ZXG10 B8018 Maintenance Troubleshooting

ZXG10 B8018In-Door Base Transceiver Station

Maintenance Manual(Troubleshooting)

Version 1.00

ZTE CORPORATION ZTE Plaza, Keji Road South, Hi-Tech Industrial Park, Nanshan District, Shenzhen, P. R. China 518057 Tel: (86) 755 26771900 800-9830-9830 Fax: (86) 755 26772236 URL: http://support.zte.com.cn E-mail: [email protected]

LEGAL INFORMATION Copyright © 2006 ZTE CORPORATION. The contents of this document are protected by copyright laws and international treaties. Any reproduction or distribution of this document or any portion of this document, in any form by any means, without the prior written consent of ZTE CORPORATION is prohibited. Additionally, the contents of this document are protected by contractual confidentiality obligations. All company, brand and product names are trade or service marks, or registered trade or service marks, of ZTE CORPORATION 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 the use 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 ZTE CORPORATION and its licensee, the user of this document shall not acquire any license to the subject matter herein. The contents of this document and all policies of ZTE CORPORATION, including without limitation policies related to support or training are subject to change without notice.

Revision History

Date Revision No. Serial No. Reason for Revision

12/21/2006 R1.0 sjzl20062591 First edition

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Please fax to: (86) 755-26772236; or mail to Documentation R&D Department, ZTE CORPORATION, ZTE Plaza, A Wing, Keji Road South, Hi-Tech Industrial Park, Shenzhen, P. R. China 518057.

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Document Name ZXG10 B8018 (V1.00) In-Door Base Transceiver Station Maintenance Manual (Troubleshooting)

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Contents

About this Manual........................................................... xi

Purpose.............................................................................. xi Intended Audience ............................................................... xi Prerequisite Skill and Knowledge ............................................ xi What is in This Manual.......................................................... xi Related Documentation........................................................ xii Conventions....................................................................... xii How to Get in Touch............................................................xiii

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

Maintenance Safety .........................................................1

Safety Instructions................................................................1 Safety Signs.........................................................................1 Precautions ..........................................................................2

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

Maintenance Overview ....................................................5

Troubleshooting Procedure ...............................................5 Fault Information Collection....................................................5 Fault Analysis .......................................................................6 Fault Locating.......................................................................6 Fault Removal ......................................................................6

Common Fault Analysis and Locating Methods.....................7 Alarms and Operation Log Check.............................................7 LED Status Analysis...............................................................7 Performance Analysis ............................................................7 Analysis with Instruments and Meters ......................................7 Plug/Unplug .........................................................................8 Comparison and replacement..................................................8 Isolation ..............................................................................8 Self -Test.............................................................................8

ZTE Customer Support...........................................................8

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

Transmission Faults.........................................................9

OVERVIEW ...........................................................................9 Troubleshooting ....................................................................9 All LAPD links of BTS Are Broken ...........................................10 LAPD Link Establishment Failure between Cascaded Sites..........11 Poor Conversation Quality with High Transmission BER .............11 OAM Link of CMB is Broken ...................................................12 Individual DTRU LAPD Links Establishment Failure....................12 LAPD Links of Many BTS Sites are Broken ...............................13 Transmission Link Break.......................................................13 Abnormal Transmission Link .................................................14 OAM Link of the BTS Site is Broken ........................................14 LAPD Links of Some Carriers of a BTS Site are Broken ..............15 LAPD Links of Carriers of Many BTS Sites are Transiently Broken16

Chapter 4........................................................................19

Antenna Feeder Faults...................................................19

Overview ...........................................................................19 Troubleshooting ..................................................................20 VSWR Faults.......................................................................21 Coverage Shrinkage ............................................................22 VSWR Alarm of the Combiner................................................22 Poor Uplink Quality ..............................................................23 Poor Downlink Quality..........................................................23 VSWR Alarm of the Power Amplifier (PA) ................................24 Tower Mount Amplifier (TMA) Power Alarm..............................25 TMA Alarm .........................................................................25 LNA Alarm..........................................................................26

Chapter 5........................................................................29

Voice Faults....................................................................29

Troubleshooting ..................................................................29 Voice Abnormalities Caused by RF Faults ................................30 Voice Abnormalities Caused by Configuration Faults .................30 One-way conversation .........................................................30 Two-way Blocking ...............................................................31

Poor Conversation Quality .................................................... 32 Crosstalk ........................................................................... 33 Poor Conversation Quality of a BTS........................................ 34 Noises in Outgoing Toll Call .................................................. 34 Unstable MS Signals in the Idle State..................................... 34 Unstable MS Signal in the Busy State..................................... 35 Echo in MS Conversation...................................................... 36

Typical Case................................................................. 36 Fault Information Collection.................................................. 37 Fault Analysis ..................................................................... 37 Troubleshooting.................................................................. 40 Summary .......................................................................... 42

Chapter 6........................................................................45

Loading Faults................................................................45

Software Version Cannot be Imported.................................... 45 Loading Failure ................................................................... 45 CMB/DTPB Board Unable to Start .......................................... 46 The Board Software cannot be Imported ................................ 46 Repeated Loading of CMB..................................................... 46 Repeated Loading of DTRU ................................................... 47 LAPD Link Establishment Failure after Software Loading ........... 47 FU LAPD and HDLC Disconnection Alarms ............................... 48

Chapter 7........................................................................49

Clock Faults....................................................................49

Overview ..................................................................... 49

Symptom........................................................................... 49 Notification Messages and Alarms.......................................... 49 Fault Analysis ..................................................................... 50

Troubleshooting ............................................................ 50 Clock Module Reset/Restart .................................................. 50 Carrier Clock Faults ............................................................. 50 Classified Faults.................................................................. 51 Clock alarms ...................................................................... 51 L3 Software Not Responding................................................. 52 PLL Lock Loss Alarm Frequently Occurs/Recovers .................... 52 Metal Noise during Conversation ........................................... 52 Call Drop during Handover ................................................... 53

High Handover Failure Ratio..................................................53

Chapter 8........................................................................55

Service Faults.................................................................55

Overview ..................................................................... 55 Symptoms .........................................................................55

Troubleshooting............................................................ 56 BTS Call Test ......................................................................56 Performance Analysis...........................................................56 Signaling Procedure Analysis.................................................57 Poor Signal Quality or Signal Fluctuation.................................57 Frequent Call Drops due to Hard Handover..............................57 No Traffic in the Cell or Sudden Rise of Call Drop Ratio .............58 MS indicates Signal Fluctuation or No Signal............................58 System Prompts Failure to Connect........................................59 Strong Signals but Unable to Make a Call ................................59 Handover Failure.................................................................60 Occupation of Carrier for Short Time ......................................60 The Carrier Cannot be Occupied ............................................60 Long SDCCH Occupation Time...............................................62 Sudden Rise of Call Drop Ratio ..............................................62 BTS Overload Message.........................................................63 Low TCH Assignment Success Ratio .......................................63

Chapter 9........................................................................65

Board Faults ...................................................................65

Trunk Node Alarm ...............................................................65 Backplane Fault ..................................................................65 Abnormality of Standby CMB Board........................................66 HW Link Interruption for a Long Time.....................................66 PA VSWR Alarm ..................................................................66 Major Clock Alarm on Active and Standby CMBs.......................67

Appendix A.....................................................................69

CBA Parameter...............................................................69

CBA Parameter Modification ..................................................69

Appendix B .....................................................................71

DTMF Signal Tone ..........................................................71

DTMF Signal Tone Generation ............................................... 71

Appendix C .....................................................................73

Abbreviations.................................................................73

Appendix D .....................................................................75

Figures............................................................................75

Tables.............................................................................77

Index..............................................................................79


Confidential and Proprietary Information of ZTE CORPORATION xi

About this Manual

Purpose

This Manual provides procedures and guidelines that support the troubleshooting of ZXG10 B8018 Base Transceiver Station.

Intended Audience

This document is intended for engineers and technicians who perform troubleshooting activities on the ZXG10 B8018 Base Transceiver Station.

Prerequisite Skill and Knowledge

To use this document effectively, users should have a general understanding of wireless telecommunications technology. Familiarity with the following is helpful:

ZXG10 system and its various components

Local troubleshooting procedures

What is in This Manual

This Manual contains the following chapters:

T AB L E 1 - C H AP T E R S U M M AR Y

Chapter Summary

Chapter 1 Maintenance Safety

Introduces the safety measures that are taken during the troubleshooting process

Chapter 2 Maintenance Overview

Introduces the common troubleshooting methods

Chapter 3 Transmission Faults

Introduces the BTS faults caused due to transmission Failure

Chapter 4 Antenna Feeder Faults

Introduces the faults caused due to antenna feeder problems

ZXG10 B8018(V1.00)In-Door Base Transceiver Station Maintenance Manual(Troubleshooting)

xii Confidential and Proprietary Information of ZTE CORPORATION

Chapter Summary

Chapter 5 Voice Faults Introduces the analysis and troubleshooting procedures of voice faults

Chapter 6 Loading Faults

Analyzes the faults that may occur during software loading process

Chapter 7 Clock Faults Analyses the clock synchronization problems

Chapter 8 Service Faults

Analyzes faults such as weak signal, call drop, poor voice quality and handover faults

Chapter 9 Board Faults Introduces the troubleshooting procedures to solve board faults

Appendix A CBA Parameter Modification

Introduces the methods for modifying the CBA parameter

Appendix B DTMF Signal Tone Generation

Introduces principles of DTMF signal tone generation

Appendix c, Abbreviations

Lists English abbreviations used in this manual

Appendix D, Figures Lists all the figures used in this manual

Appendix E, Tables Lists all the tables used in this manual

Index Index for reference to different topics

Related Documentation

The following documentation is related to this manual:

ZXG10 B8018 Base Transceiver Station Documentation Guide

ZXG10 B8018 Base Transceiver Station Technical Manual

ZXG10 B8018 Base Transceiver Station Installation Manual

ZXG10 B8018 Base Transceiver Station Maintenance Manual (Routine Maintenance)

ZXG10 B8018 Base Transceiver Station Maintenance Manual (Troubleshooting)

Conventions

ZTE documents employ the following typographical conventions.

T AB L E 2 - TY P O G R AP H I C AL C O N V E N T I O N S

Typeface Meaning

Italics References to other Manuals and documents.

Typographical Conventions

About this manual

Confidential and Proprietary Information of ZTE CORPORATION xiii

Typeface Meaning

“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 screens and company name.

Constant width Text that you type, program code, files and directory names, and function names.

[ ] Optional parameters.

Mandatory parameters.

| Select one of the parameters that are delimited by it.

Note: Provides additional information about a certain topic.

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

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

T AB L E 3 - M O U S E OP E R AT I O N C O N V E N T I O N S

Typeface Meaning

Click Refers to clicking the primary mouse button (usually the 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 and moving the mouse.

How to Get in Touch

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

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

ZTE welcomes your comments and suggestions on the quality and usefulness of this document. For further questions,

Mouse Operation

Conventions

Customer Support

Documentation Support

ZXG10 B8018(V1.00)In-Door Base Transceiver Station Maintenance Manual(Troubleshooting)

xiv Confidential and Proprietary Information of ZTE CORPORATION

comments, or suggestions on the documentation, you can contact us by e-mail at [email protected]; or you can fax your comments and suggestions to (86) 755 26772236. You can also browse our website at http://support.zte.com.cn, which contains various interesting subjects like documentation, knowledge base, forum and service request.

Confidential and Proprietary Information of ZTE CORPORATION 1

C h a p t e r 1

Maintenance Safety

This chapter includes the following topics:

Safety Instructions

Safety Signs

Precautions

Safety Instructions

Only trained professionals must operate and maintain the BTS equipment.

Follow the local safety codes when operating and maintaining the BTS equipment.

Safety precautions used in this manual are only supplementary to the local safety codes.

ZTE shall not bear any liabilities incurred by violation of the universal safety regulations or violation of safety standards for designing, manufacturing and usage of the equipment.

Safety Signs

The general safety signs used in this manual are listed in Table 4.

T AB L E 4 - S AF E T Y S I G N S

Safety Signs Meaning

Danger: Indicates an imminently hazardous situation, which if not avoided, will result in death or serious injury. This signal word should be limited to only extreme situations

ZXG10 B8018 (V1.00）In-Door Base Transceiver Station Maintenance Manual (Troubleshooting)

2 Confidential and Proprietary Information of ZTE CORPORATION

Warning: Indicates a potentially hazardous situation, which if not avoided, could result in death or serious injury.

Caution: Indicates a potentially hazardous situation, which if not avoided, could result in minor or moderate injury. It may also be used to alert against unsafe practices.

Erosion: Beware of erosion.

Electric Shock: There is a risk of electric shock

Electrostatic: The device may be sensitive to static electricity.

Microwave: Beware of strong electromagnetic field.

Laser: Beware of strong laser beam.

No flammables: No flammables can be stored.

No touching: Do not touch.

No smoking: Smoking is forbidden.

Precautions

Strictly follow the Standard Operation Procedures (SOP) of the equipment.

Wear antistatic wrist strap when touching any hardware of the equipment.

Never perform operations such as plugging/unplugging, resetting, starting or switching, loading/modifying equipment data without prior permission.

Equipment Operations

Chapter 1 - Maintenance Safety


Wear an antistatic wrist strap when touching a board.

Prepare working staff and boards in advance before plugging/unplugging or replacing any important board.

Check the spare parts regularly to ensure that the common spare parts are properly stocked, intact and free from moisture and mold.

Keep the spare parts separately from the faulty parts replaced during maintenance, mark them separately and store them in antistatic bags.

Perform operations such as data synchronization and data modification during low-traffic hours (such as midnight).

Perform operations that take more CPU time during low-traffic hours (such as midnight).

Backup important data and record the backup before data modification.

Periodically backup all data for future use.

Periodically observe all databases, especially the performance measurement and alarm databases (once every two weeks). Delete the old data to avoid disk overflow.

Generally operation rights fall in to three levels:

Super administrator: Has the highest level of rights in the system and can execute all operations.

Advanced operator: Has operation rights such as configuring/modifying data, diagnosis test, performance statistics, alarm query and status query.

Operator: Has operation rights such as alarm query and status query.

Assign only one super administrator for system management.

Super administrator must handle network management and password management tasks.

Periodically change the password used to log on to the server and the client.

Do not change the network settings and the settings of OAM server or client without prior permission.

Use CDs and disks provided by ZTE for installing software for Operation and Maintenance (OAM) server or client.

Do not install and run any program irrelevant with operation and maintenance on the OAM server or client.

Board Operations

Data Maintenance

Operations Rights

Management

Virus Protection for

the System



Install copyrighted antivirus software on every client and the servers and enable the real-time virus detection function. Timely update the virus definitions (once every week).

Detect the problems and faults and report major problems to the relevant officials and the local ZTE office.

Record the detailed troubleshooting procedures.

Fault Report


C h a p t e r 2

Maintenance Overview

This chapter introduces the common troubleshooting methods.

Troubleshooting Procedure

The troubleshooting procedure consists of four phases:

Fault information collection

Fault analysis

Fault Locating

Fault removal

Fault Information Collection

Collect fault information from the following:

Customers fault complaints

Exceptions found during routine maintenance or inspection

Alarm messages and notification messages in the OMC client

LED status of boards



Fault Analysis

After collecting information about the faults, analyze the possible fault causes.

Fault can be categorized as follows:

Transmission faults

Antenna feeder faults

Voice faults

Loading faults

Clock faults

Service faults

Board faults

This manual analyzes the faults based on the above fault types and introduces the troubleshooting methods.

Fault Locating

After analyzing the fault causes, use various troubleshooting methods to rule out the impossible fault causes and locate the exact fault cause.

For detailed information regarding fault analysis methods, refer to Common Fault Analysis and Locating Methods

Fault Removal

After locating the fault, take appropriate steps to remove the fault and recover normal operation of the system.

Chapter 2 - Maintenance Overview


Common Fault Analysis and Locating Methods Alarms and Operation Log Check

The first method of fault locating is checking the alarms and the operation log in iOMCR.

Alarm management interfaces in iOMCR helps to observe and analyze alarm messages reported by network elements, such as current alarms, history alarms and common notification messages. Operation log browsing interface in iOMCR helps in tracing modifications on system parameters, locating the relevant terminal and detecting the personal faults.

LED Status Analysis

LED Status Analysis is a method often used to locate a fault.

Be familiar with the status and meanings of all LEDs in order to locate the fault exactly.

Performance Analysis

Performance analysis is done through performance management interface in the iOMCR.

Analyze performance measurement tasks, performance reports and BSS performance indices, detect load distribution in the network and adjust network parameters to improve the network performance.

Signaling trace is done through signaling trace interface of iOMCR to locate signaling faults.

Analysis with Instruments and Meters

Use auxiliary instruments such as test MS, signaling analyzer and BER analyzer to analyze, locate and remove faults.



Plug/Unplug

Upon detecting fault in a board, plug or unplug the board and external connectors, in order to remove the faults caused by poor contact.

In addition, remove the faults caused by poor contacts by pressing the cable connectors.

Comparison and replacement

Compare a possible faulty board with a normal board at the similar position in the system and find the faulty board.

Also, replace a faulty board with a spare board or another normally working board of the same type and check whether the fault disappears after replacement.

Caution: During fault analysis, strictly follow the relevant requirements for board plugging/unplugging.

Isolation

Isolate the faulty part from the other relevant board or rack, and decide whether the fault cause is due to mutual influence between them.

Self -Test

Judge a fault by observing the flashing of LEDs on the board panel after the system or board is re-powered on.

ZTE Customer Support

Incase of further queries, contact ZTE Customer Support via telephone, fax or e-mail.

Hotline: 86-755-26770800, 86-800-8301118, 86-400-8301118

Fax: 86-755-26770801

Website: http://support.zte.com.cn

Customer service e-mail: [email protected]


C h a p t e r 3

Transmission Faults

This chapter analyzes the BTS faults caused due to transmission failure.

OVERVIEW

Transmission faults may create the following alarms:

Broken LAPD link of a BTS site

Broken OAM link of a BTS site

E1 interface frame out of sync

E1 interface code slip notification

Troubleshooting

Transmission faults are mainly caused by the following:

Transmission bit errors

Time slot allocation problems

The basic troubleshooting steps for transmission faults are:

Performing bit error test

Checking E1 time slot (TS) allocation

Bit errors cause system instability and transmission interruption (when BER is over 10-5 ).

The causes for bit errors are as follows:

Bit errors caused by internal mechanisms

Such bit errors are caused by various noise sources, phase jitters, multiplexers, inter connected equipments or switches, or inter-symbol interference.

Transmission Bit Errors



These bit errors affect the long-term bit error performance of the system.

Bit errors caused by interferences

These bit errors are caused due to electromagnetic interference, transient power interference and equipment failure. These bit errors are in bursts and bulky and they occur suddenly.

These bit errors affect the short-term bit error performance of the system.

TS allocation problem can cause BTS LAPD link interruption under normal transmission conditions (there is no transmission alarm).

The possible causes for TS allocation problem are as follows:

Inconsistent configured data between the BSC and the BTS.

The inconsistency between the background configuration data and the settings of DIP switches in the BTS causes LAPD link failure.

Cross connection of transmit and receive ends of a transmission line.

The uplink and downlink communications fails and BTS cannot start normally when there is cross connection between transmit and receive ends of a transmission line.

Failure of E1 Timeslot add/drop multiplexer

Working failure of E1 timeslot add/drop multiplexer present in the middle of the transmission path, causes inconsistent TS allocation between the BTS and BSC.

BTS LAPD link fails when the timeslot add/drop multiplexer fails or when its data configuration is incorrect.

All LAPD links of BTS Are Broken

LAPD links of all boards in a BTS are broken

iOMCR displays the site as gray

Site cannot function properly

The fault may be due to the following:

Faulty CMB board

Faulty transmission equipment

Defective backplane connection

Faulty BSC hardware

TS Allocation Problem

Symptoms

Fault Analysis

Chapter 3 - Transmission Faults


Reset the CMB board and check whether the fault is removed.

Conduct self-loop test and check if the physical link between the BTS and BSC is broken.

Check the BSC, transmission equipment and BTS for any fault.

Confirm if the DIP switch setting is correct and matches the configuration data.

LAPD Link Establishment Failure between Cascaded Sites

Lower level site cannot establish a link with the main site.

iOMCR indicates fault in the lower level site.


Mismatch of DIP switch setting with the configured LAPD timeslot.

Incorrect OAM timeslot configuration.

Interchange the upper and lower level relations of the two sites and check whether the problem is solved.

Check the equipment for faults.

Check the DIP switch setting.

Poor Conversation Quality with High Transmission BER

Bit errors

Frame out of sync

Code slip notification

Poor conversation quality in all cells of the site


Faulty CMB board

Incorrect clock reference

Troubleshooting

Symptoms

Fault Analysis

Troubleshooting

Symptoms

Fault Analysis



Check for impedance mismatch between the connections from E1 to EIB.

Measure the clock reference.

Replace the corresponding equipment.

OAM Link of CMB is Broken

Only OAM link of the site is broken while the FU LAPD link is normal.


Interferences

Multiplexing Problems

Software processing problems

Reset the CMB.

Upgrade the software to the latest version.

Individual DTRU LAPD Links Establishment Failure

The LAPD links of all other boards except a DTRU is normal.


Faulty DTRU equipment

Software processing problem

Observe and check for any alarm in DTRU and confirm its normal operation.

Reset the DTRU and observe whether it can recover.

Upgrade the software to the latest version.

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting



LAPD Links of Many BTS Sites are Broken

LAPD links of many BTS sites on the same transmission line or the sites connected to the same BSC board are broken.



Faulty BSC equipment

Confirm the connections of the faulty BTS and check if the equipment related to the BSC has the same problem.

Transmission Link Break

BSC

The TIC or SMB board related to the particular BTS reports ‘all 1s or all 0s’ alarm.

LED of the corresponding port on the TIC or SMB board is ON.

BTS

SYN LED on the CMB board is red or flashes in red.


Faulty BSC equipment

Faulty BTS equipment

Faulty Transmission equipment

Perform two-way self-loop test to check the normality of SYN LED status and TIC (or SMB) board LED status.

Incase of ambiguity in finding the problematic spot in a line; divide the line between BSC and BTS in to segments. Perform self-loop test to the segments. If ‘all 1s or all 0s’ alarm of the TIC (or SMB) board appears again after a segment is self-looped, that segment must be problematic.

Symptom

Fault Analysis

Troubleshooting

Symptoms

Fault Analysis

Troubleshooting



Abnormal Transmission Link

Discontinuous transmission link


Fault in uplink from BTS site to the BSC.

Fault in down link.

Even though the LAPD link is normal, there are transmission fault alarms like E1 out of frame, E1 code slip notification and CMB out of lock for a long time.

Both sides of the transmission line may be normal but there are BTS LAPD alarms.

Check for proper grounding of equipments like BTS, DDF, BSC and transmission equipment.

Check if the timeslot add/drop multiplexer (if any) works normally.

Check if the DIP switches of the TIC (or SMB) work normally.

Self-loop the E1 line segment by segment starting from the segment near the BSC. If a problem is detected in a segment, replace the connection line or the equipment on this segment.

Check the transmission indices using an E1 transmission tester.

Check if the BIECOM file configuration of the BSC is correct.

Check if the OAM TS configuration is consistent with the DIP switch setting on the CMB board.

Check if the cabling of transmission line conforms to the relevant requirements.

OAM Link of the BTS Site is Broken

OAM link of the BTS site is disconnected

BTS Could not start normally



Incorrect OAM timeslot configuration data

Faulty BTS E1 interface

Symptom

Fault Analysis

Troubleshooting

Symptoms

Fault Analysis



Troubleshoot the fault according to its cause.

Broken transmission line

Perform self-loop test and check whether the transmission line is normal.

Broken timeslot

Find and remove the faults of the timeslot multiplexer.

Inconsistent versions of configuration data

Install the correct versions of configuration data.

Tip: Good transmission quality is required to download the version and data. So re-download all the data when downloading fails due to transmission errors.

OAM timeslot configuration data inconsistency

Inconsistency of OAM timeslot configuration data with the DIP switch setting can cause the OAM timeslot of BTS to break.

Cascaded site Bypass

When two cascaded BTSs share the same OAM timeslot configuration and when the upper-level BTS is bypassed due to power failure, the link between the two BTS sites fails.

To solve this problem, reset the lower-level BTS site.

BTS equipment failure

When E1 interface is faulty or the E1 interface cable has a dry solder, the OAM LAPD link of the BTS fails.

Perform self-loop test to solve this problem. If the E1 LED of the BTS is ON after the test, the fault may be in the BTS.

Replace the related board(s).

LAPD Links of Some Carriers of a BTS Site are Broken

LAPD links of some carriers of a BTS are broken

LAPD board of BSC shows related alarms


Backplane connection error

DTRU failure

BSC hardware failure

Troubleshooting

Symptoms

Fault Analysis



Transmission failure

Remotely reset the CMB to reset the BTS. If the system indicates connection timeout, the communication link between the iOMCR and the CMB of the BTS must be broken.

Check if there are alarms from all DTRUs in the BTS. If yes, follow the steps below to troubleshoot the fault:

Check if the E1 line is correctly connected.

Check if the TIC and LAPD boards on the BSC report alarms. If so, remove the corresponding fault.

Measure the transmission Bit Error Ratio (BER) using a BER tester. If BER is abnormal, remove the transmission faults including transmission equipment faults and grounding faults.

Check whether the DIP switch on the TIC board is set to an appropriate position.

Note: DIP switch setting must be in 75 Ω position when a coaxial cable is used and in 120 Ω position when a twisted pair is used.

Check the connections of backplane if the LAPD links of DTRUs in a single layer are broken.

If the LAPD link of one DTRU is broken, reset the DTRU. If the problem persists, replace the DTRU.

Note: Transmission alarms of BSC appear only when the physical connection is broken. Transmission bit error or poor grounding does not result in such alarms.

LAPD Links of Carriers of Many BTS Sites are Transiently Broken

LAPD links of some BTSs break and automatically recover in 10 ~ 20 seconds without manual intervention.


Transmission interruption or instability, which can be detected from transmission alarm or alarm record.

Transmission problem between the Main Processor (MP) and LAPD boards of the same BSC.

The symptom is that the break or recovery time of the LAPD links of carriers of same LAPD board is similar (in terms of

Troubleshooting

Symptom

Fault Analysis



seconds) while that of different LAPD boards differ slightly from one another.

CMB Reset

The symptom is that the LAPD links of carriers of the BTS are broken or recovered at a time slightly different from one another (the time difference is only several seconds).

Check if transmission alarms occur during LAPD interruption. If yes, do the following :

Check if the contacts of E1 interface is proper

Check if the transmission equipment is properly grounded

Check if alarms occur due to transmission faults

Remove the faults

Analyze the LAPD interruption and recovery time to find the faulty LAPD board and then reset it. If the problem persists, replace the faulty LAPD board.

If LAPD interruption is caused by CMB reset, the system will automatically become normal without manual intervention.

Troubleshooting





C h a p t e r 4

Antenna Feeder Faults

This chapter deals with the analysis of faults such as signal fluctuation, coverage shrinkage and poor conversation quality, caused due to antenna feeder equipment problems.

Overview

Voltage Standing Wave Ratio (VSWR) alarm

Poor uplink or downlink quality

iOMCR may indicate the following three types of alarms:

Major VSWR alarm of a Combiner

This alarm occurs when the VSWR value of the antenna feeder system connected with the combiner is greater than 3.0.

Minor VSWR alarm of a Combiner

This alarm occurs when the VSWR value of the antenna feeder system connected with the combiner is between 1.5 and 3.0.

LNA alarm of a divider

This alarm indicates that the divider is faulty.

Tip: The alarms of combiners and dividers are related to configuration data and physical connections. Therefore, make sure that the configuration data are consistent with the actual physical connections so that the system correctly processes the alarms.

Two transceivers are located in each DTRU – DTRU1 and DTRU2.

Following example describes the problem occurring when the physical connections are inconsistent with data configuration:

Symptoms

Related Alarms



Physical connections:

DTRUA1 - Combiner A - Antenna feeder A

DTRUA2 - Combiner B - Antenna Feeder B

Data configuration:

DTRUA2 - Combiner A - Antenna feeder A

DTRUA1 - Combiner B - Antenna Feeder B

Background combiner A1 reports a major VSWR alarm when VSWR serious alarm occurs at antenna feeder A1. However, the system blocks DTRU A2 due to data configuration error. DTRU A1 still transmits power. In this case, Cell A does not support normal calls due to big VSWR and neither Cell B because it is blocked due to error.

Troubleshooting

1. Replace the CDU that may be faulty with a normal CDU.

2. Check whether the antenna feeder system is normal.

3. Connect the antenna feeder system that may be faulty and the normal CDU using a jumper.

4. If an alarm occurs, the fault lies in the antenna feeder system. If not, the fault lies in the CDU.

Any one of the following problems may cause the antenna feeder system faulty:

Improper installation of connectors

Improper sealing of connectors with water-proof

Damages in feeder or jumpers

High VSWR value of lightning arrestor

High VSWR value of antenna

Water enters the antenna

Check the antenna feeder system and replace the faulty parts if necessary.

If a part does not satisfy the VSWR requirement, it must be faulty. First, check the easily accessible parts before checking the parts hard to reach.

If VSWR alarm occurs occasionally, then the problem may be due to poor contact of cables.

Shake the parts to check the reliability of cable connection.

Replacement

Systematic Check

Chapter 4 - Antenna Feeder Faults


Caution: Disconnect the feed from the tower top amplifier (if any) before measuring VSWR at the TX/RX port on the CDU, to prevent damages due to short circuits.

VSWR Faults

VSWR alarm (Minor or Major)

A minor VSWR alarm occurs when the VSWR value is between 1.5 and 3.0 while a major VSWR alarm occurs when the VSWR value is greater than 3.0.

Board LEDs

Background Operation and Maintenance System

CDU

Antenna Feeder System

DTRU

A CDU reports a major VSWR alarm when it has VSWR2 alarm that lasts for one minute. Upon receipt of this major alarm, the OAM automatically turns off the DTRU.

1. Check whether the CDU is faulty.

Replace the DTRU connected to the CDU by a normal DTRU and test with a test MS if the BTS can normally receive or send signals.

If the BTS can receive or send signals normally, reset the CDU and see if the CDU misreports any alarm.

If the fault does not re-occur after CDU resetting, it indicates that the CDU misreported the alarm. Replace the CDU.

If the fault re-occurs, it indicates that the CDU did not misreport the alarm, and then determine if the CDU is faulty by replacing it with a normal CDU.

If the CDU is not faulty, it indicates that the antenna feeder system may be faulty.

2. Check whether the antenna feeder system is faulty.

Check the VSWR of the antenna feeder system at the connector of 1/2 jumper that is connected with the TX/RX ANT port of the CDU.

Shake this 1/2 jumper and the 1/2 jumper on the cabinet top and check whether there is a big change in VSWR value. If so, the cable may have loose contacts.

Symptom

Source

Related Parts

Fault Analysis

Troubleshooting



If the VSWR value is more than 1.5, the antenna feeder system may be faulty. Solve the fault by checking the antenna feeder system systematically.

3. If the cause of the VSWR1 alarm cannot be determined after performing the above steps, then the fault may be due to the following:

Unstable VSWR processing function of the CDU.

Mismatch of TX/RX ANT port and the 1/2 jumper.

Replace the CDU in the first case and replace both the CDU and the 1/2 jumper in the second case.

4. Check whether the TX port on the DTRU is properly connected to the CDU and the connectors are tightened properly when the DTRU reports a VSWR alarm.

5. Replace the DTRU and check if the DTRU misreports alarm.

Coverage Shrinkage

Output power of the BTS equipment decreases

Coverage shrinks after a period of time

The aging and overload of devices may cause performance deterioration.

Measure the output power of the BTS and replace the AEM if output power is abnormal.

Ensure that the operating temperature is within the specified range.

Ensure that the latest version of software is in use.

VSWR Alarm of the Combiner

iOMCR indicates a VSWR alarm

Blockage of carriers


External environmental interferences

Problem with internal alarm detection mechanism

Confirm the time of alarm occurrence and the radio

Symptoms

Fault Analysis

Troubleshooting

Symptoms

Fault Analysis

Troubleshooting



interference at that time.

Replace the AEM.

Ensure that the latest version of software is in use.

Poor Uplink Quality

Poor conversation quality

Poor uplink quality when viewed from signaling analysis


Faulty antenna or CDU

Faulty CPU

Connection problem between the antenna input port of the CDU and the cabinet top

Faulty antenna feeder system

Check if the CDU reports any Tower Mount Amplifier (TMA) alarm. If so, handle the fault in the way as handling a TMA alarm. For details, refer to TMA alarm

.

Check if the CDU reports any Low Noise Amplifier (LNA) alarm. If so, handle the fault in the way as handling an LNA alarm. For details, refer to LNA Alarm

.

Check if the connection from the antenna input port on the CDU to the cabinet top is normal. If the connection is abnormal, replace the connection cable.

Check the VSWR of the antenna feeder systematically, starting from the cabinet top.

Poor Downlink Quality

Could not make or receive calls from a place where calls were made or received previously.

Poor signal quality or no signal at places where signal quality was good previously.

More dropped calls than before.

Symptoms

Fault Analysis

Troubleshooting

Symptoms



The following factors may influence the coverage of the BTS:

Poor BTS environment

Poor construction quality or maintenance of the BTS

Low PA output power

Decreased receiver sensitivity

Inclined azimuth

Altered antenna pitch angle

Altered gain and height

Feeder cable or combiner loss

Altered working frequency and transmission environment

Check if the threshold of RACH receiving level is altered. If the threshold is much greater than before, it may

decrease the BTS coverage.

Check if strong interference exists around the BTS.

Check the RF cable connection between the DTRU and AEM for any signal leakage or losses.

Check if the SWR1 LED on the AEM panel is ON. If so, check the VSWR values of the jumper, main feeder and antenna segment by segment, until the VSWR fault cause is determined.

Check and adjust the power if the PA output power is abnormal and the operating temperature inside the BTS is too high. If the output power is still low after the adjustment, replace the DTRU.

Check if other antennas or obstacles exist around the BTS antenna. If so, adjust the azimuth and height of the antenna to reduce the influence.

Check if there is a change in the azimuth and pitch angle of the antenna. If so, adjust the azimuth and height of the antenna to exact positions.

Trees with abundant leaves may also affect the BTS coverage.

VSWR Alarm of the Power Amplifier (PA)

PA VSWR alarm


Problems in alarm judgment

Fault Analysis

Troubleshooting

Symptom

Fault Analysis



Problems in GUI processing mechanism

Replace the DTRU that may be faulty with a DTRU of a normal cell. Check if the cell reports the same alarm.

There are the following possibilities:

If the cell reports alarm even after replacing DTRU, then the problem may not be in DTRU. The problem may lie in PA, antenna feeder or backplane.

Replace the boards to eliminate board faults.

If the cell does not report any alarm when DTRU is replaced, then the fault lies in DTRU. Replace the faulty DTRU.

If the alarm of the problematic DTRU disappears and the normal DTRU does not generate any alarm, then the fault may be due to the poor contact of DTRU. If the fault remains, then the fault may be in the threshold settings or other hidden problems. In this case do further analysis to troubleshoot the problem.

Tower Mount Amplifier (TMA) Power Alarm

Tower mount amplifier power alarm


Power fault

Connection problem

Check whether the connections are proper.

Remove the power fault.

TMA Alarm

TMA alarm


Faulty CDU

Faulty TMA

Faulty DTRU

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis




1. Reset the CDU and check whether the TMA alarm disappears. If the alarm does not disappear, it indicates that the CDU misreports alarm. So replace the CDU.

Tip: Upon TMA alarm, CDU automatically disconnects TMA from the feed. Therefore, normally TMA alarm disappears after CDU reset.

2. If the TMA alarm disappears after the CDU is reset, disconnect the jumper from the antenna port on the CDU. Check if the antenna feeder system has any short circuit. Check the feeder, jumpers, and TMA and locate the short circuit.

3. If the antenna feeder has no short circuit, enable the TMA (turn on the TMA feeder through the CDU on the Man Machine Interface (MMI)). Check whether the CDU reports any TMA alarm. If an alarm appears, it indicates that the feed output is normal.

4. Connect an ammeter and 120-ohm resistor in series between the antenna port on the CDU and the 1/2 jumper. Make sure that the external conductor of the port and that of the jumper are in good electrical connection. Enable the TMA feed; check whether the feed voltage and feed current are in the normal working range. TMA is bypassed when the voltage is normal and the current is zero. Replace the TMA.

Tip: Check whether the TMA is faulty by interchanging the faulty TMA with a normal TMA, if the requirements for these steps are not ready.

5. Replace the TMA if the TMA is found faulty.

6. If the antenna feeder system is normal, then the problem may be in the receiving channel of DTRU. Replace the DTRU.

LNA Alarm

LNA alarm

An LNA reports an alarm when the LNA current exceeds 30% more than the normal operating current.

Troubleshooting

Symptom

Fault Analysis



The fault can be located by observing the DTRU. The DTRU connected with the LNA cannot work if the main and diversity LNAs are faulty, or cannot work properly if one LNA is faulty.

Replace the AEM. Troubleshooting



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C h a p t e r 5

Voice Faults

This chapter deals with the analysis and troubleshooting procedures of voice faults.

Common voice faults are as follows:

One-way conversation

Cross talk

Two-way blocking

Noise

Poor conversation quality

Troubleshooting

Users often report two-way blocking as one-way conversation problems. So locate and determine the exact problem.

Check whether the fault occurs to a single BTS or BSC or a larger range.

If the fault occurs only to outgoing calls, check the corresponding outgoing trunk and data. Check all the parts if the fault lies within the local office.

Locate the fault by checking the hardware and data configuration, assisted by dialing test.

If the fault is in BTS, perform drive test and record the frequency and the timeslot occupied by a call, using test MS.

If the fault is in a module, perform A-interface circuit dialing test, determine the trunk occupied by a call and locate the relevant boards through interface message analysis.

For troubleshooting one-way conversation, make a call from an MS to a fixed phone and determine whether the fault lies in the uplink or downlink.



Voice Abnormalities Caused by RF Faults

Call drop

Noise

No voice

RF faults may cause signal loss and poor call quality.

Replace the AEM board connected to the faulty carrier.

Voice Abnormalities Caused by Configuration Faults

Some timeslots are abnormal and are not assigned properly to some carriers during conversation.

The fault may be due to the wrong configuration of connection relations, mostly incase of multiplexing.

Reconfigure the site

One-way conversation

The calls can be dialed normally but only one party can hear the voice of the other party.


Error in timeslot configuration between the BSC and MSC.

Faulty connection between the transmitting and receiving ends of the PCM line.

Error in Dual Rate Transcoder (DRT) timeslot connection.

Error in Digital Switch Network Interface (DSNI) or Bit-Oriented Switching Network (BOSN) timeslot connection.

Uplink or downlink power imbalance on the edges of BTS coverage area.

Symptoms

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Chapter 5 - Voice Faults


Error in Pulse Code Modulation (PCM) timeslot connection between the MSC and the fixed switch.

Check whether the fault occurs inside the local office or at the interconnected systems. Perform dialing tests on the trunk circuits to troubleshoot the problem.

If the fault occurs to the whole MSC, check whether the equipment buyer or other relevant staff has reconfigured the MSC data or performed relevant operations during cutover. Check whether the transmitting and receiving ends of the trunk line on the A-interface is connected properly.

If the fault occurs to the entire BSC or many BTSs of the BSC, Check whether the DRT version is correct. If so, switch over the active DSNI/BOSN with the standby DSNI/BOSN and check whether the problem persists after the switchover.

If the fault occurs to only one BTS, verify the radio parameters and check whether the maximum MS transmit power is correct.

If the problem persists, do dialing test with a test MS to confirm whether the one-way conversation problem is related to a carrier timeslot or not.

If the problem always occurs to a certain carrier, replace the corresponding AEM equipment. Ensure that the latest version of software is in use.

Two-way Blocking

Neither party of the conversation can hear the peer party.

Subscriber may report two-way blocking as one-way conversation. Therefore ensure to locate the exact fault.


Transmission line self loop

Carrier Identification Code (CIC) mismatch between the two ends of the transmission line

Faulty timeslot in the transmission circuit

Improper configuration of the timeslot multiplexer with the time slots when the E1 is shared

Faulty DRT/EDRT or TIC board

An individual timeslot is not configured with the related Digital Signal Processor (DSP)

Faulty AEM.

Troubleshooting

Symptom

Fault Analysis



First, second and fourth cause may lead to two-way blocking of many BTSs. Troubleshoot according to the cause.

Third cause may lead to two-way blocking of single BTS. Troubleshoot according to the cause.

If the problem always occur to a certain carrier and there is no multiplexing, replace the corresponding AEM equipment or connector.

Ensure that the software is upgraded to the latest version.

Poor Conversation Quality

Poor voice quality with distinct noises.

Call disconnection during conversation.

The fault may be mainly due to faulty antenna feeder equipment or software problem.

Poor voice quality is due to high voice BER at the radio interface, which is caused by low receiving level, clock faults or co-channel interference.

Low frequency level may be caused by the following factors:

Inappropriate parameter configuration.

For example, the MS maximum transmission power MSTXMAXCCH (power used during access) and MS maximum transmission power MSTXPWRMAX (power for power control) are inconsistent.

Antenna feeder system faults, such as abnormal VSWR, improper setting of azimuth angle, and pitch angle.

Low BTS transmission power.

Observe the MS signal intensity. If the intensity is low, the receiving level will be low. Comply with the following steps to troubleshoot the fault:

Check if the RF cable between the DTRU and the combiner is normal. If abnormal, connect the cable again.

Check if the SWR1 LED on the AEM panel is on. If so, check the VSWR values of the jumpers, main feeder and antenna segment by segment from the combiner output port, until the cause of VSWR deterioration is found. Replace the faulty parts.

If the alarm LED on the AEM is off, check if the azimuth and pitch angle of the antenna are normal. If not, adjust the antenna.

Troubleshooting

Symptoms

Fault Analysis

Troubleshooting



If the antenna angles are normal, check the measurement report of BTS. Check whether the radio parameters are configured properly. These radio parameters include MSTXMAXCCH and MSTXPWRMAX. Set the two parameter values to 33 dBm in GSM900 network and 30 dBm in GSM1800 network.

If the parameter configuration settings are normal, check the RF cable connection between the divider and DTRU. If the connection is not proper, reconnect the RF cable.

Check whether clock alarms occur at the CMB through the background, or check the CLK LED on the CMB. If the green LED is ON, it indicates that the module is normal (the network synchronization is in locked status). If red LED is ON, replace the CMB. If the CMB LED status is normal, use the Local Monitoring Terminal (LMT) to check whether the frequency offset of the 13 MHz clock output is within the specified range.

If the clock is normal, check if the DTRU reports a phase-locked loop alarm. If there is such an alarm, replace the DTRU.

Accurately set the E1 DIP switch settings on the EIB.

Check whether co-channel interference occurs, if yes, adjust the frequency data.

Replace the antenna feeder equipment and upgrade the software to the latest version.

Crosstalk

The conversation party hears an unexpected third party voice.

The fault may be caused when the transmitting and receiving ends of transmission line are incorrectly connected.

Check whether the fault occurs to intra-office or inter-office calls.

If the fault is in intra-office calls, check whether the transmitting and receiving ends of transmission lines are connected correctly.

If the fault occurs in inter-office calls, check the outgoing circuit connections.

If the fault lies only with a BTS, focus on the transmission of the BTS.

If some E1s use timeslot multiplexers, block the E1 device that uses the timeslot multiplexer before the check.

Symptom

Fault Analysis

Troubleshooting



Poor Conversation Quality of a BTS

Poor conversation quality on busy hour and normal conversation quality when there is little traffic.


Faulty BTS equipment


External interference

Observe the interference band through the background. Interference band is 5 when the conversation quality is poor and 1 when the conversation quality is normal.

Adjust the antenna directions and check if the interference is strong in a particular direction. If yes, it indicates that the there is no fault in the antenna feeder and the equipment.

According to the symptoms, the interference is related to the traffic. So the fault may be in indoor repeater system.

Observe the interference and determine the interference direction through a frequency sweeper.

Noises in Outgoing Toll Call

Good conversation quality in the calls made within the office, but noises in outgoing calls.

The fault may be related to E1 and timeslot multiplexer.

Perform call tests on the toll circuits one by one.

If the E1 lines are found to have a poor conversation quality, then the timeslot multiplexer of the E1 lines may be faulty. Replace the circuits.

Unstable MS Signals in the Idle State

In idle state, there is fluctuation in the receiving MS signals.

Sometimes signals disappear and appear again.

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptoms



Apart from the phone quality and unstable performance caused by the long use of the MS, the factors that influence the wireless signal intensity of a place are as follows:

Environment

Unstable transmission power of DTRU

Cell reselection

Analyze whether the place is covered by multiple overlapped cells. If so, check the reselection relations and reselection parameter settings between cells. Reset the cell reselection settings.

Check whether the RF cable between the DTRU and the AEM is connected normally. If abnormal, connect the RF cables correctly.

Test the PA output power and observe whether the test signal level fluctuates, so as to check the stability of the transmission power of DTRU. Replace the DTRU if it is faulty.

Check the surrounding area of 500 meters around the MS. If multiple obstacles exist, various reflection waves overlap with the MS receiving signal. This causes Raleigh fading and a change of 10 dBm ~ 20 dBm to the receiving MS signal. If obstacles exists near the MS, adjust the azimuth and height of the antenna.

Unstable MS Signal in the Busy State

Unstable MS signal during conversation

If the TCH and BCCH occupied by the MS does not belong to the same carrier and the DTRU is unstable, it will cause the MS to present strong signal in idle state and weak signal during conversation.

Frequent MS handover (ping-pong handover) may cause unstable MS signal during busy state.

Perform on-site dialing test using a test MS and check whether the unstable signal occurs to some time slots of a carrier or multiple carriers.

If the fault occurs to some time slots of a carrier, perform the following troubleshooting steps:

Reset the carrier.

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting



Check the RF cable connection between the DTRU and the combiner, and that between the divider and the DTRU. If the connection is incorrect, connect them correctly.

Replace the DTRU.

If the fault occurs to multiple carriers of a cell, perform the following troubleshooting steps:

Check whether the main and diversity antennas of the abnormal cell are consistent in azimuth and pitch angle. If not, adjust the antenna angles.

Measure the VSWR of the antenna feeder system and check whether the antenna feeder connector is connected properly and is water proof.

Echo in MS Conversation

Echo occurs when the MS is in a conversation.


Fault occurs at the Echo Canceller (EC) set between PLMN and PSTN.

Faulty Transcoder (TC) unit at the BSC.

Faulty transmission circuit of MS.

Loop formed during careless routine maintenance of A interface circuit or Abis interface circuit.

Fault of the device which is responsible for voice decoding in DTRU.

Check the MS for faults that may create echo.

Confirm whether the echo occurs only to the PLMN and PSTN subscribers in conversation. If yes, the EC may be faulty.

Check whether loops occur at A interface and Abis interface. If yes, cancel the loop.

Replace the DTRU.

Check if alarms are generated by the DRT (EDRT) board at the BSC, if yes, reset the board. If the fault remains, replace the DRT (EDRT) board.

Typical Case This section introduces the methods to locate the one-way conversation problem in the GSM BSS network.

Symptom

Fault Analysis

Troubleshooting



Tip: Problems such as one-way conversation, two-way blocking or crosstalk are rather similar and have different symptoms of the same fault in most cases. Therefore such problems are simply referred as one-way conversation problems.

Fault Information Collection

One-way conversation problem is mostly discovered by subscribers. Subscribers report the fault to the customer services center of the operator.

The customer services center transfers the problem report to the maintenance engineer.

Maintenance engineer transfers the problem to the ZTE onsite engineer.

Onsite engineer visits the complaining subscriber and understands the fault symptom. The details that must be collected are as follows:

The MS number of the complaining subscriber and the model of MS used by the customer.

The location area where the subscriber discovered the problem.

The called number dialed by the subscriber.

Fault symptom details: Confirm whether the fault is one-way conversation, two-way blocking, crosstalk or poor conversation quality.

The BTS and the cell in which the subscriber was most probably in, when the problem occurred.

Check whether the one-way conversation problem occurs to one BTS or many BTSs.

Confirm the date when the problem started.

Confirm whether any big network adjustment or data modification operation was done before and after the problem occurred.

Tip: The subscribers’ description of the problem may slightly differ from the fact and the collected information may not completely reflect the existing problem. So collect all the relevant original information and learn the relevant information as concise as possible from the customer.

Fault Analysis

1. Determine the range of fault occurrence



After collecting fault information, analyze the possible fault causes and locate the fault as per the following:

i. Check whether the MS has the problem

If the subscriber’s MS is of poor quality or if the subscriber uses the MS improperly, one-way conversation problem may occur. Perform dialing test with another MS of same model and check whether the problem disappears. If the problem disappears, it indicates that the MS used by the subscriber is problematic.

ii. Check whether the problem is caused by radio defects

Confirm whether the fault is one-way conversation or two-way blocking or cross talk. When radio interference occur in the uplink/downlink, the subscriber may not be able to hear any voice and misreports the problem as one-way conversation problem.

Perform dialing test at the site and confirm whether the problem is caused by interference. Also check the performance analysis report to find the interference in uplink/downlink.

iii. Check whether the problem is caused by the BTS

If the problem occurs only to one or two BTSs, then the BTS (s) may be faulty.

iv. Check whether the problem is caused by the BSC

If the problem occurs to many BTSs of the BSC, then the BSC may be faulty.

v. Check whether the problem is caused by the MSC or GMSC

If the problem occurs to many BSCs connected to an MSC, then the MSC may be faulty.

2. Onsite dialing test

Perform onsite dialing test with a special test MS (generally SAGEM).This special test MS can display cell information, lock the frequency, and implement forced handover. Modify the parameters of the cell to be tested so as to allow only the test MS to access the cell; otherwise the test may be interfered by ordinary subscribers. For detail information, refer to CBA Parameter

The actual networking is as follows:



F I G U R E 1 - SY S T E M N E T W O R K I N G

Consider BSC1-BTS2 as the hot spot complained by the subscriber. BSC1 is a BSC provided by ZTE. BTS1 is a BTS of an adjacent cell, and the connection between BSC2 and the BTSs are normal.

i. Test

Lock the MS A to the frequency of BTS2.

Make calls from MS A to MS B until the one-way conversation problem occurs to a call. Remain connected.

ii. Record

Record the cell information in which MS A resides, the used BCCH/TCH frequency, the timeslot number, and BER in the downlink.

iii. Confirmation

If ambiguity arises in determining whether MS A or MS B has one-way conversation problem, use another MS C to call MS A. If one-way conversation problem occurs during the conversation between MS A and MS C, it indicates that MS A has problem. Otherwise, MS B has problem. Similarly, use another MS C to call MS B and determine whether MS B has problem.

Also use Dual-tone Multi Frequency (DTMF) signal to judge the side which has a problem. For detailed information about DTMF, refer to DTMF Signal Tone

iv. Handover



If BTS2 is a directional antenna covering more than one cell and if the MS A is in cell 1, forcibly handover MS A to cell 2 and check whether the one-way conversation problem exists. If the problem disappears, it indicates that the DTRU of cell 1 is faulty.

If BTS2 is an Omni directional BTS and covers only one cell, forcibly handover MS A to its adjacent cell and check whether the one-way conversation problem still exists. If the problem disappears, it indicates that the BTS2 is faulty.

Handover MS A from BTS2 to BTS3 and check whether the problem disappears. If so, it indicates that BSC1 is faulty.

3. Voice route analysis

Analyze the path of voice flow between MS A and the MSC. The voice flow is as follows:

MS - Antenna - AEM - DTRU - CMB - Abis interface/Transmission equipment - TIC - BIPP - BOSN - TCPP - EDRT - AIPP - TIC - A interface/transmission equipment - MSC.

BOSN board of the BSC provides the switching function while the physical timeslots on the other boards correspond one to one.

If the problem lies in the BTS, then the fault must be in the following paths: Antenna – AME – DTRU – CMB – Abis interface/transmission equipment – TIC – BIPP – BOSN.

Troubleshooting

1. Troubleshooting BTS fault

The troubleshooting steps for a BTS fault are as follows:

i. Check whether there is software mismatch in BTS boards.

ii. Check whether there is any abnormal BTS alarm.

iii. Delete the BTS hardware data and reconfigure the data so as to eliminate data errors.

iv. Replace the problematic DTRU board and check whether the fault is caused by DTRU.

v. Replace the CMB board and check whether the fault disappears.

vi. Modify the data and connect the BTS to another BTS port if another Abis interface exists, and check if the fault disappears. If the fault disappears, replace the TIC board and BIPP board in turn and find out the faulty board.

2. Troubleshooting BSC fault



i. Test

If the fault is detected in many BTSs, then the BSC must be faulty. If there is coverage of the BSC in the equipment room, perform frequency locking test using a test MS. Otherwise install a test BTS for the test. Conduct the test after 0000 Hrs so as to facilitate fault locating and to avoid influence on subscribers.

Most of the one-way conversation problem is related to A interface circuit. Conduct dialing test on the A interface.

ii. Record

Record the A interface CIC occupied by each call during the test. Check whether the fault occurs and the fault symptom is similar.

iii. Fault locating

BSC generally contains a central module and several peripheral modules. Check and judge whether the fault is related to all peripheral modules or a single peripheral module. If the fault is related to one module, focus and check the module and the cable connections between the peripheral module and the central module. If the fault is related to all peripheral modules, focus the check on the central module and the A interface circuit.

iv. Board switchover

If the fault is suspected to be in the boards such as BOSN and PP that has active/standby modes, perform board switchover and check whether the fault lies in these boards.

v. Board resetting

Many fault symptoms may disappear after board resetting but avoid resetting the board before the fault is completely located, because the fault may reoccur.

vi. A interface check

Two conclusions can be finally drawn from the dialing test:

One-way conversation problem is related to the specific circuit in the A interface.

There is no fixed relationship between the one-way conversation problem and the A interface circuit.

In the first case, if the one-way conversation problem occurs to all the timeslots of a 2 Mbps circuit, then the A interface circuit line may be cross connected with another circuit line, as shown in Figure 2.



F I G U R E 2 - CR O S S -C O N N E C T E D C I R C U I T S

If the one-way conversation problem occurs to a single timeslot, the problem may not lie in the cable but may be in boards such as EDRT and BOSN. Do Switchover, reset, or replace boards to determine the faulty board.

If a timeslot is normal sometimes and abnormal other times, the problem may be in the boards such as BOSN and EDRT.

Summary

The causes for one-way conversation problem are summarized as below:

Problems of the MS

The design, aging or faults of MSs may cause one-way conversation problem.

BTS equipment problems, for example faulty timeslot of DTRU or CMB board.

Problems of the Abis interface circuit, for example, an individual timeslot embezzled by subscribers, faulty TIC or PP board.

Problems of the connection cable between the peripheral module and the central module, such as poor contact.

BOSN board problems.

Problems of the EDRT, TCPP, AIPP or TIC board, mostly EDRT board problems.

Problems of the A interface. For example, incorrect cable connection and cross-connection of wires.



Data problems, such as incorrect CIC correspondence between the BSC and the MSC.

In practice, problems often occur to the BTS, the DRT board and the A interface.





C h a p t e r 6

Loading Faults

This chapter analyses the faults that may occur during the software loading process.

Software Version Cannot be Imported

iOMCR prompts errors when importing software version.

The fault may be due to the mismatch of version file name and the internal ID.

This fault is mostly caused by incorrect creation of the new version or manual change of the file name.

Avoid changing the file name manually.

Loading Failure

Loading process keeps repeating.

BTS site keeps restarting and could not start normal operation.

Signaling analysis helps to locate the fault causes. The causes are as follows:

Transmission errors, which causes reloading

Mismatch of software version with the hardware

Symptom

Fault Analysis

Troubleshooting

Symptoms

Fault Analysis



Check for transmission errors and remove the errors.

Update the software version so that the version matches the hardware.

Load the software strictly in accordance with the up gradation procedure.

CMB/DTPB Board Unable to Start

After loading the software and when the board is restarted, the CMB/FUC board could not start normal operation and the boards LEDs stop flashing.

The downloaded software version CMB_FPGA/DTPB_FPGA may be incompatible with the hardware

Follow the up gradation procedure strictly and download the software version of the problematic board by using the local downloading tool.

The Board Software cannot be Imported

iOMCR prompts version mismatch.

The fault may be due to the Mismatch of version ID and the version name.

Generally this problem is caused by operation errors in the process of making the version file.

Strictly use the software version released in the formal version library.

Repeated Loading of CMB

CMB of the BTS site keeps restarting and loading

FU LAPD link is broken

System indicates a cell interruption alarm

Troubleshooting

Precautions

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptoms

Chapter 6 - Loading Faults



CMB version mismatch

Packet loss during transmission

Perform Abis signaling trace and check whether the loading process is completed.

Check the data transmission if:

The BTS does not respond in the loading process.

Re-transmission of loaded data exceeds certain number of times which leads to re-initiation of the loading.

If software loading is successful, but software fails to activate, then check whether a correct version is loaded.

Repeated Loading of DTRU

CMB loading is completed, the configuration data are normally received, HDLC link of the DTRU has been established, but the DTRU keeps loading and resetting.

The fault may be due to DTRU software version mismatch.

Check the compatibility between the DTRU software version and the hardware.

LAPD Link Establishment Failure after Software Loading

CMB cannot establish a link after software loading.

The fault may be due to the mismatch of Software version (CMB_FPGA).

Directly download the available version of the CMB software using the local downloading tool.

Upgrade the software strictly in accordance with the version up gradation procedure.

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Precautions



FU LAPD and HDLC Disconnection Alarms

DTRU keeps loading or resetting

LAPD and HDLC links are broken as viewed from iOMCR

The fault is mainly due to the mismatch of software version and the hardware.

Download the version again.

If the DTRU could not start, download the version using the local downloading tool.

Symptoms

Fault Analysis

Troubleshooting


C h a p t e r 7

Clock Faults

This chapter analyzes the problems that may occur during clock synchronization.

Overview Symptom

The symptoms for clock faults are as follows:

CMB alarm

DTRU alarm

Slow internet access of the MS

MS handover failure

Poor conversation quality of the MS

Notification Messages and Alarms

The system generates alarms for the first two symptoms. So handle the faults according to the alarms.

Last three symptoms are related to the BTS clock and the system may not generate any alarms. So check whether any exceptions occur to the clock during the troubleshooting process.

The following alarms are related to the clock:

Abnormal Clock (13 MHz, FCLK, SYNCLK)

Accumulative frame number of the software is inconsistent with the accumulative frame number of the hardware

L3 software of the FUC is not responding temporarily



Clock alarm between the TPU and the CMB

TPU frame number alarm

Local oscillator PLL1 or PLL2 of the receive RF is out of lock

Local oscillator PLL1 or PLL2 of the transmit RF is out of lock

PLL of the 52 MHz reference clock is out of lock

Local oscillator PLL of the transmit IF is out of lock

DLRC_AL downward check error

Fault Analysis

The main cause of a clock fault is that the BTS clock severely deviates from the clock required for the normal running of the BTS. The symptom is that the RF unit does not get a precise clock.

The clock fault is caused by the following:

Inaccurate 13 MHz clock signal generated by CMB

Unstable 13 MHz clock signal generated by CMB

CMB is in synchronization with the external clock but the clock reference received from the BSC is unstable

Faulty PLL of the DTRU

Poor contact of the clock cable with the CMB and the DTRU

PLL is deadlocked

Troubleshooting Clock Module Reset/Restart

Reset the modules (CMB and DTRU) which had alarms.

Power off the modules (CMB and DTRU) which had alarms.

If it can be recovered through the above ways, it indicates that the PLL is deadlock and hardware is normal.

Carrier Clock Faults

Check the clock cable between the CMB and DTRU if the DTRU reports a PLL out-of-lock alarm.

If the clock cable is found normal, replace the CMB.

Chapter 7 - Clock Faults


If the problem persists, replace the DTRU.

Classified Faults

Clock and frame number alarms

PLL clock loss

DSP WATCHDOG overflow

Slow internet access of the MS

Problem in handover

Poor voice quality

The clock deviation causes

Unstable system running

Increased bit errors

Hardware response problem

Check the synchronization between the BTS and the BSC.

Check the clock locking function of the CMB board.

The problem may occur to extended racks.

Clock alarms

Clock alarms and frame number alarms occur to the CMB and DTRU

Synchronization abnormalities occur

CMB could hardly lock its clock phase during external synchronization

CMB reference clock deviates during internal synchronization

Measure the CMB clock reference, check the transmission for external synchronization and calibrate the CMB reference clock for internal synchronization.

Symptoms

Fault Analysis

Troubleshooting

Precautions

Symptom

Fault Analysis

Troubleshooting



L3 Software Not Responding

L3 software of FUC no response alarm occurs

Calls often drop


Faulty clock transmission between the CMB and the DTRU

Unstable HDLC link

Abnormal working of DTRU

Check the backplane and replace the DTRU.

PLL Lock Loss Alarm Frequently Occurs/Recovers

PLL alarm occurs and recovers soon. This keeps repeating.

PLL lock loss caused by unstable clock differs from the PLL permanent PLL lock loss caused by hardware fault.

Check the clock and backplane

Plug/unplug or replace the DTRU

Metal Noise during Conversation

A sharp noise like the metal collision sound is heard during conversation.

The clock deviation causes bit errors and error frames during the decoding process.

Check the clock and the backplane.

Plug/Unplug or replace the DTRU.

Symptoms

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Chapter 7 - Clock Faults


Call Drop during Handover

Call drop occurs during handover but the signal level is good and there is no interference.

Onsite test results show that the frequency offset of 13 MHz clocks of some BTSs is as high as 2.5 Hz (far more than the standard value 0.65 Hz).

Many BTSs reports 8 kHz clock alarm.

MSC often reports the normal/abnormal phase locking of the clock software alarm, indicating that the MSC clock is also inaccurate. Therefore, it can be determined that the call drop problem during handover may be due to the MSC clock instability.

Adjust the MSC clock reference source.

High Handover Failure Ratio

High inter-BSC handover failure ratio for a newly deployed BTS

An inter-BSC handover failure can be caused by either of the two BSCs.


Free running of adjacent BTSs of other vendors.

Big clock deviation of adjacent BTSs of other vendors.

Adjust the clock working mode of the BTSs of other vendors.

Symptom

Fault analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting





C h a p t e r 8

Service Faults

This chapter analyzes the faults such as weak signal, call drop, poor voice quality, and handover faults.

Overview Symptoms

Service-related faults are the faults that occur to the call service when the BTS does not give any alarm.

These faults include

Weak signal

Call drop

Poor voice quality

Handover failure

No traffic in a cell

The fault may be caused due to the following:

Data configuration errors or physical connection errors that occur during commissioning.

Board hardware problems.

Environmental problems, such as the coverage change caused by flourishing trees in summer.

Antenna feeder system problems.

Problems of network optimization (such as co-channel interference and improper parameter setting).

Fault Analysis



Troubleshooting BTS Call Test

SAGEM MS or NOKIA test MS

In urban areas, dial calls at about 200-300 m away from the antenna of each cell in the positive direction.

In suburban areas, dial calls at about 500-1000 m away from the antenna of each cell in the positive direction.

Ensure that the call test cover each carrier.

Record the level and quality of the call on each timeslot of each carrier.

Use Table 5 for the call test records.

T AB L E 5 - C A L L TE S T R E C O R D

TRX1 CELLID

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

CH

RXLEV

RQ

CH

RXLEV

RQ

If any problem occurs to the receiving level or the voice quality during carrier testing, handle the problem in time and ensure that the equipment commissioning quality is good.

Performance Analysis

Generate a report that covers all performance indices. For voice calls related problems, perform the following steps:

Check the interference band.

Check the uplink/downlink level.

Check the uplink/downlink quality.

Check SDCCH and TCH assignment time.

Check the assignment success ratio.

Tools

Test Procedure

Check After Test

Chapter 8 - Service Faults


For handover related problems, perform the following steps:

Check the handover attempts.

Check the handover success ratio.

Create a handover observation task and observe the specific handover data of the problematic cell.

Signaling Procedure Analysis

Use the data obtained through drive test and Abis/A interface signaling analysis, and analyze the problems in the call procedure and call processing.

Poor Signal Quality or Signal Fluctuation

MS indicates unstable signal

Signal sharply fluctuates when the MS is in idle state


Problem in software processing

Problem in GPRS related services

Check if the GPRS services are activated in the particular cell.

Check whether the cell system messages indicate any GPRS-related information.

Check whether the connection between the CDU and the RF equipment is normal.

Check whether the output power is normal.

The problems that occur periodically are mostly related to software problems. So perform signaling analysis to solve such problems.

Frequent Call Drops due to Hard Handover

Handover does not take place

Week signal

Symptoms

Fault Analysis

Troubleshooting

Precautions

Symptoms



Call drop


Incorrect handover setting

Inconsistency between parameter settings and the actual situation

Poor network coverage

Clock deviation

Perform signaling analysis and find the fault cause.

Observe the signal receiving status of the moving MS.

Observe the signal quality of adjacent cells and check whether any handover request has been initiated.

No Traffic in the Cell or Sudden Rise of Call Drop Ratio

No call in the cell during busy hours

MSs in the coverage area cannot make calls or even access the network

Cell performance suddenly deteriorates

A call on a certain carrier is soon dropped

The signal is strong and there is no alarm

The fault may be mostly due to the failure of components inside the TRX.

Reset the TRX or CMB to solve the problem temporarily.

Upgrade the software to the latest version to solve the problem permanently.

MS indicates Signal Fluctuation or No Signal

Signal level suddenly drops when the MS is idle or in conversation without fast moving, but the conversation is normal.

Fault Analysis

Troubleshooting

Symptoms

Fault Analysis

Troubleshooting

Symptom



Some MSs indicate CS signal fluctuation when the PS ATTACH operation fails. This fault is mainly due to the GPRS configuration errors.

Check the GPRS configuration or disable the GPRS option of the cell.

System Prompts Failure to Connect

The called MS is idle, the cell also has idle channels but the caller receives a message that the called MS is not in the service area.

The called MS may be attempting PS ATTACH. Most MSs may not respond to the CS paging message when processing the PS service, and as a result the network reports that the MS is not in the service area.

Confirm whether the PS service rights of the MS are correct.

Confirm whether the PS configuration of the cell is correct.

Continuous ATTACH operations may affect the network performance.

Strong Signals but Unable to Make a Call

MS indicates good signal strength but the user cannot dial any call.

According to the performance statistics, all the indices of this cell are 0.

The BCCH of the cell fails and cannot receive any signal from the MS.

Reset the BCCH to solve the problem temporarily.

Upgrade the BTS software to the latest version.

When this problem occurs to a carrier other than the BCCH, that carrier may have a high call drop ratio.

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Precautions

Symptoms

Fault Analysis

Troubleshooting

Precautions



Handover Failure

Week MS signal during conversation

MS does not perform handover operation until a call drop occurs


Poor network coverage

Improper adjacent cell configuration

Improper handover configuration

Inaccurate BTS clock

Check and confirm whether the network and handover parameters are configured properly.

Calibrate the BTS clock.

Occupation of Carrier for Short Time

TCH is assigned normally but it cannot be occupied for long time.

The fault may be due to the faulty hardware or its incorrect connections.

Check whether the connection between the DTRU and PA is normal.

Check whether the connectors are in good contact.

Replace the cables if necessary.

Check whether the RF cables between the two signal input ends and divider output ends of the carrier are connected normally. Replace the RF cable if necessary.

Dial calls with the test MS on site and observe the timeslot occupation of the carrier using the dynamic tracing function in the background. If this symptom happens at once when a timeslot is occupied, reset the carrier and check if the fault disappears. If the fault persists, replace the carrier.

The Carrier Cannot be Occupied

Symptoms

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom



The carrier is normal, but the frequency of the carrier cannot be occupied always.


According to the TCH assignment algorithm of ZTE BSC, if the time slot is assigned unsuccessfully, the priority of this time slot will be decreased and the time slots of other carriers will be assigned first in the next assignment. This time slot may not be assigned until the traffic becomes heavy. So after blocking the other TCH carriers, the time slot of this carrier can be normally occupied.

Poor contact of DTRU pins with the backplane.

Low output power of the carrier.

Observe the timeslot occupancy of this carrier through dynamic data management (with the tracing function) and confirm that this carrier is not been occupied for a long time.

Block the TCH timeslots of other carriers by blocking the logical channel during low traffic hour.

If the TCH is occupied stably for a long time, the fault may be due to the assignment errors in the assignment algorithm. Keep the carrier unchanged, continue to observe whether the fault still occurs and the current cell performance indices decrease.

If the timeslot is temporarily occupied (less than 10 seconds), check if there is any faulty timeslot in this carrier. Reset the carrier and continue the observation. If the problem persists, check if the output power of the carrier or PA is too low.

Go to the BTS site and test the power or the receiving level of the test MS and check if the RF cables from the two RX ports of the DTRU are connected properly with the divider and not damaged.

If the carrier is still not occupied after blocking the other carriers, go to the BTS site and check whether the DTRU-PA-divider RF cables are connected properly. Also, check if the DTRU is inserted properly in the backplane. If necessary, interchange the DTRU with another.

Fault Analysis

Troubleshooting



Long SDCCH Occupation Time

SDCCH is occupied for a long time.


Faulty SDCCH carrier.

Transmission bit errors.

Incase of a new site, the MSC may not have included the site in Cell Identity (CI), causing MS location update failure.

Check if the SMB/TIC board of the BSC is replaced recently and if the DIP switch of the SMB/TIC is configured correctly.

Impedance mismatch of the SMB/TIC DIP switch may cause bit errors in the transmission. Use BER tester to measure bit errors.

Configure the channel for this carrier or change the carrier.

Sudden Rise of Call Drop Ratio

The call drop ratio in a cell rises

The fault may be mainly due to the equipment instability.

Check the operation log and confirm that no parameter change that may affect the network operation has been conducted.

Check if the antenna feeder system is altered before fault detection. If yes, go to the BTS site and check the antenna feeder connections, the standing wave ratio, and the RF cable connections.

Observe alarm records of the CMB board. Check if there is any abnormal transmission alarm.

Check the alarms of every carrier to see whether there are alarms of RPP-to-CHP main set, or diversity uplink data check error (DSPO). If so, replace the carrier.

Block the TCHs of all carriers except one carrier through the iOMCR dynamic data management window (Ensure not to block the SDCCH). Observe (using the tracing function) the timeslot occupancy of this carrier.

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting



Check whether the TCH occupancy of a timeslot is below 10 s. If the timeslot is faulty, reset the DTRU remotely and observe whether the call drop ratio is improved.

BTS Overload Message

No calls can be made under the BTS.

BTS overload messages are indicated in the Signaling trace.


External interference

CMB fault

Incorrect cable connections in the backplane

Check the interference band and use alternative frequency.

Replace the CMB.

Check the backplane cable connections.

Low TCH Assignment Success Ratio

TCH assignment ratio is low (about 30% - 40%), but recovers soon.

The fault may lie in the hardware and its connection.

Select an appropriate time when the traffic is low; Block all TCHs of the other carriers except one TCH through dynamic data management. Observe whether calls can be made normally and then check the system until the faulty DTRU and TCH are located.

If alarm occurs, handle the fault according to the alarm information.

If no alarm, handle the fault as the following steps:

i. Check the RF cable connection between the DTRU and the combiner of AEM, and the RF cable connections between two receiving ends of the DTRU and the AEM divider output port. If the RF cables are incorrectly connected, connect the cables correctly.

ii. Reset the DTRU. If the problem persists, replace the DTRU.

Symptoms

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting



iii. If DTRU is normal, replace the AEM.


C h a p t e r 9

Board Faults

This chapter introduces the troubleshooting procedures to solve board faults.

Trunk Node Alarm

Trunk node alarm is not correctly reported.

The valid bits of Trunk node alarm are not in the default values (zeros and ones). The recovery strategy may not work for trunk node during BTS processing.

Check whether the CMB board location is the same as in the configuration.

Reset the CMB.

Clear the BSC alarm and get the alarm again.

Backplane Fault

The backplane has no corresponding alarm slots, but clock, HDLC, LAPD or other faults may occur.

Backplane is responsible for the clock and communication between CMB/DTRU/AEM/EAM, and a backplane fault may lead to communication fault.

Check whether the board is faulty. If the board is normal, the fault lies in the backplane. Contact local ZTE office or ZTE customer support center.

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting



Abnormality of Standby CMB Board

An alarm indicates that the standby CMB board is abnormal or not in position.

System indicates the active CMB board as standby.


The actual slot where the CMB board is located is not the same as the configured one.

The local board alarms reported by the CMB are rejected by the BSC while the standby board information reported by the CMB is considered as the active board information.

Adjust the CMB location

Change the configuration

HW Link Interruption for a Long Time

All HDLC links of DTRUs in the BTS site are disconnected.


Faulty communication port of CMB

Faulty CMB backplane

Replace the board.

PA VSWR Alarm

A VSWR alarm occurs to the PA


Faulty DTRU internal circuits

Faulty TX interface connection line.

Reset the DTRU.

Replace the RF cable.

Symptoms

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Symptom

Fault Analysis

Troubleshooting

Chapter 9 - Board Faults


Major Clock Alarm on Active and Standby CMBs

A major clock alarm occurs to both active and standby CMBs.


Faulty clock related boards.

Faulty active CMB board (possibly internal chip failure).

Switchover the CMB, and replace the faulty CMB.

Symptom

Fault Analysis

Troubleshooting





A p p e n d i x A

CBA Parameter

This section deals with the modification of Cell Bar Access (CBA) parameter.

CBA Parameter Modification

During the test, it is sometimes necessary to put the cell in to the test status, so that common MSs cannot access the cell and comprehensive tests can be conducted with a test MS without any interference from common MSs. The simplest solution is, to modify the Cell Bar Access (CBA) parameter of the cell, as shown in Figure 3.

F I G U R E 3 - CB A M O D I F I C AT I O N



Cell Bar Access option is not selected for normal cells. When it is selected, common MSs will not be able to access the cell.

After modifying this parameter, find the corresponding CBA option on the test MS and change the status into Reverted or Disabled.


A p p e n d i x B

DTMF Signal Tone

This section explains the generation of DTMF signal tone.

DTMF Signal Tone Generation

In GSM system, on pressing a numeric key on MS (after the establishment of call connection), the peer party hears a DTMF signal tone generated by MSC. Actually the MS sends the START DTMF signaling to MSC via BSC. The specific function board of the MSC generates the DTMF signal tone to send it to the peer end. When the numeric key is released, the MS sends the STOP DTMF signaling. After receiving the signaling, MSC stops sending the DTMF signal tone. The signaling procedure is shown in Figure 4.

F I G U R E 4 - DTMF S I G N AL TO N E GE N E R A T I O N

MMI MSkey X depressed START DTMF（X）

BSS

START DTMF（X）

MSC

Tone X ONSTART DTMF（X）

ACKNOWLEDGESTART DTMF（X）

ACKNOWLEDGEACKNOWLEDGE

key X released STOP DTMF STOP DTMF Tone OFF

STOP DTMFACKNOWLEDGE

STOP DTMFACKNOWLEDGEACKNOWLEDGE

As long as the MS-BSC-MSC signaling is normal (the MS can make calls and get through), the MSC generates the DTMF signal tone when the subscriber presses any numeric key on MS. If the called party could hear the DTMF signal tone but not the voice, then the voice channel from MS A to MSC may be faulty and there is no problem with the voice channel from the MSC to the called party.





A p p e n d i x C

Abbreviations

Abbreviation Full Name

A

AEM Antenna Equipment Module

AIPP A Interface Peripheral Processor

B

BIPP Abis Interface Peripheral Processor

BOSN Bit Oriented Switching Network

BSC Base Station Controller

BTS Base Transceiver Station

C

CHP Channel Processor

CI Cell Identity

CLK Clock

CMB Controller & Maintenance Board

D

DRT Dual Rate Transcoder

DSNI Digital Switch Network Interface

DTRU Dual-carrier Transceiver Unit

E

EAM External Alarm Module

EDRT Enhanced DRT

EMI Electro-Magnetic Interference

F

FDM Fan Distribution Module

H

HDLC High Level Data Link Controller

I



Abbreviation Full Name

IF Intermediate Frequency

L

LAPD Link Access Procedure ‘D’ Channel

LMT Local Management Terminal

M

MS Mobile Station

MSC Mobile Switching Center

P

PA Power Amplifier

PLL Phase Lock Loop

PP Peripheral Processor

S

SWR Standing Wave Ratio

T

TCPP Transcoder Unit Peripheral Processor

TIC Trunk Interface Circuit

TPU Transceiver Process Unit

TRM Transceiver Module


A p p e n d i x D

Figures

Figure 1 - System Networking ............................................ 39

Figure 2 - Cross-connected circuits ..................................... 42

Figure 3 - CBA Modification ................................................ 69

Figure 4 - DTMF Signal Tone Generation .............................. 71





Tables

Table 1 - Chapter Summary ................................................ xi

Table 2 - Typographical Conventions ................................... xii

Table 3 - Mouse Operation Conventions ...............................xiii

Table 4 - Safety Signs.........................................................1

Table 5 - Call Test Record.................................................. 56



This Page is intentionally blank.


Index

add/drop multiplexer ...........10 AEM. .................................27 antenna feeder system ........34 azimuth .............................24 Backplane Fault ..................66 BER ..................................16 BIECOM.............................14 BOSN ................................31 BTS clock...........................60 call processing....................57 call test record....................56 Carrier Identification Code....31 CBA ....................ii, 39, 71, 72 CDU ..................................21 cell interruption ..................47 Cell reselection ...................35 co-channel interference........32 Combiner...........................19 connection timeout..............16 Coverage Shrinkage ............22 Crosstalk ...........................33 dialing test.........................29 DIP switch ................... 16, 33 divider...............................19 DLRC_AL ...........................50 drive test ...........................57 DRT/EDRT..........................32 DSP WATCHDOG.................51 DTMF ................................73 Dual Rate Transcoder ..........30 Dual-tone Multi Frequency....40 E1 transmission tester. ........14 Echo .................................36 Echo Canceller ....................36 FCLK .................................49

forced handover ................. 39 FUC board ......................... 46 GPRS ................................ 57 Handover .......................... 57 LNA alarm ......................... 27 Local Monitoring Terminal .... 33 network optimization........... 55 OMCR .................................7 One-way conversation ......... 30 PA VSWR Alarm.................. 67 PCM line ............................ 30 ping-pong handover ............ 36 pitch angle......................... 24 PLL ................................... 50 Poor Conversation Quality .... 32 Poor Downlink Quality ......... 23 Poor Uplink Quality ............. 23 power ............................... 20 PS ATTACH ........................ 59 Pulse Code Modulation......... 31 SDCCH.............................. 62 Signaling trace .....................7 Super administrator ..............3 SYN LED............................ 13 SYNCLK............................. 49 test MS ............................. 29 TMA Alarm......................... 26 Toll Call ............................. 34 Tower mount amplifier......... 25 Trunk Node Alarm............... 66 TS allocation ...................... 10 Two-way Blocking ............... 31 virus ...................................4 VSWR ..........................19, 20

ZXG10 B8018 Maintenance Troubleshooting

Documents

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