BSS Troubleshooting Manual.pdf

Chapter 1 General Procedures and Methods 1-1................................................1.1 Requirements for Maintenance Personnel 1-1.............................................

1.1.1 On Professional Knowledge and Skills 1-1..........................................1.1.2 On BSS System and Networking 1-1...................................................1.1.3 On BSS Equipment 1-1........................................................................1.1.4 On Instruments and Apparatus 1-2......................................................

1.2 General Procedures of Troubleshooting 1-2................................................1.2.1 Information Collection-Collecting Original Information asDetailedly as Possible 1-2.............................................................................1.2.2 Fault judgement-Judge the Scope and Type of the Fault 1-3..............1.2.3 Fault Location-Specifying the Concrete Cause of the Fault 1-4...........1.2.4 Fault Removing-Removing the Fault and Restore the Systemby Using Suitable Methods or Steps 1-4.......................................................

1.3 Basic Methods of Fault Judgement and Location 1-4..................................1.3.1 Analysis of Original Information 1-4.....................................................1.3.2 Alarm Information Analysis 1-5............................................................1.3.3 Indicator Status Analysis 1-5................................................................1.3.4 Calling Test Auxiliary Analysis 1-6.......................................................1.3.5 Apparatus & Meter Auxiliary Analysis 1-7............................................1.3.6 Traffic Statistics Auxiliary Analysis 1-8.................................................1.3.7 Interface Trace 1-9...............................................................................1.3.8 Test/Loop Back 1-12..............................................................................1.3.9 Comparison/Interchange 1-13................................................................1.3.10 Switching/Resetting 1-14.....................................................................1.3.11 Contacting the Technical Support Engineers of Huawei 1-15..............

Chapter 2 Troubleshooting for OMC 2-1..............................................................

2.1 GSM BSS-OMC Overview 2-1.....................................................................2.2 Troubleshooting for OMC and Examples 2-2...............................................

2.2.1 Communication Between BAM and Host Interrupted 2-2....................2.2.2 Communication between BAM and Server is Interrupted 2-3..............2.2.3 Data Table Error is Prompted during BAM Startup 2-3........................2.2.4 Loading Host Programs from BAM Failed 2-4.....................................2.2.5 Data cannot be Modified/Deleted 2-4...................................................2.2.6 At Least One Table in BSC Data Management System ReportHas Error 2-5.................................................................................................2.2.7 Communication Timeout of Interface Tracing through BSCMaintenance System 2-5..............................................................................2.2.8 Alarm System Cannot Receive Alarms 2-6..........................................2.2.9 BAM Prints "Fail to shake hands with alarm server" 2-7......................2.2.10 Records in Alarm Box and Those in Fault Alarm tableInconsistent 2-8.............................................................................................

2.2.11 Shaking Hand with BAM Fails When the Alarms are Deletedthrough Alarm System 2-9............................................................................2.2.12 Failed to Register due to Server Failure 2-9......................................2.2.13 Service Console Running Failed 2-10..................................................2.2.14 Loading Shell Map Failed 2-10............................................................2.2.15 Some Computers Cannot Refresh Templates in BSC TrafficStatistics System 2-11.....................................................................................

Chapter 3 Troubleshooting for Software Loading 3-1........................................3.1 Troubleshooting for BTS Software Loading 3-1...........................................

3.1.1 Introduction to Software Loading 3-1...................................................3.1.2 Description of Common Loading Troubles 3-3.....................................3.1.3 Trouble Handling 3-3............................................................................3.1.4 An Example of Loading BTS Software Failure on the RemoteWS 3-6..........................................................................................................

3.2 Troubleshooting for BSC Software Loading 3-7...........................................3.2.1 BSC Software Loading Channels 3-7..................................................3.2.2 AM/CM Loading Fails 3-7.....................................................................3.2.3 AM/CM Loading Timeout 3-10...............................................................3.2.4 BM Loading Failed and LOAD Indicator is Constantly ON 3-11............3.2.5 BM Loading Timeout 3-13......................................................................3.2.6 BM Loading Starts Again after Successful Loading 3-14.......................3.2.7 BM Does Not Work Normally or Reload Automatically 3-15..................3.2.8 Operating Parameters Not Updated after Data Loading 3-16................

Chapter 4 Troubleshooting for Links 4-1.............................................................4.1 Overview 4-1................................................................................................4.2 Fundamental Knowledge 4-1........................................................................

4.2.1 SS7 Concepts 4-1................................................................................4.2.2 SS7 Direction 4-2.................................................................................4.2.3 GMC2 4-2.............................................................................................4.2.4 Pb Interface 4-2....................................................................................4.2.5 Signaling Direction on LAPD Links 4-4................................................

4.3 Trouble Handling 4-4....................................................................................4.3.1 No SS7 Signaling Trace Message 4-4.................................................4.3.2 RSL Disabled 4-5.................................................................................4.3.3 OML Disabled 4-6................................................................................4.3.4 SS7 Link Faulty 4-7..............................................................................4.3.5 AM/CM-BM Link Faulty 4-13..................................................................4.3.6 Optical Path Faulty 4-13.........................................................................4.3.7 PbSL Disabled 4-14...............................................................................4.3.8 E1 Faulty 4-15........................................................................................

4.3.9 Microcells Optical Transmission Board Faulty 4-16..............................4.4 Examples 4-18................................................................................................

4.4.1 Examples of SS7 Link Trouble 4-18.......................................................4.4.2 Examples of RSL & OML Troubles 4-19................................................4.4.3 Examples of E1 Transmission Trouble 4-21..........................................4.4.4 Examples of Optical Transmission Board Trouble in Microcell 4-26......

Chapter 5 Troubleshooting for Clock 5-1............................................................5.1 Overview 5-1................................................................................................

5.1.1 Fault Description and Fault Causes in BSC Clock System 5-1............5.1.2 Fault Description and Fault Causes in BTS Clock System 5-2............

5.2 Fundamental Knowledge 5-4........................................................................5.2.1 Introduction to BSC 5-4........................................................................5.2.2 Fundamental Knowledge of BTS Clock System 5-13............................5.2.3 Specifications about BTS Clock System 5-18........................................

5.3 Trouble Handling 5-18....................................................................................5.3.1 Trouble Handling for BSC 5-18..............................................................5.3.2 Troubleshooting for BTS 5-20................................................................

5.4 Examples 5-23................................................................................................5.4.1 Troubleshooting Examples for BSC Clock Fault 5-23............................5.4.2 Troubleshooting Examples for BTS Clock Fault 5-25............................

Chapter 6 Troubleshooting for Handover 6-1.....................................................6.1 Overview 6-1................................................................................................

6.1.1 Failure Classification 6-1......................................................................6.1.2 Locating Tool 6-1.................................................................................

6.2 Trouble Handling 6-2....................................................................................6.2.1 Locating Procedure 6-2........................................................................6.2.2 Locating Procedure of No Handover Starting Up 6-3...........................6.2.3 Locating of Hardware Failure 6-4.........................................................6.2.4 Locating of Data Configuration Problem 6-4........................................

6.3 Examples 6-5................................................................................................6.3.1 MSC Handover Problem 6-5................................................................6.3.2 BSC Problems 6-10...............................................................................6.3.3 BTS-related Problem 6-16.....................................................................6.3.4 Others 6-21............................................................................................

Chapter 7 Troubleshooting for Congestion 7-1..................................................7.1 Overview 7-1................................................................................................7.2 A-Interface Congestion 7-1...........................................................................

7.2.1 Fundamental Knowledge 7-1...............................................................7.2.2 Troubleshooting Process 7-2...............................................................

7.3 Radio Channel Congestion 7-4....................................................................7.3.1 Fundamental Knowledge 7-4...............................................................7.3.2 Analysis 7-5..........................................................................................

7.4 Examples 7-7................................................................................................7.4.1 Example of SDCCH Congestion Resulted from Co-frequencyInterference 7-7.............................................................................................7.4.2 A Cells Congestion rate is Overhigh 7-8.............................................7.4.3 Severe SDCCH Congestion Resulted from UnstableTransmission 7-8...........................................................................................7.4.4 SDCCH Congestion Resulted from Lots of Burst LA Updating 7-9......7.4.5 High TCH Congestion Rate Resulted from Incorrect CICSetting 7-10.....................................................................................................7.4.6 High SDCCH Congestion Rate LAC Resulted from ImproperLAC Setting 7-11.............................................................................................

Chapter 8 Troubleshooting for Access 8-1.........................................................8.1 Overview 8-1................................................................................................

8.1.1 MS Searching Network 8-1..................................................................8.1.2 Location Updating Procedure 8-1........................................................8.1.3 Call Procedures 8-3.............................................................................

8.2 Trouble Handling 8-5....................................................................................8.2.1 MS Cannot Find a Network 8-5............................................................8.2.2 MS Cannot Access a Network 8-7.......................................................8.2.3 Location Updating Is too Frequent 8-9.................................................8.2.4 MS Drops from the Network Frequently 8-9.........................................8.2.5 MS Finds a Network but Cannot Call 8-10.............................................

8.3 Examples 8-11................................................................................................8.3.1 MS Has Difficulty in Accessing a Network-Signal Is too Weak 8-11......8.3.2 MS Cannot Perform Cell Reselection - Signals of AdjacentCells Are Weak 8-11.......................................................................................8.3.3 GSM MS Drops from the Network - Location Updating PeriodIs too Short 8-12..............................................................................................8.3.4 MS Drops from the Network - CGI is Erroneous 8-13............................8.3.5 MS Has Difficulty in Accessing a Network - MSC Cell Data Isnot Ready 8-14................................................................................................8.3.6 MS Drops from the Network - MSC Cell Data Is not Ready 8-15..........8.3.7 Some MSs Cannot Access a Network - System Information IsErroneous 8-16...............................................................................................8.3.8 MS Has Difficulty in Accessing a Network - CBQ and CBA AreErroneous 8-17...............................................................................................

Chapter 9 Troubleshooting for Voice 9-1............................................................9.1 Overview 9-1................................................................................................9.2 Fundamental Knowledge 9-1........................................................................

9.2.1 Transmission Format of Voice Signal 9-1............................................9.2.2 Transmission Path of Voice Signal 9-2................................................9.2.3 Concepts 9-4........................................................................................9.2.4 Common Operations 9-4......................................................................9.2.5 Supplement 9-6....................................................................................

9.3 Processing of Voice Troubles 9-7.................................................................9.3.1 Analysis 9-7..........................................................................................9.3.2 Location Procedures 9-8......................................................................

9.4 Trouble Location 9-9.....................................................................................9.4.1 Single Pass and No pass 9-9...............................................................9.4.2 Echo 9-11...............................................................................................9.4.3 Voice Discontinuity 9-13.........................................................................9.4.4 Noise 9-14..............................................................................................9.4.5 Cross-talking 9-16..................................................................................

9.5 Fault Examples 9-17.......................................................................................9.5.1 Cross-talking Resulting from Improper Data Configuration 9-17...........9.5.2 Voice Discontinuity Resulting from BCCH CarrierMutual-assistance 9-18...................................................................................9.5.3 Single Pass Resulting from MS Fault 9-19............................................9.5.4 Noise Resulting from Poor Contact of E1 9-19......................................9.5.5 Voice Loopback Resulting from Outgoing Cabling 9-21........................

Chapter 10 Troubleshooting for Call Drop 10-1....................................................10.1 Overview 10-1..............................................................................................

10.1.1 Description 10-1...................................................................................10.1.2 Formula for Call drop 10-3...................................................................

10.2 Causes 10-4.................................................................................................10.2.1 Coverage 10-4.....................................................................................10.2.2 Handover 10-6.....................................................................................10.2.3 Interference 10-8..................................................................................10.2.4 Uplink/downlink Unbalance Caused by Antenna & FeederSystem 10-10....................................................................................................10.2.5 Transmission Failure 10-11....................................................................10.2.6 Unreasonable Parameter Settings 10-12...............................................10.2.7 Others 10-13..........................................................................................

10.3 Examples 10-13..............................................................................................10.3.1 Example 1: Reducing Call Drop by Optimizing HandoverRelated Parameter 10-13..................................................................................10.3.2 Example 2: Call Drop Caused by Interference 10-14.............................10.3.3 Example 3: Call Drop Caused by Interference 10-15.............................10.3.4 Example 4: Uplink/downlink Unbalance 10-16.......................................10.3.5 Example 5: Call Drop Caused by Interference from Repeater 10-16.....

10.3.6 Example 6: Call Drop Caused by Isolated Island Effect 10-17..............10.3.7 Example 7: Settings of Version Related Parameters 10-18...................

Chapter 11 Troubleshooting for Antenna & Feeder System 11-1.......................11.1 Overview 11-1..............................................................................................

11.1.1 Common Failures 11-2.........................................................................11.1.2 Common Causes of Failures 11-2.......................................................

11.2 Fundamental Knowledge 11-3......................................................................11.2.1 RF Transmission Path in Antenna Feeder System 11-3......................11.2.2 Measuring Standing Wave Ratio of Antenna Feeder 11-5...................11.2.3 Checking CDU Antenna Port TTA Power Feeding 11-6......................

11.3 Locating Failures of Different Types 11-8.....................................................11.3.1 On Downlink Signal 11-8......................................................................11.3.2 On Uplink Signal 11-9..........................................................................11.3.3 On Controlling and Alarm 11-10.............................................................

11.4 Examples 11-11..............................................................................................11.4.1 Insufficient Power Tolerance of Lightning Arrester CausedStanding Wave Ratio of Antenna Feeder Abnormal 11-11...............................11.4.2 EDU Internal Bias Tee Quality Problem Causing TTA FeedingFailure 11-11.....................................................................................................11.4.3 No Cable Connection between TX-COM and TX-DUP of CDUCausing Call Establishment Failure 11-12........................................................

HUAWEI

M900/M1800 Base Station Subsystem Troubleshooting Manual

V300R002

M900/M1800 Base Station Subsystem

Troubleshooting Manual

Manual Version T2-030303-20030331-C-4.00

Product Version V300R002

BOM 31033203

Huawei Technologies Co., Ltd. provides customers with comprehensive technical support and service. Please feel free to contact our local office, customer care center or company headquarters.

Huawei Technologies Co., Ltd.

Address: Administration Building, Huawei Technologies Co., Ltd.,

Bantian, Longgang District, Shenzhen, P. R. China

Postal Code: 518129

Website: http://www.huawei.com

Email: [email protected]

2003 Huawei Technologies Co., Ltd.

All Rights Reserved

No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.

Trademarks

, HUAWEI, C&C08, EAST8000, HONET, , ViewPoint, INtess, ETS, DMC,

TELLIN, InfoLink, Netkey, Quidway, SYNLOCK, Radium, M900/M1800, TELESIGHT, Quidview, Musa, Airbridge, Tellwin, Inmedia, VRP, DOPRA, iTELLIN, HUAWEI OptiX, C&C08 iNET, NETENGINE, OptiX, SoftX, iSite, U-SYS, iMUSE, OpenEye, Lansway, SmartAX are trademarks of Huawei Technologies Co., Ltd.

Notice

The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document don't constitute the warranty of any kind, express or implied.

About This Manual

Version

The product version corresponds to the manual is M900/M1800 Base Station Subsystem. V300R002

Contents

The manual consists of 11 chapters that brief the procedures and methods, troubleshooting for OMC, loading, links, clock, handover, congestion, access, voice, call drop, antenna & feeder.

z Chapter 1 General Procedures and Methods z Chapter 2 Troubleshooting for OMC z Chapter 3 Troubleshooting for Software Loading z Chapter 4 Troubleshooting for Links z Chapter 5 Troubleshooting for Clock z Chapter 6 Troubleshooting for Handover z Chapter 7 Troubleshooting for Congestion z Chapter 8 Troubleshooting for Access z Chapter 9 Troubleshooting for BSS Voice z Chapter 10 Troubleshooting for Call Drop z Chapter 11 Troubleshooting for Antenna & Feeder System

Target Readers

The manual is intended for the following readers:

z Marketing staff z Installation engineers & technicians z Operation & maintenance personnel

Conventions

This document uses the following conventions:

I. General conventions

Convention Description

Arial Normal paragraphs are in Arial.

Arial Narrow Warnings, cautions, notes and tips are in Arial Narrow.

Bold Headings, Command, Command Description are in boldface.

Terminal Display Terminal Display is in Courier New; message input by the user via the terminal is in boldface.

II. Command conventions


italic font Command arguments for which you supply values are in italics.

[ ] Elements in square brackets [ ] are optional.

{ x | y | ... } Alternative keywords are grouped in braces and separated by vertical bars. One is selected.

[ x | y | ... ] Optional alternative keywords are grouped in square brackets and separated by vertical bars. One (or none) is selected.

{ x | y | ... } * Alternative keywords are grouped in braces and separated by vertical bars. A minimum of one and maximum of all can be selected.

[ x | y | ... ] * Optional alternative keywords are grouped in square brackets and separated by vertical bars. Many (or none) are selected. ! A line starting with an exclamation mark is comments.

III. GUI conventions


< > Message entered via the terminal is within angle brackets.

[ ] MMIs, menu items, data table and field names are inside square brackets [ ].

/ Multi-level menus are separated by forward slashes (/). For example, [File/Create/Folder].

IV. Keyboard operation

Format Description

Press the key with key name expressed with a pointed bracket, e.g. , , , or.

Press the keys concurrently; e.g. means the three keys should be pressed concurrently.

Format Description

Press the keys in turn, e.g. means the two keys should be pressed in turn.

[Menu Option] The item with a square bracket indicates the menu option, e.g. [System] option on the main menu. The item with a pointed bracket indicates the functional button option, e.g. button on some interface.

[Menu1/Menu2/Menu3] Multi-level menu options, e.g. [System/Option/Color setup] on the main menu indicates [Color Setup] on the menu option of [Option], which is on the menu option of [System].

V. Mouse operation

Action Description

Click Press the left button or right button quickly (left button by default).

Double Click Press the left button twice continuously and quickly.

Drag Press and hold the left button and drag it to a certain position.

VI. SymbolsEye-catching symbols are also used in this document to highlight the points worthy of special attention during the operation. They are defined as follows:

Caution, Warning, Danger: Means reader be extremely careful during the

operation.

Note, Comment, Tip, Knowhow, Thought: Means a complementary description.

Troubleshooting Manual M900/M1800 Base Station Subsystem Table of Contents

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Table of Contents

Chapter 1 General Procedures and Methods ............................................................................. 1-1 1.1 Requirements for Maintenance Personnel ........................................................................ 1-1

1.1.1 On Professional Knowledge and Skills ................................................................... 1-1 1.1.2 On BSS System and Networking ............................................................................ 1-1 1.1.3 On BSS Equipment ................................................................................................. 1-1 1.1.4 On Instruments and Apparatus ............................................................................... 1-2

1.2 General Procedures of Troubleshooting............................................................................ 1-2 1.2.1 Information CollectionCollecting Original Information as Detailedly as Possible.. 1-2 1.2.2 Fault judgement-Judge the Scope and Type of the Fault ....................................... 1-3 1.2.3 Fault Location-Specifying the Concrete Cause of the Fault ................................... 1-4 1.2.4 Fault Removing-Removing the Fault and Restore the System by Using Suitable Methods or Steps ............................................................................................................. 1-4

1.3 Basic Methods of Fault Judgement and Location.............................................................. 1-4 1.3.1 Analysis of Original Information .............................................................................. 1-4 1.3.2 Alarm Information Analysis ..................................................................................... 1-5 1.3.3 Indicator Status Analysis......................................................................................... 1-5 1.3.4 Calling Test Auxiliary Analysis ................................................................................ 1-6 1.3.5 Apparatus & Meter Auxiliary Analysis ..................................................................... 1-7 1.3.6 Traffic Statistics Auxiliary Analysis.......................................................................... 1-8 1.3.7 Interface Trace ........................................................................................................ 1-9 1.3.8 Test/Loop Back ..................................................................................................... 1-12 1.3.9 Comparison/Interchange....................................................................................... 1-13 1.3.10 Switching/Resetting............................................................................................. 1-14 1.3.11 Contacting the Technical Support Engineers of Huawei .................................... 1-15

Chapter 2 Troubleshooting for OMC ........................................................................................... 2-1 2.1 GSM BSS-OMC Overview................................................................................................. 2-1 2.2 Troubleshooting for OMC and Examples .......................................................................... 2-2

2.2.1 Communication Between BAM and Host Interrupted ............................................. 2-2 2.2.2 Communication between BAM and Server is Interrupted....................................... 2-3 2.2.3 Data Table Error is Prompted during BAM Startup................................................. 2-3 2.2.4 Loading Host Programs from BAM Failed .............................................................. 2-4 2.2.5 Data cannot be Modified/Deleted............................................................................ 2-4 2.2.6 At Least One Table in BSC Data Management System Report Has Error............. 2-5 2.2.7 Communication Timeout of Interface Tracing through BSC Maintenance System 2-5 2.2.8 Alarm System Cannot Receive Alarms................................................................... 2-6 2.2.9 BAM Prints Fail to shake hands with alarm server ............................................... 2-7 2.2.10 Records in Alarm Box and Those in Fault Alarm table Inconsistent..................... 2-8


ii

2.2.11 Shaking Hand with BAM Fails When the Alarms are Deleted through Alarm System.......................................................................................................................................... 2-9 2.2.12 Failed to Register due to Server Failure ............................................................... 2-9 2.2.13 Service Console Running Failed......................................................................... 2-10 2.2.14 Loading Shell Map Failed.................................................................................... 2-10 2.2.15 Some Computers Cannot Refresh Templates in BSC Traffic Statistics System 2-11

Chapter 3 Troubleshooting for Software Loading ..................................................................... 3-1 3.1 Troubleshooting for BTS Software Loading....................................................................... 3-1

3.1.1 Introduction to Software Loading ............................................................................ 3-1 3.1.2 Description of Common Loading Troubles.............................................................. 3-3 3.1.3 Trouble Handling..................................................................................................... 3-3 3.1.4 An Example of Loading BTS Software Failure on the Remote WS........................ 3-6

3.2 Troubleshooting for BSC Software Loading ...................................................................... 3-7 3.2.1 BSC Software Loading Channels............................................................................ 3-7 3.2.2 AM/CM Loading Fails.............................................................................................. 3-7 3.2.3 AM/CM Loading Timeout ...................................................................................... 3-10 3.2.4 BM Loading Failed and LOAD Indicator is Constantly ON ................................... 3-11 3.2.5 BM Loading Timeout ............................................................................................. 3-13 3.2.6 BM Loading Starts Again after Successful Loading.............................................. 3-14 3.2.7 BM Does Not Work Normally or Reload Automatically ......................................... 3-15 3.2.8 Operating Parameters Not Updated after Data Loading....................................... 3-16

Chapter 4 Troubleshooting for Links .......................................................................................... 4-1 4.1 Overview ............................................................................................................................ 4-1 4.2 Fundamental Knowledge ................................................................................................... 4-1

4.2.1 SS7 Concepts ......................................................................................................... 4-1 4.2.2 SS7 Direction .......................................................................................................... 4-2 4.2.3 GMC2 ...................................................................................................................... 4-2 4.2.4 Pb Interface............................................................................................................. 4-2 4.2.5 Signaling Direction on LAPD Links ......................................................................... 4-4

4.3 Trouble Handling................................................................................................................ 4-4 4.3.1 No SS7 Signaling Trace Message .......................................................................... 4-4 4.3.2 RSL Disabled .......................................................................................................... 4-5 4.3.3 OML Disabled.......................................................................................................... 4-6 4.3.4 SS7 Link Faulty ....................................................................................................... 4-7 4.3.5 AM/CM-BM Link Faulty ......................................................................................... 4-13 4.3.6 Optical Path Faulty................................................................................................ 4-13 4.3.7 PbSL Disabled....................................................................................................... 4-14 4.3.8 E1 Faulty ............................................................................................................... 4-15 4.3.9 Microcell's Optical Transmission Board Faulty ..................................................... 4-16

4.4 Examples ......................................................................................................................... 4-18 4.4.1 Examples of SS7 Link Trouble.............................................................................. 4-18 4.4.2 Examples of RSL & OML Troubles ....................................................................... 4-19


iii

4.4.3 Examples of E1 Transmission Trouble ................................................................. 4-21 4.4.4 Examples of Optical Transmission Board Trouble in Microcell............................. 4-26

Chapter 5 Troubleshooting for Clock.......................................................................................... 5-1 5.1 Overview ............................................................................................................................ 5-1

5.1.1 Fault Description and Fault Causes in BSC Clock System .................................... 5-1 5.1.2 Fault Description and Fault Causes in BTS Clock System..................................... 5-2

5.2 Fundamental Knowledge ................................................................................................... 5-4 5.2.1 Introduction to BSC ................................................................................................. 5-4 5.2.2 Fundamental Knowledge of BTS Clock System ................................................... 5-13 5.2.3 Specifications about BTS Clock System............................................................... 5-18

5.3 Trouble Handling.............................................................................................................. 5-18 5.3.1 Trouble Handling for BSC ..................................................................................... 5-18 5.3.2 Troubleshooting for BTS ....................................................................................... 5-20

5.4 Examples ......................................................................................................................... 5-23 5.4.1 Troubleshooting Examples for BSC Clock Fault................................................... 5-23 5.4.2 Troubleshooting Examples for BTS Clock Fault ................................................... 5-25

Chapter 6 Troubleshooting for Handover ................................................................................... 6-1 6.1 Overview ............................................................................................................................ 6-1

6.1.1 Failure Classification ............................................................................................... 6-1 6.1.2 Locating Tool........................................................................................................... 6-1

6.2 Trouble Handling................................................................................................................ 6-2 6.2.1 Locating Procedure ................................................................................................. 6-2 6.2.2 Locating Procedure of No Handover Starting Up.................................................... 6-3 6.2.3 Locating of Hardware Failure .................................................................................. 6-4 6.2.4 Locating of Data Configuration Problem ................................................................. 6-4

6.3 Examples ........................................................................................................................... 6-5 6.3.1 MSC Handover Problem ......................................................................................... 6-5 6.3.2 BSC Problems....................................................................................................... 6-10 6.3.3 BTS-related Problem............................................................................................. 6-16 6.3.4 Others.................................................................................................................... 6-21

Chapter 7 Troubleshooting for Congestion................................................................................ 7-1 7.1 Overview ............................................................................................................................ 7-1 7.2 A-Interface Congestion ...................................................................................................... 7-1

7.2.1 Fundamental Knowledge ........................................................................................ 7-1 7.2.2 Troubleshooting Process ........................................................................................ 7-2

7.3 Radio Channel Congestion................................................................................................ 7-4 7.3.1 Fundamental Knowledge ........................................................................................ 7-4 7.3.2 Analysis ................................................................................................................... 7-5

7.4 Examples ........................................................................................................................... 7-7 7.4.1 Example of SDCCH Congestion Resulted from Co-frequency Interference .......... 7-7 7.4.2 A Cells Congestion rate is Overhigh ...................................................................... 7-8


iv

7.4.3 Severe SDCCH Congestion Resulted from Unstable Transmission ...................... 7-8 7.4.4 SDCCH Congestion Resulted from Lots of Burst LA Updating .............................. 7-9 7.4.5 High TCH Congestion Rate Resulted from Incorrect CIC Setting ........................ 7-10 7.4.6 High SDCCH Congestion Rate LAC Resulted from Improper LAC Setting.......... 7-11

Chapter 8 Troubleshooting for Access....................................................................................... 8-1 8.1 Overview ............................................................................................................................ 8-1

8.1.1 MS Searching Network ........................................................................................... 8-1 8.1.2 Location Updating Procedure.................................................................................. 8-1 8.1.3 Call Procedures....................................................................................................... 8-3

8.2 Trouble Handling................................................................................................................ 8-5 8.2.1 MS Cannot Find a Network ..................................................................................... 8-5 8.2.2 MS Cannot Access a Network ................................................................................ 8-7 8.2.3 Location Updating Is too Frequent .......................................................................... 8-9 8.2.4 MS Drops from the Network Frequently.................................................................. 8-9 8.2.5 MS Finds a Network but Cannot Call .................................................................... 8-10

Examples .............................................................................................................................. 8-11 8.3 .......................................................................................................................................... 8-11

8.3.1 MS Has Difficulty in Accessing a Network Signal Is too Weak .......................... 8-11 8.3.2 MS Cannot Perform Cell Reselection Signals of Adjacent Cells Are Weak ...... 8-11 8.3.3 GSM MS Drops from the Network Location Updating Period Is too Short ........ 8-12 8.3.4 MS Drops from the Network CGI is Erroneous .................................................. 8-13 8.3.5 MS Has Difficulty in Accessing a Network MSC Cell Data Is not Ready........... 8-14 8.3.6 MS Drops from the Network MSC Cell Data Is not Ready ................................ 8-15 8.3.7 Some MSs Cannot Access a Network System Information Is Erroneous ......... 8-16 8.3.8 MS Has Difficulty in Accessing a Network CBQ and CBA Are Erroneous......... 8-17

Chapter 9 Troubleshooting for Voice.......................................................................................... 9-1 9.1 Overview ............................................................................................................................ 9-1 9.2 Fundamental Knowledge ................................................................................................... 9-1

9.2.1 Transmission Format of Voice Signal ..................................................................... 9-1 9.2.2 Transmission Path of Voice Signal ......................................................................... 9-2 9.2.3 Concepts ................................................................................................................. 9-4 9.2.4 Common Operations ............................................................................................... 9-4 9.2.5 Supplement ............................................................................................................. 9-6

9.3 Processing of Voice Troubles ............................................................................................ 9-7 9.3.1 Analysis ................................................................................................................... 9-7 9.3.2 Location Procedures ............................................................................................... 9-8

9.4 Trouble Location ................................................................................................................ 9-9 9.4.1 Single Pass and No pass ........................................................................................ 9-9 9.4.2 Echo ...................................................................................................................... 9-11 9.4.3 Voice Discontinuity................................................................................................ 9-13 9.4.4 Noise ..................................................................................................................... 9-14 9.4.5 Cross-talking ......................................................................................................... 9-16


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9.5 Fault Examples ................................................................................................................ 9-17 9.5.1 Cross-talking Resulting from Improper Data Configuration .................................. 9-17 9.5.2 Voice Discontinuity Resulting from BCCH Carrier Mutual-assistance .................. 9-18 9.5.3 Single Pass Resulting from MS Fault.................................................................... 9-19 9.5.4 Noise Resulting from Poor Contact of E1 ............................................................. 9-19 9.5.5 Voice Loopback Resulting from Outgoing Cabling ............................................... 9-21

Chapter 10 Troubleshooting for Call Drop................................................................................ 10-1 10.1 Overview........................................................................................................................ 10-1

10.1.1 Description .......................................................................................................... 10-1 10.1.2 Formula for Call drop .......................................................................................... 10-3

10.2 Causes........................................................................................................................... 10-4 10.2.1 Coverage............................................................................................................. 10-4 10.2.2 Handover............................................................................................................. 10-6 10.2.3 Interference ......................................................................................................... 10-8 10.2.4 Uplink/downlink Unbalance Caused by Antenna & Feeder System ................. 10-10 10.2.5 Transmission Failure......................................................................................... 10-11 10.2.6 Unreasonable Parameter Settings.................................................................... 10-12 10.2.7 Others................................................................................................................ 10-13

10.3 Examples ..................................................................................................................... 10-13 10.3.1 Example 1: Reducing Call Drop by Optimizing Handover Related Parameter. 10-13 10.3.2 Example 2: Call Drop Caused by Interference.................................................. 10-14 10.3.3 Example 3: Call Drop Caused by Interference.................................................. 10-15 10.3.4 Example 4: Uplink/downlink Unbalance............................................................ 10-16 10.3.5 Example 5: Call Drop Caused by Interference from Repeater ......................... 10-16 10.3.6 Example 6: Call Drop Caused by Isolated Island Effect ................................... 10-17 10.3.7 Example 7: Settings of Version Related Parameters........................................ 10-18

Chapter 11 Troubleshooting for Antenna & Feeder System................................................... 11-1 11.1 Overview........................................................................................................................ 11-1

11.1.1 Common Failures................................................................................................ 11-2 11.1.2 Common Causes of Failures............................................................................... 11-2

11.2 Fundamental Knowledge ............................................................................................... 11-3 11.2.1 RF Transmission Path in Antenna Feeder System............................................. 11-3 11.2.2 Measuring Standing Wave Ratio of Antenna Feeder.......................................... 11-5 11.2.3 Checking CDU Antenna Port TTA Power Feeding ............................................. 11-6

11.3 Locating Failures of Different Types.............................................................................. 11-8 11.3.1 On Downlink Signal............................................................................................. 11-8 11.3.2 On Uplink Signal.................................................................................................. 11-9 11.3.3 On Controlling and Alarm.................................................................................. 11-10

11.4 Examples ..................................................................................................................... 11-11 11.4.1 Insufficient Power Tolerance of Lightning Arrester Caused Standing Wave Ratio of Antenna Feeder Abnormal ........................................................................................... 11-11 11.4.2 EDU Internal Bias Tee Quality Problem Causing TTA Feeding Failure ........... 11-11


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11.4.3 No Cable Connection between TX-COM and TX-DUP of CDU Causing Call Establishment Failure................................................................................................... 11-12

Troubleshooting Manual M900/M1800 Base Station Subsystem Chapter 1 General Procedures and Methods

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Chapter 1 General Procedures and Methods

1.1 Requirements for Maintenance Personnel

Nowadays the M900/M1800 base station subsystem (BSS) has found extensive application in the GSM network. Correspondingly it plays a more and more important role in the telecommunication network. Its stable and normal operation has to be guaranteed. Any possible trouble has to be removed as soon as possible. This manual describes how to locate and remove the possible trouble from BSS quickly.

The BSS maintenance personnel who is to use this manual should be acquainted with the following:

1.1.1 On Professional Knowledge and Skills

The BSS maintenance personnel should well grasp the following:

! Communication knowledge, including GSM principle, exchange principle, PCM principle, SDH principle, etc.

! Product knowledge, including BSS functional configuration, radio interface theory, calling flow, traffic flow, etc.

! Related signaling and protocols, including SS7, LAPD, LAPDm, etc. ! Related international technical specifications. ! PC network fundamentals, including Ethernet, TCP/IP, Client/Server, database,

etc. ! Skills in BSS routine operation, PC operation and instrument operation.

1.1.2 On BSS System and Networking

The maintenance personnel should be acquainted with BSS and the related networking, including:

! BSS hardware configuration and performance parameters. ! Networking topology between BSC and each BTS and multiplexing ratio and

trunk mode on the Abis interface. ! BSS cell distribution and attributes. ! BSS handover and power control parameters. ! Network configuration and channel allocation of the related transmission devices.

1.1.3 On BSS Equipment

In order to guarantee the troubleshooting efficiency and prevent any misoperation, the BSS maintenance personnel should get the related certificate and know the BSS operation process. The significant trouble should be handled by the personnel who


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have received Grade B (or above) training from Huawei Technologies Co., Ltd. Besides, the BSS maintenance personnel should also know:

! Which operations may cause interruption over part or all of the traffics. ! Which operations may cause equipment damage. ! Which operations may cause MS complaints. ! Which emergency or standby measures are provided.

1.1.4 On Instruments and Apparatus

Instruments and apparatus are very useful for BSS troubleshooting. Their visual data may directly tell the trouble location. Therefore, they can help to enhance the BSS troubleshooting efficiency. The BSS maintenance personnel should be able to use the following instruments and apparatus skillfully.

! Test MS ! Power meter ! Antenna & feeder analyzer ! Signaling analyzer ! Multimeter ! Oscilloscope ! Spectrum analyzer ! Frequency meter

1.2 General Procedures of Troubleshooting

Generally, the troubleshooting should go through the following four stages: Information collection -> Fault judgement -> Fault location ->Fault removing.

1.2.1 Information CollectionCollecting Original Information as Detailedly as Possible

I. Essential

Any fault processing procedures begins from the fault information collection of the maintenance personnel. There are four sources of fault information collection:

! Fault complaint from the customer or customer center; ! Analysis on traffic statistics items; ! Alarm output of the BSS alarm system; ! Routine maintenance or abnormality found during the scout

During BSS routine maintenance, most fault information is from the former three sources. However, usually the initially obtained fault information cannot describe the trouble completely and thoroughly, especially when the information is got via a phone call. The information cannot represent the essence of the fault unless it is given in detail.

Nowadays, the network size is growing and the complication of networking is increasing. The change in and interference from the various internal and external factors may constitute a negative impact on the normal running of the BSS.


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Consequently BSS faults might result from some more complex causes. This makes it more and more difficult to locate a BSS fault.

It is no use to just analyze the problem and try to solve it based on the inadequate information. It may enlarge the scope of faults to be located and increase the difficulty of solving them, even lead to the error processing methods, thus losing the best chance to remove the faults. So, it is essential to collect various original informations.

II. Practical

Although there are many factors for the fault of the BSS, they seldom function simultaneously. That is, only some or one of them function(s) at the specified time point. It implements the possibility to locate the fault by using the exclusive method.

In the initial stage of fault processing, the collection of original information shall help the maintenance personnel in locating the fault, and improve the efficiency of fault processing, reduce the possibility of error operation, thus making the customer more satisfied.

III. Suggestions on maintenance

! The maintenance personnel should collect the original information, especially in case of serious fault, so as to perform the next step.

! The maintenance personnel are strongly recommended to study the system theory, GSM theory, GSM specification and relative signaling knowledge so as to solve the problem as quickly as possible.

! When answering the fault complaint call, the maintenance personnel is suggested to gather as much information as possible.

! The maintenance personnel are also suggested to create the environment with their companion, under which they are able to communicate and ask for help easily.

1.2.2 Fault judgement-Judge the Scope and Type of the Fault

After the fault information is collected, the scope and type of the fault are to be judged.

I. Judge the scope of the fault

The determining of the fault scope is to find the direction of fault processing, that is, where and how to find the concrete cause of the fault.

In the BSS, the fault scope refers to the area where the fault happens. It often has something to do with the location of the BSS. In the manual, the fault scopes are determined based on the application of the BSS. The manual consists of ten parts:

! OMC fault; ! Load fault ! Link fault; ! Clock fault; ! Handover fault; ! Congestion fault;


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! Access fault; ! Voice fault; ! Call drop fault; ! Antenna and feeder fault;

II. Judge the type of the fault

The judgement of the type of the fault is to decide to use what methods to analyze and solve the problem.

The fault categorization shall undergo in different methods, which are going to be discussed in the subsequent chapters.

Refer to the section of 1.3 Basic Methods of Fault Judgement and Location for the mostly used fault judgement methods.

1.2.3 Fault Location-Specifying the Concrete Cause of the Fault

As mentioned in the above, although there are many factors for the fault of the BSS, they seldom function simultaneously. That is, only some or one of them function(s) at the specified time.

The fault location is to exclude the impossible causes and find the right ones from many possible causes.

The accurate and fast location can not only improve the troubleshooting efficiency but avoid the man-made accidents caused by the error operation. It provides the key instruction and reference for the fault processing methods.

The basic methods of fault judgement and location shall be introduced briefly in the next section.

1.2.4 Fault Removing-Removing the Fault and Restore the System by Using Suitable Methods or Steps

After the fault is located, the procedure of fault removing is implemented as the last step of troubleshooting.

Fault removing is to remove the fault and restore the system by using some measures, such as checking transmission line, replacing board, modifying configuration data, switching system, resetting board, etc.

1.3 Basic Methods of Fault Judgement and Location

1.3.1 Analysis of Original Information

Original information consists of the fault information collected through the subscriber fault complaint, the fault notification from other offices, the abnormality met during maintenance and other information collected by the maintenance personnel. It is the important material for the fault judgement and analysis.

The original information analysis is used to judge the fault scope, specify the fault type, and to provide the gist for reducing the fault scope and initial locating of fault. If


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the maintenance personnel are experienced, they are even able to locate the fault directly.

The BSS maintenance personnel usually can get more than what they expect if they do well in collecting the original information and analyzing it effectively and thoroughly.

Besides handling the MS related trouble, the original information analysis can also be used to handle other troubles, especially the trunk trouble. Trunk is related to transmission system interconnection and signaling matching; therefore, the original information collection seems to be vital to trunk troubleshooting. Such original information includes the operating status (normal or not) of transmission system, state (modified or not) of data at the peer office, definitions of some signaling parameters, etc.

1.3.2 Alarm Information Analysis

Alarm information is the information output from the BSS alarm system, indicated usually through sound, light, Light Emitting Diode (LED), and screen output, etc. The alarm information output from the alarm maintenance system includes the detailed description of the abnormality, possible causes and restoration suggestions. It involves the hardware, link, trunk and Central Processing Unit (CPU) loading ratio, etc., with abundant and complete information. It is a gist for the fault analysis and location.

The alarm information analysis is mainly used to find the specified section or cause of the fault. Due to its abundant contents, the alarm information may be used to locate the fault cause itself or along with other methods. It is one of the main methods for fault analysis.

1.3.3 Indicator Status Analysis

Each board has status indicators. These indicators can indicate the work status of circuit, link, optical path, node and active/standby mode besides that of the corresponding boards, so they are much helpful for the fault analysis and location.

The indicator status analysis is mainly used to find the probable fault section or cause quickly and provide the materials for the next processing. Due to the inadequacy of the information indicated by the indicators, they are used along with the alarm information generally.

[Example]

Take indicators of the BIE for example. Table 1-1 describes the indicators of the BIE. Two of them are cited as below:

! When the indicator LIU1 is ON, it can be considered that the first E1 cable of the board is not connected with the corresponding BTS. The reason may be that the E1 cable is wrongly connected or that the transmission equipment is erroneous.

! When the indicator ACT is ON, it can be considered that the board acts as an active board.

For other indicators, refer to the following table.


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Table 1-1 Indicator description of the BIE

Indicator name Color Meaning Description Normal status

RUN Green Run indicator

ON: FPGA loading. ON 0.25s & OFF 0.25s: the board is not in operation. ON 1s & OFF 1s: the board is in normal operation. OFF: self-check fault and LIU1~LIU6 are ON.

ON 1s & OFF 1s

ACT Green Active/standby indicator ON: the board is active. OFF: the board is standby. ON/OFF

LIU1 Green Group 1 E1 indicator ON: local-end loss of synchronization. ON 1s & Off 1s: peer alarm. OFF: the first E1 is connected.

OFF

LIU2 Green Group 2 E1 indicator ON: local-end loss of synchronization. ON 1s & Off 1s: peer alarm. OFF: the second E1 is connected.

OFF

LIU3 Green Group 3 E1 indicator ON: local-end loss of synchronization. ON 1s & Off 1s: peer alarm. OFF: the third E1 is connected.

OFF

LIU4 Green Group 4 E1 indicator ON: local-end loss of synchronization. ON 1s & Off 1s: peer alarm. OFF: the fourth E1 is connected.

OFF

LIU5 Green Group 5 E1 indicator ON: local-end loss of synchronization. ON 1s & Off 1s: peer alarm. OFF: the fifth E1 is connected.

OFF

LIU6 Green Group 6 E1 indicator ON: local-end loss of synchronization. ON 1s & Off 1s: peer alarm. OFF: the sixth E1 is connected.

OFF

[Notes]

The maintenance personnel should be familiar with the meanings of indicator status so as to respond quickly in case of faults.

1.3.4 Calling Test Auxiliary Analysis

Within all the services provided by the BSS, the greatest portion is the voice service, so most of the fault relative with the BSS will affect directly or indirectly the normal calls of subscribers. So, the calling test is a simple and quick method to judge whether the call processing function and relative modules of the BSC are normal or not. It is often used to judge the normality of MS (Mobile Station), BTS (Base Transceiver Station), BSC (Base Station Controller), trunk system, etc.

[Example]

There was a BTS30 with configuration of S(1/1/1). Its three cells were respectively at the frequency of 119, 123 and 105. The call initiated via this BTS had no voice, whether the call was to an MS or to a fixed phone.

The troubleshooting process is given below:

1) At the remote maintenance console, the engineer viewed the TRX and TMU states and found they were normal and no alarm was generated.

2) Via signaling trace, the engineer found the call procedure was complete.


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3) The BTS was located in the second module of the BSC where the other BTSs were normal. The engineer checked the BSC data configuration and found no problem.

4) The engineer opened the back door of the BTS to check the cables and found everything was all right.

5) The engineer performed soft & hard reset over the BTS, pulled the TMU out and then reinserted it and reloaded the software. However, the trouble was not removed yet. He then replaced the TMU and TRX, but the trouble still existed.

6) In the BSC equipment room, the engineer changed the BTS to another trunk port and found that call can be set up via that BTS with that configuration. The possibility of BTS failure was excluded.

7) The engineer pulled out the BIE and then reinserted it, replaced the trunk cable and HW; however, the trouble still existed.

8) The engineer performed several dialing tests using an MS and found the MS could not be disconnected. He suspected that the problem lied in time slot interchange. As is known, time slot interchange problem is usually caused by E3M or GNET failure.

9) The engineer switched over the GNET and found call voice could be heard. When he switched the active GNET back, the call voice disappeared again. He then replaced the active GNET with the standby and found the call voice could not be heard yet. It indicated that the problem lied in both the active GNET and the corresponding slot.

[Notes]

The calling test is one of the mostly used methods in the routine maintenance. It is often employed along with the interface message trace, and used widely in the testing of various functions of the BSS.

1.3.5 Apparatus & Meter Auxiliary Analysis

The apparatus and meter auxiliary analysis is the widely used technical method of fault analysis and location for the BSS fault processing. It reflects the fault nature with the visual and quantified data, and is often used in the power test, signaling analysis, wave analysis and error code detection, etc.

[Example]

Call drop rate was high.


1) The engineer intercepted the signaling of some dropped calls using MA10. 2) He analyzed the signaling and found the TA approached 63. It indicated that the

reason was that the TA was too great. 3) The engineer modified the data configuration to reduce the cell coverage. 4) Then the call drop rate decreased. [Notes]


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The maintenance personnel should be able to operate the meters.

1.3.6 Traffic Statistics Auxiliary Analysis

The call drop rate is one of the key indices of the BSS, because it affects directly the operators' income and is one of the key elements for the core competition of the operators. So, the operators pay much attention to increase the handover successful ratio and reduce the call drop.

However, there are many possible causes affecting the call drop ratio of BSS, and they are hard to detect. So, the key to decrease the call drop ratio is to find the main causes generating the call loss in time and resist them. The traffic statistics is one of the analysis tools.

[Example]

One BTS30 was expanded from S (4/4) to S(8/4). (The TRX0, TRX1, TRX2, TRX3, TRX4, TRX5, TRX10 and TRX11 formed cell 1 and the TRX6-TRX9 formed cell 2.) After hardware expansion and the corresponding data setting, MS complained that calls made near the BTS were subject to beep affect. No alarm related to that BTS was generated.


1) According to the traffic statistics on TCH cell measurement, the number of TCH call drops of the cell 1 under that BTS was 63 and TCH call drop rate reached 3.7%. The number of A interface failures during TCH occupation was 63. The average number of idle TCHs in interference band 3 was 0.94, that in interference band 4 was 0.33 and that in interference band 5 was 1.21. According to the traffic statistics on intracell handover measurement, the number of unsuccessful outgoing BSC handovers of that cell was 35 and the number of unsuccessful incomming BSC handovers of that cell was 12. From the traffic statistics on outgoing cell handover measurement, the engineer found that the cause of outgoing cell handover was that the uplink quality of that cell was poor.

2) Since it was after the BTS expansion that the items of the cell 1 under that BTS indicated worse performance, the problem most probably lied in hardware connection or data configuration.

3) The engineer checked the CDUs, TRXs and all RF cables and found they were all properly and securely connected.

4) As the average number of idle TCHs in interference bands 3, 4 and 5 increased from 0 after the BTS expansion, it could be considered that the more A interface failures, lower outgoing/incoming cell handover success rate and higher TCH call drop rate were all related to interference.

5) The engineer checked the frequency planning data to see whether there were inter-frequency and co-BSIC adjacent cells and whether the frequency of TCH was adjacent to that of BCCH. No unreasonable setting was found.

6) The engineer checked whether the hopping related data configuration was right. For example, he checked whether BCC was identical to the training sequence No. (TSN) and whether the mobile allocation index offset (MAIO) and hopping


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sequence No. (HSN) were properly configured. He laid the checking emphasis on [Frequency Hopping Table], [Radio Channel Configuration Table], [TRX Configuration Table], [Cell Configuration Data Table] and [Cell Allocation Table].

7) When checking the [Radio Channel Configuration] Table, he found the MAIOs corresponding to the eight TRXs TRX0, TRX1, TRX2, TRX3, TRX4, TRX5, TRX10 and TRX11 of the cell 1 were respectively 0, 1, 2, 3, 4, 5, 7 and 8. Obviously such setting was erroneous. The engineer modified the MAIOs respectively to 0, 1, 2, 3, 4, 5, 6 and 7, set the whole table to the specified module and then reset the BTS at the fourth hierarchy.

8) One hour later, the engineer viewed the traffic statistics on TCH cell measurement. He found that the average number of idle TCHs in interference bands 3, 4 and 5 was all 0, that the number of A interface failures during TCH occupation was 0 and that the number of TCH call drops was 1. He then viewed the traffic statistics on intracell handover measurement and found that the number of unsuccessful outgoing BSC handovers of that cell was 0 and the number of unsuccessful incomming BSC handovers of that cell was also 0.

9) When the engineer performed dialing tests near the BTS, the beep affect disappeared. So the trouble was removed.

[Notes]

The traffic statistics analysis is often used along with the signaling trace and analysis, and it plays an important role in high call drop ratio, low handover successful ratio, call abnormality, etc. The maintenance personnel are strongly suggested to master it.

1.3.7 Interface Trace

The interface trace is applied in locating the failure causes of subscriber call connection and inter-office signaling cooperation, etc. The trace result can help to find the cause of call failure directly and locate the problem or to get the index for the subsequent analysis.

[Example]

There were two Huawei BSCs (BSC1 and BSC4). The BSC1 was connected with Huawei MSC1 and BSC4 with MSC2 from the manufacturer S. During operation, it was found the BSC4-to-BSC1 handover success rate was over 90% while the BSC1-to-BSC4 handover success rate was only about 20%.


1) During a light traffic period, the engineer performed a handover test on the site. He traced the signaling on the internal interface and that on the A interface via the maintenance console. Then he analyzed the collected data.

2) The signaling traced on the user interface of MSC1 was shown in Figure 1-1. Upon receipt of the message "Prepare Handover", MSC2 should have returned the message "Prepare Handover ACK"; however it returned the message "Abort" actually.


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MSC2 MSC1

Prepare Handover

Abort

Figure 1-1 Flow of signaling traced on the user interface of MSC1

3) The signaling traced on the A interface between MSC2 and BSC4 was shown in Figure 1-2.

MSC2 BSC4

Handover Request ACK

Clear Command

Handover Request

Clear Complete

Paging

None Connect Response

Figure 1-2 Flow of signaling traced on the A interface

4) The engineer checked the message "Handover Request" from MSC2 to BSC4 and found that MSC2 had transmitted the "Handover Required" message properly and transparently and the speech version information was specified via the channel type.

0B IE

04 Length

01 Speech

08 Full rate TCH channel Bm

91 GSM speech full rate version 2

01 GSM speech full rate version 1

The message "Handover Request ACK" BSC4 returned to MSC2 upon receipt of that message from MSC2 contained the following:

Layer 3 information: 17 0D 06 2B 38 51 0C 00 0C B3 05 DB 63 01 90

Chosen encryption algorithm: 2C 01


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Layer 3 information of the message indicated the Channel Mode:

63 IE

01 Speech Full rate TCH or Half Rate version 1

Then MSC sent the message "Clear Command" to BSC with "Cause: Protocol Error between MSC-BSC".

Since the phase version of the A interface between MSC2 and BSC4 was Phase 2, analysis over the signaling on the A interface should be based on Phase 2 protocol.

The difference between successful signaling and failed signaling lies in the speech version in channel type. So MSC2 expected the message "Handover Request ACK" returned from BSC4 could further indicate the speech version information. However, as is specified in Phase 2 GSM 08.08 protocol, the message "Handover Request ACK" contains no speech version information but the Channel Mode information that is indicated in Layer 3 information.

However, according Phase 2+ protocol, the message "Handover Request ACK" should contain the "Speech Version (Chosen)" when BSS selects a speech version. Details are cited below. (See "GSM 08.08 version 7.6.0".)

3.2.1.10 HANDOVER REQUEST ACKNOWLEDGE

This message is sent from the BSS to the MSC and indicates that the request to support a handover at the target BSS can be supported by the BSS, and also to which radio channel(s) the MS should be directed.

The message is sent via the BSSAP SCCP connection associated with the dedicated resource.

INFORMATION ELEMENT REFERENCE DIRECTION TYPE LEN Message Type

3.2.2.1 BSS-MSC M 1 Layer 3 Information

3.2.2.24 BSS-MSC M (1)11-n Chosen Channel

3.2.2.33 BSS-MSC O (4) 2 Chosen Encryption Algorithm

3.2.2.44 BSS-MSC O (5) 2 Circuit Pool

3.2.2.45 BSS-MSC O (2) 2 Speech Version (Chosen)

3.2.2.51 BSS-MSC O (6) 2 Circuit Identity Code

3.2.2.2 BSS-MSC O (3) 3 LSA Identifier

3.2.2.15 BSS-MSC O (7)5

1 This information field carries a radio interface HANDOVER COMMAND message.

2 Shall be included when several circuit pools are present on the BSS MSC interface and a circuit was allocated by the HANDOVER REQUEST message.

3 The Circuit identity code information element is included mandatorily by the BSS if the BSS allocates the A interface circuits and a circuit is needed.

4 Included at least when the channel rate/type choice was done by the BSS.

5 Included at least when the encryption algorithm has been selected by the BSS.


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6 Included at least when the speech version choice was done by the BSS.

7 Shall be included if a new potential current LSA in the target cell has been identified (see GSM 03.73). Not included means that there is no potential current LSA in the target cell.

Based on the above analysis, it could be concluded that the A interface phase version configured at MSC2 was different from that configured at BSC4 or that MSC2 processing on Phase 2 protocol was erroneous.

5) The engineer modified the A interface phase version configurations at those two sides and made them consistent with each other. From the traffic statistics, the engineer found the BSC1-to-BSC4 handover success rate became over 90%. So the trouble was removed.

[Notes]

The interface trace is able to locate the fault cause accurately and provide the valuable reference information, it is one of the widely used method in the BSS routine maintenance and fault processing.

1.3.8 Test/Loop Back

The test is to measure the relative technical parameters of output power, transmission channel or trunk device which may be in the fault status with the apparatus and meter, software test tool, etc., and to judge whether the devices are faulty or to be faulty.

The loop back is to perform the self sending and receiving (self loop) to one transmission device or channel with the hardware or software method. And judging the normality of transmission device, transmission channel, service status and signaling cooperation, etc. after the self loop so as to find whether the relative hardware condition and software parameter setting are normal or not. It is one of widely used method to locate the transmission problem and judge the correctness of trunk parameter setting.

[Example]

One office was to be expanded. During the expansion process, the office engineer decided to add an SS7 link with SLC of 2 (consistent with that at MSC) besides the expanded parts. The engineer then manually modified the data. After resetting the whole BSC, the engineer found the links configured automatically were all normal while the one added manually could not be established.

Three data tables were modified manually on the site: [E3M E1 Configuration Table], [MTP Link Table] and [Trunk Circuit Table]. The troubleshooting process is given below:

1) The engineer checked the related data and found that all data was right. The link was configured in the FTC 13. The engineer checked the [Trunk Circuit Table] and found that all the time slots with No. of 16 in the corresponding TCSM were properly set as Unavailable and they were described to act as A or Pb interface signaling links. The SS7 link run through the port 1 in the last BIE and it was configured to involve the time slot 16; therefore, the corresponding trunk circuit No. was right 2096.

2) The other two links in that module run through the port 0 in the transparent transmission BIE and were normal. The engineer suspected that the problem lied


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in the port 1. He replaced the port 0 with the port 1, modified the corresponding data configuration and set the whole table. The latter two links were still normal. The possibility of port 1 failure was excluded.

3) Via check, the engineer found the FTC indicator was in the normal state and that circuits of the FTC 13 were all normal.

4) The engineer looped back the BIE and found the link was normal. 5) He looped back the E3M and found the link was also normal. 6) Then he looped back the FTC and found the link was abnormal now. It indicated

that the problem lied in the parts between the E3M and TCSM. 7) The engineer suspected that data configuration in AM/CM was wrong. He vied

the Host and found the SS7 that should have been added to the [E3M E1 Configuration Table] was not added. It indicated that the data was not written into the Host. It could be concluded that the problem lied in the DIP switch.

8) The engineer checked the GMCC DIP switches in AM/CM and found the DIP switches with name of S1-2 and S1-4 were all set to ON (indicating that frozen data should be used). The engineer modified the DIP switches with name of S1-2 and S1-3 to ON and those with name of S1-4 to OFF. After he reloaded the data, the SS7 link became normal.

[Notes]

The test and loop back methods are usually employed along in the location of transmission fault. The loop back can be classified into hardware loop back and software loop back. The operation of software loop back is simple and flexible, but its reliability is not as good as the hardware loop back. In addition, the BSS trunk self loop is also often used to judge whether the parameters of local office and the outgoing route data are set correctly during the office deployment and trunk expansion.

1.3.9 Comparison/Interchange

Comparison is to compare the faulted components or phenomenon with the normal ones, and find the differences so as to find the problem. It is usually used in the situation with simple fault range.

Interchange is to interchange the normal components (such as board, optical fiber, etc.) with the potential faulted components if the fault range or part can not be located even after the standby components are replaced, and to compare the work status change after the interchange so as to specify the fault range or part. It is usually used in the situation with complicated fault range.

[Example]

During power-on commissioning over one BSC, the engineer found the GALM in AM/CM was displayed in red (indicating the faulty state). When the alarm box was powered on, it was still in red and the GALM communication alarm was generated additionally.


1) The engineer checked the data and found no problem.


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2) It is normal that the GALM in AM/CM is displayed in red when the alarm box is not powered on. The engineer powered on the alarm box; however, the GALM was still displayed in red and the trouble still existed.

3) The engineer viewed the DIP switch of the alarm box and found no problem. 4) The engineer then checked whether the GALM was faulty by replacing the

GALM in AM/CM with that in BM. He performed the replacing by modifying the GALM related DIP switch & jumper settings. Note: the AM/CM and BM use the same type of GALM except that the GALM related DIP switch & jumper settings of them are different. After replacing, the GALM in AM/CM was still displayed to be faulty.

5) The GALM in AM/CM may be displayed in red when communication between it and alarm box interrupts. The engineer suspected the problem lied in the signal cables of the alarm box. He replaced the alarm signal cables in BM with those in AM/CM. Now the GALM in AM/CM became normal.

6) Then the engineer checked the alarm signal cables carefully. He found the alarm signal cables in AM/CM were mixed up with those in BM. That was the reason why the communication between GALM in AM/CM and alarm box interrupted and GALM was displayed in red. The GALM in BM could not be displayed in red though its communication with the alarm box also interrupted because it itself operated normally.

[Notes]

In the actual fault location, various methods are used together, and in the above example, the methods of loop back, interchange, test and comparison are all used. We can see that the master of various methods will be quite helpful for the fault processing.

Caution:

It should be pointed out that the interchange is of a little risk, for example, after the short-circuited board is put to the normal frame, the normal frame may become faulted. So, cautions should be exercised in performing the interchange method so as to avoid new fault.

1.3.10 Switching/Resetting

Switching is to perform the manual switching for the switching device under the active/standby work mode, that is to forward the services from the active device to the standby. Compare the running status of the device after the switching to confirm whether the active device or the active/standby relationship is normal or not.

Resetting is to restart manually some the whole switching device or some parts of it. It is used to exclude software running is confused.


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The switching and resetting can not locate the fault cause accurately, and due to the randomness of software running, the fault may be not able to re-occur after the sw

BSS Troubleshooting Manual.pdf

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