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Cellular
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1
Cellular Networks
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0
200
400
600
800
1000
1200
1996 1997 1998 1999 2000 2001 2002 year
Su
bsc
rib
ers
[mill
ion
] GSM total
TDMA total
CDMA total
PDC total
Analogue total
Total wireless
Prediction (1998)
Mobile phone subscribers worldwide
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The MSC (mobile switching center) plays a central role in GSM
switching functionsadditional functions for mobility supportmanagement of network resourcesinterworking functions via Gateway MSC (GMSC)integration of several databases
Functions of a MSCspecific functions for paging and call forwardingtermination of signaling mobility specific signalinglocation registration and forwarding of location informationprovision of new services (fax, data calls)support of short message service (SMS)generation and forwarding of accounting and billing information
Mobile Services Switching Center
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Implements space division multiplex: base station covers a certain transmission area (cell)Mobile stations communicate only via the base stationAdvantages of cell structures:
higher capacity, higher number of usersless transmission power neededmore robust, decentralizedbase station deals with interference, transmission area etc. locally
Problems:fixed network needed for the base stationshandover (changing from one cell to another) necessaryinterference with other cells
Cell sizes from some 100 m in cities to, e.g., 35 km on the country side (GSM) - even less for higher frequencies
Cell structure
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Frequency reuse patterns
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1G 2G 3G2.5G
IS-95cdmaOne
IS-136TDMAD-AMPS
GSM
PDC
GPRS
IMT-DSUTRA FDD / W-CDMA
EDGE
IMT-TCUTRA TDD / TD-CDMA
cdma2000 1X
1X EV-DV(3X)
AMPSNMT
IMT-SCIS-136HSUWC-136
IMT-TCTD-SCDMA
CT0/1
CT2IMT-FTDECT
CD
MA
TD
MA
FD
MA
IMT-MCcdma2000 1X EV-DO
Source: Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02
Development of mobile telecommunication systems
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AMPS is an analog cellular phone system using FDMA.
NoteNote::
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Figure 17.5 Second-generation cellular phone systems
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D-AMPS, or IS-136, is a digital cellular phone system using TDMA
and FDMA.
NoteNote::
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GSMformerly: Groupe Spéciale Mobile (founded 1982)now: Global System for Mobile CommunicationPan-European standard (ETSI, European Telecommunications Standardisation Institute)simultaneous introduction of essential services in three phases (1991, 1994, 1996) by the European telecommunication administrations (Germany: D1 and D2) seamless roaming within Europe possibletoday many providers all over the world use GSM (more than 184 countries in Asia, Africa, Europe, Australia, America)more than 747 million subscribersmore than 70% of all digital mobile phones use GSMover 10 billion SMS per month in Germany, > 360 billion/year worldwide
GSM: Overview
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GSM bands
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Communication mobile, wireless communication; support for voice and data services
Total mobility international access, chip-card enables use of access points of different providers
Worldwide connectivityone number, the network handles localization
High capacity better frequency efficiency, smaller cells, more customers per cell
High transmission qualityhigh audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains)
Security functions access control, authentication via chip-card and PIN
Performance characteristics of GSM
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There is no perfect system!!no end-to-end encryption of user datareduced concentration while drivingelectromagnetic radiationabuse of private data possiblehigh complexity of the systemseveral incompatibilities within the GSM standards
Performance characteristics of GSM
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GSM is a digital cellular phone system using TDMA and FDMA.
NoteNote::
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IS-95 is a digital cellular phone system using CDMA/DSSS and FDMA.
NoteNote::
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The main goal of third-generation cellular telephony is to provide
universal personal communication.
NoteNote::
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IMT-2000 radio interfaces
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Satellite Networks
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Satellite categories
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Satellite orbit altitudes
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Table 17.1 Satellite frequency bandTable 17.1 Satellite frequency band
Band Downlink,
GHzUplink, GHz
Bandwidth, MHz
L 1.5 1.6 15
S 1.9 2.2 70
C 4 6 500
Ku 11 14 500
Ka 20 30 3500
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Satellites in geosynchronous orbit
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Triangulation
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GPS
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LEO satellite system
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Iridium constellation
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The Iridium system has 66 satellites in six LEO orbits, each at an
altitude of 750 km.
NoteNote::
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Iridium is designed to provide direct worldwide voice and data
communication using handheld terminals, a service similar to cellular
telephony but on a global scale.
NoteNote::
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Teledesic
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Teledesic has 288 satellites in 12 LEO orbits, each at an altitude of 1350 km.
NoteNote::
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