mobile network technology
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MOBILE TECHNOLOGY
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Mobile Network TechnologyMobile Network Technology
Mobile phones and their network vary very significantly
from provider to provider and country to country.
However the basic communication method of all ofthem is through the electromagnetic microwaves with a
cell base station.
The cellular companies have large antennas, which are
usually mounted over towers, buildings and poles.
The cell phones have low-power transceivers that
transmit voice and data to the nearest sites usually
within the 5 to 8 miles (8 to 13 kilometers away).
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Multiple Access Technique
Multiple Access Achieved by dividing the available radio
frequency spectrum, so that multiple users can be given
access at the same time.
FDMA - Frequency Division Multiple Access
TDMA - Time Division Multiple Access
CDMA - Code Division Multiple Access
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EXAMPLE
An analogy to the problem of multiple access is a room(channel) in which people wish to communicate with eachother. To avoid confusion we can follow various ways:
People could take turns speaking (time division).
Speak at different pitches (frequency division).
In CDMA, they would speak different languages. People
speaking the same language can understand each other, butnot other people. Similarly, in CDMA, each group of users isgiven a shared code. Many codes occupy the same channel,but only users associated with a particular code canunderstand each other.
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CDMA (CODE DIVISION
MULTIPLE ACCESS)
A method for transmitting simultaneous digital
signals over a shared portion of the spectrum.
The most widely known application of CDMA is
for cellular systems.
As of 2008, there were more than 450 million
CDMA cellphone users in the world, with more
than half in Asia.
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Spread Spectrum
CDMA's spread spectrum technique overlaps
every transmission on the same carrier
frequency by assigning a unique code to each
conversation.
The often-used analogy for this is your ability to
detect your own language in a room full of
people speaking other languages.
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WORKING OF CDMA
Generally, CDMA converts analog voice
signal to a digital signal, encodes the
digital signals, and separates voice andcontrol data into data streams called
channels.
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Generating a CDMA signal is a five steps
process:
1. Analog to digital conversion or A/D 2. Voice coding or Vocoding
3. Encoding and interleaving
4. Channelizing
5. Digital to radio frequency (RF) conversion
D/A
RFSpreader
Code
generator
InterleavingVocoderA/D
converter
Channelize
voice
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CDMA PHONES
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GSM (Global System for Mobile
Communications)
GSM was first introduced in the Finland in the yearof 1991. GSM mobile phones operate on the TDMAsystems.
In the TDMA (time division multiple access system),multiple users can access single radio frequencywithout any interference.
It is a hugely successful wireless technology in the
world. GSM has become the worlds largest growing
communication technology and it has beenexpanded in more than 214 countries of the world.
The TDMA technology provides the individual time
slot within a specific channel for each user.
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Time division multiple access(TDMA)
Time division multiple access (TDMA)
It allows several users to share the samefrequency channel by dividing the signal intodifferent timeslots
. The users transmit in rapid succession, one afterthe other, each using his own timeslot.
This allows multiple stations to share the sametransmission medium while using only the partof its bandwidth they require.
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TDMA
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GSM phones use a Subscriber
Identity Module (SIM) smart card
that contains user account
information.
Any GSM phone becomes
immediately programmed after
plugging in the SIM card, thus
allowing GSM phones to be easily
rented or borrowed.
SIM CARD IN GSM MOBILE
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NOKIA 6680
NOKIA 6600
SAMSUNG C200
GSM PHONES
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MOTOROLA L7
LG 2600
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