Sjzl20083718-ZXG10 IBSC (V6.10) Maintenance Manual (Troubleshooting)

8/10/2019 Sjzl20083718-ZXG10 IBSC (V6.10) Maintenance Manual (Troubleshooting)

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ZXG10 iBSCBase Station Controller

Maintenance Manual(Troubleshooting)

Version 6.10

ZTE CORPORATION

ZTE Plaza, Keji Road South,Hi-Tech Industrial Park,Nanshan District, Shenzhen,P. R. China518057Tel: (86) 755 26771900 800-9830-9830

Fax: (86) 755 26772236URL: http://support.zte.com.cn

E-mail: [email protected]


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LEGAL INFORMATION

Copyright 2006 ZTE CORPORATION.

The contents of this document are protected by copyright laws and international treaties. Any reproduction ordistribution of this document or any portion of this document, in any form by any means, without the prior writtenconsent of ZTE CORPORATION is prohibited. Additionally, the contents of this document are protected bycontractual confidentiality obligations.

All company, brand and product names are trade or service marks, or registered trade or service marks, of ZTECORPORATION or of their respective owners.

This document is provided as is, and all express, implied, or statutory warranties, representations or conditions

are disclaimed, including without limitation any implied warranty of merchantability, fitness for a particular purpose,title or non-infringement. ZTE CORPORATION and its licensors shall not be liable for damages resulting from theuse of or reliance on the information contained herein.

ZTE CORPORATION or its licensors may have current or pending intellectual property rights or applications

covering the subject matter of this document. Except as expressly provided in any written license between ZTECORPORATION and its licensee, the user of this document shall not acquire any license to the subject matter

herein.

ZTE CORPORATION reserves the right to upgrade or make technical change to this product without further notice.

Users may visit ZTE technical support website http://ensupport.zte.com.cn to inquire related information.

The ultimate right to interpret this product resides in ZTE CORPORATION.

Revision History

Date Revision No. Serial No. Reason for Issue

January 7, 2009 R1.0 sjzl20083718 First Edition


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ZTE CORPORATIONValues Your Comments & Suggestions!

Your opinion is of great value and will help us improve the quality of our productdocumentation and offer better services to our customers.

Please fax to (86) 755-26772236 or mail to Technical Delivery Department, ZTEUniversity, Dameisha, Yantian District, Shenzhen, Guangdong, P. R. China 518083.

Thank you for your cooperation!

DocumentName

ZXG10 iBSC (V6.10) Base Station Controller Maintenance Manual (Troubleshooting)

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Contents

About This Manual ............................................................ i

Purpose................................................................................ i

Intended Audience ................................................................. i

Prerequisite Skill and Knowledge.............................................. i

What Is in This Manual ........................................................... i

Related Documentation.......................................................... ii

Conventions........................................................................ iii

How to Get in Touch............................................................. iv

Chapter 1..........................................................................1

Safety Instructions ..........................................................1

Safety Precautions ..........................................................1

Precautions ....................................................................1

Equipment Operations ...........................................................1

Board Operations..................................................................2

Data maintenance.................................................................2

Permission management........................................................2

Virus Prevention ...................................................................3

Fault Report .........................................................................3

Chapter 2..........................................................................5

Troubleshooting Overview ..............................................5

Troubleshooting Procedure ...............................................5

Common Methods to Locate Faults ....................................6

Alarm, notification and operation log view ................................6

Analysis of status indicator..................................................... 6

Performance Analysis ............................................................6

Analysis of Signaling Tracing ..................................................7

Analysis with instruments and meters ......................................7

Plugging/unplugging and pressing ...........................................7

Comparison and replacement..................................................7


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Isolation method .................................................................. 8

Self-test method .................................................................. 8

Contact Information of Technical Support from ZTE .............8

Chapter 3..........................................................................9

Clock Faults ......................................................................9

Overview of Clock Fault....................................................9

Related knowledge ............................................................... 9

Influence on service by clock faults........................................10

Alarm on Clock Faults ..........................................................10

Clock Fault Category............................................................10

Guide on Clock Faults ....................................................11

Critical and Major Alarm of BSC Clock Board............................11

Minor Alarm and Warning of BSC Clock Board..........................12

Alarm Cases on Clock Faults ...........................................13

Clock Reference Degradation Fault.........................................13

60ms Clock Alarm Caused by Clock Line Issue.........................13

Chapter 4........................................................................15

Access Faults..................................................................15

Overview of Access Fault................................................15

Related knowledge ..............................................................15

Influence on service by access faults......................................18

Alarm on Access Faults ........................................................18

Access Fault Category ..........................................................19

Troubleshooting Guide about Access Faults....................... 19

Frequent Location Update.....................................................19

Failure of MS Accessing the Network ......................................20

Network Busy Prompted at Call .............................................21

Call Returned Without Prompt ...............................................22

Call Connection Time Long....................................................23

Called Party Not in Service Area ............................................23

False MS Power-off ..............................................................24

Emergency Call Failure.........................................................24

High Priority Subscriber Access..............................................25

Alarm Cases on Access Faults .........................................26

Call Disconnection due to Different Voice Encryption Mode at CoreNetwork and Wireless Side ...................................................26


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Chapter 5........................................................................27

Handover Faults.............................................................27

Overview of Handover Faults ..........................................27

Related knowledge.............................................................. 27

Influence on service by handover faults.................................. 28

Alarm on Handover Faults .................................................... 28

Alarm on Handover Faults .................................................... 29

Troubleshooting Guide about Handover Faults ................... 29

Handover Failure Ratio High ................................................. 29

Failure of Handover to the Best Cell ....................................... 30

Handover Speed too Slow .................................................... 31

Alarm Cases on Handover Faults .....................................33Slow Inter-cell Handover...................................................... 33

Abnormal Handover with External Cells Because Handover Data isnot Added in LAC Cell at MSC Side ........................................ 33

Chapter 6........................................................................35

Congestion Faults ..........................................................35

Overview of Congestion Faults ........................................35


Influence on Service by Congestion Faults .............................. 35

Alarm on Congestion Faults .................................................. 35

Congestion Fault Category ................................................... 36

Troubleshooting Guide about Congestion Faults................. 36

SDCCH Congestion.............................................................. 36

TCH Congestion.................................................................. 37

A-Interface Circuit Congestion .............................................. 38

Alarm Cases on Congestion Faults ...................................38

High SDCCH Congestion Rate ............................................... 38

Chapter 7........................................................................41

Call Drop Faults..............................................................41

Overview of Call Drop Faults...........................................41


Influence on Service by Call Drops Fault................................. 43

Alarm on Call Drop Faults..................................................... 43

Category of Call Drop Fault................................................... 43

Troubleshooting Guide about Call Drop Faults....................44


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Call Drop due to Poor Coverage.............................................44

Call Drop due to Interference ................................................45

Call Drop due to Handover....................................................46

Call Drop due to Antenna Connection Error .............................47

Alarm Cases on Call Drop Faults...................................... 48

Handover and Reselection Fault Caused by CMM Board Clock Fault........................................................................................48

Chapter 8........................................................................51

Link Faults......................................................................51

Overview of Link Faults..................................................51


Influence on Service by Link Faults ........................................51Alarm on Link Faults............................................................51

Link Fault Category .............................................................52

Troubleshooting Guide about Link Faults .......................... 52

Calling Fault Caused by E1 Configuration Error ........................52

Alarm Cases on Link Faults............................................. 53

Call Disconnection Caused by Mismatched E1 Frame Format......53

Chapter 9........................................................................55

Voice Faults....................................................................55

Overview of Voice Fault.................................................. 55


Influence on service by voice faults........................................56

Alarm on Voice Faults ..........................................................56

Voice Fault Category............................................................57

Troubleshooting Guide about Voice Faults......................... 57

Abnormal Time Slot Calling...................................................57

Uplink/Downlink Voice Quality Fault .......................................58

Voice Fault Related to ON/ OFF of DTX ...................................58

Echo Problem .....................................................................60

Alarm Cases on Voice Faults ........................................... 61

B8018 Site Echo Issue .........................................................61

Work Abnormally after Configuring Dynamic Half-rate at B8018Site...................................................................................61

Chapter 10......................................................................63

Packet Service Faults.....................................................63


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Overview of Packet Service Faults ...................................63


Influence on Service by Packet Service Faults ......................... 64

Alarm on Packet Service Faults ............................................. 64

Packet Service Faults Category ............................................. 64

Troubleshooting Guide about Packet Service Faults ............65

BVC Status Abnormal .......................................................... 65

MS ATTACH Failure ............................................................. 65

MS PDP Activation Failure..................................................... 66

Slow Speed of MS Accessing Network .................................... 67

Alarm Cases on Packet Service Faults ..............................68

Can't Use GPRS Service With Connection Timeout Prompt......... 68

Chapter 11......................................................................69

Data and Software Loading Faults ................................69

Overview of Data and Software Loading Faults ..................69


Influence on Service by Data and Software Loading Faults ........ 69

Alarm on Data and Software Loading Faults............................ 70

Data and Software Loading Faults Category ............................ 70

Troubleshooting Guide about Data and Software LoadingFaults..........................................................................70

Mismatched Board Type and Version Configuration .................. 70

Version File not Existing....................................................... 71

Version File Check Error....................................................... 71

BTS Working Abnormally...................................................... 72

A-Interface Circuit Blocked................................................... 72

ISMG Synchronization Data Fault .......................................... 72

Alarm Cases about Data and Software Loading Faults.........73

iBSC Data Failed to Synchronize and Download to NE............... 73

Chapter 12......................................................................75

NM Faults .......................................................................75

Overview of NM Faults ...................................................75


Alarm on NM Faults ............................................................. 75

NM Fault Category .............................................................. 76

Troubleshooting Guide about NM Faults............................77

Client Can't Connect Server.................................................. 77


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ISMG Server Startup Failure .................................................78

Database Startup Failure ......................................................78

Full Data Table....................................................................79

Failure of Deleting Stored Software........................................81Failure of Querying Board Version Running in Foreground..........81

Board Running Abnormally ...................................................82

Failure of Observing Status Attribute in Dynamic Data

Management ......................................................................82

Failure of Alarm Box Displaying Audio/Visual Alarms.................83

Abnormal Performance Data Report .......................................83

Abnormal nfsdetect Process ..................................................84

nfsdetect Process Suspended ................................................85

Alarm Cases on NM Faults .............................................. 86After restarting iBSC OMP, background can't establish link withOMP ..................................................................................86

Software Version Can't be Synchronized to NE and SystemPrompts FTP Download Failed................................................86

"License file invalid or missing" occurs while configuringtransceiver.........................................................................87

Wrong time zone configuration causes performance report issue 87

Chapter 13......................................................................89

Connection Faults at Interface A...................................89

Overview of Connection Faults at Interface A .................... 89


Alarm on Interface A Connection Faults ..................................89

Category of connection faults at interface A.............................90

Troubleshooting Guide about Connection Faults at Interface A..................................................................................90

Service Unavailable in E1 Port ...............................................90

No. 7 Signaling Disconnected ................................................91

No. 7 Signaling Unstable ......................................................91

Alarm Cases on Connection Faults at Interface A ...............92

Call Fault Caused by Blocked MSC Circuit................................92

Service Fault One from Wrong Configuration at CN Side............93

Service Fault from Wrong Configuration at CN Side ..................93

Inconsistent Network Type Leads to Interface A Connection Fault........................................................................................94

Chapter 14......................................................................95

Connection Faults at Interface Gb.................................95


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Overview of Connection Faults at Interface Gb ..................95


Alarm on Interface Gb Connection Faults................................ 98

Category of connection faults at interface Gb .......................... 99

Troubleshooting Guide about Connection Faults at InterfaceGb ..............................................................................99

NSVC Disconnection ............................................................ 99

NSVC Connection Intermittent ............................................ 100

Can't ping iBSC successfully (IPGB) ..................................... 100

Can't ping SGSN successfully (IPGB).................................... 101

"GPRS Attach Reject" Alarm occurs while connecting GB Port .. 101

Alarm Cases on Connection Faults at Interface Gb ........... 102

GPRS Service Fault Caused by Wrong Data Configuration at GbInterface ......................................................................... 102

Chapter 15....................................................................105

Board Faults.................................................................105

Overview of Board Faults ............................................. 105

Influence on service by board faults..................................... 105

Alarm on Board Faults ....................................................... 105

Troubleshooting Guide about Board Faults ...................... 106

UIM/2 Board Hardware Fault .............................................. 106

OMP Board Hardware Fault................................................. 107

CMP Board Hardware Fault ................................................. 108

DTB Board Hardware Fault ................................................. 109

SDTB Board Hardware Fault ............................................... 110

GUP Board Hardware Fault ................................................. 110

SPB Board Hardware Fault.................................................. 111

GLI Board Hardware Fault .................................................. 112

CLKG Board Hardware Fault ............................................... 114

SBCX Board Hardware Fault ............................................... 115

PSN Board hardware fault .................................................. 116

CHUB Board hardware fault ................................................ 117

UIMU Optical Module Fault ................................................. 118

Alarm Cases on Board Faults ........................................ 119

Can't Start OMP due to Damaged ZDB Table ......................... 119

Instance one of OMP restarting repeatedly............................ 119

Instance two of OMP restarting repeatedly............................ 120

Appendix A...................................................................121


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Abbreviations ...............................................................121

Appendix B ...................................................................127

Figures..........................................................................127

Appendix C ...................................................................129

Tables...........................................................................129

Index ............................................................................131


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Confidential and Proprietary Information of ZTE CORPORATION i

About This Manual

Purpose

This manual introduces different faults and troubleshootingmethods and procedures.

Intended Audience

This document is intended for engineers and technicians whoperform operation activities on ZXG10 iBSC.

Prerequisite Skill and Knowledge

To use this document effectively, users should have a general

understanding of wireless telecommunications technology.

What Is in This Manual

This manual contains the following chapters:

TA B L E 1 - C H A P T E R SUM M ARY

Chapter Summary

Chapter 1, Safety

Instructions

Mainly introduces some safety precautions

for equipment maintenance.

Chapter 2,TroubleshootingOverview

Mainly introduces the process andcommon methods about troubleshootingfor reference by maintenance personnel.

Chapter 3, Clock Faults Describes common procedures foranalyzing and handling clock faults.

Chapter 4, AccessFaults

Describes common procedures foranalyzing and handling MS access faults.

Chapter 5, HandoverFaults

Describes common procedures foranalyzing and handling handover faults.

Chapter 6, Congestion Describes common procedures for


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ii Confidential and Proprietary Information of ZTE CORPORATION

Chapter Summary

Faults analyzing and handling congestion faults.

Chapter 7, Call Drop

Faults

Describes common procedures for

analyzing and handling call drop faults.

Chapter 8, Link Faults Describes common procedures foranalyzing and handling link faults.

Chapter 9, Voice Faults Describes common procedures foranalyzing and handling voice faults.

Chapter 10, PacketService Faults

Describes common procedures foranalyzing and handling packet servicefaults.

Chapter 11, Data andSoftware Loading Faults

Describes common procedures foranalyzing and handling BSC data andsoftware loading faults.

Chapter 12, NM Faults Describes common procedures foranalyzing and handling NM faults.

Chapter 13, ConnectionFaults at Interface A

Describes common procedures foranalyzing and handling connection faultsat interface A.

Chapter 14, ConnectionFaults at Interface Gb

Describes common procedures foranalyzing and handling connection faultsat interface Gb.

Chapter 15, BoardFaults

Describes common procedures foranalyzing and handling board faults.

Appendix A,

Abbreviation

Lists all abbreviations used in this manual.

Appendix B,

Figures

Lists the figures in this manual.

Appendix C,

Tables

Lists the tables in this manual.

Index Lists the index of this manual.

Related Documentation

The following documentation is related to this manual:

ZXG10 iBSC (V6.10) Base Station Controller Documentation

Guide

ZXG10 iBSC (V6.10) Base Station Controller TechnicalManual

ZXG10 iBSC (V6.10) Base Station Controller Hardware

Manual

ZXG10 iBSC (V6.10) Base Station Controller InstallationManual


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AboutThis Manual

Confidential and Proprietary Information of ZTE CORPORATION iii

ZXG10 iBSC (V6.10) Base Station Controller KPI Reference

Manual

ZXG10 iBSC (V6.10) Base Station Controller PerformanceCounter Manual Volume I

ZXG10 iBSC (V6.10) Base Station Controller Performance

Counters Manual Volume II

ZXG10 iBSC (V6.10) Base Station Controller MaintenanceManual (Routine Maintenance)

ZXG10 iBSC (V6.10) Base Station Subsystem Alarm HandlingManual

ZXG10 iBSC (V6.10) Base Station Subsystem NotificationHandling Manual

Conventions

ZTE documents employ the following typographical conventions.

TA B L E 2 - T Y P O G R A P H I C A L CO NVENT I O NS

Typeface Meaning

Italics References to other Manuals and documents.

Quotes Links on screens.

Bold Menus, menu options, function names, input

fields, radio button names, check boxes, drop-down lists, dialog box names, window names.

CAPS Keys on the keyboard and buttons on screensand company name.

Const ant wi dth Text that you type, program code, files anddirectory names, and function names.

[ ] Optional parameters.

{ } Mandatory parameters.

| Select one of the parameters that are delimitedby it.

Note: Provides additional information about acertain topic.

Checkpoint: Indicates that a particular step needsto be checked before proceeding further.

Tip: Indicates a suggestion or hint to make thingseasier or more productive for the reader.

TA B L E 3 - MO USE O P E R A T I O N C O NVENT I O NS

Typeface Meaning

TypographicalConventions

Mouse

OperationConventions


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iv Confidential and Proprietary Information of ZTE CORPORATION

Typeface Meaning

Click Refers to clicking the primary mouse button (usuallythe left mouse button) once.

Double-click Refers to quickly clicking the primary mouse button(usually the left mouse button) twice.

Right-click Refers to clicking the secondary mouse button(usually the right mouse button) once.

Drag Refers to pressing and holding a mouse button andmoving the mouse.

How to Get in Touch

The following sections provide information on how to obtainsupport for the documentation and the software.

If you have problems, questions, comments, or suggestionsregarding your product, contact us by e-mail [email protected]. You can also call our customer supportcenter at (86) 755 26771900 and (86) 800-9830-9830.

ZTE welcomes your comments and suggestions on the qualityand usefulness of this document. For further questions,comments, or suggestions on the documentation, you cancontact us by e-mail at [email protected]; or you can fax your

comments and suggestions to (86) 755 26772236. You can alsobrowse our website at http://support.zte.com.cn, which containsvarious interesting subjects like documentation, knowledge base,forum and service request.

CustomerSupport

DocumentationSupport


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Confidential and Proprietary Information of ZTE CORPORATION 1

C h a p t e r

1

Safety Instructions

This chapter mainly introduces some safety precautions for

equipment maintenance.

Safety PrecautionsOnly the professional personnel who have passed the relatedtraining can operate and maintain the equipment.

Basic requirements on maintenance personnel include:

Master BSS system theory;

Be familiar with BSS equipment principle and networking;

Hold certain network optimization skill.

During the operation and maintenance of the equipment, all thesafety rules and related operation procedures on the site mustbe strictly abided by, to avoid body injuries or equipmentdamages. The safety precautions introduced in this manual areonly supplementary to the local safety specifications.

ZTE shall in no way be liable for any losses or damages causedby violation of the universal safety operation requirements orthe safety standards for designing, manufacturing and using theequipment.

Precautions

Equipment Operations

Maintenance persons shall strictly follow operation rules.

Put on anti-static wrist straps before touching any hardware of

the equipment.


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2 Confidential and Proprietary Information of ZTE CORPORATION

Don't do the operation behavior out of daily maintenance scope.

Note:

Do not plug/unplug, reset or switch over boards at will. Do load

or modify data at will, and especially, do not modify data in theNMS database.

Board Operations

Wear antistatic strap when handling boards.

To plug/unplug or replace key critical boards, please preparesufficient personnel and boards to deal with unexpected events.

Check spare materials and parts regularly to ensure sufficient

stocks and their completeness and prevent them from gettingmoldy due to dampness.

Damaged parts shall be separated from spare parts with certainmarks on it and kept it in anti-static bag.

Data maintenance

Don't do data synchronization and modification in daytime, soyou shall select to do it in the low-traffic hours (i.e. midnight) ifpossible.

Operations concerning mass data submission should beconducted in the low-traffic hours (i.e. midnight) if possible.

Prior to data modification, data backup should be made. Duringdata modification, timely records should be made. After datamodification, the backup data should not be deleted until it isconfirmed that the system is running normally in a certain periodof time (normally one week).

Periodically backup all data for any emergent demands.

All databases, especially the performance measurement andalarm databases should be observed periodically (once every

two weeks). If t he database capacity is too high (exceeding thesize as recommended in ISMG), please delete old useless data toavoid any error of disk overflow.

Permission management

Only one super administrator is allowed in system management.

NM permission and password are managed by him uniformly.

Also, the permission to log on server and client shall be

configured by grade.


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Chapter 1 - Safety Instructions


Note:

Do not plug/unplug, reset or switch over boards at will. Do loador modify data at will, and especially, do not modify data in theNMS database.

Super administrator: Enjoying the maximum permission forany operation.

Senior operator: Enjoying the authority for dataconfiguration and modification, diagnostic test, performancemeasurement, alarm query and status query, but not foruser management.

Operator: Only enjoying the authority for alarm query andstatus query.

Also, the password to log on server and client shall be changedperiodically.

Virus Prevention

Maintenance personnel can't change network settings and othersettings on O&M server and client randomly.

Don't use external disk and CD on O&M server and client at yourdiscretion.

Don't run other programs unrelated with O&M on the server andclient. Don't play game on computer terminal.

Install original antivirus software for each client and neverdeactivate the real-time detection function. Keep the virusdatabase updated timely (weekly).

Install original antivirus software for the server with NT systemand never deactivate the real-time detection function. Keep thevirus database updated timely (weekly).

Fault Report

The maintenance personnel should settle the problems andfaults detected as soon as possible. If they find serious problems,they should report to the responsible supervisor immediatelyand contact local ZTE office. The whole fault dealing processshould be recorded in detail.


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C h a p t e r

2

Troubleshooting Overview

This chapter mainly introduces the process and common

methods about troubleshooting for reference by maintenancepersonnel.

Troubleshooting ProcedureIt commonly contains four phases: original information collection,Fault Analysis, fault cause location, and troubleshooting. Figure1 shows the troubleshooting procedure.

F I G URE 1 - T RO UBL ESHO O T I NG PRO CEDURE

Any troubleshooting begins with original information collection.

Original information mainly comes from alarms and notificationson ISMG client, status of board indicators, or customer faultreport.

After original information is collected, relevant personnel cananalyze it and judge the fault causes for the reference oftroubleshooting.

After trouble cause analysis, relevant personnel will use differenttroubleshooting methods to find out possible factors and finallyconfirm the root reason.

After the fault is located, maintenance personnel can enter intotroubleshooting phase and adopt proper measures to restorenormal operation.


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Common Methods to Locate

FaultsIn maintenance, faults can be located through the followingdifferent common methods:

Alarm, notification and operation logview

Alarm, notification and operation log view is the first method tobe adopted when a fault is detected by maintenance personnel.

It is implemented through the alarm management and operationlog view interface of the BSS operation & maintenancesubsystem ISMG.

Through the alarm management interface, we can observe andanalyze current alarms, history alarms, and normal notificationsreported from each NE such as the current alarm, history alarmand general notification. In this way, we can detect any faultduring network running in time and then locate, isolate andremove it.

By viewing operation logs in safety management, we caninvestigate modifications on system parameters, locate the

relevant responsible terminal and operator as well as detectfaults caused by individual operations in time.

Analysis of status indicator

The analysis of the indicator status is a common method used bythe maintenance personnel when a fault is found. With thismethod, we can locate and remove faults by observing theindicator status on each board panel in the rack.

This method requires maintenance personnel to be familiar with

the indicator status and meaning of each board.

Performance Analysis

It is implemented through the performance managementinterface of the BSS operation & maintenance subsystem ISMG.Through this interface, maintenance personnel can perform BSSperformance management.

With the performance management interface, users can createdifferent performance measurement tasks, generate different

performance reports and understand different performance


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Chapter 2 - Troubleshooting Overview


indices of BSS. By analyzing the information, maintenancepersonnel can detect load distribution in the network and adjustnetwork parameters in time to increase the networkperformance.

Analysis of Signaling Tracing

It is implemented through the signaling tracing tools in BSSO&M subsystem ISMG. Through the signaling tracing interface,we can trace signaling involved in BSS (including signals frominterface A, Gb, Abis, and Um), thus facilitating consulting ofdifferent signaling flows in the debugging and maintenanceprocesses as well as detection of problems in the signalinginterworking process.

Analysis with instruments andmeters

It indicates that in the BSC maintenance process, maintenancepersonnel use some auxiliary instruments such as the test MS,signaling analyzer and error analyzer in fault analysis, locationand removal.

Plugging/unplugging and pressing

When detecting a board fault, we can loosen the fixation screwin front/back panel and plug/unplug the board and externalinterface connector. In this way, we can remove faults causedby poor contact.

Pressing the cable connectors after power-off may also eliminatethe fault due to insecure contact.

Comparison and replacementComparison indicates to compare a possible faulty board with aboard at the similar position in the system (for example: a boardwith same logic function) from aspects such as the runningstatus, jumper and connection cables. We can judge whether theboard fails through comparison.

Replacement indicates to replace a possible faulty board with astandby part or another board of the same type runningnormally in the system.


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Isolation method

When a part of the system fails, it can be isolated from other

relevant boards or racks to judge whether the fault is caused bymutual influence.

Self-test method

It indicates fault judgment through self-testing after the systemor board is powered on again. Generally, during self-test of aboard after it is powered on again, the indicator on its panel willflash according to a certain rule. Based on that, we can judgewhether a board fails.

Contact Information ofTechnical Support from ZTEDuring troubleshooting, if any difficult problem occurs, you cancontact customer support center in ZTE, and ZTE will provideyou perfect technical support.

ZTE Customer Support Center Hotline:

800-830-1118 (Toll Free)

400-830-1118 (Toll Free)

0755-26770800


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C h a p t e r 3

Clock Faults

This chapter describes common procedures for analyzing and

handling clock faults.

Overview of Clock Fault

Related knowledge

Figure 2 shows the principle and structure of iBSC sync clock

system.

F I G URE 2 - PRI NCI PL E AND ST RUCT URE O F SYNC CL O CK S YST EM

Generation and distribution of sync clock is mainly finished byCLKG, UIMC, UIMU and relevant backplane and service board.


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System clock source using CLKG board includes BITS clock(2MB/2MHz in 2 lines), line clocks 8 KBASE (2 lines), localoscillation 8K.

During operation, CLKG selects clock reference source based on

defined priority to generate required 16M, 32M, and 8 K anddistribute it to UIMC/U in different frames through cable, thendistribute to proper board in this frame through backplane byUIMC/U; CLKG board communicates with UIMC/U via RS485,while receiving 8K clock reference extracted from trunk boardDTB or SDTB or SPB.

Influence on service by clock faults

If iBSC can't lock clock or clock source is lost, it may affect

network performance, such as handover success ratio; if faultoccurs on active/standby clock board, iBSC system goes down.

If clock alarm occurs at base station, it may cause some carriersor whole station can't work normally.

Alarm on Clock Faults

Table 4 shows alarm on clock faults.

TA B L E 4 - A L A R M O N C L O C K FA UL T S

Fault Causes Name of corresponding alarm

198005381 Level 1 alarm on abnormalaccess clock

198026129 Level 1 alarm on lost clockreference source

198026128 Level 2 alarm on lost clockreference source

198026113 Alarm on lost 32M8K outputclock

198026112 Alarm on lost 32M outputclock

198026114 16M output clock lost

Major alarm of the CLKGclock board

198026115 16M8K output clock lost

Clock Fault Category

According to alarm level, clock fault can be divided into critical,major, minor, and warning.


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Chapter 3 - Clock Faults


Guide on Clock FaultsCLKG indicator has plenty of meanings, so you shall know its

meanings, current clock state, and corresponding meanings ofalarm.

Confirm clock grade at upper office, CLKG equipment clockgrade at local terminal and clock position at interface A. Checkwhether background configuration and foreground wiring arecorrect.

After power on, CLKG board will first enter into BOOT program,while you can view board indicators. If the indicator flashes afterpower on, BOOT of CLKG may be failed, or poor contact existsfor the board.

Critical and Major Alarm of BSCClock Board

The ALM indicator of the board flashes or other indicators on thepanel show fault indication; the following are found throughbackground alarm query:

Abnormal access clock;

Phase-locked loop out of lock;

Level 1 alarm on lost clock reference source; Lost 16M output clock;

Lost 32M output clock;

Lost 32M8K output clock;

Lost 16M8K output clock;

Lost PP2S output clock;

Lost 16CHIP clock reference;

Lost all clock reference source;

Level 2 alarm on lost clock reference source;

Lost output clock.

Critical and major alarms are caused by hardware fault orreference loss for a long time.

Analyze it by the following steps:

1. Check clock reference (including wiring and RCLG backplane);

2. Check background data configuration;

3. Check the board's hard disk;

4. Check upper clock source.

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If only the active board has alarm, change over the CLKG boardto start the standby board. Then, replace the faulty board forrepair. If both boards have alarms, replace active/standby clockboard in turn to minimize the impact.

Handle the faults according to respective steps:

1. Modify clock reference, wiring, and backplane;

2. Change data configuration;

3. Change board;


Minor Alarm and Warning of BSCClock Board

You can find out the following alarms through background:

Alarm on lost 8KBASE clock reference source;

Alarm on lost 8KGPS clock reference source;

Alarm on lost clock reference source;

Out-of-lock alarm for lock-phase loop on clock board;

Minor alarm and warning on clock board are relaetd with clockreference or background configuration.

Analyze it by the following steps:1. Check clock reference (including wiring and RCLG backplane);

2. Check background data configuration;

3. Check the board's hard disk;


If only the active board has alarm, change over the CLKG boardto start the standby board. Then, replace the faulty board forrepair. If both boards have alarms, replace active/standby clockboard in turn to minimize the impact.

Handle the faults according to respective steps:

1. Modify clock reference, wiring, and backplane;

2. Change data configuration;

3. Change board;


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Chapter 3 - Clock Faults


Alarm Cases on Clock Faults

Clock Reference Degradation Fault

Red QUTD indicator is illuminated on CLKG board at certainoffice.

It may be caused by hardware fault, so you shall checkhardware.

It also may be caused by clock reference degradation, so youshall check clock reference.

Confirm there is no problem for clock wiring and backplane.

After replacing front board, QUTD indicator is off, so the fault issolved.

60ms Clock Alarm Caused by ClockLine Issue

Certain site is configured as S1/1/2. The following alarms occurfor secondary rack that is connecting with interface D at primaryrack:

Interruption of HDLC link between carrier and CMM;

Interruption of LAPD link between TRX and BSC;

Alarm on lost 60ms sync clock.

There is a broken signal cable in 60ms clock line in primary andsecondary rack. It is deducted that this fault is caused by clockline issue.

The alarm disappears after clock line is replaced.

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C h a p t e r

4

Access Faults


handling MS access faults.

Overview of Access Fault

Related knowledge

The access faults are divided into two types: location updateaccess faults and call access faults.

Common access faults include: failure of MS finding the network,the calling party directly bounced, and no response of the calledparty.

Figure 3 shows the location update process.


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F I G URE 3 - LOCATION UPDATE

The flow is described as follows:

1. The location update request of MS is sent to MSC throughthe Complete L3 information message of CR. If MSC acceptsthe request, it sends the location update accept message toMS; otherwise, it sends the location update rejectionmessage to MS.

If the location update request of MS is rejected, MS receives

the Location Updating Rejected message from MSC.The possible causes include:

MSC is not configured with CGI of the cell related to BSC.

Communication between MSC and VLR fails.

MS is not registered in HLR.

Figure 4 shows call flow.


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Chapter 4 - Access Faults


F I G URE 4 - CA L L FL O W

The flow is described as follows:

For the subscriber, if the flow does not reach the talk stage,then the call is not connected.

The possible causes include:

Access failure of the calling party

Access failure of the called party

2. Access failure of the calling party

Usually, it is due to that BSC does not send the AssignmentComplete message to MSC, for example:

i. BSC receives the Assignment Request message but BTSdoes not issue the Assignment Command message to MS.Instead, it directly returns the Assignment Fail message

to BSC.


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BSC has no available TCH.

The CIC assigned by MSC is not in idle state at the BSC

side. The assignment request message of MSC is illegal, for

example, the voice version does not match the circuitgroup.

ii. After BSC issues the Assignment Command message toMS, MS reports the Assignment Fail message.


Radio environment interference exists.

Signal of the assigned channel is too weak.

Hardware faults exist.

3. Access failure of the called party

For the called party, the call flow is a little different.

First there is a paging message and then MS responds to thepaging.

Based on the call flow, the possible causes of access failureare:

The location of MS has weak signals, thus MS fails toreceive the paging message.

The paging response access fails.

Influence on service by access faults

Access fault may generate the following influences:

Conversation influence: MS can not be used as calling orcalled side and network registration may be failed.

Communication quality influence: frequent call drops, failedas called side for MS, or consume too much electricity.

Alarm on Access Faults

Table 5 shows alarm on access faults.

TA B L E 5 - A L A R M O N A CCESS FA UL T S


Some alarms related withaccess

198001792 Level 2 alarm on lostSDH/SONET signal


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198001793 Level 2 alarm on lostSDH/SONET frame

198005639 Level 2 alarm on high BERat optical interface

198000512 Level 2 alarm on lost trunkframe

198066000 level 2 alarm ondisconnected Abis link

198087248 Level 3 alarm ondisconnected LAPD link between carrierand BSC

198087336 level 2 alarm ondisconnected LAPD communication link

Access Fault Category

Access faults can be divided into the following categories:

Fault caused by frequent location update:

Too much electricity consumed or difficult connection due tofrequent location update.

Faults of service failure:

MS can't access into the network; MS accessed but failed toconversation; MS called failure.

QoS fault:

Call failure for high priority subscriber; false MS power-off.

Troubleshooting Guide aboutAccess Faults

Frequent Location Update

After MS is powered on, it can access the network and makecalls, but occasionally, MS can not be connected when called,and the MS battery runs out quickly.

Usually, MS location update is performed in the following cases:

When MS is powered on, it finds the network and performs alocation update.

Location update upon MS power-on is necessary.

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MS performs location update periodically.

If the period of periodical location update is set too short, thelocation update will become more frequent.

MS is moved to a new location areaIf the location area is planned to be too small, MS will frequentlycross location areas when it moves, and the location update willbecome more frequent accordingly.

More location updates consume MS battery quickly. Meanwhile,MS is unable to respond to paging message when performing thelocation update, thus the connection failure probability increases.

Moreover, too many location updates may affect the BSC loadand increase the load of A-interface signaling link.

Perform the following steps to check A-interface signaling totroubleshoot the fault:

1. If the location update reason is Normal Location Updating,then it is usually because that MS frequently crosses locationareas. It needs to determine whether location areas are toosmall, and plan the location areas again if necessary.

2. If the location update reason is IMSI Attach, then it is usuallybecause MS is frequently powered on/off. If there are toomany location updates, the cause may also be that MS cannot receive messages from BTS due to poor radio coverageand the low level. In this case, it needs to adjust the radiocoverage range, and if possible, increase the minimumaccess level of the cell.

3. If the location update reason is Periodical location update,then the location update period may be too short. In thiscase, cooperate with MSC to modify the value of timer T3212.

It needs to record the A-interface signaling. Determine whetherlocation update is too frequent by comparing history data withdata of other offices.

Failure of MS Accessing the Network

MS often fails to access the network, and call drop often occurs.MS battery runs out quickly, with a short standby time.

1. MS will be disconnected from the network when it finds thecurrent cell level is lower than the minimum cell access levelin the system message, and will start cell selection to searchfor the network again. If MS fails to find the network, thenthe fault symptom is failure of MS accessing the network; ifMS finds the network quickly, then the fault symptom is thatMS temporarily disconnects from the network.

If the cell reselection offset parameters are setunreasonably, MS may reselect a poor cell, causing cell

occupation failure.

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The network color code allowed by the cell or that of theadjacent cell is configured incorrectly, which causes MS failsto reselect the cell.

2. The cell configuration of MSC is incomplete, causing

subscribers in some cells fail to access the network. If any ofthese cells is reselected, MS will be disconnected from thenetwork.

The CBA and CBQ parameters of cell are incorrectlyconfigured, causing occupation becomes difficult.

Poor signals during the call will cause poor voice quality andcall drop.

When the BSC processor is overload or RACH is overload, theflow control will start, which consequently prevents some MSfrom accessing the network.

1. Check whether system messages CBA and CBQ are correct,and check system messages to see whether any subscriber isbarred from network access due to flow control.

2. Check whether the minimum access level of the cell is settoo large.

3. Check whether the jitter of BTS output power is too large. Ifit is too large, check whether the PA output is normal.

4. Check whether antenna is normal to see whether signals inthe area are too weak.

5. Check whether BTS has any abnormal alarm such as LapD

disconnection alarm.6. Check whether any interference exists.

7. Check whether the parameter C2 is set reasonably, andwhether the parameter CRO of adjacent cell is set too large.

8. Check the cell settings of MSC.

9. Check CBA and CBQ parameter settings of the cell.

It needs to determine the fault cause based on alarm messages,a drive test in the area is also required.

Network Busy Prompted at Call

There is no prompting tone when dialing, and the MS screendisplays such information as network failure and network busy.

Such a fault is usually caused by resource congestion.

The call will fail in the following cases: When congestion occursin A-interface circuit; Assigned circuit attribute does not matchthe radio channel attribute; Request for TCH resource fails.

TCH is not allocated successfully in such cases, thus noprompting tone can be heard when dialing.

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1. Check whether signaling of the Abis interface and A-interfaceis abnormal and whether the signaling flow is complete.

2. If the signaling flow is incomplete and the call is notconnected, then check whether there is any available TCH. If

the cell has serious congestion, then:

Perform capacity expansion to add TRX.

Enable service functions such as queuing and directedretry.

Adjust the handover relationship and thresholds to makeMS difficult to handover in but easy to handover out.

Modify the reselection parameters, such as the minimumaccess level and CRO, which affect the C1/C2, to reducethe number of subscribers residing in the congestion cell.

Adjust the antenna direction to reduce the coveragerange of the cell.

3. If there are too many radio interface assignment failures, i.e.a high percentage of Assignment Failure in Abis signalingtracing, then:

Check whether there is any interference that causes radiointerface assignment failure.

Check whether the carrier output power of TCH is lowerthan that of BCCH. In this case, check the connectionbetween PA and BTS.

4. Check whether the A-interface circuit is blocked, and whether

its status is different from that of MSC circuit.

For such faults, it is necessary to record signaling of the Abisinterface and A-interface, from which to find out the fault causeand decide the fault location, and thus to solve the problem.

Call Returned Without Prompt

When MS dialing a phone number, the MS screen quickly returnsto the idle state without any prompt, but sometimes beepsound can be heard.

Usually, it is due to SDCCH assignment failure.

MSC rejects the connection.

Check whether the Abis interface signaling is abnormal.

Check whether the immediate assignment of SDCCH iscompleted: whether the Abis interface has SDCCHestablishment indication.

If the immediate assignment of SDCCH is not completed, thencheck whether there is any available SDCCH. If there is, thencheck the paging parameter setting and the CCCH setting, and

reconfigure the cell data if necessary.

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If the immediate assignment is completed, then check whetherthe Abis interface has received the Assignment Completemessage.

For such faults, it is necessary to record signaling of the Abis

interface and A-interface, from which to find out the fault causeand decide the fault location, and thus to solve the problem.

In addition, it is required to view the congestion condition ofSDCCH in the report.

Call Connection Time Long

When dialing a phone number, it takes a long time for the call tobe connected.

The call can be connected but sometimes a long time is neededto connect the call. The cause is that there is no available TCHresource during the call. To avoid the call failure, either makesubscribers wait for the resource in queue or implement directedretry and request resources from the adjacent cell.

Check whether the queuing function and directed retry functionare enabled.

Check the report to see whether any queuing or directed retryoccurs.

Record signaling of the Abis interface and observe the wholeassignment process to find out the cause of the long connection

time.

For such faults, analysis should be made based on signaling. Donot diagnose easily to be system fault.

Called Party Not in Service Area

When dialing a phone number, the system prompts that thecalled party is not in the service area.

The network coverage is poor and the called party is temporarily

disconnected from the network, but the periodical locationupdate time is not due yet, thus MSC/VLR does not update theMS status.

The paging channel is overloaded, thus the called party does notreceive the paging message.

The called party is engaged in services such as location updateand cell reselection and does not respond to the paging message.

The signal is poor, thus the access fails even the called partyresponds to the paging message.

Check whether cell reselection of MS occurs too frequently by a

drive test. If the reselection is too frequent, adjust the C2

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parameters to increase the penalty time and temporary offsetlevel.

Check whether CRO is set too large that attracts many edgesubscribers, which causes low level and paging response failure.

For example, in a dual-frequency network, CRO of the 1800 Mcell has set too large.

Check signaling tracing of the Abis interface to see whetherthere is any PCH overloaded. If there is, modify the CCCHconfiguration: for example, increase the multiframe number ofthe paging channel.

Check whether the MS status in MSC/VLR then is normal.

Perform a dialing test to find out the details of no response topaging.

False MS Power-off

A MS is called in its normal power-on state, but the calling partyhears the recorded prompt that the subscriber is power-off.

The fault cause is that the called MS state in MSC/VLR is IMSIdetached, which is due to the following two cases:

MS is power-off and sends the IMSI detached message tothe network;

MS has been in the no-signal coverage area for a long time.

If the periodical location update is not implemented withinthe specified duration (the implicit power-off duration),MSC/VLR will set the MS state as implicit power-off state andwill not page the MS.

The second case involves two timers: the radio-side T3212 (MSperiodical location update interval) and MSC/VLR-side implicitpower-off timer. The latter should be larger than the former,otherwise, the MSC/VLR-side implicit power-off timer will betimeout due to unable to receive the periodical location updatemessage in time, and the fault mentioned above will appear.

Check settings of the timer T3212 and the implicit power-offtimer. The latter should be larger than T3212 but can not be toolarge. Set the timers according to experience in different areas:sometimes T3212 is set to be 120 minutes and the implicitpower-off timer is set to be 150 minutes.

None

Emergency Call Failure

Call fails when MS calls an emergency phone number, but such afault does not occur when MS calls a non-emergency phone

number.

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If the cell parameter Emergency call allowed is not enabled, thenthe emergency-number call will fail.

For the emergency-number call, MSC might connect it to aspecial service console or directly play the recorded prompt.

Thus it is necessary to check MSC data configuration.

Check whether the cell parameter Emergency call allowed isenabled.

Check MSC data configuration.

None

High Priority Subscriber Access

During service-busy hour, call fails even for a high prioritysubscriber, which does not reflect the priority occupation ofresources.

The high priority subscriber refers to a subscriber whose priorityparameter value is comparatively small in the MSC assignmentmessage. BSC provides many ways for the high prioritysubscriber to occupy resource first, which includes reserving afew TCH/F for high priority subscribers, and making the lowpriority subscriber handover to adjacent cell or disconnect thelow priority subscriber to obtain channel resource in the case ofchannel congestion. The fault that call fails even for a highpriority subscriber indicates the above measures are not taken

effectively.Configure a certain number of reserved channels for high prioritysubscribers in the cell, and set the subscriber priority thresholdof using the reserved channels.

Enable the cell parameters of allowing forced handover andallowing forced disconnection.

It should be paid attention to the negative influence on lowpriority subscribers caused by forced disconnection.

Set the parameters according to actual requirements. Ifreserved channel are configured, monitor the reserved channeloccupation through performance measurement to avoid resourcewaste.

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Alarm Cases on Access

FaultsCall Disconnection due to DifferentVoice Encryption Mode at CoreNetwork and Wireless Side

After successful cutover with core network MSC, it is found thatcall is disconnected on dialing test.

By signaling trace SCCP protocol, it is found that unmatchedencryption algorithm is prompted in connection error.

We verify and confirm with core network side that A5/1 voiceencryption algorithm is opened and default iBSC parameters areclosed.

After modifying and using A5/1 encryption, the call is restored.

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C h a p t e r 5

Handover Faults


handling handover faults.

Overview of Handover Faults

Related knowledge

Handover faults include handover call drop, handover failure,

and unable to handover.

Handover performance is an important index that influences thenetwork quality.

Figure 5 shows the external handover flow.


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F I G URE 5 - EX T E R N A L HA ND O VE R

The figure above shows the handover flow between two BSCsunder the same MSC. The handover succeeds if the destinationBSS receives the HANDOVER COMPLETE message, otherwise,the handover fails.

Influence on service by handoverfaults

Minor handover fault may cause degraded call quality, and majorhandover fault may cause call drops.

Alarm on Handover Faults

Table 6 shows alarm on handover faults.

TA B L E 6 - A L A R M O N HA ND O VE R FA U L T S


198026624 level 2 alarm on DSPoverhead overload

198087380 level 2 alarm on carrierblocked

Some alarms that maycause call drops

198087385 Level 2 alarm on unavailablefrequency


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Chapter 5 - Handover Faults



198087422 level 2 alarm on critical SWRalarm

198087432 lelvel 2 alarm on loss ofdiversity

198087433 level 2 alarm onmismatched cable at antenna

198066000 level 2 alarm ondisconnected Abis link

198087336 level 2 alarm ondisconnected LAPD communication link

198087363 level 3 alarm ondisconnected link at service plane (CSservice)

198087243 level 2 alarm on inconsistentcell parameter configuration

Alarm on Handover Faults

Handover faults can be divided into the following two types:

Minor: too slow or too much handover fault causes degradedtalk quality.

Critical: handover fault causes call drops.

Troubleshooting Guide aboutHandover Faults

Handover Failure Ratio High

The report statistics indicates high handover failure ratio.

The handover failure of radio interface is related to the radioquality of the handover-in cell, for example, the handover-in cellhas severe interference, hardware fault, or failure of obtainingthe timing advance.

Find out towards which cell the handover failure ratio is highthrough handover observation or adjacent cell handovermeasurement, and then appropriately increase the handoverthreshold towards that cell according to the physical landforms.

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Check whether the handover-in cell with handover failure hashardware faults in some carriers, abnormal power, or highassignment failure ratio.

Check whether the handover-in cell with handover failure has

interference, and whether there is any same frequency/samecolor code.

Check whether NY1 and T3105 of the handover-in cell withhandover failure are set too small, which causes handoverfailure.

Check whether the handover parameters are reasonable, andfine-tune the parameters if necessary.

Check whether the adjacent relation is correct, deleteunnecessary adjacent cells, and add missing adjacent cells.

Observe whether the uplink/downlink levels of the problem cell

are balanced. Unbalanced uplink/downlink levels may also causehandover failure.

Analyze the fault cause by creating measurement jobs related tohandover, and adjust relevant handover parameters.

Failure of Handover to the Best Cell

During the drive test, it is found that MS is not handover to thebest adjacent cell

The adjacent relation is not configured correctly. Adjacentrelation configuration missing or incorrect configuration ofadjacent cell parameters will cause that handover wont takeplace.

The handover parameters of different adjacent cells may differ,which may cause the change of handover direction.

The best adjacent cell is very busy at the moment with noavailable channel, thus no attempt will be made to hand over tothe best adjacent cell.

The best adjacent cell has poor radio quality, and handoverattempt has been made but fails, thus penalty is made on the

adjacent cell by system, which causes failure of handovertowards the adjacent cell.

During MS handover, the background is performingaddition/deletion action on relevant adjacent cells.

Check all configuration data of the adjacent cell, especially whenit is an external cell. If the parameters of the cell, such asfrequency point, MCC, and MNC, have been changed, but thoseof the adjacent cell have not, then no handover will take place.

Check whether Network Color Code (NCC) of the adjacent cell isconsistent with that allowed by the system. If NCC of the

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adjacent cell is not within the allowed range of the cell, then MSwill not attempt to handover to the adjacent cell.

Check the handover parameters to see whether the threshold forhandover to the adjacent cell is too high, which causes handover

difficulty.

Check whether the adjacent cell is in busy hour at the momentand whether no channels are available. The system will notattempt to handover to the adjacent cell if no available channelsare found.

Check the signaling to see whether handover is attemptedtowards the adjacent cell but the attempt fails. If handover hasfailed, then penalty will be made on the adjacent cell, thushandover will bypass the adjacent cell.

View the whole process of handover through drive test. Recordthe handover-out cell and all its adjacent cells, and then checkthe parameter configuration and channel congestion informationof adjacent cells one by one in ISMG.

It is very important to check data configuration of adjacent cells,since many handover failures result from incorrect dataconfiguration.

Handover Speed too Slow

The detected signal level of the adjacent cell is higher than that

of the current cell, but handover takes pace some time laterrather than immediately.

Usually, slow handover is caused by improper handoverparameters configuration:

1. Handover pre-processing parameters

Handover pre-processing refers to the processing ofmeasurement report by BTS. BTS averages themeasurement data of MS and those of its own, and thenreports them to BSC at a low frequency. That themeasurement is reported at a low frequency helps reducethe load of Abis interface link, but this also results in less

timely handover control.

2. Handover window value and weight value

The two parameters are used for average processing of themeasurement reports.

To avoid any abrupt change of measurement values causedby complicated radio transmission, BSC does not use theoriginal measurement data in handover decision; instead,BSC use weighted average of the measurement data. Thelarger the window value, the more measure reports used inaveraging. When such weighted average of measurementdata is used for handover decision, the actual change of the

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level is concealed to some extent, which will cause slowhandover.

3. N value and P value for handover decision

Handover is triggered only when P measurement reportsamong the N measurement reports (average) satisfy thehandover conditions. If values of N and P are too large, thehandover conditions become difficult to be satisfied, thusinfluencing the handover speed.

4. Minimum handover interval

The parameter refers to the minimum interval between twohandovers. If the value is large and a handover has justoccurred, then no handover will be implemented within theinterval, thus the handover speed is influenced.

In addition, intra-cell handover has a higher priority over

other handovers. If the intra-cell handover condition issatisfied all the times, then MS will always implement intra-cell handover instead of inter-cell handover, which will causethe speed of handover towards the adjacent cell very slow.

Disable the pre-processing of the problem cell, or reduce thenumber of the pre-processed reports.

Decrease the handover window value.

Adjust the N value and P value for handover decision, forexample, decrease the P value.

Reduce the minimum handover interval.

If fast level fading without handover is found through the drivetest, then enable the function of handover at fast level fading.

Adjust the handover threshold to make the handover conditionsto be more easily satisfied.

If MS always implements intra-cell handover, then appropriatelyadjust the intra-cell handover threshold.

Make adjustment according to actual conditions to solve the slowhandover. In fact, slow handover has little influence on theservices as long as it does not affect voice quality or cause calldrop. Thus it is not a fault and needs no handling. On the otherhand, modifying handover parameters to make handover speedquicker will cause handover becoming too frequent and result inincorrect handover.

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Alarm Cases on Handover

FaultsSlow Inter-cell Handover

At the phase of engineering optimization in certain test area,network optimization personnel reflects too slow inter-cell duringDT test, about 6s in average.

After testing, when MS level is reduced about -90dBm in originalcell, the handover is still not finished, so call quality is affected.Handover parameters shall be adjusted.

By adjusting handover pre-processing, PN value, andHoMinInterval parameters, handover rate is increased.

Abnormal Handover with ExternalCells Because Handover Data is notAdded in LAC Cell at MSC Side

After adjacent cell is added for the base station from other

manufacturers, handover is abnormal.

After signaling trace, it is found that there is handover requesttransmitted, but without relevant signaling returned. Aftercommunicating with switching center, it is found that handoverbetween LAC cell of iBSC and LAC cell of BSC at switching side.

ZTE site is at same region as the equipment made by othermanufacturers, but the assigned LAC number is different.

After adding bi-directional handover data, handover is restored.

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C h a p t e r

6

Congestion Faults


handling congestion faults.

Overview of CongestionFaults

Related knowledge

Congestion occurs in the case of no available resource inresource allocation.

Congestion is divided into two types: congestion of A-interfacecircuit resource and congestion of Um interface radio resource.

Influence on Service by CongestionFaults

Unavailable ground resource or wireless resource may directlycause service failed due to failed MS access.

Alarm on Congestion Faults

Table 7 shows alarm on congestion faults.

TA B L E 7 - A L A R M O N CO NG EST I O N FA U L T S



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198066008 level 2 alarm on overloadtransmitting at MTP2 link

198066013 level 2 alarm on congestion atMTP3 link

198066008 level 2 alarm on overloadtransmitting at MTP2 link

Common congestion alarms

198066006 level 3 alarm on congestion atbroadband link

Congestion Fault Category

Based on source, congestion faults can be categorized into:

Ground resource congestion: such as interface A;

Wireless resource congestion: such as SDCCH channel orTCH channel.

Troubleshooting Guide aboutCongestion Faults

SDCCH Congestion

The report shows that congestion occurs on SDCCH, calls andshort message service are not running normally at the moment.

The location areas are too small, thus there are too manylocation updates, which causes SDCCH congestion.

Burst traffic (short messages for example) causes SDCCHcongestion.

Hardware fault of the carrier causes SDCCH congestion.

Interference on the radio interface causes congestion. Forexample, if the TCH signal coverage with the same frequencyand same color code as those of BCCH exists near the cell, t

Sjzl20083718-ZXG10 IBSC (V6.10) Maintenance Manual (Troubleshooting)

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Transcript of Sjzl20083718-ZXG10 IBSC (V6.10) Maintenance Manual (Troubleshooting)