GSM Technology for engineers

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Be familiar with the development of 2G mobile systems. Describe the architecture of a GSM network. Appreciate the main services provided within a GSM network. Understand the various facets of the GSM air interface including, access structures, frequency allocations, physical and logical channels.

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 Copyright 2002 AIRCOM International Ltd All rights reserved AIRCOM Training is committed to providing our customers with quality instructor led Telecommunications Training. This documentation is protected by copyright. No part of the contents of this documentation may be reproduced in any form, or by any means, without the prior written consent of AIRCOM International. Document Number: P/TR/003/K011/4.4 This manual prepared by: AIRCOM International Grosvenor House 65-71 London Road Redhill, Surrey RH1 1LQ ENGLAND Telephone: +44 (0) 1737 775700 Support Hotline: +44 (0) 1737 775777 Fax: +44 (0) 1737 775770 Web: http://www.aircom.co.uk GSM TECHNOLOGY FOR ENGINEERS
Table of Contents 1. Introduction to Cellular Systems 1.1 Introduction ...........................................................................................................1 1.2 Cellular Radio ........................................................................................................2 st 1.3 1 Generation Cellular Systems..............................................................................3 nd 1.4 2 Generation Cellular Systems .............................................................................5 1.5 GSM Development and Characteristics...................................................................7 1.6 Cellular Systems Subscriber Distribution .................................................................8 1.7 2.5G Characteristics ..............................................................................................9 2. Architecture Overview 2.1 Introduction ......................................................................................................... 11 2.2 GSM Identifiers .................................................................................................... 12 2.3 General Architecture Overview ............................................................................. 13 2.4 The GSM Mobile Station (MS).............................................................................. 14 2.5 The Base Station Subsystem (BSS). ..................................................................... 16 2.6 The Network Switching Subsystem (NSS) ............................................................. 17 2.7 GSM Interfaces.................................................................................................... 22 Self-Assessment Exerecises ................................................................................ 27 3. GSM Services 3.1 Introduction ........................................................................................................ 29 3.2 GSM Bearer Services........................................................................................... 30 3.3 Teleservices ........................................................................................................ 32 3.4 Supplementary Services....................................................................................... 33 3.5 Circuit-Switched Data (CSD) Services ................................................................... 34 3.6 Short Message Service ....................................................................................... 35 3.7 USSD Data Services ............................................................................................ 37 Self-Assessment Exerecises ................................................................................ 41 4. The Air Interface 4.1 Introduction ......................................................................................................... 43 4.2 GSM Frequency Spectrum Allocation .................................................................... 44 4.3 GSM Multiple Access Techniques ......................................................................... 50 4.4 GSM Air Interface Channels ................................................................................. 52 4.5 Frames and Multiframes ....................................................................................... 56 Self-Assessment Exercises .................................................................................. 63 5. Protocols 5.1 Introduction ......................................................................................................... 65 5.2 The ISO 7-Layer OSI Model ................................................................................. 66 5.3 GSM Protocols Overview ..................................................................................... 67 5.4 GSM Transmission Protocols................................................................................ 69 5.5 GSM Signalling Protocols ..................................................................................... 71 5.6 GSM Air (Um) Interface Protocols ......................................................................... 73 5.7 GSM A-bis Interface Protocols .............................................................................. 75 5.8 The GSM A Interface Protocols............................................................................. 78 6. Speech and Channel Coding 6.1 Introduction ......................................................................................................... 79 6.2 Speech Coding Techniques .................................................................................. 80 6.3 GSM Speech Coding .......................................................................................... 81 6.4 Channel Coding Techniques ................................................................................. 83 6.5 GSM Channel Coding. ......................................................................................... 88 6.6 Interleaving.......................................................................................................... 89 6.7 Radio Burst Multiplexing…… .............. ………………………………………………..91 6.8 Summary of Coding Processes ………… ……………………………………………95 6.9 Radio Interface Modulation….. …………… ……………………………………………95 GSM Technology for Engineers © AIRCOM International 2002 i
7. Mobility Management 7.1 Introduction ......................................................................................................... 99 7.2 Mobility Management Procedures ....................................................................... 100 7.3 Network Areas ................................................................................................... 101 7.4 Mobility States ................................................................................................... 103 7.5 IMSI Attach/Detach............................................................................................ 104 7.6 Location Updating .............................................................................................. 107 7.7 Roaming ........................................................................................................... 109 7.8 TMSI Reallocation ............................................................................................. 110 8. Radio Resource Management 8.1 Introduction ....................................................................................................... 113 8.2 Radio Resource Connection Setup ..................................................................... 114 8.3 Cell Selection and Reselection ........................................................................... 115 8.4 Handovers......................................................................................................... 118 9. Call Management 9.1 Introduction ....................................................................................................... 123 9.2 Mobile Originated Calls ...................................................................................... 124 9.3 Mobile Terminated Calls..................................................................................... 125 9.4 Call Routing Examples ....................................................................................... 127 9.5 Echo Cancelling................................................................................................. 129 Self-Assessment Exercises ................................................................................ 131 10. GSM Security 10.1 Introduction ..................................................................................................... 133 10.2 Purposes of GSM Security................................................................................ 134 10.3 User Identity Confidentiality .............................................................................. 134 10.4 Authentication.................................................................................................. 135 10.5 User Data Confidentiality - Encryption ............................................................... 138 10.6 Signalling Data Confidentiality........................................................................... 140 Self-Assessment Exercises .............................................................................. 143 11. Billing Procedures Overview 11.1 Introduction ..................................................................................................... 145 11.2 Billing Principles............................................................................................... 146 11.3 Description of Call Components ........................................................................ 146 11.4 Charge Advice Information (CAI)....................................................................... 148 11.5 Advice of Charge (AoC) Calculations................................................................. 149 11.6 Call Detail Records .......................................................................................... 151 11.7 The Transferred Account Procedure (TAP) ........................................................ 152 12. GSM Evolution 12.1 Introduction ..................................................................................................... 155 12.2 High Speed Circuit Switched Data (HSCSD) ...................................................... 156 12.3 General Packet Radio Service (GPRS).............................................................. 157 12.4 Enhanced Data for nGSM Evolution (EDGE) ..................................................... 159 Appendix A - Solutions to Self Assessment Exercises Appendix B - Glossary of Terms GSM Technology for Engineers ii © AIRCOM International 2002
Course Objectives and Structure Course Objectives • Be familiar with the development of 2G mobile systems • Describe the architecture of a GSM network • Appreciate the main services provided within a GSM network • Understand the various facets of the GSM air interface including, Access structures, frequency allocations, physical and logical channels • Appreciate GSM transmission and signalling protocols • Describe the methods of speech and error coding on the air interface • Understand the principals mobility management • Understand the principles of radio resource management • Describe the processes involved in connection management • Appreciate the security measures implemented by GSM • Understand GSM mechanisms for customer billing • Be familiar with the future evolution of GSM including 2G+ technologies • Describe the evolution of GSM towards 3G systems Course Outline Day 1 Day 2 1. Introduction to Cellular Systems 7. Radio Resource Management 2. Architecture Overview 8. Mobility Management 3. Services 9. Connection Management 4. The Air Interface 10. Security 5. GSM Protocols 11. Billing Procedures Overview 6. Speech and Channel Coding 12. GSM Evolution GSM Technology for Engineers © AIRCOM International 2002 iii
Intentional Blank Page GSM Technology for Engineers iv © AIRCOM International 2002
1. Introduction to Cellular Systems 1. Introduction to Cellular Systems _________________________________________________________________________________ 1.1 Introduction This section reviews the characteristics of first and second generation cellular systems and is followed by an overview of the functional blocks of GSM architecture, and its functional entities. Topics covered include: • Cellular Radio • 1 st generation cellular characteristics and systems • 2 nd generation cellular characteristics and non-GSM systems • GSM development and characteristics • Worldwide roll-out of cellular systems and subscriber distribution GSM Technology for Engineers © AIRCOM International 2002 1
1. Introduction to Cellular Systems _________________________________________________________________________________ 1.2 Cellular Radio Mobile Radio Networks Cellular • There are three major types of terrestrial mobile communications technologies: • Paging: Brief numeric, alphanumeric or voice messages PSTN are sent to the subscriber typically using simultaneous broadcasting. MSC • Cordless Communication: Users are provided limited mobility from a dedicated base station Cordless Paging Control Centre • Cellular: Users are provided wide area mobility from multiple base stations with handover permitted Paging Area Paging Area Cellular Radio Network Characteristics • Mobile Radio Network based on cellular structure for areas coverage • Frequency reuse required due to limited frequency availability (frequency re-use patterns) • Mobility between cell areas possible (handover) GSM Technology for Engineers 2 © AIRCOM International 2002
1. Introduction to Cellular Systems Cellular Generations The significant stages in the evolution of Data rate cellular radio systems is referred to in terms of generations: • 1st Generation or 1G • 2nd Generation or 2G • 2.5G • 3rd Generation or 3G • 4th Generation or 4G 1978 1992 2000 2002 ? time Progress of data rates with time and generation _________________________________________________________________________________ 1.3 1st Generation Cellular Systems 1st Generation Cellular Characteristics • Widespread Introduction in early 1980s • Analogue modulation • Frequency Division Multiple Access • Voice traffic only The 1st Generation of Cellular • No inter-network roaming possible Technology makes use of analogue modulation techniques such as FM • Insecure air interface GSM Technology for Engineers © AIRCOM International 2002 3
1. Introduction to Cellular Systems In early networks, the emphasis was to provide radio coverage with little consideration for the number of calls to be carried. As the subscriber base grew, the need to provide greater traffic capacity had to be addressed. 1st Generation Standards • AMPS (Analogue Advanced Mobile Phone System) • North American Standard in cellular band (800MHz) • TACS (Total Access Communications System) • UK originated Standard based on AMPS in 900MHz band • NMT (Nordic Mobile Telephony System) • Scandinavian Standard in 450MHz and 900MHz bands • C-450 • German Standard in 450MHz band Analogue/AMPS • JTACS (Japanese Total Access Communications System) Nokia 252 • Japanese Standard in 900MHz band 1st Generation Planning • Macrocellular • High sites for coverage driven planning • Antennas above roof height • Frequency planning required F1 • For networks with more cells than frequencies these must be planned F2 F5 • Large cell size • Order 30km F4 • Hard handover F3 • Mobile only ever connected to a single cell • Hexagonal Grid Representation The above diagram shows how different frequencies are used in different cells in a cellular network GSM Technology for Engineers 4 © AIRCOM International 2002
1. Introduction to Cellular Systems The First Generation 1.4 2nd Generation Cellular Systems Digital systems offer considerable advantages in terms of capacity and security and introduce new possibilities for data traffic. 2nd Generation Characteristics • Widespread Introduction in 1990’s • Uses digital modulation • Variety of multiple access strategies • More efficient use of radio spectrum 1 000 100111 • Voice and low rate circuit switched data 00 01 10 • International roaming capability 1 1111 00 001 01 0 00000010 0010 101 1 1 0010 0 • Secure air interface 0 0 1111 1110 • Compatibility with ISDN 0 GSM Technology for Engineers © AIRCOM International 2002 5
1. Introduction to Cellular Systems While first generation systems used a cellular structure and frequency re-use patterns, digital systems developed this concept to include multi-layer cellular patterns (microcells and macrocells). The greater immunity to interference inherent in digital transmission allowed tighter frequency re-use patterns to be implemented. cdmaOne Characteristics • First networks in 1996 • Derived from Qualcomm IS-95 air interface • Largely American subscriber base with some Asian networks • Code Division Multiple Access • The closest 2nd generation standard to many of the 3rd generation standards • ANSI-41 core network • Chip rate of 1.2288Mcps cdmaOne phones D-AMPS/PDC Characteristics • TDMA (D-AMPS) • PDC • North American TDMA/FDMA based • Japanese TDMA/FDMA based standard based upon AMPS standard • Predominantly used in North and • Predominantly used in Asia South America • Planning Similar to GSM • ANSI-41 Core Network • Planning Similar to GSM TDMA and PDC phones GSM Technology for Engineers 6 © AIRCOM International 2002
1. Introduction to Cellular Systems 1.5 GSM Development and Characteristics Originally GSM referred to the European working party set up to establish a new standard (‘Groupe Speciale Mobile’) but was later amended to reflect a more global application (Global System for Mobile communications). Cellular Structure • The aim of a cellular system is to make best use of the available frequencies (spectrum) • The cellular structure allows the re-use of frequencies across the network • Planning the pattern of this frequency re-use is a key part of the system design • Hexagonal pattern best represents interlocking grid of cells GSM Planning GSM Planning • Key Network planning parameters • Coverage – getting a usable radio signal to all areas in the network • Capacity – handling the call traffic generated by the subscribers F1 • Quality – low interference, few calls dropped etc. F2 • Optional parameters requiring planning F5 • Hierarchical Cell Structures (macrocell/microcell) F4 • Frequency Hopping F3 • Discontinuous Transmission • Power Control • Subscriber/traffic analysis Cellular networks can use microcells to • Capacity limited by number of TRX’s provide additional capacity GSM Technology for Engineers © AIRCOM International 2002 7
1. Introduction to Cellular Systems 1.6 Cellular Systems Subscriber Distribution Worldwide Mobile Communications Systems Subscribers (x million) Second Generation - DAMPS 700 600 Second Generation - PDC 500 400 Second Generation - GSM 300 200 Second Generation - cdmaOne 100 0 01 First Generation - Analogue 91 93 95 97 99 20 19 19 19 19 19 Source:Wideband CDMA for 3rd Generation Mobile Communications, Artech House, 1998 Worldwide Mobile Subscriber Distribution Subscribers (x million) 2000 European Union Countries 1500 North America 1000 Asia Pacific 500 Rest of World 0 1995 2000 2005 2010 Source: Third Generation Mobile Communications Artech House, 2000 GSM Technology for Engineers 8 © AIRCOM International 2002
1. Introduction to Cellular Systems 1.7 2.5G Characteristics 2.5G Characteristics • Available now... • Digital modulation • Voice and intermediate rate circuit/packet switched data • 2G technology roaming • Secure air interface • Based upon existing dominant 2G standards such as GSM and cdmaOne • Enhanced data rates GSM Technology for Engineers © AIRCOM International 2002 9
1. Introduction to Cellular Systems Summary This Section has covered: • Cellular Radio in context with other wireless systems • Cellular Radio Characteristics • 1st Generation Cellular Systems • 2nd Generation Cellular Systems • GSM-specific Characteristics • Cellular User Distribution • 2.5 G Characteristics GSM Technology for Engineers 10 © AIRCOM International 2002
2. Architecture Overview 2. Architecture Overview _________________________________________________________________________________ 2.1 Introduction This section of the course provides an overview of the GSM network architecture. This includes a brief explanation of the different network subsystems and a description of the functionality of the elements within each of the se subsystems. Topics include: • A General architecture overview • The Mobile Station (MS) Subsystem and Elements • The Base Station Subsystem (BSS) and Elements • The Network Subsystem (NSS) and Elements • Introduction to network interfaces GSM Technology for Engineers © AIRCOM International 2002 11
2. Architecture Overview ________________________________________________________________________________ 2.2 GSM Identifiers GSM Identifiers • IMEI – International Mobile Equipment Identifier • IMSI – International Mobile Subscriber Identifier • TMSI –Temporary Mobile Subscriber Identity • MSISDN – Mobile Subscriber ISDN number • MSRN – Mobile Station Roaming Number • LAI – Location Area Identity • CI – Cell Identifier • BSIC – Base Station Identity Code 2.2.1 IMEI – INTERNATIONAL MOBILE EQUIPMENT IDENTIFIER. The IMEI is an internationally-unique serial number allocated to the MS hardware at the time of manufacture. It is registered by the network operator and (optionally) stored in the AuC for validation purposes. 2.2.2 IMSI – INTERNATIONAL MOBILE SUBSCRIBER IDENTIFIER When a subscriber registers with a network operator, a unique subscriber IMSI identifier is issued and stored in the SIM of the MS. An MS can only function fully if it is operated with a valid SIM inserted into an
2. Architecture Overview 2.2.5 MSRN – MOBILE STATION ROAMING NUMBER The MSRN is a temporary, location-dependant ISDN number issued by the parent VLR to all MSs within its area of responsibility. It is stored in the VLR and associated HLR but not in the MS. The MSRN is used by the VLR-associated MSC for call routing within the MSC/VLR service area. 2.2.6 LAI – LOCATION AREA IDENTITY Each Location Area within the PLMN has an associated internationally-unique identifier (LAI). The LAI is broadcast regularly by BTSs on the Broadcast Control Channel (BCCH), thus uniquely identifying each cell with an associated LA. The purpose of LAs is covered later in this course. 2.2.7 CI – CELL IDENTIFIER The CI an identifier assigned to each cell within a network. However, the CI is only unique within a specific Location Area. When combined with the internationally unique LAI for its associated LA, the Global Cell Identity (GCI) is produced which is also internationally unique. 2.2.8 BSIC – BASE STATION IDENTITY CODE Each BTS is issued with a unique identity, the BSIC and is used to distinguish neighbouring BTSs. _________________________________________________________________________________ 2.3 General Architecture Overview GSM Architecture Overview Air Air Interface Abis Abis Interface Interface A A Interface Interface (Um) (Um) OMC MS VLR VLR BSS HLR HLR MS TRX MSC AuC AuC BTS BTS BSC MS EIR NSS NSS PSTN GSM Technology for Engineers © AIRCOM International 2002 13
2. Architecture Overview A GSM network is made up of three subsystems: • The Mobile Station (MS) • The Base Station Sub-system (BSS) – comprising a BSC and several BTSs • The Network and Switching Sub-system (NSS) – comprising an MSC and associated registers The interfaces defined between each of these sub systems include: • 'A' interface between NSS and BSS • 'Abis' interface between BSC and BTS (within the BSS) • 'Um' air interface between the BSS and the MS Abbreviations: MSC – Mobile Switching Centre BSS – Base Station Sub-system BSC – Base Station Controller HLR – Home Location Register BTS – Base Transceiver Station VLR – Visitor Location Register TRX – Transceiver AuC – Authentication Centre MS – Mobile Station EIR – Equipment Identity Register OMC – Operations and Maintenance Centre PSTN – Public Switched Telephone Network _________________________________________________________________________________ 2.4 The GSM Mobile Station (MS) The Mobile Station (MS) consists of the physical equipment used by a PLMN subscriber to connect to the network. It comprises the Mobile Equipment (ME) and the Subscriber Identity Module (SIM). The ME forms part of the Mobile Termination (MT) which, depending on the application and services, may also include various types of Terminal Equipment (TE) and associated Terminal Adapter (TA). GSM Mobile Terminal (MT) Reference Points R S Um m A Interface Interface Interface Interface TA Base Station GSM Core Subsystem Network SIM ME TE MS Mobile Mobile Terminal Terminal (MT) (MT) TE - Terminal Equipment TA - Terminal Adaptor MS - Mobile Station ME - Mobile Equipment SIM - Subscriber Identity Module GSM Technology for Engineers 14 © AIRCOM International 2002