, display, sound converting(DSP), charging, power on, rf channel controler, rf tx power
conroller, LEDs, vibrator, data
processing, data storing etc. so we can say that if a cpu is damaged in any mobile phone it cannot be
repaired unless the CPU is not
replaced but this type of fault is not even seen to me ever either memory chips can be damaged. in
brand Nokia CPU is named with
two different words (MAD or UPP)
there are two main types of memories used in mobile phones
RAM (Random Access Memory)
The RAM is used in mobile phones to store user data in mobile phones. So these a days we can store
pictures, messages, ringtones,
applications, themes and other these type of things in mobile phones so CPU stores these types of data
in the RAM of our mobile
Flash (eeprom, ROM etc)
The flash chip is used in mobile phones to hold mobile phone's operating system in it. so if the flash chip
is damaged in mobile
phones the phone cannot power on properly because all the instructions to start a mobile phones and
its various tasks like call
making , display etc are stored in the flash chip of mobile phones.
In smoe mobile phones there is a combined type of memory used which is called combo memory chips
these types of memories
work for both like RAM and Flash.The clear example of this type of memory is used in Nokia 1100.
Note: Multy Media Cards are not a part of mobile phones becaues they are used externally.
How A GSM Cellular Network Operates
GSM 900/DCS 1800 networks use a sophisticated array of digital equipment to provide you with a
seamless, hiss-free connection.
Below are some of the critical components & procedures that allow them to do so:
GSM (Global System for Mobile Communications) uses a series of
radio transmitters called Base Stations (BS) to connect you and your
cellphone to your cellular network.
Each BS is also termed a CELL so named because it covers a certain
range within a discrete area (cell).
Base Stations are all interconnected, which is why you can move from
one cell to another - a process called "hand-over" – without losing your
Base Station Controller: A set of Base Stations is connected to a
particular Base Station Controller.
MSC :The combination of a cellphone and the SIM card creates a special
digital "signature" - that includes your subscriber number - which is sent
from your cellphone to the nearest BS asking that you as a subscriber of
a particular network be allowed to use the network. The request is
passed on along the network of BSs to the multifaceted heart of a
cellular network -the Mobile Switching Center (MSC).
The MSC also routes all your incoming and outgoing calls to and from the
fixed-line networks or other cellular networks.
HLR :The MSC also contains a critical component called the Home
Location Register (HLR) which provides the administrative information
required to authenticate, register and locate you as a that network's
subscriber. Once it’s received your log-on request, the HLR immediately
checks the special "signature" contained in the request against it’s
special subscriber database.
If your subscription is current, the MSC sends a message back to the phone via the network of BSs that
indicates that you’re allowed
to access the network.
The name or code of that network will appear on the LCD screen of the cellphone.
Once this network "name" message appears on your phone’s LCD screen, it means you’re connected to
the network and able to
make and receive calls.
The entire log-on process usually takes only a couple of seconds.
Polling: At the same time, the HLR also registers which BS your cellphone is currently connected to, so
that when the network’s
MSC needs to route an
incoming call to your cellphone number, it will first check the HLR to see where you are.
Every now and gain, the cellphone will send a message to the network indicating where it is, a process
Multiplexing Each BS uses digital techniques to enable a number of phones to be simultaneously
connected to it, as well as
simultaneously allowing a number of subscribers to make and receive calls.
This sophisticated digital call-juggling ability is called Multiplexing.
However, the combination of the tracking function and your unique digital signature allows the MSC to
route that call to the precise
BS your cellphone happens to be connected to, and then exclusively to your cellphone - even if a
number of other subscribers are
simultaneously connected to that BS.
Hand Over: When you "hand-over" to another cell whilst driving, the HLR is automatically updated, and
continues to monitor where
exactly it should route your calls should you then move within range of another BS.
This sophisticated routing procedure means that out of hundreds of thousands of subscribers, only the
correct cellphone will ring
VLR: When you want to make an outgoing call, another section of the MSC called the Visitor Location
Register (VLR) checks
whether you are actually allowed to make that call.
For example, if you are barred for international dialing, a message to that effect will be generated by the
VLR, sent along the
network, and almost instantly back to your cellphone.
MailBox: If you’re unavailable for some reason and your Mailbox has been activated, any incoming voice
calls will be transferred to
the Mail system.
SMSC: Some VoiceMail systems are linked to a network's SMS Center (SMSC), a special facility that
handles Short Messages. The
SMSC generates the special SMS message that notifies you that you have mail waiting in your Mailbox.
SMS messages can be received on your SMS-capable cellphone even while you’re on a voice call. That’s
because they are sent on
a different radio frequency - the GSM data channel - than voice calls, so that the two never interfere.
These sophisticated digital facilities are the reason why GSM is now considered the de facto global
We hope the topic is of great help to you.