MOTOROLA CP-02 GSM Handbook
MOTOROLA CP-02 GSM Handbook
MOTOROLA CP-02 GSM Handbook
PRINCIPLES OF CELLULAR FEATURES OF GSM GSM NETWORK GSM TERRESTRIAL CHANNELS ON THE AIR
TELECOMMUNICATIONS COMPONENTS INTERFACES INTERFACE
CHAPTER 6 CHAPTER 7 CHAPTER 8 CP02 EXERCISE APPENDIX 1
CHANNELS ON THE AIR RADIO INTERFACE INTRODUCTION TO
INTERFACE OPTIMIZATION MICROCELLULAR
APPENDIX 2 GLOSSARY OF TERMS
Cellular Infrastructure Group
ISSUE 5 REVISION 4
CP02
INTRODUCTION TO DIGITAL CELLULAR
CP02
INTRODUCTION TO
DIGITAL CELLULAR
FOR TRAINING
PURPOSES ONLY
CP02
INTRODUCTION TO DIGITAL
CELLULAR
ISSUE 5 REVISION 4
CP02
Introduction to Digital Cellular
Copyrights
The Motorola products described in this document may include copyrighted Motorola computer
programs stored in semiconductor memories or other media. Laws in the United States and other
countries preserve for Motorola certain exclusive rights for copyright computer programs, including the
exclusive right to copy or reproduce in any form the copyright computer program. Accordingly, any
copyright Motorola computer programs contained in the Motorola products described in this document
may 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 by
implication, estoppel or otherwise, any license under the copyrights, patents or patent applications of
Motorola, except for the rights that arise by operation of law in the sale of a product.
Restrictions
The software described in this document is the property of Motorola. It is furnished under a license
agreement 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 by
law. No part of the software or documentation may be reproduced, transmitted, transcribed, stored
in a retrieval system, or translated into any language or computer language, in any form or by any
means, without prior written permission of Motorola.
Accuracy
While reasonable efforts have been made to assure the accuracy of this document, Motorola
assumes no liability resulting from any inaccuracies or omissions in this document, or from the use
of the information obtained herein. Motorola reserves the right to make changes to any products
described herein to improve reliability, function, or design, and reserves the right to revise this
document and to make changes from time to time in content hereof with no obligation to notify any
person of revisions or changes. Motorola does not assume any liability arising out of the application
or use of any product or circuit described herein; neither does it convey license under its patent
rights of others.
Trademarks
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
Chapter 1
Principles of Cellular Telecommunications . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Principles of Cellular Telecommunications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–1
Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2
Advantages of Cellular Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2
Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–4
Frequency Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–6
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–6
Cell Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
Large Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
Small Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
The Trade Off – Large vs Small . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
Frequency Re-use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10
Co-channel Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10
Adjacent Channel Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10
Sectorization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–12
Using Sectored Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–14
4 Site/3 Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–14
Switching and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–16
Chapter 2
Features of GSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Features of GSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–1
Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–2
Noise Robust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–4
Flexibility and Increased Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–6
Use of Standardised Open Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–8
Improved Security and Confidentiality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–10
Flexible Handover Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–12
ISDN Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–14
2B+D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–14
Chapter 3
GSM Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
GSM Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–1
GSM Network Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–2
Mobile Station (MS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–4
Mobile Equipment (ME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–6
Subscriber Identity Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–8
Base Station System (BSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–10
Base Station Controller (BSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–12
Base Transceiver Station – BTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–12
BSS Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–14
Transcoder (XCDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–16
Network Switching System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–18
Mobile Services Switching Centre (MSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–20
Home Location Register (HLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–22
Visitor Location Register (VLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Location Area Identity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Temporary Mobile Subscriber Identity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Mobile Subscriber Roaming Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Equipment Identity Register (EIR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–26
Authentication Centre (AUC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–28
Authentication Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–28
Interworking Function (IWF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–30
Echo Canceller (EC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–32
Operations and Maintenance System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Network Management Centre (NMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Operations and Maintenance Centre (OMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Network Management Centre (NMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–36
Operations and Maintenance Centre (OMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–38
The Network In Reality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–40
Chapter 4
GSM Terrestrial Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
GSM Terrestrial Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–2
2 Mbit/s Trunk 30-channel PCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–4
X.25 Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–6
ITU-TS Signalling System #7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–8
A-bis (LAPD) Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–10
Interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–12
Interface Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–14
Chapter 5
Channels on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Channels on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–1
Transmission of Analogue and Digital Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–2
Modulation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–2
Transmission of Digital Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–4
Phase Shift Keying (PSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–4
Gaussian Minimum Shift Keying (GMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–4
Physical and Logical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–6
GSM Physical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–6
GSM Logical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–8
Traffic Channels (TCH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–8
GSM Control Channel Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
BCCH Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
CCCH Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
DCCH Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
GSM Logical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–12
Control Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–12
Channel Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–18
Channel Combinations and Timeslots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–18
Multiframes and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–20
The 26-frame Traffic Channel Multiframe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–20
The 51-frame Control Channel Multiframe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–22
The 51-frame Control Channel Multiframe (BCCH/CCCH) . . . . . . . . . . . . . . . . . . 5–24
The 51-frame Control Channel Multiframe – DCCH/8 (SDCCH and SACCH) . . 5–26
The 51-frame Control Channel Multiframe – Combined Structure . . . . . . . . . . . . 5–28
Superframes and Hyperframes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–30
Mobile Activity – Transmit and Receive Timeslots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–32
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–32
GSM Basic Call Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–34
Chapter 6
Channels on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Channel Coding on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–1
GSM Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–2
Burst Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–4
Chapter 7
Radio Interface Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Radio Interface Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–1
Transmission Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–2
Battery Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
Voice Activity Detection (VAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–6
Discontinuous Transmission (DTX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–6
Discontinuous Reception (DRX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–8
Multipath Fading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–10
Equalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–12
Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–14
Frequency Hopping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–16
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–16
Chapter 8
Introduction to Microcellular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Introduction to Microcellular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–2
What is Microcell? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–2
Why Deploy Microcells? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–2
How are Microcells Deployed? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–4
Building Penetration from Externally Mounted Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–6
Antenna Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–8
Directional Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–8
Omni Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–8
I .......................................................................... G–18
K ......................................................................... G–20
L ......................................................................... G–20
M ......................................................................... G–21
N ......................................................................... G–25
O ......................................................................... G–26
P ......................................................................... G–27
Q ......................................................................... G–29
R ......................................................................... G–30
S ......................................................................... G–32
T ......................................................................... G–36
U ......................................................................... G–38
V ......................................................................... G–39
W ........................................................................ G–40
X ......................................................................... G–40
Z ......................................................................... G–40
General information
Important notice
If this manual was obtained when you attended a Motorola training course, it will not be
updated or amended by Motorola. It is intended for TRAINING PURPOSES ONLY. If it
was supplied under normal operational circumstances, to support a major software
release, then corrections will be supplied automatically by Motorola in the form of
General Manual Revisions (GMRs).
Purpose
Motorola Global System for Mobile Communications (GSM) Technical Education manuals
are intended to support the delivery of Technical Education only and are not intended to
replace the use of Customer Product Documentation.
WARNING
Failure to comply with Motorola’s operation, installation and maintenance
instructions may, in exceptional circumstances, lead to serious injury or death.
These manuals are not intended to replace the system and equipment training offered by
Motorola, although they can be used to supplement and enhance the knowledge gained
through such training.
About this
manual
The manual contains ...
!
" # !
Cross references
Throughout this manual, cross references are made to the chapter numbers and section
names. The section name cross references are printed bold in text.
This manual is divided into uniquely identified and numbered chapters that, in turn, are
divided into sections. Sections are not numbered, but are individually named at the top
of each page, and are listed in the table of contents.
Text conventions
The following conventions are used in the Motorola GSM manuals to represent keyboard
input 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 environmental
variables that appear on the screen are shown like this.
Warning
WARNING
Do not touch the victim with your bare hands until the electric circuit is
broken.
Switch off. If this is not possible, protect yourself with dry insulating
material and pull or push the victim clear of the conductor.
Artificial
respiration
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, cover
the wound with a dry dressing.
3. Do not apply oil or grease in any form.
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) and
follow up with a written report by fax +44 (0)1793 430987 (fax).
4. Collect evidence from the equipment under the guidance of the MCSC.
Introduction
The following describes how warnings and cautions are used in this manual and in all
manuals 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, for
example, the use of adhesives and solvents, as well as those inherent in the equipment.
WARNING
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 or
unterminated fibre optic cables connected to data in/out connectors.
Cautions
Definition
A caution means that there is a possibility of damage to systems, or individual items of
equipment within a system. However, this presents no danger to personnel.
CAUTION
Do not use test equipment that is beyond its calibration due date when testing
Motorola base stations.
General warnings
Introduction
Observe the following warnings during all phases of operation, installation and
maintenance of the equipment described in the Motorola GSM manuals. Failure to
comply with these warnings, or with specific warnings elsewhere in the Motorola GSM
manuals, violates safety standards of design, manufacture and intended use of the
equipment. Motorola assumes no liability for the customer’s failure to comply with these
requirements.
Warning labels
Personnel working with or operating Motorola equipment must comply with any warning
labels fitted to the equipment. Warning labels must not be removed, painted over or
obscured in any way.
Specific
warnings
Warnings particularly applicable to the equipment are positioned on the equipment and
within the text of this manual. These must be observed by all personnel at all times when
working with the equipment, as must any other warnings given in text, on the illustrations
and on the equipment.
High voltage
Certain Motorola equipment operates from a dangerous high voltage of 230 V ac single
phase or 415 V ac three phase mains which is potentially lethal. Therefore, the areas
where the ac mains power is present must not be approached until the warnings and
cautions 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 must
be set to off and locked.
Within the United Kingdom (UK) regard must be paid to the requirements of the
Electricity at Work Regulations 1989. There may also be specific country legislation
which need to be complied with, depending on where the equipment is used.
RF radiation
High RF potentials and electromagnetic fields are present in the base station equipment
when in operation. Ensure that all transmitters are switched off when any antenna
connections have to be changed. Do not key transmitters connected to unterminated
cavities or feeders.
Refer to the following standards:
S ANSI IEEE C95.1-1991, IEEE Standard for Safety Levels with Respect to Human
Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz.
S CENELEC 95 ENV 50166-2, Human Exposure to Electromagnetic Fields High
Frequency (10kHz to 300GHz).
Laser radiation
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 or unterminated fibre optic
cables connected to data in/out connectors.
Lifting
equipment
When dismantling heavy assemblies, or removing or replacing equipment, the competent
responsible person must ensure that adequate lifting facilities are available. Where
provided, lifting frames must be used for these operations. When equipments have to be
manhandled, reference must be made to the Manual Handling of Loads Regulations
1992 (UK) or to the relevant manual handling of loads legislation for the country in which
the equipment is used.
Do not ...
... substitute parts or modify equipment.
Because of the danger of introducing additional hazards, do not install substitute parts or
perform any unauthorized modification of equipment. Contact Motorola if in doubt to
ensure 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 material
Beryllium or its oxide Beryllia or both. These materials are especially hazardous if:
S Beryllium materials are absorbed into the body tissues through the skin, mouth, or
a wound.
S The dust created by breakage of Beryllia is inhaled.
S Toxic fumes are inhaled from Beryllium or Beryllia involved in a fire.
See the Beryllium health and safety precautions section for further information.
Definitions
This standard establishes two sets of maximum permitted exposure limits, one for
controlled environments and another, that allows less exposure, for uncontrolled
environments. These terms are defined by the standard, as follows:
Uncontrolled environment
Uncontrolled environments are locations where there is the exposure of individuals who
have no knowledge or control of their exposure. The exposures may occur in living
quarters or workplaces where there are no expectations that the exposure levels may
exceed those shown for uncontrolled environments in the table of maximum permitted
exposure ceilings.
Controlled environment
Controlled environments are locations where there is exposure that may be incurred by
persons who are aware of the potential for exposure as a concomitant of employment, by
other cognizant persons, or as the incidental result of transient passage through areas
where analysis shows the exposure levels may be above those shown for uncontrolled
environments but do not exceed the values shown for controlled environments in the
table of maximum permitted exposure ceilings.
Maximum
permitted
exposures
The maximum permitted exposures prescribed by the standard are set in terms of
different parameters of effects, depending on the frequency generated by the equipment
in question. At the frequency range of this Personal Communication System equipment,
1930-1970MHz, the maximum permitted exposure levels are set in terms of power
density, whose definition and relationship to electric field and magnetic field strengths are
described by the standard as follows:
S + E + 377
2
H2
377
where E and H are expressed in units of V/m and A/m, respectively, and S in units of
W/m 2. Although many survey instruments indicate power density units, the actual
quantities measured are E or E2 or H or H2.
Maximum
permitted
exposure
ceilings
Within the frequency range, the maximum permitted exposure ceiling for uncontrolled
environments is a power density (mW/cm2) that equals f/1500, where f is the frequency
expressed in MHz, and measurements are averaged over a period of 30 minutes. The
maximum permitted exposure ceiling for controlled environments, also expressed in
mW/cm 2, is f/300 where measurements are averaged over 6 minutes. Applying these
principles to the minimum and maximum frequencies for which this equipment is intended
to be used yields the following maximum permitted exposure levels:
If you plan to operate the equipment at more than one frequency, compliance should be
assured at the frequency which produces the lowest exposure ceiling (among the
frequencies 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 demonstrating
compliance, but this equipment operates at power levels orders of magnitude higher, and
the exclusion is not applicable.
Whether a given installation meets the maximum permitted exposure ceilings depends, in
part, upon antenna type, antenna placement and the output power to which this
equipment is adjusted. The following example sets forth the distances from the antenna
to which access should be prevented in order to comply with the uncontrolled and
controlled environment exposure limits as set forth in the ANSI IEEE standards and
computed above.
Example
calculation
For a base station with the following characteristics, what is the minimum distance from
the antenna necessary to meet the requirements of an uncontrolled environment?
Transmit frequency 1930MHz
Base station cabinet output power, P +39.0 dBm (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:
G + 4pr W
2
Pin
Where W is the maximum permissible power density in W/m2 and r is the safe distance
from the antenna in metres, the desired distance can be calculated as follows:
NOTE
The above result applies only in the direction of maximum radiation of the
antenna. Actual installations may employ antennas that have defined radiation
patterns and gains that differ from the example set forth above. The distances
calculated can vary depending on the actual antenna pattern and gain.
Power density
measurements
While installation calculations such as the above are useful and essential in planning and
design, validation that the operating facility using this equipment actually complies will
require making power density measurements. For information on measuring RF fields for
determining compliance with ANSI IEEE C95.1-1991, see IEEE Recommended Practice
for 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 be
purchased 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 this
equipment are urged to consult these standards in determining whether a given
installation complies with the applicable limits.
Other equipment
Whether a given installation meets ANSI standards for human exposure to radio
frequency radiation may depend not only on this equipment but also on whether the
environments being assessed are being affected by radio frequency fields from other
equipment, the effects of which may add to the level of exposure. Accordingly, the overall
exposure may be affected by radio frequency generating facilities that exist at the time
the 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 in
determining whether a particular installation meets the FCC requirements.
Introduction
Beryllium (Be), is a hard silver/white metal. It is stable in air, but burns brilliantly in
Oxygen.
With the exception of the naturally occurring Beryl ore (Beryllium Silicate), all Beryllium
compounds and Beryllium metal are potentially highly toxic.
Health issues
Beryllium Oxide is used within some components as an electrical insulator. Captive
within the component it presents no health risk whatsoever. However, if the component
should 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 symptoms
of Berylliosis are similar to Pneumonia and may be identified by all or any of the
following:
Mild poisoning causes fever, shortness of breath, and a cough that produces
yellow/green sputum, or occasionally bloodstained sputum. Inflammation of the mucous
membranes of the nose, throat, and chest with discomfort, possibly pain, and difficulty
with swallowing and breathing.
Severe poisoning causes chest pain and wheezing which may progress to severe
shortness of breath due to congestion of the lungs. Incubation period for lung symptoms
is 2–20 days.
Exposure to moderately high concentrations of Beryllium in air may produce a very
serious condition of the lungs. The injured person may become blue, feverish with rapid
breathing and raised pulse rate. Recovery is usual but may take several months. There
have been deaths in the acute stage.
Chronic response. This condition is more truly a general one although the lungs are
mainly affected. There may be lesions in the kidneys and the skin. Certain features
support the view that the condition is allergic. There is no relationship between the
degree of exposure and the severity of response and there is usually a time lag of up to
10 years between exposure and the onset of the illness. Both sexes are equally
susceptible. The onset of the illness is insidious but only a small number of exposed
persons develop this reaction.
First aid
Seek immediate medical assistance. The casualty should be removed immediately from
the exposure area and placed in a fresh air environment with breathing supported with
Oxygen where required. Any contaminated clothing should be removed. The casualty
should be kept warm and at rest until medical aid arrives.
Skin contact
Possible irritation and redness at the contact area. Persistent itching and blister
formations can occur which usually resolve on removal from exposure.
First aid
Wash area thoroughly with soap and water. If skin is broken seek immediate medical
assistance.
Eye contact
May cause severe irritation, redness and swelling of eyelid(s) and inflammation of the
mucous membranes of the eyes.
First aid
Flush eyes with running water for at least 15 minutes. Seek medical assistance as soon
as possible.
Handling
procedures
Removal of components from printed circuit boards (PCBs) is to take place only at
Motorola approved repair centres.
The removal station will be equipped with extraction equipment and all other protective
equipment necessary for the safe removal of components containing Beryllium Oxide.
If during removal a component is accidently opened, the Beryllium Oxide dust is to be
wetted into a paste and put into a container with a spatula or similar tool. The
spatula/tool used to collect the paste is also to be placed in the container. The container
is then to be sealed and labelled. A suitable respirator is to be worn at all times during
this operation.
Components which are successfully removed are to be placed in a separate bag, sealed
and labelled.
Disposal
methods
Beryllium Oxide or components containing Beryllium Oxide are to be treated as
hazardous waste. All components must be removed where possible from boards and put
into sealed bags labelled Beryllium Oxide components. These bags must be given to the
safety and environmental adviser for disposal.
Under no circumstances are boards or components containing Beryllium Oxide to be put
into the general waste skips or incinerated.
General cautions
Introduction
Observe the following cautions during operation, installation and maintenance of the
equipment described in the Motorola GSM manuals. Failure to comply with these
cautions or with specific cautions elsewhere in the Motorola GSM manuals may result in
damage to the equipment. Motorola assumes no liability for the customer’s failure to
comply with these requirements.
Caution labels
Personnel working with or operating Motorola equipment must comply with any caution
labels fitted to the equipment. Caution labels must not be removed, painted over or
obscured in any way.
Specific cautions
Cautions particularly applicable to the equipment are positioned within the text of this
manual. These must be observed by all personnel at all times when working with the
equipment, as must any other cautions given in text, on the illustrations and on the
equipment.
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 by
mishandling. Wear an approved earth strap when adjusting or handling digital boards.
See Devices sensitive to static for further information.
Introduction
Certain metal oxide semiconductor (MOS) devices embody in their design a thin layer of
insulation that is susceptible to damage from electrostatic charge. Such a charge applied
to the leads of the device could cause irreparable damage.
These charges can be built up on nylon overalls, by friction, by pushing the hands into
high insulation packing material or by use of unearthed soldering irons.
MOS devices are normally despatched from the manufacturers with the leads shorted
together, for example, by metal foil eyelets, wire strapping, or by inserting the leads into
conductive plastic foam. Provided the leads are shorted it is safe to handle the device.
Special handling
techniques
In the event of one of these devices having to be replaced observe the following
precautions when handling the replacement:
S Always wear an earth strap which must be connected to the electrostatic point
(ESP) on the equipment.
S Leave the short circuit on the leads until the last moment. It may be necessary to
replace the conductive foam by a piece of wire to enable the device to be fitted.
S Do not wear outer clothing made of nylon or similar man made material. A cotton
overall is preferable.
S If possible work on an earthed metal surface. Wipe insulated plastic work surfaces
with an anti-static cloth before starting the operation.
S All metal tools should be used and when not in use they should be placed on an
earthed surface.
S Take care when removing components connected to electrostatic sensitive
devices. These components may be providing protection to the device.
When mounted onto printed circuit boards (PCBs), MOS devices are normally less
susceptible to electrostatic damage. However PCBs should be handled with care,
preferably by their edges and not by their tracks and pins, they should be transferred
directly from their packing to the equipment (or the other way around) and never left
exposed on the workbench.
Introduction
The following manuals provide the information needed to operate, install and maintain the
Motorola GSM equipment.
Generic manuals
The following are the generic manuals in the GSM manual set, these manuals are
release dependent:
Tandem OMC
The following Tandem OMC manuals are part of the GSM manual set for systems
deploying Tandem S300 and 1475:
Scaleable OMC
The following Scaleable OMC manuals replace the equivalent Tandem OMC manuals in
the GSM manual set:
Related manuals
The following are related Motorola GSM manuals:
Service manuals
The following are the service manuals in the GSM manual set, these manuals are not
release dependent. The internal organization and makeup of service manual sets may
vary, they may consist of from one to four separate manuals, but they can all be ordered
using the overall catalogue number shown below:
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.
Catalogue
number
The Motorola 68P catalogue number is used to order manuals.
Ordering
manuals
All orders for Motorola manuals must be placed with your Motorola Local Office or
Representative. Manuals are ordered using the catalogue number. Remember, specify
the manual issue required by quoting the correct suffix letter.
Principles of Cellular
Telecommunications
Chapter 1
Principles of Cellular Telecommunications . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Principles of Cellular Telecommunications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–1
Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2
Advantages of Cellular Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2
Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–4
Frequency Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–6
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–6
Cell Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
Large Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
Small Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
The Trade Off – Large vs Small . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–8
Frequency Re-use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10
Co-channel Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10
Adjacent Channel Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–10
Sectorization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–12
Using Sectored Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–14
4 Site/3 Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–14
Switching and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–16
Objectives
On completion of this section the student will be able to:
S Name the main components of a cellular network and describe their functionality.
S Understand the options available for site configuration.
Overview
A cellular telephone system links mobile station (MS) subscribers into the public
telephone system or to another cellular system’s MS subscriber.
Information sent between the MS subscriber and the cellular network uses radio
communication. This removes the necessity for the fixed wiring used in a traditional
telephone installation.
Due to this, the MS subscriber is able to move around and become fully mobile, perhaps
travelling in a vehicle or on foot.
Advantages of
Cellular
Communications
Cellular networks have many advantages over the existing “land” telephone networks.
There are advantages for the network provider as well as the mobile subscriber.
Overview
S
S
S
S
S
Network Components
GSM networks are made up of Mobile services Switching Centres (MSC), Base Station
Systems (BSS)and Mobile Stations (MS). These three entities can be broken down
further into smaller entities; such as, within the BSS we have Base Station Controllers,
Base Transceiver Stations and Transcoders. These smaller network elements, as they
are referred to, will be discussed later in the course. For now we will use the three major
entities.
With the MSC, BSS and MS we can make calls, receive calls, perform billing etc, as any
normal PSTN network would be able to do. The only problem for the MS is that all the
calls made or received are from other MSs. Therefore, it is also necessary to connect the
GSM network to the PSTN.
Mobile Stations within the cellular network are located in “cells”, these cells are provided
by the BSSs. Each BSS can provide one or more cells, dependent on the manufacturers
equipment.
The cells are normally drawn as hexagonal, but in practice they are irregularly shaped,
this is as a result of the influence of the surrounding terrain, or of design by the network
planners.
Network Components
Frequency Spectrum
Introduction
The frequency spectrum is very congested, with only narrow slots of bandwidth allocated
for cellular communications. The list opposite shows the number of frequencies and
spectrum allocated for GSM, Extended GSM 900 (EGSM), GSM 1800 (DCS1800) and
PCS1900.
A single Absolute Radio Frequency Channel Number (ARFCN) or RF carrier is actually a
pair of frequencies, one used in each direction (transmit and receive). This allows
information to be passed in both directions. For GSM900 and EGSM900 the paired
frequencies are separated by 45 MHz, for DCS1800 the separation is 95 MHz and for
PCS1900 separation is 80 MHz.
For each cell in a GSM network at least one ARFCN must be allocated, and more may
be allocated to provide greater capacity.
The RF carrier in GSM can support up to eight Time Division Multiple Access (TDMA)
timeslots. That is, in theory, each RF carrier is capable of supporting up to eight
simultaneous telephone calls, but as we will see later in this course although this is
possible, network signalling and messaging may reduce the overall number from eight
timeslots per RF carrier to six or seven timeslots per RF carrier, therefore reducing the
number of mobiles that can be supported.
Unlike a PSTN network, where every telephone is linked to the land network by a pair of
fixed wires, each MS only connects to the network over the radio interface when
required. Therefore, it is possible for a single RF carrier to support many more mobile
stations than its eight TDMA timeslots would lead us to believe. Using statistics, it has
been found that a typical RF carrier can support up to 15, 20 or even 25 MSs. Obviously,
not all of these MS subscribers could make a call at the same time, but it is also unlikely
that all the MS subscribers would want to make a call at the same time. Therefore,
without knowing it, MSs share the same physical resources, but at different times.
Frequency Range
GSM 900
S Receive (uplink) 890-915 MHz
S Transmit (downlink) 935-960 MHz
S 124 Absolute Radio Frequency Channels (ARFCN)
EGSM 900
S Receive (uplink) 880-915 MHz
S Transmit (downlink) 925-960 MHz
S 174 Absolute Radio Frequency Channels (ARFCN)
PCS 1900
S Receive (uplink) 1850-1910 MHz
S Transmit (downlink) 1930-1990 MHz
S 299 Absolute Radio Frequency Channels (ARFCN)
ARFCN
S Bandwidth = 200 KHz
S 8 TDMA timeslots
Cell Size
The number of cells in any geographic area is determined by the number of MS
subscribers who will be operating in that area, and the geographic layout of the area
(hills, lakes, buildings etc).
Large Cells
The maximum cell size for GSM is approximately 70 km in diameter, but this is
dependent on the terrain the cell is covering and the power class of the MS. In GSM, the
MS can be transmitting anything up to 8 Watts; obviously, the higher the power output of
the MS the larger the cell size. If the cell site is on top of a hill, with no obstructions for
miles, then the radio waves will travel much further than if the cell site was in the middle
of a city, with many high-rise buildings blocking the path of the radio waves.
Generally large cells are employed in:
S Remote areas.
S Coastal regions.
S Areas with few subscribers.
S Large areas which need to be covered with the minimum number of cell sites.
Small Cells
Small cells are used where there is a requirement to support a large number of MSs, in a
small geographic region, or where a low transmission power may be required to reduce
the effects of interference. Small cells currently cover 200 m and upwards.
Typical uses of small cells:
S Urban areas.
S Low transmission power required.
S High number of MSs.
Cell Size
Frequency Re-use
Standard GSM has a total of 124 frequencies available for use in a network. Most
network providers are unlikely to be able to use all of these frequencies and are generally
allocated a small subset of the 124.
Example:
A network provider has been allocated 48 frequencies to provide coverage over a large
area, let us take for example Great Britain.
As we have already seen, the maximum cell size is approximately 70 km in diameter,
thus our 48 frequencies would not be able to cover the whole of Britain.
To overcome this limitation the network provider must re-use the same frequencies over
and over again, in what is termed a “frequency re-use pattern”.
When planning the frequency re-use pattern the network planner must take into account
how often to use the same frequencies and determine how close together the cells are,
otherwise co-channel and/or adjacent channel interference may occur. The network
provider will also take into account the nature of the area to be covered. This may range
from a densely populated city (high frequency re-use, small cells, high capacity) to a
sparsely populated rural expanse (large omni cells, low re-use, low capacity).
Co-channel
Interference
This occurs when RF carriers of the same frequency are transmitting in close proximity to
each other, the transmission from one RF carrier interferes with the other RF carrier.
Adjacent
Channel
Interference
This occurs when an RF source of a nearby frequency interferes with the RF carrier.
Frequency Re-use
Sectorization
The cells we have looked at up to now are called omni-directional cells. That is each site
has a single cell and that cell has a single transmit antenna which radiates the radio
waves to 360 degrees.
The problem with employing omni-directional cells is that as the number of MSs
increases in the same geographical region, we have to increase the number of cells to
meet the demand. To do this, as we have seen, we have to decrease the size of the cell
and fit more cells into this geographical area. Using omni-directional cells we can only go
so far before we start introducing co-channel and adjacent channel interference, both of
which degrade the cellular network’s performance.
To gain a further increase in capacity within the geographic area we can employ a
technique called “sectorization”. Sectorization splits a single site into a number of cells,
each cell has transmit and receive antennas and behaves as an independent cell.
Each cell uses special directional antennas to ensure that the radio propagation from one
cell is concentrated in a particular direction. This has a number of advantages: firstly, as
we are now concentrating all the energy from the cell in a smaller area 60, 120, 180
degrees instead of 360 degrees, we get a much stronger signal, which is beneficial in
locations such as “in-building coverage”. Secondly, we can now use the same
frequencies in a much closer re-use pattern, thus allowing more cells in our geographic
region which allows us to support more MSs.
Site Sectorization
3 cell site
3 Transmit/receive
antenna
4 Site/3 Cell
A typical re-use pattern used in GSM planning is the 4 site/3 cell.
For example, the network provider has 36 frequencies available, and wishes to use the 4
site/3 cell re-use pattern he may split the frequencies up as follows:
C ell C ell C ell C ell C ell C ell C ell C ell C ell C ell C ell C ell
A1 A2 A3 B1 B2 B3 C 1 C 2 C 3 D1 D2 D3
1 2 3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32 33 34 35 36
In this configuration each cell has a total of 3 carriers and each site has a total of 9
carriers. If the provider wished to reconfigure to a 3 site/3 cell then the result would be:
As can be seen from the table, each cell now has 4 carriers and each site has 12
carriers. This has the benefit of supporting more subscribers in the same geographic
region, but problems could arise with co-channel and adjacent channel interference.
4 site/3 cell
BTS
SITE
MS
BTS
SITE BTS
SITE
MS
MS
BTS BTS
SITE SITE
BSC
SITE
WITH MS
XC DR
BTS BTS
SITE SITE
MS
BTS
BTS SITE
SITE
WITH
C OLLOC ATED
BSC
RXC DR
BTS SITE
WITH
C OLLOC ATED
BSC
MSC MSC
Features of GSM
Chapter 2
Features of GSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Features of GSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–1
Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–2
Noise Robust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–4
Flexibility and Increased Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–6
Use of Standardised Open Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–8
Improved Security and Confidentiality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–10
Flexible Handover Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–12
ISDN Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–14
2B+D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–14
Enhanced Range Of Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–16
Speech Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–18
Telephony . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–18
Emergency Calls (with/without SIM Card inserted in MS) . . . . . . . . . . . . . . . . . . . 2–18
Short Message Service Point To Point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–18
Short Message Cell Broadcast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–18
Advanced Message Handling Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–18
Dual Personal and Business Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–18
Data Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–20
Supplementary Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–22
Features of GSM
Section
Objectives
On completion of this section the student will be able to:
S Understand the advantages of a digital air interface.
S Realise the implications of using standard open interfaces.
S Recognise the enhanced range of services that may be offered by a GSM network.
S Understand the part played by the mobile station in the handover process.
S Appreciate how software is used to provide flexibility.
Features of GSM
Cellular telephone systems provide the MS subscriber and network provider with many
advantages over a standard telephone network, but there are still many drawbacks.
Compatibility
The rapid development of analogue cellular networks during the 1980s resulted in many
different cellular systems which were incompatible with one another.
The need for a common standard for mobile telecommunications was therefore obvious,
and so an executive body was set up to co-ordinate the complicated task of specifying
the new standardized network.
GSM has been specified and developed by many European countries working in
co-operation with each other. The result is a cellular system which has been
implemented throughout Europe and many parts of the world.
An additional advantage resulting from this is that there is a large market for GSM
equipment. This means that manufacturers can produce equipment in higher quantities
and of better quality, and also, due to the number of manufacturers, a competitive and
aggressive pricing structure exists. This results in lower costs for the MS subscriber and
the network operators.
Compatibility
ITALY
PORTUGAL
GERMANY
U.K.
SPAIN
AUSTRIA NORWAY
SWITZERLAND
FINLAND
NETHERLANDS
FRANC E
DENMARK
SWEDEN
Noise Robust
In cellular telephone systems, such as AMPs, TACs or NMT the MS communicates with
the cell site by means of analogue radio signals. Although this technique can provide an
excellent audio quality (it is widely used for stereo radio broadcasting, for example), it is
vulnerable to noise, as anyone who has tried to receive broadcast stereo with a poor
aerial will testify!
The noise which interferes with the current system may be produced by any of the
following sources:
S A powerful or nearby external source (a vehicle ignition system or a lightning bolt,
perhaps);
S Another transmission on the same frequency (co-channel interference);
S Another transmission “breaking through” from a nearby frequency (adjacent
channel interference);
S Background radio noise intruding because the required signal is too weak to
exclude it.
In order to combat the problems caused by noise, GSM uses digital technology instead
of analogue.
By using digital signals, we can manipulate the data and include sophisticated error
protection, detection and correction software. The overall result is that the signals
passed across the GSM air interface withstand more errors (that is, we can locate and
correct more errors than current analogue systems). Due to this feature, the GSM air
interface in harsh RF environments can produce a usable signal, where analogue
systems would be unable to. This leads to better frequency re-use patterns and more
capacity.
Sources of Noise
S
S
S
S
S
GSM Answers
S
S
S
S
Flexibility/Increased Capacity
S
S
S
S
!
ÇÇ
Ç
Ç
ÇÇ
ÇÇ
ÇÇ
ISDN Compatibility
Integrated Services Digital Network (ISDN) is a standard that most developed countries
are committed to implement. This is a new and advanced telecommunications network
designed to carry voice and user data over standard telephone lines.
Major telephone companies in Europe, North America, Hong Kong, Australia and Japan
are committed to commercial enterprises using ISDN.
The GSM network has been designed to operate with the ISDN system and provides
features which are compatible with it. GSM can provide a maximum data rate of 9.6
kbit/s while ISDN provides much higher data rates than this (standard rate 64 kbit/s,
primary rate 2.048 Mbit/s).
2B+D
This refers to the signals and information which may be carried on an ISDN line. There
are effectively three connections, one for signalling (‘D’) and the other two for data or
speech (‘2B’).
ISDN Compatibility
S
Speech Services
The following services listed involve the transmission of speech information and would
make up the basic service offered by a network provider:
Telephony
Provides for normal MS originated/terminated voice calls.
Emergency Calls
(with/without SIM
Card inserted in
MS)
The number “112” has been agreed as the international emergency call number. This
should place you in contact with the emergency services (Police, Fire, Ambulance)
whichever country you are in.
Short Message
Service Point To
Point
Provides the transmission of an acknowledged short message (128 bytes maximum)
from a service centre to a MS. It is also intended that the MS should be able to send
short messages to land-based equipment. This will obviously depend upon the
equipment owned by the land-based user.
Short Message
Cell Broadcast
Provides the transmission of an unacknowledged short message (75 bytes maximum)
from a service centre in the fixed network to all MSs within one cell. This may carry
information from the network provider, for example traffic information or advertising.
Advanced
Message
Handling Service
Provides message submission and delivery from the storage from a public Message
Handling System (MHS) for example, electronic mail.
Dual Personal
and Business
Numbers
Permits the allocation of dual telephone numbers to a single subscriber. This will allow
calls to be made and be billed either to ‘‘business” or ‘‘personal” numbers.
Speech Services
S
S
S
Data Services
Data can be sent over the air using some of the present systems, but this requires
specially designed “add ons” to protect the data content in the harsh environment of the
air interface.
Special provision is made in the GSM technical specifications for data transmission.
Therefore, like ISDN, GSM is “specially designed” for data transmission. GSM can be
considered as an extension of ISDN into the wireless environment.
Text files, images, messages and fax may all be sent over the GSM network. The data
rates available are 2.4 kbit/s, 4.8 kbit/s and 9.6 kbit/s.
In addition to supporting data transmission, GSM also provides for Group 3 Fax
transmission.
Data Services
S
S
Supplementary
Services
A supplementary service is a modification of, or a supplement to, a basic
telecommunication service. The network provider will probably charge extra for these
services or use them as an incentive to join their network.
Here is a list of some of the optional supplementary subscriber services that could be
offered to GSM subscribers:
Number Identification
S Receiving party requests calling number to be shown.
S Calling party requests calling number not to be shown.
Call Barring
S Bar all incoming or all outgoing calls.
S Bar specific incoming or outgoing calls.
Call Forwarding
S Forward all calls.
S Forward calls when subscriber is busy.
S Forward calls if subscriber does not answer.
S Forward calls if subscriber cannot be located.
Call Completion
S Enable incoming call to wait until subscriber completes current call.
S Enable subscriber to place incoming calls on hold.
Charging
S Display current cost of call.
Multi-party
S Three party service.
S Conference calling.
Supplementary Services
S
S
S
S
S
Chapter 3
GSM Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
GSM Network Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–1
GSM Network Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–2
Mobile Station (MS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–4
Mobile Equipment (ME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–6
Subscriber Identity Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–8
Base Station System (BSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–10
Base Station Controller (BSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–12
Base Transceiver Station – BTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–12
BSS Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–14
Transcoder (XCDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–16
Network Switching System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–18
Mobile Services Switching Centre (MSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–20
Home Location Register (HLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–22
Visitor Location Register (VLR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Location Area Identity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Temporary Mobile Subscriber Identity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Mobile Subscriber Roaming Number . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–24
Equipment Identity Register (EIR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–26
Authentication Centre (AUC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–28
Authentication Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–28
Interworking Function (IWF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–30
Echo Canceller (EC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–32
Operations and Maintenance System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Network Management Centre (NMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Operations and Maintenance Centre (OMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–34
Network Management Centre (NMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–36
Operations and Maintenance Centre (OMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–38
The Network In Reality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–40
Section
Objectives
On completion of this section the student will be able to:
S Name the major components of a GSM network and know the functionality of
these components.
S Draw a diagram illustrating how the components of the GSM network are
connected.
NMC
VLR
HLR
OMC AUC
EIR
MSC
PSTN EC IWF
XCDR
ME
BSC
SIM BTS
Mobile Station
S RF power capability
S Encryption capability
S Frequency capability
Base Transceiver
Station – BTS
The BTS provides the air interface connection with the MS. I also has a limited amount of
control functionality which reduces the amount of traffic passing between the BTS and
BSC. The functions of the BTS are shown opposite. Each BTS will support 1 or more
cells.
Where the BSC and BTS are both shown to control a function, the control is divided
between the two, or may be located wholly at one.
BSS Configurations
As we have mentioned, a BSC may control several BTSs, the maximum number of BTSs
which may be controlled by one BSC is not specified by GSM.
Individual manufacturer’s specifications may vary greatly.
The BTSs and BSC may either be located at the same cell site “co-located”, or located
at different sites “Remote”. In reality most BTSs will be remote, as there are many more
BTSs than BSCs in a network.
Another BSS configuration is the daisy chain. A BTS need not communicate directly with
the BSC which controls it, it can be connected to the BSC via a chain of BTSs.
Daisy chaining reduces the amount of cabling required to set up a network as a BTS can
be connected to its nearest BTS rather than all the way to the BSC.
Problems may arise when chaining BTSs, due to the transmission delay through the
chain. The length of the chain must, therefore, be kept sufficiently short to prevent the
round trip speech delay becoming too long.
Other topologies are also permitted, including stars and loops. Loops are used to
introduce redundancy into the network, for example if a BTS connection was lost, the
BTS may still be able to communicate with the BSC if a second connection is available.
BSS Configurations
C ell Site
C ell Site
C ell Site
Transcoder (XCDR)
The Transcoder (XCDR) is required to convert the speech or data output from the MSC
(64 kbit/s PCM), into the form specified by GSM specifications for transmission over the
air interface, that is, between the BSS and MS (64 kbit/s to 16 kbit/s and vice versa)
The 64 kbit/s Pulse Code Modulation (PCM) circuits from the MSC, if transmitted on the
air interface without modification, would occupy an excessive amount of radio bandwidth.
This would use the available radio spectrum inefficiently. The required bandwidth is
therefore reduced by processing the 64 kbit/s circuits so that the amount of information
required to transmit digitized voice falls to a gross rate of 16 kbit/s.
The transcoding function may be located at the MSC, BSC, or BTS.
The content of the 16 kbit/s data depends on the coding algorithm used. There are two
speech coding algorithms available and selecting which one to use depends on the
capabilities of the mobile equipment and the network configuration.
The Full Rate speech algorithm is supported by all mobiles and networks. It produces 13
kbit/s of coded speech data plus 3 kbit/s of control data which is commonly referred to as
TRAU data (Transcoder Rate Adaption Unit). The TRAU data on the downlink will be
used by the BTS and therefore removed from the 13 k of speech data before
transmission on the air interface. the 13 kbit/s of speech data is processed at the BTS to
form a gross rate of 22.8 kbit/s on the air interface which includes forward error
correction. In the uplink direction the BTS adds in TRAU data which will be used by the
transcoder.
Enhanced Full Rate is an improved speech coding algorithm and is only supported by
Phase 2+ mobiles and is optional in the Network. It produces 12.2 kbit/s from each 64
kbit/s PCM channel. The TRAU data in this case is made up to 3.8 kbit/s to keep the
channel rate to and from the BTS at 16 kbit/s as for Full Rate. As with Full Rate the
TRAU data is used at the BTS and Transcoder.
For data transmissions the data is not transcoded but data rate adapted from 9.6 kbit/s
(4.8 kbit/s or 2.4 kbit/s may also be used) up to a gross rate of 16 kbit/s for transmission
over the terrestrial interfaces, again this 16 kbit/s contains a 3 kbit/s TRAU.
As can be seen from the diagram opposite, although the reason for transcoding was to
reduce the data rate over the air interface, the number of terrestrial links is also reduced
approximately on a 4:1 ratio.
Transcoder
TCH
TCH
TCH
TCH
SIG
0 31
30 TCH
120 GSM TRAFFIC CHANNELS
30 TCH
01 16 31
(C7)
Information Control
Operations
and
Maintenance System
S
S
S
S
Location Area
Identity
Cells within the Public Land Mobile Network (PLMN) are grouped together into
geographical areas. Each area is assigned a Location Area Identity (LAI), a location area
may typically contain 30 cells. Each VLR controls several LAIs and as a subscriber
moves from one LAI to another, the LAI is updated in the VLR. As the subscriber moves
from one VLR to another, the VLR address is updated at the HLR.
Temporary
Mobile
Subscriber
Identity
The VLR controls the allocation of new Temporary Mobile Subscriber Identity (TMSI)
numbers and notifies them to the HLR. The TMSI will be updated frequently, this makes
it very difficult for the call to be traced and therefore provides a high degree of security
for the subscriber. The TMSI may be updated in any of the following situations:
S Call setup.
S On entry to a new LAI.
S On entry to a new VLR.
Mobile
Subscriber
Roaming Number
As a subscriber may wish to operate outside its “home” system at some time, the VLR
can also allocate a Mobile Station Roaming Number (MSRN). This number is assigned
from a list of numbers held at the VLR (MSC). The MSRN is then used to route the call
to the MSC which controls the base station in the MSs current location.
The database in the VLR can be accessed by the IMSI, the TMSI or the MSRN.
Typically there will be one VLR per MSC.
S
S
#!# $# ##
"# #
"#
$
"#
!%
"#
"# !%
"#
Authentication
Process
To discuss the authentication process we will assume that the VLR has all the
information required to perform that authentication process (Kc, SRES and RAND). If
this information is unavailable, then the VLR would request it from the HLR/AUC.
1. Triples (Kc, SRES and RAND) are stored at the VLR.
2. The VLR sends RAND via the MSC and BSS, to the MS (unencrypted).
3. The MS, using the A3 and A8 algorithms and the parameter Ki stored on the MS
SIM card, together with the received RAND from the VLR, calculates the values of
SRES and Kc.
4. The MS sends SRES unencrypted to the VLR
5. Within the VLR the value of SRES is compared with the SRES received from the
mobile. If the two values match, then the authentication is successful.
6. If cyphering is to be used, Kc from the assigned triple is passed to the BTS.
7. The mobile calculates Kc from the RAND and A8 and Ki on the SIM.
8. Using Kc, A5 and the GSM hyperframe number, encryption between the MS and
the BSS can now occur over the air interface.
Note: The triples are generated at the AUC by:
RAND = Randomly generated number.
SRES = Derived from A3 (RAND, Ki).
Kc = Derived from A8 (RAND, Ki).
A3 = From 1 of 16 possible algorithms defined on allocation of IMSI and
creation of SIM card.
A8 = From 1 of 16 possible algorithms defined on allocation of IMSI and
creation of SIM card.
Ki = Authentication key, assigned at random together with the versions of
A3 and A8.
The first time a subscriber attempts to make a call, the full authentication process takes
place.
However, for subsequent calls attempted within a given system control time period, or
within a single system provider’s network, authentication may not be necessary, as the
data generated during the first authentication will still be available.
Authentication Process
Interworking Function
Operations
and
Maintenance System
4ĆWire (Rx)
2ĆWire
(Tx)
Echo
Hybrid
Echo Canceller
Operations
and
Maintenance System
Overview
The operations and maintenance system provides the capability to manage the GSM
network remotely.
This area of the GSM network is not currently tightly specified by the GSM specifications,
it is left to the network provider to decide what capabilities they wish it to have. The
Operations and Maintenance System comprises of two parts:
Network
Management
Centre (NMC)
The Network Management Centre (NMC) has a view of the entire PLMN and is
responsible for the management of the network as a whole. The NMC resides at the top
of the hierarchy and provides global network management.
Operations and
Maintenance
Centre (OMC)
The Operations and Maintenance Centre (OMC) is a centralized facility that supports the
day to day management of a cellular network as well as providing a database for long
term network engineering and planning tools. An OMC manages a certain area of the
PLMN thus giving regionalized network management.
NMC
OMC OMC
OMC
REGION 2 REGION 3
REGION 1
NETWORK
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
MANAGEMENT MANAGEMENT
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
MAN-MAC HINE
INTERFAC E
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
FAULT
MANAGEMENT DATABASE
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
C OMMUNIC ATIONS
HANDLER
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ C ONFIGURATION
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
MANAGEMENT
ÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓÓ
PERFORMANC E
MANAGEMENT
A typical network (for example, UK) will have approximately the following number of
network components.
MS
Chapter 4
GSM Terrestrial Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
GSM Terrestrial Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–2
2 Mbit/s Trunk 30-channel PCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–4
X.25 Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–6
ITU-TS Signalling System #7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–8
A-bis (LAPD) Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–10
Interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–12
Interface Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–14
Section
Objectives
On completion of this course the student will be able to:
S Identify the protocols used on the terrestrial interfaces between the GSM system
entities.
Introduction
The terrestrial interfaces comprise all the connections between the GSM system entities,
apart from the Um, or air interface.
They are represented on the diagram opposite by the lines that connect the various
entities together.
The GSM terrestrial interfaces and message-transport mediums all conform to ITU-TSS
specifications widely used throughout the world. As we stated previously, it is from this
use of standardized interfaces that the flexibility of GSM largely derives.
The terrestrial interfaces transport the traffic across the system and allow the passage of
the thousands of data messages necessary to make the system function. They transport
the data for software downloads and uploads, the collection of statistical information and
the implementation of operations and maintenance commands.
The standard interfaces used are as follows:
S 2 Mbit/s.
S Signalling System ITU-TSS #7 (“C7” or ‘‘SS#7”).
S X.25 (packet switched data); (LAPB).
S A bis using the LAPD protocol (Link Access Procedure “D”).
Whatever the interfaces and whatever their function, they will often share a common
physical bearer (cable) between two points, for example, the MSC and a BSS.
OSI LAYERS
4-7 X.25 C7
User Applications Applications
Application
3
Network X.25 ABIS
MTP (C7)
2
Link LAPB LAPD
1 2 Mbit/s Trunk
Physical
Typical Configuration
0 Frame Alignment/ Error Checking/ Signalling/ Alarms
1–15 Traffic
16 Signalling (other TS may also be used)
17–31 Traffic
TS = Timeslot
2 Mbit/s Trunks
NMC
VLR VLR
HLR
AUC
OMC
EIR
IWF IWF
MS
COĆLOCATED
ENTITIES
BTS BTS
BTS
MS
MS
X.25 Interfaces
The diagram opposite shows the X.25 packet data connections of the system.
The X.25 packets provide the OMC with communications to all the entities over which it
has control and oversight. Remember that these X.25 connections will commonly be
contained within 2 Mbit/s links using a dedicated timeslot.
Note that the X.25 connection from the OMC to the BSS may be “nailed through” (or
permanently connected by software) at the MSC, or may be supported by a completely
independent physical route.
X.25 Interfaces
Acronyms:
BSSAP Base Station System Application Part
BSSMAP Base Station System Management Application Part
DTAP Direct Transfer Application Part
ISUP ISDN User Part
MAP Mobile Application Part
SCCP Signalling Connection Control Part
TUP Telephone User Part
TCAP Transaction Capabilities Application Part
MAP BSSAP
(DTAP +
TUP ISUP
TC AP BSSMAP)
SC C P
MTP Level 3
MTP Level 2
MTP Level 1
2 Mbit/s Trunk
C7 Interfaces
FRAME CHECK
SEQUENCE
NMC
BSS
XC AUC
OMC
EIR
MSC
MSC
XC IWF EC EC IWF XC
MS
PSTN
LAPD
MS
MS LAPDm
(AirĆinterface)
Interconnections
The interface between the BSC and the MSC is a standardized ITU-TSS signalling
system No7 (C7) interface, referred to as the A interface.
The interface supports the following connections:
S BSC–MSC, BSC–BTS and MSC–MS.
S Operation and Maintenance interface.
S All call processing functions.
These interfaces are commonly transported on a physical bearer, the 2 Mbit/s link.
Each of these 2 Mbit/s links provide 32 x 64 kbit/s channels (timeslots), the first channel
(TS0) is used for frame alignment, leaving 31 channels available for carry “traffic
channels” or “signalling interfaces”.
The signalling protocols used between GSM networks are:
S X.25 (LAPB), 1 x 64 kbit/s timeslot.
S C7 (SS7), 1 x 64 kbit/s timeslot (BSSAP, MAP, TCAP, SCCP, MTP).
S LAPD, 1 x 64 kbit/s timeslot.
The X.25 protocol is used between the BSC–OMC.
The C7 link is between the BSC–MSC, dependent on what type of signalling is required
will depend on which part of the C7 protocol will be used (for example, MSC–MS will use
a subset of BSSAP called DTAP to transfer messages).
The LAPD protocol is used between the BSC–BTS, this is normally 64 kbit/s as stated
but some manufactures offer 16 kbit/s links as well.
The link between the BSC–CBC does not use a specified protocol. The choice of
protocol is decided between the PLMN provider and the CBC provider. (Typically X.25 or
C7 may be used.)
BSC Connections
Interface Names
Each interface specified within the GSM system has a name associated with it. The
diagram opposite illustrates the names of all the interfaces specified by
GSM.
⇔
⇔
⇔
⇔
⇔
⇔
⇔
⇔
⇔
G D
B H
B
C
E
F
A
Abis
Um
Chapter 5
Channels on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Channels on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–1
Transmission of Analogue and Digital Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–2
Modulation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–2
Transmission of Digital Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–4
Phase Shift Keying (PSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–4
Gaussian Minimum Shift Keying (GMSK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–4
Physical and Logical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–6
GSM Physical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–6
GSM Logical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–8
Traffic Channels (TCH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–8
GSM Control Channel Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
BCCH Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
CCCH Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
DCCH Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–10
GSM Logical Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–12
Control Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–12
Channel Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–18
Channel Combinations and Timeslots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–18
Multiframes and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–20
The 26-frame Traffic Channel Multiframe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–20
The 51-frame Control Channel Multiframe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–22
The 51-frame Control Channel Multiframe (BCCH/CCCH) . . . . . . . . . . . . . . . . . . 5–24
The 51-frame Control Channel Multiframe – DCCH/8 (SDCCH and SACCH) . . 5–26
The 51-frame Control Channel Multiframe – Combined Structure . . . . . . . . . . . . 5–28
Superframes and Hyperframes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–30
Mobile Activity – Transmit and Receive Timeslots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–32
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–32
GSM Basic Call Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5–34
Section
Objectives
On completion of this section the student will be able to:
S Understand why GMSK is used to modulate the GSM signal.
S Name the four most commonly used channel combinations and provide reasons
why each would be used.
S State the reason why multiframes, superframes and hyperframes are utilized.
Modulation
Techniques
There are three methods of modulating a signal so that it may be transmitted over the air:
S Amplitude Modulation (AM)
Amplitude Modulation is very simple to implement for analogue signals but it is
prone to noise.
S Frequency Modulation (FM)
Frequency Modulation is more complicated to implement but provides a better
tolerance to noise.
S Phase Modulation (PM)
Phase Modulation provides the best tolerance to noise but it is very complex to
implement for analogue signals and therefore is rarely used.
Digital signals can use any of the modulation methods, but phase modulation provides
the best noise tolerance. Since phase modulation can be implemented easily for digital
signals, this is the method which is used for the GSM air interface. Phase Modulation is
known as Phase Shift Keying (PSK) when applied to digital signals.
Modulation Techniques
Phase Shift
Keying (PSK)
Phase modulation provides a high degree of noise tolerance. However, there is a
problem with this form of modulation. When the signal changes phase abruptly, high
frequency components are produced, thus a wide bandwidth would be required for
transmission.
GSM has to be as efficient as possible with the available bandwidth. Therefore, it is not
this technique, but a more efficient development of phase modulation that is actually
used by the GSM air interface, it is called Gaussian Minimum Shift Keying (GMSK).
Gaussian
Minimum Shift
Keying (GMSK)
With GMSK, the phase change which represents the change from a digital ‘1’ or a ‘0’
does not occur instantaneously as it does with Binary Phase Shift Keying (BPSK).
Instead it occurs over a period of time and therefore the addition of high frequency
components to the spectrum is reduced.
With GMSK, first the digital signal is filtered through a Gaussian filter. This filter causes
distortion to the signal, the corners are rounded off. This distorted signal is then used to
phase shift the carrier signal. The phase change therefore is no longer instantaneous but
spread out.
Frequency Spectrum
GSM Physical
Channels
A single GSM RF carrier can support up to eight MS subscribers simultaneously. The
diagram opposite shows how this is accomplished. Each channel occupies the carrier for
one eighth of the time. This is a technique called Time Division Multiple Access.
Time is divided into discrete periods called “timeslots”. The timeslots are arranged in
sequence and are conventionally numbered 0 to 7. Each repetition of this sequence is
called a “TDMA frame”.
Each MS telephone call occupies one timeslot (0–7) within the frame until the call is
terminated, or a handover occurs. The TDMA frames are then built into further frame
structures according to the type of channel. We shall later examine how the information
carried by the air interface builds into frames and multi-frames and discuss the
associated timing.
For such a system to work correctly, the timing of the transmissions to and from the
mobiles is critical. The MS or Base Station must transmit the information related to one
call at exactly the right moment, or the timeslot will be missed. The information carried in
one timeslot is called a “burst”.
Each data burst, occupying its allocated timeslot within successive TDMA frames,
provides a single GSM physical channel carrying a varying number of logical channels
between the MS and BTS.
Timeslot
BURST
Traffic Channels
(TCH)
The traffic channel carries speech or data information. The different types of traffic
channel are listed below:
Full rate
S TCH/FS: Speech (13 kbit/s net, 22.8 kbit/s gross)
S TCH/EFR: Speech (12.2 kbit/s net, 22.8 kbit/s gross)
TCH/F9.6: 9.6 kbit/s – data
TCH/F4.8: 4.8 kbit/s – data
TCH/F2.4 2.4 kbit/s – data
Half rate
S TCH/HS: speech (6.5 kbit/s net, 11.4 kbit/s gross)
TCH/H4.8 4.8 kbit/s – data
TCH/H2.4 2.4 kbit/s – data
Acronyms:
Speech Channels
Speech channels are supported by two different methods of coding known as Full Rate
(FR) and Enhanced Full Rate (EFR). Enhanced Full Rate coding provides a speech
service that has improved voice quality from the original Full Rate speech coding, whilst
using the same air interface bandwidth. EFR employs a new speech coding algorithm
and additions to the full rate channel coding algorithm to accomplish this improved
speech service, however, it will only be supported by Phase 2+ mobiles onwards.
TCH
Traffic Channels
ACRONYMS
NB = Normal Burst
SACCH = Slow Associated Control Channel
FACCH = Fast Associated Control Channel
BCCH Group
The Broadcast Control Channels are downlink only (BSS to MS) and comprise the
following:
S BCCH carries information about the network, a MSs present cell and the
surrounding cells. It is transmitted continuously as its signal strength is measured
by all MSs on surrounding cells.
S The Synchronizing Channel (SCH) carries information for frame synchronization.
S The Frequency Control Channel (FCCH) provides information for carrier
synchronization.
CCCH Group
The Common Control Channel Group works in both uplink and downlink directions.
S Random Access Channel (RACH) is used by MSs to gain access to the system.
S 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 a
Stand-alone Dedicated Control Channel (SDCCH). The PCH is used by the
system to call a MS. The PCH and AGCH are never used at the same time.
S Cell Broadcast Channel (CBCH) is used to transmit messages to be broadcast to
all MSs within a cell, for example, road traffic information, sporting results.
DCCH Group
Dedicated Control Channels are assigned to a single MS for call setup and subscriber
validation. DCCH comprises:
S Stand-alone Dedicated Control Channel (SDCCH) which supports the transfer of
Data to and from the MS during call setup and validation.
S Associated Control Channel. This consists of Slow ACCH which is used for radio
link measurement and power control messages. Fast ACCH is used to pass
“event” type messages, for example, handover messages. Both FACCH and
SACCH operate in uplink and downlink directions.
Acronyms
BCCH Broadcast Control Channel CCCH Common Control Channel
DCCH Dedicated Control Channel ACCH Associated Control Channel
SDCCH Stand-alone Dedicated Control RACH Random Access Channel
Channel PCH Paging Channel
AGCH Access Grant Channel CBCH Cell Broadcast Channel
Control Channels
"!&$" !!
"(! ! "! )
)!
!! %
'# ! "(! !
"(! !
Control
Channels
– Frame number.
– Base Site Identity Code (BSIC).
The MS will monitor BCCH information from surrounding cells and store the information
from the best six cells. The SCH information on these cells is also stored so that the MS
may quickly resynchronize when it enters a new cell.
CCH
Control Channel
BCCH
Broadcast Control Channel
- downlink only
Synchronizing
BCCH Channels
SCH FCCH
Control
Channels
Active MSs must frequently monitor both BCCH and CCCH. The CCCH will be
transmitted on the RF carrier with the BCCH.
Acronyms:
CCH
Control Channel
CCCH
Common Control Channel
- Bidirectional
RACH CBCH
- uplink - downlink
PCH/AGCH
- downlink
Control
Channels
All of the control channels are required for system operation, however, in the same way
that we allow different users to share the radio channel by using different timeslots to
carry the conversation data, the control channels share timeslots on the radio channel at
different times. This allows efficient passing of control information without wasting
capacity which could be used for call traffic. To do this we must organise the timeslots
between those which will be used for traffic and those which will carry control signalling.
Acronyms:
SDCCH Stand-alone Dedicated Control Channel
SACCH Slow Associated Control Channel
FACCH Fast Associated Control Channel
CCH
Control Channel
DCCH
Dedicated Control Channel
- Bidirectional
SDCCH ACCH
FACCH SACCH
Channel
Combinations
The different logical channel types mentioned are grouped into what are called channel
combinations. The four most common channel combinations are listed below:
The Half Rate Channel Combination (when introduced) will be very similar to the Full
Rate Traffic Combination.
S Half Rate Traffic Channel Combination – TCH16/FACCH + SACCH
Channel
Combinations
and Timeslots
The channel combinations we have identified are sent over the air interface in a selected
timeslot.
Some channel combinations may be sent on any timeslot, but others must be sent on
specific timeslots. Below is a table mapping the channels combinations to their
respective timeslots:
Traffic Any timeslot
Broadcast 0,2,4,6 (0 must be used first) *
Dedicated Any timeslot
C ombined 0 only
The diagram opposite illustrates how these different channel combinations may be
mapped onto the TDMA frame structure.
2
The 26-frame
Traffic Channel
Multiframe
The illustration opposite shows the time relationship between time-slot, TDMA frame, and
the 26-frame multiframe. Some of the times shown are approximate numbers as the
GSM recommendations actually state the exact values as fractions rather than in decimal
form (for example, the exact duration of a time-slot is 15/26 ms).
Note:
The 12th frame (no. 13) in the 26-frame traffic channel multiframe is used by the Slow
Associated Control Channel (SACCH) which carries link control information to and from
the MS–BTS. Each timeslot in a cell allocated to traffic channel usage will follow this
format, that is, 12 bursts of traffic, 1 burst of SACCH, 12 bursts of traffic and 1 idle.
The duration of a 26-frame traffic channel multiframe is 120 ms (26 TDMA frames).
When half rate is used, each frame of the 26-frame traffic channel multiframe allocated
for traffic will now carry two MS subscriber calls (the data rate for each MS is halved over
the air interface). Although the data rate for traffic is halved, each MS still requires the
same amount of SACCH information to be transmitted, therefore frame 12 WILL BE
USED as SACCH for one half of the MSs and the others will use it as their IDLE frame,
and the same applies for frame 25, this will be used by the MSs for SACCH (those who
used frame 12 as IDLE) and the other half will use it as their IDLE frame.
0.577 ms
Timeslot
TDMA frame
7 6 5 4 3 2 1 0
4.615 ms
2 1 0
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
Idle SACCH
Multiframe
25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
120 ms
The 51-frame
Control Channel
Multiframe
The 51-frame structure used for control channels is considerably more complex than the
26-frame structure used for the traffic channels. The 51-frame structure occurs in several
forms, depending on the type of control channel and the network provider’s
requirements.
0.577 ms
Timeslot
TDMA frame
7 6 5 4 3 2 1 0
4.615 ms
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
Multiframe
235.365 ms
Time
The 51-frame
Control Channel
Multiframe
(BCCH/CCCH)
The BCCH/CCCH 51-frame structure illustrated on the opposite page will apply to
timeslot 0 of each TDMA frame on the ‘BCCH carrier’ (the RF carrier frequency to which
BCCH is assigned on a per cell basis). In the diagram, each vertical step represents one
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 is
fairly obvious because RACH is the only control channel in the BCCH/CCCH group which
works in the uplink direction. In the downlink direction (BSS–MS), the arrangement is
more interesting. Starting at frame 0 of the 51-frame structure, the first timeslot 0 is
occupied by a frequency burst (‘F’ in the diagram), the second by a synchronizing 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 CCCH traffic
(C), that is, to either PCH (mobile paging channel) or AGCH (access grant channel).
Then follows, in timeslot 0 of frames 10 and 11, a repeat of the frequency and
synchronising bursts (F and S), four further CCCH bursts (C) and so on. Note that the
last timeslot 0 in the sequence (the fifty-first frame – frame 50) is idle.
BCCH/CCCH Multiframe
50
ÈÈÈÈÈ I
KEY
50 R
R
R
C R
R= RACH (Random)
B= BCCH (Broadcast) R
F= FCCH (Frequency) R
S= SCH (Sync.) R
C R
C= CCCH (Common)
I= Idle R
S R
40 F 40 R
R
R
C R
R
R
R
C R
R
S R
30 F 30 R
R
R
C R
R
R
R
C R
R
S R
20 F 20 R
R
R
C R
R
R
R
C R
R
S R
10 F 10 R
R
R
C R
R
R
R
B R
R
Downlink S
Uplink R
0 F 0 R
The 51-frame
Control Channel
Multiframe –
DCCH/8 (SDCCH
and SACCH)
The diagram opposite shows the 51-frame structure used to accommodate eight
SDCCHs, although, as it takes two repetitions of the multiframe to complete the entire
sequence, it may be more logical to think of it as a 102-frame structure. This structure
may be transmitted on any timeslot.
Note that the SACCHs (shaded) are associated with the SDCCHs. It is important to
remember that each SDCCH has an SACCH just like a traffic channel.
i.e. D0 associated with A0
D1 associated with A1
..
..
..
..
..
D7 associated with A7
Note: The downlink and uplink channels are staggered in order to give the mobile time to
process the received message and formulate a response.
DCCH/8 Multiframe
ÈÈÈÈÈ ÈÈÈÈÈ
50
ÈÈÈÈÈ I
ÈÈÈÈÈ
101 I 50
ÈÈÈÈÈ ÈÈÈÈÈ
101
I I
A0 A4
ÈÈÈÈÈ ÈÈÈÈÈ
I I
KEY
D = SDCCH/8 (Dedicated)
A3 A7 A = SACCH/C8 (Associated)
I = Idle
D7 D7
A2 A6
40 40 D6 D6
A1 A5
D5 D5
A0 A4
D4 D4
30 30
D7 D7
D3 D3
D6 D6
D2 D2
D5 D5
20 20 D1 D1
D4 D4
D0 D0
ÈÈÈÈ ÈÈÈÈÈ
D3 D3 ÈÈÈÈ
I
ÈÈÈÈÈ I
10
ÈÈÈÈ
I
ÈÈÈÈ
I ÈÈÈÈÈ
ÈÈÈÈÈ
I
I
10
D2 D2 A7 A3
D1 D1 A6 A2
Downlink D0 D0 Uplink A5 A1
0 51 0 51
The 51-frame
Control Channel
Multiframe –
Combined
Structure
As we can see in the diagram opposite, each of the control channel types are present on
a single timeslot. The number of MSs which can effectively use this cell is therefore
reduced, as we now only have 3 CCCH groups and 4 SDCCHs, which translates into
fewer pages and simultaneous cell setups.
A typical use of this type of control channel timeslot is in rural areas, where the
subscriber density is low.
Combined Multiframe
ÈÈÈÈ ÈÈÈÈÈ
ÏÏÏÏ
ÈÈÈÈ ÏÏÏÏÏ
ÈÈÈÈÈ
50 I 101 I 50 101
ÏÏÏÏ ÏÏÏÏÏA3
D2 D2
ÏÏÏÏ ÏÏÏÏÏ
A1
ÏÏÏÏ ÏÏÏÏÏ R R
R
ÏÏÏÏ ÏÏÏÏÏ KEY R
ÏÏÏÏ ÏÏÏÏÏ
R= RACH (Random)
A0 A2 B= BCCH (Broadcast) D1 D1
ÏÏÏÏ ÏÏÏÏÏ
F= FCCH (Frequency)
S S S= SCH (Sync.)
C= CCCH (Common)
40 F F D= SDCCH/4 (Dedicated) 40
A= SACCH/C4 (Associated) D0 D0
D3 I= Idle
D3
R R
R R
R R
D2 D2 R
R
R R
S S R R
30 F F R R
R30 R
R R
D1 D1 R
R
R R
R R
R R
D0 D0 R
R
R R
S S R R
20 F F R R
R20 R
R R
C C R
R
R R
R R
C C ÏÏÏÏR
ÏÏÏÏÏ R
ÏÏÏÏ ÏÏÏÏÏ
10
S
F
S
F
10
ÏÏÏÏ
ÏÏÏÏ
A3
ÏÏÏÏÏ
ÏÏÏÏÏ
A1
ÏÏÏÏ ÏÏÏÏÏ
C C
ÏÏÏÏ
ÏÏÏÏ
A2
ÏÏÏÏÏ
ÏÏÏÏÏ
A0
R R
R R
B B
Downlink Uplink D3 D3
S S
0 F 51 F 0 51
3 h 28 min 53 s 760 ms
23 24 25
6.12 s
120 ms 235.65 ms
4.615 ms
TDMA frame
Overview
As the MS only transmits or receives its own physical channel (normally containing TCH
and SACCH) for one-eighth of the time, it uses the remaining time to monitor the BCCHs
of adjacent ‘target’ cells. It completes the process every 480 ms, or four 26-TCH
multiframes. The message that it sends to the BSS (on SACCH, uplink) contains the
Receive Signal Strength Indication (RSSI) of the adjacent cells, plus that of the link to
the BSS itself, plus an indication of the quality of the current connection. This quality
measurement is somewhat similar to a bit error rate test. Just as the mobile completes
one series of measurements, it completes sending the previous series to the BSS and
starts to send the latest series; thus the processes of compilation and transmission form
a continuous cycle.
Mobile Activity
Chapter 6
Channel Coding on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Channel Coding on the Air Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–1
GSM Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–2
Burst Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–4
Error Protection and Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–6
Speech Channel Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–8
Channel Coding for Enhanced Full Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–10
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–10
Preliminary Channel Coding for EFR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–10
Error Protection and Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–12
Control Channel Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–12
Data Channel Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–14
Mapping Logical Channels onto the TDMA Frame Structure . . . . . . . . . . . . . . . . . . . . . . 6–16
Interleaving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–16
Diagonal Interleaving – Speech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–18
Transmission – Speech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–20
Rectangular Interleaving – Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–22
Transmission – Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–22
Diagonal Interleaving – Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–24
Transmission – Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–24
Section
Objectives
On completion of this section the student will be able to:
S Draw the structure of a GSM burst and identify the purpose of each component.
S Have an understanding of the different mechanisms used to protect the air
interface from errors on speech, data and control channels.
GSM Bursts
The diagram opposite illustrates a GSM burst. It consists of several different elements.
These elements are described below:
S Info
This is the area in which the speech, data or control information is held.
S Guard Period
The BTS and MS can only receive the burst and decode it, if it is received within
the timeslot designated for it. The timing, therefore, must be extremely accurate,
but the structure does allow for a small margin of error by incorporating a ‘guard
period’ as shown in the diagram. To be precise, the timeslot is 0.577 ms long,
whereas the burst is only 0.546 ms long, therefore there is a time difference of
0.031 ms to enable the burst to hit the timeslot.
S Stealing Flags
These two bits are set when a traffic channel burst has been ‘‘stolen” by a FACCH
(the Fast Associated Control Channel). One bit set indicates that half of the block
has been stolen.
S Training Sequence
This is used by the receiver’s equalizer as it estimates the transfer characteristic of
the physical path between the BTS and the MS. The training sequence is 26 bits
long.
S Tail Bits
These are used to indicate the beginning and end of the burst.
FRAME 1 FRAME 2
GUARD
PERIOD NORMAL BURST GUARD
PERIOD
STEALING
FLAGS
TAIL BITS TAIL BITS
Burst Types
The diagram opposite shows the five types of burst employed in the GSM air interface.
All bursts, of whatever type, have to be timed so that they are received within the
appropriate timeslot of the TDMA frame.
The burst is the sequence of bits transmitted by the BTS or MS, the timeslot is the
discrete period of real time within which it must arrive in order to be correctly decoded by
the receiver:
S Normal Burst
The normal burst carries traffic channels and all types of control channels apart
from those mentioned specifically below. (Bi-directional).
S Frequency Correction Burst
This burst carries FCCH downlink to correct the frequency of the MS’s local
oscillator, effectively locking it to that of the BTS.
S Synchronization Burst
So called because its function is to carry SCH downlink, synchronizing the timing
of the MS to that of the BTS.
S Dummy Burst
Used when there is no information to be carried on the unused timeslots of the
BCCH Carrier (downlink only).
S Access Burst
This burst is of much shorter duration than the other types. The increased guard
period is necessary because the timing of its transmission is unknown. When this
burst is transmitted, the BTS does not know the location of the MS and therefore
the timing of the message from the MS can not be accurately accounted for. (The
Access Burst is uplink only.)
FRAME 1 FRAME 2
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
DUMMY BURST
Fixed Bits Training Sequence Fixed Bits
TB 57 26 57 TB GP
3 1 1 3
ACCESS BURST
Synchronisation Sequence Encrypted Bits GP
TB 41 36 TB 68.25
8 3
577 m sec
20 ms 0.577 ms
Information Information
Block Bursts
ISSUE 5 REVISION 4
EMOTOROLA LTD. 1999
EFR Speech FR Speech BCCH, PCH, AGCH, Data Traffic RACH + SCH
Frame 244 Frame 260 SDCCH, FACCH, SACCH, 9.6/4.8/2.4k P0 bits
bits bits CBCH 184 bits N0 bits
Cyclic Code + Class 1a Cyclic Firecode + Tail Add in Tail Cyclic Code +
Repetition Code + Tail In: 184 bits In: N0 bits Tail
In: 244 In: 260 Out: 228 bits Out: N1 bits In: P0 bits
Out: 260 Out: 267 Out: P1 bits
TCH/2.4
ReĆordering & Partitioning
+ Stealing Flag
In: 456 bits;
Out: 8 subblocks
Diagonal Interleaving
Speech Channel
Encoding
The BTS receives transcoded speech over the A-bis interface from the BSC. At this
point the speech is organized into its individual logical channels by the BTS. These
logical channels of information are then channel coded before being transmitted over the
air interface.
The transcoded speech information is received in frames, each containing 260 bits. The
speech bits are grouped into three classes of sensitivity to errors, depending on their
importance to the intelligibility of speech.
S Class 1a
Three parity bits are derived from the 50 class 1a bits. Transmission errors within
these bits are catastrophic to speech intelligibility, therefore, the speech decoder is
able to detect uncorrectable errors within the class 1a bits. If there are class 1a bit
errors, the whole block is usually ignored.
S Class 1b
The 132 class 1b bits are not parity checked, but are fed together with the class 1a
and parity bits to a convolutional encoder. Four tail bits are added which set the
registers in the receiver to a known state for decoding purposes.
S Class 2
The 78 least sensitive bits are not protected at all.
The resulting 456 bit block is then interleaved before being sent over the air interface.
Note:
Over the A-bis link, when using Full Rate Speech vocoding, 260 bits are transmitted in 20
ms equalling a transmission rate of 13 kbit/s. If Enhanced Full Rate is used then 244 bits
are transmitted over the A-bis link for each 20 ms sample. The EFR Frame is treated to
some preliminary coding to build it up to 260 bits before being applied to the same
channel coding as Full Rate.
The encoded speech now occupies 456 bits but is still transmitted in 20 ms thus raising
the transmission rate to 22.8 kbit/s.
260 bits
Class Class Class
1a 1b 2
50 bits 132 bits 78 bits
Tail
Parity
Bits
Check
50 3 132 4
Convolutional Code
378 78
456 bits
Overview
The transcoding for Enhanced Full Rate produces 20 ms speech frames of 244 bits for
channel coding on the air interface. After passing through a preliminary stage which
adds 16 bits to make the frame up to 260 bits the EFR speech frame is treated to the
same channel coding as Full Rate.
The additional 16 bits correspond to an 8 bit CRC which is generated from the 50 class
1a bits plus the 15 most important class 1b bits and 8 repetition bits corresponding to 4
selected bits in the original EFR frame of 244 bits.
Preliminary
Channel Coding
for EFR
EFR Speech Frame
50 Class 1a + 124 Class 1b + 70 Class 2 = 244 bits
Preliminary Coding
8 bit CRC generated from 50 Class 1a + 15 Class 1b added to Class 1b bits
8 repetition bits added to Class 2 bits
Output from Preliminary Coding
50 Class 1a + 132 Class 1b + 78 Class 2 = 260 bits
EFR frame of 260 bits passed on for similar channel coding as Full Rate.
Control Channel
Encoding
The diagram opposite shows the principle of the error protection for the control channels.
This scheme is used for all the logical signalling channels, the synchronization channel
(SCH) and the random access burst (RACH). The diagram applies to SCH and RACH,
but with different numbers.
When control information is received by the BTS it is received as a block of 184 bits.
These bits are first protected with a cyclic block code of a class known as a Fire Code,.
This is particularly suitable for the detection and correction of burst errors, as it uses 40
parity bits. Before the convolutional encoding, four tail bits are added which set the
registers in the receiver to a known state for decoding purposes.
The output from the encoding process for each block of 184 bits of signalling data is 456
bits, exactly the same as for speech. The resulting 456 bit block is then interleaved
before being sent over the air interface.
184 bits
Parity
184 Bits
184 40 4
Convolutional Code
456
456 bits
Data Channel
Encoding
The diagram opposite shows the principle of the error protection for the 9.6 kbit/s data
channel. The other data channels at rates of 4.8 kbit/s and 2.4 kbit/s are encoded
slightly differently, but the principle is the same.
Data channels are encoded using a convolutional code only. With the 9.6 kbit/s data
some coded bits need to be removed (punctuated) before interleaving, so that like the
speech and control channels they contain 456 bits every 20 ms.
The data traffic channels require a higher net rate (‘net rate’ means the bit rate before
coding bits have been added) than their actual transmission rate. For example, the 9.6
kbit/s service will require 12 kbit/s, because status signals (such as the RS-232 DTR
(Data Terminal Ready) have to be transmitted as well.
The output from the encoding process for each block of 240 bits of data traffic is 456 bits,
exactly the same as for speech and control. The resulting 456 bit block is then
interleaved before being sent over the air interface.
Note:
Over the PCM link 240 bits were transmitted in 20 ms equalling a transmission rate of 12
kbit/s. 9.6 kbit/s raw data and 2.4 kbit/s signalling information.
The encoded control information now occupies 456 bits but is still transmitted in 20 ms
thus raising the transmission rate to 22.8 kbit/s.
240 bits
240
Tail
Bits
240 244 4
Convolutional Code
488
Punctuate
456
456 bits
Interleaving
Having encoded, or error protected the logical channel, the next step is to build its
bitstream into bursts that can then be transmitted within the TDMA frame structure. It is
at this stage that the process of interleaving is carried out. Interleaving spreads the
content of one traffic block across several TDMA timeslots. The following interleaving
depths are used:
S Speech – 8 blocks
S Control – 4 blocks
S Data – 22 blocks
This process is an important one, for it safeguards the data in the harsh air interface
radio environment.
Because of interference, noise, or physical interruption of the radio path, bursts may be
destroyed or corrupted as they travel between MS and BTS, a figure of 10–20% is quite
normal. The purpose of interleaving is to ensure that only some of the data from each
traffic block is contained within each burst. By this means, when a burst is not correctly
received, the loss does not affect overall transmission quality because the error
correction techniques are able to interpolate for the missing data. If the system worked
by simply having one traffic block per burst, then it would be unable to do this and
transmission quality would suffer.
It is interleaving that is largely responsible for the robustness of the GSM air interface,
enabling it to withstand significant noise and interference and maintain the quality of
service presented to the subscriber.
Interleaving
#
# !"!
% $
"
"
"
Diagonal
Interleaving –
Speech
The diagram opposite illustrates, in a simplified form, the principle of the interleaving
process applied to a full-rate speech channel.
The diagram shows a sequence of ‘speech blocks’ after the encoding process previously
described, all from the same subscriber conversation. Each block contains 456 bits,
these blocks are then divided into eight blocks each containing 57 bits. Each block will
only contain bits from even bit positions or bits from odd bit positions.
The GSM burst will now be produced using these blocks of speech bits.
The first four blocks will be placed in the even bit positions of the first four bursts. The
last four blocks will be placed in the odd bit positions of the next four bursts.
As each burst contains 114 traffic carrying bits, it is in fact shared by two speech blocks.
Each block will share four bursts with the block preceding it, and four with the block that
succeeds it, as shown. In the diagram block 5 shares the first four bursts with block 4
and the second four bursts with block 6.
Speech Blocks
1 2 3 4 5 6
456
bits
57 57 57 57 57 57 57 57
bits bits bits bits bits bits bits bits
even odd even odd even odd even odd
ÍÍ Í
Í ÍÍ
ÍÍ ÍÍ
ÍÍ ÍÍ
ÍÍ Í
Í Í
Í Í
Í
Í Í ÍÍ ÍÍ ÍÍ Í Í Í
Shared by blocks 4 & 5 Shared by blocks 5 & 6
block 5 even bits block 6 even bits
block 4 odd bits block 5 odd bits
Transmission –
Speech
Each burst will be transmitted in the designated timeslot of eight consecutive TDMA
frames, providing the interleaving depth of eight.
The diagram opposite shows how successive bursts from this particular subscriber
conversation are transmitted. The subscriber is allocated timeslot 4 of the TDMA frame;
it will share this frame with up to seven other subscribers.
It is important to remember that each timeslot on this carrier may be occupied by a
different channel combination: traffic, broadcast, dedicated or combined.
Note that FACCH, because it ‘steals’ speech bursts from a subscriber channel,
experiences the same kind of interleaving as the speech data that it replaces
(interleaving depth = 8). The FACCH will steal a 456 bit block and be interleaved with the
speech. Each burst containing a FACCH block of information will have the appropriate
stealing flag set.
Full rate encoded speech blocks from 1 conversation arrive from the speech codec.
Speech Blocks
1 2 3 4 5 6
456
bits
4 5 6
ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ
ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ
ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ
Bursts
TDMA frames
Rectangular
Interleaving –
Control
The diagram opposite illustrates, in a simplified form, the principle of rectangular
interleaving. This is applied to most control channels.
The diagram shows a sequence of ‘control blocks’ after the encoding process previously
described. Each block contains 456 bits, these blocks are then divided into four blocks
each containing 114 bits. Each block will only contain bits for even or odd bit positions.
The GSM burst will be produced using these blocks of control.
Transmission –
Control
Each burst will be transmitted in the designated timeslot of four consecutive TDMA
frames, providing the interleaving depth of four.
The control information is not diagonally interleaved as are speech and data. This is
because only a limited amount of control information is sent every multiframe. If the
control information was diagonally interleaved, the receiver would not be capable of
decoding a control message until at least two multiframes were received. This would be
too long a delay.
ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ
ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ
ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ ÍÍ
FRAME 3
Diagonal
Interleaving –
Data
The diagram opposite illustrates, in a simplified form, diagonal interleaving applied to a
9.6 kbit/s data channel.
The diagram shows a sequence of ‘data blocks’ after the encoding process previously
described, all from the same subscriber. Each block contains 456 bits, these blocks are
divided into four blocks each containing 114 bits. These blocks are then interleaved
together.
The first 6 bits from the first block are placed in the first burst. The first 6 bits from the
second block will be placed in the second burst and so on. Each 114 bit block is spread
across 19 bursts and the total 456 block will be spread across 22 bursts.
Data channels are said to have an interleaving depth of 22, although this is sometimes
also referred to as an interleaving depth of 19.
Transmission –
Data
The data bits are spread over a large number of bursts to ensure that the data is
protected. Therefore, if a burst is lost, only a very small amount of data from one data
block will actually be lost. Due to the error protection mechanisms used, the lost data
can be reproduced at the receiver.
This wide interleaving depth, although providing a high resilience to error, does introduce
a time delay in the transmission of the data. If data transmission is slightly delayed, it will
not effect the reception quality, whereas with speech, if a delay were introduced this
could be detected by the subscriber. This is why speech uses a shorter interleaving
depth.
ÍÍ ÍÍÍÍ Í
ÍÍ
Í Í
ÍÍÍ Í
ÍÍÍ Í
ÍÍ
Í Í
ÍÍÍÍÍ
ÍÍÍÍÍÍ
ÍÍÍ
ÍÍÍ
ÍÍÍ
ÍÍÍ Í
ÍÍÍ
Chapter 7
Radio Interface Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Radio Interface Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–1
Transmission Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–2
Battery Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–4
Voice Activity Detection (VAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–6
Discontinuous Transmission (DTX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–6
Discontinuous Reception (DRX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–8
Multipath Fading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–10
Equalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–12
Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–14
Frequency Hopping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–16
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7–16
Section
Objectives
On completion of this section the student will be able to:
S Know the methods used to combat the following problems using GSM.
– Transmission Timing
– Multipath Fading
– Battery Life
Transmission Timing
To simplify the design of the MS, the GSM specifications specify an offset of three
timeslots between the BSS and MS timing, thus avoiding the necessity for the MS to
transmit and receive simultaneously. The diagram opposite illustrates this.
The synchronization of a TDMA system is critical because bursts have to be transmitted
and received within the “real time” timeslots allotted to them. The further the MS is from
the base station then, obviously, the longer it will take for the bursts to travel the distance
between them. The GSM BTS caters for this problem by instructing the MS to advance
its timing ((that is, transmit earlier) to compensate for the increased propagation delay.
This advance is then superimposed upon the three timeslot nominal offset.
The timing advance information is sent to the MS twice every second using the SACCH.
The maximum timing advance is approximately 233 ms. This caters for a maximum cell
radius of approximately 35 km.
Timing Advance
FRAME 1
Downlink
6 7
3 4 5 BS - MS
1 2
0
3 TS offset
TIMING
ADVANCE FRAME 1
6 7
4 5
2 3
Uplink 0 1
MS - BS
Battery Life
Introduction
One of the main factors which restrict reducing the size of a MS is the battery.
A battery must be large enough to maintain a telephone call for an acceptable amount of
time without needing to be recharged. Since there is demand for MSs to become smaller
and lighter the battery must also become smaller and lighter.
Four features which enable the life of a GSM MS battery to be extended.
S Power Control
S Voice Activity Detection (VAD)
S Discontinuous Transmission (DTX)
S Discontinuous Reception (DRX)
Power Control
This is a feature of the GSM air interface which allows the network provider to not only
compensate for the distance from MS to BTS as regards timing, but can also cause the
BTS and MS to adjust their power output to take account of that distance also. The
closer the MS is to the BTS, the less the power it and the BTS will be required to
transmit. This feature saves radio battery power at the MS, and helps to reduce
co-channel and adjacent channel interference.
Both uplink and downlink power settings can be controlled independently and individually
at the discretion of the network provider.
Initial power setting for the MS is set by the information provided on the Broadcast
Control Channel (BCCH) for a particular cell.
The BSS controls the transmit power of both the MS and the BTS. The received MS
power is monitored by the BSS and the receive BTS power is monitored by the MS and
then reported to the BSS. Using these measurements the power of both MS and BTS
can be adjusted accordingly
Power Control
The BTS will adjust the Tx power of each MS to ensure that the Rx
signal at the BTS is maintained within the defined power window.
Overview
VAD is a mechanism whereby the source transmitter equipment identifies the presence
or absence of speech.
VAD implementation is effected in speech mode by encoding the speech pattern
silences at a rate of 500 bit/s rather than the full 13 kbit/s. This results in a data
transmission rate for background noise, known as “comfort” noise, which is regenerated
in the receiver.
Without “comfort” noise the total silence between the speech would be considered to be
disturbing by the listener.
Discontinuous
Transmission
(DTX)
DTX increases the efficiency of the system through a decrease in the possible radio
transmission interference level. It does this by ensuring that the MS does not transmit
unnecessary message data. DTX can be implemented, as necessary, on a call by call
basis. The effects will be most noticeable in communications between two MS.
DTX in its most extreme form, when implemented at the MS can also result in
considerable power saving. If the MS does not transmit during ‘silences’ there is a
reduction in the overall power output requirement.
The implementation of DTX is very much at the discretion of the network provider and
there are different specifications applied for different types of channel usage.
DTX is implemented over a SACCH multiframe (480 ms). During this time, of the
possible 104 frames, only the 4 SACCH frames and 8 Silence Discriptor (SID) frames are
transmitted.
WITHOUT
DTX
WITH
VAD + DTX
SID
52 59
ÍÍÍ
S S
ÍÍÍ S S
ÍÍÍ
A A A A SACCH
C C C C MULTIFRAME
ÍÍÍ
C C C C (480 ms)
H H H H
0 103
4 x SACCH
8 x Silence Descriptor (SID)
DRX
8
ÈÈÈÈÈÈ
I
C
C= PCH/AGCH (CCCH)
7 C
S
F
6 C
5 C
S
F
4 C
3 C
S
F
2 C
0 C
S
F
C8 C17 C26 C8
C7 C16 C25 C7
MS paged only during
C6 C15 C24 C6
paging C1.
C5 C14 C23 C5 Once every 3 MF
C4 C13 C22 C4 (705 ms)
C3 C12 C21 C3
C2 C11 C20 C2
C1 C10 C19 C1
C0 C9 C18 C0
Multipath Fading
Multipath Fading results from a signal travelling from a transmitter to a receiver by a
number of routes. This is caused by the signal being reflected from objects, or being
influenced by atmospheric effects as it passes, for example, through layers of air of
varying temperatures and humidity.
Received signals will therefore arrive at different times and not be in phase with each
other, they will have experienced time dispersion. On arrival at the receiver, the signals
combine either constructively or destructively, the overall effect being to add together or
to cancel each other out. If the latter applies, there may be hardly any usable signal at
all. The frequency band used for GSM transmission means that a ‘‘good” location may
be only 15 cm from a ‘‘bad” location!
When the receive antenna is moving, the exact phase of each path changes and
consequently the combined signal-strength is also continually changing. When the
antenna is moving rapidly, this loss is recovered by interleaving and channel coding.
When it is slow moving or stationary however, the receiver may be in a “null” (point of
minimum signal) for several consecutive frames.
The diagram opposite shows a few routes by which a pulse of radio energy might be
propagated from a base station to a mobile.
Each has suffered varying losses in transmission (path attenuation), hence the variety of
amplitudes. A typical urban profile would cause dispersion of up to 5 microseconds,
whereas, a hilly terrain would cause dispersion of up to 20 microseconds.
GSM offers five techniques which combat multipath fading effects:
S Equalization.
S Diversity.
S Frequency hopping.
S Interleaving.
S Channel coding.
Multipath Fading
Equalization
Due to the signal dispersion caused by multipath signals the receiver cannot be sure
exactly when a burst will arrive and how distorted it will be. To help the receiver identify
and synchronize to the burst, a Training Sequence is sent at the centre of the burst. This
is a set sequence of bits which is known by both the transmitter and receiver.
When a burst of information is received, the equalizer searches for the training
sequence code. When it has been found, the equaliser measures and then mimics the
distortion which the signal has been subjected to. The equalizer then compares the
received data with the distorted possible transmitted sequences and chooses the most
likely one.
There are eight different Training Sequence codes numbered 0–7. Nearby cells
operating with the same RF carrier frequency will use different Training Sequence Codes
to enable the receiver the discern the correct signal.
FRAME 1 FRAME 2
GUARD
PERIOD NORMAL BURST GUARD
PERIOD
STEALING FLAGS
TAIL BITS TAIL BITS
Diversity
Signals arrive at the receive antenna from multiple paths. The signals are therefore
received by the antenna at different phases, some at a peak and some at a trough. This
means that some signals will add together to form a strong signal, while others will
subtract causing a weak signal.
When diversity is implemented, two antennas are situated at the receiver. These
antennas are placed several wavelengths apart to ensure minimum correlation between
the two receive paths. The two signals are then combined and the signal strength
improved.
Signal Strength
time
Signal Strength
time
Signal Strength
time
Diversity
Frequency Hopping
Introduction
Frequency hopping allows the RF channel used for carrying signalling channel timeslots
or traffic channel (TCH) timeslots to change frequency every frame (or 4.615 msec).
This capability provides a high degree of immunity to interference, due to the effect of
interference averaging, as well as providing protection against signal fading.
The effective “radio channel interference averaging” assumes that radio channel
interference does not exist on every allocated channel and the RF channel carrying TCH
timeslots changes to a new allocated RF channel every frame. Therefore, the overall
received data communication experiences interference only part of the time.
All mobile subscribers are capable of frequency hopping under the control of the BSS.
To implement this feature, the BSS software must include the frequency hopping option.
Cyclic or pseudo random frequency hopping patterns are possible, by network provider
selection.
0 1 2 3 4 5 6 7 0 1 2 3 45 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2
MS Tx
0 1 2 3 4 5 6 7 0 1 2 3 45 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2
Frequency Hopping
Cyclic frequency hopping using ARFCN's 10, 20, 30 and 40
7–17
Frequency Hopping ISSUE 5 REVISION 4
Introduction to Microcellular
Chapter 8
Introduction to Microcellular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Introduction to Microcellular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–1
Section Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–2
What is Microcell? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–2
Why Deploy Microcells? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–2
How are Microcells Deployed? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–4
Building Penetration from Externally Mounted Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–6
Antenna Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–8
Directional Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–8
Omni Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–8
The Microcellular Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–10
Picocells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8–12
Introduction to Microcellular
Section
Objectives
On completion of this section the student will be able to:
S understand what a microcell is and how they may be employed.
S understand the advantages of microcellular over other capacity enhancement
techniques.
Introduction
What is
Microcell?
The term microcell suggests a small cell. This is true, but microcells are defined as cells
for which the antennas are mounted below local rooftop level. This helps contain the
microcells RF radiation to within the street canyons.
Why Deploy
Microcells?
At present 80 to 90% of the current worldwide GSM subscribers fall into one category,
that of slow moving and stationary handportable units (class 4 mobiles).
Microcellular Concept
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
ÓÓÓÓÓÓÓÓÓ
!
(for example, Motorola microcells
under another vendors
macrocells)
or
S Erlangs
S Km2
S MHz
Note:
One Erlang is a measure of one traffic channel permanently utilized.
Layered Architecture
ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ
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Antenna Types
Both directional and omni-directional antennas have their uses in a microcellular system.
The different attributes of these antennas can be used by the cell planners to avoid
shadows, reduce handover requests, and maximize call success.
Directional
Antennas
Directional antennas are useful for covering long streets and have the following
advantages:
S Extra gain in the forward direction.
S Suppressed signal in the reverse direction, this is a useful characteristic if the cell
is a potential interferer with another cell located behind it.
It is also worth noting that a directional antenna could be used to improve in-building
coverage, in specific buildings, within the microcell area.
Omni Antennas
Omni antennas are useful for covering open areas (for example squares, plazas). In
these areas, it is desirable to have a clearly designated ‘best server’ cell to avoid
excessive handovers and their attendant problems.
Another application is to create a “corner crossroads” cell. This avoids having transient
cells at street crossroads. However, by intersecting with more streets, the potential for
interference with other cells may be increased.
Antenna Types
Directional Antennas
Buildings
Antenna
Coverage
ÈÈÈÈÈÈ
ÈÈÈÈÈÈ
ÈÈÈÈÈÈ
ÈÈÈÈÈÈ
Buildings
Antenna
Coverage
S
S
S
S
S
Picocells
The future capacity and coverage requirements of a network may require the introduction
of indoor cellular coverage. This may be provided by picocells. Picocells could offer
further capacity, coverage and quality enhancement to a network which has already
deployed microcells to provide on street coverage and capacity.
Picocells
CP02 Exercise
Exercise
Please answer all questions on the answer sheet provided.
2. There are five criteria used by GSM to perform handovers, RF level, MS distance
and power budget are three, but what are the other two?
3. What feature will GSM use to double the number of traffic channels for the same
bandwidth?
A. Discontinuous transmission
B. Half rate speech
C. Higher data rates
D. Phase two phones
A. The BSC connects DATA circuits to CONTROL BITS on the air interface.
B. The BSC connects TERRESTRIAL circuits to FRAMES on the air interface.
C. The BSC connects TERRESTRIAL circuits to CHANNELS on the air interface.
D. The BSC connects RADIO circuits to CHANNELS on the air interface.
6. The XCDR converts _____ kbps voice circuits to GSM defined _____ kbps
channels. (Fill in the blanks).
A. The XCDR converts 64 kbps voice circuits to GSM defined 16 kbps channels
B. The XCDR converts 120 kbps voice circuits to GSM defined 16 kbps channels
C. The XCDR converts 9600 kbps voice circuits to GSM defined 2400 kbps channels
D. The XCDR converts 64 kbps voice circuits to GSM defined 120 kbps channels
A. MSC and MS
B. BSC and BTS
C. OMC and BSC
D. BTS and MSC
8. The Message Transfer Link (MTL) carries signalling information between the MSC
and BSC. Which signalling protocol does the MTL use?
A. X.25
B. LAPB
C. C7
D. LAPD
A. Frequency correction
B. Normal
C. Dummy
D. Access
10. Which type of coding provides error protection and increases the number of bits to
be transmitted by a factor of 1:2?
11. Interleaving spreads the contents of a coded speech or data block over a number
of air interface bursts to provide error protection. What type of interleaving is used
for speech blocks?
A. Diagonal
B. Rectangular
C. Both
D. Cyclic
12. What is the maximum timing advance that can be ordered at the mobile station?
A. 4.615 mS
B. 233uS
C. 3 timeslots
D. 577uS
13. Which one of the following is NOT a technique to combat the effects of multi-path
fading?
A. Frequency hopping
B. Equalisation
C. Diversity
D. Sectorisation
14. The duration of a timeslot on the Air Interface is 577uS. What is the duration of a
burst?
A. 20mS
B. 577uS
C. 546uS
D. 4.615mS
15. Which of the following channels carries measurement information from a mobile
during a call?
A. SACCH
B. SDCCH
C. BCCH
D. TCH
16. Which logical channel is used by the mobile station for its first access to the
cellular system?
A. FACCH
B. RACH
C. SACCH
D. AGCH
17. Which timeslots in the TDMA frame can be used to carry DCCH channels?
A. Any
B. Zero
C. 1–7
D. 0, 2, 4, and 6
A. FACCH
B. RACH
C. SACCH
D. AGCH
A. Erlang
B. Picocell
C. Nanocell
D. Macrocell
Notes Page
Please write clearly and answer all questions on this answer sheet.
Name: _________________________
Date: _________________________
Company: _________________________
Country: _________________________
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Percentage:
GSM History
Frequency Band
Reserved for
Cellular (1979)
Due to the increasing use of radio communications throughout Europe, the frequency
spectrum was becoming congested and cluttered. Some bandwidth needed to be set
aside if a Europe wide cellular system was ever to become a reality. At the World
Administrative Radio Conference (WARC) of 1979, the frequency band to be used was
agreed upon. Since then, many analogue systems have come into service in Europe
(Sweden–1981, UK–1985 etc).
“Groupe Special
Mobile” Created
Within CEPT
(1982)
In 1982, the Conference of European Posts and Telecommunications Administrations
(CEPT) established a committee called “Groupe Speciale Mobile” (GSM) . This committee
was set up to specify a unique radio communication system for Europe, this system was
to be called GSM. Four working parties were set up to specify the different parts of the
GSM system.
“Permanent
Nucleus”
Established
(1986)
The GSM committee met regularly and eventually it was decided that a permanent body
was required. In 1986 a small team of full time members was established in Paris. This
team were to co-ordinate the working parties and manage the edition and updating of the
specifications. (There are now 130 recommendations divided into 12 series)
Phase 1 GSM
Recommendation
s Frozen (1990)
The first phase of the Recommendations for GSM were frozen in 1990 to enable
development of the first GSM systems.
GSM History
GSM Changes to
SMG (1991/1992)
In January 1991 phase 1 issue of DCS 1800 was approved by ETSI–GSM
At the end of 1991 the GSM committee was given responsibility for the next generation
of mobile communications equipment. To avoid confusion between the GSM system and
the GSM committee with its wider responsibilities, the committee was renamed ‘Special
Mobile Group‘ (SMG) in 1992. The SMG committees are now responsible for GSM,
Digital Communication System (DCS)1800 and the Universal Mobile Telecommunication
System (UMTS).
Also during this year, the GSM System was renamed. Rather than being called “Groupe
Special Mobile” it was now named “Global System for Mobile Communications”. The
name was changed to make the product attractive to a world-wide market rather than a
Europe-wide market, as was the initial intention. The acronym GSM was retained to
avoid confusion.
GSM is launched
(1992)
Commercial service for some major cities started in 1992, these are now firmly
established. The aim is to have GSM networks available along ‘‘corridors” linking major
cities. The introduction of GSM has occurred at different rates throughout the various
participating countries.
Phase 2 GSM
Technical
Specifications
Frozen (1993)
Several major changes have been made to the GSM technical specifications since phase
1 was frozen in 1990. These changes include rewriting a number of specifications to
remove ambiguities and faults. Many specifications have also been extended to detail
new services and features.
The GSM Recommendations have now passed through the appropriate ETSI procedures
and may now be referred to as “ETSI Technical Specifications”. These procedures
involve public enquiries and voting and the process takes several months.
GSM Coverage
GSM is widely used throughout the world, both GSM900/DCS1800.
GSM History
Overview
The SMG committee specifies all aspects of GSM. There are seven main sub-
committees which meet several times per year to discuss and update the technical
specifications that relate to their areas of concern. Each committee is responsible for a
number of specifications.
The permanent nucleus is responsible for the co-ordination and release of the
specifications. This group is now referred to as ETSI Project Team #12 (PT12).
The Technical
Specifications
The scope of the technical specifications, and the committees that are responsible for
them, are shown in the tables opposite.
GSM Committees
SMG5 UMTS –
The GSM
Memorandum of
Understanding
(MoU)
The technical specifications make up only part of the definition for GSM. Since so many
countries are working together on this one system, commercial and operational aspects
must also be taken into account.
A Memorandum of Understanding was put together which covered a number of items not
covered by the technical specifications, these are listed below:
Timescales.
S Procurement.
S Routing plans.
S System deployment.
S Tariff principles.
S Concerted service introduction.
S Roaming agreements.
This memorandum was first signed in 1987 by operators and regulatory bodies in the
participating countries. The MoU was updated in 1991.
Australia was the first non-European country to sign the the MoU many others have also
signed since then.
01 General
02 Service aspects
03 Network aspects
06 Audio aspects
09 Network interworking
10 Service interworking
GSM Coverage
GSM has been widely accepted throughout the world.
International roaming is available between many of the networks, and more agreements
are added constantly as new networks go live.
A list of GSM networks is given opposite.
GSM Coverage
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The subscriber pressing the send" key initiates a C hannel Request" message from
the MS to the BSS. This is followed by the assignment of a dedicated control channel
by the BSS and the establishment of the signalling link between the MS and BSS
``SABM" - Set Asynchronous Balanced Mode
The message Request for Service" is passed to the MSC which relays it to the VLR.
The VLR will carry out the authentication process if the MS has been previously
registered on this VLR - if not, the VLR will have to obtain authentication parameters
from HLR. The diagram assumes the MS was previously registered on this VLR.
Subscriber authentication (optional) takes place using authentication messages and
encryption algorithms and, if successful the C all setup can continue. If ciphering is to
be used this is initiated at this time as the setup message contains sensitive
information.
The message ``SetĆUp" is sent by the MS to the MSC accompanied by the call
information (type of call, and number being called etc.). The message is forwarded
from the MSC to the VLR.
The MSC may initiate the MS IMEI check (is the MS stolen? etc). Note that this check
may occur later in the message sequence.
In response to the message `SetĆUp" (sent at step 4), the VLR sends the message
``C omplete C all" to the MSC , which notifies the MS with ``C all Proceeding".
The MSC then assigns a traffic channel to the BSS ``Assignment C ommand", which
in turn assigns an air interface traffic channel. The MS responds to the BSS (which
responds in turn to the MSC ) with ``Assignment C omplete
An ``Initial and Final Address Message (IFAM)" is sent to the PSTN. Ring tone is applied
at the MS in response to ``Alerting" which the MSC sends to the MS when the PSTN
responds with an ``Address C omplete Message (AC M)"
When answered (``Answer (ANS)" from the PSTN), the message `C onnect" is
forwarded to the MS by the MSC , stopping the MS ring tone. The MSC then connects
the GSM traffic channel to the PSTN circuit, thus completing the end to end traffic
connection.
<RAC H>
C HANNEL REQUEST
<AGC H>
DC C H ASSIGN
(C all info)
EQUIPMENT ID REQUEST
C OMPLETE C ALL
<SDC C H>
C ALL PROC EEDING
<SDC C H>
ASSIGNMENT C OMMAND
(channel)
(circuit)
<FAC C H>
ASSIGNMENT C OMPLETE
(TC H)
INITIAL AND FINAL
ADDRESS (IFAM)
ALERTING MS HEARS
RINGTONE <FAC C H>
FROM LAND
PHONE
ANSWER (ANS)
<FAC C H>
C ONNEC T RING
TONE
STOPS
BILLING STARTS
C ONNEC T AC KNOWLEDGE <FAC C H>
<TC H>
INITIAL AND FINAL ADDRESS
(IFAM) (MSISDN)
<SDC C H>
(TMSI) (TMSI (Status)
& Status)
<TMSI>
C OMPLETE C ALL
<SDC C H>
SETUP
<SDC C H>
C ALL C ONFIRMATION
RING TONE
ADDRESS C OMPLETE (AC M) AT LAND
<SDC C H>
PHONE
ASSIGNMENT C OMMAND
(channel)
<FAC C H>
(circuit)
ASSIGNMENT C OMPLETE
RINGING
STOPS
<FAC C H> AT LAND
SUBSC RIBER
PHONE
C ONNEC T PIC KS UP
<FAC C H> BILLING
C ONNEC T AC K ANSWER (ANS) STARTS
<TC H>
The MS initiates the clearing of the call by sending the Disconnect" message
to the MSC . The MSC will then send a Release" message to the PSTN which
will then start to release the fixed network circuits associated with the call . The
MSC will also send a Release" message to the MS to indicate that it may clear
down the call.
When the MS receives the message, it will release the call and respond with the
Release C omplete" message. The PSTN will also respond with a Release
C omplete" message.
The MSC now initiates the freeing up of the air interface radio resources and the
A interface terrestrial resources related to the call. The MSC will send the C lear
C ommand" to the BSS. The BSS in turn will send a C hannel Release" on to
the MS this will start the release of the radio resources used for that call. The
BSS will then respond to the MSC with the C lear C omplete" message
indicating that is has released the radio and terrestrial resources.
The BSS will complete the release of the radio resources by sending the DISC "
message to the MS. The MS will respond with an Unnumbered
Acknowledgement (UA)" message.
The MSC will now initiate the release of the signalling connection related to the
call. The MSC will send the Released" message to the BSS, which will respond
with the Release C omplete" message.
The call is now cleared and all resources are available for another subscriber.
<FAC C H>
DISC ONNEC T
PSTN RELEASE
<FAC C H>
MOBILE RELEASE
PSTN RELEASE
C OMPLETE
MS RELEASE <FAC C H>
C OMPLETE
MS ↔ MSC SIGNALLING
RELEASED
C LEAR C OMMAND
<FAC C H>
C HANNEL RELEASE
C LEAR C OMPLETE
RELEASED
RELEASE C OMPLETE
Acronyms:
TMSI Temporary Mobile Subscriber Identity
MSRN Mobile Station Roaming Number
IMSI International Mobile Subscriber Identity
MSISDN Mobile Station ISDN Number
LAI Location Area Identity
SACCH Slow Associated Control Channel
FACCH Fast Associated Control Channel
PERIODIC
MEASUREMENT
REPORTS
<SAC C H>
HANDOVER REQUIRED
HANDOVER REQUEST
New BSS assigns
air interface traffic
HANDOVER REQ AC K (TMSI
channel
cct. code)
INFORMATION
INTERC HANGE
(HO Ref. No.)
<FAC C H>
HANDOVER C OMPLETE
C LEAR C OMMAND
PERIODIC
MEASUREMENT
REPORTS
<SAC C H>
A location update is initiated by the MS when it detects that it has entered a new
location area. The location area is transmitted on the BC C H as the LAI. The
MS will be assigned an SDC C H by the BSS, the location updating procedure
will be carried out using this channel.
Once the SDC C H has been assigned, the MS transmits a Location Update
Request" message. This message is received by the MSC which then sends
the new LAI and the current MS TMSI number to the VLR. The information will
also be sent to the HLR if the MS has not previously been updated on the
network.
Authentication and ciphering may now take place if required.
The VLR will now assign a new TMSI for the MS, this number will be sent to the
MSC using the Forward New TMSI" message. The VLR will now initiate the
Location Update Accept" message which will transmit the new TMSI and LAI
to the MS.
Once the MS has stored both the TMSI and the LAI on its SIM card it will send
the TMSI Relocate C omplete" message to the MSC . The MSC will then send
the TMSI AC K" message to the VLR to confirm that the location update has
been completed.
The SDC C H will then be released by the MS.
<RAC H>
C HANNEL REQUEST
<AGC H>
DC C H ASSIGN
AUTHENTIC ATION
C IPHERING
<SDC C H>
LOC ATION UPDATE
AC C EPT (TMSI)
<SDC C H>
TMSI RELOC ATE
C OMPLETE
TMSI AC K
<SDC C H>
C LEAR C OMMAND
<SDC C H>
C LEAR C OMPLETE
If the authentication fails, the HLR will be notified and an Authentication Reject"
message will be send to the MS.
PREĆSEND
TRIPPLES TO VLR
<SDC C H>
AUTHENTIC ATION
RESPONSE (SRES)
START C IPHERING
C IPHER MODE
C OMMAND
<SDC C H>
<SDC C H>
C IPHER MODE
C OMPLETE
Equipment
Identification
Equipment Identification
<SDC C H>
EQUIPMENT ID REQUEST
C HEC K IMEI
Note:
IMEI check may be deferred until after traffic channel has been established!
abbreviations
Numbers
# Number.
2 Mbit/s link As used in this manual set, the term applies to the European
4-wire 2.048 Mbit/s digital line or link which can carry 30
A-law PCM channels or 120 16 kbit/s GSM channels.
4GL 4th Generation Language.
A
A interface Interface between MSC and BSS.
A3 Authentication algorithm that produces SRES, using RAND
and Ki.
A38 A single algorithm performing the function of A3 and A8.
A5 Stream cipher algorithm, residing on an MS, that produces
ciphertext out of plaintext, using Kc.
A8 Ciphering key generating algorithm that produces Kc using
RAND and Ki.
AB Access Burst.
Abis interface Interface between a remote BSC and BTS. Motorola offers a
GSM standard and a unique Motorola A-bis interface. The
Motorola interface reduces the amount of message traffic and
thus the number of 2 Mbit/s lines required between BSC and
BTS.
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 BTS
equipment.
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.
B
B Interface Interface between MSC and VLR.
BA BCCH Allocation. The radio frequency channels allocated in a
cell 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 to
broadcast general information about a BTS site on a per cell
or sector basis.
BCD Binary Coded Decimal.
BCF Base station Control Function. The GSM term for the digital
control circuitry which controls the BTS. In Motorola cell sites
this is a normally a BCU which includes DRI modules and is
located in the BTS cabinet.
BCIE Bearer Capability Information Element.
BCU Base station Control Unit. A functional entity of the BSS
which provides the base control function at a BTS site. The
term 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 GSM
system.
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 12
balanced (6-pair) 120 ohm (37-pin D-type connector) lines for
2 Mbit/s circuits (See also T43).
BIC–Roam Barring of All Incoming Calls when Roaming outside the
Home 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, databases
and 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 a
particular bit period within a timeslot.
BPF Bandpass Filter.
BPSM mBCU Power Supply Module.
BS Basic Service (group).
BS Bearer Service. A type of telecommunication service that
provides the capability for the transmission of signals
between user-network interfaces. The PLMN connection type
used to support a bearer service may be identical to that used
to support other types of telecommunication service.
BSC Base Station Controller. A network component in the GSM
PLMN which has the digital control function of controlling all
BTSs. The BSC can be located within a single BTS cabinet
(forming a BSS) but is more often located remotely and
controls 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 station
colour code. One Base Station can have several Base
Station 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 the
MSC through a single interface as defined by the GSM 08
series of recommendations, as being the entity responsible
for communicating with MSs in a certain area. The radio
equipment of a BSS may cover one or more cells. A BSS
may consist of one or more base stations. If an internal
interface is implemented according to the GSM 08.5x series
of recommendations, then the BSS consists of one BSC and
several BTSs.
BSSAP BSS Application Part (of Signalling System No. 7) (DTAP +
BSSMAP).
BSSC Base Station System Control cabinet. The cabinet which
houses one or two BSU shelves at a BSC or one or two RXU
shelves at a remote transcoder.
BSSMAP Base Station System Management Application Part (6-8).
BSSOMAP BSS Operation and Maintenance Application Part (of
Signalling System No. 7).
BSU Base Station Unit shelf. The shelf which houses the digital
control modules for the BTS (p/o BTS cabinet) or BSC (p/o
BSSC cabinet).
BT British Telecom.
BT Bus Terminator.
C
C Conditional.
C Interface Interface between MSC and HLR/AUC.
C7 ITU-TSS Signalling System 7 (sometimes referred to as S7 or
SS#7).
CA Cell Allocation. The radio frequency channels allocated to a
particular cell.
CA Central Authority.
CAB Cabinet.
CADM Country ADMinistration. The Motorola procedure used within
DataGen to create new country and network files in the
DataGen 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. There
are two types of CCB, CCB (Output) and CCB (Extension).
These, with up to two CCB Control cards, may comprise the
TATI. The second card may be used for redundancy.
CCBS Completion of Calls to Busy Subscriber supplementary
service.
1 C ell =
1 Sector
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 object
configuration 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 control
channels 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 in
Horizonmacro).
DCN Data Communications Network. A DCN connects Network
Elements with internal mediation functions or mediation
devices to the Operations Systems.
DC PSM DC Power Supply Module.
Dummy burst A period of carrier less than one timeslot whose modulation is
a defined sequence that carries no useful information. A
dummy burst fills a timeslot with an RF signal when no
information is to be delivered to a channel.
DYNET DYnamic NETwork. Used to specify BTSs sharing dynamic
resources.
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 voice
circuits.
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 spectral
density.
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).
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 control
channel which is associated with a TCH and carries control
information 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).
G
G Interface Interface between VLR and VLR.
Gateway MSC An MSC that provides an entry point into the GSM PLMN
from another network or service. A gateway MSC is also an
interrogating node for incoming PLMN calls.
GB, Gbyte Gigabyte.
GBIC Gigabit Interface Converter.
GCLK Generic Clock board. System clock source, one per site (p/o
BSS, BTS, BSC, IWF, RXCDR).
GCR Group Call Register.
GDP Generic DSP Processor board. Interchangeable with the XCDR
board.
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 a
user’s primary group.
GMB GSM Multiplexer Board (p/o BSC).
GMR GSM Manual Revision.
GMSC Gateway Mobile-services Switching Centre (see Gateway
MSC).
GMSK Gaussian Minimum Shift Keying. The modulation technique
used in GSM.
GND GrouND.
GOS Grade of Service.
GPA GSM PLMN Area.
GPC General Protocol Converter.
GPROC Generic Processor board. GSM generic processor board: a
68030 with 4 to 16 Mb RAM (p/o BSS, BTS, BSC, IWF,
RXCDR).
GPROC2 Generic Processor board. GSM generic processor board: a
68040 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 reached
by a fixed subscriber, without the subscriber’s knowledge of
the location of the MS. A GSA may include the areas served
by several GSM PLMNs.
GSA GSM System Area. The group of GSM PLMN areas
accessible by GSM MSs.
GSM Groupe Spécial Mobile (the committee).
GSM Global System for Mobile communications (the system).
H
H 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 from
one radio channel to another radio channel. Handover allows
established calls to continue by switching them to another
radio resource, as when an MS moves from one BTS area to
another. Handovers may take place between the following
GSM 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 information
defining the higher layer characteristics of a teleservice active
on the terminal.
HLR Home Location Register. The LR where the current location
and all subscriber parameters of an MS are permanently
stored.
HMS Heat Management System. The system that provides
environmental 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 double
the current GSM air interface capacity to 16 simultaneous
calls per carrier (see also FR – Full Rate).
HS HandSet.
I
I Information frames (RLP).
IA Incoming Access (closed user group (CUG) SS
(supplementary service)).
IA5 International Alphanumeric 5.
IADU Integrated Antenna Distribution Unit. (The IADU is the
equivalent 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 database
management 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. Electronic
serial number that uniquely identifies the MS as a piece or
assembly of equipment. The IMEI is sent by the MS along
with request for service.
IMM IMMediate assignment message.
K
k 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 the
operation of encipherment and decipherment.
kHz kilo-Hertz (103).
Ki Individual subscriber authentication Key (p/o authentication
process of AUC).
KIO A class of processor.
KSW Kiloport SWitch board. TDM timeslot interchanger to connect
calls (p/o BSS).
KSWX KSW Expander half size board. Fibre optic distribution of
TDM bus (p/o BSS).
kW kilo-Watt.
L
L1 Layer 1.
L2ML Layer 2 Management Link.
L2R Layer 2 Relay function. A function of an MS and IWF that
adapts a user’s known layer2 protocol LAPB onto RLP for
transmission 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 freely
without updating the location register. An LA may comprise
one or several base station areas.
LAC Location Area Code.
LAI Location Area Identity. The information indicating the location
area in which a cell is located.
LAN Local Area Network.
LANX LAN Extender half size board. Fibre optic distribution of LAN
to/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.
M
M Mandatory.
M Mega (106).
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-R
database. There is a CM MIB and an EM MIB.
MIC Mobile Interface Controller.
Microcell A cell in which the base station antenna is generally mounted
below rooftop level. Radio wave propagation is by diffraction
and scattering around buildings, the main propagation is
within street canyons.
min minute(s).
ms micro-second (10–6).
mBCU Micro Base Control Unit.
MIT Management Information Tree. Name of a file on the
Motorola 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 user
interfaces with the software to request a function or change
parameters.
MMI client A machine configured to use the OMC-R software from an
MMI server.
MMI processor MMI client/MMI server.
MMI server A computer which has its own local copy of the OMC-R
software. It can run the OMC-R software for MMI clients to
mount.
MML Man Machine Language. The tool of MMI.
MMS Multiple Serial Interface Link. (see also 2Mbit/s link)
MNC Mobile Network Code.
MNT MaiNTenance.
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).
N
N/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 the
column contains unique values (used only with indexed
columns).
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 of
network information for example hostnames, IP addresses
and 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 which
control, monitor and record the use and the performance of
resources of a telecommunications network in order to
provide telecommunication services to customers/users at a
certain level of quality.
NMASE Network Management Application Service Element.
NMC Network Management Centre. The NMC node of the GSM
TMN provides global and centralised GSM PLMN monitoring
and control, by being at the top of the TMN hierarchy and
linked to subordinate OMC nodes.
NMSI National Mobile Station Identification number.
NMT Nordic Mobile Telephone system.
O
O Optional.
OA Outgoing Access (CUG SS).
O&M Operations and Maintenance.
OASCU Off-Air-Call-Set-Up. The procedure in which a
telecommunication connection is being established whilst the
RF 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 modify
and carry out Radio Frequency planning on multiple BSS
binary files.
OLR Overall Loudness Rating.
OMAP Operations and Maintenance Application Part (of signalling
system No. 7) (was OAMP).
OMC Operations and Maintenance Centre. The OMC node of the
GSM TMN provides dynamic O&M monitoring and control of
the PLMN nodes operating in the geographical area
controlled by the specific OMC.
OMC-G Operations and Maintenance Centre — Gateway Part.
(Iridium)
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 infrastructure
attempts to reach an MS within its location area, before any
other 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 to
send paging messages to the MSs.
PCHN Paging Channel Network.
PCHN Physical Channel.
PCM Pulse Code Modulation (see also 2 Mbit/s link which is the
physical bearer of PCM).
PCN Personal Communications Network.
PCR Preventative Cyclic Retransmission. A form of error
correction suitable for use on links with long transmission
delays, 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 a
building.
PICS Protocol Implementation Conformance Statement.
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 alarm
interface (p/o BSS).
PIXT Protocol Implementation eXtra information for Testing.
PK Primary Key. A database column attribute, the primary key is
a not-null, non-duplicate index.
Plaintext Unciphered data.
PlaNET Frequency planning tool.
PLL Phase Lock Loop (refers to phase locking the GCLK in the
BTS).
PLMN Public Land Mobile Network. The mobile communications
network.
PM Performance Management. An OMC application.
PM-UI Performance Management User Interface.
Q
QA 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.
R
R Value of reduction of the MS transmitted RF power relative to
the maximum allowed output power of the highest power
class of MS (A).
RA RAndom mode request information field.
RAB Random Access Burst.
RACCH Random Access Control CHannel. A GSM common control
channel 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 Motorola
diagnostic 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 control
circuits, 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 unique
identifier, the distinguished name, for a particular network
element.
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 (see
full rate).
resync Resynchronize/resynchronization.
REQ REQuest.
S
S/W SoftWare.
SABM Set Asynchronous Balanced Mode. A message which
establishes the signalling link over the air interface.
SABME SABM Extended.
SACCH Slow Associated Control CHannel. A GSM control channel
used by the MS for reporting RSSI and signal quality
measurements.
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, SAPs
of a layer are defined as gates through which services are
offered 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).
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 supplement
to, a basic telecommunication service.
SS System Simulator.
SSA SCCP messages, Subsystem-allowed (see CCITT Q.712
para 1.15).
SSAP Site System Audits Processor.
SSC Supplementary Service Control string.
SSF Subservice Field. The level 3 field containing the network
indicator 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.712
para 1.18).
SSP SubSystem Prohibited message.
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 26
broadcast/common control multiframes (period 6.12s).
Super user User account that can access all files, regardless of
protection settings, and control all user accounts.
SURF Sectorized Universal Receiver Front-end (Used in
Horizonmacro).
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 modulation
bit stream carries information for the MS to synchronize its
frame to that of the received signal.
SYS SYStem.
SYSGEN SYStem GENeration. The Motorola procedure for loading a
configuration database into a BTS.
T
T Timer.
T Transparent.
T Type only.
T43 Type 43 Interconnect Board. Provides interface to 12
unbalanced (6-pair) 75 ohm (T43 coax connectors) lines for
2 Mbit/s circuits (See BIB).
TA Terminal Adaptor. A physical entity in the MS providing
terminal adaptation functions (see GSM 04.02).
TA Timing Advance.
TAC Type Approval Code.
TACS Total Access Communications System (European analogue
cellular system).
TAF Terminal Adaptation Function.
TATI Transmit Antenna Transceiver Interface. The TATI consists
of RF combining equipments, either Hybrid or Cavity
Combining. (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 Signalling
System No. 7).
TCB TATI Control Board.
TCH Traffic CHannel. GSM logical channels which carry either
encoded 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.
U
UA Unnumbered Acknowledgment. A message sent from the
MS to the BSS to acknowledge release of radio resources
when 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 the
user.
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 from
the full burst because of the bit shift of the I and Q parts of
the GMSK signal.
USSD Unstructured Supplementary Service Data.
UUS User-to-User Signalling supplementary service.
V
V Value only.
VA Viterbi Algorithm (used in channel equalizers).
VAD Voice Activity Detection. A process used to identify presence
or 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 which
provides a temporary register for subscriber information for a
visiting 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.
W
WAN Wide Area Network.
WPA Wrong Password Attempts (counter).
WS Work Station. The remote device via which O&M personnel
execute input and output transactions for network
management purposes.
WSF Work Station Function block.
WWW World Wide Web.
X
X.25 CCITT specification and protocols for public packet-switched
networks (see PSPDN).
X.25 link A communications link which conforms to X.25 specifications
and uses X.25 protocol (NE to OMC links).
XBL Transcoder to BSS Link. The carrier communications link
between the Transcoder (XCDR) and the BSS.
XCB Transceiver Control Board (p/o Transceiver).
XCDR Full-rate Transcoder. Provides speech transcoding and 4:1
submultiplexing (p/o BSS, BSC or XCDR).
XCDR board The circuit board required to perform speech transcoding at
the 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.
Z
ZC Zone Code