mobile network technology

8/9/2019 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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