GSM system engineering artech

GSM
SYSTEM
ENGINEERING
The Artech House Mobile Communications Series
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GSM
SYSTEM
ENGINEERING
Asha Mehrotra
Artech House, Inc.
Boston
London
Library of Congress Cataloging-in-Publication Data
Mehrotra,
Asha.
GSM System Engineering
1
Asha Mehrotra.
p. cm.
Includes bibliographical references and index.
ISBN 0-89006-860-7 (alk. paper)
1
.Global system for mobile communications.
I.
Title.
TK5103.483.M45 1996
621.3845'64~21
97-4029
CIP
British Library Cataloguing in Publication Data
Mehrotra,
Asha

GSM System Engineering
1.
Cellular radio 2. Mobile communication systems.
I. Title
621.3'8456
ISBN 0-89006-860-7
Cover design by Jennifer Makower.
8
1997 ARTECH HOUSE, INC.
685
Canton Street
Norwood,
MA
02062
All rights reserved. Printed and bound in the United States of America. No part of this book
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tion. Use of a term in this book should not be regarded as affecting the validity of any trade-
mark or service mark.
International Standard Book Number: 0-89006-860-7
Library of Congress Catalog Card Number: 97-4029
Preface
Chapter
1
Introduction to GSM System
1.1
Introduction

1.1.1 Objectives of FPLMTS
1.2 GSM Background
1.2.1 Important Dates
1.2.2 MOU and Different Working Groups
1.3 GSM Operational Requirements
1.4 GSM Technical Requirements
1.5 GSM-Provided Services
1.6 Future Developments
1.7 Organization of the Book
Problems
References
Appendix
1A Teleservices
Appendix
1B
Bearer Services
Appendix
1C Supplementary Services
Chapter 2 GSM Architecture
2.1 Introduction
viii
GSM SYSTEM
ENGINEERING
GSM Network Structure
2.2.1
Cell Layout and Frequency Planning
Mobile Station
2.3.1 Functions of
MS
2.3.2 Power Levels

2.3.3 MS Configuration
2.3.4 SIM Card
2.3.5 Mobile Identification Numbers
Base Station System
2.4.1 Functions of BTS
2.4.2 BSC
Switching Subsystems: Mobile Switching Center and
Gateway Switching Center
2.5.1 Functions of MSC
2.5.2 VLR
Home Location Register
Authentication Center
Equipment Identity Register
Interworking Function
2.10 Echo Canceler
2.1
1
Operations and Maintenance Center
2.12 The Network Management Center
2.13 Billing Center
2.14 Networking
2.15 Conclusions
Problems
References
Chapter 3
Time and Frequency Axis Representation
3.1 Introduction
3.2 Time Domain Representation
3.2.1 Logical Channels
3.2.2 Logical

TCHs
3.2.3 Logical Control Channels
3.2.4
Structure of a TDMA Slot With a Frame
3.2.5
Time Organization of Signaling Channels
3.3 Frequency Axis Representation
3.3.1 Frequency Hopping
3.4 Operational Concepts
3.4.1 Mobile Modes
3.4.2 Access Support to Mobile
3.4.3 Mobile Sequence of Operations
Contents
fx
3.5 Conclusions
Problems
References
Chapter 4 Mobility Management
4.1 Introduction
4.2 Signaling Protocols
4.3 Mobile Initialization
4.4
Basic Steps in the Formation of a
Call
4.4.1 Connection Request
4.4.2 Paging Procedure
4.4.3 Identification Procedure
4.4.4 Authentication
4.4.5 Ciphering
4.4.6 Call Clearing

4.4.7 IMSI Attach and Detach
4.5 Location Update
4.6 MS-PSTN Call
4.7 PSTN-MS Call
4.8 MS-MS Call
4.9
Call Handover
4.10 Summary and Conclusions
Problems
References
Chapter 5 Security Management
5.1 Introduction
5.2 Temporary Mobile Subscriber Identification
5.3 Authentication
5.4 Encryption
5.5 Characteristics of the SIM
5.6 Equipment Identification
5.7 Conclusions
Problems
References
Chapter 6
Technical Details of GSM
6.1 Introduction
6.2 Spectral Efficiency of GSM System
6.2.1
Some Alternate Measure of Spectral Efficiency
6.2.2
Multiple Access Efficiency of FDMA and TDMA
Systems
6.2.3 FDMA

6.2.4 TDMA
x
GSM SYSTEM ENGINEERING
6.3
Speech Coding
6.3.1
The RPE-LTP Speech Encoder
6.4
Block and Convolutional Coding
6.4.1
Full Rate Speech Coding
6.4.2
Data Coding at
9.6
Kbps and
2.4
Kbps
6.4.3
Channel Rate of
2.4
Kbps
6.4.4
Control Channel Signaling Data
6.4.5
Interleaving
6.5
Digital Modulation
6.5.1
MSK Modulation
6.5.2

GMSK Modulation
6.5.3
Demodulation
6.6
Channel Characterization
6.6.1
Channel Equalization
6.7
Delay Requirements
6.8
Discontinuous Transmission
6.8.1
Voice Activity Detector
6.8.2
The Comfort Noise Functions
6.9
Timing Advance Mechanism
6.10
Mobile-Assisted Handover
6.10.1
GSM Application
6.11
Conclusions
Problems
References
Chapter
7
Subscriber Management and Network Maintenance
7.1
Introduction

7.2
Subscription Administration
7.3
Billing and Accounting
7.3.1
GSM and Subscriber Mobility
7.3.2
Subscriber Billing: National and International
7.3.3
Charging Principles
7.3.4
Billing and Accounting: Different Call Components
7.3.5
Standard for Data Transfer
7.3.6
Toll Ticketing
7.4
Network Maintenance
7.4.1
Minimization of Failure Occurrence
7.4.2
Minimizing the Effects of Failure
7.4.3
Fault Detection
7.5
Conclusions
Problems
References
Contents
xi

Chapter
8
GSM Protocols
Introduction
Physical Layer
Data Link Layer
MTP3, SCCP, and TCAP Protocols
Application Layer
8.5.1
RRLayer
8.5.2
MM Layer
8.5.3
CCLayer
8.5.4
Message Formatting
BSS Application Part
MAP Protocol
8.7.1
MAP Protocols for MM
8.7.2
MAP Protocols for Basic Services Support
Common Channel Signaling Between MSC and Fixed
Network
Standardized Interfaces in GSM
8.9.1
U,
Interface
8.9.2
A-bis Interface

8.9.3
A Interface
8.10
Conclusions
Problems
References
Chapter
9
Details of MS, BSS, MSC, and NMC
9.1
Introduction
9.2
Mobile Station Subsystem
9.2.1
Mobile Attributes
9.2.2
Features of Mobile: Basic, Supplementary, and
Additional
9.2.3
Mobile Configuration
9.2.4
Terminal Architecture
9.3
Base Station System
9.3.1
BS Controller Architecture
9.3.2
BTS Architecture
9.3.3
Remote Transcoders

9.4
MSC and GMSC Architecture
9.4.1
Switch Matrix
9.4.2
Automatic Message Accounting
9.4.3
Timing System
9.4.4 X.25
Interface System
9.4.5
Land Call Management
xii
GSM SYSTEM ENGINEERING
9.4.6 Mobile Call Management
9.4.7 Mobility Management
9.4.8 Service Management Subsystem
9.4.9 VLR Subsystem
9.4.10 Interface to Authentication Center
9.5 Network Management System
9.5.1 Functions of NMC
9.5.2 Functions of OMC
9.5.3 Architecture of OMC
9.6 Conclusions
Problems
References
Chapter 10 Microcellular Systems 343
10.1 Introduction 343
10.2
First-, Second-, and Third-Generation Systems, Technology,

and Future Trend 344
10.3 Technical Requirements
of
Microcellular Systems 347
10.3.1 Channel Segregation 347
10.3.2 Multiple
BSs Registration 348
10.3.3 Diversity Transmission 348
10.3.4 Modulation 349
10.3.5 Performance Criterion 350
10.3.6 Propagation Model 351
10.3.7 Multipath Model 353
10.4 Cordless Telephones 353
10.4.1 Cordless Telephones
(CT2-CAI)
354
10.4.2 DECT 359
10.5 European DCS 1800 System 367
10.5.1 The Frequency Band of Operation and Channel
Arrangement 368
10.5.2 Mobile and BS Power Requirements 368
10.5.3 RF Modulation Spectrum 368
10.5.4 Power Ramping 368
10.6 Conclusions 3 70
Problems 3 70
References 3 72
Chapter 11
Future of PCS Systems
11.1
Introduction

11.2 PCS Systems of the Future
11.2.1 European Role
11.2.2 Key Objectives of UMTSJFPLMTS
Contents
xiii
11.2.3 Solution Aproach for Future Systems
11.2.4 Role of Different Players
11.3 U.S. Effort for Universal Personal Communication Services
11.3.1 Spectrum for PCS Services
11.3.2 Trading Areas
11.3.3 Narrowband Licenses
11.3.4 Wideband PCS
11.3.5 Unlicensed PCS Services
11.3.6 Pioneer's Preference
11.4 Satellite Mobile Communication
11.4.1 Potential Markets
11.4.2 Iridium
1
1.4.3 Odyssey
11.4.4 Globalstar
11.4.5 Inmarsat-P
11.5 Conclusions
Problems
References
Glossary
About the Author
Index
Cellular communications is one of the fastest growing and most challenging telecom-
munication applications ever. Today, it represents a large and continuously increasing

percentage of all new telephone subscribers around the world. In the long term,
cellular digital technology may become the universal way of communication.
The mobile communications market has experienced rapid growth in European
Post Offices and Telecommunication (CEPT) Europe. This has been driven by market
forces, technological development, and new forms of cooperation in the areas of
standardization and implementation of new systems.
A
major product of this stan-
dards work within CEPT Europe has been the GSM standard. The Global System
for Mobile Communication was developed as the next generation digital cellular
mobile communication system for CEPT Europe.
The European cellular market was, up to the
1980s, characterized by a large
number of incompatible analog systems (TACS, NMT, etc.). This created a situation
where service generally was limited to national territories and where the economy
of scale was largely lost. This situation has made it clear that for the future a common
system is required for the widespread use of mobile telephones all over Europe.
GSM is the Pan-European digital mobile telephony standard specified by European
Telecommunication Standards Institute (ETSI) and provides a common standard.
This means that cellular subscribers can use their mobile telephones all over Europe.
The essential elements of GSM system consist of the following: Mobile users,
Base Station System, Mobile Switching Center, and the Public Voice and Data
xui
GSM SYSTEM ENGINEERING
networks. Some other important elements of the system include the Operations and
Management Center, the Billing Center, and the various networks (SS7 and
X.25)
interconnecting these subsystems. Therefore, we arrange the discussion based on
different aspects of the subsystem as follows.
Chapter

2
deals with the architecture of the GSM system. We discuss the
functional requirements of Mobile Station; Base Station System, which includes Base
Transceiver and Base Station Controller; Mobile Switching Center and its variation
known as Gateway Switching Center; Operations and Network Management Cen-
ters; and Billing Center. Chapter
3
provides a detailed discussion of time and fre-
quency axis representation of the system. We discuss the functions and characteristics
of physical and logical channels and provide the reasons for the flexibility of GSM
system. Chapter
4
is fully devoted to the mobility management issues and provides
the timing diagrams for different types of calls, including incoming call to mobile,
mobile origination of a call, and mobile-to-mobile call. Chapter 5 brings out various
security aspects. In Chapter
6
we discuss technical characteristics of the system which
include all the important aspects of speech coding, modulation, and error encoding
applied to the GSM system. In Chapter
7
we discuss subscription management,
billing and accounting, and some important aspects of network
maintenance.Chapter
8
deals with GSM protocols based on the IS0 and SS7 standards. Chapter
9
elaborates
on Chapters
2

and
3
and discusses subsystem configuration and architecture of
MSC, BSS, and OCC, and MS. Chapter
10
provides existing systems as predecessors
to PCS systems. Chapter
11
points out the potential shortfalls of existing PCS systems
and provides some solutions in this direction.
I
believe the best way to prove that one has understood the contents of the
chapters is to answer pertinent questions. With this in mind, review questions are
arranged at the end of each chapter.
This book is mainly intended for engineers working in the area of cellular
communication, and in particular, with GSM, or closely related TDMA-based sys-
tems. The book can also be used as a special course for TDMA systems with examples
of GSM, as this is probably the most intricate mobile communication systems of
the world today. For practicing engineers, a BS degree in electrical engineering and
some working knowledge of mobile communications is assumed. For students taking
the specialized TDMA course, it is assumed that they have taken senior-level courses
in communication engineering.
I would like to thank my students at George Washington University during
the summer of 1995, and my graduate students during the summer of
1996
at
Virginia Tech at Washington Graduate Center, who have contributed by asking the
right questions and, in general, by improving the script. I also must thank the
reviewers of this book for their excellent comments, which have tremendously
improved the book.

Finally, a project of this type can never be completed without the continuous
support of one's family. In this regard, thanks are due to my wife, Nisha, my
Preface
xvit
daughters, Anuja, Sonia, Vinita, and my son Neil. Special thanks to my daughters
Anuja, who was mainly responsible for arranging the script before she got married,
and Sonia, who carried the responsibility until the book was completed.
Asha Mehrotra
March
1997
CHAPTER
1
vvv
INTRODUCTION
TO
GLOBAL
SYSTEM
FOR
MOBILE
COMMUNICATIONS
1.1
INTRODUCTION [I-51
Cellular telecommunications is one of the fastest growing and most challenging
telecommunication applications ever. Today, it represents a large and continuously
increasing percentage of all new telephone subscribers around the world. In the long
term, cellular digital technology may become the universal way of communication.
The mobile communications market has experienced rapid growth in
European
Post Offices and Telecommunication

(CEPT). This has been driven by market forces,
technological development, and new forms
of
cooperation in the areas of new systems
standardization and implementation.
A
major product of this standards work within
CEPT Europe has been the
Global System for Mobile Communication
(GSM) stan-
dard. The GSM was developed as the next-generation digital cellular mobile commu-
nication system for
CEPT
Europe. The standardization work for the first
implementation in 1991 was completed in early 1990. Network operators in
17
CEPT
countries signed the
memorandum of understanding
(MOU) and are committed to
introduce GSM systems by 1991.
2
GSM
SYSTEM
LNGINEERING
In
1987
a Group Special Mobile Conference under the auspices of CEPT took
place. The goal of this conference was to define a Pan-European standard for digital
cellular communications that would be implemented beginning in 1991. Thirteen

countries were involved in the
devel~pment of the initial recommendations. Since
that time,
GSM
development has been characterized by remarkable progress and
cooperation. Eighteen European nations decided to adopt the standard initially.
Currently
GSM
recommendations provide country "Color Codes" for
26
European
nations. Hong Kong and Australia have also adapted the GSM systems. In Europe
there are several large cellular systems in operation, such as Nordic Mobile Telephone
(NMT) in the Nordic countries and Total Access Communication System (TACS)
in the United Kingdom. Other countries in Western Europe also offer mobile services
as shown in Table
1.1.
Quality, capacity, and area of coverage vary widely, but
Table
1.1
Major Analog Systems in Europe
Date of
Country Systems Freq. Band Launch Operator
United Kingdom
Sweden
Norway
Finland
Denmark
France
Italy

Germany
Switzerland
The Netherlands
Austria
Spain
ETACS
NMT
NMT
NMT
MT
NMT
NMT
NMT
Radicom
2000
NMT
NMT
RTMS
ETACS
CNETZ
NMT
NMT
NMT
NMT
CNETZ
TACS
NMT
TACS
Cellnet
Vodafone

Comvik (Millicom)
Telia
Mobitel
Tele-Mobil
Teli-Mobile
Telecom Finland
Telecom Finland
Tele Denmark Mobil
A/S
Tele Denmark Mobil
AIS
France Telecom
Ligne SFR (SBC, Bell
South)
France Telecom
SIP
SIP
DETeMobil
DeTeMobile
PTT
Royal PIT
Royal PTT
PTV
PTV
Telefonica
Telefonica
Subs
x
1000
(Yr.

1991)
1521.4
1521.4
11.5
694.58
180.5
279.6
186.8
352.2
38.02
234.8
291
143.9
15.0
17.5
2191.9
733.891
Not Available
292.3
22.7
231.3
47.6
219.07
36.5
377.45
Introduction to Global
System
for Mobrle Commrrnlcations
3
demand in most cases has exceeded estimates almost in every country. Most systems

however, are national, which makes it impossible to use the mobile telephones
abroad. This situation has made it clear that for the future a common system is
required for the widespread use of mobile telephones all over Europe. GSM is the
Pan-European digital mobile telephony standard specified by the European Telecom-
munication Standards Institute (ETSI) and provides a common standard; thus, cellu-
lar subscribers can use their mobile telephones all over Europe. GSM growth from
199 1 to 1994 is shown in Figure
1.1.
Before the 1980s, the European cellular market was characterized by a large
number of incompatible analog standards (such as TACS and NMT), leading to a
situation where service generally was limited to national territories and where the
economy of scale was largely lost. At the same time, mobile communications
expanded very rapidly and the development showed clear signs of accelerated future
growth. These factors in combination were of course very unfortunate, and it was
realized, in view of the increasing mobility of the subscribers all over Europe and
their expectations of service being offered even in foreign countries, that unless a
remedy could be found, the result would be a very difficult situation in the 1990s.
In order to solve the problem, the European telecom authorities made the
following three decisions.
In 1982, two frequency bands, 890 MHz to 915
MHzand 935 MHz to 960 MHz,
were reserved primarily for use by cellular systems; and a next-generation European
cellular system for a newly allocated band of
2
MHz
x
25
MHz was formed.
In 1985, the decision was made to implement a digital system. The next step
was to choose between narrowband and

wideband solutions.
In 1987, GSM concluded that digital technology working in the Time Division
Multiple Access (TDMA) mode would provide the optimum solution for the future
system. The narrowband TDMA solution was chosen (less than 10 channels per
carrier frequency is generally regarded as a narrowband TDMA system),
in
consider-
1992 1993
Year
Figure
1.1
GSM
growth
in
Europe.
4
GSM SYSTEM ENGINEERING
ation of its several advantages. Specifically, a TDMA system has the following
advantages.
Offers a possibility of channel splitting and advanced speech coding in the
future, resulting in improved spectrum efficiency;
Offers much greater variety of service than the analog;
Has ISDN capability;
Is strongly favored by modern component development, which leads to lower
system cost;
Allows considerable improvements to be made with regards to the protection
of information in the system.
Developing such a common system would allow a subscriber to use his own set all
over Europe. From a user's point of view, the Pan-European system would appear
as one system, although, in fact, it would consist of many systems run by independent

operators. This standardization would be applied to certain key interfaces within
the fixed parts of the system to avoid development of a large number of proprietary
interfaces, resulting in loss of economy of scale. Hence, the system would be defined
in terms of functional building blocks and their interfaces. This initiative was taken
at the right time, with regard to the technology, the demand, and the need for
standardization. There was and still is a strong interaction between the developments
in the fields of telecommunications and politics, in Europe as elsewhere, that has
lead to a strong drive toward standardization in many fields. Standardization was
felt to be the necessity for the development of a single European market.
CCIR Study Group
8
realized in the middle of the last decade that different
Future Public Land Mobile Telecommunication Systems (FPLMTS) were presently
under study in different countries. It was obvious that
CCIR
had the task of coordinat-
ing the different developments and forming a list of recommendations. CCIR Study
Group
8
decided to establish a special team, that is, an
Interim
Working Party
(IWP), to study this important subject and determine the overall objectives of the
FPLMTS systems, which include the suitable choice of frequency band or bands and
defining the essential characteristics of the systems. The system should provide a
wide range of services, such as voice, data, and others including compatibility for
national and international roaming.
1.1.1
Objectives
of

FPLMTS
Some primary objectives for FPLMTS are as follows.
1.
To provide a framework for continuing the extension of mobile network
services and access to services and facilities of the fixed network
(public-
Introduction to
Global System
for
Mobile Commrttticatiot~s
5
switched telephone networks
/
integrated service digital networks
(PSTNI
ISDN)) subject to the constraints of radio transmission, spectrum usage, and
system economics;
2.
To allow mobile and fixed network users to use the services regardless of
location (that is, national and international roaming);
3.
To provide an open architecture that will permit the easy introduction of new
technology advancements as well as different applications;
4.
To allow the coexistence and interconnection with mobile systems that use
direct satellite links;
5.
To provide for unique user identification and PSTNASDN numbers in accor-
dance with appropriate
CCITT

Recommendations;
6.
To offer the services available in the PSTNASDN and other public networks,
as far as possible, bearing in mind the differences in the characteristics of the
fixed network and mobile radio environments;
7. To provide frequency commonality, which should allow for the desired level
of operational compatibility on the systems. In principle, a complete common-
ality
of
one frequency band on a worldwide basis would be desired, but
reasonable commonality could also be obtained through a common signaling
band and sufficient overlap of the traffic bands to ensure compatibility.
With these reasons for developing the GSM system, we will highlight the GSM
background, operational requirements, and technical requirements. Section 1.5 will
describe the different services offered by GSM, followed by the contents of the book
and conclusions.
1.2
GSM
BACKGROUND
The Joint West-European venture of specifying the GSM system started within the
CEPT Organization, where the cooperative work in the different areas of telecommu-
nications was formally adopted in the form of recommendations. However, it was
a national decision whether or not each recommendation, or set of recommendations,
for a given service should be implemented by the administration of each country.
There was a need, however, for a more demanding obligation as far as the
GSM was concerned. The system needed to include the concept of international
roaming, and success in one country would therefore depend upon the system roll-
out in other countries. The development and production of system equipment would
require large industrial investments that could hardly be justified unless the different
national markets evolved somewhat simultaneously.

A
memorandum of understand-
ing was thus prepared during mid-1987 and signed by the first
12
countries in
September 1987.
The GSM system specification work was later transferred to ETSI, an organiza-
tion controlling standardization and the MOU, which served as an adequate forum
6
GSM SYSTEM ENGINEERING
for discussions on pure operational matters. The main purpose of the GSM-MOU
was to provide a framework for all the necessary measures to be taken by the
signatories together to ensure the opening of a commercial service in their respective
countries by
1991. Also, the network operators would plan the progressive implemen-
tation of the networks in each country so that transport routes between the countries
of the signatories could be brought early into the coverage of the respective systems.
Priority for coverage would be given to all capital cities including the principal
airport by 1991, introduction of special services by 1993, and the full European
roaming market by 1995, as shown in Table 1.2.
1.2.1
Important Dates
Important dates in the development cycle of the GSM project are shown in Table
1.3. The project started in 1982 with the creation of the Group Special Mobile
within
CEPT.
The pivotal year was 1987, when digital system was adopted and
field trials were completed. The system was finally put into operation in 1991.
1.2.2
MOU and Different Working Groups

The GSM-MOU established several subgroups within GSM. The task of the individ-
ual groups was to organize the work in the following areas of concern, as shown
in Table 1.4.
1.3
GSM OPERATIONAL REQUIREMENTS
[6-101
A
list of operational requirements was developed that consisted of the following.
High audio quality and link integrity;
High spectral efficiency;
Identical system in all countries (European harmonization and standardization);
Table 1.2
Milestones for a GSM System
Year Occurrence
Mid-1991 Capitals;
Voice, emergency calls, call forwarding, and barring
Mid-1 993 Intercapitol roaming;
Short
message services
(SMS),
FAX,
and call holding
Mid-1995 European roaming;
Real-time information, call waiting, and conference calls
Introduction to Global System for Mobrle Communications
7
Table
1.3
Important Dates in the GSM Project
Occurrence

Group Special Mobile created within CEPT
FrancelGerman agreement at Nice to support GSM, thus triggering the process to resolve
European differences of opinion in favor of a unified Pan-European digital cellular service.
GSM establishes a permanent nucleus in Paris.
The Heads of State meeting in London in December requested agreement on standards and
commitment of operators. The European Council of Ministers issued a draft directive on
radio spectrum use.
Field trials were completed in Paris in February following a precedent-setting decision to
conduct a single set of field trials of spectrum efficiency, voice quality, and the radio interface
of all the proposed systems. All systems were tested under the same conditions.
At the Madrid GSM conference in February, it was agreed that the system would be digital,
narrowband TDMA access using voice coders.
The Ministerial meeting was held in Bonn on May
3.
The United Kingdom, Germany, France,
and Italy agreed at the Bonn conference on May
19
to standards,
1991
roll-out of the system,
and competition concentration of industry, and asked operators for a Memorandum of
Understanding.
At Copenhagen on September
7,
operators signed Memorandum of Understanding, agreeing
on procedures and schedules to procure, build, and test systems.
Tenders were issued by GSM member countries in March.
Prototype (validation) systems were on the air. GSM became an ETSI Technical Committee.
Pre-operational systems came on the air. DCS
1800

adaptation started.
The United Kingdom, France, Germany, and Italy introduced digital cellular service.
Motorola started the first commercial GSM system.
Conference was called in Finland to explore the GSM migration toward UMTSIFPLMT.
Phase
2
GSM specifications were frozen. Contracts were awarded in Asia, the Middle East,
and Europe for GSM systems. The new name "Global System for Mobile Communications"
was given to GSM.
Phase 2 implementation began.
Intersystem roaming (international roaming needs standardized air interface);
High degree of flexibility (open architecture that will allow new services to be
introduced at a future date);
Economy in both sparsely and heavily populated areas;
Integration with
ISDN;
Other security features;
A
range of additional features, such as short message service and use of facsimile
system;
Easy to introduce the system;
Low-cost infrastructure.
The specific requirements for the system were not clearly defined by the superior
committees in CEPT. On the contrary, a great deal of freedom was given to
GSM
8
GSM SYSTEM t.NGINEER!NG
Table 1.4
Main Areas of Concern of Different Working Groups
Working

Group
Areas of Concern
MOU-BARG
(Billing and Accounting)
MOU-MP
(Marketing Planning)
MOU-P
All commercial and administration principles and procedures to sup-
port European roaming including:
(I) Administration of subscribers,
(2) Billing harmonization, (3) Credit control, (4) Fraud prevention
intersystem, (5) Accounting operation,
(6)
Statistics, and
(7)
Definitions
of harmonized billing and accounting software requirements.
(1) Presentation of coverage information, (2) Identification of selling
features to guide system development,
(3)
Coordination of awareness
campaign public relations, and (4) GSM name and logo.
Harmonization of procurement policy.
(Procurement)
MOU-EREG
(European Roaming)
MOU-CONIG
(Conformancc of Nctwork
Interfaces)
MOU-TAP

(Type Approval
Administrative
Procedures)
MOU-TADIG
(Transfer Account Data
Interchange)
MOU-SERG
(Services)
MOU-SG
(Security)
MOU-RIC
(Radio Interface
Coordination)
Coordination of all technical and operational procedures principles
and plans for the support of European roaming, including:
(1) Mobile
numbering plans; (2) Routing of mobile terminated calls and of signal-
ing messages; (3) Technical implications of tariff principles on interna-
tional interworking;
(4) Establishment of international signaling links;
and (5) Interworking between PLMN utilizing different work func-
tions, quality and availability of service.
(1) Listtdefinition of tests for conformance of interfaces "A" and
"Abis" and (2) harmonization of test activities.
(1) Harmonization of procedures regarding type approval,
(2)
Review
of existing or emerging directives and identification of possible diffi-
culties, and
(3) Control and issue of IMEIs.

(1) To specify the detailed file: Interchange mechanism to tape and
data transfer between
billing entities to facilitate the transfer account
"
procedures as defined by relevant GSM recommendations, taking into
account the necessary security and quality of service requirements; (2)
To specify the format of data records to be exchanged either by tape
or data transfer; and
(3)
To
specify standard sets of protocols for such
data transfer
(1)
Maintenance of GSM recommendations following transfer of
responsibilities from
ETSItGSM, (2) Allocation/revision of status of
implementation categories of services and dates for introduction, and
(3) Review of compatibility of services for roaming.
(1) Administration of nondisclosure undertaking for algorithms, (2)
Maintenance of algorithms and test sequences, (3) Monitoring of ade-
quacy of system security and proposals for enhancements as required.
(1)
Coordination of technical aspects of type approval and identifica-
tion of problems affecting type approval as a result of validation and
conflicting interpretations of recommendations, (2) Resolution of tech-
nical problems with regard to type approval in different countries, and
(3) Review of the System Simulator activities.