Cellular

1

Cellular Networks

2

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

3

4

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

5

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

6

Frequency reuse patterns

7

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

8

AMPS is an analog cellular phone system using FDMA.

NoteNote::

9

Figure 17.5 Second-generation cellular phone systems

10

D-AMPS, or IS-136, is a digital cellular phone system using TDMA

and FDMA.

NoteNote::

11

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

12

GSM bands

13

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

14

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

15

GSM is a digital cellular phone system using TDMA and FDMA.

NoteNote::

16

IS-95 is a digital cellular phone system using CDMA/DSSS and FDMA.

NoteNote::

17

The main goal of third-generation cellular telephony is to provide

universal personal communication.

NoteNote::

18

IMT-2000 radio interfaces

19

Satellite Networks

20

Satellite categories

21

Satellite orbit altitudes

22

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

23

Satellites in geosynchronous orbit

24

Triangulation

25

GPS

26

LEO satellite system

27

Iridium constellation

28

The Iridium system has 66 satellites in six LEO orbits, each at an

altitude of 750 km.

NoteNote::

29

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::

30

Teledesic

31

Teledesic has 288 satellites in 12 LEO orbits, each at an altitude of 1350 km.

NoteNote::