3. INTRODUCTION
•A cellular network is a radio network made up of
a number of radio cells (or just cells) each served
by at least one fixed-location transceiver known as
a cell site or base station.
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4. Example
An example of a simple non-telephone cellular
system is an taxi driver's radio system where the taxi
company has several transmitters based around a city
that can communicate directly with each taxi.
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5. WORKING
MSMobile station; BSTBase station transceiver; MSCMobile switching center; BSCBase station controller; PSTNPublic
switched telephone network
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6. BENEFITS
More capacity due to spectral reuse
Lower transmission power due to smaller
transmitter/receiver distances
reduced power usage
larger coverage area
reduced interference from other signals
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7. CHARACTERISTICS
PAGIN
G
• Paging takes place by sending the broadcast message to
all of the cells.
• In mobile telephony systems, the most important use of
broadcast information is to set up channels for one to one
communication between the mobile transceiver and the
base station.
• Paging messages can be used for information transfer.
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8. FREQUENCY REUSE
•FDMA
•Frequency Division Multiple
Access or FDMA is a channel
access method used in
multiple-access protocols as a
channelization protocol.
•FDMA gives users an
individual allocation of one or
several frequency bands,
or channels. Multiple Access
systems coordinate access
between multiple users.
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9. •CDMA
• Code division multiple
access (CDMA) is a channel
access method utilized by various
radio communication
technologies.
• It should not be confused with
the mobile phone standards
called cdmaOne and CDMA2000
(which are often referred to as
simply "CDMA"), which use
CDMA as an underlying channel
access method.
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10. • TDMA
• Time division multiple access. A method of digital wireless
communications transmission that allows a large number of
users to access (in sequence) a single radio frequency
channel without interference by allocating unique time slots
to each user within the channel. Each frequency is broken
into time slots through which bits of data flow.
• TDMA is used in second generation wireless phone systems,
such as GSM and TDMA.
• TDMA cannot be used to separate signals from one cell to
the next since the effects of both vary with position and this
would make signal separation practically impossible.
• Time division multiple access, however, is used in
combination with either FDMA or CDMA in a number of
systems to give multiple channels within the coverage area
of a single cell.
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11. MOVEMENT FROM CELL TO CELL &
HANDOVER
•RADIO TAXI NETWORK
•In a primitive taxi system, when the taxi moved away from a
first tower and closer to a second tower, the taxi driver
manually switched from one frequency to another as needed.
If a communication was interrupted due to a loss of a signal,
the taxi driver asked the base station operator to repeat the
message on a different frequency.
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12. MOVEMENT FROM CELL TO CELL &
HANDOVER
•CELLULAR NETWORK
•In a cellular system, as the distributed mobile transceivers
move from cell to cell during an ongoing continuous
communication, switching from one cell frequency to a
different cell frequency is done electronically without
interruption.
•This is called the handover or handoff.
13. MOBILE PHONE NETWORKS
The most common example of a cellular network is a mobile
phone (cell phone) network.
A mobile phone is a portable telephone which receives or makes calls
through a cell site (base station), or transmitting tower.
Since almost all mobile phones use cellular technology,
including GSM, CDMA, and AMPS (analog), the term "cell phone" is
in some regions, notably the US, used interchangeably with "mobile
phone".
However, satellite phones are mobile phones that do not
communicate directly with a ground-based cellular tower, but may do
so indirectly by way of a satellite.
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14. MOBILE PHONE NETWORKS
(Contd.)
There are a number of different digital cellular technologies,
including:
Global System for Mobile Communications (GSM)
General Packet Radio Service (GPRS)
Code Division Multiple Access (CDMA)
Evolution-Data Optimized (EV-DO)
Enhanced Data Rates for GSM Evolution (EDGE or GSM EDGE)
3GSM
Digital Enhanced Cordless Telecommunications (DECT)
Digital AMPS (IS-136/TDMA)
Integrated Digital Enhanced Network (iDEN).
15. CDMA
Interim Standard 95 (IS-95) is the first CDMA-based digital cellular
standard pioneered by Qualcomm. The brand name for IS-95
is cdmaOne.
It is a 2G Mobile Telecommunications Standard that uses CDMA,
a multiple access scheme for digital radio, to send voice, data and
signaling data (such as a dialed telephone number) between
mobile telephones and cell sites.
CDMA or "code division multiple access" is a digital radio system that
transmits streams of bits (PN codes).
CDMA permits several radios to share the same frequencies.
Unlike TDMA "time division multiple access", a competing system
used in 2G GSM, all radios can be active all the time, because network
capacity does not directly limit the number of active radios.
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16. CDMA (Contd.)
Since larger numbers of phones can be served by smaller numbers of
cell-sites, CDMA-based standards have a significant economic
advantage over TDMA-based standards that used frequency-division
multiplexing.
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17. GSM
GSM (Global System for Mobile communications: originally
from Groupe Spécial Mobile) is the most popular standard
for mobile phones in the world.
Its promoter, the GSM Association, estimates that 80% of the global
mobile market uses the standard. GSM is used by over 3 billion people
across more than 212 countries and territories.
GSM differs from its predecessors in that both signaling and speech
channels are digital, and thus is considered a second generation (2G)
mobile phone system.
This has also meant that data communication was easy to build into
the system. GSM EDGE is a 3G version of the protocol.
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18. FUTURE SCOPE
Next Generation Mobile Networks (NGMN) Ltd. - Consortium with
partnership of major mobile operators
Recommendations without specific technology prescriptions
Target to establish performance targets, recommendations and
deployment scenarios for future wide-area mobile broadband
network packet switched core.
The architecture intended to provide a smooth migration of existing
2G/3G networks towards an IP network that is cost competitive and
has broadband performance.
Multi-hopping Networks.
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