CHAPTER 2 GSM AIR INTERFACE COMMON BEARER [2MBIT/S BTS…read.pudn.com/downloads61/ebook/212957/SYS01.pdf · · 2004-02-23chapter 2 gsm air interface review chapter 3 gsm air interface

CHAPTER 2GSM AIR INTERFACE

REVIEW

CHAPTER 3GSM AIR INTERFACE

PROTOCOL

CHAPTER 4COMMON BEARER [2MBIT/S

LINKS]

CHAPTER 5BTS–BSC INTERFACE

(A–BIS)

CHAPTER 1 INTRODUCTION TO GSM

INTERFACES

CHAPTER 7BSS–OMCR INTERFACE

(OML)

CHAPTER 8SMS CELL BROADCAST

LINK

GLOSSARY OF TERMS ANSWERSCHAPTER 6BSC–MSC INTERFACE

(A-INTERFACE)

Cellular Infrastructure Group

SYS01GSM SYSTEM INTERFACES

FOR TRAINING PURPOSES ONLY

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FOR TRAININGPURPOSES ONLY

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SYS01GSM SYSTEMINTERFACES

SYS01GSM SYSTEM INTERFACES

�MOTOROLA LTD. 2000 SYS01: GSM System Interfaces


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SYS01GSM System Interfaces

� Motorola 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000All Rights ReservedPrinted in the U.K.

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�MOTOROLA LTD. 2000SYS01: GSM System Interfaces


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Copyrights, notices and trademarks

CopyrightsThe Motorola products described in this document may include copyrighted Motorola computerprograms stored in semiconductor memories or other media. Laws in the United States and othercountries preserve for Motorola certain exclusive rights for copyright computer programs, including theexclusive right to copy or reproduce in any form the copyright computer program. Accordingly, anycopyright Motorola computer programs contained in the Motorola products described in this documentmay not be copied or reproduced in any manner without the express written permission of Motorola.Furthermore, the purchase of Motorola products shall not be deemed to grant either directly or byimplication, estoppel or otherwise, any license under the copyrights, patents or patent applications ofMotorola, except for the rights that arise by operation of law in the sale of a product.

RestrictionsThe software described in this document is the property of Motorola. It is furnished under a licenseagreement and may be used and/or disclosed only in accordance with the terms of the agreement.Software and documentation are copyright materials. Making unauthorized copies is prohibited bylaw. No part of the software or documentation may be reproduced, transmitted, transcribed, storedin a retrieval system, or translated into any language or computer language, in any form or by anymeans, without prior written permission of Motorola.

AccuracyWhile reasonable efforts have been made to assure the accuracy of this document, Motorolaassumes no liability resulting from any inaccuracies or omissions in this document, or from the useof the information obtained herein. Motorola reserves the right to make changes to any productsdescribed herein to improve reliability, function, or design, and reserves the right to revise thisdocument and to make changes from time to time in content hereof with no obligation to notify anyperson of revisions or changes. Motorola does not assume any liability arising out of the applicationor use of any product or circuit described herein; neither does it convey license under its patentrights of others.

Trademarks

and MOTOROLA are trademarks of Motorola Inc.UNIX is a registered trademark in the United States and other countries, licensed exclusively throughX/Open Company Limited.Tandem , Integrity , Integrity S2 , and Non-Stop-UX are trademarks of Tandem ComputersIncorporated.X Window System , X and X11 are trademarks of the Massachusetts Institute of Technology.Looking Glass is a registered trademark of Visix Software Ltd.OSF/Motif is a trademark of the Open Software Foundation.Ethernet is a trademark of the Xerox Corporation.Wingz is a trademark and INFORMIX is a registered trademark of Informix Software Ltd.SUN, SPARC, and SPARCStation are trademarks of Sun Microsystems Computer Corporation.IBM is a registered trademark of International Business Machines Corporation.HP is a registered trademark of Hewlett Packard Inc.

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General information 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important notice 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Purpose 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . About this manual 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cross references 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Text conventions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

First aid in case of electric shock 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Warning 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Artificial respiration 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Burns treatment 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reporting safety issues 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Procedure 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Warnings and cautions 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Warnings 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cautions 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General warnings 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Warning labels 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific warnings 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High voltage 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RF radiation 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laser radiation 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lifting equipment 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Do not ... 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Battery supplies 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Toxic material 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Human exposure to radio frequency energy (PCS1900 only) 8. . . . . . . . . . . . . . . . . . . . . . Introduction 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Definitions 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum permitted exposures 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum permitted exposure ceilings 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Example calculation 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power density measurements 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other equipment 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Beryllium health and safety precautions 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Health issues 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inhalation 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin contact 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eye contact 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handling procedures 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Disposal methods 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Product life cycle implications 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General cautions 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Caution labels 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific cautions 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fibre optics 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Static discharge 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Devices sensitive to static 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special handling techniques 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motorola GSM manual set 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generic manuals 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tandem OMC 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scaleable OMC 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Related manuals 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service manuals 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Category number 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Catalogue number 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ordering manuals 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1Introduction to GSM Interfaces i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction to GSM Interfaces 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM System Entities 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Architecture 1–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Links 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exercise 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Terrestrial Interfaces 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Open Systems Interconnection (OSI) 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Layer Concept 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Protocols 1–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Model 1–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Specifications 1–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 2GSM Air Interface Review i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Air Interface Review 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Air Interface 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bursts 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Timing Advance and Power Control 2–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mapping Logical Channels onto the TDMA Frame Structure 2–6. . . . . . . . . . . . . . . . . . . . . . Bursts 2–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multiframes and Timing 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The 26-frame Traffic Channel Multiframe 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The 51-frame Control Channel Multiframe – BCCH/CCCH 2–10. . . . . . . . . . . . . . . . . .

GSM Control Channels 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BCCH Group 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CCCH Group 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DCCH Group 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Multiframes and Timing 2–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The 51-frame Control Channel Multiframe – BCCH/CCCH 2–14. . . . . . . . . . . . . . . . . . The 51-frame Dedicated Control Channel Multiframe – SDCCH and SACCH 2–16. . The 51-frame Control Channel Multiframe – Combined Structure 2–18. . . . . . . . . . . .

Short Message Service Cell Broadcast (SMSCB) 2–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS Cell Broadcast 2–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple Background Messages 2–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 3GSM Air Interface Protocol i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GSM Air-interface Protocol 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Objectives 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MS – BTS Interface (Um or Air-interface) 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Air-interface – Layer 1 3–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Air-interface – Layer 1 (SACCH) 3–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Modes of Operation 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unacknowledged Operation 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledged Operation 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Data Link Connection Identifier (DLCI) 3–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Service Access Point Identifier 3–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Type of Control Channel 3–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Air-interface – Layer 2 3–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Format Peer-to-Peer Communication 3–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Frame Delimitation 3–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Address Field 3–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAPI – Service Access Point Identifier 3–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LPD – Link Protocol Discriminator 3–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Field Frame Formats 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P/F – Poll/Final bit 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S – Supervisory Function Bit(s) 3–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U – Unnumbered Function Bit 3–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Length Indicator 3–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of System Parameters (LAPDm) 3–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Air-interface – Layer 3 3–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 3–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Radio Resource Management Sub-layer 3–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mobility Management Sub-layer 3–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connection Management Sub-layer 3–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 3 – Frame Structure 3–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Protocol Discriminator/Skip Indicator 3–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Skip Indicator 3–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transaction Identifier 3–52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Type 3–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 3–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mobile Originating Call Establishment 3–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mobile Terminating Call Establishment 3–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Location Updating 3–62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Call Clearing 3–64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Message Flow Scenarios 3–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exercise 3–68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 4Common Bearer [2 Mbit/s Links] i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Common Bearer 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction 4–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Links – Common Channel Signalling 4–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transmission Code 4–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High Density Bipolar 3 (HDB3) 4–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time Division Multiplexing (TDM) 4–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rx Buffer/Slip Loss 4–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slip Loss Counters 4–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Frame Alignment Procedures 4–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N Bit 4–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Synchronization 4–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sync Loss Counters 4–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sync Timers 4–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GCLK Synchronization 4–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Remote Alarm 4–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Remote Loss Alarms 4–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bit Error Rate (BER) 4–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BER Timers 4–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BER Counters 4–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclic Redundancy Checking (CRC) 4–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclic Redundancy Check 4–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Database Command 4–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

High Bit-Rate Digital Subscriber Line (HDSL) 4–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 5BTS – BSC Interface (A-bis) i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BTS – BSC Interface 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSC – BTS Interface (A-bis) 5–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



A-bis Limitations 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Link Capacity 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Processors 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Redundancy 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Motorola Defined A-bis Interface (Mobis) 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motorola A-bis 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Division between BSC and BTS 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MTP L3/SCCP Preselector 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Connectionless Manager 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP State Machine (SSM) 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Switch Manager 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cell Resource Manager 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio Resource State Machine (RRSM) 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio Channel Interface 5–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motorola/GSM A-bis Comparison 5–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GSM A-bis 5–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motorola A-bis 5–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Interface Structure 5–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MSI Defaults 5–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Links Logical Channels 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio Signalling Link (RSL) 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transparent Messages 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layer 2 Management Link (L2ML) 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 2 – Link Access Procedure LAPD 5–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Structure 5–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Definition of Fields 5–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Address Field 5–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Access Point Identifier (SAPI) 5–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Terminal Endpoint Identifier (TEI) 5–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TEI Allocation 5–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Field 5–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Unnumbered Frames 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Set Asynchronous Balanced Mode Extended (SABME) Command 5–34. . . . . . . . . . . Disconnect (DISC) Command 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unnumbered Information (UI) Command 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unnumbered Acknowledgment (UA) Response 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Alignment Procedures 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layer 2 timers 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timer T203 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Supervisory Control 5–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 2 – Link Access Procedure LAPD 5–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Check Sequence (FCS) Field 5–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 3 Model 5–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Complete Layer 2/Layer 3 Message Example (A-bis Defined) 5–44. . . . . . . . . . . . . . . . . . . . . Encryption Command 5–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Discriminator 5–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Type 5–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 5–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Global Reset 5–52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mobile Originated Connection Establishment 5–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Message Sequence Scenarios 5–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Traffic Assignment Procedures 5–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Traffic Assignment Procedures 5–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Request Queued – T11 Expiry 5–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 5–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Successful Intra-BTS Handover 5–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Successful Inter-BSC Handover 5–62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix A 5–i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSC to BTS Interface Message Types 5–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part A – Message Types as Defined and Implemented by Motorola 5–ii. . . . . . . . . . . . . . . .

BSC to BTS Messages 5–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BTS to BSC Messages as Defined and Implemented by Motorola 5–iv. . . . . . . . . . .

Part B 5–vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Elements 5–vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1) Message Elements defined by GSM 08.08 5–vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2) Message Elements defined by GSM 08.58 5–ix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3) Message Elements defined by GSM 04.08 5–x. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4) Message Elements defined by GSM 04.08 5–xi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5) Message Elements defined by Motorola 5–xii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix B 5–i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSC to BTS Interface (A-bis) 5–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exercise 5–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 6BSC–MSC Interface (A-interface) i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSC–MSC Interface 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Objectives 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-interface Capabilities 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-interface specification objectives 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-interface Characteristics 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Specification 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 08.0x 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-Interface Functions 6–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Signalling System No7 (C7) 6–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction 6–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Messages Transfer Part (MTP) 6–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Level 2 Header Part 6–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LSSU Status Field Format 6–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alignment Procedure 6–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alignment Status Indications 6–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Signal Unit (MSU) 6–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Information Octet (SIO) 6–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Signalling Information Field (SIF) 6–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Routing Label 6–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Connection Control Part (SCCP) 6–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 6–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Protocol Classes 6–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP Message Format 6–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Establishment Procedure 6–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP Message Parameters 6–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP Message Example 6–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Called/Calling Party Address Parameter 6–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Radio Subsystem Application Part (BSSAP) 6–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSSAP Message Structure 6–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSSAP Message Header 6–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DTAP Header Structure 6–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP Header Structure 6–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSSAP Message Structure 6–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Complete Message Format 6–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS Management Application Part (BSSMAP) 6–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Procedures 6–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Normal Mobile Station (MS) to PSTN Call Set. 6–52. . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-Interface Messages 6–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Normal PSTN to MS Call 6–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-Interface Messages 6–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Call from PSTN to MS 6–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures – Global 6–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blocking 6–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Circuit Procedures 6–62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unblocking 6–64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Resource Indication 6–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Resource Indication Procedure 6–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Global Reset Procedure 6–68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset at the MSC 6–68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reset at the BSS 6–70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures – Global 6–72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset Circuit at the MSC 6–72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset Circuit at the BSS 6–72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paging 6–74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Candidate Enquiry 6–76. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flow Control 6–76. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures – Dedicated 6–78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assignment 6–78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Handover 6–80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Required Indication 6–80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Resource Allocation 6–80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Execution 6–82. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Release 6–84. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classmark Update 6–86. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cipher Mode Control 6–88. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Initial MS Message 6–90. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Queueing Indication 6–92. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Timers 6–94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MTP Level 2 Timers 6–94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MTP Level 3 Timers 6–94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP Timers 6–95. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix A 6–i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix A – MSC to BSC Interface (A-interface) 6–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exercise 6–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Appendix B 6–i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix B – MSC–BSS Message Types 6–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DTAP Messages 6–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP 6–iii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MSC–BSS Message Types 6–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP 6–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP Messages 6–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP Messages 6–v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 7BSS–OMCR Interface (OML) i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS–OMCR Interface 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS–OMCR Interface (OML) 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motorola Application Layer 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . File Transfer 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Event/Alarm Reporting 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Remote Login 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OMC–BSS Interconnection 7–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OML 7–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

X.25 Layers 7–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 7–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Physical Link Layer 1 7–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Data Link Layer 2 7–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overview 7–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Address Field 7–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Types – Control field encoding 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

X.25 Packet Level Protocol (PLP) 7–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Packet Header 7–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Logical Channel Numbers (LCN) 7–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Packet Type Identifier (PTI) 7–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Packet Types 7–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Additional Fields 7–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OMC to BSS Communication DTE Addresses 7–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Virtual Call Setup Procedure 7–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 8SMS Cell Broadcast Link i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS Cell Broadcast Link 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Short Message Service Cell Broadcast 8–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cell Broadcast Link (CBL) 8–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CBC, Cell Broadcast Responsibilities 8–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS, Cell Broadcast Responsibilities 8–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Mobiles Cell Broadcast Responsibilities 8–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS CB Database Commands 8–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Command Line 8–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description 8–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CBL Message Flow Scenarios 8–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CBL Protocol 8–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple SVC Connections 8–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cell Broadcast Messages from BSC to BTS 8–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS CB Message Structure (Air-Interface) 8–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRX Scheduling Message Coding 8–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . New SMS CB Message Bitmap 8–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . New SMS CB Message Description 8–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other Message Descriptions 8–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Description Encoding 8–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First Transmission of an SMS CB within the Schedule Period 8–26. . . . . . . . . . . . . . . Retransmission Indication 8–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Free Message Slot, Optional Reading 8–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Free Message Slot, Reading Advised (not yet implemented by Motorola) 8–28. . . . . Reserved Codepoints 8–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix AThe 24-Channel System 8–i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The 24-Channel (T1) System 8–ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24-Channel (T1) System 8–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Channel - associated signalling 8–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Common - channel signalling 8–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of T1 and E1 Systems 8–iv. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Glossary of Terms Glos–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Numbers Glos–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A Glos–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

B Glos–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C Glos–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

D Glos–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

E Glos–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F Glos–19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

G Glos–21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

H Glos–23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I Glos–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

K Glos–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

L Glos–27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

M Glos–29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

N Glos–33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

O Glos–35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P Glos–37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



xii

Q Glos–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

R Glos–41. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

S Glos–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T Glos–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

U Glos–51. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

V Glos–52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

W Glos–53. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

X Glos–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Z Glos–55. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Answers i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0 General information



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General information

Important notice

If this manual was obtained when you attended a Motorola training course, it will not beupdated or amended by Motorola. It is intended for TRAINING PURPOSES ONLY. If itwas supplied under normal operational circumstances, to support a major softwarerelease, then corrections will be supplied automatically by Motorola in the form ofGeneral Manual Revisions (GMRs).

Purpose

Motorola Global System for Mobile Communications (GSM) Technical Education manualsare intended to support the delivery of Technical Education only and are not intended toreplace the use of Customer Product Documentation.

Failure to comply with Motorola’s operation, installation and maintenanceinstructions may, in exceptional circumstances, lead to serious injury or death.

WARNING

These manuals are not intended to replace the system and equipment training offered byMotorola, although they can be used to supplement and enhance the knowledge gainedthrough such training.

About thismanual

The manual contains ...

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ISSUE 12 REVISION 0General information



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Cross references

Throughout this manual, cross references are made to the chapter numbers and sectionnames. The section name cross references are printed bold in text.

This manual is divided into uniquely identified and numbered chapters that, in turn, aredivided into sections. Sections are not numbered, but are individually named at the topof each page, and are listed in the table of contents.

Text conventions

The following conventions are used in the Motorola GSM manuals to represent keyboardinput text, screen output text and special key sequences.

Input

Characters typed in at the keyboard are shown like this.

Output

Messages, prompts, file listings, directories, utilities, and environmentalvariables that appear on the screen are shown like this.

Special key sequences

Special key sequences are represented as follows:

CTRL-c Press the Control and c keys at the same time.

ALT-f Press the Alt and f keys at the same time.

| Press the pipe symbol key.

CR or RETURN Press the Return (Enter) key. The Return key isidentified with the ↵ symbol on both the X terminal andthe SPARCstation keyboards. The SPARCstationkeyboard Return key is also identified with the wordReturn.

ISSUE 12 REVISION 0 First aid in case of electric shock



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First aid in case of electric shock

Warning

Do not touch the victim with your bare hands until the electric circuit isbroken.Switch off. If this is not possible, protect yourself with dry insulatingmaterial and pull or push the victim clear of the conductor.

WARNING

Artificialrespiration

In the event of an electric shock it may be necessary to carry out artificial respiration.Send for medical assistance immediately.

Burns treatment

If the patient is also suffering from burns, then, without hindrance to artificial respiration,carry out the following:

1. Do not attempt to remove clothing adhering to the burn.

2. If help is available, or as soon as artificial respiration is no longer required, coverthe wound with a dry dressing.

3. Do not apply oil or grease in any form.

ISSUE 12 REVISION 0Reporting safety issues



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Reporting safety issues

Introduction

Whenever a safety issue arises, carry out the following procedure in all instances.Ensure that all site personnel are familiar with this procedure.

Procedure

Whenever a safety issue arises:

1. Make the equipment concerned safe, for example, by removing power.

2. Make no further attempt to tamper with the equipment.

3. Report the problem directly to GSM MCSC +44 (0)1793 430040 (telephone) andfollow up with a written report by fax +44 (0)1793 430987 (fax).

4. Collect evidence from the equipment under the guidance of the MCSC.

ISSUE 12 REVISION 0 Warnings and cautions



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Warnings and cautions

Introduction

The following describes how warnings and cautions are used in this manual and in allmanuals of the Motorola GSM manual set.

Warnings

Definition

A warning is used to alert the reader to possible hazards that could cause loss of life,physical injury, or ill health. This includes hazards introduced during maintenance, forexample, the use of adhesives and solvents, as well as those inherent in the equipment.

Example and format

Do not look directly into fibre optic cables or optical data in/out connectors.Laser radiation can come from either the data in/out connectors orunterminated fibre optic cables connected to data in/out connectors.

WARNING

Cautions

Definition

A caution means that there is a possibility of damage to systems, or individual items ofequipment within a system. However, this presents no danger to personnel.

Example and format

Do not use test equipment that is beyond its calibration due date when testingMotorola base stations.

CAUTION

ISSUE 12 REVISION 0General warnings



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General warnings

Introduction

Observe the following warnings during all phases of operation, installation andmaintenance of the equipment described in the Motorola GSM manuals. Failure tocomply with these warnings, or with specific warnings elsewhere in the Motorola GSMmanuals, violates safety standards of design, manufacture and intended use of theequipment. Motorola assumes no liability for the customer’s failure to comply with theserequirements.

Warning labelsPersonnel working with or operating Motorola equipment must comply with any warninglabels fitted to the equipment. Warning labels must not be removed, painted over orobscured in any way.

Specificwarnings

Warnings particularly applicable to the equipment are positioned on the equipment andwithin the text of this manual. These must be observed by all personnel at all times whenworking with the equipment, as must any other warnings given in text, on the illustrationsand on the equipment.

High voltageCertain Motorola equipment operates from a dangerous high voltage of 230 V ac singlephase or 415 V ac three phase mains which is potentially lethal. Therefore, the areaswhere the ac mains power is present must not be approached until the warnings andcautions in the text and on the equipment have been complied with.

To achieve isolation of the equipment from the ac supply, the mains input isolator mustbe set to off and locked.

Within the United Kingdom (UK) regard must be paid to the requirements of theElectricity at Work Regulations 1989. There may also be specific country legislationwhich need to be complied with, depending on where the equipment is used.

RF radiationHigh RF potentials and electromagnetic fields are present in the base station equipmentwhen in operation. Ensure that all transmitters are switched off when any antennaconnections have to be changed. Do not key transmitters connected to unterminatedcavities or feeders.

Refer to the following standards:

� ANSI IEEE C95.1-1991, IEEE Standard for Safety Levels with Respect to HumanExposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz.

� CENELEC 95 ENV 50166-2, Human Exposure to Electromagnetic Fields HighFrequency (10kHz to 300GHz).

Laser radiationDo not look directly into fibre optic cables or optical data in/out connectors. Laserradiation can come from either the data in/out connectors or unterminated fibre opticcables connected to data in/out connectors.

ISSUE 12 REVISION 0 General warnings



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Liftingequipment

When dismantling heavy assemblies, or removing or replacing equipment, the competentresponsible person must ensure that adequate lifting facilities are available. Whereprovided, lifting frames must be used for these operations. When equipments have to bemanhandled, reference must be made to the Manual Handling of Loads Regulations1992 (UK) or to the relevant manual handling of loads legislation for the country in whichthe equipment is used.

Do not ...... substitute parts or modify equipment.

Because of the danger of introducing additional hazards, do not install substitute parts orperform any unauthorized modification of equipment. Contact Motorola if in doubt toensure that safety features are maintained.

Battery supplies

Do not wear earth straps when working with standby battery supplies.

Toxic material

Certain Motorola equipment incorporates components containing the highly toxic materialBeryllium or its oxide Beryllia or both. These materials are especially hazardous if:

� Beryllium materials are absorbed into the body tissues through the skin, mouth, ora wound.

� The dust created by breakage of Beryllia is inhaled.

� Toxic fumes are inhaled from Beryllium or Beryllia involved in a fire.

See the Beryllium health and safety precautions section for further information.

ISSUE 12 REVISION 0Human exposure to radio frequency energy (PCS1900 only)



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Human exposure to radio frequency energy (PCS1900 only)

IntroductionThis equipment is designed to generate and radiate radio frequency (RF) energy. Itshould be installed and maintained only by trained technicians. Licensees of the FederalCommunications Commission (FCC) using this equipment are responsible for insuringthat its installation and operation comply with FCC regulations designed to limit humanexposure to RF radiation in accordance with the American National Standards InstituteIEEE Standard C95.1-1991, IEEE Standard for Safety Levels with Respect to HumanExposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz.

DefinitionsThis standard establishes two sets of maximum permitted exposure limits, one forcontrolled environments and another, that allows less exposure, for uncontrolledenvironments. These terms are defined by the standard, as follows:

Uncontrolled environmentUncontrolled environments are locations where there is the exposure of individuals whohave no knowledge or control of their exposure. The exposures may occur in livingquarters or workplaces where there are no expectations that the exposure levels mayexceed those shown for uncontrolled environments in the table of maximum permittedexposure ceilings.

Controlled environment

Controlled environments are locations where there is exposure that may be incurred bypersons who are aware of the potential for exposure as a concomitant of employment, byother cognizant persons, or as the incidental result of transient passage through areaswhere analysis shows the exposure levels may be above those shown for uncontrolledenvironments but do not exceed the values shown for controlled environments in thetable of maximum permitted exposure ceilings.

Maximumpermittedexposures

The maximum permitted exposures prescribed by the standard are set in terms ofdifferent parameters of effects, depending on the frequency generated by the equipmentin question. At the frequency range of this Personal Communication System equipment,1930-1970MHz, the maximum permitted exposure levels are set in terms of powerdensity, whose definition and relationship to electric field and magnetic field strengths aredescribed by the standard as follows:

Power density (S)Power per unit area normal to the direction of propagation, usually expressed in units ofwatts per square metre (W/m2) or, for convenience, units such as milliwatts per squarecentimetre (mW/cm2). For plane waves, power density, electric field strength (E) andmagnetic field strength (H) are related by the impedance of free space, 377 ohms. Inparticular,

� ��

��

where E and H are expressed in units of V/m and A/m, respectively, and S in units ofW/m2. Although many survey instruments indicate power density units, the actualquantities measured are E or E2 or H or H2.

ISSUE 12 REVISION 0 Human exposure to radio frequency energy (PCS1900 only)



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Maximumpermittedexposureceilings

Within the frequency range, the maximum permitted exposure ceiling for uncontrolledenvironments is a power density (mW/cm2) that equals f/1500, where f is the frequencyexpressed in MHz, and measurements are averaged over a period of 30 minutes. Themaximum permitted exposure ceiling for controlled environments, also expressed inmW/cm2, is f/300 where measurements are averaged over 6 minutes. Applying theseprinciples to the minimum and maximum frequencies for which this equipment is intendedto be used yields the following maximum permitted exposure levels:

Uncontrolled Environment Controlled Environment

1930MHz 1970MHz 1930MHz 1970MHz

Ceiling 1.287mW/cm2 1.313mW/cm2 6.433mW/cm2 6.567mW/cm2

If you plan to operate the equipment at more than one frequency, compliance should beassured at the frequency which produces the lowest exposure ceiling (among thefrequencies at which operation will occur).

Licensees must be able to certify to the FCC that their facilities meet the above ceilings.Some lower power PCS devices, 100 milliwatts or less, are excluded from demonstratingcompliance, but this equipment operates at power levels orders of magnitude higher, andthe exclusion is not applicable.

Whether a given installation meets the maximum permitted exposure ceilings depends, inpart, upon antenna type, antenna placement and the output power to which thisequipment is adjusted. The following example sets forth the distances from the antennato which access should be prevented in order to comply with the uncontrolled andcontrolled environment exposure limits as set forth in the ANSI IEEE standards andcomputed above.

ISSUE 12 REVISION 0Human exposure to radio frequency energy (PCS1900 only)



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Examplecalculation

For a base station with the following characteristics, what is the minimum distance fromthe antenna necessary to meet the requirements of an uncontrolled environment?

Transmit frequency 1930MHz

Base station cabinet output power, P +39.0dBm (8 watts)

Antenna feeder cable loss, CL 2.0dB

Antenna input power Pin P–CL = +39.0–2.0 = +37.0dB (5watts)

Antenna gain, G 16.4dBi (43.65)

Using the following relationship:

� ��

��

Where W is the maximum permissible power density in W/m2 and r is the safe distancefrom the antenna in metres, the desired distance can be calculated as follows:

� ��

��

��

��

where W = 12.87 W/m2 was obtained from table listed above and converting frommW/cm2 to W/m2.

The above result applies only in the direction of maximum radiation of theantenna. Actual installations may employ antennas that have defined radiationpatterns and gains that differ from the example set forth above. The distancescalculated can vary depending on the actual antenna pattern and gain.

NOTE

Power densitymeasurements

While installation calculations such as the above are useful and essential in planning anddesign, validation that the operating facility using this equipment actually complies willrequire making power density measurements. For information on measuring RF fields fordetermining compliance with ANSI IEEE C95.1-1991, see IEEE Recommended Practicefor the Measure of Potentially Hazardous Electromagnetic Fields - RF and Microwave,IEEE Std C95.3-1991. Copies of IEEE C95.1-1991 and IEEE C95.3-1991 may bepurchased from the Institute of Electrical and Electronics Engineers, Inc., Attn:Publication Sales, 445 Hoes Lane, P.O. Box 1331, Piscattaway, NJ 08855-1331,(800) 678-IEEE or from ANSI, (212) 642-4900. Persons responsible for installation of thisequipment are urged to consult these standards in determining whether a giveninstallation complies with the applicable limits.

Other equipmentWhether a given installation meets ANSI standards for human exposure to radiofrequency radiation may depend not only on this equipment but also on whether theenvironments being assessed are being affected by radio frequency fields from otherequipment, the effects of which may add to the level of exposure. Accordingly, the overallexposure may be affected by radio frequency generating facilities that exist at the timethe licensee’s equipment is being installed or even by equipment installed later.Therefore, the effects of any such facilities must be considered in site selection and indetermining whether a particular installation meets the FCC requirements.

ISSUE 12 REVISION 0 Beryllium health and safety precautions



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Beryllium health and safety precautions

Introduction

Beryllium (Be), is a hard silver/white metal. It is stable in air, but burns brilliantly inOxygen.

With the exception of the naturally occurring Beryl ore (Beryllium Silicate), all Berylliumcompounds and Beryllium metal are potentially highly toxic.

Health issues

Beryllium Oxide is used within some components as an electrical insulator. Captivewithin the component it presents no health risk whatsoever. However, if the componentshould be broken open and the Beryllium Oxide, which is in the form of dust, released,there exists the potential for harm.

Inhalation

Inhalation of Beryllium Oxide can lead to a condition known as Berylliosis, the symptomsof Berylliosis are similar to Pneumonia and may be identified by all or any of thefollowing:

Mild poisoning causes fever, shortness of breath, and a cough that producesyellow/green sputum, or occasionally bloodstained sputum. Inflammation of the mucousmembranes of the nose, throat, and chest with discomfort, possibly pain, and difficultywith swallowing and breathing.

Severe poisoning causes chest pain and wheezing which may progress to severeshortness of breath due to congestion of the lungs. Incubation period for lung symptomsis 2–20 days.

Exposure to moderately high concentrations of Beryllium in air may produce a veryserious condition of the lungs. The injured person may become blue, feverish with rapidbreathing and raised pulse rate. Recovery is usual but may take several months. Therehave been deaths in the acute stage.

Chronic response. This condition is more truly a general one although the lungs aremainly affected. There may be lesions in the kidneys and the skin. Certain featuressupport the view that the condition is allergic. There is no relationship between thedegree of exposure and the severity of response and there is usually a time lag of up to10 years between exposure and the onset of the illness. Both sexes are equallysusceptible. The onset of the illness is insidious but only a small number of exposedpersons develop this reaction.

First aid

Seek immediate medical assistance. The casualty should be removed immediately fromthe exposure area and placed in a fresh air environment with breathing supported withOxygen where required. Any contaminated clothing should be removed. The casualtyshould be kept warm and at rest until medical aid arrives.

ISSUE 12 REVISION 0Beryllium health and safety precautions



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Skin contact

Possible irritation and redness at the contact area. Persistent itching and blisterformations can occur which usually resolve on removal from exposure.

First aid

Wash area thoroughly with soap and water. If skin is broken seek immediate medicalassistance.

Eye contact

May cause severe irritation, redness and swelling of eyelid(s) and inflammation of themucous membranes of the eyes.

First aid

Flush eyes with running water for at least 15 minutes. Seek medical assistance as soonas possible.

Handlingprocedures

Removal of components from printed circuit boards (PCBs) is to take place only atMotorola approved repair centres.

The removal station will be equipped with extraction equipment and all other protectiveequipment necessary for the safe removal of components containing Beryllium Oxide.

If during removal a component is accidently opened, the Beryllium Oxide dust is to bewetted into a paste and put into a container with a spatula or similar tool. Thespatula/tool used to collect the paste is also to be placed in the container. The containeris then to be sealed and labelled. A suitable respirator is to be worn at all times duringthis operation.

Components which are successfully removed are to be placed in a separate bag, sealedand labelled.

Disposalmethods

Beryllium Oxide or components containing Beryllium Oxide are to be treated ashazardous waste. All components must be removed where possible from boards and putinto sealed bags labelled Beryllium Oxide components. These bags must be given to thesafety and environmental adviser for disposal.

Under no circumstances are boards or components containing Beryllium Oxide to be putinto the general waste skips or incinerated.

Product life cycleimplications

Motorola GSM and analogue equipment includes components containing Beryllium Oxide(identified in text as appropriate and indicated by warning labels on the equipment).These components require specific disposal measures as indicated in the preceding(Disposal methods) paragraph. Motorola will arrange for the disposal of all suchhazardous waste as part of its Total Customer Satisfaction philosophy and will arrangefor the most environmentally “friendly” disposal available at that time.

ISSUE 12 REVISION 0 General cautions



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General cautions

Introduction

Observe the following cautions during operation, installation and maintenance of theequipment described in the Motorola GSM manuals. Failure to comply with thesecautions or with specific cautions elsewhere in the Motorola GSM manuals may result indamage to the equipment. Motorola assumes no liability for the customer’s failure tocomply with these requirements.

Caution labels

Personnel working with or operating Motorola equipment must comply with any cautionlabels fitted to the equipment. Caution labels must not be removed, painted over orobscured in any way.

Specific cautions

Cautions particularly applicable to the equipment are positioned within the text of thismanual. These must be observed by all personnel at all times when working with theequipment, as must any other cautions given in text, on the illustrations and on theequipment.

Fibre optics

The bending radius of all fibre optic cables must not be less than 30 mm.

Static discharge

Motorola equipment contains CMOS devices that are vulnerable to static discharge.Although the damage caused by static discharge may not be immediately apparent,CMOS devices may be damaged in the long term due to static discharge caused bymishandling. Wear an approved earth strap when adjusting or handling digital boards.

See Devices sensitive to static for further information.

ISSUE 12 REVISION 0Devices sensitive to static



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Devices sensitive to static

Introduction

Certain metal oxide semiconductor (MOS) devices embody in their design a thin layer ofinsulation that is susceptible to damage from electrostatic charge. Such a charge appliedto the leads of the device could cause irreparable damage.

These charges can be built up on nylon overalls, by friction, by pushing the hands intohigh insulation packing material or by use of unearthed soldering irons.

MOS devices are normally despatched from the manufacturers with the leads shortedtogether, for example, by metal foil eyelets, wire strapping, or by inserting the leads intoconductive plastic foam. Provided the leads are shorted it is safe to handle the device.

Special handlingtechniques

In the event of one of these devices having to be replaced observe the followingprecautions when handling the replacement:

� Always wear an earth strap which must be connected to the electrostatic point(ESP) on the equipment.

� Leave the short circuit on the leads until the last moment. It may be necessary toreplace the conductive foam by a piece of wire to enable the device to be fitted.

� Do not wear outer clothing made of nylon or similar man made material. A cottonoverall is preferable.

� If possible work on an earthed metal surface. Wipe insulated plastic work surfaceswith an anti-static cloth before starting the operation.

� All metal tools should be used and when not in use they should be placed on anearthed surface.

� Take care when removing components connected to electrostatic sensitivedevices. These components may be providing protection to the device.

When mounted onto printed circuit boards (PCBs), MOS devices are normally lesssusceptible to electrostatic damage. However PCBs should be handled with care,preferably by their edges and not by their tracks and pins, they should be transferreddirectly from their packing to the equipment (or the other way around) and never leftexposed on the workbench.

ISSUE 12 REVISION 0 Motorola GSM manual set



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Motorola GSM manual set

Introduction

The following manuals provide the information needed to operate, install and maintain theMotorola GSM equipment.

Generic manuals

The following are the generic manuals in the GSM manual set, these manuals arerelease dependent:

Categorynumber

Name Cataloguenumber

GSM-100-101 System Information: General 68P02901W01

GSM-100-201 Operating Information: GSM System Operation 68P02901W14

GSM-100-311 Technical Description: OMC in a GSM System 68P02901W31

GSM-100-313 Technical Description: OMC Database Schema 68P02901W34

GSM-100-320 Technical Description: BSS Implementation 68P02901W36

GSM-100-321 Technical Description: BSS CommandReference

68P02901W23

GSM-100-403 Installation & Configuration: GSM SystemConfiguration

68P02901W17

GSM-100-423 Installation & Configuration: BSS Optimization 68P02901W43

GSM-100-501 Maintenance Information: Alarm Handling atthe OMC

68P02901W26

GSM-100-521 Maintenance Information: Device StateTransitions

68P02901W57

GSM-100-523 Maintenance Information: BSS FieldTroubleshooting

68P02901W51

GSM-100-503 Maintenance Information: GSM StatisticsApplication

68P02901W56

GSM-100-721 Software Release Notes: BSS/RXCDR 68P02901W72

Tandem OMC

The following Tandem OMC manuals are part of the GSM manual set for systemsdeploying Tandem S300 and 1475:

Categorynumber


GSM-100-202 Operating Information: OMC SystemAdministration

68P02901W13

GSM-100-712 Software Release Notes: OMC System 68P02901W71

ISSUE 12 REVISION 0Motorola GSM manual set



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Scaleable OMC

The following Scaleable OMC manuals replace the equivalent Tandem OMC manuals inthe GSM manual set:

Categorynumber


GSM-100-202 Operating Information: Scaleable OMC SystemAdministration

68P02901W19

GSM-100-413 Installation & Configuration: Scaleable OMCClean Install

68P02901W47

GSM-100-712 Software Release Notes: Scaleable OMCSystem

68P02901W74

Related manuals

The following are related Motorola GSM manuals:

Categorynumber


GSM-001-103 System Information: BSS Equipment Planning 68P02900W21

GSM-002-103 System Information: DataGen 68P02900W22

GSM-005-103 System Information: Advance OperationalImpact

68P02900W25

GSM-008-403 Installation & Configuration: Expert Adviser 68P02900W36

Service manuals

The following are the service manuals in the GSM manual set, these manuals are notrelease dependent. The internal organization and makeup of service manual sets mayvary, they may consist of from one to four separate manuals, but they can all be orderedusing the overall catalogue number shown below:

Categorynumber


GSM-100-020 Service Manual: BTS 68P02901W37

GSM-100-030 Service Manual: BSC/RXCDR 68P02901W38

GSM-105-020 Service Manual: M-Cell2 68P02901W75

GSM-106-020 Service Manual: M-Cell6 68P02901W85

GSM-201-020 Service Manual: M-Cellcity 68P02901W95

GSM-202-020 Service Manual: M-Cellaccess 68P02901W65

GSM-101-SERIES ExCell4 Documentation Set 68P02900W50

GSM-103-SERIES ExCell6 Documentation Set 68P02900W70

GSM-102-SERIES TopCell Documentation Set 68P02901W80

GSM-200-SERIES M-Cellmicro Documentation Set 68P02901W90

ISSUE 12 REVISION 0 Motorola GSM manual set



17

Category number

The category number is used to identify the type and level of a manual. For example,manuals with the category number GSM-100-2xx contain operating information.

Cataloguenumber

The Motorola 68P catalogue number is used to order manuals.

Orderingmanuals

All orders for Motorola manuals must be placed with your Motorola Local Office orRepresentative. Manuals are ordered using the catalogue number. Remember, specifythe manual issue required by quoting the correct suffix letter.

ISSUE 12 REVISION 0Motorola GSM manual set



18



i

Chapter 1

Introduction to GSM Interfaces

ISSUE 12 REVISION 0



ii

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iii

Chapter 1Introduction to GSM Interfaces i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction to GSM Interfaces 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM System Entities 1–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Architecture 1–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Links 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exercise 1–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Terrestrial Interfaces 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 1–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Open Systems Interconnection (OSI) 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Layer Concept 1–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Protocols 1–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



ISSUE 12 REVISION 0



iv

ISSUE 12 REVISION 0 Introduction to GSM Interfaces



1–1

Introduction to GSM Interfaces

Objectives

On completion of this chapter the student will be able to:

� State the BSS terrestrial interfaces protocols and architecture.

� Identify the GSM specifications which apply to these protocols.

ISSUE 12 REVISION 0GSM System Entities



1–2

GSM System EntitiesOperations and Maintenance Centre (OMC) – A central network entity that controlsand monitors other network entities, including the quality of service provided by thenetwork.

Mobile Switching Centre (MSC) – The telephone switching exchange for mobileoriginated or terminated subscriber traffic.

Base Station System (BSS) – The fixed end of the radio interface that provides controland radio coverage functions for one or more sites and their associated Mobile Stations(MS). The Base Station Controller (BSC) and the Base Transceiver Station (BTS) arepart of the BSS.

Base Station Controller (BSC) – The Base Station System Control (BSSC) cabinet isonly used at BSC sites and provides the required expansion capabilities to interface tothe maximum number of remote BTSs allowed by the Motorola GSM BSS offering.

Base Transceiver Station (BTS) – The BTS cabinet is capable of operating as a BTSwith up to six Radio Frequency (RF) carriers in a single cabinet, utilising theHorizonmacro. The Horizonmicro and Horizoncompact can offer two carrier solutions.

Interworking Function (IWF) – Performs data rate adaption between the Public LandMobile Network (PLMN) and other existing land networks.

Transcoder Function (XC) – Converts the signal from 64Kbs A–law to 13Kbs GSMspeech, as well as 3 kbit/s of control information.

Authentication Centre (AUC) – Generates and stores authentication parameters forsubscriber identification.

Equipment Identity Register (EIR) – The database-oriented processing network entitythat contains centralized information for validating MSs based on their internationalmobile equipment identity.

Visitor Location Register (VLR) – The database-oriented processing network entitythat temporarily contains information for subscribers roaming in a given location area.

Home Location Register (HLR) – The database-oriented processing network entity thatcontains the master database of the subscribers to a PLMN.

Echo Canceller (EC) – Performs echo suppression for all voice circuits.

Mobile Station (MS) – The radio equipment and man-machine interface that asubscriber needs to access PLMN services.

Cell Broadcast Centre (CBC) – A user facility that allows the broadcast of shortmessage cell broadcast messages on a per cell, location area or PLMN basis.

ISSUE 12 REVISION 0 GSM System Entities



1–3

The GSM System

OMC(R)

MSC

VLR

HLR

AUC

EIR

IWF

BTS

BTS BTSBSC

BTS BTS BTS

EC PSTN

XC

OMC(S)

CBC

BSS

BTS

CO–LOCATED ENTITIES

MS

MS

SYS01_1_02

ISSUE 12 REVISION 0GSM Architecture



1–4

GSM ArchitectureGSM has defined the interfaces between the various components of the system, so faras it is necessary to ensure their correct functionality and also that satisfactoryinterworking with fixed networks can be provided. Only in this way can the GSM systemfunction be considered as a truly public telecommunications system.

As such, specific definitions are provided for the functional entities within a GSM systemand the interactions/interfaces between these entities.

The diagram illustrates the generalized architecture of the interfaces.

Several interfaces between these components can be recognized and consideration ofthem all is necessary for a complete understanding of the system.

Air-interface MS-BTS

A-bis (Mo-bis) BTS-BSC

A-interface BSS-MSC

B-interface MSC-VLR

C-interface MSC-HLR

D-interface HLR-VLR

E-interface Inter-MSC

F-interface MSC-EIR

G-interface VLR-VLR

R-interface MS-DTE

ISSUE 12 REVISION 0 GSM Architecture



1–5

GSM Architecture: Interface Types

DTE

MS

Air-interface A-interface

MSC

A-bis (Mo-bis)

MSC

EIR

VLR VLR

HLR

AUC

R

BSS

E

F

CC B

D

G

D

B

SYS01_1_03

MS = Mobile StationBSS = Base Station SystemBTS = Base Transceiver StationBSC = Base Site ControllerMSC = Mobile Switching CentreVLR = Visitor Location RegisterAUC = Authentication CentreRXCDR = Remote TranscoderDTE = Data Terminating Equipment

KEY

XCDRBSC

BTS

I

H

SMS

ISSUE 12 REVISION 0Signalling Links



1–6

Signalling Links

Exercise

Using the diagram opposite fill in the signalling links between each of the networkelements, stating the Motorola name of the link and which protocol is used on the link.

ISSUE 12 REVISION 0 Signalling Links



1–7

Exercise – Signalling Links

SYS01_1_04

MSC

BSC

BSC

BSC

RXCDR

MS

BSC

RXCDR

OMC–R

BTS

OMC–R

BTS

BSC CBC

NAME:

NAME:

NAME:

NAME:

NAME:

NAME:

NAME:

PROTOCOL:

PROTOCOL:

PROTOCOL:

PROTOCOL:

PROTOCOL:

PROTOCOL:

PROTOCOL:

ISSUE 12 REVISION 0Terrestrial Interfaces



1–8

Terrestrial Interfaces

Introduction

From the overall logical diagram of the GSM system, the Terrestrial interfaces compriseof all the connections between each of the GSM entities, apart from the Air-Interface.

The BSS interfaces and message protocols all conform to ITU-TS recommendationsenabling the system to be connected to different national telecommunications systems.

Terrestrial interfaces transport the traffic across the system and allow the passage of thethousands of data messages necessary to make the system function. They transport thedata for software downloads and uploads, the collection of statistical information,implementation of operations and maintenance commands.

The standard interfaces used are as follows;

� GSM ‘A-bis’ or ‘Motorola defined-mobis’; – (this is a Motorola interpretation of theA-bis which offers saving in resources)

� Signalling System ITU-TS #7 (‘C7);

� Packet Switching X25;

Whatever the interconnecting system, they share a common physical bearer betweentwo points, referred to as the 2 Mbit/s link.

Acronyms

TUP = Telephone User PartMAP = Mobile Application PartBSSAP = BSS Application PartMOMAP = Managed Objects Management PartITU-TS = International Telecommunications Union-Technical Specifications.

ISSUE 12 REVISION 0 Terrestrial Interfaces



1–9

Terrestrial Interfaces

OMCRAUC

SYS01_1_05

EC

MSC

PSTN

OMCROMC–R

OMCRXC

OMCRVLR OMCRVLR OMCRHLR

OMCREC OMCREC OMCRXC

BSC

BTS OMCRBTS

MS

OMCRBTS

OMCRBTS

OMCRBTS

OMCRBTSOMCRBTS

OMCRBSC

OMCRMSC OMCRMSC OMCREIR

OMCRPSTN

OMCROMCS

BSSAP on C7

MAP on C7

MAP on C7

MAP on C7

MOMAP on X.25MOMAP on x.25

TUP on C7GSM A-bis or

Motorola

ISSUE 12 REVISION 0Open Systems Interconnection (OSI)



1–10

Open Systems Interconnection (OSI)

Introduction

Users of information technology operate a wide range of data processing systems, officeautomation facilities and telecommunication networks in order to achieve their businessobjectives. The majority of such users recognise that there is a desperate need for suchsystems to be able to interwork effectively and efficiently. Furthermore, users havebecome increasingly unhappy at the prospect of being ‘locked in’ to any onemanufacturer’s range of equipment and proprietary methods of interconnecting systems.

The International Organisation for Standardisation (ISO) began work in 1979 on an opensystem architecture which is known as Open Systems Interconnection (OSI). Theultimate aim of OSI is simple – to provide a means whereby many different sorts ofsystems can communicate with each other economically and efficiently.

To achieve this, the ISO has developed a definition of the way systems communicate –the seven layer reference model.

The use of the model and defined standards should allow ‘open’ systems to be producedcreating an environment in which equipment, similar in function, but from anymanufacturing source, can be interconnected.

The LayerConcept

The method chosen was to view the total set of functions of a system as being dividedinto seven ‘layers’.

When the reference model was being developed a set of guiding principles were setdown:

� each layer has a unique and specific task to perform

� functions that are similar or highly inter-related are collected together within onelayer

� the internal design of a layer is independent of the functions it provides

� a layer only knows about its immediately adjacent layers

� a layer uses the services of the layer below

� a layer provides services to the layer above.

Each layer consists of a set of functions which provide specific services, which can bethought of as being performed by an abstract ‘entity’. The protocol operating betweenequivalent functions in the same layer of two different systems remote from each other isknown as the peer-to-peer protocol.

ISSUE 12 REVISION 0 Open Systems Interconnection (OSI)



1–11

The Reference Model

SYS01_1_06

Application

Presentation

Session

Transport

Network

Data Link

Physical

7

6

5

4

3

2

1

Users ofTransportService

NetworkService

TransportService

ISSUE 12 REVISION 0Protocols



1–12

ProtocolsThe concept of services in the OSI Model leads to an understanding of the data flowvertically within the architecture. Protocols define the way in which entities in the samelayer, but at different ends of the system, can communicate in a horizontal manner. Thisidea is termed ‘peer-to-peer’ protocol.

The requirements of the OSI protocols are achieved by each layer in the modelappending a quantity of data to the data unit ‘handed down’ from the layer above. Thisadditional data is protocol information which is stripped off and interpreted by thecorresponding peer entity at the remote end of the system.

Layer 1:

Physical; Responsible for the transparent transmission of information across the physicalmedium.

Layer 2:

Data Link; responsible for providing reliable transfer between the terminal and network.

Layer 3:

Network; responsible for setting up and maintaining the connection across a network.

Layer 4:

Transport; responsible for the control of quality of service.

Layer 5:

Session; Handles the co-ordination between the user processes.

Layer 6:

Presentation; responsible for ensuring that the information is presented to the eventualuser in a meaningful way

Layer 7:

Application; provides user interface to lower levels.

NOTE:

AH – Application Header

PH – Presentation Header

SH – Session Header

TH – Transport Header

NH – Network Header

LH – Link Header

ISSUE 12 REVISION 0 Protocols



1–13

OSI Layers

SYS01_1_07

AH

PH

DATA

SH

TH

NH

LH

Interface to lowerlevels

Formatting andcode

Coordination

Quality andservice

Setup andMaintenance

Reliable datatransfer

BIT STREAM

APPLICATIONLAYER

PRESENTATIONLAYER

SESSIONLAYER

TRANSPORTLAYER

NETWORKLAYER

LINKLAYER

PHYSICALLAYER

ISSUE 12 REVISION 0Signalling Model



1–14

Signalling ModelThe complete MSC to MS signalling model is shown opposite:

Connection Management (CM) and Mobility Management (MM) are not interpreted by theBSS (BSC or BTS) but are transferred using a procedure called Direct TransferApplication Part (DTAP) which is transparent to the BSS components.

Radio Resource (RR) messages are passed between the BTS and MS, however somemessages have to be forwarded to the BSC. The BTSM (BTS Management) entitiescontain procedures for handling these messages and other procedures for managing theBTS/BSC link.

The BSC to MSC link (A-interface) uses the signalling link structure of C7. The MessageTransfer Part (MTP) serves as a transport system for reliable transfer of messages.

The Signalling Connection Control Part (SCCP) builds on the underlying MTP to providea full network service as described by the OSI architecture.

The user function of the SCCP is the BSS Application Part (BSSAP) which uses onesignalling connection per active MS.

NOTE:

CM – Connection Management

MM – Mobility Management

RR – Radio Resource Management

LAPD – Link Access Procedure “D” (Data Channel)

LAPDm – Link Access Procedure “Dm” (Mobile “D” Channel)

BTSM – BTS Management

SCCP – Signalling Connection Control Part

MTP – Message Transfer Part

BSSAP – BSS Application Part

DTAP – Direct Transfer Application Part

ISSUE 12 REVISION 0 Signalling Model



1–15

Signalling Model

SYS01_1_08

CM

MM

BSSAP:DTAP/BSSMAP

MS BTS BSC MSC

MM

LAPDm

PhysicalLayer 1

CM

RRBSSAP

LAPDmSCCPMTP

SCCPMTP

RR

BTSM

Physical:Layer 1

LAPD

A–InterfaceA–bisRadio Air–interface

BTSM = BTS Management

KEY

Physical:Layer 1

LAPD

RR BTSM

Physical:Layer 1

ISSUE 12 REVISION 0GSM Specifications



1–16

GSM SpecificationsThe GSM committee has been responsible for the production of the standards and thetheoretical studies. The resultant specifications are divided into several sets ofspecifications, each providing a detailed description of a different aspect of the systemtogether with all the mandatory and optional features. These specifications makeextensive reference to existing ITU, CEPT and ISO standards.

These specifications are arranged under 12 main headings:

1. General

2. Services Aspects

3. Network Aspects

4. MS-BSS interface and Protocols

5. Physical layer on the Radio Path (Radio Sub-system)

6. Speech Coding

7. Terminal Adaptors for MS

8. BSC-MSC Interface

9. Network Interworking

10. Service Interworking

11. Equipment Specification and type approval

12. Network Management (operation and maintenance)

ITU – International Telecommunications Union

NOTE:

ITU-TS was formerly known as CCITT

ISSUE 12 REVISION 0 GSM Specifications



1–17

GSM Specifications

HLR

SYS01_1_9

05Radio Subsystem

06Speech Coding

09Network Interworking

07Terminal Adapters

10Service Interworking

04MS–BSS InterfaceMS

08MSC–BSC InterfaceBSS MSC

MSC

PSTN/ISDN

VLR




1–18



i

Chapter 2

GSM Air Interface Review

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 2GSM Air Interface Review i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Air Interface Review 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Air Interface 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bursts 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Timing Advance and Power Control 2–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mapping Logical Channels onto the TDMA Frame Structure 2–6. . . . . . . . . . . . . . . . . . . . . . Bursts 2–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multiframes and Timing 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The 26-frame Traffic Channel Multiframe 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The 51-frame Control Channel Multiframe – BCCH/CCCH 2–10. . . . . . . . . . . . . . . . . .

GSM Control Channels 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BCCH Group 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CCCH Group 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DCCH Group 2–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multiframes and Timing 2–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The 51-frame Control Channel Multiframe – BCCH/CCCH 2–14. . . . . . . . . . . . . . . . . . The 51-frame Dedicated Control Channel Multiframe – SDCCH and SACCH 2–16. . The 51-frame Control Channel Multiframe – Combined Structure 2–18. . . . . . . . . . . .

Short Message Service Cell Broadcast (SMSCB) 2–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS Cell Broadcast 2–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple Background Messages 2–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

ISSUE 12 REVISION 0 GSM Air Interface Review



2–1

GSM Air Interface Review

Objectives


� Understand the Air-interface Burst Structure.

� Understand the Air-interface Frame and multiframe structure.

� Understand the Air-interface implementation of SMS CB.

ISSUE 12 REVISION 0GSM Air Interface



2–2

GSM Air Interface

Bursts

Each carrier frequency used in GSM is divided into 8 independent timeslots and intoeach of these timeslots a burst is placed. The diagram shows the general format of aGSM burst.

The receiver can only receive the burst and decode it if it is received within the timeslotdesignated for it. The timing, therefore, must be extremely accurate, however, thestructure does allow for a small margin of error by incorporating a ‘guard period’ asshown in the diagram. To be precise, the timeslot is 0.577ms long, whereas the burst isslightly shorter at 0.546ms. Eight bursts occupy one TDMA frame.

The ‘‘flag-bits” are set when the frame has been ‘stolen’ by FACCH (the Fast AssociatedControl Channel). The ‘‘training sequence” is used by the receiver’s equaliser as itestimates the transfer characteristic of the physical path between the base-station andthe mobile.

ISSUE 12 REVISION 0 GSM Air Interface



2–3

GSM Burst and TDMA Frame

FRAME 2FRAME 1

NORMAL BURSTTRAINING

SEQUENCE

FLAG BITS

TAIL BITS

GUARDPERIOD

GUARDPERIOD

0 1 2 3 4 5 6 0 1 2 3 4 5 6 7

SYS01_2_2

7

ISSUE 12 REVISION 0Timing Advance and Power Control



2–4

Timing Advance and Power ControlTo simplify the design of the mobile, the GSM Recommendations specify an offset ofthree time-slots between the BSS and MS timing thus avoiding the necessity for themobile to transmit and receive simultaneously. The facing diagram illustrates this.

However, the synchronisation of a TDMA system is critical because bursts have to betransmitted and received within the “real-time” timeslots allotted to them. The further themobile is from the base station then, obviously, the longer it will take for the bursts totravel the distance between them. The GSM base-station caters for this problem byinstructing the MS to advance its timing (i.e. transmit earlier) to compensate for theincreased propagation delay.

This advance is then superimposed upon the 3 timeslot nominal offset, as shown.

‘‘Power Control” is an optional feature of the GSM air interface which allows the operatorto not only compensate for the distance from mobile to base-station as regards timing,but can also cause the base-station and mobile to adjust their power output to takeaccount of that distance. The closer the mobile is to the base-station, the less the powerit and the base-station will be required to transmit. This feature saves radio batterypower at the mobile, and helps to reduce co-channel and adjacent channel interference.

ISSUE 12 REVISION 0 Timing Advance and Power Control



2–5

Timing Advance

0 1 2 3 4 5 6 7

FRAME 1

0 1 2 3 4 5 6 7

FRAME 1

DOWNLINK

UPLINK

BS – MS

MS – BS

SYS01_2_3

TIMINGADVANCE

ISSUE 12 REVISION 0Mapping Logical Channels onto the TDMA Frame Structure



2–6

Mapping Logical Channels onto the TDMA Frame Structure

Bursts

The diagram shows the five types of burst employed in the GSM air-interface and showsthat all bursts, of whatever type, have to be timed so that they are received within theappropriate timeslot of the TDMA frame. The ‘‘burst” is the sequence of bits transmittedby the base-station or mobile – the ‘‘timeslot” is the discrete period of real time withinwhich it must arrive in order to be correctly decoded by the receiver.

1. Normal Burst. The normal burst carries traffic channels (both voice and data) and alltypes of control channels. It is bi-directional.

2. Frequency Correction Burst. This burst carries FCCH downlink to correct thefrequency of the mobile’s local oscillator, effectively locking it to that of the base-station.

3. Synchronisation Burst. So called because its function is to carry SCH downlink,synchronising the timing of the mobile to that of the base-station.

4. Dummy Burst. Timeslot 0 of the BCCH carrier will always contain control channelinformation but depending on configuration the remaining seven timeslots may be usedto support additional control channel information or a traffic channel. If any of theremaining seven timeslots are idle then Dummy bursts must be inserted as all eighttimeslots on the BCCH carrier must always be active.

5. Access Burst. This burst is of much shorter duration than the other types. Theincreased guard period is necessary because the timing of its transmission is unknown –this is due to the unknown quantity of the mobile’s location and the lack of timingadvance information at this point during the call set-up process.

ISSUE 12 REVISION 0 Mapping Logical Channels onto the TDMA Frame Structure



2–7

GSM Burst Types

SYS01_2_4

FRAME 1 FRAME 2

NORMAL BURST (NB)

Encoded Bits57

Training Sequence26

Training Sequence26

Encrypted Bits57

Encrypted Bits39

Encrypted Bits39

Encrypted Bits36

TB

TB

TB

TB

TB

TB

TB

TB

TB

TB

GP

GP

GP

GP

Synchronization Sequence64

Synchronization Sequence41

FREQ CORRECTION BURST (FB)

Fixed Bits142

Fixed Bits57

Fixed Bits57

SYNCHRONIZATION BURST (SB)

DUMMY BURST

ACCESS BURST

3 3

3

3

3

3

3

3

8

GP68.25

577 mS

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

ISSUE 12 REVISION 0Multiframes and Timing



2–8

Multiframes and TimingThere are eight timeslots within each TDMA frame, enabling eight physical channels toshare a single physical resource – the RF carrier. In turn, each physical channel may beshared by a number of logical control or traffic channels.

In order to understand how a single physical channel is shared by various logicalchannels, it is necessary to introduce the GSM multiframe structures that make itpossible.

The 26-frameTraffic ChannelMultiframe

The illustration opposite shows the time relationship between time-slot, TDMA frame, andthe 26-frame multiframe. Some of the times shown are approximate numbers as theGSM Recommendations actually state the exact values as fractions rather than indecimal form (eg. the exact duration of a timeslot is 15/26ms).

Note that frame 12 (the 13th frame in the 26 frame sequence) is used by SACCH, theSlow Associated Control Channel which carries link control information to and from themobile and base-station. The 8 timeslots of frame 12 accommodate 8 SACCHs – oneper TCH/FS (full-rate speech). Also note that frame 25 is idle. When the GSM‘‘half-rate” speech channel (TCH/HS) is a reality, this frame will carry the additional 8SACCHs required. The basic frame/timeslot structure remains identical (full-rate andhalf-rate channels will coexist) – each timeslot will carry two 11.4Kb/s channels insteadof one 22.8Kb/s channel. The SACCH bit rate will remain the same, hence the need forframe 25.

ISSUE 12 REVISION 0 Multiframes and Timing



2–9

26-Frame Multiframe

SYS01_2_5

17 6 5 4 3 2

2 01 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1

24 23 2122 20 19 18 17 16 15 14 13 11 10 9 8 7 6 5 4 3 2 0125 12

Idle

MultiframeSACCH

119.99mS

7 6 5 4 3 2 1 0

0.577 ms

4.615 ms

0

Time




2–10

The 51-frameControl ChannelMultiframe –BCCH/CCCH

The 51-frame structure used for control channels is considerably more complex than the26-frame structure used for the traffic channels and occurs in several forms, dependingon the type of control channel and the system operator’s requirements.




2–11

51-Frame Multiframes – Control Channel

SYS01_2_6

17 6 5 4 3 2

2 01 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1

24 23 2122 20 19 18 17 16 15 14 13 11 10 9 8 7 6 5 4 3 2 0125 12

Multiframe

235.365 mS

7 6 5 4 3 2 1 0

0.577 ms

4.615 ms

0

Time

50 49 4748 46 45 44 43 42 41 40 39 37 36 35 34 33 32 31 30 29 28 262738

ISSUE 12 REVISION 0GSM Control Channels



2–12

GSM Control ChannelsThese are: Broadcast Control Channel (BCCH).

Common Control Channel (CCCH).Dedicated Control Channel (DCCH).

BCCH Group

The Broadcast Control Channels are downlink only (base-station to mobile) andcomprises of the following:

� BCCH carries info about the network, a mobiles present cell and the surroundingcells. It is transmitted continuously as its signal strength is measured by allmobiles on surrounding cells.

� The Synchronising Channel (SCH) carries information for frame synchronisation.

� The Frequency Control Channel (FCCH) provides information for carriersynchronisation.

CCCH Group

The Common Control Channel Group is bi-directional i.e. it works in both the uplink anddownlink directions.

� Random Access Channel (RACH) is the ‘uplink’ used by mobiles to gain access tothe system.

� Paging Channel (PCH) and Access Granted Channel (AGCH) operate in the“downlink” direction. The AGCH is used to assign resources to the MS, such as aStandalone Dedicated Control Channel (SDCCH). The PCH is used by the systemto call a mobile. The PCH and AGCH are never used at the same time.

� Cell Broadcast Channel (CBCH) is used to transmit messages to be broadcast toall mobiles within a cell e.g. traffic information.

DCCH Group

Dedicated Control Channels are assigned to a single mobile for call setup and subscribervalidation. DCCH comprises of the following:

� Standalone Dedicated Control Channel (SDCCH) which supports the transfer ofData to and from the mobile during call setup and validation.

� Associated Control Channel. This consists of Slow ACCH which is used for radiolink measurement and power control messages. Fast ACCH is used to pass“event” type messages e.g. handover messages. Both FACCH and SACCHoperate in uplink and downlink directions.

ISSUE 12 REVISION 0 GSM Control Channels



2–13

Control Channels

SYS01_2_7

CCHControl Channel

DCCH

SDCCH ACCH

FACCH SACCH

BCCHdownlink only

PCH/AGCHdownlink only

RACHuplink

CBCHdownlink

CCCH

BCCH

SCH

Sync.channels

FCCH

NB/AB

NB/DB

SB

NBNBAB

NB

FB

NB = Normal BurstFB = Frequency BurstSB = Synchronization BurstAB = Access BurstDB = Dummy Burst

KEY




2–14

Multiframes and Timing

The 51-frameControl ChannelMultiframe –BCCH/CCCH

The BCCH/CCCH 51-frame structure illustrated on the opposite page will apply totimeslot 0 of each TDMA frame on the ‘BCCH carrier’ (the RF carrier frequency to whichthe BCCH is assigned on a per cell basis). In the diagram, each vertical step representsone repetition of the timeslot (= one TDMA frame), with the first repetition (numbered 0)at the bottom.

Looking at the uplink (MS – BSS) direction, all timeslot 0s are allocated to RACH. This isfairly obvious because RACH is the only control channel in the BCCH/CCCH group whichworks in the uplink direction. In the downlink direction (BSS – MS), the arrangement ismore interesting. Starting at frame 0 of the 51-frame structure, the first timeslot 0 isoccupied by a frequency burst (‘F’ in the diagram), the second by a synchronising burst(‘S’) and then the following four repetitions of timeslot 0 by BCCH data (B) in frames 2 –5. The following four repetitions of timeslot 0 in frames 6 – 9 are allocated to CCCHtraffic (C) – that is, to either PCH (mobile paging channel) or AGCH (Access GrantChannel). Then follows, in timeslot 0 of frames 10 and 11, a repeat of the frequency andsychronising bursts (F and S), four further CCCH bursts (C) and so on ... . Note that thelast time-slot 0 in the sequence (the fifty-first frame – frame 50) is idle.




2–15

BCCH/CCCH Multiframe

R = RACH (Random)B = BCCH (Broadcast)F = FCCH (Frequency)S = SCH (Sync.)C = CCCH (Common)I = Idle

0 10 20 30 40 50

F S F S F S F S F S IB C C C C C C C C C

0 10 20 30 40 50

Uplink

Downlink

RRR RRR RRRR RRRR RRRR RRR RRRR RRRR RRR RRRR RRRR RRRR RRR RRRR

SYS01_2_8

KEY




2–16

The 51-frameDedicatedControl ChannelMultiframe –SDCCH andSACCH

The diagram shows the 51-frame structure used to accommodate 8 SDCCHs although,as it takes two repetitions of the multiframe to complete the entire sequence, it may bemore logical to think of it as a 102-frame structure! This structure will be used on aphysical channel selected by the system operator – it is not placed in a timeslot or on anRF carrier defined by GSM Recommendations.

Note that the 8 SACCHs (shaded) are associated with the 8 SDCCHs. It is important toremember that each SDCCH has an SACCH just like a traffic channel.




2–17

DCCH Multiframe

0 10 20 30 40 50

Downlink

I I IA0D0 D1 D2 D3 D4 D5 D6 D7

I I IA7A6A5A4D0 D1 D2 D3 D4 D5 D6 D7

A3A2

0 10 20 30 40 50

Uplink

D5D4A5 A6 A7 D0 D1 D2 D3

D7D6D5D4A1 A2 A3 D0 D1 D2 D3

D7D6 A0

A4

I I I

I I I

A1

D = SDDCH/8 (Dedicated)A = SACCH/C8 (Associated)I = Idle

SYS01_2_9

KEY




2–18

The 51-frameControl ChannelMultiframe –CombinedStructure

The structure illustrated can be used where traffic density is low – perhaps in a rural areain cells with few RF carriers and only light traffic. Again, as it takes two repetitions of the51-frame multiframe to complete the sequence, this is really a 102-frame structure.

In this case, all the control channels (with the exception of the ‘frame-stealer’ FACCH)share the BCCH carrier timeslot 0.




2–19

Combined Multiframe

0 10 20 30 40 50

Downlink

0 10 20 30 40 50

Uplink

R = RACH (Random)B = BCCH (Broadcast)F = FCCH (Frequency)S = SCH (Sync.)C = CCCH (Common)D = SDCCH/4 (Dedicated)A = SACCH/4 (Associated)I = Idle

F

F

S

S

C

C

F

F

S

S

F

F

S

S

D0

D0

D1

D1

F

F

S

S

D2

D2

D3

D3

F

F

S

S

A0

A2

A1

A3

I

IB

B C

C

C

C

D3

D3

R

R

R

R RRRR

RR RR RR

R RR

R R

R

R

R

R

R

R

R

R

R

R

R

R

R

R

RR

R

R

R

R

RR

R R

R

R

RRR

RR

A2

A0

A3

A1

D0

D0

D1

D1

D2

D2

RR

RR

SYS01_2_10

KEY

ISSUE 12 REVISION 0Short Message Service Cell Broadcast (SMSCB)



2–20

Short Message Service Cell Broadcast (SMSCB)There are a number of database parameters which control the use of Short MessageService. The service itself is specified by GSM and can be divided into two functions CellBroadcast and Point to Point.

When a short message service cell broadcast (SMSCB) message is to be sent, themessage shall be sent on the Cell Broadcast Channel (CBCH) in four consecutivemultiframes using the block defined on the page opposite.

The SMSCB header shall be sent in the multiframe on TB=0. When SMSCB is in use,this is indicated in the BCCH data.

If this option is enabled, frequency, slot, and subslot information present within BCCHsystem information will cause suitably equipped mobiles to monitor the Cell BroadcastChannel (CBCH). This channel, when enabled, fits into the 51/102 frame multiframe inplace of SDCCH number 2. It can appear on BCCH or Non-BCCH carriers on timeslots0-3 inclusive. Only one CBCH will exist within a cell and an algorithm will control itswhereabouts. A cell broadcast block is made up of 23 bytes (184 bits) which is encodedto produce the familiar 456 bit block, this is then transmitted over four successive airinterface bursts. In the case where the CBCH resides on a BCCH carrier dummy burstswill be transmitted in the other 4 multiframes.

ISSUE 12 REVISION 0 Short Message Service Cell Broadcast (SMSCB)



2–21

Short Message Service Cell Broadcast

0 10 20 30 40 50

Downlink

0 10 20 30 40 50

F

F

S

S

C

C

F

F

S

S

F

F

S

S

D0

D0

D1

D1

F

F

S

S

D3

D3

F

F

S

S

A0

A2

A1

A3

I

IB

B C

C

C

C

D0

D0

SYS01_2_11

D1

D1

D3

D3

D4

D4

D5

D5

D6

D6

D7

D7

A0

A0

A1

A1

A2

A2

A3

A3

CBCH

CBCH0 1 2 3

I

I I I

II

SMSCB(normalburst)

0 1 2 3

0 1 2 3

0 1 2 3

SMSCB(normalburst)

CBCH

CBCH

DCCH Multiframe

Combined Multiframe

ISSUE 12 REVISION 0SMS Cell Broadcast



2–22

SMS Cell BroadcastThe GSM defined Cell Broadcast feature is a means of unilaterally transmitting data tomobiles on a per cell basis, by use of the Cell Broadcast channel. Each BSC should beconnected to a Cell Broadcast Centre, which is responsible for downloading cellbroadcast messages to the BSC, together with repetition rate, and the number ofbroadcasts required per message. The BSC is then responsible for transmitting theseupdates to the BTS’s affected, which will then ensure that the message is transmitted asrequested. In 1400 the full GSM functionality is available, in particular the BSC to CBCinterface is supported. However, a single operator defined background message may beentered using the appropriate database command.

The parameters controlling cell broadcast SMS are shown below:

Chg_element cbch_enabled <*><SITE No> cell number = <GSM Cell id>

* 0 disabled 1 enabled

MultipleBackgroundMessages

Background messages can be a maximum of 93 characters and will be sent on theSMSCB channel in the absence of messages originating from the Cell Broadcast Center(CBC). A maximum of four background messages can be specified using the followingdatabase commands:

chg_smscb_msg <msg_num> <msg_id> <gs> <msg_code> <language>cell_number= <cell id>

msg_num (0–3) This number is not sent to the MS, but is used as a message identifier within the Motorola BSS software.

msg_id (0–65535) Identifies the logical channel used within the physical CBSMS slot. This corresponds to the ’channel number’ entered in the MMI of the MS.

gs (0–3) This field indicates to the MS the geographical area overwhich the message code is unique. It also indicates the display mode to the mobile.

0 – Immediate, Cell Wide1 – Normal, PLMN Wide2 – Normal, Location Area (LAC) Wide3 – Normal, Cell Wide

msg_code (0–1023) This field is used by the MS to differentiate between different messages being broadcast using the same msg_id.

language (0–12) This field specifies the alphabet/coding scheme being used in the message. Values specified in W23.

ISSUE 12 REVISION 0 SMS Cell Broadcast



2–23

SMS Cell Broadcast

SYS01_2_12

184 bits

23 bytes 23 bytes 23 bytes

456 bits

23 bytes

57bits

burst1

burst4

burst3

burst2

Dummy bursts (BCCH only)

Each block contains a51 frame multiframe

57bits

57bits

57bits

57bits

57bits

57bits

57bits

Part of original message

4 successive bursts

CBCH

Fire code andconvolutional coding

8 blocks of 57 bits

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

1 2 3 4 5 6 7 00 1 2 3 4 5 6 7

ISSUE 12 REVISION 0SMS Cell Broadcast



2–24



i

Chapter 3

GSM Air Interface Protocol

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 3GSM Air Interface Protocol i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Air-interface Protocol 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MS – BTS Interface (Um or Air-interface) 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Air-interface – Layer 1 (SACCH) 3–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


Modes of Operation 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unacknowledged Operation 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledged Operation 3–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Data Link Connection Identifier (DLCI) 3–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Service Access Point Identifier 3–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Type of Control Channel 3–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Air-interface – Layer 2 3–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Format Peer-to-Peer Communication 3–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Frame Delimitation 3–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Address Field 3–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SAPI – Service Access Point Identifier 3–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LPD – Link Protocol Discriminator 3–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Field Frame Formats 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P/F – Poll/Final bit 3–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S – Supervisory Function Bit(s) 3–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U – Unnumbered Function Bit 3–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Length Indicator 3–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

List of System Parameters (LAPDm) 3–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Air-interface – Layer 3 3–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 3–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Radio Resource Management Sub-layer 3–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mobility Management Sub-layer 3–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Connection Management Sub-layer 3–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 3 – Frame Structure 3–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Protocol Discriminator/Skip Indicator 3–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Skip Indicator 3–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transaction Identifier 3–52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Type 3–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 3–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mobile Originating Call Establishment 3–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mobile Terminating Call Establishment 3–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Location Updating 3–62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Call Clearing 3–64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Flow Scenarios 3–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exercise 3–68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

ISSUE 12 REVISION 0 GSM Air-interface Protocol



3–1

GSM Air-interface Protocol

Objectives


� State the BSS Air-interface’s protocols and architecture.

� Identify the GSM specifications which apply to these protocols.

ISSUE 12 REVISION 0MS – BTS Interface (Um or Air-interface)



3–2

MS – BTS Interface (Um or Air-interface)

The air-interface supports the logical channels which allow the MS to establishcommunication with the GSM terrestrial network (BSS).

The following GSM specifications define the structure and procedures of this interface:

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Note:

There are additional parts to the 04.xx series of recommendations, 04.2x details rateadaption and radio link protocol while the 04.8x series details supplementary services.

ISSUE 12 REVISION 0 MS – BTS Interface (Um or Air-interface)



3–3

MS – BTS Interface (Air-interface) GSM Recommendations

SYS01_3_2

GSM Recs. Description04.03 MS–BSS Interface Channel structure and access

capabilities04.04 Layer 1 General requirements04.05 Data Link Layer (Layer 2) – General aspects04.06 Data Link Layer (Layer 2) – Specification04.07 Mobile radio interface signalling Layer 3 – General

aspects04.08 Mobile radio interface signalling Layer 3 – Specification04.10 Layer 3 – Supplementary services specification general

aspects04.11 Point-to-point Short Message Service support (Layer 3)04.12 Short Message Service Cell Broadcast (Layer 3)

Note:

There are additional parts to the 04.xx series of recommendations, 04.2x details rate adaptionand radio link protocol while the 04.8x series details supplementary services.

ISSUE 12 REVISION 0Air-interface – Layer 1



3–4

Air-interface – Layer 1The diagram opposite shows the layer relationship between the MS – BTS. From thediagram we can see that traffic channels are catered for with other functional units, theseinterfaces are described in the 06 and 07 series of Technical Specifications and will notbe covered on this course.

The Data Link Layer (Layer 2) is where the control channels are supported (PCH+AGCH,SACCH etc.), Layer 2 frames are also passed from the Data Link Layer to the PhysicalLayer.

The Physical Layer also communicates directly to the Radio Resources Managementlayer for the purposes of channel assignment, physical system layer information(including, measurement results, timing advance etc).

ISSUE 12 REVISION 0 Air-interface – Layer 1



3–5

MS–BTS Signalling Model (Layers 1–3)

SYS01_3_3

PhysicalLayer

(Layer 1)

RadioResources

Management(Layer 3)

Data LinkLayer

(Layer 2)

To FunctionalUnits (TCH)

PhysicalLayer

(Layer 1)

RadioResources

Management(Layer 3)

Data LinkLayer

(Layer 2)

To FunctionalUnits (TCH)

MS BTS




3–6

Air-interface – Layer 1The Physical Layer supports the transfer of bit streams on the radio medium according toTS GSM 05-series.

In the OSIRM, Service Access Points (SAPs) of a layer are defined as gates throughwhich services are offered to an adjacent layer. Through a SAP the Physical Layer offersservices to the Data Link Layer (Layer 2). The SAP is used for both the control of theservice providing entity and the transfer of data. In GSM the SAPs for the Physical Layerdiffer from the OSI Layer SAPs; the Layer 3 RR-management instead of the Data LinkLayer (Layer2) controls the SAPs (establishment and release of channels).

On the Physical Layer of GSM system a SAP is defined between the Data Link Layerand the Physical Layer for each control channel.

Using Primitives (communication between layers) the Physical Layer interacts with Layer2 and Layer 3, in line with the services required.

OSIRM – Open Systems Interconnect Reference Model




3–7

SAPs between the Physical Layer and the Data Link Layer

SYS01_3_4

Physical Layer (Layer 1)

BCCHPCH

+AGCH

RACH SDCCH SACCH FACCH

There is one SAP for each control channel




3–8

GSM recommendations define five states that a mobile can be in at any one time. Thesefive individual states are shown in the table opposite.

From switch on, idle mode and then to dedicated mode, the Mobile Subscriber must gothrough these five states in order to establish and maintain a call.




3–9

MS – Physical Layer States

SYS01_3_5

STATE DescriptionNULL The equipment is switched off

SEARCHING BCH The Physical Layer tracks the bestBCCH

BCH The Physical Layer listens to aBCCH/CCCH and is able to doRandom Access

TUNING DCH The Physical Layer seizes on a physicaldedicated channel

DCH The physical layer has seized adedicated channel and may establishand through connect logical channels

In the Physical Layer of the MS the following states are defined:

Note:

BCH = Bcch/ccch physical CHannelDCH = Dedicated physical CHannel

ISSUE 12 REVISION 0Air-interface – Layer 1 (SACCH)



3–10

Air-interface – Layer 1 (SACCH)On a Dedicated Control Channel, the Physical Layers at both the MS and BSS,implement a Peer-to-Peer protocol for the control of timing advance and power control.

For this purpose the Physical Layer adds a 2 octet physical header on all SACCH blocks(a logical channel always present on a dedicated physical channel). This physical headercontains the ordered MS power level and ordered timing advance. If no timing advanceis ordered the timing field is coded with “111 111”. The timing advance is defined in steps0 to 63, values 64 to 126 are reserved.

Procedures for handling the ordered timing advance, power control, as well as theresponse from the MS in the form of actual timing advance, power control are defined inGSM 05.05/05.08 and GSM 05.10 respectively.

ISSUE 12 REVISION 0 Air-interface – Layer 1 (SACCH)



3–11

SACCH Block Format (UL & DL)

SYS01_3_6

Spare

Spare Ordered MS Power Level

Ordered Timing Advance

Layer 2and

Layer 3Information

8 7 6 5 4 3 2 1

Octet 1

Octet 2

Octet 3

Octet 23

BSS – MS

Spare

Spare Actual MS Power Level

Actual Timing Advance

Layer 2and

Layer 3Information

8 7 6 5 4 3 2 1

Octet 1

Octet 2

Octet 23

MS – BSS




3–12

Air-interface – Layer 2The Data Link Layer is the OSI layer 2 entity on the air interface. The Data Link Layerprovides services to Layer 3 and is served by the Physical Layer.

The Data Link Layer uses LAPDm on all the control channels except the RACH (this willbe covered separately on the course).

LAPDm is designed to specifically support :

� Multiple Layer 3 entities

� Multiple Physical Layer entities

� BCCH signalling

� PCH signalling

� AGCH signalling

� DCCH (SDCCH, SACCH, FACCH) signalling

LAPDm includes functions for:

� The provision of one or more data link connections on a Dm channel.Discrimination between the data link connections is by means of a Data LinkConnection Identifier (DLCI).

� Organisation of Layer 3 information into frames.

� Peer-to-Peer transmission of signalling data in defined frame formats.

� Recognition of frame formats.

� Establishment, maintenance (supervision) and termination of one or more (parallel)data links on signalling channels.

� Acknowledgement of transmission and reception of information frames (I frames).

� Unacknowledged transmission and reception of unnumbered information frames(UI frames).

� Detection of format and operational errors on a data link.

� Flow control.

� Contention Resolution when establishing data link after an access request hasbeen made on the RACH.




3–13

Air-interface – Layer 2

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ISSUE 12 REVISION 0Modes of Operation



3–14

Modes of Operation

UnacknowledgedOperation

In unacknowledged operation, Layer 3 information is transmitted in UnnumberedInformation (UI) frames.

At the Data Link Layer, the UI frames are not acknowledged. Flow control mechanismsand error recovery mechanisms are not defined.

AcknowledgedOperation

In this mode Layer 3, information is transmitted in frames and is acknowledged by thereceiving Data Link Layer. Error recovery by retransmission of unacknowledged frames isspecified. In the case where errors which cannot be recovered by the Data Link Layer, aprocedure exists to notify Layer 3. Flow control procedures are also defined.

Only one form of acknowledged information transfer is defined, ie. Multiple frameoperation.

For Multiple frame operation, Layer 3 information is sent in numbered information frames,in principle a number of I frames may be outstanding at the same time (K value = 0–7).However for many applications a window size of 1 is required. The procedure for Multipleframe operation is initiated by using the Set Asynchronous Balanced Mode (SABM)

The acknowledged mode of information transfer in the Data Link Layer offerssegmentation at the transmitter of Layer 3 message units if the message unit is longerthan the information field of the data layer frames. At the receiver the segmented Layer 3message units are concatenated such that the integrity of the Layer 3 message unit isrestored.

ISSUE 12 REVISION 0 Modes of Operation



3–15

Mode of Operation and Allowed SAPI’s

SYS01_3_8

Type of Channel SAPI=0 SAPI=3

BCCH Unacknowledged Not Supported

CCCH Unacknowledged Not Supported

SDCCH Unacknowledged andacknowledged

Acknowledged

SACCH associated withSDCCH

Unacknowledged Not Supported

SACCH associated with TCH Unacknowledged Acknowledged

FACCH Unacknowledged andacknowledged

Not Supported

ISSUE 12 REVISION 0Data Link Connection Identifier (DLCI)



3–16

Data Link Connection Identifier (DLCI)The DLCI consists of two elements:

1. ServiceAccess PointIdentifier

The SAPI is carried in the address field of each frame and determines to which and fromwhich Layer 3 entity a message is to be transported by Layer 2. On the air interface onlytwo SAPI values (0 & 3) are currently supported, others may be defined in the future.

The SAPI takes a specific value for the following functions on the Dm channel:

SAPI = 0:

Call Control Signalling (TS GSM 04.08 )

Mobility Management Signalling (TS GSM 04.08 )

Supplementary Services Signalling (TS GSM 04.10)

Radio Resource Management Signalling (TS GSM 04.08 )

SAPI = 3

Short Message Services (TS GSM 04.11)

Priority of SAPIs

On SDCCH:

Highest priority: SAPI = 0

Lowest priority: SAPI = 3

On SACCH

The priority arrangement on the SACCH must ensure that if a SAPI=3 frame is awaiting transmission, two SAPI=0 frames are not sent in consecutive SACCH frames. In addition, for the MS to network direction it must also be ensured that any SAPI=3 frame is followedby at least one SAPI=0 frame.

ISSUE 12 REVISION 0 Data Link Connection Identifier (DLCI)



3–17

SAPIs

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ISSUE 12 REVISION 0Data Link Connection Identifier (DLCI)



3–18

2. Type ofControl Channel

The type of control channel on which the Data Link Connection is to be established. Thisinformation is not carried in frames between Data Link Layer peer entities but is managedlocally in each system and is carried in primitives between layers.

Procedure for Transmission of Message Unit

A. The Network Layer (Layer 3) will select the appropriate SAP and DLCI.

B. The Network Layer (Layer 3) will indicate to the Data Link Layer which endpointhas been chosen.

Procedure upon Receipt of a Message Unit

A. When the Data Link Layer Receives a frame containing a Layer 3 message unit, itwill have also received from the Physical Layer an indication concerning the typeof channel on which the message unit was received.

B. This combined information together with the SAPI will enable the Data Link Layerto deliver the Layer 3 message unit to the required Data Link connection endpointof the indicated SAP.

ISSUE 12 REVISION 0 Data Link Connection Identifier (DLCI)



3–19

Signalling model showing channels SAPs and SAPIs

SYS01_3_10

Network Layer 3

DataLink

RandomAccess

DataLink

ProcedureUI

DataLink

ProcedureUI

DataLink

ProcedureMF + UI

DataLink

ProcedureMF + UI

DataLink

ProcedureUI

DataLink

ProcedureMF

Data Link Layer 2

Physical Layer 1

SAPI = 3SAPI = 0

Data Link DistributionProcedure

RACH BCCH PCH + AGCH SDCCH FACCH SACCH + SDCCH

Key:

UI = Unacknowledged InformationMF = Multiframe Operation




3–20


Frame FormatPeer-to-PeerCommunication

A number of different frame formats exist for the Layer 2 peer-to-peer communicationprocedure (LAPDm).

Format A

This format is used on a DCCH for frames where there is no real Layer 3 information tobe transmitted.

It often occurs that Layer 2 (the receiving entity) does not have a Layer 3 message tosend after receiving a frame, which requires acknowledging, from its peer. Should thisbe the case, the Layer 2 entity will simply transmit an empty frame to acknowledgereceipt of the last frame, but as yet does not have any information to send in response.The empty frame will contain fill bits, coded with the hexadecimal value 2B or FF.

Format B

This format is used on a DCCH for frames containing an information field.




3–21

Layer 2 Frame Structures

Format A

SYS01_3_11

Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Octet No

1

Address Field

k

Control Field k+1

k+2

Length Indicator Field

n

n+1

Fill Bits

(Hexadecimal Value 2B or FF) N201+n

Format B

SYS01_3_12


1

Address Field

k

Control Field k+1

k+2

Length Indicator Field

n

n+1

Information Field

N

N+1

Fill Bits

(Hexadecimal Value 2B or FF) N201+n




3–22

Frame FormatPeer-to-PeerCommunication

Format Bbis

This format is used only on BCCH, PCH and AGCH.

Only used in the unacknowledging mode of signalling data transfer.

Format C

The random access procedure is not LAPDm. Layer 3 is responsible for generating the 8bit information content of the random access burst and using the primitives will pass thisinformation to the Data Link Layer, the primitives will also contain which type of channelto use.

The Data Link Layer will then using the Physical primitives pass the information to thePhysical Layer who will send the random access burst. The Physical Layer upon sendingthe random access burst will inform the Data Link Layer which burst the request was sentin, the Data Link Layer will pass this information up to Layer 3, again using primitives.

Note:

Primitives are the messages which are passed between each of the OSI layers to enablethem to communicate with each other.




3–23

Format B-bis

SYS01_3_13


1

Information Field

N201

ISSUE 12 REVISION 0Frame Delimitation



3–24

Frame Delimitation

(Start and end of frame and/or information elements)

Frame delimitation is provided by the Physical Layer (Layer 1). See TS GSM 04.04.

Address Field

The address field may contain a variable number of octets. However, for applications oncontrol channels the field consists of only one octet. The address field identifies the SAPfor which a command frame is intended (note: the type of control channel i.e. BCCH,SDCCH etc, is determined using the primitives) and the SAP transmitting a responseframe.

EA – Address Field Extension Bit

If this field is coded with a “0” then there is more than one octet to the address field, a “1”in the field indicates that this is the final octet in the address field.

C/R – Command/Response Field Bit

The C/R bit identifies a frame as either a command or response. The MS shall sendcommands with the C/R bit set to “0” and responds with the C/R bit set to “1”.

The BSS shall do opposite; that is commands are sent with the C/R bit set to “1” andresponse with the C/R bit set to “0”.

ISSUE 12 REVISION 0 Address Field



3–25

Address Field

SYS01_3_14


Spare LPD SAPI C/R EA=1 1

Type Direction C/R value

Command BS Side to MS Side 1

Command MS Side to BS Side 0

Response BS Side to MS Side 0

Response MS Side to BS Side 1

BSS and MS combinations:

ISSUE 12 REVISION 0Address Field



3–26

SAPI – ServiceAccess PointIdentifier

The SAPI identifies a point at which Data Link Layer services are provided by the DataLink Layer to the Layer 3 entity.

The SAPI allows 8 service access points to be specified, initially only two have beenspecified the remainder are reserved for future use.

LPD – LinkProtocolDiscriminator

The Link Protocol Discriminator can take two values only with all other values reserved:

“00” Corresponds to all other available data link protocols apart from SMSCB(These are defined within TS GSM 04.06).

“01” Correspond to the data link protocol used for SMSCB.(These are defined within TS GSM 04.12).

The Link Protocol Discriminator is used for discriminating between the GSM Protocol andother protocols (national or manufacturer – specific).

ISSUE 12 REVISION 0 Address Field



3–27

Address Field

SAPI – Service Access Point Identifier:

SYS01_3_15

SAPI Value Related Entity

0 Call Control SignallingMobility Management SignallingSupplementary Services SignallingRadio Resource Management Signalling

3 Short Message Service

All Others Reserved for future use

LPD Link Protocol Discriminator:

“00” All other Data Link Protocols apart from SMSCB.

“01” Data Link Protocol used for SMSCB.

ISSUE 12 REVISION 0Control Field Frame Formats



3–28

Control Field Frame FormatsThe control field identifies the type of frame and whether it will be either be a commandor a response. The control field will contain receive and send sequence numbers, whereapplicable.

Three types of control field formats are specified:

� Information format – numbered information transfer between Layer 3 entities.

� Supervisory format – performs data link supervisory functions, such asacknowledgement of I frames, request retransmission of I frames, and request atemporary suspension of I frames.

� Unnumbered format – Additional unnumbered information transfer and controlfunctions (this format does not contain sequence numbers)

P/F – Poll/Finalbit

The Poll/Final bit serves a function in both command and response frames. In commandframes the P/F bit is referred to ass the “P” bit and in response frames the P/F bit isreferred to as “F”.

The “P” bit set to a “1” is used by the Data Link Layer entity to create a response fromthe peer Data Link Layer entity. The “F” bit set to “1” is used by a Data Link Layer peerentity to indicate the response frame transmitted as a result of a soliciting command.

N(S) – Send Sequence Number

Only I frames contain N(S), the send sequence number of the transmitted I frames.

N(R) – Receive Sequence Number

All I and S frames contain N(R), this is the expected send sequence number of the nextreceived I frame.

N(R) indicates that the Data Link Layer entity transmitting N(R) has correctly received allI frames numbered up to and including N(R)–1.

ISSUE 12 REVISION 0 Control Field Frame Formats



3–29

Control Field Frame Formats

SYS01_3_16

Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1

I Frame N(R) P N(S) 0

S Frame N(R) P/F S S 0 1

U Frame U U U P/F U U 1 1




3–30

S – SupervisoryFunction Bit(s)

The following supervisory commands/responses have been defined using bit 3 and 4 ofthe control field.

RR – Receiver Ready

The RR frame is used by the Data Link Layer entity to indicate:

� it is ready to receive I frames

� acknowledge previously received I frames up to and including N(R)–1

� clear a busy condition which was previously indicated by a RNR frame sent by thesame data link entity.

In addition an RR frame with the “P” bit set to a “1” may be used by the Data Link Layerentity to ask for the status of its peer Data Link Layer entity.

No information field is permitted in the RR frame.

REJ – Reject Command/response

The REJ command is used by a Data Link Layer entity to request retransmission of Iframes starting at N(R). The value 0f N(R) in the REJ frame acknowledges I framesnumbered up to and including N(R)–1.

In addition an REJ frame with the “P” bit set to a “1” may be used by the Data Link Layerentity to ask for the status of its peer Data Link Layer entity.

No information field is permitted in the REJ frame.

RNR – Receiver Not Ready

The RNR frame shall be used to by a Data Link Layer entity to indicate a busy condition,that is temporary inability to accept additional incoming I frames. The value of N(R) in theRNR frame acknowledges I frames numbered up to and including N(R)–1.

In addition an RNR frame with the “P” bit set to a “1” may be used by the Data Link Layerentity to ask for the status of its peer Data Link Layer entity.

No information field is permitted in the RNR frame.




3–31

Supervisory Function Bits

SYS01_3_17

Bit 4 Bit 3 Command/Response0 0 RR – Receiver Ready0 1 RNR – Receiver Not Ready1 0 REJ – Receiver Reject




3–32

U – UnnumberedFunction Bit

SABM – Set Asynchronous Balanced Mode Command

The SABM is used to place the addressed user side or network side into the modulo 8multiple frame acknowledged operation (the ability to transfer I frames).

If the SABM is in the MS to BSS direction in order to establish a SAPI=0 data link (forcontention resolution after having transmitted a random access frame on the RACH),Layer 3 will indicate whether an information field is to be included.

Note:

SABM frames cannot contain Layer 3 frames which have to be segmented.

A Data Link Layer entity confirms acceptance of a SABM command by transmission atthe first opportunity of a UA response. Upon acceptance all variables for the for nexttransmitted I frame, next received I frame and acknowledged I frames are set to “0”.

Any currently unacknowledged I frames, remain unacknowledged and shall be discarded,it is the responsibility of the higher layers to recover form the loss of this information.

DISC – Disconnect Command

The DISC unnumbered command is transmitted to terminate the multiple frameoperation. Prior to actioning this command the Data Link Layer receiving the DISCcommand confirms the acceptance of the DISC command by the transmission of a UAresponse.

The Data Link Layer entity sending the DISC command terminates multiple frameoperation when it receives the acknowledging UA or DM response.




3–33

U – Frames

SYS01_3_18

Command Response 8 7 6 5 4 3 2 1

SABM 0 0 1 P 1 1 1 1

DM 0 0 0 F 1 1 1 1

UI 0 0 0 P 0 0 1 1

DISC 0 1 0 P 0 0 1 1

UA 0 1 1 F 0 0 1 1




3–34

U – UnnumberedFunction Bit

UI – Unnumbered Information Command

When a Data Link Layer requests unacknowledged Information transfer, the UIunnumbered command shall be used to send information to its peer without affectingdata link variables (number of acknowledged I frame, next I frame to betransmitted/received).

UI frames do not carry a sequence number. Therefore a UI frame may be lost withoutnotification to the Layer 3 entity if a Data Link Layer exception occurs during transmissionof the command.

UA – Unnumbered Acknowledgement Response

The UA frame is used by a Data Link Layer to acknowledge the receipt and acceptanceof a SABM or DISC commands. The SABM or DISC commands are not actioned untilthe UA response is transmitted.

If an information field is present in the received SABM then the UA response shallcontain the same information field as received in the SABM .

The transmission of a UA frame indicates the clearance of a busy condition that wasreported earlier by the transmission of an RNR frame by the same Data Link Layer.

DM – Disconnect Mode Response

The DM unnumbered response is used by a Data Link Layer to report to its peer that theData Link Layer is in a state such that multiple frame operation cannot be performed.

A Data Link Layer shall transmit a DM response to any valid command it received whichit cannot action.

No information field is present in the DM response.




3–35

U – Frames

SYS01_3_19

Command Response 8 7 6 5 4 3 2 1

SABM 0 0 1 P/F 1 1 1 1

DM 0 0 0 F 1 1 1 1

UI 0 0 0 P 0 0 1 1

DISC 0 1 0 P 0 0 1 1

UA 0 1 1 F 0 0 1 1




3–36

Length Indicator

EL – Extension Bit

A “1” in the EL field indicates that this is the final octet of the length indicator field, a “0”indicates that the length indicator field is extended.

M– More Data Bits

The “M” data bit is used to indicate segmentation of Layer 3 message data units on DataLink Layer frames. Only I frames shall contain segmented Layer 3 information.

When the “M” bit is set to “1”, it indicates that the information field of the frame containsonly a segment of the Layer 3 message unit.

The “M” bit set to “0” indicates

� that the information field contains a complete Layer 3 message unit provided thatthe “M” bit of the previous frame was set to “0”

� that the information frame contains the last segment of the Layer 3 message unit ifthe “M” bit of the previous frame was set to “1”.

Note:

When the “M” bit is set to “1” the information field shall contain the maximum number ofoctets, N201 that an information frame can contain.

Frames may contain fill bits, octets containing fill bits shall take the binary value“00101011” when sent by the network. Octets containing fill bits shall take the binaryvalue “00101011” or “11111111” when sent by the MS.

Length – length field bits

The length field bits shall be any value from 0–N201 inclusive.

A length= 0 shall be used in frames not containing an information field.




3–37

Length Indicator

SYS01_3_20

Key:

EL = Extension BitM = More Data BitsLength = length field bits


Length M EL=1

ISSUE 12 REVISION 0List of System Parameters (LAPDm)



3–38

List of System Parameters (LAPDm)

Timer T200

T200 is set such that it is possible to receive an acknowledgement from the peer entity ofthe transmitting Data Link Layer, taking into account all processing and propagationdelays.

If T200 Expires then the frame transmitted which started T200 is retransmitted and thecounter N200 is incremented.

Counter N200

N200 is the maximum number of transactions between the Data Link Layers of anunacknowledged frame. For SAPI=0 and SAPI=3 the value of N200 shall be set = 5.

In the state Timer Recovery the value of N200 shall be:

5 for use on SACCH

23 for use on SDCCH

34 for use on FACCH/full rate

29 for use on FACCH/half rate

(Timer recovery is defined in TS GSM 04.06)

Maximum Number of outstanding I frames (k)

The maximum number of sequentially numbered I frames that may be outstanding (thatis unacknowledged) at any given time for SAPI=0 and SAPI=3 the value shall be k=1.

Maximum number of Octets in an I, UI SABM and UA frame informationfield (N201)

The maximum number of octets in an information field (N201):

� for the SACCH: N201=18

� for the FACCH and SDCCH: N201=20

� for the BCCH, AGCH + PGH: N201=23

ISSUE 12 REVISION 0 List of System Parameters (LAPDm)



3–39

System Parameters

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3–40


Introduction

The Signalling Layer 3 comprises of the following groups of signalling functions:

� Call Control (CC)

� Short Message Service Support (SMS)

� Supplementary Services Support (SS)

� Mobility Management (MM)

� Radio Resource Management (RR)

These functional groups are realised by separate protocol control entities.

Both RRM and MM have the task to route the messages according to the ProtocolDiscriminator (PD) and the Transaction Identifier (TI) which are part of the messageheader.

Services provided by Signalling Layer 3 at the MS side

The different classes of services provided by the Signalling Layer 3 at the MS side areaccessible at the following Service Access Points.

� Registration Services at the MM REG SAP.

� CC services for normal and emergency calls including call related SupplementaryServices at the MNCC–SAP.

� Short Message Services support services at the MN SMS–SAP.

� Call Independent Supplementary services, support services at the MNSS–SAP.

The registration services (location – updating IMSI attach/detach) are provided at theservice access point MM REG–SAP. These services are provided by and can be directlyaccessed at the MM sub-layer.




3–41

Layer 3 Signalling Model

SYS01_3_22

CALLCONTROL

(CC)

SUPPSERVICESUPPORT

(SS)

SHORTMESSAGESERVICE

(SMS)

MOBILITY MANAGEMENT(MM)

MM REG–SAP

TI TI

SAPI=0 SAPI=3

RR RR

TIMM CC SS SMS

RACH BCCH AGCH+PGH

SDCCH SACCH FACCH SDCCH SACCH

CONNECTION MANAGEMENT

MNCC–SAP MNSS–SAP MNSMS–SAP

MM CC–SAP

MMSS–SAP

MMSMS–SAP

PD

RADIO RESOURCES(RR)

PD

ISSUE 12 REVISION 0Radio Resource Management Sub-layer



3–42

Radio Resource Management Sub-layerThe sub-layer is responsible for:

� The management of the frequency spectrum

� The systems reactions to the changing radio environment

� The maintenance of a clear channel between the Public Land Mobile Network andthe Mobile Subscriber

These responsibilities will include, channel assignment, power level control, timealignment and handovers.

The Radio Resource sub-layer handles all the procedures necessary to establish,maintain and release dedicated radio connections.

ISSUE 12 REVISION 0 Radio Resource Management Sub-layer



3–43

Radio Resource Sub-layer:

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ISSUE 12 REVISION 0Mobility Management Sub-layer



3–44

Mobility Management Sub-layerThe Mobility Management Sub-layer has to deal with all the effects of handling a MobileSubscriber that is not directly related to radio functions.

These functions will include all tasks relevant to authorisation of a particular MobileSubscriber for connection to the network.

These tasks will include:

� Support a user mobility, registration and management of mobility data.

� Checking the user and the equipment identity.

� Checking if the user is allowed to use the services and what kind of extra servicesare allowed.

� Support of user confidentiality.

� Provision of user security.

� Provision of a Mobility Management connection, based on an existing RadioResource connection to the Connection Management sub-layer

ISSUE 12 REVISION 0 Mobility Management Sub-layer



3–45

Mobility Management Sub-layer:

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ISSUE 12 REVISION 0Connection Management Sub-layer



3–46

Connection Management Sub-layerThe Connection Management sub-layer is composed of:

� Call Control – GSM 04.08

� Supplementary Service Support – GSM 04.11

� Short Message Service Support – GSM 04.10

The sub-layer itself manages all the functions necessary for circuit-switched call controlwithin the GSM Public Land Mobile Network. These functions are provided by the CallControl entity within the sub-layer, with the other entities providing SupplementaryServices and Short Message Services.

ISSUE 12 REVISION 0 Connection Management Sub-layer



3–47

Connection Management Sub-layer

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ISSUE 12 REVISION 0Layer 3 – Frame Structure



3–48

Layer 3 – Frame StructureThe Layer 3 information elements are defined in TS GSM 04.08. Every message, withthe exception of the messages sent on the BCCH, downlink CCCH, SCH, RACH, andHANDOVER ACCESS message, is a standard Layer 3 message as defined in TS GSM04.07.

The standard Layer 3 message consists of:

� Protocol Discriminator (PD).

� Transaction Identifier (TI), or Skip Indicator.

� Message Type.

Other information elements as required.

ISSUE 12 REVISION 0 Layer 3 – Frame Structure



3–49

Layer 3 Header

SYS01_3_26


Transaction Identifieror Skip Indicator

Protocol Discriminator

Message TypeOther information elements as required

ISSUE 12 REVISION 0Protocol Discriminator/Skip Indicator



3–50

Protocol Discriminator/Skip IndicatorBits 1 to 4 of the first octet of a standard L3 message contain the Protocol Discriminator(PD) information element. The PD identifies the L3 protocol to which the standard Layer3 message belongs. The correspondence between L3 protocols and PDs is one-to-one.

The PD can take the following values:

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If the network receives a standard L3 message with a protocol discriminator differentfrom those specified above the network may ignore the message or initiate the channelrelease procedure.

If the mobile station receives a standard L3 message with a protocol discriminatordifferent from those specified above, the mobile station shall ignore the message.

Skip IndicatorBits 5 to 8 of the first octet of every Radio Resource management message and MobilityManagement message contains the skip indicator. A message received with skipindicator different from 0000 shall be ignored. A message received with skip indicatorencoded as 0000 shall not be ignored (unless it is ignored for other reasons). A protocolentity sending a Radio Resource Management message or a Mobility Managementmessage shall encode the skip indicator as 0000.

ISSUE 12 REVISION 0 Skip Indicator



3–51

Layer 3 Message Structure

SYS01_3_27

IE TYPE PD

OCTET 1

bits

reserved for tests procedures described in TSGSM 11.10

TI or SkipIndicator

4 3 2 1

x x x x

4 3 2 1

call control; call related SS messages0 0 1 1mobility management messages0 1 0 1radio resources management messages0 1 1 0SMS messages1 0 0 1non call related SS messages1 0 1 1

1 1 1 1

ISSUE 12 REVISION 0Transaction Identifier



3–52

Transaction IdentifierThe Transaction Identifier (TI) is a pointer with a length of four bits. It is used todistinguish between (possible) multiple parallel Connection Management connections andbetween the various transactions over these simultaneous Connection Managementconnections.

Bits 5 to 8 of octet 1 of a standard L3 message may contain the Transaction Identifier(TI) IE.

The TI IE is coded as shown opposite. It is composed of the TI value and the TI flag.

The TI value and the TI flag occupy bits 5–7 and bit 8 of the first octet respectively.

TI values are assigned by the side of the interface initiating a transaction. At thebeginning of a transaction a free TI value (i.e. a value not yet used for the given PD andwith the given originator) is chosen and assigned to this transaction. It then remainsfixed for the life time of the transaction. After a transaction ends, the associated TI valueis free and may be reassigned to a later transaction.

Two identical transaction identifier values may be used when each value pertains to atransaction originated at opposite ends of the interface. In this case the TI flag shouldavoid ambiguity. The transaction identifier flag can take the values “0” or “1”. The TI flagis used to identify which end of the radio interface originated a TI. The origination sidealways sets the TI flag to “0”. The destination side always sets the TI flag to a “1”.

Hence the TI flag identifies who allocated the TI value for this transaction and the onlypurpose of the TI flag is to resolve simultaneous attempts to allocate the same TI value.

TI flag (octet 1)Bit 8

0 The message is sent from the side that originates the TI. 1st1 The message is sent to the side that originates the TI. 2nd

TI value (octet 1)

7 6 50 0 0 TI value 00 0 1 – – 10 1 0 – – 20 1 1 – – 31 0 0 – – 41 0 1 – – 51 1 0 – – 61 1 1 Reserved for future extension

Note:

IE – Information Element

ISSUE 12 REVISION 0 Transaction Identifier



3–53


SYS01_3_28

IE TYPE PD

OCTET 1

TI VALUE

TI or SkipIndicator

TIFLAG

8 7 6 5

IE – Information ElementsTI – Transaction IdentifierPD – Protocol Discriminator

Key:

ISSUE 12 REVISION 0Message Type



3–54

Message TypeThe message type element defined in the transparent L3 IEs is defined in TS GSM04.08. The message defines if the message is for Radio Resource Management,Mobility Management or Connection Management.

Bit 8 is reserved for possible future use as an extension bit.

The Mobility Management messages and the Connection Management messages usingSAPI= 0 sent from the Mobile Station to the network will specify the send sequencenumber N(SD) in bit 7. At the time when such a message is designated for transmissionthe value N(SD) for the message to be transferred is not equal to the value of the sendstate variable.

In all other standard Layer 3 messages bit 7 is set to 0 by the sending side, the receivingside shall ignore such messages if bit 7 is set to 1.

For a complete list of the different types of message elements refer to TS GSM 04.08.

Note the information elements are defined in TS GSM 04.08.

ISSUE 12 REVISION 0 Message Type



3–55


SYS01_3_29

RESERVED

MESSAGE TYPE (RR)

MESSAGE TYPE (MM, CC)

BIT 8 BIT 7

1 OCTET

INFORMAIONELEMENTS

TRANSACTIONOR SKIP

IDENTIFIER

PROTOCOLDISCRIMINATOR

TYPE

ISSUE 12 REVISION 0Message Sequence Scenarios



3–56

Message Sequence ScenariosThe best way of understanding the interface procedures is to examine the commonmessage sequence scenarios which highlight the flow of messages between the MobileSubscriber and the BTS.

The main message sequence scenarios are shown:

� Mobile Originating Call Establishment.

� Mobile Terminating Call Establishment.

� Location Updating.

� Call Clearing

ISSUE 12 REVISION 0 Message Sequence Scenarios



3–57

Message Sequence Scenarios

� ��

� ��

� ��

� ��




3–58

MobileOriginating CallEstablishment

The mobile station initiates the call by transmitting a Channel Request. The Network willrespond with an immediate assignment message informing the Mobile Station on whichSDCCH the rest of the call set up procedure will take place. The Mobile Stationestablishes contact on the SDCCH by transmitting a SABM LAPDm frame containing theDTAP message “CM Service Request”.

However, the Network could also respond with an assignment reject message.

The Network may then initiate authentication and may start the ciphering mode setting.

After sending the Ciphering Mode Complete message, the Mobile Station initiates the callestablishment by sending the setup message to the network. The Network answers witha Call Proceeding message.




3–59

Mobile Originating Call Establishment

SYS01_3_31

Access Burst(Channel Request)

Immediate Assignment

CM Service Request

Authentication Request

Authentication Response

Cipher Mode Command

Cipher Mode Complete

Set up

Call Proceeding

Assignment Command

SABM on FACCH

Assignment Complete

Alerting

Connect

Connect Acknowledge

Mobile Station Network

RR

RR

SABM MM

UAMM

MM

RR

RR

CC

CC

RR

UA RR

CC

CC

CC

Authentication

Ciphering ModeSetting

CallInitialization

Assignment of aTraffic Channel

User Alerting

Call Accepted

Key:

RR – Radio ResourcesMM – Mobility ManagementCC – Call Control




3–60

MobileTerminating CallEstablishment

Mobile terminating call establishment is initiated by the Network sending a paging requestmessage.

Upon receiving this message the Mobile Station initiates the immediate assignmentprocedure and responds to the Network by sending the Paging Response messagewithin a Layer 2 SABM frame. The Network returns a Layer 2 UA frame containing thesame information field as was sent in the SABM frame.

Authentication and ciphering are treated by the Network in the same way as defined forthe Mobile originating call establishment. After ciphering has been started, the Networksends a setup message to the Mobile Station. The capability of the Mobile Station (atthat time) to accept the call is confirmed when the mobile station returns a call confirmedmessage to the Network.




3–61

Mobile Terminating Call Establishment

SYS01_3_32

Paging Request

Channel Request


Paging Response



Cipher Mode Command


Set up

Call Confirmed

Assignment Command

Assignment Complete

Alerting

Connect

Connect Acknowledge


Authentication

Ciphering ModeSetting

CallInitialization

Assignment of aTraffic Channel

User AlertingInformation

Call Accepted




3–62

LocationUpdating

The updating procedure is always initiated by the Mobile Station for example: when theMobile Station finds itself in a different location area from the one in which it wasregistered before.

The location updating procedure is a general procedure which is used for the followingpurposes:

� Normal location updating

� Periodic updating

� IMSI attach

Normal location updating procedure is used to update the registration of the actuallocation area of a Mobile Station in the Network.

Periodic updating may be used to notify the availability of the Mobile Station to theNetwork.

The IMSI attach procedure is used to indicate the IMSI as active in the Network.

The Network may decide whether to allocate a new TMSI during location updating, thisoption is reflected in the example.




3–63

Location Updating

SYS01_3_33

Channel Request


Location Updating Request



Cipher Mode Command


Location Updating Accept

TMSI Reallocation Complete

UA or DM


Channel Release

DISC




3–64

Call Clearing

Initiated by the Network:

The Network initiates the clearing of a call by sending a Disconnect message to theMobile Station.

Upon receiving the Disconnect message from the Network the Mobile Station sends arelease message to the Network.

Upon receiving the release message from the Mobile Station, the Network sendsRelease Complete to the Mobile Station and if the traffic channel is no longer neededperforms the channel release procedure.

Upon receiving the Release Complete message and if the cleared call was the lastactivity on the traffic channel, the Mobile Station waits for the release of the channelwhich is always initialised by the Network.

Initiated by the Mobile Station:

The Mobile Station initiates the clearing of a call by sending a Disconnect message to theNetwork.

Upon receiving the Disconnect message from the Mobile Station the Network sends aRelease Message to the Mobile Station.

Upon receiving the Release Message from the network, the Mobile Station sends aRelease Complete to the Network, which, if the traffic channel is no longer neededperforms the channel release procedure.




3–65

Call Clearing Initiated by the Network

SYS01_3_34


Disconnect

Release

Release Complete

Channel Release

Call Clearing

Call Clearing Initiated by the Mobile Station

SYS01_3_35


Disconnect

Release

Release Complete

Channel Release

Call Clearing

ISSUE 12 REVISION 0Message Flow Scenarios



3–66

Message Flow ScenariosA practical session to show message flow scenarios across the Um interface will now beset up by your instructor.

The practical demonstrations will include:

� Call setup

� Handover

� Call clear down

� Paging response

ISSUE 12 REVISION 0 Message Flow Scenarios



3–67

ISSUE 12 REVISION 0Exercise



3–68

ExerciseThe purpose of this exercise is to construct the Layer 2 and Layer 3 information elementsfor a MS to network CM Service Request using the SABM.

The MS is to be identified by its TMSI.

No Ciphering Key Sequence Number is available.

The MS is a phase 1 mobile.

A5/1 is available, A5/2 and A5/3 are not available.

The MS is power class 2, GSM 900.

Pseudo synchronisation capability is not present.

Short message capability not present.

The MS does not support the extension band G1 (extended GSM frequency range)

No additional MS capability information is present.

Use the Table opposite for your answer.

Supplementary Screen Indicator is 00

Hint:

You will need to refer to TS GSM 04.07, 04.08 and 04.80 for your answers.

ISSUE 12 REVISION 0 Exercise



3–69

Exercise

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ISSUE 12 REVISION 0Exercise



3–70



i

Chapter 4

Common Bearer [2 Mbit/s Links]

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 4Common Bearer [2 Mbit/s Links] i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Common Bearer 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction 4–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Links – Common Channel Signalling 4–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Transmission Code 4–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High Density Bipolar 3 (HDB3) 4–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time Division Multiplexing (TDM) 4–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rx Buffer/Slip Loss 4–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slip Loss Counters 4–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Frame Alignment Procedures 4–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N Bit 4–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Synchronization 4–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sync Loss Counters 4–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sync Timers 4–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GCLK Synchronization 4–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Remote Alarm 4–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Remote Loss Alarms 4–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bit Error Rate (BER) 4–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BER Timers 4–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BER Counters 4–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclic Redundancy Checking (CRC) 4–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclic Redundancy Check 4–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Database Command 4–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

High Bit-Rate Digital Subscriber Line (HDSL) 4–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

ISSUE 12 REVISION 0 Common Bearer



4–1

Common Bearer

Objectives


� Identify the connectivity, using the 2 Mbit/s links.

� State the TDM frame format and alignment procedures.

� Identify the uses of CRC-4.

� Understand the implementation of GCLK synchronization.

ISSUE 12 REVISION 0Introduction



4–2

IntroductionAs previously mentioned the GSM system entities are connected using a common bearersystem – this being the 2 Mbit/s link.

For 75ohm cable termination we use T43 Interconnect Boards (T43IB) and for 120ohmtwisted pair termination we use Balanced Line Interconnect Boards (BIB).

Within the BSU two digital boards are used to interface the 2 Mbit/s links to the TDMhighway.

The first board is the Multiple Serial Interface board (MSI), this board can terminate up totwo 2 Mbit/s links. The second board is the Transcoder Board (XCDR) which onlyterminates one 2 Mbit/s link but it also has the ability to perform the GSM definedtranscoding function on up to 30 channels of the 32 channels on the 2 Mbit/s link.

ISSUE 12 REVISION 0 Introduction



4–3

Common Bearer (2 Mbit/s Link)

SYS01_4_2

PSTN MSC MSC

BSC

CBC RXCDR OMC–R

BTS

BTS

BTS

BTS

BTS BTS

BTS

BTS

ISSUE 12 REVISION 0Signalling Links – Common Channel Signalling



4–4

Signalling Links – Common Channel SignallingThe signalling links on the GSM terrestrial interfaces utilize common channel signalling.This means the signalling link is kept separate from the traffic. As the signalling is keptseparate from the traffic, it does not have to follow the same physical route as the traffic.

Using common channel signalling allows a signalling message to be transmittedwhenever a slot becomes available, i.e. there is no dedicated time reserved for aparticular traffic circuit to transmit its signalling data.

The advantages of common channel signalling are:

� Signalling possible at any time

� Signalling repertoire is increased

� Signalling protocols are flexible

� Signalling can include processor and network management functions

� Signalling is more economical

� Signalling speed is increased

The terrestrial signalling links used in the Motorola GSM system are all 64 kbit/s timeslotson the common bearer (2 Mbit/s link). It is normal to have both traffic and signallingusing a single 2 Mbit/s link for efficient use of the 2 Mbit/s link.

ISSUE 12 REVISION 0 Signalling Links – Common Channel Signalling



4–5

Signalling Links – Common Channel Signalling

SYS01_4_3

ControlProcessor

Signalling(64 Kbps Timeslot)

ControlProcessor

2 Mbit/s Link

TrafficChannels BSSMSC

ISSUE 12 REVISION 0Transmission Code



4–6

Transmission Code

High DensityBipolar 3 (HDB3)

The transmission of a digital bit stream along a line has two main problems, the first isthe introduction of a DC component. This has the effect of causingcross-talk/interference with other cable pairs. To overcome this we use a code calledalternate mark inversion. In the diagram opposite a mark is normally a positive voltage.(In this case every other positive mark is inverted to a negative mark. This prevents thebuild up of a DC level on a copper wire, therefore making it easier for the receivingequipment to distinguish the difference between a ‘1’ and a ‘0’.)

The second problem is that both ends of a digital link are required to be synchronised.This can be achieved by the transmission of a clock signal, but this will require anadditional cable pair, however, it can also be achieved by using a transmission code.

HDB3 is a type of transmission code which ensures that sufficient marks (1’s) are sent toline so that the receiver can use the data stream to extract a clock, thus saving on thenumber of cable pairs required.

HDB3 checks the data stream for the number of consecutive 0s. If this number reaches4, the transmitter will alter this to a mark (1). To enable the receiver to determine that thetransmitter has carried out this alteration, the transmitted mark is sent in the samepolarity as the last mark, called a violation. The receiver recognising this violation markreinserts the 0.

If the data stream has a further consecutive number of 0s, then the transmitter will inserttwo violation bits, to indicate that this is the second count of 0s. These two violation bitsare in the same polarity but the opposite from the last violation mark.

This transmission code ensures that even with data of continuous 0s, there is a 50% dutycycle rate, thus the receiver can still extract the clock signal for synchronisation.

ISSUE 12 REVISION 0 Transmission Code



4–7

High Density Bipolar 3 (HDB3)

SYS01_4_4

+ve

0 v

–ve

Signal Data

HDB3 Code

+ve

0 v

–ve

Vm

Vm Vm

Vm

Vm = Violation mark inserted

**

Balancing bits to ensure consecutive violations areopposite polarity and hence no dc component is introducedand the receiver can perform clock extraction.

TRANSMIT DATA STREAM

Data: 0 0001 0000000000000 1 1 01

*

Key:




4–8

Time DivisionMultiplexing(TDM)

When using time division multiplexing (TDM) a number of different channels can betransmitted on a single line by allowing each channel in turn to transmit to the line for acertain period of time. This period of allocated time is called a timeslot.

The channels are sampled in turn and time division multiplexed before being transmitted,each channel (timeslot) being represented by an 8 bit code.

The system bit rate (the speed of transmission) can be calculated as follows:

Bit Rate = Sampling Frequency x Number of Bits per sample x Number of timeslots (Channels)

8000 x 8 x 32 = 2.048 Mbit/s. Usually referred to as 2 Mbit/s systems.

Timeslot (TS) 0 does not carry traffic. Timeslot 0 in each frame is used for framealignment purposes.




4–9

TDM Frame Format

SYS01_4_5

0 1 31

Frame 0 – 125��sec

(256 bits)Timeslot

AlignmentTimeslot

8 bits

Traffic Timeslots




4–10

Rx Buffer/SlipLoss

The incoming bit stream is stored in a receive buffer which can accommodate twocomplete TDM frames (512 bits). The alignment procedure uses a sliding window tolocate the frame alignment word (FAW), which indicates the start of the frame. Thereceiver knows how many bits there are in a single frame (256 bits) and therefore shouldbe able to locate the complete frame in the buffer store.

Slip loss is when either the frame alignment word or part of the frame structure can notbe located within the buffer storage area. When this occurs the receiver buffer isrequired to be reset and consequently the loss of at least one frame.

Slip LossCounters

These are database parameters and are equipped for every site, using thechange_element command.

Slip_loss_daily Number of slip errors in 24 hour period. (Minor alarm generated)

Slip_loss_hourly Number of slip errors in one hour period.(Major alarm generated)

Slip loss_oos Number of slip errors before the link is taken out of service, within a 24 hour period.(Critical alarm generated)

Slip_loss_restore Minimum time period of “error-free” before link is restored to service.(Clear indication generated)

An occurrence of slip loss causes the hourly, daily and out-of-service (OOS) countersto be incremented.




4–11

Receive Buffer

SYS01_4_6

Buffer Storage Area(512 bits)

128 bits128 bits

TS0

FRAME 256 bits

SLIDING WINDOW

8 bits

Slip Loss

SYS01_4_7

Buffer Storage Area

300 bits

SLIDING WINDOW

TS0

8 bits

ISSUE 12 REVISION 0Frame Alignment Procedures



4–12

Frame Alignment ProceduresTimeslot (TS) 0 contains one of two fixed bit patterns so that the ‘far end’ receive buffercan discriminate between different frames.

One of the bit patterns is inserted into TS 0 of frame 0 and will be inserted into TS 0 ofeach even numbered frames. The other bit pattern will be inserted into each oddnumbered frame.

The two bit patterns are sent alternately and are known as the Frame Alignment Word(FAW) and Frame Data Word (FDW).

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It is possible to set an extra remote alarm bit, the n bit. The bit which is used for thispurpose is bit 4 of the frame data word. The actual use of this bit is specified by thecustomer but the bit must be enabled using the modify_value command. Again this bitcan be enabled for all sites using the ‘all’ location index.

ISSUE 12 REVISION 0 Frame Alignment Procedures



4–13

Frame Structure

SYS01_4_8

TS OFDW

TS OFAW

TS OFDW

TS OFAW

TS OFDW

TS OFAW

TS OFDW

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TS OFDW

TS OFAW

TS OFDW

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TS OFDW TS 1 TS 31

FAW = Frame Alignment WordFDW = Frame Data Word

TS OFAW TS 1 TS 31

Key:

ISSUE 12 REVISION 0Synchronization



4–14

SynchronizationSynchronization is achieved when the sliding window detects the Frame Alignment Word(FAW) and sets the frame in the middle of the receiver buffer. Continued synchronizationis dependant upon the window detecting the FAW and Frame Data Word (FDW) at 256bit intervals.

Note: The synchronization is dependant on BIT 2 of the FAW/FDW toggling.

Synchronization loss occurs when 3 consecutive frame alignment signals (FAW/FDW)are received with an error. If this occurs then link alignment will recommence.

Sync LossCounters

These are database parameters, which are equipped at every site and use the “change_element ” command.

��

��

��

��

��

��

Sync Timers

sync_time–oos Immediately a synchronization loss occurs the sync_time_oos is started, this sets the maximum time the error can exist before the link is taken out of service.At the same time a condition is sent to the distance end.

sync_time_restore sets the minimum time after restoring synchronization, the link has to be free of sync errors before restoring to service.

ISSUE 12 REVISION 0 Synchronization



4–15

Synchronization Timers

SYS01_4_9

Sync Error

sync_time_oos = started

ExpiresLink = Unlock/Disbaled)

Sync restored

sync_time_restore = started(Link = Unlock/Enabled)

sync_time_restore expires withoutany sync_loss_errors(Link = Unlock/Busy)

Increment:Sync_loss_dailySync_loss_oosSync_loss_hourly

ISSUE 12 REVISION 0GCLK Synchronization



4–16

GCLK SynchronizationThe aim of the GCLK synchronization is to provide:

� RF carrier frequencies to within +/–0.05ppm

� Synchronization of E1 or T1 links to minimise

– Frame slips– On site calibrations

The network clock should be maintained at +/–0.01ppm of 2,048 MHz E1, or 1.544 MHzT1. To maintain the link the clock or data should have no breaks greater than 80�secs,this would cause loss of synch.

The synchronization circuit resides on the GCLK board (used in BSC, BTS & RXCDR).The feature will operate with BTS’s in star, daisy chain and loop topologies.

The network can be run from one high quality, high accuracy clock. There is still theability to have two GCLK’s at each Network element (BTS, RXCDR or BSC).

Once synchronization to a “known good clock source” the Network Elements can selfcalibrate to this clock (calibration is not eliminated but its occurrence is reduced.

ISSUE 12 REVISION 0 GCLK Synchronization



4–17

GCLK Synchronization

BTS

GCLK

BTS

GCLK

SYS01_4_10

NetworkClock

BTS

GCLK

Public SwitchedTelephone Network

(PSTN)

LinksOR T1E1

BSC

GCLK

RXCDR

GCLK

MSC

BTS

GCLK

BTS

GCLK2 Mbs–1




4–18

GCLK SynchronizationIn order to phase lock, a GCLK must have a span assigned as a reference source.Parameters in the database can be used to specify priorities applicable to each span at asite. These priorities will be used to determine the order of selection of spans as areference source.

Should the chosen span subsequently go out-of-service a GCLK reference fail alarm willbe initiated. A timer controls the time the system will wait before selecting another spanfor extraction. If the current span returns to synch before the timer expires then it willremain the clock extraction source.




4–19


SYS01_4_11

chg_element phase_lock_gclk <*> <site>

* 0 Disable phase locking

1 Enable phase locking

chg_element wait_for_reselection <*><site>

* 0–255 (seconds)

Default Value: 10




4–20

GCLK SynchronizationTo enable the GCLK to synchronize to an E1 or T1 a suitable source must exist. Thepriority for source selection is:

1. MMS in service.

2. Priority of MMS (database parameter)

3. Number of times the MMS has gone out-of-service (oos) in a given period

4. If priority and MMS oos are equal the order of selection of sources shall be on arotation basis.

The priority of each MMS can be individually set:

modify_value <site> mms_priority <*> mms <mms_id 1> <mms_id 2>

* 0–255 0– MMS will not be selected1– Lowest priority255– Highest priority

A count of the number of times the MMS goes oos is kept to enable the prioritizingalgorithm to function. A reset period is used to delimit the time for which an oos count isheld. At the end of each reset period the oos count is reset to zero and the count beginsagain.

chg_element clk_src_fail_reset_period <*> <site>

* 1–255 Hours

After initialization of the site the GCLK will attempt to synchronize to the chosen MMS,the time duration taken for this synchronization will vary depending on the hardwarerevision level of the card. If the synchronization has been maintained forphase_lock_duration the CA will declare the GCLK phase locked. The default valuefor this variable is 0 which indicates that there is no change from the minimum perioddefined for the revision level of the GCLK. The variable may be set on an MMS basis toaccount for different transmission media.

modify_value<site>phase_lock_duration <*> mms <mms_id 1> <mms_id 2>

* 0 – Default, GCLK revision level dependent, any MMS details ignored 1 – 3600 seconds MMS details used




4–21


SYS01_4_12

MMS Priority:

modify_value <site> mms_priority <*> mms <mms_id 1><mms_id 2>

* 0–255 0 – MMS will not be selected1 – Lowest priority255 – Highest priority

Time for which OOS count is held:

chg_element clk_src_fail_reset_period <*> <site>

* 1–255 Hours

Synchronization period maintained:

modify_value <site>phase_lock_duration <*> mms<mms_id 1> <mms_id 2>

* 0 – Default, GCLK revision level dependent, any mms details ignored

1 – 3600 seconds mms details used




4–22

Remote Alarm

When a synchronisation alarm occurs the sync_time_oos timer is started at the localend and remote flag alarm is set (bit 3 of the FDW). When the remote flag is detected thedistant end starts a timer (remote_time_oos ) and increments the counters,remote_loss_daily , remote_loss_hourly and remote_loss_oos .

The timer remote_time_oos sets the period in which a remote flag must be receivedbefore the link is taken out of service and passed back to layer 1 for link alignment.

If the link was taken out of service due to remote_time_oos then the link can only bereturned back to service when there have been no remote_loss alarms for the timespecified in timer remote_time_restore .

remote_time_oos

remote_time_restore

Remote LossAlarms

Two database parameters are used which indicate the number of remote_loss alarmsthat can occur in a given period (hourly/daily) before an alarm message is generated.

Note: these alarms can only be generated once during the given period, e.g. if the alarmcondition for the remote_loss_hourly was met in the first 10 minutes then an alarmmessage would be generated, no alarm messages could be generated after this initialone until the 1 hour period had elapsed and the remote_loss_hourly alarm was reset.

Another parameter is used to set an upper limit to the number of remote_loss alarmsthat we will allow in any one day before we take the link out of service,remote_loss_oos . If this parameter is met then an alarm is generated and the link ispassed back to layer 1 for link realignment.

If the link was taken out of service due to an remote_loss_oos then the link can only berestored back to service when there are no remote_loss alarms for a period of timedefined in remote_loss_restore .

remote_loss_hourly

remote_loss_daily

remote_loss_oos

remote_loss_restore




4–23

Remote Timers

SYS01_4_13

Distant Local

BIT 3 FDW SET (Remote Flag)





BIT 3 FDW NOT SET

BIT 3 FDW NOT SET

BIT 3 FDW NOT SET

remote_time_oos (STARTED)

Increments:REMOTE_LOSS_DAILYREMOTE_LOSS_HOURLYREMOTE_LOSS_OOS

remote_time_oos (EXPIRES)

DISABLE MMS

remote_time_restore (STARTED)

remote_time_restore (EXPIRES)

remote_time_restore (EXPIRES)

MMS in service MMS in service

SYNC ALARM

sync_time_oos (STARTED)

sync_time_oos (EXPIRES)

DISABLE MMS(SYNCHRONIZATION GAINED)

sync_time_restore (STARTED)

sync_time_restore (EXPIRES)




4–24

Bit Error Rate(BER)

After the link has achieved link alignment/synchronisation, it is checked for bit errors overa period of time, to ensure that this is below a pre-determined value. Typical BER rate10e–4 eg. 1 error every 10,000 bits.

Bit errors are constantly being checked against the known fixed bits in both the FrameAlignment Word and Frame Data Word (Bits 2–8 FAW/Bit 2 FDW). If any errors aredetected in these 8 bits (over two frames time periods) a counter will be incremented andshould the total errors over a particular time exceed the counters threshold then the linkwill be taken out of service.

BER Timers

These parameters form part of the firmware of the MSI/XCDR card and set themonitoring periods. The values may be changed using the modify value command.

ber_oos_mon_period The amount of time that an in-service MMS must be above a set BER rate before it is taken oos.

ber_restore_mon_period The amount of time an oos MMS must be below a set BER before it is put backin service.

BER Counters

These parameters are part of the database and are set using the “change_element ”command.

Ber_loss_daily Indicates the BER daily alarms.

Ber_loss_hourly Indicates the BER hourly alarms.




4–25

BER – Fixed Bits

SYS01_4_14

* 0 1 10 1 10

* 1 1 10 0* *_ _ _ _ _

Frames

Bit Error Rate = 10e–4 BER Timers: ber_oos_mon_periodber_restore_mon_period

BER Counters: ber_loss_dailyber_loss_hourly

8 Fixed Bits

Frame AlignmentWord

Frame Data Word

= Fixed Bit1




4–26

CyclicRedundancyChecking (CRC)

Where there is a need to provide additional protection and enhanced error monitoringcapacity, then Cyclic Redundancy Check–4 (CRC–4) procedure is used. All MSI/XCDRcards are fitted with this procedure but must be capable of interworking with equipmentwhich does not incorporate the CRC procedures, this being optional.

CRC–4 procedure utilises bit 1 of each frame, over a complete multiframe (16 frames).This multiframe is further divided into two sub-multiframes (0–7) (8–15) each with a blocksize of 2048 bits.

In those frames containing the Frame Alignment Word, bit 1 is used to transmit theCRC–4 bits designated C1 – C4, for each sub-multiframe. In those frames containingthe frame data word bit 1 is used to transmit a 6-bit CRC–4 multiframe alignment signaland two CRC–4 error indication bits (E).

This CRC multiframe alignment signal is 001011 spread over frames 1–11. The E-bitsindicate a received error from either of the two sub-multiframes (frame 13 bit 1=sub-multiframe 1 frame 15 bit 1= sub-multiframe 2).

CyclicRedundancyCheck

For each sub-multiframe, which consists of 2048 bits a polynomial is generated M(x).This polynomial is multiplied by X4 and then divided by the generator polynomial X4 + x +1. This calculation produces a remainder of 4 bits or less.

This remainder is transmitted to the distant end as the CRC–4 check bits (C–C).

At the distant end the CRC check bits are added to M(x) and the divided by G(x) theresult should equal zero. If it does not then an error has occurred and a remote error willbe transmitted to the distant end.

DatabaseCommand

To enable this command use:

Modify_value <site> CRC <VALUE><LINK TYPE><LINK ID>,

Site= 0 – 40Value= 0 is enabled

1 is disabledLink type= RSL, XBL, etcLink ID= Unique link ID at that site.




4–27

Cyclic Redundancy Checking(Timeslot 0 of a 32 Timeslot Frame)

SYS01_4_15

C1 to C4 are the CRC–4 check bitsSub–multiframe alignment = 001011E = CRC–4 error indication bitsA = Alarm Indication (Remote Flag)X = Spare bits

Key:

1 2 3 4 5 6 7 8

0 C1 0 0 1 1 0 1 1

FDW 1 0 1 A X X X X X

FAW 2 C2 0 0 1 1 0 1 1

1FDW 3 0 1 A X X X X X

1FAW 4 C3 0 0 1 1 0 1 1


FAW 6 C4 0 0 1 1 0 1 1


FAW 8 C1 0 0 1 1 0 1 1


2FAW 10 C2 0 0 1 1 0 1 1

2FDW 11 1 1 A X X X X X

FAW 12 C3 0 0 1 1 0 1 1

FDW 13 E 1 A X X X X X

FAW 14 C4 0 0 1 1 0 1 1

FDW 15 E 1 A X X X X X

SUB–MF(SMF)

FRAMENUMBER

BITS 1 TO 8 OF THE FRAME

FAW

ISSUE 12 REVISION 0High Bit-Rate Digital Subscriber Line (HDSL)



4–28

High Bit-Rate Digital Subscriber Line (HDSL)The purpose of HDSL is to allow transmission of high speed data over normal voicequality 64kbps twisted wire cables, thus reducing interconnectivity costs to the Networkoperator. A standard 2.048 Mbps E1 link is converted by a HDSL modem into two1168kbps data links, each of these being transmitted down a twisted wire pair. Each pairof wires is capable of operating at full duplex so that the same two pairs can be used fortransmission and reception at either end of the link.

The HDSL modem effectively splits the 2.048 Mbps into two and adds its own codinginformation to the resultant data streams. This brings the data rate up to 1168kbps foreach pair of wires. At the distant end the data from the two wires are recombined andthe E1 link is then presented to the terminal equipment as a standard 2.048 E1 format.The E1 link can be said to be transmitted transparently as when it arrives at the distantterminal it is exactly the same as when it was transmitted.

There are various modes of operation possible. Single pair mode is where only timeslots0 to 16 are transported over a single HDSL pair of wires. At the other end a full E1 frameis reconstituted using idle code for timeslots 17 to 31. Data must be sent in contiguousblocks when using this mode, i.e. timeslots 1, 2, 3 and 4 is a permitted combination, butnot 1, 3 and 5. Any unused timeslots of 1 to 16 are filled with idle code. This is anadvantage where low capacity sites are used.

There is a minimum quality threshold and this is determined by the gauge of wire usedand the distance of transmission. This leads to maximum possible transmissiondistances for each grade of wire. Typically for 0dB of ETSI noise the minimumtransmission range is as follows:

��

��

� ��

� ��

� ��

� ��

Typical applications are for M-CELLaccess (in buildings) and M-CELLmicro equipmentwhere site interconnection distances are relatively small and possibly existing twistedpairs may be used.

ISSUE 12 REVISION 0 High Bit-Rate Digital Subscriber Line (HDSL)



4–29

HDSL Modes of Operation

SYS01_4_16

Tx/Rx

HDSL Modem

Tx/Rx

Tx/Rx

HDSL Modem

Tx/Rx

HDSL Modem

Tx/Rx

Tx/Rx

HDSL Modem

1.168Mbps

1.168Mbps

1.168Mbps

Unstructured Mode – Transparent 2.048Mbps E1 transmission

Single Pair Mode – E1 timeslots 0 – 16 only

2.048MbpsE1 Link

2.048MbpsE1 Link

2.048MbpsE1 Link

2.048MbpsE1 Link

ISSUE 12 REVISION 0High Bit-Rate Digital Subscriber Line (HDSL)



4–30



i

Chapter 5

BTS – BSC Interface (A-bis)

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 5BTS – BSC Interface (A-bis) i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BTS – BSC Interface 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Objectives 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSC – BTS Interface (A-bis) 5–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



A-bis Limitations 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Link Capacity 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Processors 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Redundancy 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary 5–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motorola Defined A-bis Interface (Mobis) 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motorola A-bis 5–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Division between BSC and BTS 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MTP L3/SCCP Preselector 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Connectionless Manager 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP State Machine (SSM) 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Switch Manager 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cell Resource Manager 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio Resource State Machine (RRSM) 5–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio Channel Interface 5–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motorola/GSM A-bis Comparison 5–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GSM A-bis 5–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motorola A-bis 5–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Interface Structure 5–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MSI Defaults 5–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Links Logical Channels 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radio Signalling Link (RSL) 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transparent Messages 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layer 2 Management Link (L2ML) 5–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 2 – Link Access Procedure LAPD 5–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Structure 5–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Definition of Fields 5–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Address Field 5–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Access Point Identifier (SAPI) 5–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Terminal Endpoint Identifier (TEI) 5–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TEI Allocation 5–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Field 5–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Unnumbered Frames 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Set Asynchronous Balanced Mode Extended (SABME) Command 5–34. . . . . . . . . . . Disconnect (DISC) Command 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unnumbered Information (UI) Command 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unnumbered Acknowledgment (UA) Response 5–34. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Alignment Procedures 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layer 2 timers 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timer T203 5–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

Supervisory Control 5–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 2 – Link Access Procedure LAPD 5–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Check Sequence (FCS) Field 5–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Layer 3 Model 5–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Complete Layer 2/Layer 3 Message Example (A-bis Defined) 5–44. . . . . . . . . . . . . . . . . . . . . Encryption Command 5–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Discriminator 5–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Type 5–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 5–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Global Reset 5–52. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mobile Originated Connection Establishment 5–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 5–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Traffic Assignment Procedures 5–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Traffic Assignment Procedures 5–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Request Queued – T11 Expiry 5–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Message Sequence Scenarios 5–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Successful Intra-BTS Handover 5–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Successful Inter-BSC Handover 5–62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0 BTS – BSC Interface



5–1

BTS – BSC Interface

Objectives


� Identify the GSM Recommendations for the BSC – BTS interface.

� State the functions of the BSC – BTS interface.

� Identify the Layer 2 (LAPD) frame structure.

� Identify the limitations of the GSM A-bis interface.

� State the major components and functions of the Motorola BSC – BTS A-bisinterface.

� Identify the Layer 3 model.

� Identify the Layer 3 message structures.

ISSUE 12 REVISION 0BSC – BTS Interface (A-bis)



5–2

BSC – BTS Interface (A-bis)

Introduction

The interface is defined to be at the terrestrial link of a remote BTS connected to theBSC.

The BSC–BTS interface is specified by a set of characteristics including:

� Physical and electrical parameters

� Channel structures

� Signalling transfer procedures

� Configuration and control procedures

� Operation and maintenance support.

The BSC–BTS interface shall be capable of supporting all services offered to the GSMusers and subscribers. In addition, it shall also allow control of the radio equipment andradio frequency allocation in the BTS.

This interface is known as the A-bis within the GSM specifications, but was not rigorouslydefined. This has lead to various manufacturers developing their own specific signallingprotocol.

Motorola’s interpretation of the A-bis link places more functionality at the BTS, this resultsin reduced signalling on the A-bis link in comparison to other implementations.

ISSUE 12 REVISION 0 BSC – BTS Interface (A-bis)



5–3

BSC – BTS Interface (A-bis)

SYS01_5_2

BTS

BSC

Motorola’simplementation

1 x RSL at 64kbp/s per BTS

(minimum)

32 x 64 kb/s timeslots(2 Mbit/s)




5–4

GSM SpecificationsThe A-bis interface is defined in the 08.5X series of GSM specifications, which isdesigned to support a wide range of possible architecture.

� 08.51 General aspects of the interface.

� 08.52 Interface principles: This specification is intended to provide a unified way of connecting remotely located BTS to a BSC.

� 08.54 Layer 1 – the physical connectors alignment of the link.

� 08.56 Layer 2 – specifies the link layer used for signalling with the Link Access procedure on the D-channel (LAPD) specification.

� 08.58 Layer 3 – specifies the general structure of layer 3 and traffic management procedures and messages used on the A-bis interface to support the signalling procedures.

ISSUE 12 REVISION 0 GSM Specifications



5–5

GSM Specifications 08.5X

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ISSUE 12 REVISION 0Signalling Model



5–6

Signalling ModelThe A-bis interface uses a single 64 kbit/s timeslot on the 2 Mbit/s common bearer link.Motorola have defined this signalling link as the Radio Signalling Link (RSL), which usesthe LAPD frame structure.

Radio Resource (RR) messages are mapped to BSSAP (BSS Application Part) in theBSC. In the BTS most of them are handled as transparent messages where the BTSonly converts from one message format to another (eg. LAPDm – LAPD). However,some of them have to be interpreted by BTS (eg. random access).

The BTS Management (BTSM) entities contain procedures for handling these messagesand other procedures for managing the BTS. These provide the mapping betweenBTSM and the relevant RR messages on the radio interface.

The Layer 2 protocol over the A-bis interface is based on Link Access ProcedureD-Channel (LAPD). Where each individual BTS site and DRCU/TCU/SCU areaddressed separately using the Terminal Endpoint Identifier (TEI) of LAPD.

There are also a number of different Layer 2 procedures used for traffic managementmessages, which are indicated by the Service Access Point Identifier (SAPI).

ISSUE 12 REVISION 0 Signalling Model



5–7

A-bis Signalling Model

SYS01_5_4

Radio Signalling Link (RSL)

Air interfaceA-bis

RR

LAPDm LAPD

Layer 1 Layer 1

BTSM

BTS BSC

RR

LAPD

Layer 1

BTSM

BSSAP

SCCPMTP

BTSM = BTS Management

ISSUE 12 REVISION 0A-bis Limitations



5–8

A-bis Limitations

Introduction

The main idea of the A-bis interface is to create a Network element, the BTS, which is assimple as possible in order to minimize the interfacing required to the BSC. Therefore,due to the simple nature of the A-bis interface, this tends to limit what can be done to thearchitecture and the distribution of software functions among the various BSScomponents.

Several of these limitations are listed:

Link Capacity

In the A-bis interface a single 64 kbit data link is used to connect the BSC to the BTS andit has been calculated that this would be inadequate capacity to handle a busy cell.

Processors

One of the implications of keeping the BTS as simple as possible is that minimal callprocessing is done at the BTS. Locating most call processing activities at the BSCplaces an additional burden on the BSC–BTS data links which are already overloadeddue to Mobility Management procedures (location update, paging etc).

Redundancy

A-bis does not allow redundancy at the BTS level. The A-bis interface states that aone-to-one correspondence at all times between traffic channels and the megastreamtimeslot to the BSC.

Summary

The A-bis interface is lacking in several respects. Redundant control links are notsupported. It also has inadequate capacity to carry the message traffic calculated toexist on busy cells. It requires the BSC to keep track of the BTS’s current GSM framenumber, which could reduce delays in handovers.

ISSUE 12 REVISION 0 A-bis Limitations



5–9

GSM A-bis Limitations

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ISSUE 12 REVISION 0Motorola Defined A-bis Interface (Mobis)



5–10

Motorola Defined A-bis Interface (Mobis)

Introduction

To overcome the limitations of the GSM A-bis Motorola has defined its own A-bisinterface. Where possible GSM A-bis message formats are implemented. The messagetransfer between the BSC and BTS is done through the internal workings of the MotorolaBSS.

To implement a GSM A-bis interface, the LAPD protocol is used between the two entitiesand a translation of the protocol TEI and internal BSS executive references (mailboxesand logical references) is necessary.

Motorola A-bis

Main areas of improvement within Motorola A-bis are:

� Packing of pages; there is an inconsistency within the GSM Specifications as towhen and where this procedure can be carried out. Motorola interface willimplement this procedure at the BTS.

� Processing measurement reports/power control; if measurements are sent overthe A-bis link, this increases the traffic flow. The Motorola approach is to have themeasurement reports remain at the BTS, also have the power and timing advanceinformation calculated here as well. Thus greatly reducing the message flow overthe interface.

� Handover Detection; Since the measurements information is at the BTS, thehandover detection algorithm is executed here. When conditions exist for ahandover, an added message, handover_required , is passed over the A-bisinterface.

� Reject mode; a message is sent across the A-bis interface which allows CallProcessing to set the “reject mode” at the Radio Subsystem. Having this capacityreduces the message flow across the interface i.e. if the BSS is in a conditionwhere every channel request would receive an immediate assignment reject (nochannels available).

ISSUE 12 REVISION 0 Motorola Defined A-bis Interface (Mobis)



5–11

Motorola Defined A-bis Interface

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5–12

FunctionalDivision betweenBSC and BTS

Under the Motorola system, the control of radio resources/procedures and terrestrialcircuits (BSC to BTS) are split between the BSC and BTS. This split has enabledMotorola to reduce the number of signalling links required on the A-bis

The BSC retains the processes which control the terrestrial links to the MSC and theswitch manager. It also has the overall control of any handovers required via the SCCPstate machine process.

MTP L3/SCCPPreselector

This process handles the protocol adaption of messages when transmitting or receivingmessages from the A interface. It also decides what process a particular message isdestined for by the message header and then routes the message to the requiredprocess.

ConnectionlessManager

The Connectionless Manager process deals with the global control of a BSS. Thisprocess deals with the non-connection orientated portion of the C7 Signalling.

SCCP StateMachine (SSM)

The Signalling Control Connection Part State Machine (SSM) is responsible for handlingall the connection orientated portion of the C7 Signalling.

Switch Manager

The function of the Switch Manager is to connect a mobiles terrestrial trunk from theMSC (designated by the MSC), to the radio channel given to a mobile by the CellResource Manager in the BSS Software.

Cell ResourceManager

The Cell Resource Manager is responsible for the allocation of radio channels inresponse to either a mobile accessing the system or the MSC paging a mobile.

Radio ResourceState Machine(RRSM)

The Radio Resource State Machine is responsible for maintaining the state of calls.

This process is responsible for the activation of the radio channel on instructions from theCell Resource Manager. When a mobile no longer requires a radio channel, the RRSMis responsible for closing the channel down.




5–13

Motorola System

SYS01_5_7

MSC


MTP L3/SCCP Preprocessor

SCCP StateMachine

SwitchManager

RadioResource

StateMachine Radio

ChannelInterface

CellResourceManager

Radiosubsystem

Radiosubsystem

RadioChannelProcess

BTS

BSC




5–14

Radio ChannelInterface

The Radio Channel Interface process changes the address of a mobile used in the RSSinto the address used by the Layer 3 Call Processing processes.




5–15

Motorola System

SYS01_5_7

MSC


MTP L3/SCCP Preprocessor

SCCP StateMachine

SwitchManager

RadioResource

StateMachine Radio

ChannelInterface

CellResourceManager

Radiosubsystem

Radiosubsystem

RadioChannelProcess

BTS

BSC




5–16

Motorola/GSMA-bisComparison

To give a simple example of the advantage Motorola defined A-bis has over GSM A-bis isthe message sequence for the mobile originated connection establishment.

GSM A-bis

The Mobile Station (MS) generates the Access Burst (RACH) which requires the BTS torequest a channel from the BSC.

The BSC responds with a SDCCH channel activation message, which requiresacknowledging, before the BSC initiates the Immediate Assignment Command message.

This in turn initiates the Immediate Assignment message on the AGCH to the MS.

A Total of 4 messages on the BTS–BSC interface.

Motorola A-bis

The Radio Resource State manager (RRSM) and Radio Channel Interface (RCI) arewithin the BTS, therefore, no messages required to be sent over the BSC–BTS interface.




5–17

Motorola/GSM A-bis Comparison

SYS01_5_8

RACH

AGCH

Access BurstChannel Required

Immediate

Assignment

Channel Required

SDCCH Channel

Activation

Channel Activation

Acknowledged

Immediate AssignmentCommand

MS BTS BSC

Motorola A-bisNo messages over BTS–BSC interface

GSM A-bis

ISSUE 12 REVISION 0Interface Structure



5–18

Interface StructureThe Motorola interpretation of the A-bis interface recognises two types of communicationchannels:

� Traffic Channels – Carrying speech or data of one air interface radio channel (13 kbit/s traffic + 3 kbit/s of control)

� Signalling channel – 64 kbit/s carrying signal information (both BSC – BTS and BSC to MSC)

The signalling channel uses a single timeslot of the 2 Mbit/s common bearer.

The A-bis interface software entity is within the RSS subsystem. Messages are passedbetween the RSS subsystem and other BSS entities. The A-bis interfacescommunicates within the RSS with Handover/Measurement Evaluation and RSSConfiguration and Fault Management.

The A-bis interface software has the following major functions:

� Check downlink message validity

� Translate downlink messages into internal RSS address

� Translate uplink messages into RSS–CP messages

� Redundancy Operations for improved reliability

� Reporting/logging or erroneous states or events.

ISSUE 12 REVISION 0 Interface Structure



5–19

Signalling/Traffic Links

SYS01_5_9

BSC

MSI

KSW

BTP

DHP(RSS)

DRIM/DRCU

DRIM/DRCU

DHP(RSS)

LAN

MCAP MCAP

TDM highway(traffic and signalling)

TDM highway(signalling) TDM highway

traffic

RSL at 64 Kb/s (2 Mbit/s LINK)

BTS Cabinet

MS MS

MCAP

ISSUE 12 REVISION 0Interface Structure



5–20

MSI Defaults

The BTS sites can be connected by multiple 2Mbit/s lines which carry the traffic andsignalling link (RSL). The operator can specify the route between the BSC and BTS bythe software function called “PATH”.

To ensure that the BTS can re-establish the link in the event of a failure and resetconditions, at least one of these connections must be in the default position.

Up to four default RSL timeslots can be used by the BTS to contact the BSC in ROM tosupport code loading during the Initialisation procedure. The IP uses fixed MSI cardlocations and fixed 64kbit/sec timeslots at the BTS.

These default links can use the same 64kbit/sec timeslots as the RSL links equipped inthe database for passing signalling traffic to the BTS once the site has been initiated.Therefore the operator is required to equip a PATH for at least one RSL which willterminate using one of the default MSI and MMS locations.

DEFAULT POSITIONS ARE:

CAGE 15 SLOT 16 PORT 0 TIMESLOT 1CAGE 15 SLOT 16 PORT 1 TIMESLOT 2CAGE 15 SLOT 14 PORT 0 TIMESLOT 2CAGE 14 SLOT 16 PORT 0 TIMESLOT 2

The function of actually allocating timeslots on 2 Mbit/s lines is carried out by analgorithm. A timeslot is chosen independently for each 2 Mbit/s line in the PATH.

ISSUE 12 REVISION 0 Interface Structure



5–21

MSI Defaults

SYS01_5_10

BSC

BTS 1

BTS 2

BTS 3

RSL BTS 1cage 15MSI slot 16port 0timeslot 1



RSL BTS 2softwaredecision (any timeslot)



Path 1

Path 0

Path 2

ISSUE 12 REVISION 0Signalling Links Logical Channels



5–22

Signalling Links Logical Channels

The addressing of each Radio Channel Unit DRCU/TCU as well as the Base TransceiverProcessor (BTP) and MCU is made using separate Terminal Endpoint Identifiers (TEI).

The Layer 2 protocol over the A-bis interface is based on Link Access ProcedureD-channel (LAPD). There are different logical channels used for traffic managementmessages, these different logical channels are addressed using the Service Access Pointidentifier (SAPI) which forms part of the Layer 2 address field.

The three logical links are defined for each TEI.

� Radio Signalling Link (RSL) used for supporting traffic management procedures(MS to Network communication).

� Operations and Maintenance Link (OML) used for supporting Networkmanagement procedures. One Link per DRCU/TCU and BTP/MCU.

� Layer 2 Management Link (L2ML) used for transferring Layer 2 managementmessages to DRCU/TCU or BTP/MCU.

Only point to point signalling links are used.

Radio SignallingLink (RSL)

In every message, there is a message discriminator which is used to distinguish betweentransparent messages and non-transparent messages. The discriminator also definesthe message group type.

� Radio Link Layer Management

� Dedicated Channel Management

� Common Channel Management

� TRX (Transceiver) Management

TransparentMessages

Transparent messages are used to convey Layer 3 messages to/from the radio interfacefor which the BSC and BTS has no specific action.

These messages are defined in the GSM air-interface 04.08 and are referred to as DirectTransfer Application Part (DTAP).

Layer 2ManagementLink (L2ML)

This link is used by the BSC/BTS to carry reconfiguration and management messages.

ISSUE 12 REVISION 0 Signalling Links Logical Channels



5–23

Logical Channels

SYS01_5_11

BSPTEI = 0

RSL (SAPI 0)LTML (SAPI 63)OML (SAPI 62)

1 x 64 kbit TS

Logical channels BTSBSC

BTP/MCUTEI001

DRCU/TCU/SCUTEI002

DRCU/TCU/SCUTEI003

ISSUE 12 REVISION 0Layer 2 – Link Access Procedure LAPD



5–24

Layer 2 – Link Access Procedure LAPD

Introduction

This bit orientated data Link access protocol is a subset of High Level Data Link Control(HDLC) using the standard frame structure, with a ISDN address field layout.Specification GSM 08.56. (ITU–TS Recom Q.921)

The basic functional content of the Layer 2 protocol is shown opposite:

This is achieved by the passage of messages over the data link, normally called frames,which uses a standardised structure. There are three different frame types:

� Information (I) frame – used for the passage of messages both control andsignalling data.

� Supervisory (S) frame – used to maintain the link and flow control.

� Unnumbered (U) frame – used to establish the link (Layer 2 alignment)

ISSUE 12 REVISION 0 Layer 2 – Link Access Procedure LAPD



5–25

Link Access Procedure D-channel (LAPD)

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5–26

Frame Structure

The signalling information is passed by the LAPD protocol mechanism utilising acommon frame structure.

Each of the three different frames conform to this common frame structure, where eachframe consists of a number of fields each of which is defined to cover the variousfunctions of the interface protocol

Definition ofFields

Flag

The Flag pattern (01111110) denotes the start and end of each frame. The end flag canact as the start of the next frame providing it follows on immediately. The receiver willalways assume that a flag pattern followed by a non flag pattern signifies the beginning ofanother frame.

To prevent occurrence of this pattern within the frame a bit-stuffing technique isemployed. This technique inserts an extra ‘0’ after any 5 consecutive ‘1’s detected atthe transmitter, the receiver removes this extra ‘0’ by a process called ‘bit-stripping’.




5–27

Frame Structure – Flag

SYS01_5_13

Frame checksequence

Flag FlagInformation(Layer 3)

Control Address

0 1 1 1 1 1 1 0

8 16 Var 8/16 16 8

Information Type Frame

0 1 1 1 1 1 1 0 – defines beginning and/or end of frame

Unique Pattern




5–28

Address Field

The address field identifies the intended receiver within a command frame, and thetransmitter of the response frame, the format of the address field is shown opposite:

This field contains: address field extension (EA) bits; a command/response indication(C/R) bit; a data link layer Service Access Point Identifier (SAPI) subfield and a TerminalEndpoint Identifier (TEI) subfield.

The address field can be made up of more than one octet, to indicate this the first bit ofeach octet is set to 0, indicating that this is not the final octet. The presence of a 1 in thefirst bit of any octet signals that this is the final octet of the address field.

Command/response field bit (C/R): identifies the frame as either a command or responseframe.

Service AccessPoint Identifier(SAPI)

The SAPI identifies a point at which data link layer services are provided andconsequently the Layer 2/3 boundary.

The following SAPI’s are defined for use on the A-bis interface.

SAPI 0= Call control procedures (normally referred to as the RSL)

SAPI 62= Operation and Maintenance procedures (OML)

SAPI 63= Layer 2 management procedures (L2ML)

TerminalEndpointIdentifier (TEI)

The TEI identifies a unique function or element within the BSS.




5–29

Address Field Format

SYS01_5_14

Frame checksequence

Flag FlagInformation

Control Address

TEI

EA1 SAPI C/R

EA0

Octet No 3 Octet No 2

EA = Address field extension bit –“1” signifies end of address field

C/R = Command/response field bit –“1” – command, “0” = response

SAPI = Service Access Point Identifier(Valid SAPIs 0, 62, 63)

TEI = Terminal Endpoint Identifier




5–30

TerminalEndpointIdentifier (TEI)

The TEI for a point-to-point system is the physical address of a single terminalequipment. Within the A-bis interface the address indicates the base station masterGPROC (BTP)/MCU, the DRCUs/TCUs at the BTS site and the BSP at the BSC.

Within the Motorola system a single BSC can control upto 40 BTS sites, where each sitemust be equipped with a BTP. This BSC can only support a maximum of 50 BTPs/MCU.Each DRCU/TCU and BTP/MCU would require its own TEI address.

TEI Allocation

The TEI number is assigned when the BSC is initialised and is part of the database setup. The TEI’s are allocated in the same order as they are equipped in the database.

Example: A BSC controls two remote BTS’s, site 1 and site 2. Site 1 has 3 activecarriers and site 2 has 1 active carrier.

TEI Allocation

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5–31

TEI Allocation

SYS01_5_15

BTP/MCUDRCU/TCU/SCUDRCU/TCU/SCUDRCU/TCU/SCU

BTP/MCUDRCU/TCU/SCU

Assigned when BSC initializedTEIs allocated as equipped in database

BSC

Site 1

BSP

ISSUE 12 REVISION 0Control Field



5–32

Control FieldThis field identifies the type of frame which can be either a command or a response.

Send sequence number N(S) : Only Information (I) frames contain N(S) which is thenumber of each transmitted frame.

Receive sequence number N(R) : All Information frames and supervisory framescontain N(R), the expected send sequence number of the next received Informationframe. The value of N(R) also indicates it has correctly received all information framesnumbered up to and including N(R)– 1

All frames contain the Poll/Final (P/F) bit. The P/F bit serves a function in bothcommand and response frames. In command frames it is a P bit and response as a Fbit. When set to a 1 in either cases indicates a command or response required.

On the A-bis interface, Motorola uses the modulo 128 version of LAPD.

ISSUE 12 REVISION 0 Control Field



5–33

Control Field

SYS01_5_16

N(S) = Transmitter send sequence number

N(R) = Transmitter receiver sequence number

Poll bit (P) when as a commandFinal bit (F) when as a response

(2 octets)

8 7

0

P

N(S)

N(R)

1

P/FN(R)

N(R)

N(R)

0 0 0 0 0 00

0 0 0 0 0 01

0 0 0 0 1 00

1

1

P/F

P/F

10 1 1 P 1 11

0 0 0 P 0 10

0 1 1 F 0 10

1

1

10 0 0 F 1 11

10 1 0 P 0 10

Bit positions

I–frame

RR

RNR

REJ

SABME

DM

UI

DISC

UA

Octet

4

5

4

5

4

5

4

5

4

4

4

4

4

C/R

C/R

C/R

C

R

C

C

R

(UNNUMBERED)

(SUPERVISORY)

(INFORMATION)

C = Command

R = Response

FlagFrame check

sequenceInformation Control Address Flag

6 5 4 3 2 1

P/F =

ISSUE 12 REVISION 0Unnumbered Frames



5–34

Unnumbered FramesThere are a number of different unnumbered frames which are used within the linkalignment procedure.

SetAsynchronousBalanced ModeExtended(SABME)Command

The SABME command is used to place the addressed user side or network side into amodulo 128 multiple frame acknowledged operation. Upon acceptance of this commandboth N(S) and N(R) counter will be reset to 0.

Disconnect(DISC) Command

The DISC command is transmitted in order to terminate a multiframe operation. Eitherend can generate a DISC command, but only activate the command after receipt ofeither an UA or DM response.

UnnumberedInformation (UI)Command

Sent when unacknowledged Information Transfer is requested.

UnnumberedAcknowledgment(UA) Response

The UA unnumbered response is used to acknowledge the receipt and acceptance of themode setting commands (SABME or DISC).

Disconnected mode (DM) response

The DM unnumbered response is used to report to its peer-protocol that multiframeoperation cannot be performed.

ISSUE 12 REVISION 0 Unnumbered Frames



5–35

Types of U Frame used on the A-bis Link

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ISSUE 12 REVISION 0Alignment Procedures



5–36

Alignment ProceduresOnce the common bearer (2 Mbit/s) link has achieved synchronisation and checked theBER rate, the link will initiate a request for multiple frame operation, e.g. Layer 2alignment. This is set by one end transmitting a SABME command.

This condition causes timer T200 to be started, all existing conditions to be cleared andthe retransmission counter (N200) to be reset.

The distance end receiving this SABME command and is able to enter the multiframeestablish state (e.g Link alignment) will respond with a UA frame, reset the sequencecounter to zero (N(S), N(R)).

On receipt of this UA frame, T200 is reset and sequence counters N(S), N(R) are resetto zero

Now the link is available for information frames to be transmitted.

If timer T200 expires before receiving the UA frame, then the SABME is retransmittedand T200 is reset. Also retransmission counter N200 is incremented by a count of 1. IfN200 reaches its maximum value then link is passed back to Layer 1 e.g.resynchronisation.

Layer 2 timers

T200: This is the maximum time allowed without frames being exchanged.

(eg. acknowledgment of SABME )

Typical Value= 1 second

However Motorola allow this value to be increased to 2.5 seconds when BTS to BSClinks have long propagation delays.

Timer T203

This timer is the maximum time allowed without a frame being exchanged for each TEI.On an idle link, this will cause an RR frame to be transmitted as a sanity check.

ISSUE 12 REVISION 0 Alignment Procedures



5–37

Layer 2 Alignment

SYS01_5_18

N200 Incremented (N200=1)T200 started

T200 started/N200=0 N(S)=0/N(R)=0SABME

UA

I FRAME

I FRAME

T200 StoppedN(S)=0 (N(R)=0

T200/T203both started

T200 ResetT203 Reset

SABME

SABME

T200 started/N200=0

T200 Expires

2 Mbit/s Link

BTS BSC

Successful

Unsuccessful

Not received ornot in synchronization

BTS BSC

ISSUE 12 REVISION 0Supervisory Control



5–38

Supervisory ControlThe other feature of the control field is to control the sequencing of frames and performsupervisory control. To do this there are four possible supervisory frames, only three areused on the A-bis interface.

Receive Ready (RR) command/response

� Indicates ready to receive Information (I) frames.

� Acknowledges previously received I frames numbered upto and including N(R)–1

� Clears a busy condition

Receive not Ready (RNR) command/response

� Indicates a busy condition; e.g. a temporary inability to accept additional I frames.

� Acknowledges all frames up to N(R)–1

Reject (REJ) command/response

� The REJ frame is used to request retransmission of I frames starting with theframe numbered N(R). All new I frames are held until acknowledgment of theretransmission frame.

� Each I frame increments the N(S) sequence counter, before being transmittedhowever the control field only has 7 bits to indicate this number, thus it is restrictedto a count of 0–127. This then is the maximum number (k) of sequentiallynumbered I frames that may be transmitted at a given time, beforeacknowledgment of one frame is required. To enable the transmission of further Iframes, the distance end must reply with either an I frame or a RR frame with theappropriate N(R) set.

� To avoid infinite loop situations. Retransmissions are limited to a maximum value(N200) and the maximum wait time to wait for any response (T200).

ISSUE 12 REVISION 0 Supervisory Control



5–39

Supervisory Control

SYS01_5_19

2 Mbit/s Link

N(S)

–

I Frame

I Frame

I Frame

I Frame

I Frame

I Frame

I Frame

RR

REJ

RR

Retransmission ofmsg No2

Retransmission ofmsg No3

N(R)

0

0

0

1

1

1

NEXT MSGEXPECTED

Ack Msg 0

REJECTMSG NO2

NEXT MsgEXPECTED

(msg 0+1 alreadyAcknowledged)

AcknowledgesMsg 2 and Msg 3

CLEAR BUFFER OFMsg 0 + Msg 1

BTS BSC

N(S)

0

1

2

3

2

3

2

0 2

–

– 2

– 4

N(R)




5–40

Layer 2 – Link Access Procedure LAPD

Frame CheckSequence (FCS)Field

The frame check sequence is a 16 bit cyclic redundancy check which is performed on thebits found in the following fields:

Address

Control

Information

The FCS is used to detect the presence of errors resulting from transmission. TheITU–TS defined D+CRC is x16 + x12 + x5 + 1 using this polynomial code we can catch allsingle and double errors, all errors with an odd number of bits. All burst errors of length16 or less, 99.997% of 17 bit error bursts, and 99.998% of 18 bit and longer bursts.

The following method is used to calculate the FCS:

M(x) Message to be transmitted polynomial

G(x) Generator polynomial (x16 +x12 + x5 + 1, CRC)

xk The highest polynomial value in the Generator polynomial

Formula: M(x) . xk

G (x)

The result of this calculation will be a whole number and a remainder (16 bits or less) theremainder is the FCS which is transmitted to the distant end. At the distant end the Rxadds the FCS to the Rx message and divides the result by G(x) the answer should equal0 (no errors) if the answer results in any other value then the frame is rejected.




5–41

Frame Check Sequence

SYS01_5_20

ITU–TS – CRC

x16 + x12+ x5 + 1

Formula: M(x) . xk

G (x)= whole number + remainder

The remainder is 16 bits or less.The remainder is Tx as the FCS to the distant end.

Note:

ISSUE 12 REVISION 0Layer 3 Model



5–42

Layer 3 ModelAll messages between the BSC and BTS are composed of a number of elements.

The Layer 3 message is formatted as shown opposite.

Executive Header – This is Motorola defined and is Motorola confidential.

Discriminator – Transparent/non-transparent, Radio Link LayerManagement, Dedicated Channel Management, Common Channel Management, TRX Management messages and Motorola defined internal messages.

Message Type – The message type is sent with all messages and uniquely identifies the function of the message being sent. It is a single octet in length.

This element is defined by either GSM recs. 08.58 or Motorola.

Information Elements – The information elements are of variable length, the first octet is called the element identifier this is again either defined by GSM recs. 08.58 or by Motorola.

Motorola due to their implementation of the BSS functionality do not use a largeproportion of the GSM defined 08.58 messages across the RSL. A list of messagesdefined by Motorola and passed across the RSL are shown in Annex A.

ISSUE 12 REVISION 0 Layer 3 Model



5–43

Message Structure

SYS01_5_21

Frame checksequence

Flag FlagInformation Control Address

Motorola informationelements or A-bis 08.58

messages and/orcomplete L3 information

for transparent messages(04.08)

Information elements

Message typeMessage

discriminatorMotorola executivemessage header

Message typeTransaction identifier

or skip indicatorProtocol discriminator

Complete L3 Info as defined in TS GSM 04.08 or TS GSM 08.58

L2

L3

ISSUE 12 REVISION 0Complete Layer 2/Layer 3 Message Example (A-bis Defined)



5–44

Complete Layer 2/Layer 3 Message Example (A-bis Defined)As an example of a message on the A-bis link we will look at the CIPHERING MODECOMMAND which is sent from the MSC to the MS to start ciphering. This messagecannot be sent as a TRANSPARENT message as would be expected but is sent as aNON-TRANSPARENT message as the BTS requires some of the information to enableciphering at the BTS.

Due to this fact the CIPHERING MODE COMMAND is replaced on the A-bis byENCRYPTION COMMAND (TS GSM 08.58, section 8).

The ENCRYPTION COMMAND fits in the Layer 2 message in the information field and isformatted:

EncryptionCommand

This message is sent from BSC to BTS to start ciphering mode operation

��

��

��

�"..�$"�!&. -&)&*�/+- ��

�"..�$"�/1," ��

�%�**"(�*0)�"- ��

�* -1,/&+*�&*#+-)�/&+* ��

�&*'��!"*/&#&"- ��

��*#+��

The L3 Info element contains the complete Ciphering Mode Command message asdefined in Technical Specification GSM 04.08.

Note:

On the Motorola A-bis the CIPHERING MODE COMMAND from the MSC is replacedwith a CIPHERING REQUEST. The definition of the Information elements of thismessage are either defined by Motorola or TS GSM 08.08:

��

��

�"..�$"��1," �+/+-+(� � �

��"#"-"* "��0)�"- �+/+-+(� �

��1"-��"�!"-��*#+-)�/&+* ��

� ��

�

�* -1,/&+*��*#+-)�/&+* ��

� ��

� ��*

ISS

UE

12 RE

VIS

ION

0C

omplete Layer 2/Layer 3 M

essage Exam

ple (A-bis D

efined)

�M

OTO

RO

LA LT

D. 2000

SY

S01: G

SM

System

Interfaces

FO

R T

RA

ININ

G P

UR

PO

SE

S O

NLY

5–45

L2/L3 Message E

xample (G

SM

A-bis)TEI

EA1 SAPI C/R

SY

S01_5_22

Frame checksequence

Flag FlagInformation(Layer 3)

Control Address

1 octet 2 octet “n” octets 2 octets 2 octets 1 octet

EA0

2 octets

N(R) P N(S) X

2 octets

2 octets

L3 information(cipher mode command) Link identifier Encryption information Channel number Message type Message discriminator

SAPI identifierand channel type(FACCH/SDCCH)

(SACCH)

2 octets

Algorithm identifierand key

> =3 octets

Which channelthe message is

to be sent to

2 octets

ENCRyptionCoMmanD

1 octet

Dedicated channelmanagement

message(non-transparent)

1 octet6 octets

ISSUE 12 REVISION 0Complete Layer 2/Layer 3 Message Example (A-bis Defined)



5–46

MessageDiscriminator

A 1 octet field is used in all messages to discriminate between Transparent andNon-Transparent messages and also between Radio Link Layer Management, DedicatedChannel Management, Common Channel Management and TRX Managementmessages.

The T-bit is set to 1 to indicate that the message is to be/was considered transparent byBTS. All other messages shall have the T-bit set to 0.

The G-bits are used to group the messages as follows:

� �� "�

� � � � � � � � �� #��

� � � � � � � � �� $��!��

� � � � � � � � ��!��!��

� � � � � � � � ��!��

� � � � � � � � ��!

ISSUE 12 REVISION 0 Complete Layer 2/Layer 3 Message Example (A-bis Defined)



5–47

Message Structure

SYS01_5_23

Frame checksequence


Motorolainformation elements

or GSM 05.58 messagesor

Complete L3 informationfor transparent messages

(04.08)

Messagediscriminator

Type

MotorolaExecutive message

header

G7 G6 G5 G4 G3 G2 G1 T

ISSUE 12 REVISION 0Message Type



5–48

Message TypeThe message Type uniquely identifies the function of the message being sent. It is asingle octet in length. The following are GSM defined A-bis messages.

Bit 8 is the extension bit and is reserved for future use. The following Message Typesare used (all other values are reserved):

� � � � � � �(33$)(

� � � � � � � � �$'+0��+/,��$8(2��$/$)(.(/4�.(33$)(3�

� � � � ��5(34 � �� +&$4+0/ � �� +&$4+0/

� � � � ��$%-+3*��5(34

� � � � ��$%-+3*��+2.

� � � � ��$%-+3*��+&$4+0/

� � � � ��($3(��5(34

� � � � ��($3(��+2.

� � � � ��($3(��+&$4+0/

� � � � ��5(34 � �� +&$4+0/ � ��

� � � � � � � � �0..0/��*$//(-��$/$)(.(/4

� � � � ��2.$4+0/

� � � � ��+&$4+0/

� � � � ��/(-��(�5+2(�

� � � � ��+&$4+0/

� � � � ��0..$/�

� � � � ��

� � � � �� 20$'�$34��5(34�

� � � � �� 20$'&$34��0�.$/�

� � � � � � � � ��"��$/$)(.(/4��(33$)(3

� � � � ��052&(��+&$4+0/

� � � � ��+/)

� � � � � ��

� � � � ��

� � � � � � � � �('+&$4('��*$//(-��$/$)(.(/4�.(33$)(3�

� � � � � ��/(-�� $4+0/

� � � � � ��/(-�� $4+0/��/07-(')(

� � � � � ��/(-�� $4+0/��()$4+6(��

� � � � � ��(&4+0/��52(

� � � � � ��

� � � � � ��814+0/��0�.$/�

� � � � � ��6(2��(&4+0/

� � � � � ��52(.(/4��5-4

� � � � � ��#��5(34

� � � � � ��#��/07-(')(

� � � � � ��#��()$4+6(��/07-(')(

� � � � � ��#3+&$-��"��5(34

� � � � � ��#3+&$-��"��+2.

� � � � � ��/(-��($3(

� � � � � ��!��

� � � � � ��!��

� � � � � ��(33('��52(

� � � � � ��(33('��52(.(/4��5-4

� � � � � ��/(-��($3(��/07-(')(

ISSUE 12 REVISION 0 Message Type



5–49

Message Structure

EM

SYS01_5_24

Frame checksequence


Motorolainformation elements

or GSM 08.58 messagesor

Complete L3 informationfor transparent messages

(04.08)

Messagediscriminator

TypeMotorola

Executive messageheader

Message type




5–50

Message Sequence ScenariosThe best way of understanding the interface procedures is to examine the commonmessage sequence scenarios, which highlight the flow of messages between the MSC,BSC, BTS and MS.

The messages between the MSC and BSC are defined within the A-interface (TS GSM08.08) and will be covered later in the course.

The messages between the BSC and the BTS are defined within the A-bis interface (TSGSM 08.58).

The messages between the BTS and MS are defined within the Air-interface (TS GSM04.08).

The messages between the MSC and MS, referred to as Direct Transfer Application Part(DTAP) are transparent to the BSS. These messages/procedures will be covered later inthe course so are not shown.

The main message sequence scenarios are shown:

� Mobile Originated Connection Establishment; there are three different scenarios,successful, rejected by MSC and no radio resources available.

� Traffic Assignments four scenarios, successful, failure, Queued and T11 expiry.

� Handover procedures: These procedures are defined for both source and targetcell for successful and failed. Also defined in intra-BSS handovers.

� Global Reset: Complete reset at either end.




5–51


��

��

��

��




5–52


Global Reset

The Global Reset procedure on the A-bis interface is always initiated by the BSC. Thishowever can be as a result of the BSC receiving a Global Reset command from theMSC.

The Global Reset is when the BSC has to completely reboot all of its process proceduresand as a consequence, cause each BTS to be taken out of “Call Process” and if need berebooted.

If it is the case that each BTS site has to reboot then each must re-register to the BSC.This procedure is the BTS site indicating to the BSC that each of its cells are in “CallProcessing” mode and is capable of supporting traffic.




5–53

Global Reset

SYS01_5_26

Halt BSS

Halt BSSAcknowledgeGlobal Reset

Global ResetAcknowledge

Register

Register Acknowledge

Start BSS

Start BSSAcknowledge

Reboot

Call processavailable

Trafficavailable

GlobalReset

BSC BTS

ISSUE 12 REVISION 0Mobile Originated Connection Establishment



5–54

Mobile Originated Connection EstablishmentAfter the BSC and the BTS have completed the registration procedure, calls can beestablished.

This is initiated by the Mobile transmitting an Access Burst on the appropriate CommonControl Channel (CCCH). If the Mobile is detected by the BTS, this will generate theimmediate Assignment message and send it over the Access Granted Channel (AGCH).This control tells the mobile on which Standalone Channel (SDCCH) the rest of the cellsetup procedure will take place.

The Mobile will establish contact on the SDCCH by transmitting a SABM LAPDm framecontaining the DTAP message “CM Service Request”. The BTS carries out two actions.

� Send a UA LAPDm frame back to the Mobile.

� Generate the “Initial Layer 3 Info” message containing the DTAP message “CMService Request” and sends it to the BSC.

It is at this stage that the BSC initiates the connection to the MSC using SCCPprocedures (these will be covered later in the course).

After the connection is made, the MSC can command the Mobile to go to “cipher” mode,before the rest of the setup procedure is carried out. These other procedures use theDTAP messages across the A-bis interface and are passed as transparent messages.

ISSUE 12 REVISION 0 Mobile Originated Connection Establishment



5–55

Mobile Originated Connection Establishment

SYS01_5_27

SCCP Connections Request

Initial Layer 3 Info

Access Burst

<CM Service Request>SCCP Connections Confirm

Cipher Mode Command


DT1 <SET-UP>

DT1 <Call Proceeding>

<CM Service Request>

Ciphering Request

Ciphering Successful

DTAP <SET-UP>

DTAP <Call Proceeding>


SABM<CM Service Request>

Ciphering Mode Complete

Ciphering Mode Complete

SET–UP

Call Proceeding

UA

A interface Mobis LAPDm

MSBTSBSCMSC




5–56


TrafficAssignmentProcedures

The traffic assignment procedure is initiated by the MSC sending the AssignmentRequest message to the BSC.

This message will contain the type of channel required; classmark of the MS; the timeslot(traffic channel) on the BSC–MSC link.

The BSC request the BTS to allocate it a traffic channel.

It also starts a timer (assign_successful) which sets the maximum time the BSC will waitfor a reply. If this expires before receiving the Assignment Successful message, it willgenerate and Assignment Failure message back to the MSC.

The BTS site after assigning the traffic channel will generate the “Assignment Command”message and transmits this to the mobile via the SDCCH. It will also start a timer(bssmap_t10) which is the maximum time the BTS will wait for the mobile to establishcontact on the new traffic channel. This timer is stopped on receipt of the “AssignmentComplete” message from the mobile.

The BTS then generates the “Assignment Successful” message to the BSC and stopsassign_successful.




5–57

Traffic Assignment Procedures

SYS01_5_28

Assignment Request

Informationi.e. Type of channel requiredClassmark of the MSThe timeslot

Assignment Complete

Initiate Assignment

Assignment Successful

Timer

assign_successful

Assignment Command

Assignment Complete

BTSBSCMSC MS

Successful

Timer

bssmap_t10

ISSUE 12 REVISION 0Traffic Assignment Procedures



5–58

Traffic Assignment Procedures

Request Queued– T11 Expiry

Upon receipt of the Assignment Request message from the MSC the BSC sends anInitiate Assignment message to the BTS, if the BTS supports queuing and no resourcesare currently available then the BTS will send an Assignment queued message back tothe BSC to indicate that no resources are currently available and the request is queued.

Upon queuing of the Initiate assignment command the BTS starts timer T11(bssmap_t11) if resources do not become available before T11 expires then a ReleaseRequest message is sent to the BSC, the BSC will then initiate the release of the channelresources already in use (SDCCH).

ISSUE 12 REVISION 0 Traffic Assignment Procedures



5–59

Traffic Assignment Queued – T11 Expiry

SYS01_5_29

Assignment Request

SCCP Release Complete

BTSBSCMSC MS

Queueing Indication

Clear Request

Clear Command

Initiate Assignment

Assignment Queued

Release Request

Radio Channel Released

Release Radio Channel

Deallocate SCCP Number

Channel Release

SCCP Release

Clear Complete

T11 startedbssmap_t11

T11 expires




5–60


SuccessfulIntra-BTSHandover

During a call the MS sends at least one Measurement Report (MR) per second to theBTS, the MR reports on the best six neighbours and the serving cell. The BTS willevaluate these MR’s and based upon database values will generate a HandoverRecognised message to the BSC.

When the BTS generates the Handover Recognised message it starts a timer (1), thistimer is the maximum time the BTS will wait for a response before it will generate anotherHandover Recognised Message (provided the same cause for the handover exists).

From the Handover Recognised message (this contains a list of the preferred targetcells for a handover) the BSC will select a target BTS and generate an InternalHandover Request message to the target BTS. The Internal Handover Requestmessage asks the target BTS to supply a traffic channel. The BSC will also start timer(2) on issue of the Internal Handover Request message as this is the maximum timethe BSC will wait for the BTS to respond.

The target BTS will respond (providing there is a traffic channel available) with aHandover Allocation message. the target BTS will now start timer (3), this timer setsthe maximum time the BTS will keep the traffic channel assigned for this handover.

Upon receipt of the Handover Allocation message the BSC will stop timer (2) and issuea Initiate Handover message to the source BTS and start timer (4). This timer is usedto set the maximum time the BSC waits for an internal handover to complete.

Upon receipt of the Initiate Handover message the source BTS will stop timer (1) andissues a Handover Command to the MS and start timer (5), this timer sets themaximum time the source BTS will wait for a successful handover message.

The MS will attempt to establish on the new traffic channel on the target BTS, once thetarget BTS detects the MS it generates a Handover Detect message to the BSC. Uponreceipt of a Handover Complete message from the MS the target BTS stops (3) andissues a Handover Successful message to the BSC.

The BSC on receipt of the Handover Successful message will stop timer (4) andgenerate a Handover Performed message to the MSC and a Blast message to thesource BTS to clear down the resources held there.




5–61

Handover – BTS to BTS (intra-BTS)

SYS01_5_30

BSCBTSMS BTS BTS

Measurement Report

Handover Recognized

Internal HandoverRequest

Handover Allocation

Initiate Handover

Timer (1)

Timer (2)

Handover Command

Handover Access

Handover Complete

Handover Detect

Handover Successful

Timer (5)

Timer (3)

Timer (4)

Handover Performed

BLAST

ISSUE 12 REVISION 0Successful Inter-BSC Handover



5–62

Successful Inter-BSC HandoverIf after the Handover Recognised message has been passed to the BSC, the target BTS(cell) is not under control of the same BSC then a External Handover is required,normally referred to as a inter-BSC handover.

The procedure is the same, but some extra messages are generated with different timersused. This is due to the extra time required to send/acknowledge these messages bothon the A-bis (BTS–BSC) interface and A-Interface (BSC to MSC).

The diagram opposite shows the complete sequence at each side of the handover.

ISSUE 12 REVISION 0 Successful Inter-BSC Handover



5–63

Handover – Inter-BSC (Source Cell)

SYS01_5_31

MSCBSCBTS BSC MSBTS

MRH/O REC

H/O REQSCCP CR

H/O REQUEST H/O REQUEST

H/O ALLOCSCCP CC

H/O COMMANDH/O REQUEST ACK

INITIATE H/OH/O COMMAND

H/O ACCESS

H/O DETECT

H/O DETECT

H/O COMPLETE

H/OSUCCESSFUL

H/O COMPLETE

CLEARCOMMAND

BLAST

ISSUE 12 REVISION 0Successful Inter-BSC Handover



5–64

ISSUE 12 REVISION 0



5–i

Appendix A

ISSUE 12 REVISION 0BSC to BTS Interface Message Types



5–ii

BSC to BTS Interface Message TypesPart A – Message Types as Defined and Implemented by Motorola

BSC to BTSMessages

1. Audit Call

Description: This message is sent periodically per cell between the BSC and BTS to verify that the call is still active at the other side of the link. The information in this message is compared with the local information to verify that the BSC and BTS have consistent call data.

2. Audit RRSM Call Response

Description: This message is sent in response to an Audit Call message.

3. Blast Command

Description: This message is sent to the BTS after an internal handover, to tear down the dedicated channel resources on the source cell if the handover is successful or the destination cell if the handover procedure fails. Upon receipt of this message, the call is released at the BTS and no response is returned to the BSC.

4. BSS Status

Description: This message is sent to inform the BTS is the BSS BSSMAP subsystem goes into service or out of service.

5. Ciphering Request

Description: This message is sent to initiate ciphering when a Cipher Mode Command is received from the MSC.

6. Deallocate SCCP Reference Number

Description: Upon receipt of this message the BTS will mark the given SCCP reference number as unused.

7. Global Reset

Description: This message is sent to the BTS so that it can reset its state tables after a global reset.

8. Halt BSS

Description: This message is sent by the BSC when it wishes to halt call processing activities due to a global reset.

9. Handover Request

Description: This message is sent from the MSC to the BSS to indicate that a mobile is to be handed over to that BSS. The BSC sends this message to the BTS if it is contained in the data field of the SCCP Connection Request message.

10. Information Request

Description: This message is sent to the BTS to request information about the idleresources when Resource Request message is received from the MSC.

11. Initiate Assignment

Description: This message is sent to the BTS upon receipt of an Assignment Request message from the MSC.

ISSUE 12 REVISION 0 Part A – Message Types as Defined and Implemented by Motorola



5–iii

12. Initiate Handover

Description: This message is sent to the BTS which manages the source cell of a handover and includes the allocated destination channel information to be sent to the MS.

13. Initiate Intra-Cell Handover

Description: This message is sent to the BTS in order to initiate the intra-cell handover procedure.

14. Internal Handover Initiated Acknowledge

Description: This message is sent to the BTS in response to an Internal handover Initiated message. This message is used to avoid race conditions that may result if the MSC initiates a procedure at the same time as the BTS initiates an internal intra-cell handover.

15. Internal Handover Request

Description: This message is sent to the destination cell BTS in an intra-BSS handover. The BTS allocates the requested resources.

16. MSC Status

Description: This message is sent to the BTS to inform is of the state of the SCCP Layer or BSSAP Subsystem at the MSC.

17. Page mobile Request

Description: This message is sent to the BTS to instruct it to send a Paging Request message when a Paging message is received from the MSC.

18. Register Acknowledge

Description: This message is sent to the BTS to acknowledge registration.

19. Release Radio Channel

Description: This message is sent to the BTS to acknowledge registration.

20. Remove From Queue

Description: This message is sent to the BTS when a Handover Request message has been queued and guard timer (Tqho) has expired. The BTS removes the request from the queue and the handover procedure is aborted.

21. Start BSS

Description: This message is to the BTS to allow call processing activities to start.

22. Trace Request

Description: This message is to the BTS when data is required for call trace.

ISSUE 12 REVISION 0Part A – Message Types as Defined and Implemented by Motorola



5–iv

BTS to BSCMessages asDefined andImplemented byMotorola

1. Assignment Queued

Description: This message is sent to the BSC when an assignment request has been queued by the BTS.

2. Assignment Successful

Description: This message is sent to the BSC when an Assignment Complete is received from the MS.

3. Audit Call

Description: This message is sent periodically per call between the BSC and BTS to verify that the call is still active at the other side of the link. The information in this message is compared with the local information to verify that the BSC and BTS have consistent call data.

4. Audit SSM Call Response

Description: This message is sent to the BSC in response to an audit call message.

5. Call Trace Response

Description: This message is sent to the BSC containing trace data that has been collected at the BTS.

6. Ciphering Successful

Description: This message is sent to the BSC upon receipt of the Cipher Mode Complete message from the MS.

7. DTAP Message

Description: This message is used to transfer a DTAP message internally between the BTS and the BSC in either the uplink or downlink direction. Please note that the DTAP message can be any DTAP message defined in GSM Recommendation 4.08.

8. Global Reset Acknowledge

Description: This message is sent in response to a Global Reset message to inform the BSC that all tables at the BTS have been reset.

9. Halt BSS Acknowledge

Description: This message is sent to the BTS to acknowledge that all call processing activities at the BTS have been stopped.

10. Handover Allocation

Description: This message is sent to the BSC when a resource has been allocated for an external or internal handover.

11. Handover Detect Received

Description: This message is sent to the BSC when the BTS receives the handover Access message from the MS. The BSC then sends the Handover Detect message to the MSC.

ISSUE 12 REVISION 0 Part A – Message Types as Defined and Implemented by Motorola



5–v

12. Handover Failure

Description: This message is contained in the data field of the Connection refusedSCCP message. This message is forwarded to the MSC from the BSC. it indicates to the MSC that there has been a failure in the resource allocation process on handover and that the handover has been aborted.

13. Handover Recognised Received

Description: This message is sent to the BSC when Measurement Report messages from the MS indicate that the specified call requires a handover to a new cell.

14. Handover Request Queued

Description: This message is sent to the BSC when a handover request has been queued by the BTS.

15. Handover Resources Not Available

Description: This message is sent to the BSC if the BTS is unable to allocate the requested resource for an internal handover.

16. Handover Successful

Description: This message is sent to the BSC when the MS has successfully accessed the allocated radio channel on the destination cell of a handover.

17. Initial Layer 3 Information

Description: This message is sent to initiate a call at the BSC. The BTS sends this message when the MS had established on a dedicated channel.

18. Internal Handover Initiated

Description: This message is sent to the BSC when the resources for an internal handover have been successfully allocated.

19. Radio Channel Release

Description: This message is sent to the BSC to indicate that the allocated radio channel has been released at the BTS.

20. Register

Description: This message is sent by the BTS to inform the BSC that the BTS is available for call processing activities.

21. Release Request

Description: This message is sent to the BSC when the guard timer on an assignment request queue times out before the requested resources become available.

22. Resource Indication

Description: This message is contained in the data field of the UDT SCCP message and forwarded directly to the MSC in response to a Resource Request message from the MSC.

23. SCCP Number Assigned

Description: This message is sent to the BSC if an SCCP Connection Request is received from the MSC without a handover request in the data field. The BTS assigns an SCCP Reference number and sends it within this message to the BSC.The BSC then sends an SCCP Connection Confirm to the MSC.

ISSUE 12 REVISION 0Part A – Message Types as Defined and Implemented by Motorola



5–vi

24. Start BSS Acknowledge

Description: This message is sent in response to a request by the BTS to start callprocessing activities.

25. Unsuccessful Assignment

Description: This message is sent to the BSC if the MS is unable to access the allocated resources in an assignment procedure.

26. Unsuccessful Handover

Description: This message is sent if the MS re-establishes on the source cell afteran unsuccessful attempt to access the destination cell.

27. Update Classmark

Description: This message is sent to the BSC upon receipt of the Classmark Change message from the MS.

ISSUE 12 REVISION 0 Part B



5–vii

Part BMessage Elements

1) MessageElements definedby GSM 08.08

1. Circuit Identity Code

This element defines the terrestrial channel over which the call will pass. If a 2048kbit/s digital path is used then the circuit identification code contains in the 5 least significant bits of binary representation of the actual number of the timeslot which is assigned to the circuit. The remaining bits in the CIC are used where necessary, to identify one among several systems interconnecting an originating and destination point.

2. Radio Channel Identity

In messages relating to the serving cell the element is coded as:

3. Resource Available

This element gives the number of full and half rate channels available on any givencell at the time of construction of the message.

It identifies these parameters in terms of the number of channels available in five interference bands, the boundaries of these bands being set by O & M.

4. Cause

The cause element is used to indicate the reason for particular event to have occurred.

5. IMSI

The IMSI is coded as a sequence of BCD digits, compressed two into each octet. This is a variable length element, and includes a length indicator. The end of the element is indicated by a code 15, if this does not equate to an integral number of octets in the message then a filter nibble will be added.

6. TMSI

The TMSI is a variable length element, and therefore contains a length indicator. The TMSI is an unstructured number upto 4 octets in length, it is however an integral number of octets.

7. Number of MSs

This is fixed length element which indicates the number of handover candidates that will be sent to the MSC.

8. Layer 3 Header Information

This element is used to supply the BSS with information that needs to be included in the header of Layer 3 messages over the radio interface.

9. Encryption Information

This element contains the user data encryption information used to control any equipment at the BSS. It is variable length element.

10. Channel Type

This element contains all of the information that the BSS requires to determine the radio resource that is required.

ISSUE 12 REVISION 0Message Elements



5–viii

11. Periodicity

This element defines the periodicity of a particular procedure is as follows:

12. Cell Identifier

The element uniquely identifies a cell within a BSS and is of variable length.

13. Priority

This element indicates the priority of the request.

14. Classmark Information Type 2

The classmark information type 2 defines certain attributes of the mobile station equipment in use on a particular transaction.

15. Interference Band to be Used

A bit map indicating which interference bands are acceptable.

16. RR Cause

This fixed length element is passed from the air interface to the MSC transparently,when received in a specification GSM 4.08 message.

17. Trace Number

A fixed length element giving a 16 bit binary reference number.

18. Complete Layer 3 Information

This is a variable element used to pass layer three messages from the air interfaceto the MSC unchanged – it differs from the DTAP message because the BSS analyses part of the message as it passes through the BSS, it is not therefore a transparent message as such.

19. DLCI

This is a fixed length element indicating the channel on which the SAPI value over the air interface that the transaction concerns.

20. Downlink DTX Flag

A fixed length element indicating whether the DTX function in the BSS is to be disabled on a particular radio channel.

21. Resource Indication Method

This element defines the way the BSS shall transfer the resource information related to a cell to the MSC.

22. Classmark Information Type 1

The classmark information type 1 defines certain attributes of the Mobile Station equipment in use on a particular transaction. It is coded as follows:

ISSUE 12 REVISION 0 Message Elements



5–ix


1. Channel Number

The Channel Number is used to identify the physical channel/subchannel.

2. Activation Type

This element is used to indicate the type of activation requested in the Channel Activation message.

3. L3 Information

This element contains a link layer service data unit (L3 message). It is used to forward a complete L3 message between the RSS and Call Processing.

4. MS Identity

This element carries the identity of an MS (TMSI or IMSI). It is a variable length element.

5. Paging Group

This element carries the paging population of an MS to be paged.




5–x


1. Mobile Station Classmark 2

The purpose of the Mobile Station classmark 2 information elements is to provide the Network with information concerning aspects of both high an low priority of the MS equipment. This affects the matter in which the Network handles the operationof the MS.

2. Channel Description

The purpose of the channel description information element is to provide a description of an allocatable channel together with its SACCH. The channel description is a type 3 information element with 4 octets length.

3. Mobile Allocation

The purpose of the Mobile allocation information element is to provide that part of the RF channels belonging to the cell allocation (coded with a “1” in the cell channel description information element) which is used in the mobile hopping sequence. The Mobile allocation is a type 4 information element with 10 octets length maximal.

ISSUE 12 REVISION 0 Message Elements



5–xi


1. SCCP Reference Number

The SCCP reference number is defined to be unique per call and is used by the BSS to identify a call.

2. Local Cell Identifier

This element is used to identify the logical cell identity.

3. Transaction Number

This value is used in the Global reset message to keep track of the BTSs to which a Global reset message has been sent. The process must respond with an acknowledge which contains the same transaction number.

4. Carrier Number

This value is used to indicate the logical carrier number referenced.

5. Channel type

The channel type element is used to determine the type of channel request queued.

6. Trace Data

This element contains an information element identifier, length of trace data following and the trace data. This element is included in the trace response message.

7. Interference Band

This element contains an information element identifier, and both requested and current interference bands.

8. Audit Result

This element is included in the Audit Call Response message from the RRSM to the SSM and vice versa to give the CRM reason for deallocating the channel.

9. MSC or BSS Status

This element is included in the MSC Status message from the BSC to the BTS to give the BTS information on whether to send messages to the MSC or not.

10. Stats Cause

This element is included in the Radio Channel Released message to specify whether an Assignment Command has been sent to the mobile before the radio channel was released. This is used for stats collection purposes only.

11. Message Discriminator

The T-bit is set to 1 to indicate that the message is to be/was considered transparent by the BTS. All other messages shall have the T-bit set to 0.

12. Message Type

The Message Type uniquely identifies the function of the message being sent.

13. Handover Cause

The field is included in handover recognised and Force handover fields. This field is included to indicate the reason for initiating a handover for the specified mobile.




5–xii

14. Candidate Cells

This field is included in the Handover Recognised message to indicate the candidate cells for a handover.

15. Trace Mode

This field is included in Trace Request message.

5) MessageElements definedby Motorola

Motorola Confidential Proprietary

ISSUE 12 REVISION 0



5–i

Appendix B

ISSUE 12 REVISION 0BSC to BTS Interface (A-bis)



5–ii

BSC to BTS Interface (A-bis)

Exercise

1. Construct the Layer 2/Layer 3 message which has to be transmitted on the A-bisinterface from the BSC to the BTS to page mobile subscriber (IMSI=234101234567890). SAPI 0 is to be used and the TEI at the BTS is 3.

This message is the second to be transmitted on the A-bis for this link and the BSC/BSP is acknowledging all messages upto and including message 5.

The timeslot (TN) for the paging message to appear on is TN 2. The mobiles paging group is 4 (defined in TS GSM 05.02).

This transaction requires the use of an SDCCH.

For the purpose of this exercise the FCS is to be set at 1010111010111011.

2. Which message type will the BTS use on the A-bis link to the BSC in response tothe above command assuming the MS responds to the PAGING REQUEST?

ISSUE 12 REVISION 0 BSC to BTS Interface (A-bis)



5–iii

� � � � � � � � ��

� � � � � � � � ��

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � � �

� � � � � � �

ISSUE 12 REVISION 0BSC to BTS Interface (A-bis)



5–iv



i

Chapter 6

BSC–MSC Interface (A-interface)

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 6BSC–MSC Interface (A-interface) i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSC–MSC Interface 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Objectives 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-interface Capabilities 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-interface specification objectives 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-interface Characteristics 6–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GSM Specification 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 08.0x 6–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-Interface Functions 6–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling System No7 (C7) 6–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 6–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Messages Transfer Part (MTP) 6–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Level 2 Header Part 6–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LSSU Status Field Format 6–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alignment Procedure 6–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alignment Status Indications 6–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Signal Unit (MSU) 6–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Information Octet (SIO) 6–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Signalling Information Field (SIF) 6–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Routing Label 6–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signalling Connection Control Part (SCCP) 6–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 6–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Protocol Classes 6–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP Message Format 6–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Establishment Procedure 6–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP Message Parameters 6–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SCCP Message Example 6–36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Called/Calling Party Address Parameter 6–38. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Radio Subsystem Application Part (BSSAP) 6–40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSSAP Message Structure 6–42. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSSAP Message Header 6–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DTAP Header Structure 6–44. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP Header Structure 6–46. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSSAP Message Structure 6–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Complete Message Format 6–48. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS Management Application Part (BSSMAP) 6–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Procedures 6–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Normal Mobile Station (MS) to PSTN Call Set. 6–52. . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-Interface Messages 6–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Normal PSTN to MS Call 6–56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

A-Interface Messages 6–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Call from PSTN to MS 6–58. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures – Global 6–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blocking 6–60. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Circuit Procedures 6–62. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unblocking 6–64. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Resource Indication 6–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Resource Indication Procedure 6–66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Global Reset Procedure 6–68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset at the MSC 6–68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

Reset at the BSS 6–70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures – Global 6–72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset Circuit at the MSC 6–72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset Circuit at the BSS 6–72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paging 6–74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Candidate Enquiry 6–76. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flow Control 6–76. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Procedures – Dedicated 6–78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assignment 6–78. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Handover 6–80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Required Indication 6–80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Resource Allocation 6–80. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handover Execution 6–82. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Release 6–84. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classmark Update 6–86. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cipher Mode Control 6–88. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Initial MS Message 6–90. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Queueing Indication 6–92. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Timers 6–94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MTP Level 2 Timers 6–94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MTP Level 3 Timers 6–94. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BSSMAP Timers 6–95. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0 BSC–MSC Interface



6–1

BSC–MSC Interface

Objectives


� Identify the functions of the BSC–MSC Interface.

� State the GSM Recommendations which apply to the A-interface.

� Identify the Signalling Protocol Reference Model.

� State the various parts of the CCITT signalling system Number 7.

– Message Transfer Part (MTP)

– Signalling Connection Control Part (SCCP)

� Identify the procedure for SCCP establishment.

� State the structure of the BSS Application Part (BSSAP).

� Identify the Direct Transfer Application Part (DTAP) message type and structure.

� Identify the BSS Management Application Part (BSSMAP) procedures.

� Identify complete A-interface message flow.

ISSUE 12 REVISION 0Introduction



6–2

Introduction

A-interfaceCapabilities

The BSS–MSC interface shall be capable of supporting all the services offered to GSMusers and subscribers. In addition it also allows for the allocation of suitable radioresources within the PLMN, and the operation and maintenance of those resources.

A-interfacespecificationobjectives

The MSC to BSS interface specifications shall allow the following:

� Connection of various manufacturers BSSs to the same MSC

� The use of several manufacturers MSCs to the same type of BSS

� The use of the same BSS in any PLMN

� The use of the same MSC in any PLMN

� The separate evolution of MSC and BSS technology, and

� The separate evolution of O&M facilities

� Support of all services defined in the GSM 02 series of Technical Specifications

A-interfaceCharacteristics

The interface is defined to be at the boundary of the MSC.

The MSC to BSS interface is specified by a set of characteristics, including:

� Physical and electromagnetic parameters

� Channel structures

� Network operating procedures

� Operation and Maintenance information support

The definition of the MSC to BSS interface follows a layered approach similar to that inthe ISDN. Layer 3 is for the most part based on Technical Specification GSM 04.08 withadditional procedures added for the control of radio resources and the identification oftransactions using the SCCP. Layer 2 is based on the signalling system No.7 (SS No.7)Message Transfer Part (MTP). Layer 1 is either digital (at 2048 kbit/s, based on ITU–TSRec G703 section 6) or analogue with the data being passed by the use of modems (thislatter case is a national option).

ISSUE 12 REVISION 0 Introduction



6–3

MSC–BSS Interface (A-interface)

SYS01_6_2

PSTN

MSC BSS

BSS

MSC

BTS

BSC

BTS

A-interface(2.048 Mbit/s)

MS

MSMS

ISSUE 12 REVISION 0GSM Specification



6–4

GSM Specification

08.0x

The A-interface is defined in the 08.0X series of GSM specification, which is designed tosupport a wide range of possible architecture on both sides of the interface.

� 08.01 General Aspects

� 08.02 Interface Principle. This gives the functional split between the BSC and the MSC

� 08.04 Layer 1 (2 Mbit/s)

� 08.06 Signalling Transport Mechanisms(ITU–TS Signalling No7)

� 08.08 Layer 3 Specifications – BSSAP user part.– BSSOMAP user part

ISSUE 12 REVISION 0 GSM Specification



6–5

GSM Specification – A-Interface

� ��

� ��

� ��

� ��

� ��

ISSUE 12 REVISION 0A-Interface Functions



6–6

A-Interface FunctionsThe A-interface provides facilities to the traffic channels and signalling Links for thefollowing functions:

� Terrestrial management : allocation and blocking of terrestrial traffic channels.

� Radio channel Management : BSS Management – radio channelallocations/control.

� Mobility Management : location update – transparency between the MS andMSC.

� Call Control : setup for Mobile originating/terminating calls.

� Supplementary Services : transparency through the BSS.

The signalling is layered, similar to that in the OSI reference model, however the layersreferred to are not identical. They are specified by ITU–TS Signalling System No7 (C7).

Once a mobile is established on a channel, be it a traffic channel or control channel, allsignalling between the mobile and the MSC are transparent to the BSS software. All theBSS software undertakes is to maintain the channel to the mobile, whilst passing on anysignalling to the mobile. The BSS software does not track the identity of a mobile.

CLM= Connectionless Manager

SSM= SCCP State Machine

SM= Switch Manager

ISSUE 12 REVISION 0 A-Interface Functions



6–7

MSC–BSC Interface

SYS01_6_4

MSC(Call Control)

(MobilityManagement)

CLM SSM SM

MTP

(Radio Channel Management)

BTSBTS

BTS

PSTN

HLR

VLR

2 Mbit/s

ShortMessageService

SupplementaryServices

BSC

IntelligentNetwork

ISSUE 12 REVISION 0Signalling System No7 (C7)



6–8

Signalling System No7 (C7)

Introduction

The objective of Signalling System C7 is to provide an internationally standardizedgeneral purpose Common Channel Signalling (CCS) system which can:

� Be optimized for operation in digital communications networks with stored programcontrolled exchanges.

� Meet present and further requirements regarding speed, flexibility to handle newservices such as ISDN

� Provide a reliable means of transfer of information in correct sequence and withoutloss or duplication.

The signalling system is optimized for operation over a 64kbit/s digital channel. It is alsosuitable for operation over analogue channels at lower speeds and for point to point links.

The initial specification of C7 was based on circuit related telephony control requirementsand was specified in four functional levels, the MTP (Levels 1–3 Signalling Data Link,Link control and Signalling Network) and the User Part (Level 4). As new requirementshave emerged, C7 has also evolved to meet these new requirements.

The first was an additional sublayer, added on top of the MTP (the Signalling ConnectionControl Part SCCP) to obtain full OSI Layer 3 functionally.

The second is the addition of a common support function called Transaction Capabilities(TC).

TC forms two elements; Transaction Capabilities Application Part (TCAP) andIntermittent Service Part (ISP) (not yet defined). TCAP is a functional block residingabove the ISP. It supports the various TC users such as OMAP and MAP. (Operations,Maintenance and Administration Part (OMAP) – Mobile Application Part (MAP)).

BSS OMAP: Operation and Maintenance Application Part

BSSAP: BSS Application Part which is sub-divided into two separate functions:

� The Base Station Management Application Part (BSSMAP) , which supportsprocedures between the MSC and BSS related to the MS, or to a cell within theBSS, or to the whole BSS.

� The Direct Transfer Application Part (DTAP) , used to transfer Call Control (CC)and Mobility Management (MM) messages to/from the MS.

ISSUE 12 REVISION 0 Signalling System No7 (C7)



6–9

Signalling Protocol Reference Model

SYS01_6_5

SCCP

MTP

Physical Layer

OML

DTAP BSSMAP

SCCP

MTP

OML

DTAPMAP

A-interface

BSSAP BSSAP

Other applications e.g. call control

BSS side MSC side

Operation andMaintenanceinformation toPLMN O & M

To otherusers of theSCCP and

MTP

To other processeswithin the BSS

To air interfacetransmissionequipment

BSS

DTAP: Direct Transfer Application PartBSSMAP: BSS Management Application PartBSS OMAP: Operation and Maintenance Application PartSCCP: Signalling Connection Control PartMTP: Message Transfer PartBSS: Base Station SystemMSC: Mobile Services Switching Centre

Layer 4–7

Layer 3

Layer 1–3

OSIMODEL

Distribution functionDistribution function




6–10

MessagesTransfer Part(MTP)

Introduction

The MTP serves as a transport system for reliable transfer of messages between users.It is broken down into three levels which equate to Layers 1–3 of the OSI model.

Signalling Data Link defines the physical, electrical and mechanical interfacerequirements. (Recommendations ITU–TS Q.702). The standard signalling rate is64kbit/s and the basic digital interface would be a 4-wire line using AMI/HDB3 encoding.The signalling link being assigned to the time slot 16 in a 2048kbits digital path (this is atypical assignment due to Motorola’s design of the XCDR Board. The MTL may resideon any available TS).

Signalling Link Control defines the functions and procedures for the controlling of thetransfer of signalling messages over one individual signalling data Link (RecommendationITU–TS Q.703)

Signalling Network in principle defines these transport functions and procedures thatare common to and independent of the operation of individual signalling links(Recommendation ITU–TS Q.704)

The functions fall in to two main categories:

� Signalling Message Handling; which directs the message to the propersignalling Link or User part.

� Signalling Network Management; which controls the message routing and theconfiguration of the signalling network facilities.




6–11

Level Relationships

SYS01_6_6

BSS AP

SCCP(virtual circuit – call control)

Signalling Network(MTP L3)

Signalling Link Control

Signalling Data Link

(MTP L2)

(MSI CARD)

Physical Medium

Application

Level 4

Level 3

Level 2

Level 1

MessageTransfer

Part(MTP)




6–12

MessagesTransfer Part(MTP)

Signalling Unit Format

One of the fundamental concepts adopted for C7 is that of variable message length,where practically all messages are complete in themselves.

Each message consists of three main parts:

� Header

� Data User part; which may contain complete messages.

� Tail; Frame Check Sequence.

These messages are referred to as Signal Units (SU) of which there are three differenttypes.

� Message Signal Unit (MSU) – Used for passing of higher Level signalling data.

� Link Status Signal Unit (LSSU) – To enable the Level 2 MTP to be aligned andmaintain the link.

� Fill-in Signal Units (FISU) – If there are no MSU or LSSU to be passed along thelink, then a FISU is periodically sent to maintain the signalling link




6–13

C7 Signalling Unit Format

SYS01_6_7

TAIL DATA HEADER

FRAME CHECKSEQUENCE

(ERROR CHECKING)

DATA(MSU, LSSU, FISU)

SEQUENCE NUMBERLENGTH INDICATOR

SIGNALLING UNITS (SU)




6–14

Level 2 HeaderPart

The header sequence is the same for all types of Signalling Units (SU) and consists ofthe following:

Flag (F) – All SUs begin and end with an 8 bit flag. The flag bit pattern is 01111110. Theflag pattern is added by Level 2 before transmission. To ensure a flag pattern is notcontained in the data, a “0” is inserted after any 5 consecutive “1’s” at the transmitter. Atthe receiver, the “0” is removed. These processes are called “Bit Stuffing” and “BitStripping”.

Backward Sequence Number (BSN) – The BSN is the sequence number of an MSUbeing acknowledged.

Backward Indicator Bit (BIB) – Used with the BSN in the basic error control functionsto perform SU sequence control and acknowledgement.

Forward Sequence Number (FSN) – The FSN is the sequence number of the SU inwhich it is being carried. The FSN and BSN are binary coded number in the range0–127. The FSN and BSN in a particular SU bear no relationship to each other. TheFSN is only incremented when an MSU is transmitted.

Forward Indicator Bit (FIB) – Used with the FSN in the basic error control functions toperform SU sequence and acknowledgement.

Length Indicator (LI) – The length indicator field allows a cross-check on the closingflag and pre-allocation of buffer space (normal function of length indicator), the lengthindicator also provides the signal unit type.

� Message Signal Units have data portions larger than 2 octets.

� Link Status Units have a data field of one of two octets.

� Fill-in Signal Units have a length zero indicator.




6–15

MTP Level 2 Header Part

SYS01_6_8

SPAREBITS

LIFIB

FSNBIB

BSN FLAG

2 6 1 7 1 7 8

HEADER

Types of SUs:

LI = 0 – FISULI = 1 or 2 – LSSULI = >2 – MSU




6–16

LSSU StatusField Format

This field is used to indicate the senders view of the actual signalling status of the link.At present only a single octet Status Field (SF) is defined.

The first three bits of the Status Field are used, the remainder are spare.

C B A Indication

0 0 0 Status ‘O’ – Out of alignment0 0 1 Status ‘N’ – Normal alignment0 1 0 Status ‘E’ – Emergency alignment0 1 1 Status ‘OS’ – Out of Service1 0 0 Status ‘PO’ – Processor Outage1 0 1 Status ‘B’ – Busy (Level 2 congestion)

Procedure

Status Indicator ‘O’ is sent during the initial alignment until an LSSU indicating status ‘O’,‘N’ or ‘E’ is received ie until frame alignment.

Status Indication ‘N’ indicates normal operation.

Status Indication ‘E’ is used for emergency alignment with a short proving period at therequest of the network level.




6–17

LSSU Status Field

SYS01_6_9

TAIL Status Field HEADER

* * * * * BC A

Length Indicator = 1 or 2

Note: LSSUs have the highest priority of all signal units

* = Spare bits

8 bits




6–18

AlignmentProcedure

The procedure is applicable to activation and to restoration of the link. The procedureprovides a “normal” proving period for “normal” initial alignment and an “emergency”proving period for “emergency” initial alignment. The decision to apply either the“normal” or the “emergency” procedures is made unilaterally at Level 3. Only thesignalling link to be aligned is involved in the initial alignment procedure (i.e. no transferof alignment information over other signalling links is required).

Alignment StatusIndications

The initial alignment procedure employs four different alignment status indications:

� status indication “O”: Out of alignment

� status indication “N”: “Normal” alignment status

� status indication “E”: “Emergency” alignment status

� status indication “OS”: Out of Service

These indications are carried in the status field of the Link Status Signal Units

Status indication “O” is transmitted when initial alignment has been started and none ofthe status indications “O”, “N” or “E” are received from the link. Status indication “N” istransmitted when, after having started initial alignment, status indication “O”, “N”, or “E” isreceived and the terminal is in the “normal” alignment status. Status indication “E” istransmitted when, after having started initial alignment, status indication “O”, “N” or “E” iereceived and the terminal is in the “emergency” alignment status, i.e. it must employ theshort “emergency” proving period.

Status indication “N” and “E” indicate the status of the transmitting signalling link terminal;this is not changed by reception of status indications indicating a different status at theremote signalling link terminal. Hence, if a signalling link terminal with a “normal”alignment status receives a status indication “E” it continues to send status indication “N”but initiates the short “emergency”proving period.

Status indication “OS” informs the remote signalling link terminal that for reasons otherthan processor outage (e.g. link failure) the signalling link terminal can neither receive nortransmit message signal units. Status indication OS is sent on completion of “power on”until initial alignment is started.




6–19

Alignment Procedure

SYS01_6_10

BSS MSC

START T1 IDLE

Not aligned state

Start T2

Aligned state

Proving periodemergency or normal

Aligned ready state

T1 allows for up to fouradditional proving attempts

Stop T2

Start T3

Stop T3Start T4

T4 Expires

Stop T1

SIO

SIO

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

FISU/MSU

FISU/MSU




6–20

AlignmentProcedure

The alignment procedure passes through a number of states during the initial alignment:

� State Idle: the procedure is suspended

� State “not aligned”: the signalling link is not aligned and the terminal is sendingstatus indication “O”. Time-out T23 is started on entry to State and stopped whenState is left.

� State “aligned”: the signalling link is aligned and the terminal is sending statusindication “N” or “E”, status indications “N”, “E” or “OS” are not received. Time-outT3 is started on entry to State and stopped when State is left.

� State, “proving”, the signalling link terminal is sending status indication “N” or “E”,status indication “O” or “OS” are not received, proving has been started.

Proving is the means by which the signalling link terminal validates the link’s abilityto carry signal units correctly by inspecting the signal units. «Proving» must last fora period of T4 before the link can enter the «aligned ready» link state. Expiry oftimer T4 indicates a successful proving period unless the proving period has beenpreviously aborted up to four times.

� Following successful alignment and proving procedure, the signalling terminalenters Aligned Ready state and the aligned ready time-out T1 is stopped on entryin the In service state and the duration of time-out T1 should be chosen such thatthe remote end can perform four additional proving attempts.

The nominal values of the proving periods are:

Pn= 216 octets transmission time

Pe= 212 octets transmission time




6–21

Alignment Procedure

SYS01_6_10

BSS MSC

START T1 IDLE

Not aligned state

Start T2

Aligned state

Proving periodemergency or normal

Aligned ready state

T1 allows for up to fouradditional proving attempts

Stop T2

Start T3

Stop T3Start T4

T4 Expires

Stop T1

SIO

SIO

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

SIE or SIN

FISU/MSU

FISU/MSU




6–22

Message SignalUnit (MSU)

Level 3 of the C7 MTP provides the functions and procedures to control the transfer ofmessages between the nodes of the signalling network.

The functions can be divided into two basic categories.

� Signalling Message Handling

� Signalling Network Management – Not Used

Signalling Network Management includes the functions necessary to reconfigure theNetwork in the event of failure and to execute traffic flow control.

This facility is not implemented within the GSM A-interface, as only point-to-pointoperation is recommended. So the procedures for message re-routing are not required.

Signalling Message Handling ensures that the messages originated by a User Part aredelivered to the corresponding user part at the destination. These functions include,discrimination, distribution and routing.

The discrimination and distribution functions are controlled by the SCCP and will becovered later.




6–23

Message Signal Unit

SYS01_6_11

TAIL Data Field Level2

MTPSignalling InfoField

Service Info Octet

Message Signal Unit

ROUTINGLABELData HEADER

Data HEADER

Data

Level3

MTP

Level4

SCCP

BSSAP(DTAP or BSSMAP)




6–24

ServiceInformation Octet(SIO)

The service information octet only exists in Message Signal Units. It contains theService Indicator and the Subservice Field (network indicator).

The Service Indicator is assigned for each user within the message transfer part, this isthen used to indicate which user should receive the message.

The Subservice Field (network indicator) indicates if the traffic is national or international.

Service Indicator

D C B A Indication0 0 0 0 Signalling network management.0 0 0 1 Signalling network testing + maintenance0 0 1 0 Spare0 0 1 1 Signalling Connection Control Part (SCCP)0 1 0 0 Telephone User Part (TUP)0 1 0 1 ISDN User Part0 1 1 0 Data User Part (Call + cut related)0 1 1 1 Data User Part (facility registration and cancellation)1 0 0 0 MTP testing User Part1 0 0 1

to1 1 1 1 Spare

Sub-service Field

� � � � ��

� � � � ��

� � � � ��

� � � � ��

� � � � ��

��

��

��

Note: If “ni” (network identifier) is set incorrectly an error will occur giving an invalid SIO.




6–25

Service Information Octet – L3 Header

SYS01_6_12

BC A

Data Field

TAIL SIF SIO HEADER MTPLevel 2

A DBD C

SUBSERVICEFIELD

SERVICEINDICATOR

NOTE:1 . No Signalling Network Management in GSM A-interface signalling.

2. All messages via SCCP therefore,Service indicator set to D C B A(SCCP) 0

Subservice field set to D C B A(National network) 1 0 X X

1 10

8Bits




6–26

SignallingInformation Field(SIF)

The signalling Information Field (SIF) is only used in MSU’s and is the position for theactual signalling messages and accompanying routing information being transferredbetween signalling nodes.

The field includes a routing label and the message.

The routing label identifies the address of the destination to which the message is to betransferred. In the GSM application this is greatly simplified

The interface is only used for point-to-point application, so the routing function in theMTP will be preset to select the point code appropriate to the parent MSC.

Routing Label

The part of the message label directly used for routing is called the routing label. Thelabel is 32-bits, 4 octets in length and contains:

� 14-bit Destination Point Code (DPC)

� 14-bit Originating Point Code (OPC)

� 4-bit Signalling Link Selector (SLS)

The origination and destination point code identifies the signalling points e.g. BSS andMSC of the A-interface link.

The SLS identifies which MTL link to use.

Router Index

To improve the loadsharing of traffic on MTL links in the uplink direction from the BSS tothe MSC. (Loadsharing from the MSC to the BSC is based on the routing functionimplemented at the MSC and is beyond the scope of this course.)

This will be done by distribution of signalling traffic originating at the BSS across 64virtual circuits. A router index in the range of 0 to 63 will be randomly assigned to eachcall block when a call is established. Random assignment will result in even distribution ofrouting indices to call blocks. The router index identifies the virutal circuit for all signallingmessages associated wit the call block. The BSS MTP Layer 3 routing function willevenly distribute the 64 virtual circuits over the active MTLs. This routing function iscompliant with the SS7 protocol because the BSS still routes all messaging associatedwith a given call over the same physical MTL. Delivery of messages in order is stillguaranteed. A database element will be used for setting the loadshare granularity toeither 16 or 64.

Although the SLS will not be used to perform routing at the BSS, the SLS field will befilled in. The SLS may be used for message routing by the MSC or some other signallingpoint in the SS7 network.




6–27

Signalling Information Field

SYS01_6_13

Data Field

TAIL SIF SIO HEADER

MTPLevel 2

MTPLevel 3

Maximum 272 Octets

MESSAGE DATA ROUTING LABEL

Signalling LinkSelection (SLS)

Originating PointCode (OPC)

Destination PointCode (DPC)

4-bits 14-bits 14-bits

ISSUE 12 REVISION 0Signalling Connection Control Part (SCCP)



6–28

Signalling Connection Control Part (SCCP)

Introduction

The SCCP builds on the underlying MTP to provide a full network service as describedby the OSI architecture. The SCCP accepts message units from the higher layer users,adds value in the form of network service features and gives the enhanced messageunits to the MTP for delivery.

The SCCP provides two types of message transfer:

� Without logical signalling connection (connectionless transfer)

� With logical signalling connection (connection-oriented)

“Connectionless message transfer” is used to send single messages to other SCCPusers. The SCCP generates a UDT message from the user data and from thedetermined address. This is then transferred to the MTP for transmission.

“Connection-oriented message transfer” is used for an exchange of SCCP users.When the SCCP receives a request from a user to set up a signalling connection, itsends a Call Request (CR) message to the SCCP in the opposite signalling point. ThisCR message contains the local reference number, which is used to identify theconnection.

Protocol Classes

To satisfy a variety of requirements the SCCP provide four classes of protocol. Two areassociated with the connectionless service and two are connection-orientated.

Class 0– provides a pure connectionless transfer service.

Class 1– Sequenced (MTP) connectionless class.

Class 2– Basic connection-orientated class.

Class 3– Flow control connection-orientated class

GSM Recommendations allows only Classes 0 (BSSMAP messages) and Class 2 (DTAP+ BSSMAP messages)

ISSUE 12 REVISION 0 Signalling Connection Control Part (SCCP)



6–29

Signalling Connection Control Part (SCCP)

SYS01_6_14

ITU–TS Recom Q.711–Q.716Message Transfer

ConnectionlessConnection-orientated

Protocol Class 2(DTAP – BSSMAP messages)

Protocol Class 0(BSSMAP messages)




6–30

SCCP MessageFormat

The SCCP’s objective is to provide the means to establish logical signalling connectionswithin the C7 common channel signalling network.

Each SCCP message is a message in its own right, where each message uses therouting label of the MTP. The SCCP message format is as shown, consisting:

MESSAGE TYPE FIELD ; identifying one of 16 defined messages.

FIXED MANDATORY PART; This part includes a variable number of parameters each offixed length for a particular message type. The order of these parameters are defined foreach message type.

VARIABLE MANDATORY PART ; This part includes pointers to locate parameters in thevariable length field. The name of the parameters and the order of listing is definedwithin the message type.

OPTIONAL PART; If the message type allows an optional parameter field, the variablemandatory part will include a pointer to the optional part. The optional part is defined asparameter name, length of field and the parameter value.




6–31

SCCP Message Format

SYS01_6_15

TAIL SIF SIO HEADER MTPLevel 2

MTPLevel 3

SCCPLevel 4

MESSAGE DATA ROUTING LABEL

Optional Part(DTAP or BSSMAP)

VariableMandatory

Part

FixedMandatory

Part

MessageType




6–32

EstablishmentProcedure

A new connection is established when individual information related to a MS transactionhas to be exchanged between a BSS and MSC. This establishment can be initiated byeither the BSS or MSC.

If initiated by the BSS then the user data field of the SCCP Connection Requestmessage contains the BSSMAP message (COMPLETE L3 INFORMATION).

A typical establishment procedure is for a Connection Request (CR) message to be sent,the user data field may contain BSSMAP or DTAP messages.

After checking this message the connection confirm (CC) message is returned with theoption of containing BSSMAP or DTAP messages.

Connection Release procedure is always initiated by the MSC. The MSC sends a SCCPReleased (RLSD) message. The user data field of this message is optional and maycontain a transparent Layer 3 message to the MS or be empty.

When receiving this message, the BSS releases all the radio resources allocated to therelevant MS and sends a SCCP Release Complete (RLC) message back to the MSC.

The transfer of DTAP or BSSMAP data is via the data user field of the SCCP frames.This is optional in the Connection Request, connection confirm and released messages(except CR initiated by BSS). The user data field is a mandatory parameter of a Datamessage (DT1) which always contain either a DTAP or a BSSMAP message.

��

��

��

��




6–33

SCCP Establishment Procedure

SYS01_6_16

BSS MSC

(BSSMAP; DTAP) CR

CC (*)

(BSSMAP; DTAP) DTI

DTI (BSSMAP; DTAP)

RLSD (*)

RLC

(ssm_t_v_0)

* CC and RLSD has option for Data field




6–34

SCCP MessageParameters

Listed below is a brief description of each of the message parameters used with therelative message type, along with the number of octets for that parameter.

The overhead also shows if the parameter is used in the Fixed (F), Variable (V) orOptional (O) part of the message.

“Source Local Reference” , parameter field is a 3-octet field containing a referencenumber which is generated and used by the local node (BSS or MSC) to identify theconnection section.

“Destination Local Reference” parameter field is a 3-octet field containing a referencenumber which outgoing messages, has been allocated by the remote node (BSS orMSC)

“Protocol Class” parameter field is a four bit field containing the protocol class (i.e.Class 0 or 2 (connection-orientated/connectionless)).

“Called Party Address” and “Calling Party Address” parameters which identify thesub-system which messages are using.

“Segmenting/reassembling” parameter field is a 1-octet field and indicates if more datamessages, relating to this message are required (not used in A-interface however theparameter must be still included for syntax reasons).

“Refusal Cause” parameter field is a 1-octet field containing the reason for the refusal ofthe connection (full list ITU–TS Q.713 para 3.11)

“Data” parameter field is a variable length field containing SCCP user data to betransferred transparently between the SCCP user functions.

“End of Optional Parameter” identifies the end of all the optional parameters, a singleoctet set to all zeros.




6–35

SCCP Message Parameters

SYS01_6_17

Parameters

Source Local Reference

Destination Local Reference FF

33

Protocol Class F 1Called Party Address V 3 minCalling Party Address O 4 minSegmenting/reassembling F 1Refusal Cause F 1Release Cause F 1Data (DTAP/BSSMAP) O/V 3 min

256max

End of OptionalParameter

F = FixedV = VariableO = Optional

Type(F,V,O)

Length(Octets)

0 1




6–36

SCCP MessageExample

This example is a typical SCCP connect request message. It illustrates a connectrequest message that contains 3 fixed mandatory parameters:

� Message Type Code

� Source Local Reference

� Protocol Class (class 2)

One variable mandatory parameter:

� Called Party Address

Three optional parameters:

� Calling Party Address

� Data

� End of Optional Parameter

The mandatory variable part also contains two pointers:

� The first pointer indicates the start of the called party address parameter

� The second pointer indicates the start of the optional parameters

NOTE:

When the parameter is part of the Fixed or Variable Mandatory part of the message theparameter type code octet is not used. e.g. Called Party Address (Variable Mandatory) 3octets.

Calling Party Address (optional part) 4 Octets.




6–37

SCCP Message Example

SYS01_6_18

Message Type: Connection Request (CR)

PARAMETER CODE/INDICATION

Message Type

Source LocalReference

Protocol Class

Pointer to Variable

Pointer to optional

Called PartyAddress

Calling PartyAddress

Data

End of OptionalParameter

0000 0001

Incoming ConnectionIdentifier

0000 0010

0000 0100

Length IndicatorAddress IndicatorSubsystem Number

Parameter Type CodeLength IndicatorAddress IndicatorSubsystem Number

3 – 130 Octets

0000 0000

0000 0010

(CR)

CLASS 2

(2)

(4)

BSSMAP or DTAPmessage

FixedMandatory

Part

VariableMandatory

Part

OptionalPart




6–38

Called/CallingParty AddressParameter

In order to limit the complexity of the address procedures the BSS exchanges signallingmessages only with its parent MSC i.e. point-to-point working. Therefore, the addressparameters, both Calling and Called Party Address are structured identically. They areprimarily used to indicate the required application part and where to obtain the routinginformation.

The A-interface has no global title so the Destination Point Code (DPC) which is coded inthe MTP routing label and subsystem number in the Called Party Address allow therouting of the message.

The encoding of the address indicator is 01000010 with the subsystem number beingeither.

11111110 – – BSSAP

11111101 – – OMAP

Address indicator and subsystem number will always be the same in our messages. Forcalling and called party addresses are point to point routing provided with Level 3 (MTProuting label) OPC and DPC and national addressing (Ni= 2).




6–39

Called/Calling Party Address Parameter

SYS01_6_19

SUBSYSTEM NUMBER

ADDRESS INDICATOR

LENGTH INDICATOR 0 0 0 0 0 0 1 0

0 1 0 0 0 0 1 0

1 1 1 1 1 1 1 0 (BSSAP)

ISSUE 12 REVISION 0Radio Subsystem Application Part (BSSAP)



6–40

Radio Subsystem Application Part (BSSAP)The user function of the SCCP called Radio Subsystem Application Part (BSSAP) usesone signalling connection per active Mobile Station for the transfer of Layer 3 messagesrelated to that transaction. The BSSAP user function is further subdivided into twoseparate functions.

The Direct Transfer Application Sub-Part (DTAP) is used to transfer ConnectionManagement (CM) and Mobility Management (MM) messages to and from the mobilestation (MS). The Layer 3 information in these messages is not interpreted by the BSSand a complete description is contained in the GSM Recommendation 04.08.

The BSS Management Application Sub-Part (BSSMAP) supports other proceduresbetween the MSC and BSS related to the MS (i.e. resource management, handovercontrol), or to a cell within the BSS, or to the whole BSS. The description of the Level 3protocol for BSSMAP is contained in GSM Recommendation 08.08, with the Radioresource management contained in GSM Recommendations 04.08.

ISSUE 12 REVISION 0 Radio Subsystem Application Part (BSSAP)



6–41

BSS Application Part (BSSAP)

SYS01_6_20

ConnectionManagement

(CM)

Mobility Management(MM)

Radio ResourceManagement

(RR)GSM 04.08

BSS ManagementBSSMAP

GSM 08.08

Short MessageService (SMS)

Call Control(CC)

SupplementaryService Support

(SSS)

Direct TransferApplication Part

(DTAP)GSM Rec 04.08

BSS Management Part(BSSMAP)

ISSUE 12 REVISION 0BSSAP Message Structure



6–42

BSSAP Message StructureThe distribution of messages between BSSMAP and DTAP functions are performed byan intermediate layer of protocol between the BSSAP and SCCP. This is referred to asthe Distribution Sub-layer.

Each SCCP User Data Field contains a distribution data unit as a header, followed by theLevel 3 BSSMAP or Layer 3 transparent DTAP message.

The discrimination parameter indicates which message type is transparent ornon-transparent

ISSUE 12 REVISION 0 BSSAP Message Structure



6–43

BSSAP Message Structure

SYS01_6_21

TAIL MTP

Message Signal Unit

Mandatory

MESSAGETYPE

Variable FixedOptional(Data) SCCP

END

TransportLayer 3 Message(TS GSM 04.08)

DTAPHeader

Information Elements(TS GSM 04.08 and 08.08)

BSSMAPHeader

either/or

ISSUE 12 REVISION 0BSSAP Message Header



6–44

BSSAP Message Header

DTAP HeaderStructure

The discriminator is one octet in length and discriminates between DTAP and BSSMAPtype messages. For DTAP messages the D bit (bit 1 of the octet) is set to 1.

The DLCI parameter is used by the MSC messages to indicate to the BSS the type ofData Link Connection to be used over the Air-interface. This is a single octet, whichindicates the radio channel identification and the SAPI value used on the radio link.

The LI states the number of octets remaining in the message.

DTAP Message Format:

� Discriminator parameter

� Data link connection identification parameter

� Length indicator

� Message (Information elements)

ISSUE 12 REVISION 0 BSSAP Message Header



6–45

DTAP Header Structure

SYS01_6_22

LI(1 Octet)

DLCI(1 Octet)

DISC(1 Octet)

3 Octets

1 Octet

“D” bit = “1”

C 1 C2 00 0 S 1 S 2 S 3

Data Link Connection Identification (DLCI)

C1, C2 = 00 = FACCH, SDCCHC1, C2 = 01 = SACCHS1, S2, S3 = 000 = Call Control

011 = Short Message Service

ISSUE 12 REVISION 0BSSAP Message Header



6–46

BSSMAP HeaderStructure

The BSSMAP messages are to support the MSC to BSC interface and thus do notrequire any DLCI field. All messages apply only to the connected MSC/BSC.

The first octet, discriminator, indicates by the first bit, being set to a 0, that the messagecontained within this MSU is a BSSMAP type.

This is then followed by an octet indicating the length of the Level 3 message.

BSSMAP Message Format:

� Discriminator parameter

� Length indicator

� Message (Information elements)

ISSUE 12 REVISION 0 BSSAP Message Header



6–47

BSS Management Application Part Header

SYS01_6_23

MessageLength

IndicatorDISC

2 Octets

“D” bit = 0

ISSUE 12 REVISION 0BSSAP Message Structure



6–48

BSSAP Message Structure

CompleteMessage Format

The Direct Transfer Application Part is used to transfer Call Control (CC) and MobilityManagement (MM) messages to and from the MS. These messages are transferred viathe A-interface in the format shown but the information in these messages are notinterpreted by the BSS at all, except in one case (stated below).

The actual messages are defined in GSM Recommendation 04.08, of these messagesthe Radio Resource (RR) Management type are not transferred over the A-interface.

The initial MS message received by the BSS will be analysed to allow the extraction, bythe BSS, of the “Classmark field” (mobile capabilities). The entire initial message (e.g.CM service request, LOC update request, page response, re-establishment request) ispassed to the MSC piggybacked on the “complete layer 3 information” message.

The BSS uses the “Classmark” information to set timing and power requirements for theAir-interface.

Note:

LI= Length Indicator

DISC= Discriminator

ISSUE 12 REVISION 0 BSSAP Message Structure



6–49

BSSAP Message Format

SYS01_6_24

Message Signal Unit

MTPLevel 2

MTPLevel 3

SCCPMessage

(DT1)

CKFSignal Information

FieldSIO LI

FIB

FSNBIB

BSN F

DPCOPCSLSSCCP Message

DTAP Message(TS GSM 04.08)

LI DLCI DISC = 1

End ofMessage

Optional(Data)

VariableMandatory

FixedMandatory

MessageType

DTAPMessage

BSSMAP Message(TS GSM 08.08)

Message Type LI DISC = 0 BSSMAPMessage

ISSUE 12 REVISION 0BSS Management Application Part (BSSMAP)



6–50

BSS Management Application Part (BSSMAP)

Procedures

The BSSMAP supports all procedures between the MSC and BSS that requireinterpretation and processing of information related to single calls and resourcemanagement.

There are a total of 18 procedures defined in GSM Recommendations 08.08 which canbe defined into two groups.

“Global” ; these procedures concern a complete cell/BSS, they use the connectionlessservices of the SCCP (e.g. UDT).

These procedures are defined within GSM Recommendation 08.08 separately, to enablea more flexible approach to the buildup of complete call sequence.

Global procedures include:

� Blocking/Unblocking

� Resource Indication

� Reset

� Reset Circuit

� Paging

� Handover Candidate Enquiry

� Flow Control

“Dedicated” ; these procedures concern a single dedicated radio resource on theradio-orientated services of the SCCP, thus the connection has to be set up to supportthe call or transaction.

The procedures are defined separately but in many instances the procedures can existsimultaneously.

Dedicated procedures include:

� Assignment

� Handover Required Indication

� Handover Resource Allocation

� Handover Execution

� Release

� Classmark Update

� Cipher Mode Control

� Initial MS Message

� Queuing Indication

� Trace Invocation

� DataLink Control SAPI not equal to 0

ExternalHandover

ISSUE 12 REVISION 0 BSS Management Application Part (BSSMAP)



6–51

BSSMAP

SYS01_6_25

PROCEDURES (18 Total)GSM Recom 08.08

DEDICATED(single radio resource)Connection–orientated

GLOBAL(complete cell/BSS)

Connectionless

Blocking/UnblockingResource Indication

ResetReset Circuit

PagingHandover Candidate Enquiry

Flow Control

AssignmentHandover Required IndicationHandover Required Allocation

Handover ExecutionRelease

Classmark UpdateCipher Mode ControlInitial MS MessageQueueing Indication

Trace InvocationData Link Control SAPI not Equal to 0

ISSUE 12 REVISION 0BSS Management Application Part (BSSMAP)



6–52

Normal MobileStation (MS) toPSTN Call Set.

The CM service request message (DTAP) is enveloped into Connection Request (CR)(SCCP) message.

* When the Alerting message is received by the MS this generates the ringing tone in theMS, indicating the distant-end phone is ringing. Ring tone may be sent from the distantexchange.

ISSUE 12 REVISION 0 BSS Management Application Part (BSSMAP)



6–53

MS to PSTN Call

SYS01_6_26

Message Flow Type

MSC : BSS

CR – ComL3inf (CM service request)

CC – (SCCP) [BSSMAP/DTAP]

DT1 – Cipher Mode Command (BSSMAP)

DT1 – Cipher Mode Complete (BSSMAP)

DT1 – Set up (DTAP)

DT1 – Call Proceeding (DTAP)

DT1 – Assignment Complete (BSSMAP)

DT1 – Assignment Request (BSSMAP)

DT1 – Alerting (DTAP)

DT1 – Connect (DTAP)

DT1 – Connect Ack (DTAP)

ISSUE 12 REVISION 0A-Interface Messages



6–54

A-Interface MessagesNormal Mobile Station (MS) to PSTN call setup when call is cleared.

ISSUE 12 REVISION 0 A-Interface Messages



6–55

MS Clears Call

SYS01_6_27

Message Flow Type

MSC : BSS

DT1 – Disconnect (DTAP)

DT1 – Release (DTAP)

DT1 – Release Complete (DTAP)

DT1 – Clear Command (BSSMAP)

DT1 – Clear Complete (BSSMAP)

RSLD – Released (SCCP)

RLC – Release Complete (SCCP)

ISSUE 12 REVISION 0Normal PSTN to MS Call



6–56

Normal PSTN to MS CallThe paging request message (BSSMAP) is enveloped into a Unit Data (SCCP) messageand the BSS generates the required paging message over the air-interfaceBCCH/CCCH. The call set up is then similar to an MS originated call except for thePaging Response message (DTAP) enveloped into the ComL3inf message (BSSMAP)enveloped into the Connection Request (SCCP).

ISSUE 12 REVISION 0 Normal PSTN to MS Call



6–57

Normal PSTN to MS Call

SYS01_6_28

Message Flow Type

MSC : BSS

UDT – Paging (BSSMAP)

CR – ComL3inf (Paging Response) (BSSMAP/DTAP)

CC – (SCCP)

DT1 – Cipher Mode Command (BSSMAP)

DT1 – Cipher Mode Complete (BSSMAP)

DT1 – Set up (DTAP)

DT1 – Assignment Complete (BSSMAP)

DT1 – Assignment Request (BSSMAP)

DT1 – Alerting (DTAP)

DT1 – Connect (DTAP)

DT1 – Connect Ack (DTAP)

DT1 – Call Confirmed (DTAP)

ISSUE 12 REVISION 0A-Interface Messages



6–58

A-Interface Messages

Call from PSTNto MS

After the conversation either party can clear down, which is indicated by eitherDisconnect or Release.

ISSUE 12 REVISION 0 A-Interface Messages



6–59

PSTN User Clears Call

SYS01_6_29

Message Flow Type

MSC : BSS

DT1 – Disconnect (DTAP)

DT1 – Release (DTAP)

DT1 – Release Complete (DTAP)

DT1 – Clear Command (BSSMAP)

DT1 – Clear Complete (BSSMAP)

RSLD – Released (SCCP)

RLC – Release Complete (SCCP)

Example: Call Cleared

#

# can be with release message

ISSUE 12 REVISION 0Procedures – Global



6–60

Procedures – Global

Blocking

The assignment procedure depends upon the MSC choosing the terrestrial resource tobe used. The MSC therefore needs to be informed of any terrestrial circuits that are outof service at the BSS. This is performed by using a simple blocking/unblockingprocedure. The block messages used to support this procedure are sent as globalmessages (i.e. using the SCCP connectionless mode). Each message refers to one ormore terrestrial circuits accessed through the BSS MSC interface. The circuit isidentified by its Circuit Identity Code.

A BSS may block a terrestrial circuit because:

� Operation and Maintenance intervention makes the circuit unavailable for use(Cause value: “O and M intervention”).

� An equipment failure makes the circuit unavailable (Cause value: “equipmentfailure”)

� Radio resource is not accessible from the terrestrial circuit (Cause value: “no radioresource available”).

When and if the BSS decides to block a terrestrial circuit, the BSS shall immediatelymark that terrestrial circuit as “blocked” (to stop any further allocation of that terrestrialcircuit) and shall then send a block message to the MSC and start timer T1 (T20).

The BLOCK message contains the Circuit Identity Code indicating the terrestrial circuitthat is to be blocked and a Cause Information Element indicating the reason for blocking.Typical Cause values are: “no radio resources available,” “O and M intervention”,“equipment failure”.

If the CIRCUIT GROUP BLOCK message is applied by the BSS the circuits to beblocked are indicated in the status field of the Circuit Identity Code list.

Receipt of a block message (BLOCK or CIRCUIT GROUP BLOCK) at the MSC from theBSS will indicate to the MSC that the identified circuits are unavailable for reselection. Ifa call is in progress on any of the identified terrestrial circuits then it will be unaffected bythis procedure, the circuits will however be “camp on blocked”. Such circuits shall beblocked as soon as that call is no longer in progress, or active.

An appropriate blocking acknowledge message (BLOCKING ACKNOWLEDGE orCIRCUIT GROUP BLOCKING ACKNOWLEDGE) will be returned to the BSS by theMSC to acknowledge receipt of the block message and to indicate that any necessaryaction has been taken.

On receipt of the blocking acknowledge the BSS shall stop timer T1 (T20).

The resource involved will be assumed to be blocked by the MSC until either an unblock(UNBLOCK or CIRCUIT GROUP UNBLOCK) or RESET message is received relevant tothat resource.

ISSUE 12 REVISION 0 Procedures – Global



6–61

Blocking

SYS01_6_30

Informs the MSC of terrestrial circuits that are out of service at the BSS.

Blocking

StartedT1 (T20)

StoppedT1 (T20)

BSS MSC

(BLOCK) UDT

UDT (BLOCKING ACK)

CIC = x

CIC = xCause = Equipment fail

StartedT1 (T20)

StoppedT1 (T20)

BSS MSC(Circuit Group Block) UDT

(Circuit Group BlockAcknowledge) UDT

OR




6–62

Blocking

If blocking acknowledge message is not received for a block message within T1 (T20)seconds then the block message will be repeated. If this occurs a second time thecircuits will be kept marked as blocked, and the situation must then be resolved internallywithin the BSS or by O&M procedures.

It should be noted that this is a unidirectional procedure and that the MSC does not sendblock messages towards the BSS. If the MSC wishes to take a terrestrial circuit out ofservice this is achieved by local blocking within the MSC

Note: Timer T1 is used to supervise a single circuit block/unblock procedure whilst T20is used to supervise the circuit group block/unblock procedure.

If an ASSIGNMENT REQUEST or HANDOVER REQUEST message is receivedallocating a circuit which is marked at the BSS as blocked then an ASSIGNMENTFAILURE message or a HANDOVER FAILURE message (respectively) followed by aBLOCK message shall be sent to the MSC.

Group CircuitProcedures

Allows reduced messages across the A-interface. Faster completion of procedures isachieved by implementing group messages throughout the BSS software.

To enable this function within the BSS the following change_element command must beentered at the BSC:

chg_element group_block_unblock_allowed <element_value><bsc or 0)

<element_value> 0: Disable – the BSS sends single circuit Block/Unblock messages to the MSC.

1: Enable – the BSS sends Circuit Group Block/Unblock messages to the MSC.

To indicate support of group block/unblock at the BSC the following command must beentered at the RXCDR:

chg_rxcdr_gbu <bsc><bss_grp_block_unblock_allowed>

<bsc> Represents the BSC associated with this RXCDR Range: 0–31

<bss _grp _block _unblock _allowed> off:BSC does not support Group block/unblockon: BSC does support Group block/unblock




6–63

Blocking

SYS01_6_30

Informs the MSC of terrestrial circuits that are out of service at the BSS.

Blocking

StartedT1 (T20)

StoppedT1 (T20)

BSS MSC

(BLOCK) UDT

UDT (BLOCKING ACK)

CIC = x

CIC = xCause = Equipment fail

StartedT1 (T20)

StoppedT1 (T20)

BSS MSC(Circuit Group Block) UDT

(Circuit Group BlockAcknowledge) UDT

OR




6–64

Unblocking

If the BSS wishes to unblock a blocked circuit and return it to service then it shallimmediately mark the circuit as “unblocked” and then send an unblock message, andstart timer T1 (T20).

If an unblock message (UNBLOCK or CIRCUIT GROUP UNBLOCK) is received at theMSC for a blocked resource then the resource will be marked as available for service andan unblocking acknowledge message (UNBLOCKING ACKNOWLEDGE or CIRCUITGROUP UNBLOCKING ACKNOWLEDGE) will be returned to the BSS. The BSS shallstop timer T1 (T20) on receipt of this unblocking acknowledge.

If an unblocking acknowledge message is not received for an unblock message beforeexpiry of timer T1 (T20) then the unblock message will be repeated. If this occurs asecond time, this situation may be reflected to the O&M, which shall resolve the possibleconflict. The unblocking acknowledge message is repeated at most one time. Whateverthe outcome of possible repetitions, the concerned circuits remain “unblocked”.




6–65

Unblocking

SYS01_6_31

Informs the MSC of terrestrial circuits which require unblocking and returningto service.

StartedT1 (T20)

StoppedT1 (T20)

BSS MSC

(UNBLOCK) UDT

UDT (UNBLOCKING ACK)

BSS MSC

(Circuit Group Unblock) UDT

(Circuit Group UnblockAcknowledge) UDT

CIC = Circuit Identity Code

Unblocking




6–66

ResourceIndication

The purpose of the resource indication is to inform the MSC of the amount of radioresources that are spare at the BSS and available for carrying traffic. This informationmay be used by the MSC for external handover decisions.

The procedure is for the MSC to indicate to the BSS one of the four methods oftransferring the required information to the MSC. This is achieved by the MSC sending aResource Request message containing the required method and the cell identity.

The four methods are:

� “Spontaneous indication expected”; when conditions defined by O+M are met inthe BSS (e.g. traffic thresholds, or time interval between two messages).

� “Single indication expected”; immediate one-off response.

� “Periodic indication expected”; immediately then periodically, set by MSC (100mSintervals)

� “No indication expected”; BSS to MSC transfer of resource indication informationdisabled until receipt of Resource Request

The resource indication message contains two pieces of information for each of the 5interference bands:

# The number of half rate traffic channels available in each band.

# The number of full rate traffic channels available in each band.

The level of the 5 bands are defined by O+M (user).

ResourceIndicationProcedure

A change_element command has been introduced to enable this message to eitherreport using the Phase 1 or Phase 2 message formats. In addition an acknowledgemessage with no information in the response to the Resource Request from the MSC isintroduced.

chg_element phase 2_resource_ind_allowed<element_value><bsc or 0>

<element_value> 0: Disabled – (default) the BSS sends Resource Indication messages to the MSC in the GSM phase 1 format.

1: Enabled – the BSS send the resource Indication messages to the MSC in the GSM phase 2 format.




6–67

Resource Indication

SYS01_6_32

Informs the MSC of the amount of radio resources that are available at the BSS.

BSS MSC<UDT, Resource Request>

<UDT, Resource Indication>

<timeout>

Phase2_resource_ind_allowed=0

BSS MSC<UDT, Resource Request>



<timeout>

Phase2_resource_ind_allowed=1

(acknowledgementwith information)

Method:

1. Spontaneous indication expected

2. Single indication expected

3. Periodic indication expected

4. No indication expected – Disable reporting




6–68

Global ResetProcedure

The purpose of the reset procedure is to initialise the BSS and MSC in the event of afailure. The procedure is a global procedure applying to a whole BSS, and therefore allmessages relating to the reset procedure are sent as global messages using theconnectionless mode of the SCCP.

If only a limited part of the MSC or BSS has suffered a failure then clearing procedurescan be used to clear only those affected calls.

Reset at the MSC

In the event of a failure at the MSC which has resulted in the loss of transactionreference information, a RESET message is sent to the BSS. This message is used bythe BSS to release affected calls and erase all affected references.

Upon receipt of a RESET message from the MSC the BSS shall send block messages(BLOCK or CIRCUIT GROUP BLOCK) for all circuits that were previously blocked, theMSC shall respond to these with blocking acknowledge messages.

After a guard period of T13 seconds a RESET ACKNOWLEDGE message is returned tothe MSC, indicating that all MSs which were involved in a call are no longer transmittingand that all references at the BSS have been cleared.

If the MSC sends a RESET message to the BSS and receives no RESETACKNOWLEDGE message within a period T16 then it shall repeat the entire resetprocedure. The sending of the RESET message is repeated a maximum of “n” timeswhere n is an operator matter. After the n-th unsuccessful repetition the procedure isstopped and the maintenance system is informed.




6–69

Reset

SYS01_6_33

MSC

UDT (RESET)

UDT (BLOCK)

UDT (CIRCUIT GROUP BLOCK)

UDT (BLOCKING ACKNOWLEDGE)

UDT (CIRCUIT GROUP BLOCKINGACKNOWLEDGE)

UDT (RESET ACKNOWLEDGE)

T13 STARTED

T13 EXPIRES

T16 STARTED

T16 EXPIRES

BSS MSC

Max of “N” times for Reset Message

ISSUE 12 REVISION 0Reset at the BSS



6–70

Reset at the BSSIn the event of a failure at the BSS which has resulted in the loss of transaction referenceinformation, a RESET message is sent to the MSC. This message is used by the MSCto release affected calls and erase all affected references, and to put all circuits into theidle state.

After a guard period of T2 seconds a RESET ACKNOWLEDGE message is returned tothe BSS indicating that all references have been cleared.

After the sending of the RESET to the MSC the BSS shall initiate blocking procedures(Block or Circuit group block procedures) for all circuits that are blocked, the MSC shallrespond with blocking acknowledge or check group block acknowledge. The sending ofblock messages shall be done without waiting for the acknowledgement to the RESETmessage.

If the BSS sends a RESET message to the MSC and receives no RESETACKNOWLEDGE message within a period T4 then it shall repeat the entire resetprocedure. The sending of the RESET message is repeated a maximum of “n” timeswhere n is an operator matter. After the n-th unsuccessful repetition the procedure isstopped and the maintenance system is informed.

To specify the number of repetitions the following change_element command must beused.

chg_element global_reset_repetitions <element_value><bsc or 0>

<element_value> 0: The Global Reset Message will repeat continuously until a reset acknowledge is received.

1 to 255: The Global Reset Message will be repeated thenumber of times entered and the alarm “No MSCAcknowledgement” for Global Reset is generated.

ISSUE 12 REVISION 0 Reset at the BSS



6–71

Reset

SYS01_6_34

BSS

UDT (RESET)

UDT (BLOCK)

UDT (CIRCUIT GROUP BLOCK)

UDT (BLOCKING ACKNOWLEDGE)

UDT (CIRCUIT GROUP BLOCKINGACKNOWLEDGE)

UDT (RESET ACKNOWLEDGE)

T2 STARTED

T2 EXPIRES

T4 STARTED

T4 EXPIRES

MSC BSS

Max of “N” times for Reset Message




6–72

Procedures – Global

Reset Circuit atthe MSC

If a circuit has to be put to idle at the MSC due to an abnormal SCCP-connectionrelease, a RESET CIRCUIT message will be sent to the BSS. When the BSS receives aRESET CIRCUIT message, it shall respond with a RESET CIRCUIT ACKNOWLEDGEmessage in case the circuit can be put to idle. If the circuit is blocked at the BSS aBLOCK message shall be returned to the MSC. the MSC shall then respond with aBLOCKING ACKNOWLEDGE message. If the circuit is unknown at the BSS, the BSSshall return an UNEQUIPPED CIRCUIT message to the MSC.

Timer T12 is used at the MSC to supervise the reset circuit procedure. If the Timerelapses before a response (RESET, RESET CIRCUIT ACKNOWLEDGE, UNEQUIPPEDCIRCUIT or BLOCK) the reset circuit procedure is repeated.

Reset Circuit atthe BSS

If the circuit to be put to idle at the BSS due to an abnormal SCCP-connection release, aRESET CIRCUIT message will be sent to the MSC. When the MSC receives thismessage, it clears the possible call and puts the circuit, if known, to the idle state. if thecircuit is known, a RESET CIRCUIT ACKNOWLEDGE message is returned to the BSS.if the circuit is unknown in the MSC, an UNEQUIPPED CIRCUIT message is returned tothe BSS.

Timer T19 is used at the BSS to supervise the reset circuit procedure. if the timerelapses before a response (RESET, RESET CIRCUIT ACKNOWLEDGE orUNEQUIPPED CIRCUIT) is returned to the BSS, the procedure is repeated.

If the BSC receives a message for a circuit identity code that is unequipped then it mayrespond with an unequipped circuit message. To enable this function the followingchange_element command has to be enabled.

chg_element unequipped_circuit_allowed<element_value><bsc or 0>

<element_value> 0: Disabled (default) the BSS shall not send UnequippedCircuit messages to the MSC id Unknown circuit Identity code is received.

1: Enabled the BSS shall send Unequipped Circuit messagesto the MSC.

Note:

This parameter does not apply to RXCDR sites. This parameter requires a location of 0 or BSC.This parameter is used with a Phase 2 optional feature which must be purchased.




6–73

Reset Circuit

SYS01_6_35

BSS MSCT12 STARTED

T12 STOPPED ONRECEIPT OF:RESET CIRCUIT ACKRESETBLOCK UNEQUIPPEDCIRCUIT

UDT (RESET CIRCUIT)CIC = Y

(RESET CIRCUIT ACK) UDTCIC = Y

(BLOCK) UDT

UDT (BLOCK ACK)

(UNEQUIPPED CCT)

MSC

BSS MSCT19 STARTED

(RESET CIRCUIT) UDTCIC = x

UDT (RESET CIRCUIT ACK)CIC = x

UNEQUIPPED CIRCUIT

BSS

OR




6–74

Paging

PAGING messages for all MSs shall be sent via the BSSMAP as a connectionlessmessage. These will include the IMSI of the MS to allow derivation of the pagingpopulation number; they also include an indication of which combination of channels willbe needed for the subsequent transaction related to the paging. This type of PAGINGmessage will then be stored and a corresponding radio interface paging messagetransmitted over the radio interface at the appropriate time.

It should be noted that each PAGING message on the MSC–BSS interface relates toonly one MS and therefore the BSS has to pack the pages into the relevant TechnicalSpecification GSM 04.08 radio interface paging message.

If a radio interface PAGING RESPONSE message is received then the relevantconnection is set up towards the MSC as described in Technical Specification GSM08.06 and the radio interface PAGING RESPONSE message is passed to the MSC in aCOMPLETE LAYER 3 INFORMATION message.

A single PAGING message across the MSC to BSS interface contains information onthe cells in which the page shall be broadcast.




6–75

Paging

SYS01_6_36

MS

Contacting Mobile Stations:

BSS MSC

PAGING BROADCAST

TMSI = Y

PAGING RESPONSE

UDT (PAGING)

IMSI = XTMSI = YCELL Identifier

(COML3INF) CRPAGING RESPONSE




6–76

HandoverCandidateEnquiry

The purpose of this procedure is to allow the MSC to ascertain if it is possible tohandover any MSs that are currently being served by a particular cell to anothernominated cell. The procedure uses both global and dedicated resource messages, andis relevant to an individual cell.

Flow Control

These procedures are defined to give some degree of flow control.

At the BSS, the BSS processor or CCCH scheduler can indicate overload.

The MSC can indicate to the BSS that it is in a congested state by sending an overloadmessage.

MSC Overload

If the MSC becomes overloaded, it shall send an OVERLOAD message from the MSC tothe BSS. The BSS receives this message and starts to reduce traffic loading on the MSCimmediately. The BSS reduces the traffic load on the MSC by barring of mobile accessclasses within cells in the BSS. When a mobile access class is barred a group of mobileusers are no longer allowed to make calls on the network and hence the load to the MSCis reduced. This mobile access class information is carried to the mobile subscriber in theSYSTEM INFORMATION message specified in GSM recommendations.




6–77

Handover Candidate Enquiry

SYS01_6_37

BSS MSCHANDOVER CANDIDATE ENQUIRY

HANDOVER REQUIRED

HANDOVER REQUIRED

HANDOVER REQUIRED

HANDOVER CANDIDATE RESPONSE

Note:Receipt of the Handover Candidate Enquiry message causes the generation of a HandoverRequired message for each of candidate MS. These are sent as connection orientatedmessages. When all Handover Required messages have been generated a globalHandover Candidate response message is returned.

MSC Overload

SYS01_6_38

MSCBSSMS

OVERLOAD

OVERLOAD

OVERLOAD

OVERLOAD

(MSC OVERLOAD)

(BSS OVERLOAD)

ISSUE 12 REVISION 0Procedures – Dedicated



6–78

Procedures – Dedicated

Assignment

The purpose of the assignment procedure is to ensure that the correct dedicated radioresource can be allocated or re-allocated to a mobile as required. However, the initialrandom access by the MS and “immediate assignment” to a DCCH is handledautonomously by the BSS without reference to the MSC.

The initial SETUP procedure (A-bis) has been assumed to have taken place. E.g. theMSC has been told type of call; channel required; dialled number etc by the MS.

Then based on this information, an Assignment Request message is sent to the BSS.This message contains details of the resource that is required e.g. speech rate, channeltype, data adaption priority level etc, it also contains the terrestrial channel that should beused between the MSC and BSS.

When the BSS is satisfied that the radio Assignment procedure has been successfullyaccomplished (e.g. receipt of assignment complete) via Air-interface, it will return anAssignment Complete message to the MSC.

If the assignment procedure fails for any reason, an Assignment Failure message will bereturned, containing the appropriate cause value.

ISSUE 12 REVISION 0 Procedures – Dedicated



6–79

Assignment

SYS01_6_39

MS BSS MSC

DT1 (ASSIGN. REQUEST)

CHAN TYPE

START T10 Speech ratechannel typedata adaptionpriority level

STOP T10(ASSIGN COMPL) DT1

ASSIGN CMD

(SDCCH)(Channel = FACCH)

SABM (FACCH)

UA (FACCH)

ASSIGN COMP

(FACCH)

The purpose of the assignment procedure is to allocate the correct radioresource to an MS.

If procedure fails, an Assignment Failure message is returned,containing an appropriate cause value.




6–80

ExternalHandover

This procedure supports handover transitions to and from both DCCH and trafficchannels. The defined procedures which can be used are:

� Handover Required Indication

� Handover Resource Allocation

� Handover Execution

HandoverRequiredIndication

The Handover Required Indication procedure allows an BSS to request that a handoverbe carried out for a particular mobile, currently allocated a dedicated resource.

This is done by generating a Handover Required message from the BSS to MSC. Thismessage contains the following information.

� Message Type

� Cause for Handover (e.g. downlink quality)

� Response Request (response required for completion)

� Preferred List of Target Cells

� Source Cell

HandoverResourceAllocation

This procedure allows the MSC to request that resources be reserved at a targetBSS/cell for a subsequent handover. However, it does not result in the transmission ofany messages over the radio interface.

In order to support this procedure a SCCP connection is set up to the BSS and is thenused to support all relevant BSSAP messages.

The MSC sends a Handover Request message (piggybacked on SCCP CR message) tothe BSS from which it requires radio resources.

This message contains an indication of the type of channel and the terrestrial circuit to beused for the traffic channel.

The BSS after allocating the required resources sends a Handover Requestacknowledge message containing the appropriate channel and the radio interfaceHANDOVER COMMAND message to the MSC.

The Handover Command message contains all the information the MS requires toaccess the new cell/BSS and is passed to the MS via the MSC and current source BSS.Part of this information is the Handover reference number which is to ensure the currentMS accesses the new BSS radio resource.




6–81

Handover Resource Allocation

SYS01_6_40

MSCBSS

Target (new)

CR (Handover Request)

Channel Type Encryption InfoCIC etc.

(Handover Request Ack) CC

Handover Command(Handover Reference Number)

This procedure allows the MSC to request that resources be reserved at thetarget cell/BSS for a subsequent handover.




6–82

HandoverExecution

The MSC instructs the MS to handover to the target BSS using the “HandoverCommand” previously generated by the target BSS.

A Handover Command message is generated by the MSC and sent to the current sourceBSS on which the concerned MS is connected.

Upon receiving the Handover Command message, the BSS starts timer T8. A HandoverCommand message is then sent by the BSS to the concerned MS. This message mustcontain the handover reference number previously allocated by the target BSS

The timer T8 is used to initiate the BSS clear sequence. The T8 is reset when either theMS returns to the source BSS (due to handover failure) or the MSC send a ClearCommand (handover complete).

Following reception of the Handover Command the MS accesses the target BSS:

� The BSS checks the handover reference number to ensure that it is the same asexpected.

� If it is as expected ( the reference number), it is passed to the MSC.

� When the MS is successfully in communications, it will send a handover completemessage to the BSS, which is passed to the MSC.

The MSC sends the Clear Command to the old source BSS, to release the radioresources.

If target BSS, or the MS are unable to establish a connect, or Timer T8 is expires thenthe MS returns to the original BSS and the handover failure message is sent to the MSC.

The handover shows the complete Handover procedure:

Handover Required Indication

ËËËË�

Handover Resources Allocation

ËËËËËËËËË

�

Handover Execution 3

ËËËËËË

�




6–83

Handover Procedure

STS01_6_41

MSTargetBSS MSC

SourceBSS

(Handover Required)DT1

DT1 (Handover Command)

1

2

3

Handover Command

Set T8Access

(FACCH)

Establish Air–Interface

Handover Complete

DT1 (Clear Command)

(Clear Command) DT1Reset T8

(Handover Detect) DT1

(Handover Complete) DT1

CR (Handover Request)

(Handover Request Ack) CC




6–84

Release

The release procedure is to inform the BSS that the assigned radio resources andterrestrial resources should be released.

This procedure can be initiated by the BSS, where the BSS generates a Clear Requestmessage to the MSC. The MSC then initiates the same release procedure.

Before the MSC initiates the MSC/BSS release it must have carried out the MSC/MSrelease procedure using the transparent messages via the DTAP protocol.

The MSC will then send a BSSMAP Clear Command indicating that the radio resourceshould be released and the cause of the release (e.g. handover successful).

When the BSS receives this clear command, the clearing of the radio resources iscarried out. When completed it then sends a clear complete message to the MSC. TheMSC then releases the assignment terrestrial resources.

The MSC initiates the SCCP connection release by sending a SCCP Released (RSLD).

The BSS returns the SCCP Release Complete RLC to the MSC.




6–85

Release

SYS01_6_42

The release procedure informs the BSS that the assigned radioresource should be released.

The BSS can initiate this procedure by sending Clear request to the MSC.

MSCBSS

DT1 (CLEAR COMMAND)

Cause = ?Chan Rel

MS

DISC

(FACCH)

UA

SET T10 CIC = Xetc.

(CLEAR COMPLETE) DT1

RLSD

RLC

ReleaseTerrestrialResources




6–86

ClassmarkUpdate

The classmark is a way GSM have defined the types of MS that can be connected to thenetwork. (e.g. vehicle and portable, portable or handheld). This will obviously have abearing on the air-interface connection.

Also these MS equipments may be altered (e.g. portable becomes vehicle while makinga call).

The BSS must be able to inform the MSC of a classmark update, when this is receivedfrom a MS. This message contains information on several transmission parametersrelevant to the MS.

This procedure will normally only be used where the power class of a MS change whilstthe MS has a dedicated resource.

Note:

To enable the MSC to initiate a command enquiring a chg_element command has beenintroduced at the BSC.

The new command enables the use of commands enquiry over the A-interface andsupports the MOBILE STATION CLASSMARK 3 MESSAGE (classmark 3 elementindicates the support of the additional encryption algorithms A5/4–A5/7

chg_element phase2_classmark_allowed<element_value><bsc or 0>

<element_value> 0: Disabled (default) the BSS shall send only classmarkssupported in GSM phase 1 to the MSC.

1: Enabled the BSS shall send classmarks supported in GSM Phase 2 to the MSC (includes classmark 3).




6–87

Classmark Update

SYS01_6_43

The BSS uses this procedure to inform the MSC of a MS classmark change.

MS BSS MSC

MS BSS MSC

CLASSMARK CHANGE

DCCH(SACCH)

(CLASSMARK UPDATE) DT1

DATA REQUEST

(CLASSMARK ENQUIRY)

DATA INDICATION

(CLASSMARK CHANGE)

DT1

(CLASSMARK REQUEST)

DT1

(CLASSMARK UPDATE)




6–88

Cipher ModeControl

The cipher mode control procedure allows the MSC to pass cipher mode information tothe BSS to select and load the user data and signalling encryption device with theappropriate key.

This is achieved by sending the BSS a Cipher Mode Command message. Receipt of themessage at the BSS will invoke the encryption device and generate the Cipher ModeCommand message via the radio interface.

Receipt of the Cipher Mode Complete message via the air-interface is used internally bythe BSS to achieve air-interface synchronisation.

When this has been achieved a cipher mode complete message is returned to the MSC.

If in the cipher_mode_command from the MSC the cipher response mode is present andit indicates that the International Mobile station Equipment Identity (IMEI) must beincluded by the mobile, then the BSC shall request in the ciphering mode command themobile station to include its IMEI in the ciphering mode complete message.

Phase 2 GSM recommendations introduced A5/2 encryption algorithm (place holdersexist for additional A5 algorithms) if in the cipher mode command the MSC requests theBSS to use an A5 algorithm that it does not support the BSS shall return a cipher modereject message with the cause clue “Ciphering Algorithm not Supported”. Also, a ciphermode reject will be returned to the MSC if the MSC requests a change of cipheringAlgorithm when ciphering is already active.

Note:

1. To enable the use of the cipher mode reject message at the BSC thechg_element command must be used

chg_element ciph_mode_rej_allowed<element_value><bsc or 0>

<element_value> 0: Disabled the BSS shall not sent Cipher mode reject messages to the MSC.

1: Enabled the BSS may send Cipher Mode Reject messages to the MSC.

2. The MSC must also support CIPHER_MODE_REJECT.




6–89

Cipher Mode Control

SYS01_6_44

MS BSS MSC

MS BSS MSC

CIPHERING MODE COMMAND

SACCH

The procedure allows the MSC to pass cipher mode information to the BSS (and MS).

CIPHERING MODE COMPLETE

SDCCH

DT1 (CIPHER MODE COMMAND)

CIPHER MODE COMPLETE

DT1 (CIPHER MODE COMMAND)

(CIPHER MODE REJECT) DT1

CAUSE VALUE = CIPHERINGALGORITHM NOT SUPPORTED




6–90

Initial MSMessage

The initial L3 message from the MS which has to be passed to the MSC is receivedpiggybacked on the Set Asynchronous Balanced Mode (SABM) frame. This could beCipher Mode (CM)-Service Request, page response, re-establishment request, Locationupdate request.

Whichever message type the BSS needs to carry out two basic requirements:

� perform SCCP connection to the MSC to enable the passing of the message.

� analyse part of the MS information to enable correct connection to the MS.

Enabling the BSS to analyse the message to a level which allows the extraction of theclassmark information. However the entire initial message is also passed to the MSC,using a “Complete Layer 3” information message. This message is piggybacked on tothe SCCP Connection Request (CR) message.

This is a one-off procedure, as all other messages between MSC and MS use the DTAPtransparent protocol.




6–91

Initial MS Message

SYS01_6_45

BSS required to carry out two actions:

Initial Layer 3 message from MS is analyzed by the BSS to extract the ClassmarkInformation, before passing to the MSC.

� Maintain (radio resource) link to MS.

� Establish SCCP connection to MSC.

MSCBSSMS

Access Burst

RACHImmediate Assignment

AGCHSABM

SDCCHUA

SDCCHComplete L3 Information

(CM SERV) CR

CC

CM SERV.REQ = CM Service Request




6–92

QueueingIndication

The purpose of the queueing indication procedure is to inform the MSC about a delay inthe necessary dedication radio resources.

This procedure is only relevant for Traffic Channels (TCH) assignment and /or forhandover of Traffic Channels (TCH).

After receiving the assignment request message but without the necessary TCHresources available the message is put into a queue. The queueing indication messageis sent to the MSC and a timer T11 set.

If T11 expires before the necessary resources become available an Clear requestmessage is returned to the MSC.

The procedure is terminated with a successful assignment of the traffic channel bysending an assignment complete.




6–93

Queueing Indication

SYS01_6_46

To inform the MSC about a delay in allocation of the necessay dedicated

radio resources.

MSCBSSMS

DT1 (ASSIGN. REQUEST)

No Resources

Start T11(Queueing Indication) DT1

Resources Available

ASSIGN CMD

ASSIGN CMP

(ASSIGN. COMPL) DT1

CLEAR REQUESTT11 Expires

ISSUE 12 REVISION 0Timers



6–94

TimersThe concept of timers is to ensure that an action/response that is required to beperformed is carried out in the correct sequence and in the required time. If thesystem/process fails to carry out this action/response before the timer set has expired,then this generates another sequence of events, normally release/reset (indicated byfailure message).

Within the GSM system there are a number of different levels of timers, most of whichhave to be defined.

The most critical within the A-interface are Message Transfer Part (MTP) Level 2 andLevel 3 timers.

MTP Level 2Timers

T1 Timer “alignment ready”

T2 Timer “not aligned”

T3 Timer “aligned”

T4 Proving period timer= 216 or 212 octet transmission time

T5 Timer “sending SIB”

T6 Timer “remote congestion”

T7 Timer “excessive delay of acknowledgement”

PE Emergency proving period

PN Normal proving period

MTP Level 3Timers

T1 Delay to avoid message mis-sequencing on changeover

T2 Waiting for changeover acknowledgement

T3 Time controlled diversion – delay to avoid mis-sequencing on changeback

T4 Waiting for changeback acknowledgement (first attempt)

T5 Waiting for changeback acknowledgement (second attempt)

T6 Delay to avoid message mis-sequencing on controlled rerouting

T7 Waiting for signalling data link connection acknowledgement

T8 Transfer prohibition timer (transient solution)

T9

T10 Waiting to repeat signalling route set test message

T11 Transfer restricted timer

T12 Waiting for uninhibit acknowledgement

T13 Waiting for force uninhibit

T14 Waiting for inhibition acknowledgement

T15 Waiting to start signalling route set congestion test

T16 Waiting for route set congestion status update

T17 Delay to avoid oscillation of initial alignment failure and link restart

ISSUE 12 REVISION 0 Timers



6–95

BSSMAP Timers

There is a number of timers defined with the GSM Recommendation 08.08 for thepassage of BSSMAP messages. The actual time is set by the system Operations andMaintenance with the system data base. A complete list of timers in the BSSMAPprocedures is as follows:

Timer Title LOC

T1: Time to receipt of blocking ack BSS

T2: Reset guard period at the MSC MSC

T3: Resource indication periodicity BSS

T4: Time to return of Rest Ack BSS

T5: Overload timer MSC/BSS

T6: Overload timer MS/BSS

T7: Handover required periodicity BSS

T8: Time to receipt of successful handoverinformation BSS

T10: Time to return of Assignment Completeor Assignment Failure form MS BSS

T11: Maximum allowed queuing time BSS

T12: Time to receipt of Reset Cit Ack MSC/BSS

T13: Reset guard period at the BSS BSS

T16: Time to return of Reset Ack at the MSC MSC

Tqho: Maximum allowed queuing time forhandover BSS

ISSUE 12 REVISION 0Timers



6–96

ISSUE 12 REVISION 0



6–i

Appendix A

ISSUE 12 REVISION 0Appendix A – MSC to BSC Interface (A-interface)



6–ii

Appendix A – MSC to BSC Interface (A-interface)

Exercise

Construct, using flow diagrams, the message sequence for a Mobile to Mobile call, wherethe originating Mobile has the capacity of encryption.

The Network carries out complete authentication for each subscriber before allowingaccess to the system.

For this particular call setup the two individual Mobiles are on the same BSC but are heldon different BTS cells.

Your answer should include the BSSAP message type, SCCP message type and inwhich direction the message is being passed over the MSC–BSC interface.

ISSUE 12 REVISION 0 Appendix A – MSC to BSC Interface (A-interface)



6–iii

��

ISSUE 12 REVISION 0Appendix A – MSC to BSC Interface (A-interface)



6–iv

ISSUE 12 REVISION 0



6–i

Appendix B

ISSUE 12 REVISION 0Appendix B – MSC–BSS Message Types



6–ii

Appendix B – MSC–BSS Message Types

DTAP Messages

The “A” interface carry’s DTAP messages as defined in TS GSM 04.08. A summary ofthe message types is listed below for Call Control and Mobility Management.

Messages for Circuit-switched call control

Call establishment messages: TS GSM 04.08 Reference

ALERTING 9.3.1CALL CONFIRMED 1) 9.3.2CALL PROCEEDING 9.3.3CONNECT 9.3.5CONNECT ACKNOWLEDGE 9.3.6EMERGENCY SETUP 1) 9.3.8PROGRESS 9.3.17SETUP 9.3.23

Call Information phase message: TS GSM 04.08 Reference

MODIFY 1) 9.3.13MODIFY COMPLETE 1) 9.3.14MODIFY REJECT 1) 9.3.15USER INFORMATION 9.3.31

Call Clearing messages TS GSM 04.08 Reference

DISCONNECT 9.3.7RELEASE 9.3.18RELEASE COMPLETE 9.3.19

Messages for supplementary service control: TS GSM 04.08 Reference

FACILITY 9.3.9HOLD 1) 9.3.10HOLD ACKNOWLEDGE 1) 9.3.11HOLD REJECT 1) 9.3.12RETRIEVE 1) 9.3.20RETRIEVE ACKNOWLEDGE 1) 9.3.21RETRIEVE REJECT 1) 9.3.22

Miscellaneous messages: TS GSM 04.08 Reference

CONGESTION CONTROL 9.3.4NOTIFY 9.3.16START DTMF 1) 9.3.24START DTMF ACKNOWLEDGE 1) 9.3.25START DTMF REJECT 1) 9.3.26STATUS 9.3.27STATUS ENQUIRY 9.3.28STOP DTMF 1) 9.3.29STOP DTMF ACKNOWLEDGE 1) 9.3.30

ISSUE 12 REVISION 0 Appendix B – MSC–BSS Message Types



6–iii

BSSMAP

Below is a list of the Radio Resource and BSSMAP messages used on the A-Interface.The message types are defined in TS GSM 04.08 (Radio Resource) and TS GSM 08.08(BSSMAP).

Messages for Radio Resources management

Channel establishment messages: TS GSM 04.08 Reference

ADDITIONAL ASSIGNMENT 9.1.1IMMEDIATE ASSIGNMENT 9.1.18IMMEDIATE ASSIGNMENT EXTENDED 9.1.19IMMEDIATE ASSIGNMENT REJECT 9.1.20

Ciphering messages: TS GSM 04.08 Reference

CIPHERING MODE COMMAND 9.1.9CIPHERING MODE COMPLETE 9.1.10

Handover messages: TS GSM 04.08 Reference

ASSIGNMENT COMMAND 9.1.2ASSIGNMENT COMPLETE 9.1.3ASSIGNMENT FAILURE 9.1.4HANDOVER ACCESS 9.1.14HANDOVER COMMAND 9.1.15HANDOVER COMPLETE 9.1.16HANDOVER FAILURE 9.1.17PHYSICAL INFORMATION 9.1.28

Channel release messages: TS GSM 04.08 Reference

CHANNEL RELEASE 9.1.7PARTIAL RELEASE 9.1.26PARTIAL RELEASE COMPLETE 9.1.27

Paging messages: TS GSM 04.08 Reference

PAGING REQUEST TYPE 1 9.1.22PAGING REQUEST TYPE 2 9.1.23PAGING REQUEST TYPE 3 9.1.24PAGING RESPONSE 9.1.25

ISSUE 12 REVISION 0MSC–BSS Message Types



6–iv

MSC–BSS Message Types

BSSMAP

Messages for Radio Resources management

System Information messages: TS GSM 04.08 Reference

SYSTEM INFORMATION TYPE 1 9.1.31SYSTEM INFORMATION TYPE 2 9.1.32SYSTEM INFORMATION TYPE 2bis 9.1.33SYSTEM INFORMATION TYPE 3 9.1.34SYSTEM INFORMATION TYPE 4 9.1.35SYSTEM INFORMATION TYPE 5 9.1.36SYSTEM INFORMATION TYPE 5bis 9.1.37SYSTEM INFORMATION TYPE 6 9.1.38SYSTEM INFORMATION TYPE 7 9.1.39SYSTEM INFORMATION TYPE 8 9.1.40

Miscellaneous messages: TS GSM 04.08 Reference

CHANNEL MODE MODIFY 9.1.5CHANNEL MODE MODIFY ACKNOWLEDGE 9.1.6CHANNEL REQUEST 9.1.8CLASSMARK CHANGE 9.1.11CLASSMARK ENQUIRY 9.1.12FREQUENCY REDEFINITION 9.1.13MEASUREMENT REPORT 9.1.21SYNCHRONIZATION CHANNEL INFORMATION 9.1.30RR STATUS 9.1.29

BSSMAPMessages

Message Name: TS GSM 08.08 Reference

ASSignment REQuest 3.2.1.1Assignment COMplete 3.2.1.2BLOck 3.2.1.3BLocking Acknowledge 3.2.1.4circuit group block 3.2.1.41circuit Group blockING acknowledge 3.2.1.42circuit group unblock 3.2.1.43circuit group unblockING acknowledge 3.2.1.44CLear command 3.2.1.21CLear COMplete 3.2.1.22CLear REQuest 3.2.1.20UnBLOck 3.2.1.6UnBLocking Ack 3.2.1.7HaNDover CaNDidate ENQuirE 3.2.1.14

ISSUE 12 REVISION 0 MSC–BSS Message Types



6–v

BSSMAPMessages

HaNDover CaNDidate RESponse 3.2.1.15HaNDover REQuest 3.2.1.8HaNDover ReQuireD 3.2.1.9HaNDover ReQuired Reject 3.2.1.37HaNDover ReQuest ACKnowledge 3.2.1.10HaNDover COMmand 3.2.1.11HaNDover CoMPlete 3.2.1.12HaNDover FaiLuRe 3.2.1.16HaNDover PerForMed 3.2.1.25HaNDover DETect 3.2.1.40RESource REQuest 3.2.1.17ReSeT 3.2.1.23ReSeT ACK 3.2.1.24RESource indication 3.2.1.18Paging 3.2.1.19Overload 3.2.1.26MSC Invoke trace 3.2.1.27BSS Invoke trace 3.2.1.28Classmark update 3.2.1.29CLASSMARK REQUEST 3.2.1.46Cipher Mode Command 3.2.1.30Cipher Mode Complete 3.2.1.31Cipher mode Reject 3.2.1.48Complete layer 3 information 3.2.1.32Queing indication 3.2.1.33SAPI “n” reject 3.2.1.34Reset circuit 3.2.1.38Reset circuit acknowledge 3.2.1.39CONFUSION 3.2.1.45UNEQUIPPED CIRCUIT 3.2.1.47

ISSUE 12 REVISION 0MSC–BSS Message Types



6–vi



i

Chapter 7

BSS–OMCR Interface (OML)

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 7BSS–OMCR Interface (OML) i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS–OMCR Interface 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS–OMCR Interface (OML) 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Motorola Application Layer 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . File Transfer 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Event/Alarm Reporting 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Remote Login 7–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OMC–BSS Interconnection 7–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OML 7–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

X.25 Layers 7–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 7–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Physical Link Layer 1 7–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Data Link Layer 2 7–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overview 7–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Address Field 7–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Frame Types – Control field encoding 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

X.25 Packet Level Protocol (PLP) 7–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Packet Header 7–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Logical Channel Numbers (LCN) 7–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Packet Type Identifier (PTI) 7–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Packet Types 7–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Additional Fields 7–30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OMC to BSS Communication DTE Addresses 7–32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Virtual Call Setup Procedure 7–34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

ISSUE 12 REVISION 0 BSS–OMCR Interface



7–1

BSS–OMCR Interface

Objectives


� State the BSS–OMCR configurations available.

� Identify the structure of the X.25 layers.

� Identify the Layer 2 (data link) parameter.

� Identify the X.25 packet level protocol.

� State the procedure for establishing a X.25 call.

ISSUE 12 REVISION 0BSS–OMCR Interface (OML)



7–2

BSS–OMCR Interface (OML)

Introduction

The OMC communications requirements are via specific protocols derived from the OSINetwork Management Model.

The main Management interface between the OMC and the BSS is based on Motorolaapplications protocols, with CCITT X.25 protocols used as the bearer.

These protocols are used to transfer all Operations and Maintenance data between theOMC and the BSS.

The application protocols are:

� File Transfer

� Event/Alarm reporting

� Remote Login

At the BSC the DTE address determine which default timeslots/2Mbit/s links weterminate the OML on.

BSC

0 MSI slot 16 Port 0 TS 1 Cage 0




RXCDR

0 MSI 10 Port 0 TS 1 Cage 0




ISSUE 12 REVISION 0 BSS–OMCR Interface (OML)



7–3

OMC-R Connections

SYS01_7_2

BSCMSI

MSI

MSI

RXCDR

OMC–R

2 Mbit/s Link

OML (XCDR) OML (BSC)

2 Mbit/s Link

ISSUE 12 REVISION 0Motorola Application Layer



7–4

Motorola Application Layer

File Transfer

Files can be transferred from the OMC to BSS and vice versa.

This protocol supports uploading of network element software and data. For example,backing-up databases, collecting statistics, up-grading Base Station software.

Event/AlarmReporting

This protocol provides a BSS with a mechanism for informing the OMC of changes inoperational conditions. For example:

� the start of an alarm condition

� an indication that a statistics file is ready for collection.

Remote Login

Remote Login allows the OMC to access the MMI of a network element.

The OMC uses this protocol to transfer information between an MMI session at the OMCand an MMI session at the Base Site.

With the introduction of Software 1.4.1.0 it is now possible to have up to 4 simultaneousRemote Login sessions at a BSS, each to a different GPROC.

The GPROCs are selected on a round-robin basis, with no GPROC having priority overany other.

ISSUE 12 REVISION 0 Motorola Application Layer



7–5

External Communications: OMC to NE

SYS01_7_3

SYSTEM PROCESSORF

ILE

TR

AN

SF

ER

EV

EN

T/A

LAR

MR

EP

OR

TIN

G

RE

MO

TE

LOG

IN T

O B

SS

MM

I

X.25 PLP

X.25 HDLC(LAP–B)

X.21 bis

X.25 Packet Switch

NE1 NE2 NE64

2 Mbps link

64Kb port interface

ApplicationServices

X.25

7

6

5

4

3

2

1

OSILayers

APPLICATION

PRESENTATION

SESSION

TRANSPORT

NETWORK

DATA LINK

PHYSICAL

ISSUE 12 REVISION 0OMC–BSS Interconnection



7–6

OMC–BSS InterconnectionConnections from the OMC to the BSS can be made via two methods.

� Public/Private X.25 networks using the A-interface (MSC–BSC). Normally via theRemote Transcoder, where the OML’s are multiplexed on to a 2 Mbit/s Link beforethe X.25 network.

� A dedicated 2 Mbit/s link to the BSS using one TS.

ISSUE 12 REVISION 0 OMC–BSS Interconnection



7–7

External Communications: OMC to BSS

SYS01_7_4

OMCSYSTEMPROCESSOR

O & M DataPackets

MULTIPLEXER

V.35 connections(seven physicalconnections)

NAILED CONNECTIONS(ONE PER O&M TIMESLOT)

BSS n

64 Kb/sO&M

TIMESLOT

2 MB link

64 Kb/sO&M

TIMESLOT

2 MB link

2 MB link

RXCDR

BSS 1

BSS 2 BSS 3BSS 4

PSDN – Public Switched Data Network

PSDNMSC

2 MB link

2 MB link2 MB link

2 MB link

X.25PACKETSWITCH

BSS1

ISSUE 12 REVISION 0OML



7–8

OMLThe download of software from the OMC to the BSC can take considerable time, todecrease this download time dual OML downloading is supported, provided the followingprovisions are met.

� Two 2 Mbit/s links are required

� Two DTE addresses are required (one per link)

� Conventional code download only

� BSS executes in ROM

� Two GPROCs to support PLP processes

If the above conditions are met then the download time is reduced by approximately40%.

If only one code object is to be downloaded then there is no saving.

Code objects are not shared across the X.25 links, therefore there is no height if onlyone code object is to be downloaded.

The OML can now carry out 8 simultaneous uploads.

ISSUE 12 REVISION 0 OML



7–9

Dual OML Download (BSC)

SYS01_7_5

OMCR

RXCDR

MSI MSI

(Transparent toBSCs OMLs)

PLPAGENT

IP

GPROC

PLPAGENT

GPROC

TDMHIGHWAY

ISSUE 12 REVISION 0X.25 Layers



7–10

X.25 Layers

Introduction

The X.25 protocol specifies the format and protocols necessary to transfer informationbetween DTE and DCE nodes for packet mode terminals connected to Public DataNetwork (PDN). It conforms to Layers 1, 2 and 3 of the OSI model.

Data Circuit-terminating Equipment (DCE) – The modem or digital interface that links tothe data communications network.

Data Terminal Equipment (DTE) – Any type of data communication equipment accessingthe network.

Virtual circuit – A connection between DTE’s through the network. The connection is notreally patched through but packets are routed from one DTE to the other DTE by thenetwork. More than one virtual circuit can exist on the physical link.

There are two types of virtual circuits – permanent (PVC) and switched (SVC). TheOMC software does not handle PVCs only SVCs.

ISSUE 12 REVISION 0 X.25 Layers



7–11

X.25

SYS01_7_6

DTE

DTE

PDN(Public Data Network)

X.25 X.25

– interface between DTE and DCE for packet mode terminals connected to Public Data Network (PDN).

DTE = Data Terminal EquipmentDCE = Data Circuit–terminating Equipment

DCE

DCE

ISSUE 12 REVISION 0X.25 Layers



7–12

Physical LinkLayer 1

The hardware characteristics that control the physical line between the DTE and the DCEconforms to (ITV) X.21 bis.

The OMC–BSS Link can be linked via the X.25 network to a MSI/XCDR on a BSC orRXCDR with Time slot 1 allocated on the 2Mbit/s link.

ISSUE 12 REVISION 0 X.25 Layers



7–13

X.25 Layers

�!,)"��$��"%#��,�(��

��")��+)��&��*�*&��))��

�&$*� ��"%��,��%��

�&%%��*"&%��"%��,��

�+%�*"&%�$�'"%��!�(��*�(")*"�)��"%��"%��

�!,)"��$�'&(*��&%%��*"&%��

ISSUE 12 REVISION 0Data Link Layer 2



7–14

Data Link Layer 2

Overview

This describes how data being carried between DTE and DCE is protected againsterrors. A bit-orientated protocol, a subset of High-level Data Link Control (HDLC)Asynchronous Balanced Mode, called Link Access Procedure Balanced (LAPB) definesthe frame envelope to carry the data across the physical link with a high degree of errorand flow control.

The basic frame structure of the LAPB frame is very similar to the LAPD frame coveredin Section 3 (A-bis interface). Only the differences will be covered in this section.

ISSUE 12 REVISION 0 Data Link Layer 2



7–15

Frame Structure – Layer 2

��

��

��

� ��

� ��

� ��

SYS01_7_8

FLAG FLAGINFORMATION CONTROL ADDRESSFRAME CHECKSEQUENCE




7–16

Address Field

The address field is a single octet as only two address are required within X.25.

� DTE address 03 hex

� DCE address 01 hex

All frames are either a Command or Response frame on each Link.




7–17

Address Field

��

��

�� SYS01_7_9

Command – 01 hex

Response – 01 hex

Command – 03 hex

Response – 03 hex

DTE DCE




7–18

Frame Types –Control fieldencoding

There are three types of frames:

I-frame carries a packet for Layer 3, this is always a command, which must be acknowledged.

S-frame Manages flow of I-frames, usually a response, contains N(R) for acknowledgment.

U-frame Used to start and stop Layer 2 activity.

# Exchange of SABM + UA opens Link; N(S) is set to 0 at each end.

Exchange of DISC + UA closes Link.

P/F: P=0 in ‘normal’ circumstances no hurry to respond.

P=1 demands an immediate response ie. reduces window size to one.

F in response must match P in command to which it relates.

# Only required from DTE (BSS) to DCE (OMC)

Control Field

Bit/s 1 or 1 and 2 determine which type of frame is being transmitted.

If supervisory frame then bits 3 and 4 determine which type of supervisory frame is beingtransmitted.

If unnumbered frame then bits 3, 4, 6, 7 and 8 determine which type of unnumberedframe is being transmitted.

bit 5 is always the “P” or “F” flag.

Bit 6. 7 and 8 for “I” and “S” frames is coded as N(R)

Bits 2, 3 and 4 for the “I” frame is coded as N (S)




7–19

Control Field Encoding

SYS01_7_10

FORMAT COMMAND RESPONSE ENCODING

PN(R) 0I (Information)Information

transfer

Supervisory

Unnumbered

RR(Receive Ready)

RR(Receive Ready)

RNR (ReceiveNot Ready)

RNR (ReceiveNot Ready)

REJ(Reject)

REJ(Reject)

SABM (SetAsyn Bal Mode)

DISC(Disconnect)

DM(Disconnect Mode)

UA(Unnumb Ack)

FRMR (Frame Rej)

1

1

1

1

1

1

0

1

1

1

1

1

0

1

0

1

0

1

0

1

1

0

1

0

0

P/F

P/F

P

P

F

F

F

1

0

0

1

0

0

1

0

1

0

0

0

0

0

1

N(R)

N(R)

8 7 6 5 4 3 2 1

N(S)

0 0 1

N(R) P/F 0 1 0 1

ISSUE 12 REVISION 0X.25 Packet Level Protocol (PLP)



7–20

X.25 Packet Level Protocol (PLP)Deals with the final end-to-end control procedure known as the PLP (Packet LevelProtocol) Layer describing packet formats and control procedures for the exchange ofdata between the BSS and the OMC. A packet is the smallest unit of informationoriginated and X.25 protocol stipulates that all packets will consist of whole numberoctets. The number of octets transmitted within each packet depends on the packettype, the minimum length being 3 octets (the header). The X.25 protocol allows packetlengths of up to 1024 octets, but has been set at a maximum length of 128 octets, withinthe OMC-R system.

The packet format can be divided into a packet (control) header (Level 3) and data block,which forms the information field within the I-frame (Level 2).

ISSUE 12 REVISION 0 X.25 Packet Level Protocol (PLP)



7–21

X.25 Packet Level Protocol (PLP, Layer 3)

SYS01_7_11

DATA

DATA

DATA

Packet

PH

INFORMATION FIELD

FLAG ADDRESSCONTROL FLAGFRAMECHECK

SEQUENCE

PH – PACKET HEADER

HeaderLAYER 3

(Max length 1024 octets)

Layer 2 Header Layer 2 Header

ISSUE 12 REVISION 0Packet Header



7–22

Packet HeaderAll packets have a header consisting of 3 octets.

General Format Identifier (GFI)

� � � �

� � � �

Q= qualifier bit used with X29 (control signal for remote PAD Control)

D= delivery bit (not used)

XX= Used to indicate the mode of operation:

01 for modulo 8 working (standard)10 for modulo 128 working

ISSUE 12 REVISION 0 Packet Header



7–23

X.25 Packet Header Format

SYS01_7_12

FlagData

LCGN = Logical Channel Group NumberGFI = General Format IdentifierLCN = Logical Channel NumberPTI = Packet Type Identifier

PACKET

Header Control Address

PTI LCN GFI LCGN

3 Octets

8 8 8

(1 OCTET) (1 OCTET) (1 OCTET)

DATA

11 1

ISSUE 12 REVISION 0Logical Channel Numbers (LCN)



7–24

Logical Channel Numbers (LCN)The Logical Channel Number LCN is used between the DTE and DCE to identify specificconnections, it is local to the interface and indicates the virtual circuit. The LCN isallocated from a table of free LCNs at the call set up time. The DTE allocates the LCNfor outgoing calls and the DCE allocates the LCN for incoming calls, with all packets ofthat call (in both directions) having the same LCN.

There are a total of 4096 LCNs available but these have to be shared by all the users,therefore each user is allocated a group of LCNs to use.

The LCNs have been divided into LCGNs as follows:

16 groups (LCGNs) with 256 LCNs in each group.

BAND LCGN

0 0, 1 Supports PVCs (LCNs 0–511)

1 2, 3 Supports SVC’s incoming only (512 – 1023)

2 4, 5 Supports SVC’s bothways (incoming/outgoing, 10241535)

3 6, 7 Supports SVC outgoing (1535 – 2047)

All other LCN’s are not specified and are left open.

Motorola has been allocated LCNs 1024–1055, 32 LCNs in total, as we only have amaximum of 7 SVCs in use at any time we have no problems with allocation LCNs.

The coding of the LCGN field determines the LCGN group, in Motorola’s case this willalways be LCGN 4, the LCNs for each LCGN group are coded in the range of 0–255 (8bits).

ISSUE 12 REVISION 0 Logical Channel Numbers (LCN)



7–25

Logical Channel Number (LCN)

��

� �� #�'��""��'�� #��#��"�#�$

� �$#��""��"#��%��

� ��""��&�"#��%��

� ��#�!��"��

SYS01_7_13

8 256 3 1

GFI LCGN

LCN

PTI

7 4

ISSUE 12 REVISION 0Packet Type Identifier (PTI)



7–26

Packet Type Identifier (PTI)The Packet Type Identifier field is one octet in length. Bit 1 determines whether a datapacket is being sent or a control packet:

Bit 1= 0– Data packet

1– Control packet

Bits 2–7 are coded as shown in the table opposite.

��

��

� � � � �

��

��

� � � � �

� � � � �

�� ,)�'�� +��%��!�)��,%��)�� !�)�(�#��(�&*�#��#*"��'�-�� ) �� $'��)�� ) ��$'��!�)(�

��()��!�)(�

ISSUE 12 REVISION 0 Packet Type Identifier (PTI)



7–27

Packet Type Identifier (PTI)

SYS01_7_14

Packet Type

From DCE to DTE From DTE to DCE 8 7 4 3 2 1 Call setup and clearing

Incoming callCall connectedClear indicationDCE clear confirmation

Call requestCall acceptedClear requestDTE clear confirmation

Data and interruptDCE dataDCE interrupt Expidited dataDCE interrupt confirmation

DTE dataDTE interruptDTE interrupt confirmation

Flow control and resetDCE RR (modulo 8)DCE RNR (modulo 8)

DTE RR (modulo 8)DTE RNR (modulo 8)DTE REJ (modulo 8)*Reset requestDTE reset confirmation

RestartRestart indicationDCE restart confirmation

Restart requestDTE restart confirmation

DiagnosticDiagnostic*

Registration*

Registration confirmationRegistration request

1 1 1 0 1 1

* �%(�$��''�& ",��*� "��"��%$��*�&,�$�(+%&!

�%(�� (�(��(� '� $� ��(��'�-��#�,��'�(�(%�� (��&��%&��'��&�)'��'�� (��&��%&��%)$(�&'�� ('�� (�� '��$�-�� (�

Octet 3Bits

0

0 0 0

0

00 0

0

0 00

00 1

1

1 1 1 1 1 11 1

11

11

111

1000 0 1 111

x x 1 0 0 1x 0x x 0 1 0 1x 0x x 0 0 0 1x 0

1 1 11 00001 1 100000

0x x x xxx x

0 0 1 1 1 10 10 0 1 0 1 10 1

1 1 0 0 1 1111 1 0 1 1 111

11

1 0 0 0 1111

6 5

ISSUE 12 REVISION 0Control Packet Types



7–28

Control Packet TypesAll these packet types are either “Request” or “Confirmation” where the appropriateconfirmation is the only allowed response to the request.

Types:

a) CALL request/Accept.

– carrier full destination address.

– establishes virtual circuit; resets P(S) at each end to zero.

b) CLEAR Request/Confirm

– Releases virtual circuit and LCN

c) RESET Request/Confirm

– clears queues and resets P(S) to zero

d) INTERRUPT Request/Confirm

– this packet can overtake data packets in a queue

– can carry one octet of data

– allows a break facility across the system.

e) RESTART Request/Confirm

– carries LCN 000; clears all virtual circuits

– used to start packet activity.

ISSUE 12 REVISION 0 Control Packet Types



7–29

Packet Type Identifier

��

��

� � � � � � � ��#�$"!# �� &*�()

� � � � � � � ��$##��)�� %)��

� � � � � � � ��#�!��)!$# ��&*�()

� � � � � � � � ��

� � � � � � � � ��

� � � � � � � � ��#)�''*%)�� #)�''*%)��$#��

� � � � � � � ��#�!��)!$# ��&*�()

� � � � � � � � ��'�(�)�� '�(�)��

� � � � � � � ��#�!��)!$# ��&*�()

� � � � � � � � ��()�')�� ()�')��

��

SYS01_7_16

DataNetwork

DCE DTEDTE DCE

’00001111’

’00001011’

’00001111’Call Connected

Call Request’00001011’

Incoming Call

Call Accepted

SYS01_7_15

ISSUE 12 REVISION 0Additional Fields



7–30

Additional FieldsNearly all packet types contain additional fields along with the 3 octet header.

To summarise these additional fields:

� Data Field:

Packet length (set to 128 octets for OMCR)– option: 16, 32, 64, 256, 512, 1024, 2048, 4096.

Up to 16 octets of data allowed in CALL request packet.

Full 128 octets allowed in CALL Request and clear request packet (”fast select”).

� Address Field:

Always present in call request packet.

Contains both called/calling X.25 address.

� Facilities Field:

Always present in call request packet.

Higher protocol can request new packet and window sizes.

� Cause and Diagnostics Field:

Always present in restart, reset and clear request packets.

Indicates reason for packet.

ISSUE 12 REVISION 0 Additional Fields



7–31

Additional Fields

� ��'��

� ��'��!�'��"#'�"!��(�'��"�'�'&�

� ��&'�&��'

� ��%�&&��%'�"��'��+�%�� &&��"��"!!��'�"!�%�$(�&'�

� �,��'��%�&&

� ��,��'��%�&&��,��'�(&�%��!��*'�!&�"!

� ��'��&��

�&��'"�!��"'��'��!�')"%��"#'�"!&��#��'��!�'�

� ��(&��!"&'��

�!��'��%��&"!��"%�#��'��%�&'�%'��%�&�'��'��

ISSUE 12 REVISION 0OMC to BSS Communication DTE Addresses



7–32

OMC to BSS Communication DTE AddressesThe diagram opposite demonstrates the full implementation of the X.25 DTE addresssystem used by the Motorola GSM entities. This DTE address used to indicate a singleL3 application at the OMC (OMCR DTE) or a single BSC or RXCDR (BSS DTE).

ISSUE 12 REVISION 0 OMC to BSS Communication DTE Addresses



7–33

OMC to BSS Communication (DTE Addressing)

��

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BSS

DTE

Add

ress

Addr

ess

0: 7

9320

1010

1000

0Ad

dres

s 1:

Not

use

dAd

dres

s 2:

Not

use

dAd

dres

s 3:

Not

use

dO

MC

R D

TE A

ddre

ssAd

dres

s 0:

793

1010

1040

1014

1Ad

dres

s 1:

793

1010

1040

1014

2Ad

dres

s 2:

793

1010

1040

1014

3Ad

dres

s 3:

793

1010

1040

1014

4Ad

dres

s 4:

793

1010

1040

1014

5Ad

dres

s 5:

793

1010

1040

1014

6Ad

dres

s 6:

793

1010

1040

1014

7Ad

dres

s 7:

Not

use

d

BSS

DTE

Add

ress

Addr

ess

0: 7

9320

1010

1000

1Ad

dres

s 1:

Not

use

dAd

dres

s 2:

Not

use

dAd

dres

s 3:

Not

use

dO

MC

R D

TE A

ddre

ssAd

dres

s 0:

793

1010

1040

141

Addr

ess

1: 7

9310

1010

4014

2Ad

dres

s 2:

793

1010

1040

143

Addr

ess

3: 7

9310

1010

4014

4Ad

dres

s 4:

793

1010

1040

145

Addr

ess

5: 7

9310

1010

4014

6Ad

dres

s 6:

793

1010

1040

147

Addr

ess

7: N

ot u

sed

BSS

DTE

Add

ress

Addr

ess

0: 7

9320

1010

1000

2Ad

dres

s 1:

Not

use

dAd

dres

s 2:

Not

use

dAd

dres

s 3:

Not

use

dO

MC

R D

TE A

ddre

ssAd

dres

s 0:

793

1010

1040

141

Addr

ess

1: 7

9310

1010

4014

2Ad

dres

s 2:

793

1010

1040

143

Addr

ess

3: 7

9310

1010

4014

4Ad

dres

s 4:

793

1010

1040

145

Addr

ess

5: 7

9310

1010

4014

6Ad

dres

s 6:

793

1010

1040

147

Addr

ess

7: N

ot u

sed

BSS

DTE

Add

ress

Addr

ess

0: 7

9320

1010

1000

3Ad

dres

s 1:

Not

use

dAd

dres

s 2:

Not

use

dAd

dres

s 3:

Not

use

dO

MC

R D

TE A

ddre

ssAd

dres

s 0:

793

1010

1040

141

Addr

ess

1: 7

9310

1010

4014

2Ad

dres

s 2:

793

1010

1040

143

Addr

ess

3: 7

9310

1010

4014

4Ad

dres

s 4:

793

1010

1040

145

Addr

ess

5: 7

9310

1010

4014

6Ad

dres

s 6:

793

1010

1040

47Ad

dres

s 7:

Not

use

d

BSS

DTE

Add

ress

Addr

ess

0: 7

9320

1010

1000

4Ad

dres

s 1:

Not

use

dAd

dres

s 2:

Not

use

dAd

dres

s 3:

Not

use

dO

MC

R D

TE A

ddre

ssAd

dres

s 0:

793

1010

1040

141

Addr

ess

1: 7

9310

1010

4014

2Ad

dres

s 2:

793

1010

1040

143

Addr

ess

3: 7

9310

1010

4014

4Ad

dres

s 4:

793

1010

1040

145

Addr

ess

5: 7

9310

1010

4014

6Ad

dres

s 6:

793

1010

1040

147

Addr

ess

7: N

ot u

sed

��

��

��

��"��"

��

��"��"

��

��"��"

��

��"��"

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��

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��

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��

ISSUE 12 REVISION 0Virtual Call Setup Procedure



7–34

Virtual Call Setup ProcedureAssuming the Layer 2 Link has been established using LAPB procedures and theReceiver Ready (RR) packets on the physical link.

The DTE generates the Call Request packet which contains all the required facilities, i.e.packet length; reverse charging; window size etc. This is sent over the network whereeach node along the route checks the facilities requested and set the appropriate LCN forthe duration of that call.

ISSUE 12 REVISION 0 Virtual Call Setup Procedure



7–35

Virtual Call Setup

SYS01_7_19

DTE DCE DTE

CALL REQUEST

(LCN= 20)

CALL CONNECTED

LCN= 20)

INCOMING CALL

(LCN=3)

CALL ACCEPTED

(LCN=3)

ISSUE 12 REVISION 0Virtual Call Setup Procedure



7–36



i

Chapter 8

SMS Cell Broadcast Link

ISSUE 12 REVISION 0



ii

ISSUE 12 REVISION 0



iii

Chapter 8SMS Cell Broadcast Link i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS Cell Broadcast Link 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Objectives 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Short Message Service Cell Broadcast 8–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cell Broadcast Link (CBL) 8–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CBC, Cell Broadcast Responsibilities 8–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BSS, Cell Broadcast Responsibilities 8–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Mobiles Cell Broadcast Responsibilities 8–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS CB Database Commands 8–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Command Line 8–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description 8–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CBL Message Flow Scenarios 8–14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CBL Protocol 8–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple SVC Connections 8–16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cell Broadcast Messages from BSC to BTS 8–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SMS CB Message Structure (Air-Interface) 8–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DRX Scheduling Message Coding 8–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . New SMS CB Message Bitmap 8–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . New SMS CB Message Description 8–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other Message Descriptions 8–24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Message Description Encoding 8–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . First Transmission of an SMS CB within the Schedule Period 8–26. . . . . . . . . . . . . . . Retransmission Indication 8–26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Free Message Slot, Optional Reading 8–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Free Message Slot, Reading Advised (not yet implemented by Motorola) 8–28. . . . . Reserved Codepoints 8–28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISSUE 12 REVISION 0



iv

ISSUE 12 REVISION 0 SMS Cell Broadcast Link



8–1

SMS Cell Broadcast Link

Objectives


� Understand the implementation of a CBL.

� Understand the operation of a CBL.

ISSUE 12 REVISION 0Short Message Service Cell Broadcast



8–2

Short Message Service Cell BroadcastThe Cell Broadcast Centre (CBC) is responsible for downloading cell broadcastmessages to the BSC, together with an indication of the repetition rate and the number ofbroadcasts per message. The BSC must interpret these messages and transmit eachrequest to the appropriate BTS(s). Each BTS is responsible for storing and schedulingcell broadcast messages, as well as ensuring that each broadcast message istransmitted to cells under its control.

To support interaction with the CBC, this feature shall provide the following functionality:

� A real-time interface between the CBC and BSC;

� Storage and scheduling of broadcast messages at the Cell Broadcast Scheduler(CBS);

� DRX Schedule Messages, to provide the mobile with information on the next set ofcell broadcast messages;

� Enable the operator to monitor and manage the link between the BSC and theCBC;

� Performance measurements for the CBC.

Note: This functionality co-exists with, but does not replace, multiple messagefunctionality.

ISSUE 12 REVISION 0 Short Message Service Cell Broadcast



8–3

Short Message Service, Cell Broadcast Provides:

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ISSUE 12 REVISION 0Cell Broadcast Link (CBL)



8–4

Cell Broadcast Link (CBL)To enable communication between the BSS and the CBC (Cell Broadcast Centre) onX.25 (LAPB) a link must exist between the BSS and the CBC (64k TIMESLOT). TheBSS is responsible for activating a SVC (Switched Virtual cct) to Upload Information. The CBC is responsible for activating a SVC to Download Information.

The CBL is a realtime link. The operator is able to manage the CBL device and monitorits status via the customer MMI.

The application of the X.25 (PLP) is identical to that of the OML implementation.

Note: TYPE 1 and 2 BSCs only support this feature.

ISSUE 12 REVISION 0 Cell Broadcast Link (CBL)



8–5

Cell Broadcast Link (Terrestrial)

SYS01_8_3

CellBroadcast

Entity

CBE

CellBroadcastScheduler

CellBroadcastAgent

BTS

CBC

PLPCUSTOMERSITE

RSL – 64kLAPDTimeslot Configurable

Note: The CBS is responsible forthe storing and scheduling of CellBroadcast MSGS.

BTPGPROC

PLP

LCFGPROC

BSC(SLAVE)

CBL (SVS) – 64kX.25 (LAPB)Timeslot ConfigurableReal Time

(MASTER)Note: The Cell Broadcast Agentat the BSC supports the protocolshort stack.

CustomerSpecific Link

ISSUE 12 REVISION 0CBC, Cell Broadcast Responsibilities



8–6

CBC, Cell Broadcast ResponsibilitiesThe CBC has certain functions it should support, specified in GSM 03:41 (Technicalrealisation of SMS). The functions are shown opposite.

ISSUE 12 REVISION 0 CBC, Cell Broadcast Responsibilities



8–7

CBC, Cell Broadcast Responsibilities

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ISSUE 12 REVISION 0BSS, Cell Broadcast Responsibilities



8–8

BSS, Cell Broadcast ResponsibilitiesThe BSS has certain functions it should support, specified in GSM 03.41 (Technicalrealisation of SMS). The functions are shown opposite.

The BTS shall detect CBCH overload. If overload is detected the BSS shall reject anyfurther requests from the CBC for cells with the overloaded CBCH.

Note: Motorola have placed the Cell Broadcast Scheduler and storage functionality atthe BTS. GSM specifies that each message may be broadcast at a different frequency.It identifies the maximum frequency as once every 30 seconds, the minimum frequencyas once every 32 minutes.

GSM specifies the maximum number of broadcasts of a message as 2880, therebyenabling the message to be broadcast every 30 seconds for 24 hours. If theNo_of_Broadcast_Requested is set to 0, the BSS shall broadcast the messageindefinitely or until a CBSE_KILL_MESSAGE is received from the CBC.

ISSUE 12 REVISION 0 BSS, Cell Broadcast Responsibilities



8–9

BSS, Cell Broadcast Responsibilities

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ISSUE 12 REVISION 0Mobiles Cell Broadcast Responsibilities



8–10

Mobiles Cell Broadcast ResponsibilitiesThe mobile has certain functions it should support, specified in GSM 03:41 (Technicalrealisation of SMS). The functions are shown opposite.

ISSUE 12 REVISION 0 Mobiles Cell Broadcast Responsibilities



8–11

Mobiles Cell Broadcast Responsibilities

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ISSUE 12 REVISION 0SMS CB Database Commands



8–12

SMS CB Database CommandsThe following new command is introduced by this feature:

add_link

Command Line

add_link <mms_a_id_l><mms_a_id_2><timeslot_number_a>

<mms_b_id_l><mms_b_id_2><timeslot_number_b>

The following inputs are inbound from BSC to the RXCDR.

MMS_a_id_1: First ID of T1/E1 line 9 (values 0–50)MMS_a_id_2: Second ID of T1/E1 line 9 (values 0 or 1)timeslot_number–a: Specifies timeslot on T1/E1 line 9.

Values T1 – 1 to 24Values E1 – 1 to 31

The following input parameters are outbound from the RXCDR to the MSC, OMC orCBC:

MMS_b_id_1:MMS_b_id_2:timeslot_number_b:

FunctionalDescription

The command add_link shall replace the existing commands add_oml andadd_rxcdr_mtl. It shall enable the operator to establish a link between the followingsites:

� The BSC and the MSC.

� The BSC and the OMC.

� The BSC and the CBC.

This command shall be rejected under the following conditions:

� If the MMS timeslot is in use.

� If the command is entered outside SYSGEN mode.

� If the command is entered at an insufficient security level.

� If the command is entered at a non-RXCDR site.

Note: Other commands have been modified to include the new CBL device, i.e. equipcbl, ins_device, chg_dte and other supporting commands.

ISSUE 12 REVISION 0 SMS CB Database Commands



8–13

SMSCB Database Commands

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ISSUE 12 REVISION 0CBL Message Flow Scenarios



8–14

CBL Message Flow ScenariosThe establishment of a CBL SVC can be initiated by the CBC or the BSS. Theprocedure is shown opposite.

The normal flow of information between CBC and BSS is by means of N_Dataindications, requests and confirm messages.

ISSUE 12 REVISION 0 CBL Message Flow Scenarios



8–15

CBL Message Flow Scenarios

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ISSUE 12 REVISION 0CBL Protocol



8–16

CBL ProtocolThe X.25 (LAPB) implementation is identical to that of the OML. The BSS supports aprotocol stack which utilises an application layer convergence function for connecting theBSS and the CBC. This means it supports the lower 3 OSI layers in what is morecommonly referred to as the short stack by GSM 03.49 (Example Protocol Stacks forInterconnecting CBC and BSC).

Multiple SVCConnections

The BSS shall support a maximum of 2 SVC connections – the Upload SVC (BSS to theCBC) and the Download SVC (CBC to the BSS). The Upload SVC is controlled by theBSS and is established when the BSS needs to send restart or failure information to theCBC. The BSS shall tear down the SVC if the SVC is idle for longer than a timeoutperiod. The Download SVC is established only at the request of the CBC. The BSS hasno control over the Download SVC. It is not able to establish or tear down theconnection, unless the operator requests a lock_device command at the MMI.

ISSUE 12 REVISION 0 CBL Protocol



8–17

A Protocol Stack which utilizes an Application-Networklayer convergence function for interconnecting CBC andBSC

SYS01_8_9

Application Layer – CBS Application

Layers 4,5 & 6 notused

Convergence Function:

Layer 3(Network Layer – as defined by X.213)

Layer 2 (Link Layer)

Layer 1(Physical Layer)

CBSE – Cell Broadcast Short Message Element

Maps application entityprotocol (CBSE)directly to networklayer.

ISSUE 12 REVISION 0Cell Broadcast Messages from BSC to BTS



8–18

Cell Broadcast Messages from BSC to BTSGSM recommend that commands interpreted by the BSC will result in a sequence of 4SMS BROADCAST REQUEST messages or 1 SMS BROADCAST COMMANDmessage being sent to a BTS, which in turn result in a sequence of 4 messages beingtransferred via the BTS–MS interface (GSM 04.12).

With the SMS BROADCAST REQUEST mode of operation, the 88 octet fixed lengthCBS page is split into four 22 octet blocks which are carried in SMS BROADCASTREQUEST messages as follows:

octets 1–22 are transferred in the 1st SMS BROADCAST REQUESTwith a sequence number (GSM 04.12) indicating first block

octets 23–44 are transferred in the 2nd SMS BROADCAST REQUESTwith a sequence number (GSM 04.12) indicating second block

octets 45–66 are transferred in the 3rd SMS BROADCAST REQUESTwith a sequence number (GSM 04.12) indicating third block

octets 67–88 are transferred in the 4th SMS BROADCAST REQUESTwith a sequence number (see GSM 04.12) indicating fourth block

ISSUE 12 REVISION 0 Cell Broadcast Messages from BSC to BTS



8–19

Cell Broadcast Messages from BSC to BTS

SYS01_8_10

64k LAPD (RSL)

MOTOROLA IMPLEMENT A SINGLE 88OCTET MESSAGE FOR SMCB.

BSC BTS

CELLBROADCAST

AGENT

CELLBROADCASTSCHEDULER

ISSUE 12 REVISION 0SMS CB Message Structure (Air-Interface)



8–20

SMS CB Message Structure (Air-Interface)GSM specifies that each message to be broadcast shall consist of a number of pages,where a page is of the following format:

� 6 octet header

� 82 octets of user data (93 characters)

GSM identifies a maximum number of pages as 15, with a minimum of 1. This featurecurrently supports a single page only.

The BTS stores a maximum of 650 messages, where each message is a single page ofup to 88 octets of message text plus queuing overhead. Each cell can send any or all ofthese messages.

ISSUE 12 REVISION 0 SMS CB Message Structure (Air-Interface)



8–21

SMS CB Message Structure

The SMS CB message is a message with four consecutive blocks, with Block Types“first block”, “second block”, “third block” and “fourth block”.

A null message (which is indicated by the Sequence Number 1111) (binary) shall have octets 2 to 23, inclusive, filled with the value 2B (hex).

The SMS CB message coding is defined in Technical Specification GSM 03.41.

SYS01_8_11

BLOCK TYPEThe purpose of the Block Type is to identify the function of the block and message being sent.

Bit: 8 7 6 5 4 3 2 1

Octet:Spare 0

LPD Sequence Number0 1

Spare 0 1

LPD = 01 All others are ignored

Bit No: 4 3 2 1

0 0 0

0

0

0 0 1

0

0

0

0

1

1

1

0

0

1

0

1 1 1

First block

Second block

Third block

Fourth block

First schedule block:Message containsSMSCB schedulinginformation

Null message (doesnot contain validSMSCB information)

All other values of bits 4 to 1 are reserved for future use.The use of a reserved code point shall cause the message to be ignored.

0

1




8–22

DRX SchedulingMessage Coding

The BSS shall transmit DRX Schedule Messages (refer to TS GSM 04.12 [3]) to theMobile to provide it with information on any following cell broadcast messages. TheSchedule Message enables the Mobile to minimise battery usage, by allowing it to ignoretransmissions of unwanted messages.

The text of the Schedule Message provides information pertaining to the CB messagessent afterward.

A Schedule Message consists of 4 consecutive blocks with Block Types “first scheduleblock”, “second block”, “third block” and “fourth block”.

A Schedule Message containing scheduling data which does not fill the 88 octets shall bepadded with the hexadecimal value “2B” after the end of the used part of the message.

The Schedule Message comprises a 2-octet header followed by three parts, the first ofthem of 6 octets, and the two others of variable length, as indicated on the oppositepage.

Octets following the last part (n+1 to 88 inclusive), if any, shall be ignored.

When bits are indicated as spare, they shall be set to the indicated value (0 or 1) by thenetwork, and their value shall be ignored by the Mobile Station.




8–23

SMSCB Message Structure

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SYS01_8_12

Other Message Descriptions

Bit: 8 7 6 5 4 3 2 1

Type0 0

0 0

Begin Slot Number

End Slot Numberspare spare

New CBSMS Message Bitmap

New CBSMS Message Description

Octet:

1

3 – 8

9 – 2m

(m+1) – n

2

DRX SCHEDULE MESSAGE CODING




8–24

New SMS CBMessage Bitmap

NM i: The New Message bit i refers to the content of message slot i. Its meaning is asfollows:

1. The message slot contains an SMS CB message which was either not sentduring the previous schedule period, or sent unscheduled during the preceding scheduleperiod; or, the message is indicated as of free usage, reading advised. The value is 1both for the first transmission of a given SMS CB message in the schedule period or arepetition of it within the schedule period.

0. The message slot is such that value 1 is not suitable.

An SMS CB message fulfilling the criterion for bit value 1 is said in the following to be“new”. It should be noted that the broadcasting is not necessarily the first one. Thenetwork can choose not to send a given SMS CB message in all schedule periods. Inthis case it will be “new” each time it has not been sent in the previous schedule period.Another case is when a message is scheduled but its first transmission in the scheduleperiod is pre-empted; the next time the SMS CB message is “new”.

New SMS CBMessageDescription

This part contains as many Message Descriptions as there are bits set to 1 in the NewMessage Bitmap. This part can then be empty. A message description is 1 or 2 octetslong:

New Message Description j: This one or two octet long field contains information aboutwhat is sent in the jth message slot for which NM i is set to 1.

All descriptions pertaining to the first transmission of a new message shall be put at thebeginning, so that mobile stations can determine rapidly where the new messages are.

Other MessageDescriptions

This part contains a one or two octet message description for each of the remainingmessage slots in the schedule period, in the order of transmission. This part can beempty.

The Message Slot Number for each description must be derived from the New SMS CBMessage Bitmap.




8–25


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SYS01_8_13

NM 1

NM 9

NM 17

NM 25

NM 33

NM 41

NM 2

NM 10

NM 18

NM 26

NM 34

NM 42

NM 3

NM 11

NM 19

NM 27

NM 35

NM 43

NM 4

NM 12

NM 20

NM 28

NM 36

NM 44

NM 5

NM 13

NM 21

NM 29

NM 37

NM 45

NM 6

NM 14

NM 22

NM 30

NM 38

NM 46

NM 7

NM 15

NM 23

NM 31

NM 39

NM 47

NM 8

NM 16

NM 24

NM 32

NM 40

NM 48

8 7 6 5 4 3 2 1Bit:

Octet:1

2

3

4

5

6

SYS01_8_13_1

Message Description 1

Message Description p

Octet

1

9 – 2m

8 7 6 5 4 3 2 1Bit:




8–26

MessageDescriptionEncoding

Four different encoding formats are specified, respectively: 1) for the first transmission ofan SMS CB message in the schedule period, 2) for the repetition of an SMS CBmessage, 3) for a message slot of unindicated usage that Mobile Stations can skip, and4) for a message slot of unindicated usage that Mobile Stations should not skip. Thedifferent encoding formats are identified by the Message Description Type (MDT) field.The MDT field is of variable length.

The length of a description can be determined from the value of bit 8 of the first octet,which can then be understood as a “more” bit. Value 1 indicates a single-octet field, andvalue 1 a 2-octet field.

FirstTransmission ofan SMS CBwithin theSchedule Period

This describes the content of a message slot which contains the first transmission of anSMS CB message within the period:

MDT, Message Description Type (octet 1 of Message Description, bit 8): 1-bit field set to1 for the message description of a message slot containing the first transmission duringthe schedule period of a given SMS CB.

MESSAGE IDENTIFIER (octet 1 bits 7 to 1 and octet 2 of Message Description):Consists of the low-order 15 bits of the corresponding field of the SMS CB message, asdefined in Technical Specification GSM 03.41.

RetransmissionIndication

When a message slot contains the repetition of an SMS CB message within the scheduleperiod, the corresponding message description is coded on one octet, as shownopposite.

MDT, Message Description Type (octet 1 of Message Description, bits 8 and 7): 2-bitfield set to “00” for the message description of a message slot containing the repetition ofan SMS CB message.

Repeated Message Slot Number (octet 1 of Message Description, bits 6 to 1): This fieldencodes the message slot number of the first transmission during the schedule period ofthe repeated SMS CB message. The field is encoded in binary, range 1 to 47.




8–27


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Message Identifier (high part)

Message Identifier (low part)

8 7 6 5 4 3 2 1Bit:Octet

1

2

MDT1

SYS01_8_14

8 7 6 5 4 3 2 1Bit:Octet

1MDT0 0 Repeated Message Slot Number




8–28

Free MessageSlot, OptionalReading

When no specific information about a message slot is provided, and Mobile Stationsneed not read its contents, the Message Description is coded as shown opposite.

MDT, Message Description Type (octet 1 of Message Description): 8-bit field set to“01000000”. The network can use such a message slot as needed, e.g. for unscheduledmessages or for unscheduled Schedule Messages.

Free MessageSlot, ReadingAdvised (not yetimplemented byMotorola)

When no specific information about a message slot is provided, and Mobile Stationsshould read its contents, the Message Description is coded as shown opposite.

MDT, Message Description Type (octet 1 of Message Description): 8-bit field set to“01000001”. The network can use such a message slot as needed, e.g. for sendinghigh-priority messages.

ReservedCodepoints

The values of MDT other than those specified in the previous sections are reserved forfuture use. They shall be treated as encoding a one octet message description.




8–29


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0 1 0 0 0 0 0 0

Bit: Octet

1

SYS01_8_15

8 7 6 5 4 3 2 1

0 1 0 0 0 0 0 1

Bit: Octet

1




8–30

ISSUE 12 REVISION 0



8–i

Appendix A

The 24-Channel System

ISSUE 12 REVISION 0The 24-Channel (T1) System



8–ii

The 24-Channel (T1) SystemA digital transmission link with a capacity of 1.544 mbps. T1 uses two pairs of normaltwisted wires, and can normally handle 24 voice conversations, each one digitized at 64kbp/s.

Digitization and coding of analogue voice signals requires 8000 samples per second (twotimes the highest voice frequency of 4000 Hz) and its coding in 8-bit words yields thefundamental T1 building block of 64 kbp/s for voice.

Combining 24 such voice channels into a serial bit stream using Time DivisionMultiplexing (TDM) is performed on a frame by frame basis.

A frame is a sample of 24 channels (24 x 8 = 192) plus a synchronization bit called aframing bit, which yields a block of 193 bits. Frames are transmitted at a rate of 8,000 persecond (corresponding to the required sampling rate), thus creating a 1.544 mbp/s (8.000x 193 = 1.544 mbp/s) transmission rate.

ISSUE 12 REVISION 0 The 24-Channel (T1) System



8–iii

The 24-Channel PCM Frame Format

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ISSUE 12 REVISION 024-Channel (T1) System



8–iv

24-Channel (T1) SystemWe can associate two types of signalling with a T1 system. Each one has fundamentaldifferences – each one described below.

Channel -associatedsignalling

Channel-associated signalling for each channel is conveyed in every sixth frame, usingthe least-significant bit of each corresponding time-slot, a technique known as “bitstealing”. This means that for frames 1 to 5 and 7 to 11, 8 bits carry the encoded speechfor each channel, while for frames 6 and 12 only 7 bits of encoded speech are carried.The perceived degradation to the quality of transmission is negligible. The bit stealingtechnique provides a 1.33 khz (i.e. 8 khz/6) signalling capacity for each channel within itstime-slot. The signalling bits for each channel in the sixth and twelfth frames are knownas the “A bit” and “B bit” respectively. The 12-bit frame alignment pattern is carried, onebit at a time, at the beginning of each odd frame. Similarly, the 12-frame 1.5 msmultiframe is identified by a 12-bit multiframe alignment pattern carried in the first bits ofeven frames.

Common -channelsignalling

Since a multiframe is not required for common-channel signalling, the first bit ofsuccessive even frames is used to convey common-channel signalling on a T1 system.This gives only a 4 kbit/s signalling capacity.

However the T1 system can be modified to allow 64 kbit/s Common-channel Signalling tobe carried transparently. This requires the elimination of the bit-7-zero-code-suppressionprocess normally provided in T1 systems. The suppression process involves the settingof bit 7 to a 1 for any channel which has eight zeros in a frame. Although this occasionalchanging of bit 7 has no perceivable effect on speech transmission, it does prevent theuse of time-slots for carrying 8 bits of data. The T1 system is thus sometimes referred toas having “non-clear” channels. With the necessary suppression, the T1 system cancarry in its “clear channels” not only 64 kbit/s Common-channel Signalling but also anyother 64 kbit/s data stream. The resulting loss of the zero suppression, with itsconsequent reduction in timing content, should not affect the performance of the newertime-transmission systems. With Clear-channel operation, the T1 system carries onecommon-channel signalling channel of 64 kbit/s and 23 traffic channels of 64 kbit/s.

Comparison ofT1 and E1Systems

There are significant differences between the 30-channel and 24-channel PCM systems.Apart from the number of speech channels within the frames and the companding lawsused, the systems employ radically different methods of carrying signalling.

The 30-channel system uses a separate dedicated time slot in a bunched format forchannel associated and common-channel signalling, while the 24-channel system uses adispersed format with a bit stealing-within time slot method for channel-associatedsignalling. Common-channel signalling on a 24-channel PCM (T1) system may beconveyed over a single-bit separate channel or within one of the 64 kbit//s 8-bit channels.It is important that these details are appreciated when considering the processes ofdigital switching.

ISSUE 12 REVISION 0 24-Channel (T1) System



8–v

Comparison of PCM Systems

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(2) Unless modified.

ISSUE 12 REVISION 024-Channel (T1) System



8–vi

ISSUE 12 REVISION 0



Glos–1

Glossary of Terms

ISSUE 12 REVISION 0



Glos–2

ISSUE 12 REVISION 0 Numbers



Glos–3

Numbers# Number.

2 Mbit/s link As used in this manual set, the term applies to the European4-wire 2.048 Mbit/s digital line or link which can carry 30A-law PCM channels or 120 16 kbit/s GSM channels.

4GL 4th Generation Language.

ISSUE 12 REVISION 0A



Glos–4

AA interface Interface between MSC and BSS.

A3 Authentication algorithm that produces SRES, using RANDand Ki.

A38 A single algorithm performing the function of A3 and A8.

A5 Stream cipher algorithm, residing on an MS, that producesciphertext out of plaintext, using Kc.

A8 Ciphering key generating algorithm that produces Kc usingRAND and Ki.

AB Access Burst.

Abis interface Interface between a remote BSC and BTS. Motorola offers aGSM standard and a unique Motorola Abis interface. TheMotorola interface reduces the amount of message traffic andthus the number of 2 Mbit/s lines required between BSC andBTS.

ABR Answer Bid Ratio.

ac–dc PSM AC–DC Power Supply module.

ac Alternating Current.

AC Access Class (C0 to C15).

AC Application Context.

ACC Automatic Congestion Control.

ACCH Associated Control CHannel.

ACK, Ack ACKnowledgement.

ACM Accumulated Call meter.

ACM Address Complete Message.

ACPIM AC Power Interface Module. Used in M-Cell6 indor ac BTSequipment.

AC PSM AC Power Supply Module. Used in M-Cell6 BTS equipment.

ACSE Associated Control Service Element.

ACU Antenna Combining Unit.

A/D Analogue to Digital (converter).

ADC ADministration Centre.

ADC Analogue to Digital Converter.

ADCCP ADvanced Communications Control Protocol.

ADM ADMinistration processor.

ADMIN ADMINistration.

ADN Abbreviated Dialling Number.

ADPCM Adaptive Differential Pulse Code Modulation.

AE Application Entity.

AEC Accoustic Echo Control.

AEF Additional Elementary Functions.

ISSUE 12 REVISION 0 A



Glos–5

AET Active Events Table. Alarms and events are sent to theEvents Log in the GUI. Different operators will have differentsubscription lists. All alarms and events are sent to the AETbefore they are re-routed to different subscription lists.

AFC Automatic Frequency Control.

AFN Absolute Frame Number.

AGC Automatic Gain Control.

AGCH Access Grant CHannel. A GSM common control channelused to assign MS to a SDCCH or a TCH.

Ai Action indicator.

AI Artificial Intelligence.

AIB Alarm Interface Board.

AIO A class of processor.

Air interface The radio link between the BTS and the MS.

AM Amplitude Modulation.

AMA Automatic Message Accounting (processor).

AM/MP Cell broadcast mobile terminated message. A messagebroadcast to all MSs in a cell.

AoC Advice of Change.

AoCC Advice of Change Charging supplementary service.

AoCI Advice of Change Information supplementary service.

AOC Automatic Output Control.

AP Application Process.

ARFCN Absolute Radio Frequency Channel Number. An integerwhich defines the absolute RF channel number.

ARQ Automatic ReQuest for retransmission.

ARP Address Resolution Protocol.

ASCE Association Control Service Element. An ASE whichprovides an AP with the means to establish and control anassociation with an AP in a remote NE. Maps directly ontothe Presentation layer (OMC).

ASE Application Service Element (OMC)

ASE Application Specific Entity (TCAP).

ASN.1 Abstract Syntax Notation One.

ASP Alarm and Status Panel.

ASR Answer Seizure Ratio.

ATB All Trunks Busy.

ATI Antenna Transceiver Interface.

ATT (flag) ATTach.

ATTS Automatic Trunk Testing Subsystem.

AU Access Unit.

AuC Authentication Centre. A GSM network entity which providesthe functionality for verifying the identity of an MS whenrequested by the system. Often a part of the HLR.

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Glos–6

AUT(H) AUThentication.

AUTO AUTOmatic mode.

ISSUE 12 REVISION 0 B



Glos–7

B

B Interface Interface between MSC and VLR.

BA BCCH Allocation. The radio frequency channels allocated in acell for BCCH transmission.

BAIC Barring of All Incoming Calls supplementary service.

BAOC Barring of All Outgoing Calls supplementary service.

BBBX Battery Backup Board.

BBH Base Band Hopping.

BCC BTS Colour Code.

BCCH Broadcast Control CHannel. A GSM control channel used tobroadcast general information about a BTS site on a per cellor sector basis.

BCD Binary Coded Decimal.

BCF Base station Control Function. The GSM term for the digitalcontrol circuitry which controls the BTS. In Motorola cell sitesthis is a normally a BCU which includes DRI modules and islocated in the BTS cabinet.

BCIE Bearer Capability Information Element.

BCU Base station Control Unit. A functional entity of the BSSwhich provides the base control function at a BTS site. Theterm no longer applies to a type of shelf (see BSC and BSU).

BCUP Base Controller Unit Power.

BER Bit Error Rate. A measure of signal quality in the GSMsystem.

BES Business Exchange Services.

BFI Bad Frame Indication.

BHCA Busy Hour Call Attempt.

BI all Barring of All Incoming call supplementary service.

BIB Balanced-line Interconnect Board. Provides interface to 12balanced (6-pair) 120 ohm (37-pin D-type connector) lines for2 Mbit/s circuits (See also T43).

BIC–Roam Barring of All Incoming Calls when Roaming outside theHome PLMN Country supplementary service.

BIM Balanced-line Interconnect Module.

Bin An area in a data array used to store information.

BL BootLoad. Also known as download. For example, databasesand software can be downloaded to the NEs from the BSS.

BLLNG BiLLiNG.

bit/s Bits per second (bps).

Bm Full rate traffic channel.

BN Bit Number. Number which identifies the position of aparticular bit period within a timeslot.

BPF Bandpass Filter.

BPSM �BCU Power Supply Module.

ISSUE 12 REVISION 0B



Glos–8

BS Basic Service (group).

BS Bearer Service. A type of telecommunication service thatprovides the capability for the transmission of signalsbetween user-network interfaces. The PLMN connection typeused to support a bearer service may be identical to that usedto support other types of telecommunication service.

BSC Base Station Controller. A network component in the GSMPLMN which has the digital control function of controlling allBTSs. The BSC can be located within a single BTS cabinet(forming a BSS) but is more often located remotely andcontrols several BTSs (see BCF, BCU, and BSU).

BSG Basic Service Group.

BSIC Base Transceiver Station Identity Code. A block of code,consisting of the GSM PLMN colour code and a base stationcolour code. One Base Station can have several BaseStation Colour Codes.

BSIC-NCELL BSIC of an adjacent cell.

BSP Base Site control Processor (at BSC).

BSN Backward Sequence Number.

BSS Base Station System. The system of base station equipment(Transceivers, controllers and so on) which is viewed by theMSC through a single interface as defined by the GSM 08series of recommendations, as being the entity responsiblefor communicating with MSs in a certain area. The radioequipment of a BSS may cover one or more cells. A BSSmay consist of one or more base stations. If an internalinterface is implemented according to the GSM 08.5x seriesof recommendations, then the BSS consists of one BSC andseveral BTSs.

BSSAP BSS Application Part (of Signalling System No. 7) (DTAP +BSSMAP).

BSSC Base Station System Control cabinet. The cabinet whichhouses one or two BSU shelves at a BSC or one or two RXUshelves at a remote transcoder.

BSSMAP Base Station System Management Application Part (6-8).

BSSOMAP BSS Operation and Maintenance Application Part (ofSignalling System No. 7).

BSU Base Station Unit shelf. The shelf which houses the digitalcontrol modules for the BTS (p/o BTS cabinet) or BSC (p/oBSSC cabinet).

BT British Telecom.

BT Bus Terminator.

BTC Bus Terminator Card.

BTF Base Transceiver Function.

BTP Base Transceiver Processor (at BTS). One of the six basictask groups within the GPROC.

ISSUE 12 REVISION 0 B



Glos–9

BTS Base Transceiver Station. A network component in the GSMPLMN which serves one cell, and is controlled by a BSC.The BTS contains one or more Transceivers (TRXs).

Burst A period of modulated carrier less than one timeslot. Thephysical content of a timeslot.

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Glos–10

CC Conditional.

C Interface Interface between MSC and HLR/AUC.

C7 ITU-TSS Signalling System 7 (sometimes referred to as S7 orSS#7).

CA Cell Allocation. The radio frequency channels allocated to aparticular cell.

CA Central Authority.

CAB Cabinet.

CADM Country ADMinistration. The Motorola procedure used withinDataGen to create new country and network files in theDataGen database.

CAI Charge Advice Information.

CAT Cell Analysis Tool.

CB Cell Broadcast.

CB Circuit Breaker.

CBC Cell Broadcast Centre.

CBCH Cell Broadcast CHannel.

CBF Combining Bandpass Filter.

CBL Cell Broadcast Link.

CBM Circuit Breaker Module.

CBMI Cell Broadcast Message Identifier.

CBSMS Cell Broadcast Short Message Service.

CBUS Clock Bus.

CC Connection Confirm (Part of SCCP network connectivity).

CC Country Code.

CC Call Control.

CCB Cavity Combining Block, a three way RF combiner. Thereare two types of CCB, CCB (Output) and CCB (Extension).These, with up to two CCB Control cards, may comprise theTATI. The second card may be used for redundancy.

CCBS Completion of Calls to Busy Subscriber supplementaryservice.

CCCH Common Control CHannels. A class of GSM controlchannels used to control paging and grant access. IncludesAGCH, PCH, and RACH.

CCCH_GROUP Group of MSs in idle mode.

CCD Common Channel Distributor.

CCDSP Channel Coding Digital Signal Processor.

CCF Conditional Call Forwarding.

CCH Control CHannel. Control channels are channels which carrysystem management messages.

CCH Council for Communications Harmonization (referred to inGSM Recommendations).

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Glos–11

CCIT Comité Consultatif International Télégraphique etTéléphonique. This term has been superceded by ITU–TSS(International Telecommunications Union –Telecommunications Sector).

CCM Current Call Meter.

CCP Capability/Configuration Parameter.

CCPE Control Channel Protocol Entity.

CCS Hundred call-seconds. The unit in which amounts oftelephone traffic are measured. A single call lasting onehundred seconds is one CCS. See also erlang.

Cct Circuit.

CDB Control Driver Board.

CDE Common Desktop Environment. Part of the SUN software(crontab – cron job file).

CDR Call Detail Records.

CDUR Chargeable DURation.

CEB Control Equalizer Board (BTS).

CED Called station identifier.

CEIR Central Equipment Identity Register.

Cell By GSM definition, a cell is an RF coverage area. At anomni-site, cell is synonymous with site; at a sectored site, cellis synonymous with sector. This differs from analoguesystems where cell is taken to mean the same thing as site.(See below).

Omni Site1-Cell Site

(1 BTS)

6-Sector Siteor

6-Cell Site(6 BTSs)

1 Cell =1 Sector

CEND End of charge point.

CEPT Conférence des administrations Européennes des Postes etTelecommunications.

CERM Circuit Error Rate Monitor.

CF Conversion Facility.

CF all Call Forwarding services.

CFB Call Forwarding on mobile subscriber Busy supplementaryservice.

CFC Conditional Call Forward.

CFNRc Call Forwarding on mobile subscriber Not Reachablesupplementary service.

CFNRy Call Forwarding on No Reply supplementary service.

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Glos–12

CFU Call Forwarding Unconditional supplementary service.

Channel A means of one-way transmission. A defined sequence ofperiods (for example, timeslots) in a TDMA system; a definedfrequency band in an FDMA system; a defined sequence ofperiods and frequency bands in a frequency hopped system.

CIM Coaxial Interconnect Module.

CHP CHarging Point.

CHV Card Holder Verification information.

CKSN Ciphering Key Sequence Number.

CI Cell Identity. A block of code which identifies a cell within alocation area.

CI CUG Index.

CIC Circuit Identity Code.

CIR, C/I Carrier to Interference Ratio.

Ciphertext Unintelligible data produced through the use of encipherment.

CKSN Ciphering Key Sequence Number.

CLI Calling Line Identity.

CLIP Calling Line Identification Presentation supplementaryservice.

CLIR Calling Line Identification Restriction supplementary service.

CLK Clock.

CLKX Clock Extender half size board. The fibre optic link thatdistributes GCLK to boards in system (p/o BSS etc).

CLM Connectionless Manager.

CLR CLeaR.

CM Configuration Management. An OMC application.

CM Connection Management.

CMD CoMmanD.

CMM Channel Mode Modify.

CMIP Common Management Information Protocol.

CMISE Common Management Information Service Element. An ASEwhich provides a means to transfer management informationvia CMIP messages with another NE over an associationestablished by ASCE using ROSE (OMC).

CMR Cellular Manual Revision.

CNG CalliNg tone.

COLI COnnected Line Identity.

Collocated Placed together; two or more items together in the sameplace.

Coincident Cell A cell which has a co-located neighbour whose cell boundaryfollows the boundary of the said cell. The coincident cell hasa different frequency type, but the same BSIC, as that of theneighbour cell.

COLP COnnected Line Identification Presentation supplementaryservice.

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Glos–13

COLR COnnected Line Identification Restriction supplementaryservice.

CODEX Manufacturer’s name for a type of multiplexer and packetswitch commonly installed at the Motorola OMC-R.

COM Code Object Manager.

COM COMplete.

COMB Combiner.

CONNACK CONNect ACKnowledgement.

COMM, Comms COMMunications.

CommsLink Communications Link. (2Mbit/s)

CONF CONFerence circuit.

CONFIG CONFIGuration Control Program.

CP Call Processing.

CPU Central Processing Unit.

C/R Command/Response field bit.

CR Carriage Return (RETURN).

CR Connection Request (Part of SCCP network connectivity).

CRC Cyclic Redundancy Check (3 bit).

CRE Call RE-establishment procedure.

CREF Connection REFused (Part of SCCP network connectivity).

CRM Cell Resource Manager.

CRM-LS/HS Cellular Radio Modem-Low Speed/High Speed. Low speedmodem used to interwork 300 to 2400 bit/s data servicesunder V.22bis, V.23, or V.21 standards. High speed modemused to interwork 1200 to 9600 bit/s data services underV.22bis, V.32, or V.29/V.27ter/V.21 standards.

CRT Cathode Ray Tube (video display terminal).

CSFP Code Storage Facility Processor (at BSC and BTS).

CSP Central Statistics Process. The statistics process in the BSC.

CSPDN Circuit Switched Public Data Network.

CT Call Transfer supplementary service.

CT Channel Tester.

CT Channel Type.

CTP Call Trace Product (Tool).

CTR Common Technical Regulation.

CTS Clear to Send. Method of flow control (RS232 Interface).

CTU Compact Transceiver Unit (M-Cellhorizon radio).

CUG Closed User Group supplementary service.

Cumulative value The total value for an entire statistical interval.

CW Call Waiting supplementary service.

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Glos–14

D

D Interface Interface between VLR and HLR.

D/A Digital to Analogue (converter).

DAB Disribution Alarm Board.

DAC Digital to Analogue Converter.

DACS Digital Access Cross-connect System.

DAN Digital ANnouncer (for recorded announcements on MSC).

DAS Data Acquisition System.

DAT Digital Audio Tape.

DataGen Sysgen Builder System. A Motorola offline BSS binary objectconfiguration tool.

dB Decibel. A unit of power ratio measurement.

DB DataBase.

DB Dummy Burst (see Dummy burst).

DBA DataBase Administration/Database Administrator.

DBMS DataBase Management System.

dc Direct Current.

DCB Diversity Control Board (p/o DRCU).

DCCH Dedicated Control CHannel. A class of GSM controlchannels used to set up calls and report measurements.Includes SDCCH, FACCH, and SACCH.

DCD Data Carrier Detect signal.

DCE Data Circuit terminating Equipment.

DCF Data Communications Function.

DCF Duplexed Combining bandpass Filter. (Used inHorizonmacro).

DCN Data Communications Network. A DCN connects NetworkElements with internal mediation functions or mediationdevices to the Operations Systems.

DC PSM DC Power Supply Module.

DCS1800 Digital Cellular System at 1800 MHz. A cellular phonenetwork using digital techniques similar to those used in GSM900, but operating on frequencies of 1710 – 1785 MHz and1805 – 1880 MHz.

DDF Dual-stage Duplexed combining Filter. (Used inHorizonmacro).

DDS DataGen Directory Structure.

DDS Data Drive Storage.

DDS Direct Digital Synthesis.

DEQB Diversity Equalizer Board.

DET DETach.

DFE Decision Feedback Equalizer.

DGT Data Gathering Tool.

ISSUE 12 REVISION 0 D



Glos–15

DHP Digital Host Processor.

DIA Drum Intercept Announcer.

DINO E1/HDSL Line termination module.

DINO T1 Line termination module.

DISC DISConnect.

Discon Discontiuous.

DIQ Diversity In phase and Quadrature phase.

DIR Device Interface Routine.

DL Data Link (layer).

DLCI Data Link Connection Identifier.

DLD Data Link Discriminator.

DLNB Diversity Low Noise Block.

DLSP Data Link Service Process.

DLSP Digital Link Signalling Processor.

Dm Control channel (ISDN terminology applied to mobile service).

DMA Deferred Maintenance Alarm. An alarm report level; animmediate or deferred response is required (see also PMA).

DMA Direct Memory Access.

DMR Digital Mobile Radio.

DMX Distributed Electronic Mobile Exchange (Motorola’snetworked EMX family).

DN Directory Number.

DNIC Data network identifier.

Downlink Physical link from the BTS towards the MS (BTS transmits,MS receives).

DP Dial/Dialled Pulse.

DPC Destination Point Code. A part of the label in a signallingmessage that uniquely identifies, in a signalling network, the(signalling) destination point of the message.

DPC Digital Processing and Control board.

DPNSS Digital Private Network Signalling System (BT standard forPABX interface).

DPP Dual Path Preselector.

DPR, DPRAM Dual Port Random Access Memory.

DPSM Digital Power Supply Module.

DRAM Dynamic Random Access Memory.

DRC Data Rate Converter board. Provides data and protocolconversion between PLMN and destination network for 8circuits (p/o IWF).

DRCU Diversity Radio Channel Unit. Contains transceiver, digitalcontrol circuits, and power supply (p/o BSS) (see RCU).

(D)RCU Generic term for radio channel unit. May be standard RCU ordiversity radio channel unit DRCU.

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DRI Digital Radio Interface. Provides encoding/decoding andencryption/decryption for radio channel (p/o BSS).

DRIM Digital Radio Interface extended Memory. A DRI with extramemory.

DRIX DRI Extender half size board. Fibre optic link from DRI toBCU (p/o BSS).

DRX, DRx Discontinuous reception (mechanism). A means of savingbattery power (for example in hand-portable units) byperiodically and automatically switching the MS receiver onand off.

DS-2 German term for 2 Mbit/s line (PCM interface).

DSE Data Switching Exchange.

DSI Digital Speech Interpolation.

DSP Digital Signal Processor.

DSS1 Digital Subscriber Signalling No 1.

DSSI Diversity Signal Strength Indication.

DTAP Direct Transfer Application Part (6-8).

DTE Data Terminal Equipment.

DTF Digital Trunk Frame.

DT1 DaTa form 1 (Part of SCCP network connectivity).

DTI Digital Trunk Interface.

DTMF Dual Tone Multi-Frequency (tone signalling type).

DTR Data Terminal Ready signal. Method of flow control (RS232Interface).

DTRX Dual Transceiver Module. (Radio used in M-Cellarena andM-Cellarenamacro).

DTX, DTx Discontinuous Transmission (mechanism). A means ofsaving battery power (for example in hand-portable units) andreducing interference by automatically switching thetransmitter off when no speech or data are to be sent.

Dummy burst A period of carrier less than one timeslot whose modulation isa defined sequence that carries no useful information. Adummy burst fills a timeslot with an RF signal when noinformation is to be delivered to a channel.

DYNET DYnamic NETwork. Used to specify BTSs sharing dynamicresources.

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Glos–17

E

E See Erlang.

E Interface Interface between MSC and MSC.

EA External Alarms.

EAS External Alarm System.

Eb/No Energy per Bit/Noise floor.

EBCG Elementary Basic Service Group.

EC Echo Canceller. Performs echo suppression for all voicecircuits.

ECB Provides echo cancelling for telephone trunks for 30 channels(EC).

ECID The Motorola European Cellular Infrastructure Division.

ECM Error Correction Mode (facsimile).

Ec/No Ratio of energy per modulating bit to the noise spectraldensity.

ECT Event Counting Tool.

ECT Explicit Call Transfer supplementary service.

EEL Electric Echo Loss.

EEPROM Electrically Erasable Programmable Read Only Memory.

EGSM900 Extended GSM900.

EI Events Interface. Part of the OMC-R GUI.

EIR Equipment Identity Register.

EIRP Effective Isotropic Radiated Power.

EIRP Equipment Identity Register Procedure.

EL Echo Loss.

EM Event Management. An OMC application.

EMC ElectroMagnetic Compatibility.

EMF Electro Motive Force.

EMI Electro Magnetic Interference.

eMLPP enhanced Multi-Level Precedence and Pre-emption service.

EMMI Electrical Man Machine Interface.

EMU Exchange office Management Unit (p/o Horizonoffice)

EMX Electronic Mobile Exchange (Motorola’s MSC family).

en bloc Fr. — all at once (a CCITT #7 Digital Transmission scheme);En bloc sending means that digits are sent from one systemto another ~ (that is, all the digits for a given call are sent atthe same time as a group). ~ sending is the opposite ofoverlap sending. A system using ~ sending will wait until ithas collected all the digits for a given call before it attempts tosend digits to the next system. All the digits are then sent asa group.

EOT End of Tape.

EPROM Erasable Programmable Read Only Memory.

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Glos–18

EPSM Enhanced Power Supply Module (+27 V).

EQB Equalizer Board. Control circuit for equalization for 8 timeslots each with equalizing circuitry and a DSP (p/o RCU).

EQCP Equalizer Control Processor.

EQ DSP Equalizer Digitizer Signal Processor.

Erlang International (dimensionless) unit of traffic intensity defined asthe ratio of time a facility is occupied to the time it is availablefor occupancy. One erlang is equal to 36 CCS. In the USthis is also known as a traffic unit (TU).

ERP Ear Reference Point.

ERP Effective Radiated Power.

ERR ERRor.

ESP Electro-static Point.

ESQL Embedded SQL (Structured Query Language). An RDBMSprogramming interface language.

E-TACS Extended TACS (analogue cellular system, extended).

Ethernet Type of Local Area Network.

ETR ETSI Technical Report.

ETS European Telecommunication Standard.

ETSI European Telecommunications Standards Institute.

ETX End of Transmission.

EXEC Executive Process.

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Glos–19

F

F Interface Interface between MSC and EIR.

FA Fax Adaptor.

FA Full Allocation.

FA Functional Area.

FAC Final Assembly Code.

FACCH Fast Associated Control Channel. A GSM dedicated controlchannel which is associated with a TCH and carries controlinformation after a call is set up (see SDCCH).

FACCH/F Fast Associated Control Channel/Full rate.

FACCH/H Fast Associated Control Channel/Half rate.

FB Frequency correction Burst (see Frequency correction burst).

FC-AL Fibre Channel Arbitration Loop. (Type of hard disc).

FCCH Frequency Correction CHannel. A GSM broadcast controlchannel which carries information for frequency correction ofthe mobile (MS).

FCP Fault Collection Process (in BTS).

FCS Frame Check Sequence.

FDM Frequency Division Multiplex.

FDMA Frequency Division Multiple Access.

FDN Fixed Dialling Number.

FDP Fault Diagnostic Procedure.

FEC Forward Error Correction.

FEP Front End Processor.

FER Frame Erasure Ratio.

FFS, FS For Further Study.

FH Frequency Hopping.

FIB Forward Indicator Bit.

FIR Finite Impulse Response (filter type).

FK Foreign Key. A database column attribute; the foreign keyindicates an index into another table.

FM Fault Management (at OMC).

FM Frequency Modulation.

FMIC Fault Management Initiated Clear.

FMUX Fibre optic MUltipleXer.

FN Frame Number. Identifies the position of a particular TDMAframe within a hyperframe.

FOA First Office Application.

FOX Fibre Optic eXtender.

FR Full Rate. Refers to the current capacity of a data channel onthe GSM air interface, that is, 8 simultaneous calls per carrier(see also HR – Half Rate).

ISSUE 12 REVISION 0F



Glos–20

FRU Field Replaceable Unit.

Frequency correction Period of RF carrier less than one timeslot whose modulationbit stream allows frequency correction to be performed easilywithin an MS burst.

FS Frequency Synchronization.

FSL Free Space Loss. The decrease in the strength of a radiosignal as it travels between a transmitter and receiver. TheFSL is a function of the frequency of the radio signal and thedistance the radio signal has travelled from the point source.

FSN Forward Sequence Number.

FTAM File Transfer, Access, and Management. An ASE whichprovides a means to transfer information from file to file(OMC).

ftn forwarded-to number.

FTP Fault Translation Process (in BTS).

FTP File Transfer Protocol.

ISSUE 12 REVISION 0 G



Glos–21

GG Interface Interface between VLR and VLR.

Gateway MSC An MSC that provides an entry point into the GSM PLMNfrom another network or service. A gateway MSC is also aninterrogating node for incoming PLMN calls.

GB, Gbyte Gigabyte.

GBIC Gigabit Interface Converter.

GCLK Generic Clock board. System clock source, one per site (p/oBSS, BTS, BSC, IWF, RXCDR).

GCR Group Call Register.

GDP Generic DSP Processor board. Interchangeable with the XCDRboard.

GDP E1 GDP board configured for E1 link usage.

GDP T1 GDP board configured for T1 link usage.

GHz Giga-Hertz (109).

GID Group ID. A unique number used by the system to identify auser’s primary group.

GMB GSM Multiplexer Board (p/o BSC).

GMR GSM Manual Revision.

GMSC Gateway Mobile-services Switching Centre (see GatewayMSC).

GMSK Gaussian Minimum Shift Keying. The modulation techniqueused in GSM.

GND GrouND.

GOS Grade of Service.

GPA GSM PLMN Area.

GPC General Protocol Converter.

GPROC Generic Processor board. GSM generic processor board: a68030 with 4 to 16 Mb RAM (p/o BSS, BTS, BSC, IWF,RXCDR).

GPROC2 Generic Processor board. GSM generic processor board: a68040 with 32 Mb RAM (p/o BSS, BTS, BSC, IWF, RXCDR).

GPRS General Packet Radio Service.

GPS Global Positioning by Satellite.

GSA GSM Service Area. The area in which an MS can be reachedby a fixed subscriber, without the subscriber’s knowledge ofthe location of the MS. A GSA may include the areas servedby several GSM PLMNs.

GSA GSM System Area. The group of GSM PLMN areasaccessible by GSM MSs.

GSM Groupe Spécial Mobile (the committee).

GSM Global System for Mobile communications (the system).

GSM MS GSM Mobile Station.

GSM PLMN GSM Public Land Mobile Network.

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Glos–22

GSR GSM Software Release.

GT Global Title.

GTE Generic Table Editor. The Motorola procedure which allowsusers to display and edit MCDF input files.

Guard period Period at the beginning and end of timeslot during which MStransmission is attenuated.

GUI Graphical User Interface.

GUI client A computer used to display a GUI from an OMC-R GUIapplication which is beingbrun on a GUI server.

GUI server A computer used to serve the OMC-R GUI applicationprocess running locally (on its processor) to other computers(Gui clients or other MMI processors).

GWY GateWaY (MSC/LR) interface to PSTN.

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Glos–23

HH Interface Interface between HLR and AUC.

H-M Human-Machine Terminals.

HAD, HAP HLR Authentication Distributor.

HANDO, Handover HANDOver. The action of switching a call in progress fromone radio channel to another radio channel. Handover allowsestablished calls to continue by switching them to anotherradio resource, as when an MS moves from one BTS area toanother. Handovers may take place between the followingGSM entities: timeslot, RF carrier, cell, BTS, BSS and MSC.

HCU Hybrid Combining Unit. (Used in Horizonmacro).

HDLC High level Data Link Control.

HDSL High bit-rate Digital Subscriber Line.

HLC High Layer Compatibility. The HLC can carry informationdefining the higher layer characteristics of a teleservice activeon the terminal.

HLR Home Location Register. The LR where the current locationand all subscriber parameters of an MS are permanentlystored.

HMS Heat Management System. The system that providesenvironmental control of the components inside the ExCell,TopCell and M-Cell cabinets.

HO HandOver. (see HANDO above).

HPU Hand Portable Unit.

HOLD Call hold supplementary service.

HPLMN Home PLMN.

HR Half Rate. Refers to a type of data channel that will doublethe current GSM air interface capacity to 16 simultaneouscalls per carrier (see also FR – Full Rate).

HS HandSet.

HSI/S High Speed Interface card.

HSM HLR Subscriber Management.

HSN Hopping Sequence Number.

HU Home Units.

HW Hardware.

Hyperframe 2048 superframes. The longest recurrent time period of theframe structure.

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Glos–24

I

I Information frames (RLP).

IA Incomming Access (closed user group (CUG) SS(supplementary service)).

IA5 International Alphanumeric 5.

IADU Integrated Antenna Distribution Unit. (The IADU is theequivalent of the Receive Matrix used on pre-M-Cell BTSs).

IAM Initial Address Message.

IAS Internal Alarm System.

IC Integrated Circuit.

IC Interlock Code (CUG SS).

IC(pref) Interlock Code op the preferential CUG.

ICB Incoming Calls Barred.

ICC Integrated Circuit(s) Card.

ICM In-Call Modification.

ICMP Internet Control Message Protocol.

ID, Id IDentification/IDentity/IDentifier.

IDN Integrated Digital Network.

IDS INFOMIX Database Server. (OMC-R relational databasemanagement system).

IE Information Element (signalling).

IEC International Electrotechnical Commission.

IEEE Institute of Electrical and Electronic Engineers.

IEI Information Element Identifier.

I-ETS Interim European Telecommunication Standard.

IF Intermediate Frequency.

IFAM Initial and Final Address Message.

IM InterModulation.

IMACS Intelligent Monitor And Control System.

IMEI International Mobile station Equipment Identity. Electronicserial number that uniquely identifies the MS as a piece orassembly of equipment. The IMEI is sent by the MS alongwith request for service.

IMM IMMediate assignment message.

IMSI International Mobile Subscriber Identity. Published mobilenumber (prior to ISDN) (see also MSISDN) that uniquelyidentifies the subscription. It can serve as a key to derivesubscriber information such as directory number(s) from theHLR.

IN Intelligent Network.

IN Interrogating Node. A switching node that interrogates anHLR, to route a call for an MS to the visited MSC.

INS IN Service.

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Glos–25

INS Intelligent Network Service.

InterAlg Interference Algorithm. A single interference algorithm in acell.

Interworking The general term used to describe the inter-operation ofnetworks, services, supplementary services and so on. Seealso IWF.

Interval A recording period of time in which a statistic is pegged.

Interval expiry The end of an interval.

I/O Input/Output.

IOS Intelligent Optimization Platform.

IP Initialisation Process.

IP Internet Protocol.

IPC Inter-Process Communication.

IP, INP INtermodulation Products.

IPR Intellectual PRoperty.

IPSM Integrated Power Supply Module (–48 V).

IPX (A hardware component).

ISAM Indexed Sequential Access Method.

ISC International Switching Centre.

ISDN Integrated Services Digital Network. An integrated servicesnetwork that provides digital connections betweenuser-network interfaces.

ISG Motorola Information Systems group (formally CODEX).

ISO International Organisation for Standardization.

ISQL Informix Structured Query Language.

ISUP ISDN User Part (of signalling system No. 7).

IT Inactivity Test (Part of SCCP network connectivity).

ITC Information Transfer Capability.

ITU International Telecommunication Union.

ITU–TSS International Telecommunication Union – TelecommunicationsSector.

IWF InterWorking Function. A network functional entity whichprovides network interworking, service interworking,supplementary service interworking or signalling interworking.It may be a part of one or more logical or physical entities in aGSM PLMN.

IWMSC InterWorking MSC.

IWU InterWorking Unit.

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Glos–26

Kk kilo (103).

k Windows size.

K Constraint length of the convolutional code.

KAIO Kernal Asynchronous Input/Output.

kb, kbit kilo-bit.

kbit/s, kbps kilo-bits per second.

kbyte kilobyte.

Kc Ciphering key. A sequence of symbols that controls theoperation of encipherment and decipherment.

kHz kilo-Hertz (103).

Ki Individual subscriber authentication Key (p/o authenticationprocess of AUC).

KIO A class of processor.

KSW Kiloport SWitch board. TDM timeslot interchanger to connectcalls (p/o BSS).

KSWX KSW Expander half size board. Fibre optic distribution ofTDM bus (p/o BSS).

kW kilo-Watt.

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LL1 Layer 1.

L2ML Layer 2 Management Link.

L2R Layer 2 Relay function. A function of an MS and IWF thatadapts a user’s known layer2 protocol LAPB onto RLP fortransmission between the MT and IWF.

L2R BOP L2R Bit Orientated Protocol.

L2R COP L2R Character Orientated Protocol.

L3 Layer 3.

LA Location Area. An area in which an MS may move freelywithout updating the location register. An LA may compriseone or several base station areas.

LAC Location Area Code.

LAI Location Area Identity. The information indicating the locationarea in which a cell is located.

LAN Local Area Network.

LANX LAN Extender half size board. Fibre optic distribution of LANto/from other cabinets (p/o BSS etc).

LAPB Link Access Protocol Balanced (of ITU–TSS Rec. x.25).

LAPD Link Access Protocol Data.

LAPDm Link Access Protocol on the Dm channel.

LC Inductor Capacitor (type of filter).

LCF Link Control Function.

LCN Local Communications Network.

LCP Link Control Processor.

LE Local Exchange.

LED Light Emitting Diode.

LF Line Feed.

LI Length Indicator.

LI Line Identity.

LLC Lower Layer Compatibility. The LLC can carry informationdefining the lower layer characteristics of the terminal.

Lm Traffic channel with capacity lower than a Bm.

LMP LAN Monitor Process.

LMS Least Mean Square.

LMSI Local Mobile Station Identity. A unique identity temporarilyallocated to visiting mobile subscribers in order to speed upthe search for subscriber data in the VLR, when the MSRNallocation is done on a per cell basis.

LMT Local Maintenance Terminal.

LNA Low Noise Amplifier.

LND Last Number Dialled.

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Location area An area in which a mobile station may move freely withoutupdating the location register. A location area may compriseone or several base station areas.

LPC Linear Predictive Code.

LPLMN Local PLMN.

LR Location Register. The GSM functional unit where MSlocation information is stored. The HLR and VLR are locationregisters.

LSSU Link Stations Signalling Unit (Part of MTP transport system).

LSTR Listener Side Tone Rating.

LTA Long Term Average. The value required in a BTS’s GCLKfrequency register to produce a 16.384 MHz clock.

LTE Local Terminal Emulator.

LTP Long Term Predictive.

LTU Line Terminating Unit.

LU Local Units.

LU Location Update.

LV Length and Value.

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MM Mandatory.

M Mega (106).

M-Cell Motorola Cell.

M&TS Maintenance and Troubleshooting. Functional area ofNetwork Management software which (1) collects anddisplays alarms, (2) collects and displays Software/Hardwareerrors, and (3) activates test diagnostics at the NEs (OMC).

MA Mobile Allocation. The radio frequency channels allocated toan MS for use in its frequency hopping sequence.

MAC Medium Access Control.

MACN Mobile Allocation Channel Number.

Macrocell A cell in which the base station antenna is generally mountedaway from buildings or above rooftop level.

MAF Mobile Additional Function.

MAH Mobile Access Hunting supplementary service.

MAI Mobile Allocation Index.

MAIDT Mean Accumulated Intrinsic Down Time.

MAINT MAINTenance.

MAIO Mobile Allocation Index Offset.

MAP Mobile Application Part (of signalling system No. 7). Theinter-networking signalling between MSCs and LRs and EIRs.

MAPP Mobile Application Part Processor.

MB, Mbyte Megabyte.

Mbit/s Megabits per second.

MCAP Motorola Cellular Advanced Processor.

MCC Mobile Country Code.

MCDF Motorola Customer Data Format used by DataGen for simpledata entry and retrieval.

MCI Malicious Call Identification supplementary service.

MCSC Motorola Customer Support Centre.

MCU Main Control Unit for M-Cell2/6. Also referred to as the MicroControl Unit in software.

MCUF Main Control Unit, with dual FMUX. (Used in M-Cellhorizon).

MCU-m Main Control Unit for M-Cell Micro sites (M-Cellm). Alsoreferred to as the Micro Control Unit in software.

MCUm The software subtype representation of the Field ReplaceableUnit (FRU) for the MCU-m.

MD Mediation Device.

MDL (mobile) Management (entity) - Data Link (layer).

ME Maintenance Entity (GSM Rec. 12.00).

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ME Mobile Equipment. Equipment intended to access a set ofGSM PLMN and/or DCS telecommunication services, butwhich does not contain subscriber related information.Services may be accessed while the equipment, capable ofsurface movement within the GSM system area, is in motionor during halts at unspecified points.

MEF Maintenance Entity Function (GSM Rec. 12.00).

MF MultiFrame.

MF Multi-Frequency (tone signalling type).

MF MultiFunction block.

MGMT, mgmt Management.

MGR Manager.

MHS Message Handling System.

MHS Mobile Handling Service.

MHz Mega-Hertz (106).

MI Maintenance Information.

MIB Management Information Base. A Motorola OMC-Rdatabase. There is a CM MIB and an EM MIB.

MIC Mobile Interface Controller.

Microcell A cell in which the base station antenna is generally mountedbelow rooftop level. Radio wave propagation is by diffractionand scattering around buildings, the main propagation iswithin street canyons.

min minute(s).

�s micro-second (10–6).

�BCU Micro Base Control Unit.

MIT Management Information Tree. Name of a file on theMotorola OMC-R.

MM Man Machine.

MM Mobility Management.

MME Mobile Management Entity.

MMF Middle Man Funnel process.

MMI Man Machine Interface. The method in which the userinterfaces with the software to request a function or changeparameters.

MMI client A machine configured to use the OMC-R software from anMMI server.

MMI processor MMI client/MMI server.

MMI server A computer which has its own local copy of the OMC-Rsoftware. It can run the OMC-R software for MMI clients tomount.

MML Man Machine Language. The tool of MMI.

MMS Multiple Serial Interface Link. (see also 2Mbit/s link)

MNC Mobile Network Code.

MNT MaiNTenance.

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MO Mobile Originated.

MO/PP Mobile Originated Point-to-Point messages.

MOMAP Motorola OMAP.

MoU Memorandum of Understanding.

MPC Multi Personal Computer (was p/o OMC).

MPH (mobile) Management (entity) - PHysical (layer) [primitive].

MPTY MultiParTY (Multi ParTY) supplementary service.

MPX MultiPleXed.

MRC Micro Radio Control Unit.

MRN Mobile Roaming Number.

MRP Mouth Reference Point.

MS Mobile Station. The GSM subscriber unit.

MSC Mobile-services Switching Centre, Mobile Switching Centre.

MSCM Mobile Station Class Mark.

MSCU Mobile Station Control Unit.

msec millisecond (.001 second).

MSI Multiple Serial Interface board. Intelligent interface to two2 Mbit/s digital links (see 2 Mbit/s link and DS-2) (p/o BSS).

MSIN Mobile Station Identification Number.

MSISDN Mobile Station International ISDN Number. Published mobilenumber (see also IMSI). Uniquely defines the mobile stationas an ISDN terminal. It consists of three parts: the CountryCode (CC), the National Destination Code (NDC) and theSubscriber Number (SN).

MSRN Mobile Station Roaming Number. A number assigned by theMSC to service and track a visiting subscriber.

MSU Message Signal Unit (Part of MTP transport system). Asignal unit containing a service information octet and asignalling information field which is retransmitted by thesignalling link control, if it is received in error.

MT Mobile Terminated. Describes a call or short messagedestined for an MS.

MT (0, 1, 2) Mobile Termination. The part of the MS which terminates theradio transmission to and from the network and adaptsterminal equipment (TE) capabilities to those of the radiotransmission. MT0 is mobile termination with no support forterminal, MT1 is mobile termination with support for an S-typeinterface and MT2 is mobile termination with support for anR-type interface.

MTM Mobile-To-Mobile (call).

MTP Message Transfer Part.

MT/PP Mobile Terminated Point-to-Point messages.

MTBF Mean Time Between Failures.

MTK Message Transfer LinK.

MTL MTP Transport Layer Link (A interface).

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MTP Message Transfer Part.

MTTR Mean Time To Repair.

Multiframe Two types of multiframe are defined in the system: a26-frame multiframe with a period of 120 ms and a 51-framemultiframe with a period of 3060/13 ms.

MU Mark Up.

MUMS Multi User Mobile Station.

MUX Multiplexer.

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NN/W Network.

NB Normal Burst (see Normal burst).

NBIN A parameter in the hoping sequence.

NCC Network (PLMN) Colour Code.

NCELL Neighbouring (of current serving) Cell.

NCH Notification CHannel.

ND No Duplicates. A database column attribute meaning thecolumn contains unique values (used only with indexedcolumns).

NDC National Destination Code.

NDUB Network Determined User Busy.

NE Network Element (Network Entity).

NEF Network Element Function block.

NET Norme Européennes de Telecommunications.

NETPlan Frequency planning tool.

NF Network Function.

NFS Network File System.

NHA Network Health Analyst. Optional OMC-R processor feature.

NIC Network Interface Card.

NIC Network Independent Clocking.

NIS Network Information Service. It allows centralised control ofnetwork information for example hostnames, IP addressesand passwords.

NIU Network Interface Unit.

NIU-m Network Interface Unit, micro.

NLK Network LinK processor(s).

Nm Newton metres.

NM Network Management (manager). NM is all activities whichcontrol, monitor and record the use and the performance ofresources of a telecommunications network in order toprovide telecommunication services to customers/users at acertain level of quality.

NMASE Network Management Application Service Element.

NMC Network Management Centre. The NMC node of the GSMTMN provides global and centralised GSM PLMN monitoringand control, by being at the top of the TMN hierarchy andlinked to subordinate OMC nodes.

NMSI National Mobile Station Identification number.

NMT Nordic Mobile Telephone system.

NN No Nulls. A database column attribute meaning the columnmust contain a value in all rows.

Normal burst A period of modulated carrier less than a timeslot.

NPI Number Plan Identifier.

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NRZ Non Return to Zero.

NSAP Network Service Access Point.

NSP Network Service Provider.

NSS Network Status Summary.

NT Network Termination.

NT Non Transparent.

NTAAB New Type Approval Advisory Board.

NUA Network User Access.

NUI Network User Identification.

NUP National User Part (of signalling system No. 7).

NV NonVolatile.

NVRAM Non-Volatile Random Access Memory.

nW Nano-Watt (10–9).

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O

O Optional.

OA Outgoing Access (CUG SS).

O&M Operations and Maintenance.

OASCU Off-Air-Call-Set-Up. The procedure in which atelecommunication connection is being established whilst theRF link between the MS and the BTS is not occupied.

OCB Outgoing Calls Barred within the CUG.

OCXO Oversized Voltage Controlled Crystal Oscillator.

OD Optional for operators to implement for their aim.

OFL % OverFlow.

offline IDS shutdown state.

online IDS normal operatng state.

OIC Operator Initiated Clear.

OLM Off_Line MIB. A Motorola DataGen database, used to modifyand carry out Radio Frequency planning on multiple BSSbinary files.

OLR Overall Loudness Rating.

OMAP Operations and Maintenance Application Part (of signallingsystem No. 7) (was OAMP).

OMC Operations and Maintenance Centre. The OMC node of theGSM TMN provides dynamic O&M monitoring and control ofthe PLMN nodes operating in the geographical areacontrolled by the specific OMC.

OMC-G Operations and Maintenance Centre — Gateway Part.(Iridium)

OMC-G Operations and Maintenance Centre — GPRS Part.

OMC-R Operations and Maintenance Centre — Radio Part.

OMC-S Operations and Maintenance Centre — Switch Part.

OMF Operations and Maintenance Function (at BSC).

OML Operations and Maintenance Link.

OMP Operation and Maintenance Processor.

OMS Operation and Maintenance System (BSC–OMC).

OMSS Operation and Maintenance SubSystem.

OOS Out Of Service.

OPC Originating Point Code. A part of the label in a signallingmessage that uniquely identifies, in a signalling network, the(signalling) origination point of the message.

ORAC Olympus Radio Architecture Chipset.

OS Operating System.

OSI Open Systems Interconnection.

OSI RM OSI Reference Model.

OSF Operation Systems Function block.

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OSF/MOTIF Open Software Foundation Motif. The basis of the GUI usedfor the Motorola OMC-R MMI.

OSS Operator Services System.

Overlap Overlap sending means that digits are sent from one systemto another as soon as they are received by the sendingsystem. A system using ~ will not wait until it has received alldigits of a call before it starts to send the digits to the nextsystem. This is the opposite of en bloc sending where alldigits for a given call are sent at one time.

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P

PA Power Amplifier.

PAB Power Alarm Board.

PABX Private Automatic Branch eXchange.

PAD Packet Assembler/Disassembler facility.

Paging The procedure by which a GSM PLMN fixed infrastructureattempts to reach an MS within its location area, before anyother network-initiated procedure can take place.

PATH CEPT 2 Mbit/s route through the BSS network.

PBUS Processor Bus.

PBX Private Branch eXchange.

PC Personal Computer.

PCH Paging CHannel. A GSM common control channel used tosend paging messages to the MSs.

PCHN Paging Channel Network.

PCHN Physical Channel.

PCM Pulse Code Modulation (see also 2 Mbit/s link which is thephysical bearer of PCM).

PCN Personal Communications Network.

PCR Preventative Cyclic Retransmission. A form of errorcorrection suitable for use on links with long transmissiondelays, such as satellite links.

PCU Packet Control Unit (p/o GPRS).

PCU Picocell Control unit (p/o M-Cellaccess).

pd Potential difference.

PD Protocol Discriminator.

PD Public Data.

PDB Power Distribution Board.

PDF Power Distribution Frame (MSC/LR).

PDN Public Data Networks.

PDU Power Distribution Unit.

PDU Protected Data Unit.

PEDC Pan European Digital Cellular.

Peg A single incremental action modifying the value of a statistic.

Pegging Modifying a statistical value.

PH Packet Handler.

PH PHysical (layer).

PHI Packet Handler Interface.

PI Presentation Indicator.

Picocell A cell site where the base station antenna is mounted within abuilding.

PICS Protocol Implementation Conformance Statement.

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PID Process IDentifier/Process ID.

PIM PCM Interface Module (MSC).

PIN Personal Identification Number.

PIN Problem Identification Number.

PIX Parallel Interface Extender half size board. Customer alarminterface (p/o BSS).

PIXT Protocol Implementation eXtra information for Testing.

PK Primary Key. A database column attribute, the primary key isa not-null, non-duplicate index.

Plaintext Unciphered data.

PlaNET Frequency planning tool.

PLL Phase Lock Loop (refers to phase locking the GCLK in theBTS).

PLMN Public Land Mobile Network. The mobile communicationsnetwork.

PM Performance Management. An OMC application.

PM-UI Performance Management User Interface.

PMA Prompt Maintenance Alarm. An alarm report level; immediateaction is necessary (see also DMA).

PMS Pseudo MMS.

PMUX PCM MUltipleXer.

PN Permanent Nucleus (of GSM).

PNE Présentation des Normes Européennes.

POI Point of Interconnection (with PSTN).

POTS Plain Old Telephone Service (basic telephone services).

p/o Part of.

pp, p-p Peak-to-peak.

PP Point-to-Point.

ppb Parts per billion.

PPE Primative Procedure Entity.

ppm Parts per million (x 10–6).

Pref CUG Preferential CUG.

Primary Cell A cell which is already optimized in the network and has aco-located neighbour whose cell boundary follows theboundary of the said cell. The primary cell has a preferredband equal to the frequency type of the coincident cell.

PROM Programmable Read Only Memory.

Ps Location probability.

PSA Periodic Supervision of Accessability.

PSAP Presentation Services Access Point.

PSM Power Supply Module.

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PSPDN Packet Switched Public Data Network. Public datacommunications network. x.25 links required for NE to OMCcommunications will probably be carried by PSPDN.

PSTN Public Switched Telephone Network. The UK land linetelephone network.

PSU Power Supply Unit.

PSW Pure Sine Wave.

PTO Public Telecommunications Operator.

PUCT Price per Unit Currency Table.

PVC Permanent Virtual Circuit.

PW Pass Word.

PWR Power.

PXPDN Private eXchange Public Data Network.

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QQA Q (Interface) – Adapter.

Q3 Interface between NMC and GSM network.

Q-adapter Used to connect MEs and SEs to TMN (GSM Rec. 12.00).

QAF Q-Adapter Function.

QEI Quad European Interface. Interfaces four 2 Mbit/s circuits toTDM switch highway (see MSI).

QIC Quarter Inch Cartridge (Data storage format).

QOS Quality Of Service.

Quiescent mode IDS intermediate state before shutdown.

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RR Value of reduction of the MS transmitted RF power relative to

the maximum allowed output power of the highest powerclass of MS (A).

RA RAndom mode request information field.

RAB Random Access Burst.

RACCH Random Access Control CHannel. A GSM common controlchannel used to originate a call or respond to a page.

RACH Random Access CHannel.

RAM Random Access Memory.

RAND RANDom number (used for authentication).

RATI Receive Antenna Transceiver Interface.

RAx Rate Adaptation.

RBDS Remote BSS Diagnostic System (a discontinued Motoroladiagnostic facility).

RBER Residual Bit Error Ratio.

RBTS Remote Base Transceiver Station.

RCB Radio Control Board (p/o DRCU).

RCI Radio Channel Identifier.

RCP Radio Control Processor.

RCU Radio Channel Unit. Contains transceiver, digital controlcircuits, and power supply (p/o BSS) (see DRCU).

RCVR Receiver.

RDBMS Relational DataBase Management System (INFORMIX).

RDI Radio Digital Interface System.

RDIS Restricted Digital Information.

RDM Reference Distribution Module.

RDN Relative Distinguished Name. A series of RDN form a uniqueidentifier, the distinguished name, for a particular networkelement.

REC, Rec RECommendation.

REJ REJect(ion).

REL RELease.

RELP Residual Excited Linear Predictive.

RELP-LTP RELP Long Term Prediction. A name for GSM full rate (seefull rate).

resync Resynchronize/resynchronization.

REQ REQuest.

Revgen A Motorola DataGen utility for producing an MMI script from abinary object database.

RF Radio Frequency.

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RFC, RFCH Radio Frequency Channel. A partition of the system RFspectrum allocation with a defined bandwidth and centrefrequency.

RFE Receiver Front End (shelf).

RFEB Receiver Front End Board (p/o DRCU II).

RFI Radio Frequency Interference.

RFM Radio Frequency Module.

RFN Reduced TDMA Frame Number.

RFU Reserved for Future Use.

RJ45 Network cable/Connector type.

RISC Reduced Instruction Set Computer.

RL Remote login.

RLC Release Complete.

RLP Radio Link Protocol. An ARQ protocol used to transfer userdata between an MT and IWF. See GSM 04.22.

RLR Receiver Loudness Rating.

RLSD ReLeaSeD.

RMS Root Mean Square (value).

RMSU Remote Mobile Switching Unit.

RNTABLE Table of 128 integers in the hopping sequence.

ROM Read Only Memory.

ROSE Remote Operations Service Element. An ASE which carriesa message between devices over an association establishedby ASCE (a CCITT specification for O & M) (OMC).

Roundtrip Time period between transmit and receive instant of atimeslot in the BTS, propagation determined by the responsebehaviour of the MS and the MS to BTS delay distance.

RPE Regular Pulse Excited.

RPE-LTP Regular Pulse Excitation - Long Term Prediction. The GSMdigital speech coding scheme.

RPOA Recognised Private Operating Agency.

RPR Read Privilege Required. Access to the column is allowedonly for privileged accounts.

RR Radio Resource management.

RR Receive Ready (frame).

RRSM Radio Resource State Machine.

RS232 Standard serial interface.

RSE Radio System Entity.

RSL Radio Signalling Link.

RSLF Radio System Link Function.

RSLP Radio System Link Processor.

RSS Radio SubSystem (replaced by BSS).

RSSI Received Signal Strength Indicator.

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RSZI Regional Subscription Zone Identity.

RTC Remotely Tuneable Channel Combiner.

RTE Remote Terminal Emulator.

RTF Radio Transceiver Function.

RTF Receive Transmit Functions.

RTS Request to Send. Method of flow control (RS232 Interface).

RU Rack Unit.

Run level System processor operating mode.

Rx Receive(r).

RXCDR Remote Transcoder.

RXF Receive Function (of the RTF).

RXLEV-D Received signal level downlink.

RXLEV-U Received signal level uplink.

RXQUAL-D Received signal quality downlink.

RXQUAL-U Received signal quality uplink.

RXU Remote Transcoder Unit. The shelf which houses theremote transcoder modules in a BSSC cabinet at a remotetranscoder site.

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SS/W SoftWare.

SABM Set Asynchronous Balanced Mode. A message whichestablishes the signalling link over the air interface.

SABME SABM Extended.

SACCH Slow Associated Control CHannel. A GSM control channelused by the MS for reporting RSSI and signal qualitymeasurements.

SACCH/C4 Slow Associated Control CHannel/SDCCH/4.

SACCH/C8 Slow Associated Control CHannel/SDCCH/8.

SACCH/T Slow Associated Control CHannel/Traffic channel.

SACCH/TF Slow Associated Control CHannel/Traffic channel Full rate.

SACCH/TH Slow Associated Control CHannel/Traffic channel Half rate.

SAGE A brand of trunk test equipment.

SAP Service Access Point. In the reference model for OSI, SAPsof a layer are defined as gates through which services areoffered to an adjacent higher layer.

SAP System Audits Process.

SAPI Service Access Point Indicator (identifier).

SAW Surface Acoustic Wave.

SB Synchronization Burst (see Synchronization burst).

SBUS Serial Bus.

SC Service Centre (used for Short Message Service).

SC Service Code.

SCCA System Change Control Administration. Software modulewhich allows full or partial software download to the NE(OMC).

SCCP Signalling Connection Control Part (6-8).

SCEG Speech Coding Experts Group (of GSM).

SCH Synchronization CHannel. A GSM broadcast control channelused to carry information for frame synchronization of MSsand identification of base stations.

SCI Status Control Interface.

SCIP Serial Communication Interface Processor.

SCM Status Control Manager.

SCN Sub-Channel Number. One of the parameters defining aparticular physical channel in a BS.

SCP Service Control Point (an intelligent network entity).

SCSI Small Computer Systems Interface.

SCU Slim Channel Unit.

SCU900 Slim Channel Unit for GSM900.

SDCCH Stand-alone Dedicated Control CHannel. A GSM controlchannel where the majority of call setup occurs. Used forMS to BTS communications before MS assigned to TCH.

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SDL Specification Description Language.

SDT SDL Developement Tool.

SDU Service Data Unit.

SDR Special Drawing Rights (an international “basket” currency forbilling).

SE Support Entity (GSM Rec. 12.00).

Secondary Cell A cell which is not optimized in the network and has aco-located neighbour whose cell boundary follows theboundary of the said cell. The secondary cell has a preferredband the same as that of its own frequency type.

SEF Support Entity Function (GSM Rec.12.00).

SFH Slow Frequency Hopping.

SI Screening Indicator.

SI Service Interworking.

SI Supplementary Information.

SIA Supplementary Information A.

SID Silence Descriptor.

SIF Signal Information Field. The bits of a message signal unitthat carry information for a certain user transaction; the SIFalways contains a label.

SIM Subscriber Identity Module. Removable module which isinserted into a mobile equipment; it is considered as part ofthe MS. It contains security related information (IMSI, Ki,PIN), other subscriber related information and the algorithmsA3 and A8.

SIMM Single Inline Memory module.

SIMM System Integrated Memory Module.

SIO Service Information Octet. Eight bits contained in a messagesignal unit, comprising the service indicator and sub-servicefield.

SITE BSC, BTS or collocated BSC-BTS site.

SIX Serial Interface eXtender. Converts interface levels to TTLlevels. Used to extend 2 serial ports from GPROC to externaldevices (RS232, RS422, and fibre optics).

SK Secondary Key. A database column attribute, the secondarykey indicates an additional index and/or usage as acomposite key.

SL Signalling Link.

SLNK Serial Link.

SLR Send Loudness Rating.

SLTM Signalling Link Test Message.

SM Switch Manager.

SM Summing Manager.

SMAE System Management Application Entity (CCITT Q795, ISO9596).

SMCB Short Message Cell Broadcast.

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SME Short Message Entity.

SMG Special Mobile Group.

SMP Motorola Software Maintenance Program.

SMS Short Message Service.

SMSCB Short Message Service Cell Broadcast.

SMS-SC Short Message Service - Service Centre.

SMS/PP Short Message Service/Point-to-Point.

Smt Short message terminal.

SN Subscriber Number.

SND SeND.

SNDR SeNDeR.

SNR Serial NumbeR.

SOA Suppress Outgoing Access (CUG SS).

SP Service Provider. The organisation through which thesubscriber obtains GSM telecommunications services. Thismay be a network operator or possibly a separate body.

SP Signalling Point.

SP Special Product.

SP SPare.

SPC Signalling Point Code.

SPC Suppress Preferential CUG.

SPI Signalling Point Inaccessible.

SPP Single Path Preselector.

SQE Signal Quality Error.

SQL Structured Query Language.

SRD Service Request Distributor.

SRES Signed RESponse (authentication).

SS Supplementary Service. A modification of, or a supplementto, a basic telecommunication service.

SS System Simulator.

SSA SCCP messages, Subsystem-allowed (see CCITT Q.712para 1.15).

SSAP Site System Audits Processor.

SSC Supplementary Service Control string.

SSF Subservice Field. The level 3 field containing the networkindicator and two spare bits.

SSM Signalling State Machine.

SSN SubSystem Number.

SSP Service Switching Point (an intelligent network element).

SSP SCCP messages, Subsystem-prohibited (see CCITT Q.712para 1.18).

SSP SubSystem Prohibited message.

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SSS Switching SubSystem (comprising the MSC and the LRs).

SS7 ANSI Signalling System No. 7 (alias C7).

STAN Statistical ANalysis (processor).

STAT STATistics.

stats Statistics.

STC System Timing Controller.

STMR Side Tone Masking rating.

SUERM Signal Unit Error Rate Monitor.

STP Signalling Transfer Point.

Superframe 51 traffic/associated control multiframes or 26broadcast/common control multiframes (period 6.12s).

Super user User account that can access all files, regardless ofprotection settings, and control all user accounts.

SURF Sectorized Universal Receiver Front-end (Used inHorizonmacro).

SVC Switch Virtual Circuit.

SVM SerVice Manager.

SVN Software Version Number.

SW Software.

SWFM SoftWare Fault Management.

sync synchronize/synchronization.

Synchronization burst Period of RF carrier less than one timeslot whose modulationbit stream carries information for the MS to synchronize itsframe to that of the received signal.

SYS SYStem.

SYSGEN SYStem GENeration. The Motorola procedure for loading aconfiguration database into a BTS.

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TT Timer.

T Transparent.

T Type only.

T43 Type 43 Interconnect Board. Provides interface to 12unbalanced (6-pair) 75 ohm (T43 coax connectors) lines for2 Mbit/s circuits (See BIB).

TA Terminal Adaptor. A physical entity in the MS providingterminal adaptation functions (see GSM 04.02).

TA Timing Advance.

TAC Type Approval Code.

TACS Total Access Communications System (European analoguecellular system).

TAF Terminal Adaptation Function.

TATI Transmit Antenna Transceiver Interface. The TATI consistsof RF combining equipments, either Hybrid or CavityCombining. (See CCB).

TAXI Transparent Asynchronous Transmitter/Receiver Interface(physical layer).

TBD To Be Determined.

TBR Technical Basis for Regulation.

TBUS TDM Bus.

TC Transaction Capabilities.

TCAP Transaction Capabilities Application Part (of SignallingSystem No. 7).

TCB TATI Control Board.

TCH Traffic CHannel. GSM logical channels which carry eitherencoded speech or user data.

TCH/F A full rate TCH.

TCH/F2.4 A full rate TCH at � 2.4 kbit/s.

TCH/F4.8 A full rate TCH at 4.8 kbit/s.

TCH/F9.6 A full rate TCH at 9.6 kbit/s.

TCH/FS A full rate Speech TCH.

TCH/H A half rate TCH.

TCH/H2.4 A half rate TCH at � 2.4 kbit/s.

TCH/H4.8 A half rate TCH at 4.8 kbit/s.

TCH/HS A half rate Speech TCH).

TCI Transceiver Control Interface.

TCP/IP Transmission Control Protocol/Internet Protocol.

TC-TR Technical Commitee Technical Report.

TCU Transceiver Control Unit.

TDF Twin Duplexed Filter. (Used in M-Cellhorizon).

TDM Time Division Multiplexing.

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Glos–49

TDMA Time Division Multiple Access.

TDU TopCell Digital Unit.

TE Terminal Equipment. Equipment that provides the functionsnecessary for the operation of the access protocols by theuser.

Tei Terminal endpoint identifier.

TEI Terminal Equipment Identity.

TEMP TEMPorary.

TEST TEST control processor.

TFA TransFer Allowed.

TFP TransFer Prohibited.

TFTP Trivial File Transfer Protocol.

TI Transaction Identifier.

Timeslot The multiplex subdivision in which voice and signalling bitsare sent over the air. Each RF carrier is divided into 8timeslots.

Timing advance A signal sent by the BTS to the MS. It enables the MS toadvance the timing of its transmission to the BTS so as tocompensate for propagation delay.

TLV Type, Length and Value.

TM Traffic Manager.

TMI TDM Modem Interface board. Provides analogue interfacefrom IWF to modems for 16 circuits (p/o IWF).

TMM Traffic Metering and Measuring.

TMN Telecommunications Management Network. Theimplementation of the Network Management functionalityrequired for the PLMN is in terms of physical entities whichtogether constitute the TMN.

TMSI Temporary Mobile Subscriber Identity. A unique identitytemporarily allocated by the MSC to a visiting mobilesubscriber to process a call. May be changed between callsand even during a call, to preserve subscriber confidentiality.

TN Timeslot Number.

TON Type Of Number.

Traffic channels Channels which carry user’s speech or data (see also TCH).

Traffic unit Equivalent to an erlang.

Training sequence Sequence of modulating bits employed to facilitate timingrecovery and channel equalization in the receiver.

TRAU Transcoder Rate Adaption Unit.

TRU TopCell Radio unit.

TRX Transceiver(s). A network component which can serve fullduplex communication on 8 full-rate traffic channels accordingto specification GSM 05.02. If Slow Frequency Hopping(SFH) is not used, then the TRX serves the communicationon one RF carrier.

TS Technical Specification.

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TS TeleService.

TS TimeSlot (see Timeslot).

TSA TimeSlot Acquisition.

TSA TimeSlot Assignment.

TSDA Transceiver Speech & Data Interface.

TSC Training Sequence Code.

TSI TimeSlot Interchange.

TSDI Transceiver Speech and Data Interface.

TSM Transceiver Station Manager.

TSW Timeslot SWitch.

TTCN Tree and Tabular Combined Notation.

TTL Transistor to Transistor Logic.

TTY TeleTYpe (refers to any terminal).

TU Traffic Unit.

TUP Telephone User Part (SS7).

TV Type and Value.

Tx Transmit(ter).

TXF Transmit Function (of the RTF).

TXPWR Transmit PoWeR. Tx power level in theMS_TXPWR_REQUEST and MS_TXPWR_CONFparameters.

TxBPF Transmit Bandpass Filter.

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UUA Unnumbered Acknowledgment. A message sent from the

MS to the BSS to acknowledge release of radio resourceswhen a call is being cleared.

UDI Unrestricted Digital Information.

UDP User Datagram Protocol.

UDUB User Determined User Busy.

UHF Ultra High Frequency.

UI Unnumbered Information (Frame).

UIC Union International des Chemins de Fer.

UID User ID. Unique number used by the system to identify theuser.

UL Upload (of software or database from an NE to a BSS).

Um Air interface.

UMTS Universal Mobile Telecommunication System.

UPCMI Uniform PCM Interface (13 bit).

UPD Up to Date.

Uplink Physical link from the MS towards the BTS (MS transmits,BTS receives).

UPS Uninterruptable Power Supply.

UPU User Part Unavailable.

Useful part of burst That part of the burst used by the demodulator; differs fromthe full burst because of the bit shift of the I and Q parts ofthe GMSK signal.

USSD Unstructured Supplementary Service Data.

UUS User-to-User Signalling supplementary service.

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VV Value only.

VA Viterbi Algorithm (used in channel equalizers).

VAD Voice Activity Detection. A process used to identify presenceor absence of speech data bits. VAD is used with DTX.

VAP Videotex Access Point.

VBS Voice Broadcast Service.

VC Virtual Circuit.

VCO Voltage Controlled Oscillator.

VCXO Voltage Controlled Crystal Oscillator.

VDU Visual Display Unit.

VGCS Voice Group Call Service.

VLR Visitor Location Register. A GSM network element whichprovides a temporary register for subscriber information for avisiting subscriber. Often a part of the MSC.

VLSI Very Large Scale Integration (in ICs).

VMSC Visited MSC. (Recommendation not to be used).

VOX Voice Operated Transmission.

VPLMN Visited PLMN.

VSC Videotex Service Centre.

V(SD) Send state variable.

VSP Vehicular Speaker Phone.

VSWR Voltage Standing Wave Ratio.

VTX host The components dedecated to Videotex service.

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Glos–53

WWAN Wide Area Network.

WPA Wrong Password Attempts (counter).

WS Work Station. The remote device via which O&M personnelexecute input and output transactions for networkmanagement purposes.

WSF Work Station Function block.

WWW World Wide Web.

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Glos–54

XX.25 CCITT specification and protocols for public packet-switched

networks (see PSPDN).

X.25 link A communications link which conforms to X.25 specificationsand uses X.25 protocol (NE to OMC links).

XBL Transcoder to BSS Link. The carrier communications linkbetween the Transcoder (XCDR) and the BSS.

XCB Transceiver Control Board (p/o Transceiver).

XCDR Full-rate Transcoder. Provides speech transcoding and 4:1submultiplexing (p/o BSS, BSC or XCDR).

XCDR board The circuit board required to perform speech transcoding atthe BSS or (R)XCDR). Also known as the MSI (XCDR)board. Interchangeable with the GDP board.

XFER Transfer.

XID eXchange IDentifier.

X-Term X terminal window.

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ZZC Zone Code

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Glos–56



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Answers

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Answers–1

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Answers–4

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Answers–5

Chapter 5 Appendix B – Exercise Answers

1. The A-bis message to be transmitted is PAGING CoMmanD. The BSC receives a PAGING REQUEST message from the MSC but on the A-bis link this is converted into a PAGING CoMmanD message(TS GSM 08.58 section 8).

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1. The MS will respond with a RACH (TS GSM 04.08) with an ESTABLISHMENT CAUSE – ANSWER TO PAGING. The BTS will allocate an SDCCH channel in response to this and send an ESTablish INDication message type on the A-bis interface to the BSC.

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Answers–6

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Answers–7

Chapter 6 Appendix A – Answers

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Answers–8

Documents

CHAPTER 2 GSM AIR INTERFACE COMMON BEARER [2MBIT/S BTS…read.pudn.com/downloads61/ebook/212957/SYS01.pdf · · 2004-02-23chapter 2 gsm air interface review chapter 3 gsm air interface