4 gsm call drops (influence factors + troubleshooting methods and tools + deliverables)...

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

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23/4/17

Prepared by: Wang Zhicheng

Approved by: Qi Haofeng

GSM Call Drop: Influence Factors + Troubleshooting Methods and Tools +

Deliverables

July 30, 2011

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

Abstract

This slide provides the main factors that affect the GSM call drop rate, 14 standard

actions required for troubleshooting call drops, and the methods for identifying the

main factors that affect the GSM call drop rate, such as analyzing top N problem cells

and call history records (CHRs). This slide also lists the required deliverables for

reporting call drops, including the analysis results of top N problem cells and CHRs. In

addition, this slide provides some representative cases, which indicate that it is

significant for onsite engineers to analyze call drops according to the standard actions

and call drops are mainly caused by common problems including inappropriate

parameter settings, cross coverage, missing neighboring cells, interference, and

indoor signal leakage.


Date Version Description Reviewer Author2010-11-30 Version issued

in December 2010

1. Added principles for selecting top N cells.

2. Added CHR analysis, including the instructions for analyzing CHRs by using the Nastar and Insightsharp.

3. Added common measures for optimizing call drops.

4. Added the checklist for troubleshooting call drops.

Yan Yafeng (employee ID: 37189), Zha Shuangliu (employee ID: 57469), Zhao Jinjin (employee ID: 105415), Ni Hongxiang (employee ID: 50324), Zhu Kan (employee ID: 137966), Chen Ruiqun (employee ID: 140495), Chen Kai (employee ID: 143018), Li Wenhui (employee ID: 146717), Jiang Ying (employee ID: 162124), Peng Xiang (employee ID: 119711), Chen Wei (employee ID: 119773)

Wang Zhicheng (employee ID: 151324)

2011-07-30 Version issued in July 2011

1. Added call drop analysis based on various data and required actions to focus on the procedure for analyzing call drops and the required data and tools.

2. Added the methods for identifying and troubleshooting call drops caused by other factors.

3. Added the required actions for troubleshooting call drops.

4. Added the impacts of parameter settings from other vendors on call drops and related cases.

5. Added the impacts of traffic sharing on a dual-band network or a network configured with the co-BCCH on call drops and related cases.

6. Added the impact of seasonal changes in KPIs on call drops and related cases.

7. Added the cases of optimizing the top N cells where call drops occur.

Qi Haofeng (employee ID: 118729), Si Fazhong (employee ID: 119461), Chen Wei (employee ID: 119773), Wang Fei (employee ID: 162184), Zhang Liang (employee ID: 51995), Zha Shuangliu (employee ID: 57469), Zhao Jinjin (employee ID: 105415), Shi Yuan (employee ID: 146349), Guo Hongliang (employee ID: 42533),

Ni Hongxiang (employee ID: 50342), Zhu Kan (employee ID: 137966), Chen Ruiqun (employee ID: 140495), Chen Kai (employee ID: 143018), Li Wenhui (employee ID: 146717), Li Peng (employee ID: 52434), Liu Fang (employee ID: 58813), Jiang Xueyi (employee ID: 59075), Xun Lijun (employee ID: 54865), Wan Lu (employee ID: 51624), Wang Song (employee ID: 55188)

Wang Zhicheng (employee ID: 151324), Xu Binbin (employee ID: 39448)

Change History


R&D Technical Support

For call drops, Huawei provides trainings and 7 x 24-hour technical

support.

The following table lists the R&D technical support personnel and

their contact methods.

Name Employee ID Telephone Number

Wang Zhicheng 00151324 See the telephone book.

Xu Binbin 00039448 See the telephone book.

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 5

Call Drop Problem Overview

Call Drop Cases

Actions and Deliverables Required for Troubleshooting Call Drops

Cause Analysis and Data Processing


Call Drop Measurement A call drops when it is terminated abnormally. For example, a call is terminated because the

BSC or the MS releases the TCH due to an exception. Call drop measurement: When receiving a Connection Failure or an Error Indication message

from the BTS, the BSC sends the Clear Request message to the MSC and measures one call drop in a corresponding performance counter based on the cause value.

Call drop measurement during drive tests (DTs): The BSC measures one normal call release when the Disconnect or Channel Release message is received during a DT call. Only when the BSC receives neither of the preceding messages and the MS enters idle mode from the dedicated mode, the BSC measures one call drop.

Calculate call drop counter

Connection failure

Error indication

Clear request

MS BTS BSC MSC


Call Drop Types in Terms of KPIs The BSC measures call drops by cause, which facilitates call drop type identification and

cause analysis. In normal cases, most call drops are caused by Um interface problems, and therefore you

need to focus on these call drops. Call drops caused by Um interface problems are measured as CM33C and classified into call drops in the stable state and call drops due to handovers.

Call drops due to other causes seldom occur and are easy to locate. You need to focus on only CM334 and CM333.

You need not pay attention to call drops caused by loop back because loopback is seldom used on the network. CM33:CELL_TRAF_CH_CALL_DROPS

CM33C:CELL_TRAF_CH_UM_CALL_DROPS

CM332:CELL_TRAF_CH_CALL_DROPS_NO_MR

CM333:CELL_TRAF_CH_CALL_DROPS_ABIS_LNK_FAIL

CM334:CELL_TRAF_CH_CALL_DROPS_EQUIP_FAIL

CM335:CELL_TRAF_CH_CALL_DROPS_FORCE_HO

CM397:CELL_LOOP_START_FAIL_DROPS

CM385:CELL_LOOP_RESTORE_FAIL_DROPS

CM330:CELL_TRAF_CH_CALL_DROPS_IN_STABLE_STATE

CM331:CELL_TRAF_CH_CALL_DROPS_HO_FAIL


Types of Call Drops Caused by Um Interface Problems in Terms of KPIs

Call drops caused by Um interface problems are classified into call drops in the stable state and call drops due to handovers.

Call drops in the stable state: You need to focus on CM3300 and CM3301. In normal cases, most call drops in the stable state are measured as CM3301.

Call drops due to handovers: In normal cases, the percentage of inter-cell handovers is high. Therefore, most call drops due to handovers are measured as H3127Ca and H3128Ca.

By analyzing the percentages of various call drops, you can determine whether the call drop problem is caused by a certain reason. If the call drops of a specific type whose percentage is generally low increase, you need to focus on these call drops.

CM33C:CELL_TRAF_CH_UM_CALL_DROPS

CM330:CELL_TRAF_CH_CALL_DROPS_IN_STABLE_

STATE

CM3302:CELL_TRAF_CH_STATIC_STATE_CALL_DROPS_REL_IND

H3128Ca:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHH_TRAF_NOT_INCLUDE_DR

H3027Ca:CELL_INTRACELL_HO_FAIL_EXP_TCHF_TRAF

H3028Ca:CELL_INTRACELL_HO_FAIL_EXP_TCHH_

TRAF

H3127Ca:CELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHF_TRAF_NOT_INCLUDE_DR

CM331:CELL_TRAF_CH_CALL_DROPS_HO

_FAIL

CM3300:CELL_TRAF_CH_STATIC_STATE_CALL_DROPS_ERR_IND

CM3301:CELL_TRAF_CH_STATIC_STATE_CALL_DROPS_CONN_FAIL

H3227Ca:CELL_INTRABSC_INCELL_HO_FAIL_EXP_TCHF_TRAF

H3228Ca:CELL_INTRABSC_INCELL_HO_FAIL_EXP_TCHH_TRAF


Example: Percentages of Various Call Drops in XingtaiThe percentages of various call drops on the network in Xingtai are as follows: Call drops caused by Um interface problems takes 98.21% and call drops due to other causes

takes only 1.79%. This proportion is normal. If the percentage of call drops due to other

causes is high, for example, the percentage of CM334 (call drops due to device faults) is high,

you need to check for hardware faults and alarms. For call drops caused by Um interface problems, the percentage of call drops in the stable

state is higher than that of call drops due to handovers. For call drops in the stable state, the

percentage of call drops caused by radio link failures (M3101A and M3201A) is the highest.



Call Drop Cases




Procedure for Analyzing Call Drops Based on Various Data

Step 1: Determine the scope of the call drop problem by analyzing performance dataor CHRs. The scope of the call drop problem can be top N cells, entire network, top N cells+entire network, top N MS types, or top N subscribers.

NOTE 1: The methods for determining the scope of the call drop problem vary according to scenario. If the call drop rate increases after network swapping or upgrade, you need to compare the performance dataor CHRs before and after the network swapping or upgrade. If the call drop rate on a network is always high and cannot meet the requirement, you need only to analyze the current performance dataor CHRs.

NOTE 2: performance dataare generally used to determine whether the scope of the call drop problem is top N cells, entire network, or top N cells+entire network. If call drops occur because certain types of MSs are used or only calls of certain subscribers drop, you need to analyze CHRs.

Step 2: Analyze call drop causes based on various data. Step 3: Take required actions according to the checklist to analyze root causes of

call drops and determine how to troubleshoot call drops. NOTE: The required actions for analyzing call drops are described in the next section. Step 4: Troubleshoot call drops and evaluate the result. If the call drop problem is

not resolved, repeat step 1 through step 4.


4-3. Provide a summary report and cases

Yes

Principle for Analyzing Call Drops: Analyze Data, Provide a Conclusion, and Determine the Next Action

• You can take most required actions by using tools, which facilitate the analysis of data such as traffic statistics, CHRs, neighboring cell data, parameters, alarms, and radio frequency (RF) channel data.

• Based on the analysis result, you can determine how to troubleshoot the call drop problem. When troubleshooting the call drop problem, focus on the main cause so that the problem can be resolved as soon as possible. 4-2. Check

whether the call drop problem is solved?

4-1. Troubleshoot the call drop problem by troubleshooting the main causes first and then other causes

3-2. Provide solutions and determine how to troubleshoot the call drop problem

3-1. Take the required actions for analyzing the call drop problem and provide a conclusion or a

temporary conclusion on root causes

2. Analyze the call drop causes

1. Determine the scope of the call drop problem

No


Determining the Scope of the Call Drop Problem – Methods for determining top N cells, top N MS types, or top N subscribers

Page 13

The methods for determining top N cells, top N MS types, and top N subscribers vary according to the scenario where call drops occur. •Scenario 1: The call drop rate increases abruptly because of unknown reasons after network swapping or upgrade. Method for determining top N cells: Calculate the difference in the call drop rates and the difference in the numbers of call drops during a specified time range when the call drop KPIs deteriorate for each cell. Rank cells according to the differences in the call drop rates in descending order to obtain the top N cells with increased call drop rates and rank cells according to the differences in the numbers of call drops in descending order to obtain the top N cells with increased numbers of call drops. The methods for determining top N MS types and top N subscribers are similar to that for determining top N cells. •Scenario 2: The call drop rate in the current network does not meet the requirement all the time. Method for determining top N cells: Rank cells according to the call drop rates in descending order to obtain the top N cells with high call drop rates and rank cells by the numbers of call drops in descending order to obtain the top N cells with large numbers of call drops. The methods for determining top N MS types and top N subscribers are similar to that for determining top N cells.


Determining the Scope of the Call Drop Problem – Criteria

Top N cells: After 20% of top N cells with high call drop rates and top N cells with large numbers of call

drops are ignored, the call drop rate of the entire network improves significantly and becomes similar to

the call drop rate before the call drop KPIs deteriorate, or the call drop rate of the entire network meets

the requirement. Entire network: After 20% of top N cells with high call drop rates and top N cells with large numbers of

call drops are ignored, the call drop rate of the entire network does not improve. Top N cells+entire network: After 20% of top N cells with high call drop rates and top N cells with large

numbers of call drops are ignored, the call drop rate of the entire network improves but is still higher than

the call drop rate before the call drop KPIs deteriorate and does not meet the requirement. Top N MS types or subscribers: After 20% of top N types of MSs or 20% of top N subscribers with high

call drop rates are ignored, the call drop rate of the entire network improves significantly and becomes

similar to the call drop rate before the call drop KPIs deteriorate, or the call drop rate of the entire network

meets the requirement. NOTE: The MS compatibility problem usually occurs during network swapping. However, CHRs or data

similar to CHRs on the original network may be unavailable. In this case, you need to pay attention to

subscriber complaints and check whether subscribers complain about call drops.


Analyzing Call Drop Causes

After determining the scope of the call drop problem,

analyze the call drop causes by analyzing the following

data:

Traffic statistics

CHRs

Signaling

DT data


Analyzing Traffic Statistics By analyzing traffic statistics, you can identify call drops caused by Um interface problems (call drops in the stable state and

call drops caused by handovers) and call drops caused by device faults (call drops caused by transmission faults and

device faults). You can also further identify call drops caused by the Um interface problems such as low levels and poor

transmission quality. However, you cannot identify call drops caused by core network (CN) problems by analyzing traffic

statistics. Provide the R&D personal with the performance statistical report obtained by analyzing performance datausing tools.


Tools and Methods for Analyzing Traffic Statistics

Page 17

Tools: excel template attached and OMStar to be releasedMethod: Determine the top N cells with high call drop rates based on the call drop rates and the numbers of call drops. Calculate the call drop rate of the entire network by ignoring the call drops occur in the top N cells to determine the scope of the call drop problem. Templates for calculating the call drop rate and the percentages of various call drops: 1. Obtain the performance dataand paste the performance datain the Call Drop Measurement sheet of the attached excel template. The contents in the table head of the sheet is arranged according to the sequence specified by the PRS and you can change the sequence as required. 2. Refresh the table in the Calculate Call Drop Ratio sheet to obtain the call drop rates of cells and filter out the top N cells by using the TOP Cell Filter sheet. 3. Set filtering criteria on the Call Drop Measurement sheet and use the Call Drop Ratio&Plenty Ratio sheet to calculate the call drop rates and the percentages of various call drops.

Call drop rates and percentages of various call drops

Template for analyzing call drop data:

Template for analyzing call drop data

Call Drop(RF Cause)M3030A:Call Drops on TCH(TA) 0.00%

M3030B:Call Drops on TCH(Uplink Received Level)81.82

%M3030C:Call Drops on TCH(Downlink Received Level) 0.00%M3030D:Call Drops on TCH(Uplink and Downlink Received Level)

0.00%

M3030G:Call Drops on TCH(Uplink and Downlink FER) 0.00%M3030H:Call Drops on TCH(Uplink Quality) 0.00%M3030I:Call Drops on TCH(Downlink Quality) 9.09%M3030J:Call Drops on TCH(Uplink and Downlink Quality) 0.00%M3030K:Call Drops on TCH(Other) 9.09%


Analyzing CHRs

CHR is a call history record, which logs the detailed

information about each call.

By analyzing CHRs using the Nastar, you can identify call

drops caused by CN problems (do not affect call drop KPIs),

Um interface problems, and transmission and device faults

and further identify call drops caused by the Um interface

problems.

Call Drop Caused by the Um Interface Problems Percentage Times

Call Drops on TCH(TA) 2.17% 5

Call Drops on TCH(Uplink Received Level) 41.30% 95

Call Drops on TCH(Uplink Interference) 3.04% 7

Call Drops on TCH(Uplink Received Level Suddenly

Decrease)0.00% 0

Call Drops on TCH(Uplink Quality) 39.13% 90

Call Drops on TCH(Downlink Received Level) 2.17% 5

Call Drops on TCH(Downlink Interference) 1.30% 3

Call Drops on TCH(Downlink Quality) 10.87% 25

Call Drops on TCH(Downlink Received Level Suddenly

Decrease)0.00% 0

Call Drops on TCH(Uplink and Downlink Received

Level)0.00% 0

Call Drops on TCH(Uplink and Downlink Interference) 0.00% 0

Call Drops on TCH(Uplink and Downlink Quality) 0.00% 0


Tools and Methods for Analyzing CHRs

Page 19

Tools: Nastar, Insightsharp, and Insightsharp components. You can use the cell performance analysis function of

the Nastar to analyze CHRs and identify the causes of abnormal releases. You can use the Insightsharp to

analyze the CHRs of BSCs, top N cell groups, or top N cells to identify and sort call drop causes offline. The

Insightsharp components are developing and will be release in the near future.

By using the Insightsharp, you can filter CHRs by field to sort call drops according to causes and calculate the

percentages of various call drops. You can also manually sort call drops based on the results generated by the

Insightsharp.

See the Insightsharp’s help.


Analyzing Signaling and Single-Subscriber CHRs By analyzing signaling and single-subscriber CHRs, you can identify the call drop causes

based on the signaling procedures and measurement reports (MRs). Abis signaling can be traced by cell. That is, you can trace the Abis signaling all calls in a cell.

Single-subscriber signaling contains all information about the calls of a single subscriber. CHRs log the information about all historical calls but contain limited MRs.

By analyzing the signaling traced over the Abis interface, you can identify the cause of a call drop based on the messages related to call drops and the level and quality information in MRs.

By analyzing the single-subscriber signaling and CHRs, you can identify the call drop causes of a single subscriber.


Tools and Methods for Analyzing Signaling and Single-Subscriber CHRs

Use the Traffic Recording Review tool on the local maintenance terminal (LMT) to display the signaling of a single subscriber and analyze the signaling procedure and the level and quality information in the MRs.

Use the Insightsharp to display the CHRs of a single subscriber, the detailed call signaling, and ten MRs generated before call drops and analyze these data.

Use the PFMStudio to analyze the signaling traced over the Abis interface. Select the path where the Abis signaling file to be analyzed is saved and click RUN. The PFMStudio automatically export files with the signaling related to one call drop saved in one file. All the files are saved to the out directory in the path for saving the Abis signaling file. Click Icon Display and perform signaling analysis.


Analyzing DT Data DT data contains only the downlink information about a single subscriber.

Therefore, you can analyze the DT data together with the single-subscriber

signaling to identify the call drop causes. You can perform DTs in top N cells or top N areas to identify call drop causes.

Neighboring cell relationships

Handover parameters

Interference problems

Cross coverage

Terminal problems

DT call drops

Due to co-frequency/adjacent-frequency interference, inter-network interference, or intermodulation interference of equipment, call drops due to bad quality occur.

Due to missing configuration of neighboring cell relationships, handovers cannot be triggered in time. Due to redundant neighboring cell relationship, inappropriate handovers occur. This, then, causes call drops.

Due to inappropriate configuration of handover parameters, handovers cannot be triggered in time or inappropriate handovers occur. This, then, causes call drops.

Because some terminals do not analyze the levels and BSICs of neighboring cells in time, handovers cannot be triggered in time. This, then, causes call drops.

Due to the geographical location and terrain of the site, cross coverage is caused and then call drops occur.


Tools and Methods for Analyzing DT Data Tools: TEMS and Probe. The TEMS or Probe can play back DT data such as

level, quality, and signal noise ratio and presents the DT data explicitly on the GUI.

By analyzing the DT data, you can identify the call drop causes.

DT data can provide more downlink information such as the BA2 list than signaling

and traffic statistics.



Call Drop Cases




4-3. Provide a summary report and cases

Yes

Principle for Analyzing Call Drops: Analyze Data, Provide a Conclusion, and Determine the Next Action

• You can take most required actions by using tools, which facilitate the analysis of data such as traffic statistics, CHRs, neighboring cell data, parameters, alarms, and radio frequency (RF) channel data.

• Based on the analysis result, you can determine how to troubleshoot the call drop problem. When troubleshooting the call drop problem, focus on the main cause so that the problem can be resolved as soon as possible.

4-2. Check whether the call drop problem is solved?

4-1. Troubleshoot the call drop problem by troubleshooting the main causes first and then

other causes

3-2. Provide solutions and determine how to troubleshoot the call drop problem

3-1. Take the required actions for analyzing the call drop problem and provide a conclusion or a

temporary conclusion on root causes

2. Analyze the call drop causes

1. Determine the scope of the call drop problem

No


The causes of call drops are complicated. Currently, a checklist containing 14 check items is available for identifying call drop scopes and causes, including top N problem cells, top N causes, and combination of some causes. You are advised to perform analysis according to the checklist.


Call Drops in Top N Cells – Required Action Checklist (1)

Required Action Operation Deliverable Subsequent Action

Identify call drop causes by analyzing performance data and CHRs

Analyze performance data to determine the scope of the call drop problem and identify the call drop causes

In special scenarios such as network swapping, analyze CHRs to determine whether calls initiated by certain types of MSs or certain subscribers always drop.

1. Top N types of call drops and causes.

2. Subsequent actions to be taken.

Take required actions according to the top N types of call drops and causes.

Check RF tunnels for main and diversity faults, cross connections, and interference

Check for RF tunnel faults by referring to the Detection and Troubleshooting of GSM RF Tunnel Faults theme.

1. Check results.

2. Solutions and measures for rectifying the RF tunnel faults.

1. Rectify the RF tunnel faults.

2. Provide a summary report and cases.

Check for device faults and alarms

Check for device faults and alarms by referring to the GSM Parameters Check theme and output the check results.

1. Check results.

2. Solutions and measures for rectifying the device faults and clearing the alarms.

1. Rectify the device faults and clear the alarms.


Check all parametersCheck the reasonableness and consistency of parameter settings by referring to the GSM Parameters Check theme and output the check results.

1. Check results.

2. Solutions and measures for optimizing parameter settings.

1. Optimize parameter settings.


Check for BTS or BSC version differences and parameter differences

Check for BTS or BSC version differences and parameter differences by referring to the GSM Parameters Check theme and output the check results and impacts of the differences.

1. Check results and impacts of the differences.

2. Solutions and measures for optimizing parameter settings and BTS or BSC versions.


2. Optimize BTS or BSC versions


Check the parameters of the devices from other vendors in the boundaries of the areas served by the devices from other vendors

Check the parameter settings and versions of the devices that are from other vendors and in the boundaries of the areas served by the devices from other vendors by referring to the GSM Parameters Check theme and output the check results.

1. Inappropriate parameter settings of the devices from other vendors.

2. Solutions and measures for optimizing the parameter settings.






Check network coverage (power matching and newly deployed sites)

1. Check network coverage by analyzing and comparing DT data and output coverage evaluation result and problem areas.

2. Check power matching after network swapping by referring to the GSM Parameters Check theme and the guide to checking power matching and output the check results. Pay attention to common problems such as combiner and tower-mounted amplifier (TMA) faults.

3. After network swapping or network expansion, obtain and analyze the information about new sites, modified sites, and changed sites and the changes in RF parameter settings and output the impacts of these changes.

1. Coverage evaluation results of problem areas and solution for optimizing RF coverage.

2. Check result of power matching accuracy and solution for optimizing the power matching.

3. Analysis results of the information about new sites, removed sites, and changed sites and changes in RF parameter settings, impacts of these changes, and solution for optimizing RF coverage.

1. Optimize power matching.

2. Optimize RF coverage


Analyze neighboring relationships (for newly deployed sites and areas where Huawei devices are interconnected to devices from other vendors)

1. Analyzing neighboring relationships by referring to the GSM Neighboring Cell Optimization theme and output the analysis results.

2. After network swapping or network expansion, check whether neighboring relationships need to be adjusted by analyzing site changes and output the analysis results.

1. Analysis results of neighboring relationships, such as missing neighboring cells and redundant neighboring cells.

2. Conclusion in inheriting or adjusting neighboring relationships

3. Solutions for optimizing neighboring relationships.

1. Optimize neighboring relationships.


Analyze changes in traffic and KPIs in special scenarios (networks supporting GSM900 and DCS1800 and configured with co-BCCH)

1. Analyze the changes in traffic and KPIs and output the analysis results and the impacts of these changes.

2. In a network supporting GSM900 and DCS1800 and configured with the co-BCCH, check the difference in call drops and traffic distribution between GSM900 and DCS1800 and between the overlaid subcell and underlaid subcell.

1. Changes in traffic and KPIs and impacts of these changes.

2. Changes in traffic and KPIs in special networking scenarios such as a dual-band network and a network configured with co-BCCH and the impacts of these changes.

3. Solutions and measures.

1. For call drops caused by reasonable changes in traffic and KPIs, provide an analysis report to explain the problem objectively to the customer and provide suggestions on how to resolve the problem. For call drops caused by unreasonable changes in traffic and KPIs, troubleshoot the traffic and KPI problems.

2. Optimize traffic distribution in special scenarios such as a dual-band network and a network configured with the co-BCCH.





Check CS and PS services (their proportions and changes)

Analyze the correlation between the traffic changes in CS and PS services and the number of call drops and output the traffic changes and the impacts of the changes, including the changes in the proportions of data and CS services, change causes, and the correlation between the traffic changes in data and CS services and the number of call drops.

1. Traffic changes in CS and PS services and the impacts of the changes.


1. For call drops caused by reasonable traffic changes in CS and PS services, provide an analysis report to explain the problem objectively to the customer and provide suggestions on how to resolve the problem.

2. For call drops caused by unreasonable traffic changes in CS and PS services, troubleshoot the traffic problems.


Analyze frequencies after network expansion, deployment, or reconstruction

1. Analyze the frequencies used on the current network and evaluate the frequency replanning gain by referring to the GSM Frequency Replanning theme and output the analysis and evaluation results.

2. Analyze whether there is internal and external interference and output the analysis results.

3. After network swapping or expansion, analyze whether frequencies are inherited or replanned and output the conclusion.

1. Analysis results of the frequencies used on the current network, evaluation result of the frequency replanning gain, and solutions and measures for replanning frequencies or optimizing frequencies.

2. Interference analysis results and measures for eliminating interference.

3. Conclusion in inheriting or adjusting frequencies and solutions and measures for optimizing frequencies.

1. Replan or optimize frequencies.

2. Eliminate interference.


Check for abrupt events such as charging policy changes, weather changes, and mass gatherings

Analyze the impacts of abrupt events on call drops and output the analysis results.

1. Impacts of abrupt events on call drops.


1. For a reasonable increase in call drops caused by emergence events, prepare an analysis report to explain the problem objective to the customer and provide suggestions.

2. For an unreasonable increase in call drops caused by emergence events, troubleshoot the problem.


Check for complaints and call drops due to other causes by analyzing CHRs

1. Analyze CHRs and output top N subscribers whose calls drop, top N cells where call drops occur, top N call drop causes, and characteristics of call drop causes (especially the percentage of call drops caused by disordered serial numbers). 2. Analyze the causes of the call drops that subscribers complain by analyzing CHRs and output analysis results.

1. Top N subscribers whose calls drop, top N cells where call drops occur, top N call drop causes, and characteristics of call drop causes.




Call Drops on the Entire Network – Required Action Checklist (1)


Identify call drop causes by analyzing performance dataand CHRs

Analyze performance datato determine the scope of the call drop problem and identify the call drop causes

In special scenarios such as network swapping, analyze CHRs to determine whether calls initiated by certain types of MSs or certain subscribers always drop.

1. Top N types of call drops and causes.



Check all parametersCheck the reasonableness and consistency of parameter settings by referring to the GSM Parameters Check theme and output the check results.

1. Check results.

2. Solutions and measures for optimizing parameter settings.




Check for BTS or BSC version differences and parameter differences by referring to the GSM Parameters Check theme and output the check results and impacts of the differences.

1. Check results and impacts of the differences.

2. Solutions and measures for optimizing parameter settings and BTS or BSC versions.


2. Optimize BTS or BSC versions



1. Analyze the changes in traffic and KPIs and output the analysis results and the impacts of these changes.

2. In a network supporting GSM900 and DCS1800 and configured with the co-BCCH, check the difference in call drops and traffic distribution between GSM900 and DCS1800 and between the overlaid subcell and underlaid subcell.

1. Changes in traffic and KPIs and impacts of these changes.

2. Changes in traffic and KPIs in special networking scenarios such as a dual-band network and a network configured with co-BCCH and the impacts of these changes.


1. For call drops caused by reasonable changes in traffic and KPIs, provide an analysis report to explain the problem objectively to the customer and provide suggestions on how to resolve the problem. For call drops caused by unreasonable changes in traffic and KPIs, troubleshoot the traffic and KPI problems.

2. Optimize traffic distribution in special scenarios such as a dual-band network and a network configured with the co-BCCH.



Analyze the correlation between the traffic changes in CS and PS services and the number of call drops and output the traffic changes and the impacts of the changes, including the changes in the proportions of data and CS services, change causes, and the correlation between the traffic changes in data and CS services and the number of call drops.

1. Traffic changes in CS and PS services and the impacts of the changes.


1. For call drops caused by reasonable traffic changes in CS and PS services, provide an analysis report to explain the problem objectively to the customer and provide suggestions on how to resolve the problem.

2. For call drops caused by unreasonable traffic changes in CS and PS services, troubleshoot the traffic problems.



Call Drops on the Entire Network – Required Action Checklist (2)



1. Analyze the frequencies used on the current network and evaluate the frequency replanning gain by referring to the GSM Frequency Replanning theme and output the analysis and evaluation results.

2. Analyze whether there is internal and external interference and output the analysis results.

3. After network swapping or expansion, analyze whether frequencies are inherited or replanned and output the conclusion.

1. Analysis results of the frequencies used on the current network, evaluation result of the frequency replanning gain, and solutions and measures for replanning frequencies or optimizing frequencies.

2. Interference analysis results and measures for eliminating interference.

3. Conclusion in inheriting or adjusting frequencies and solutions and measures for optimizing frequencies.

1. Replan or optimize frequencies.

2. Eliminate interference.



Analyze the impacts of abrupt events on call drops and output the analysis results.

1. Impacts of abrupt events on call drops.


1. For a reasonable increase in call drops caused by emergence events, prepare an analysis report to explain the problem objective to the customer and provide suggestions.

2. For an unreasonable increase in call drops caused by emergence events, troubleshoot the problem.


Analyze the long-term traffic trends due to seasonal changes and subscriber number increase

Obtain the long-term trends of traffic and KPIs, analyze whether the trends are consistent with the trend of the call drop rate, and output the analysis results.

1. Correlation between the long-term trends of traffic and KPIs and the trend of the call drop rate.


1. For call drops caused by reasonable changes in traffic and environment, prepare an analysis report to explain the problem objective to the customer.

2. For call drops caused by unreasonable changes in traffic and environment, troubleshoot the problem.



1. Analyze CHRs and output top N subscribers whose calls drop, top N cells where call drops occur, top N call drop causes, and characteristics of call drop causes (especially the percentage of call drops caused by disordered serial numbers). 2. Analyze the causes of the call drops that subscribers complain by analyzing CHRs and output analysis results.

1. Top N subscribers whose calls drop, top N cells where call drops occur, top N call drop causes, and characteristics of call drop causes.




See the required action checklists for call drops in the top N cells and on the entire network.

Call Drops in Top N Cells and on the Entire Network – Required Action Checklist


Data Analysis Templates

The procedure for analyzing the call drop problem is as follows:

1. Analyze the call drop scope and causes based on various data such as traffic statistics,

signaling, DT data, alarms, parameter settings, and CHRs.

2. Take required actions to further analyze the call drop causes.

By using the following types of data analysis templates, you can quickly identify call drop

causes

and further identify the causes by taking the required actions:

1. Templates for identifying call drop causes

2. Templates for providing supplementary information for call drop analysis

The following attached excel describes the common templates for analyzing the call drop problem: Common Templates

for Analyzing the Call


Templates for Identifying Call Drop Causes There are four types of templates for identifying call drop causes:

Performance statistical analysis: 1. Templates for identifying the call drop scope (top N cells, entire network, or top N

cells+entire network) 2. Template for identifying the causes of call drops that occur in the top N cells and on the entire network

CHR analysis: 3. Templates for identifying the call drop scope (top N MS types or top N subscribers) 4. Template for identifying

the causes of call drops that occur on top N types of MSs and top N subscribers.


Templates for Providing Supplementary Information for the Call Drop Analysis – Channel and Frequency AnalysisCommon performance counters in RF tunnel and frequency analysis are: Rate of Outgoing Handovers and Incoming Handovers (100% x (Outgoing Handovers/Incoming Handovers)) Rate of Good RxLev and Bad HQI on Downlink(Downlink Receive Level Rank 5~7, and Downlink Receive Quality

Rank 6~7) Rate of Uplink-and-Downlink Imbalance(Downlink)(Uplink-and-Downlink Balance Level 1~2) Rate of Uplink-and-Downlink Imbalance(Uplink)(Uplink-and-Downlink Balance Level 10~11) Rate of Uplink Interference(Rate of Uplink Interference Band 4~5) Rx Level Difference between Main and Diversity Antenna(Average Main Level in the Customized MR-Average

Diversity Level in the Customized MR) If the scope of the call drop problem is top N cells, analyze the preceding performance counters of the top N cells. If the

scope of the call drop problem is entire network or top N cells+entire network, rank cells in the entire network by each of the

preceding performance counters to identify problem cells and analyze the problem cells on the entire network.


Templates for Providing Supplementary Information for the Call Drop Analysis – Device Fault Analysis

Common performance counters in device fault analysis are:

TRX Usability(Abnormal Condition:<100%)

TCH Availability(Abnormal Condition:<100%)

Cell Out-of-Service DuRaten(BCCH Fault)(Abnormal Condition:>0)

Rate of CHAN_ACTIV Failure(Abnormal Condition:>0%)

Traffic Volume(Abnormal Condition:=0)

Outgoing or Incoming Handover Requests(Abnormal Condition:=0)

Channel Requests(Abnormal Condition:=0)

If the scope of the call drop problem is top N cells, analyze the preceding performance counters of the top N cells. If the scope of the call drop problem is

entire network or top N cells+entire network, rank cells in the entire network by each of the preceding performance counters to identify problem cells and

analyze the problem cells on the entire network.


Templates for Providing Supplementary Information for the Call Drop Analysis – Coverage AnalysisCommon performance counters in coverage analysis are: Rate of Weak Received-Power on Downlink(Downlink Receive Level Rank 0~2) Rate of Weak Received-Power on Uplink(Uplink Receive Level Rank 0~2) Rate of Bad HQI on Downlink(Downlink Receive Quality Rank 6~7) Rate of Bad HQI on Uplink(Uplink Receive Quality Rank 6~7) Rate of MRs (Weak Coverage) Rate of MRs (Excessive Coverage)

If the scope of the call drop problem is top N cells, analyze the preceding performance counters of the top N cells. If the scope of

the call drop problem is entire network or top N cells+entire network, rank cells in the entire network by each of the preceding

performance counters to identify problem cells and analyze the problem cells on the entire network.


Templates for Providing Supplementary Information for the Call Drop Analysis – Neighboring Cell AnalysisCommon performance counters in neighboring cell analysis are: Proportion of Call Drop Rate Due to Handover Success Rate of Outgoing Internal Inter-Cell Handovers Success Rate of Incoming Internal Inter-Cell Handovers Success Rate of Outgoing External Inter-Cell Handovers Success Rate of Incoming External Inter-Cell Handovers Success Rate of Internal Intra-Cell Handover, Handover Density ((Outgoing Handovers + Incoming Handovers)/Traffic

Volume) Rate of Outgoing Handovers and Incoming Handovers (100% x (Outgoing Handovers/Incoming Handovers))

If the scope of the call drop problem is top N cells, analyze the preceding performance counters of the top N cells. If the scope of the call drop problem is entire network or top N cells+entire network, rank cells in the entire network by each of the preceding performance counters to identify problem cells and analyze the problem cells on the entire network.


Templates for Providing Supplementary Information for the Call Drop Analysis – Traffic and Abrupt Event Analysis

To analyze call drops caused by traffic changes and abrupt environment changes,

analyze the trend of the call drop rate and the following performance counters: call

drop rate, traffic volume, call setup performance counters, handover performance

counters, coverage performance counters, device status performance counters,

channel and frequency performance counters, and neighboring cell performance

counters. If the scope of the call drop problem is top N cells, analyze the preceding

performance counters of the top N cells. If the scope of the call drop problem is

entire network or top N cells+entire network, analyze both the preceding

performance counters and the trend of the call drop rate.


Templates for Providing Supplementary Information for the Call Drop Analysis – Dual-Band Network/Overlaid and Underlaid Subcell Analysis

For a dual-band or an enhanced dual-band network configured with overlaid and underlaid subcells, analyze

and compare the call drop and traffic counters of the bands and overlaid and underlaid subcells to determine

whether the call drop problem can be resolved by optimizing networking or parameter settings.


Required Actions – Check RF Tunnels (1)

Triggering conditions:

1. If call drops occur after BTS adjustment during network swapping,

network deployment, or BTS upgrades, check all the RF tunnels on the

entire network.

2. If call drops occur after routine network optimization or device

adjustment during network expansion, BTS reparenting, or site

maintenance, check the RF tunnels in the sites where network

optimization or device adjustment are performed.

For details about how to check RF tunnels, see the “1 Detection and

Troubleshooting of GSM RF Tunnel Faults:

Principle+Tools+Cases+Deliverables 20110730.PPT”.


Required Actions – Check RF Tunnels (2)

Data and Characteristics

数据源 Data Performance Data DT Data and Signaling Alarm and Log

分析模板及相关特征

Analysis templates and characteristics

[Data Analysis]

1. Template for analyzing RF tunnels and frequencies2. Template for ranking cells by Rate of Good RxLev and Bad HQI on Uplink3. Template for ranking cells by Rate of Good RxLev and Bad HQI on Downlink4. Template for ranking cells by Rate of Uplink-and-Downlink Imbalance(Downlink)5. Template for ranking cells by Uplink-and-Downlink Imbalance(Uplink)6. Template for ranking cells by Uplink Interference7. Template for ranking cells by Rx Level Difference between Main and Diversity Antenna8. Template for ranking cells by the mean signal strength difference between the serving cell and the neighboring cell

[Characteristics]

1. The difference between the receive level of the main and the receive level of the diversity is great. 2. The uplink and the downlink are imbalanced. (Proportion of uplink and downlink imbalance level 1 + Proportion of uplink and downlink imbalance level 2) > 15% (poor downlink or good uplink) or Proportion of uplink and downlink imbalance level 11 > 30% (good downlink or poor uplink)3. The proportion of interference band levels 3 to 5 is high in a specific time period or a day. 4. The proportion of call drops caused by poor HQIs is high. 5. The mean signal strength difference between the serving cell and the neighboring cell is less than 0.

[Tools]

PRS, OMStar, and DownlinkAnalyse

[Data Analysis]

1. Cross connections between cells: Perform DTs to check whether the connections between the main of a cell and the antenna of another cell are cross connection and check the order of wires.

2. Antenna misconnections between cells: Perform DTs along the direction of the major lobe in the cells under possible problem sites to check whether the BCCH of the major lobe in each cell is the same as the planned BCCH.

3. Interference caused by antenna intermodulation: Conduct the start idle timeslot test and stop idle timeslot test on the LMT during off-peak hours and compare the interference band information carried in Abis signaling before and after idle timeslots are sent. If the interference increases after idle timeslots are sent (the interference band levels increase to 3 to 5), there is interference from the antenna system of the BTS.

[Tools]

DT software and IntferBandAnalyse

[Data Analysis]

Alarm list

[Characteristics]

The voltage standing wave radio (VSWR) alarm is reported.


Required Actions – Check for Device faults and AlarmsTriggering conditions:

Check for alarms in all scenarios and first clear the alarms that are related to call

drops and affect network performance. You can temporarily ignore the alarms not

related to call drops.

Data and CharacteristicsData Performance Data Alarm and Log


[Data Analysis]

1. Template for analyzing device faults2. Template for listing carriers with device faults3. Template for identifying carriers without traffic volume or with low traffic volumes4. Template for identifying carriers not involved in any handovers or with small numbers of handovers5. Template for identifying carriers without access success or with low access success rates

[Characteristics]

1. Call drops may not be caused by Um interface problems. For example, call drops are caused by Abis interface problems.2. The call drop rate deteriorates abruptly. 3. The following items become abnormal: carrier availability, TCH availability, out-of-service durations of cells, and out-of-service ratio of cells. 4. The channel activation failure ratio is greater than 0%, which indicates that the BTS or transmission is faulty.

[Data Analysis]

1. Alarm list2. Device logs

[Characteristics]

1. Device or link fault alarms are reported.

2. The device logs record some internal alarms and assertions.

[Tools]

Alarm console, OMStar, and some maintenance tools


Required Actions – Check All Parameters (1) Triggering conditions: 1. Check all parameters on the entire network if call drops occur after the

network structure or traffic changes because of the following causes: CN

parameter adjustment, 2G or 3G service adjustment, parameter adjustment on

the entire network during network swapping, and network deployment, network

upgrades, and timer or soft parameter adjustment 2. Check all parameters for some sites in an area or at the boundaries of areas

served by the devices from other vendors if call drops occur after the network

structure or traffic changes because of the following causes: network expansion,

network reparenting, part parameter adjustment, coverage adjustment, and

adjustment of the boundaries of areas served by the devices from other vendors. 3. If the network structure or traffic does not change, check and optimize core

parameters during routine call drop optimization. If the call drop problem persists

after the core parameters are optimized, check all parameters.


Required Actions – Check All Parameters (2)

Data and CharacteristicsData Performance Data Parameter s DT Data and Signaling


[Data Analysis]

1. Template for analyzing call drop scopes

2. Template for analyzing the distribution of call drop causes

3. Template for analyzing the correlation between the trend of CS or PS service traffic and the trend of the call drop rate

[Characteristics]

The scope of the call drop problem is top N cells, entire network, or top N cells+entire network.

[Data Analysis]

1. Check and optimize parameter settings.

2. Check and optimize parameter relationships.

3. Check whether parameter settings are consistent and perform other parameter checks.

[Tools]

PFMStudio, DAMS, CME, and OMStar

[Data Analysis]

Perform DTs in the coverage of the following areas to check whether call drops are caused by inappropriate parameter settings: top N cells, boundaries of areas served by the devices from other vendors, areas where 2G/3G interoperability is allowed.

[Tools]

DT software and signaling analysis software

For details about how to check all parameters, see the “2 GSM Parameters Check: Check Rules+Tools+Cases+Deliverables 20110730.PPT”.


Required Actions – Check for Version DifferencesTriggering conditions: If call drops occur after the BSC, BTS, or MSC is upgraded, check

for version differences.

　 Data and CharacteristicsData Performance Data Parameter


[Data Analysis]

1. Template for analyzing call drop scopes

2. Template for analyzing the distribution of call drop causes

[Characteristics]

1. The scope of the call drop problem is top N cells, entire network, or top N cells+entire network and the call drop rates deteriorate immediately after the BSC, BTS, or MSC is upgraded.

2. The scope of the call drop problem is top N cells, the call drop rates deteriorate immediately after the BTS or BSC is upgraded, and the configurations of the top N cells are different from those of the cells where the call drop rates are normal.

3. The versions of the BTSs serve the top N cells are different from the versions of other BTSs.

[Data Analysis]

Output all version differences in terms of features, procedures, parameters, and default values of parameters and analyze whether the version differences affect the call drop rates.

[Characteristics]

Some version differences affect the call drop rates.


Required Actions – Analyze Neighboring Relationships (1)


1. If neighboring relationships change after network deployment, network

swapping, or network expansion, analyze neighboring relationships.

2. If network scale or subscriber distribution changes, check and optimize

neighboring relationships periodically.

3. Perform centralized neighboring cell optimization on cell clusters with poor

KPIs or in VIP regions.

4. Optimize neighboring relationships before frequency replanning.

For details about how to optimize neighboring relationships, see the

“6 GSM Neighboring Cell Optimization Principles, Tools, and

Deliverables 20110730.PPT”.


Required Actions – Analyze Neighboring Relationships (2)

　 Data and Characteristics

Data Performance Data DT Data and Signaling Parameter Other Data


[Data Analysis]

1. Template for analyzing weak coverage 2. Template for ranking cells by Rate of Weak Received-Power on Downlink 3. Template for analyzing inappropriate neighboring cells 4. Template for ranking cells by the proportions of call drops caused by handovers 5. Template for ranking cells by the handover densities 6. Template for ranking cells by the handover success rates 7. Template for ranking cells by Outgoing Handover/Incoming Handover8. GSM Cell to GSM Cell Outgoing Handover Measurement

[Characteristics]

1. The call drop rates in the neighboring cells of some cells are high. 2. The handover success rates in some cells are low because of inappropriate neighboring relationships.3. Large numbers of handovers or only small numbers of handovers occur in some cells. 4. The proportion of call drops caused by low levels is high for some cells. The low-level problem may be caused by weak coverage due to missing neighboring cells. 5. The differences between the numbers of outgoing handovers and the numbers of incoming handovers are great for some cells.

[Tools]

Nastar and CellOpt

[Data Analysis]

Perform DTs in top N cells, on the entire network, or in the boundaries of areas served by the devices from other vendors to check for cross coverage and troubleshoot the cross coverage.

[Characteristics]

1. Problems such as missing neighboring cells, cross coverage, and inappropriate parameter settings exist.

2. After calls drop in a cell, MSs access the network from other cells because some neighboring cells are missing or handovers are triggered with delays. This is caused by inappropriate parameter settings.

3. Cross coverage occurs. That is, the signal of the serving cell is too strong. As a result, handovers fail to be triggered when MSs move to other cells.

[Tools]


[Data Analysis]

Handover parameters: Check and optimize handover parameters when neighboring relationships are inappropriate or large numbers of handovers or only small numbers of handovers occur.

[Characteristics]

Handover parameter settings are inappropriate or some other configurations need to be optimized.

[Data Analysis]

1. Analyze MRs to identify missing and redundant neighboring cells.

2. Analyze CHRs to check whether an MS accesses the network from the same cell where the previous call drops. If the MS accesses the network from a different cell, some neighboring cells are not configured or handovers are triggered with delays.

3. Analyze CHRs to check whether the last handover before the call drops is successful. If the last handover fails, the following problems occur: co-BSIC problem, weak coverage, interference, resource congestion, or link faults.

[Tools]

Nastar and CellOpt


Required Actions – Check the Parameters of the Other Vendors’ Devices in the Boundaries of HW and Other Vendors’ DevicesTriggering conditions: 1. If network swapping or network deployment involves the boundaries of the areas served by the

devices from other vendors, check the parameters of the devices from other vendors before network swapping or network deployment.

2. If the call drop rates in the boundaries of the areas served by the devices from other vendors are abnormal, check the parameters of the devices from other vendors.


Data Performance DataDT Data and Signaling

Parameter


[Data Analysis]

1. Template for analyzing weak coverage (top N cells, top N cells+entire network)2. Template for ranking cells by Rate of Weak Received-Power on Downlink (entire network, top N cells+entire network)3. Template for analyzing inappropriate neighboring cells (top N cells, top N cells+entire network)4. Template for ranking cells by the proportions of call drops caused by handovers (entire network, top N cells+entire network)5. Template for ranking cells by the handover densities (entire network, top N cells+entire network)6. Template for ranking cells by the handover success rates (entire network, top N cells+entire network)7. Template for ranking cells by Outgoing Handover/Incoming Handover (entire network, top N cells+entire network)8. GSM Cell to GSM Cell Outgoing Handover Measurement

[Characteristics]

1. The call drop rates deteriorate in the boundaries of the areas served by the devices from other vendors. 2. The differences between the numbers of outgoing handovers and the numbers of incoming handovers are great in the boundaries of the areas served by the devices from other vendors.3. The outgoing handover success rates are low and the incoming handover success rates are normal in the boundaries of the areas served by the devices from other vendors.4. The outgoing handover success rates and the incoming handover success rates are low in the boundaries of the areas served by the devices from other vendors.

[Data Analysis]

Perform DTs in the boundaries of the areas served by the devices from other vendors to check whether call drops are caused by inappropriate parameter settings.

[Tools]


[Data Analysis]

Analyze Huawei parameters and the parameters of the devices from other vendors in terms of handovers, camp-on, neighboring cells, configurations, timers to check whether the call drop rates are affected by inappropriate parameter settings.

For details about how to check all parameters, see the “2 GSM Parameters Check: Check Rules+Tools+Cases+Deliverables 20110730.PPT”.


Required Actions – Check Network Coverage (1)


1. Check network coverage if network structure and RF parameters such as power and

antenna configurations are adjusted during network swapping, network deployment, or

network expansion and compare the network coverage before and after the network

swapping, network deployment, or network expansion.

2. If the call drop problem persists after the RF tunnel faults are rectified, inappropriate

parameter settings are modified, and neighboring cells are optimized, check the network

coverage thoroughly and troubleshoot the coverage problems.

3. During routine network maintenance, check network coverage periodically.


Required Actions – Check Network Coverage (2)

　 Data and CharacteristicsData Performance Data DT Data and Signaling Parameter Other Data


[Data Analysis]

1. Template for analyzing weak coverage

2. Template for ranking cells by Rate of Weak Received-Power on Downlink

3. Template for ranking cells by Rate of Weak Received-Power on Uplink

4. Template for ranking cells by Rate of Bad HQI on Downlink

5. Template for ranking cells by Rate of Bad HQI on Uplink

6. Template for ranking cells by Rate of MRs (Weak Coverage)

7. Template for ranking cells by Rate of MRs (Excessive Coverage)


[Characteristics]

1. A large number of call drops are caused by low levels.

2. The call drop rate increases and traffic volume decreases after network adjustment operations such as network swapping, network deployment, network expansion, and RF optimization.

3. The proportions of weak coverage or cross coverage MRs are high for some cells.

[Data Analysis]

1. Perform DTs on the entire network or in top N cells and analyze the DT data.

2. Perform DTs in special scenarios such as VIP regions, indoor environment, campus, residential areas, and highways or perform DTs in specified areas.

3. Perform coverage DTs in areas where subscribers complain about call drops.

4. Analyze CHRs to identify the cell with the highest call drop rate and the subscriber with the highest call drop rate in that cell. Then, perform DTs in the areas where the call drop problem is serve based on the feedback from the subscriber.

[Characteristics]

1. Call drops caused by abnormal handovers and low levels occurs because the following problems occur: weak coverage, coverage hole, cross coverage, downlink interference, missing neighboring cells, or inappropriate settings of handover parameters.

2. The antennas or combiners may be faulty or power mismatch occurs if the coverage of a cell or a site shrinks after network swapping.

NOTE

It is difficult to identify the coverage shrink caused by power matching problems and combiner faults by checking RF tunnels. Therefore, you need to focus on power and combiners if the RF tunnel check does not show any problems but the coverage shrinks.

[Data Analysis]

Check the settings of power, TA gain, and antenna parameters.

After network swapping, check parameter consistency and test power matching based on the typical power setting on the original network.

[Data Analysis]

1. Analyze CHRs to identify the cell with the highest call drop rate and the subscriber with the highest call drop rate in the problem cell and perform DTs in the areas where the call drop problem is serve based on the feedback from the subscriber.

2. Analyze MRs containing information such as levels, TA values, and quality information to identify coverage problems.

If the TA value is small but the level is high, power is wasted.

If the TA value is small and the level is low, weak coverage in buildings or RF tunnel faults occur.

If the TA value is large but the level is low, weak coverage occurs.

If the TA value is large and the level is high, cross coverage occurs.


Required Actions – Analyze Changes in Traffic and KPIs in Special Scenarios


Analyze changes in traffic and KPIs in dual-band networks,

enhanced dual-band networks, and concentric networks.


Data Performance Data


[Data Analysis]

1. Template for comparing call drop trends between the two bands in a dual-band network or an enhanced dual-band network.

2. Template for comparing call drop trends between the underlaid subcell and the overlaid subcell in a concentric network.

[Characteristics]

1. The call drop performance differs greatly between the two bands in a dual-band network or an enhanced dual-band network.

2. The call drop performance differs greatly between the underlaid subcell and the overlaid subcell in a concentric network.


Required Actions – Check CS and PS services (Proportions and Changes)

Triggering conditions: If the call drop rate increases during a period and the increasing trend of

the call drop rate is correlated with the increasing trends of CS and PS

services, check the proportions of and changes in CS and PS services.




[Data Analysis]


[Characteristics]

The call drop rate increases during a period and the increasing trend of the call drop rate is correlated with the increasing trends of CS and PS services.


Required Actions – Analyze Frequencies (1)


After the current network operates for a period, the original frequency planning is not

applicable to the current network and the internal interference affects the overall network

performance because of network changes such as increasing subscribers, traffic transfer,

network expansion, site relocation, repeater addition, and coverage adjustment.


Required Actions – Analyze Frequencies (2)

For details about how to replan frequencies, see the “5 GSM Frequency Replanning Process, Principles, Tools, and Deliverables 20110730.PPT”.

　 Data and CharacteristicsData Performance Data Other Data

Analysis templates

and characteristics

[Data Analysis]

1. Template for analyzing RF tunnels and frequencies

2. Template for ranking cells by Rate of Good RxLev and Bad HQI on Uplink

3. Template for ranking cells by Rate of Good RxLev and Bad HQI on Downlink

4. Template for ranking cells by Rate of Uplink-and-Downlink Imbalance(Downlink)

5. Template for ranking cells by Uplink-and-Downlink Imbalance(Uplink)

6. Template for ranking cells by Uplink Interference

[Characteristics]

1. The performance counters related to call drops change with the traffic volume and deteriorate

significantly during peak hours.

2. The proportion of call drops caused by poor quality during peak hours is high.

3. The proportion of HQIs 6 and 7 increases significantly during peak hours.

4. During peak hours, the proportion of interference band levels 4 and 5 is high and there is no

external interference.

[Data Analysis]

Analyze MRs and output the interference

matrix.

[Characteristics]

There are a lot of intra-frequency and inter-

frequency neighboring cells generating great

interference signals.

[Tools]

CellOpt


Required Actions – Check for Abrupt EventsTriggering conditions: If the call drop rate increases abruptly and the call drops are not caused by external

interference or network adjustment such as device faults, parameter modification, and

network upgrades, check for abrupt events that may affect coverage or traffic, such as

charging policy changes, weather changes, mass gatherings, and returning of college

students to campuses.

　 Data and CharacteristicsData Performance Data


[Data Analysis]


[Characteristics]

The call drop rate increases abruptly and the time and location of the call drop rate problem is the consistent with those of an abrupt event that affects coverage and traffic, such as charging policy changes, weather changes, mass gatherings, or returning of college students to campuses.


Required Actions – Analyze the Long-Term Traffic or KPI TrendsTriggering conditions:

If the call drop rate increases slowly with seasonal traffic changes, analyze the long-term

traffic or KPI trends to determine whether the increase in the call drop rate is acceptable.




[Data Analysis]


[Characteristics]

The call drop rate increases slowly with seasonal changes in traffic and increase in the subscriber number.


Required Actions – Check for Complaints and Call Drops Caused by Other Causes by Analyzing CHRs

Triggering conditions: 1. When tracing and analyzing the signaling of VIP subscribers to ensure the service quality,

check for complaints and call drops caused by other causes. 2. Subscribers complain about call drops. 3. When analyzing call drop records thoroughly, check for complaints and call drops caused by

other causes. Currently, no tool is available for analyzing call drop records thoroughly and therefore engineers must be highly qualified.

4. Call drops due to other causes refer to abnormal call releases due to causes other than Um interface problems and are classified into call drops due to disordered serial numbers, call drops due to sudden downlink failures, and call drops due to BSC-initiated releases. The call drops due to other causes can be identified by analyzing CHRs traffic statistics, and signaling.


Data Other Data


[Data Analysis]

Obtain the following information by analyzing CHRs: 1. Detailed cause values of call drops2. Top N cells with high call drop rates3. Top N subscribers with high call drop rates 4. CHRs of VIP subscribers 5. CHRs of subscribers who complain about call drops


Required Actions

The attached excel provides the triggering

conditions, templates, data, and characteristics

related to the required actions.

µô»°¹æ¶¨¶¯×÷ÏêÏ¸ËµÃ÷.xlsx


Checking for Call Drops Not Caused by Um Interface Problems

Focus on the call drops measured as CM333 and CM334 and ignore

the call drops caused by failures to start loopback and failures to return

to normal calls from loopback because BSC or BTS local switching is

disabled in most cases. Determine whether the Abis interface links are faulty by analyzing the

proportion and number of the call drops measured by CM333. If call

drops occur because the RSL is disconnected, they are measured as

CM333. Determine whether some devices are faulty by analyzing the

proportion and number of the call drops measured by CM334. The call

drops caused by the following operations are measured as CM334:

Enable TRX mutual aid; dynamically modify cell attributes, TRX

frequencies, or TRX FH data; dynamically delete cells or TRXs;

blocking cells, TRXs, or channels The call drops caused by software errors are also measured as

CM334. If the number of call drops measured as CM333 and CM334

increases, check for and clear related alarms. Check for and rectify

transmission and hardware faults onsite if necessary.

Alarm ID Alarm Name1000 LAPD_OML Fault Alarm

11270Transmission LAPD Link

Interrupt Alarm11278 E1/T1 Local Alarm11280 E1/T1 Remote Alarm

20081Loss of E1/T1 Signals

Alarm(LOS)

20082Loss of E1/T1 Frames

Alarm(LOF)2204 TRX Commnunication Alarm4414 TRX VSWR Alarm3606 DRU Hardware Alarm


Identifying and Troubleshooting Call Drops Due to Other Causes

• Call drops due to other causes refer to abnormal call releases due to causes other than Um interface problems and are classified into call drops due to disordered serial numbers, call drops due to sudden downlink failures, and call drops due to BSC-initiated releases. Such call drops can be identified by analyzing CHRs, traffic statistics, and signaling.

• BSC-initiated releases are generally caused by transmission faults, hardware faults, resource faults, or resource insufficiency. The call drops due to BSC-initiated releases can be identified by CM333 or CM334, or BSC Release in CHRs and seldom occur on the network. If such call drops count for more than 5% of the total call drops, troubleshoot them by rectifying transmission and hardware faults, resolving resource problems, and clearing related alarms.• Call drops due to disordered uplink serial numbers, call drops due to sudden downlink failures, and call drops due to sudden level decreases can be identified by analyzing the traffic statistics, CHRs, and signaling. The possible root causes for such call drops include signaling interference, intermodulation interference between MSs, and subscriber behaviors such as MS power-off.

• The inter-frequency intermodulation interference is the root cause for the call drops due to disordered serial numbers and call drops due to sudden downlink failures. You can reduce the probability of intermodulation interference by taking the following measures:

1. Enable dummy bit randomization2. Enable Flex Tsc in limited areas3. Enable encryption4. Adjust ARFCNs

Call drops due to disordered serial numbers

Call drops due to sudden downlink failures

Call drops due to sudden level decreases

Call drops due to transmission faults

Call drops due to other causes

Signaling for call drops due to sudden downlink failures and sudden level decreases


Common Measures for Troubleshooting Call Drops

To improve the network quality, be meticulous in rectifying hardware faults, solving antenna problems, eliminating interference, planning frequencies, and optimizing neighboring cells.

Interference is a direct reason for call drops over the Um interface. With the increase in traffic volume, especially the rapid increase in data traffic volume, interference increases in the same frequency reuse pattern. Therefore, decreasing interference can decrease the number of call drops.

Common measures are as follows: 1. Optimize power control parameters. For details about how to set

these parameters, refer to the related documents at http://support.huawei.com.

2. Perform PS uplink power control to decrease the impact of PS services on CS services. This measure may improve CS counters but deteriorate PS counters to some extent.

3. Disable intra-cell handovers.4. Enable the PS DTX function to decrease the interference to PS

services and therefore decrease the number of call drops.5. Adjust traffic distribution on a dual-band network to ensure that the

two bands share the traffic properly. 6. Enable the no downlink MR handover feature to ensure that

handovers can be performed when no downlink MR is available to prevent calls from being released abnormally. This measure decreases the number of call drops to some extent.

7. Ensure that the number of static PDCHs is not greater than that before the network swapping.



Call Drop Cases




Case 1 – Impact of Parameter Settings of Other Vendors' Equipment on Call Drops

Problem AnalysisStep 1: Determine the scope of the call drop problem. According to the analysis of

traffic statistics, the call drop problem occurs on the entire network and in top N

cells, most of which are in the boundaries of the areas served by the devices from

other vendors

Step 2: Analyze the call drop causes. According to the analysis of traffic statistics,

most call drops are caused low levels over the Um interface.

Overview

After network swapping at an O site in country S the call drop rate increases and does

not meet the requirement. This problem is caused by weak coverage and inappropriate

parameter settings of the equipment from a vendor other than Huawei.


Required Action Data Analysis Result Conclusion


The call drop problem occurs in few cells. 　

Check for device faults and alarms The call drop problem occurs in few cells. 　

Check all parameters Acceptable 　


N/A 　


Traffic statistics: Most top N cells are in the boundaries of the areas served by the devices from other vendors.DT data: MSs are handed over to Huawei cells even if the levels in the cells served by the devices from other vendors are high.

The handover parameter settings of the devices from other vendors are inappropriate. As a result, MSs are likely to be handed over from the cells served by the devices from other vendors to Huawei cells due to high TA values or low levels. In this case, there is a high probability of call drops.


Acceptable 　


Traffic statistics: The proportion of cells with low uplink levels is high. DT data: Weak coverage occurs.

Serious weak coverage occurs because the antenna tilts are large at some sites.


N/A 　


This required action is not taken. 　










Step 3: Take required actions.



The following figure shows the troubleshooting measures and the trend of the call drop rate. After the coverage and the handover parameter settings of the devices from other vendors are adjusted, the call drop rate decreases significantly.

Step 4: Troubleshoot call drops and evaluate the result. Required Action Conclusion Solution Effect Evaluation


The levels of the main and diversity are different for some cells.

Rectify the RF tunnel fault. The call drop rate decreases.

Check for device faults and alarms Some cells report device fault alarms. Rectify the device faults. The call drop rate decreases.


The handover parameter settings of the devices from other vendors are inappropriate. As a result, many calls drop because of low levels after MSs are handed over from the cells served by the devices from other vendors to Huawei cells.

Adjust the handover parameter settings of the devices from other vendors.

The call drop rate in the top N cells in the boundaries of the areas served by the devices from other vendors becomes normal.


Serious weak coverage occurs because the antenna tilts are large at some sites.

Adjust the antenna tilts. The number of call drops due to low levels decreases and the call drop rate becomes normal.


Case 2 – Impact of Traffic Sharing on a Dual-Band Network on Call Drops OverviewAfter network swapping, network expansion, network deployment, or UMTS900 refarming at a PT site in country

P, the call drop rate does not meet the requirement. The analysis shows that the call drop rates are different

between GSM900 and DCS1800 and the handover parameter settings are inappropriate. The call drop rate

decreases significantly after the traffic on GSM900 and DCS1800 is balanced by adjusting parameter settings.

Problem Analysis

Step 1: Determine the scope of the call drop problem. According to the analysis

of traffic statistics, the call drop problem occurs on the entire network and in top N

cells, most of which work on GSM900.

Step 2: Analyze the call drop causes. According to the analysis of traffic

statistics, most call drops are caused by Um interface problems due to high levels

and poor quality.


Case 2 – Impact of Traffic Sharing on a Dual-Band Network on Call Drops

Required Action Data Analysis Result Conclusion

Check all parametersCalls are difficult to hand over from GSM900 to DCS1800 because some parameters such as Inter-layer HO Hysteresis are set inappropriately.

After network swapping, network expansion, network deployment, or UMTS900 refarming, the call drop rates differ greatly between GSM900 and DCS1800 due to inappropriate parameter settings.


Traffic statistics: The proportion of call drops due to high levels and poor quality is high. DT data: The downlink interference is strong.


Traffic statistics: The receive quality and call drop rate differ greatly between GSM900 and DCS1800. In addition, the proportion of call drops due to high levels and poor quality is high for cells working on GSM900.DT data: The downlink interference is strong in cells working on GSM900.

Step 3: Take required actions.


Case 2 – Impact of Traffic Sharing on a Dual-Band Network on Call DropsStep 4: Troubleshoot call drops and evaluate the result.

Required Action Conclusion Solution Effect Evaluation

Check all parameters

After network swapping, network expansion, network deployment, or UMTS900 refarming, the call drop rates in the cells working on GSM900 increase significantly because of heavy load and strong interference caused by inappropriate parameter settings.

Transfer some traffic from GSM900 to DCS1800 by adjusting the settings of parameters such as Inter-layer HO Hysteresis.

The call drop rate decreases significantly after the parameter settings are adjusted. See the following figure.




Case 3 – Impact of Co-BCCH Traffic Sharing on Call Drops OverviewAfter network swapping at a GP site in country B, the Minutes per Drop (MPD) performance does not meet the

requirement. Most calls access the overlaid subcell where the level is low, which affects the overall MPD

performance. After the parameters related to assignment and handovers between the overlaid subcell and the

underlaid subcell are modified, the traffic is shared properly between the overlaid subcell and the underlaid

subcell and therefore the overall MPD performance improves significantly.

Problem Analysis


of traffic statistics, the call drop problem occurs in top N cells and most top N cells

are the overlaid subcells.


statistics, most call drops are caused low levels over the Um interface.


Case 3 – Impact of Co-BCCH Traffic Sharing on Call DropsStep 3: Take required actions. Step 4: Troubleshoot call drops

and evaluate the result. Required Action Data Analysis Result Conclusion Solution Effect Evaluation


1. The traffic in the underlaid subcell is heavier than that in the overlaid subcell because the settings of the parameters related to assignment and handovers between the overlaid subcell and the underlaid subcell are inappropriate. 2. The PDCH configuration on the current network is inconsistent with that on the original network.

1. The MPD performance deteriorates because a large number of calls access the overlaid subcell where the signal level is low.2. PS services affect the normal access of CS services because the PDCH configuration on the current network is inconsistent with that on the original network.

1. Adjust the settings of the parameters related to assignment and handovers between the overlaid subcell and the underlaid subcell to balance the traffic between the overlaid subcell and the underlaid subcell. 2. Adjust the PDCH configuration on the current network.

The overall MPD performance improves significantly. Analyze changes in traffic

and KPIs in special scenarios (networks supporting GSM900 and DCS1800 and configured with co-BCCH)

Traffic statistics: According to the KPI and the traffic in the overlaid subcell and underlaid subcell, the MPD performance in the overlaid subcell is better than that in the underlaid subcell.DT data: According to the signaling, the proportion call drops due to low levels is high in the overlaid subcell.


Case 4 – Impact of Seasonal Changes on Call Drops OverviewAfter network swapping at a Telnor site in country N, the MPD performance of multiple clusters does not meet

the requirement. After a series of optimization and adjustment operations, the MPD performance of these

clusters improves to some extent but still does not reach the benchmark. According to the analysis of long-term

traffic during past years, the traffic and MPD performance varies significantly with season. In summers, the

overall MPD performance deteriorates significantly. After the network swapping, the MPD performance of some

clusters is not worse than the MPD performance during the same periods in the past years but still does not

reach the benchmark.

Problem Analysis


of traffic statistics, the call drop problem occurs in top N cells and on the entire

network.


statistics, most call drops are caused by Um interface problems.


Case 4 – Impact of Seasonal Changes on Call Drops

Step 3: Take required actions. After a series of optimization and adjustment operations such as RF tunnel optimization, parameter setting adjustment, neighboring cell optimization, and coverage optimization, the MPD performance of some clusters improves to some extent but still does not reach the benchmark. According to the analysis of long-term traffic during past years, the traffic and MPD performance varies significantly with season. In summers, the overall MPD performance deteriorates significantly. After the network swapping, the MPD performance of some clusters is not worse than the MPD performance during the same periods in the past years but still does not reach the benchmark.

Step 4: Troubleshoot call drops and evaluate the result. Seasonal changes can bring changes in radio environment and traffic and therefore affect call drops significantly in many regions. For example, thunderstorms and leafy trees in summers bring changes in radio environment. The season when the network swapping is verified is different from the season when the benchmark is defined. Therefore, explain the impact of seasonal changes on call drops to the customer objectively. NOTEThe MPD performance deterioration at the Telenor site in country N is caused by multiple causes and the season factor is only one of them.


Case 5 – Call Drop Troubleshooting in a Typical Area

OverviewAt a site of Daqing branch of China Mobile around the Longfeng expressway bridge, the call drop rate is high.

After DTs, problem analysis, and adjustment operations, the call drop rate decreases significantly.

Problem Analysis

Step 1: Determine the scope of the call drop problem. The call drop problem

occurs in the area around the Longfeng expressway bridge.




Case 5 – Call Drop Troubleshooting in a Typical AreaStep 3: Take required actions.

Step 4: Troubleshoot call drops and evaluate the result.

Required Action Data Analysis Result Conclusion Solution Effect Evaluation


Acceptable 　　　

Check for device faults and alarms Acceptable 　　　


Traffic statistics: Most call drops are caused low levels over the Um interface.

DT data: No primary network coverage is available and therefore the network coverage is chaotic. As a result, calls are handed over randomly between cells, interference is strong, and the network quality is poor.

The Longfeng expressway bridge runs through a wetland preservation area, where no primary network coverage is available and therefore the network coverage is chaotic. As a result, calls are handed over randomly between cells, interference is strong, and the network quality is poor. The DT before optimization operations shows that the network quality is poor and handovers are performed frequently.

Determine the cells providing primary network coverage, optimize neighboring relationships, optimize frequencies, and adjust parameter settings.

The call drop rate in the problem area decreases significantly. The following figures show the receive quality before and after optimization.





Case 6 – Call Drops Due to Inappropriate Parameter Settings

OverviewThe call drop rate in a cell is high because calls are likely to drop after being handed over to the cell from cells

served by another BSC. This problem is caused by inappropriate settings of inter-BSC handover parameters.

Problem Analysis


occurs in top N cells.




Case 6 – Call Drops Due to Inappropriate Parameter Settings

Step 3: Take required actions. Step 4: Troubleshoot call drops and evaluate the result.

Required Action Data Analysis Result Conclusion SolutionEffect Evaluation

Check all parameters Traffic statistics: Most call drops are caused low levels over the Um interface.

DT data: A call initiated in cell A is handed over to cell B where the level is low. As a result, the call drops after the handover. According to the moving direction of the DT car, the call should be handed over to cell C where the level is higher than that in cell B.

Parameters: Cell A and cell C are served by the same BSC and cell B is served by another BSC. For cells served by the same BSC, Inter-layer HO Threshold is set to 63 and bit 14 of the 16-bit priority is set to 1. For the neighboring cells served by another BSC, Inter-layer HO Threshold is set to 25. In this case, if the level is greater than the sum of Inter-layer HO Threshold and HO Hysteresis, bit 14 of the 16-bit priority is set to 0. On the current network, if the level of a neighboring cell served by another BSC is greater than –82 dBm, the neighboring cell has a higher priority than the neighboring cells served by the same BSC as the serving cell. As a result, calls in the serving cell are first handed over to the neighboring cell served by another BSC.

On the current network, if the level of a neighboring cell under another BSC is greater than –82 dBm, this neighboring cell has a higher priority than the neighboring cells served by the same BSC as the serving cell. As a result, calls in the serving cell are first handed over to the neighboring cell served by another BSC. This handover mechanism is inappropriate.

Adjust the setting of Inter-layer HO Threshold for the neighboring cells served by another BSC.

The call drop rate becomes normal.




Case 7 – Call Drops Due to Cross Coverage

OverviewThe call drop rate in a cell is high and the proportion of call drops due to low levels is high. This problem is caused by cross coverage. If cross coverage occurs, calls are not handed over in time and therefore drop when MSs move to street corners.

Problem Analysis






Case 7 – Call Drops Due to Cross CoverageStep 3: Take required actions. Step 4: Troubleshoot call drops

and evaluate the result.





Check all parameters Acceptable 　　　



DT data: A call in cell A is not handed over to cell B when the MS is moving to a street corner. After the MS passes through the street corner, the call drops because the level decreases and the network quality becomes poor.

The call is not handed over to cell B in time because cross coverage occurs in cell A.

Adjust the antenna tile and azimuth of cell A to control the coverage.

The call drop rate becomes normal. Check network coverage (power matching and

newly deployed sites)


Case 8 – Call Drops Due to Missing Neighboring Cells

OverviewThe call drop rate in a cell is high and the proportion of call drops due to low levels is high. This problem is caused by missing neighboring cells.

Problem Analysis

Step 1: Determine the scope of the call drop problem. The call drop

problem occurs in top N cells.




Case 8 – Call Drops Due to Missing Neighboring CellsStep 3: Take required actions.

Step 4: Troubleshoot call drops and evaluate the result.

Required Action Data Analysis Result Conclusion Solution Effect Evaluation




Check all parameters Acceptable 　　　



DT data: After the test MS in cell A passes through the corner of the street, the network quality becomes poor. The call initiated by the test MS fails to be handed over to cell B because cell B is not configured as a neighboring cell of cell A and therefore drops. After the call drops, the test MS initiates another call and accesses cell B.

The call fails to be handed over from cell A to cell B because cell B is not configured as a neighboring cell of cell A and therefore drops.

Add a neighboring relationship between cell A and cell B.

The call drop rate becomes normal.

See the following figure.



Case 9 – Call Drops Due to Interference

OverviewThe call drop rate in a cell is high. Because of uplink interference, calls in the cell are likely to drop or be handed over to neighboring cells and then drop due to low levels in the neighboring cells. The call drop rate becomes normal after the ARFCNs of the cell are changed.

Problem AnalysisStep 1: Determine the scope of the call drop problem. The call drop problem occurs in top N cells. Step 2: Analyze the call drop causes. According to the analysis of traffic statistics, most call drops are caused by Um interface problems due to the high uplink level but poor uplink quality in the problem cell and low downlink levels in the neighboring cells.

Step 3: Take required actions.Most call drops are caused by Um interface problems due to the high uplink level but poor uplink quality in the problem cell and low downlink levels in the neighboring cells. In addition, uplink interference is strong in the cell and reverse handovers occur frequently on carrier A in the cell. Because of the uplink interference on carrier A in the cell, calls in the cell are likely to drop or be handed over to neighboring cells and then drop due to low levels in the neighboring cells. Step 4: Troubleshoot call drops and evaluate the result. The call drop rate becomes normal after the ARFCN of carrier A is changed to an ARFCN without interference.


Case 10 – High Call Drop Rate Due to BTS Upgrade OverviewAfter all the BTSs are upgraded from BTS3012 V100R008C11B325 to V100R008C12SP26 at a site in country I,

the call drop rates of some BSCs increase because the default values of Second-Level Filter are different

between the two BTS versions. The call drop rates become normal after the default value of Second-Level Filter

in BTS3012 V100R008C12SP26 is changed to 200 kbit/s.

Problem AnalysisStep 1: Determine the scope of the call drop problem. According to the analysis of traffic statistics, the call drop problem occurs on most BSCs in the entire network.Step 2: Analyze the call drop causes. According to the analysis of traffic statistics, most call drops are caused by Um interface problems due to high levels and poor quality. Step 3: Take required actions. The call drop rates increase after the BTS upgrade. Therefore, check whether the call drop rate problem is caused by the differences in BTS versions. The default values of Second-Level Filter are different between the two BTS versions. BTS3012 V100R008C12SP26: 260 kbit/sBTS3012 V100R008C11B325: 200 kbit/sIn tight frequency reuse pattern, uplink interference increases if the bandwidth increases from 200 kbit/s to 260 kbit/s, which increases the call drop rates.Step 4: Troubleshoot call drops and evaluate the result. The call drop rates become normal after the default value of Second-Level Filter in BTS3012 V100R008C12SP26 is changed to 200 kbit/s.


Case 11 – Call Drops Due to Coverage Changes Caused by Addition of Combiners

OverviewAfter network swapping at site A, the call drop rates are high in the cells covering two tunnels. After the network swapping, the network coverage decreases because some combiners are added to BTSs. As a result, the call drop rates increase. After the power is adjusted, the call drop rates become normal.

Problem Analysis







Check for device faults and alarms


Check all parameters Acceptable 　　　Analyze neighboring relationships (for newly deployed sites and areas where Huawei devices are interconnected to devices from other vendors)



Some combiners are added to BTSs, but the power of the BTSs is not increased.

After the network swapping, some combiners are added to BTSs but the power of the BTSs is not increased. As a result, the network coverage becomes weak.

Increase the power of the BTSs to which combiners are added.

The network coverage and call drop rates become normal.



DT data: The network coverage becomes weak after the network swapping.

Case 11 – Call Drops Due to Coverage Changes Caused by Addition of Combiners

Step 3: Take required actions. Step 4: Troubleshoot call drops and evaluate the result.


Complaint About Call Drops on the GSM Network in Chengdu Overview At 10:38 on November 12, 2010, one CDMA subscriber in F5 building of Huawei R&D Center in Shenzhen

called a GSM subscriber in Chengdu. The call dropped.

According to the analysis of CDMA CHRs, the call is released by the MSC on the CDMA network.

Cause Value of a Call Release

Meaning of the Cause Value

Telephone Number of the Calling/Called Party

Access Time (Precise to Second)

Access Time (Precise to Millisecond)

Call Duration

Call Flag

272 MSC_REL_NORMAL_CLR(The MSC releases a call normally.)

1528101**** 2010-11-12 10:38 960 163770 0

According to the analysis of GSM CHRs, the call is released with the

cause value "Sequence error". As a result, the call is released by the

MSC on the CDMA network.


Introduction to Three Network Optimization Tools

Evaluation of Working Efficiency of the Tools

Used to Take Required Actions for Call Drop Analysis


Three Network Optimization Tools

A lot of persons, equipment, and time are required for DTs. A lot of work is involved to replan the frequencies of the

entire network. KPIs and subscriber experience cannot be closely

integrated. VIP subscribers cannot be monitored. It is difficult to analyze the complaints and assumptions

usually used in locating problems. Reports are generated inefficiently and cannot be combined

with concrete scenarios. A lot of persons are involved and it is difficult to manage

parameters.

Network Optimization

Nastar PRS DAMS

Three Network Optimization Tools

Network optimization: Network

optimization involves a lot of manual

analysis. This consumes not only labors

and time, but also introduces risks.

Tool application: Currently, three network

optimization tools can be used in basic

network optimization analysis, including

TOP cell filtering, neighboring cell

optimization, and frequency optimization.

Tool deployment: You need to purchase a

server. Ensure that the data to be

analyzed by the tools are MRs and CHRs.

In addition, you need to add SAUs for the

BSC because a lot of data is involved.


Support Capability of Three Network Optimization Tools

Tool Main Feature V9R8C12SP21 V9R8C12SP23 V9R11C00

Nastar

Neighboring cell analysis O O O

Coverage analysis O O O

Frequency analysis O O O

Assisted analysis of complaints O O O

VIP KPI analysis O O O

PRS Report system O O O

DAMS Data management system O O O

Four Main

Functions

Network Monitoring Network KPIs + Top N Cells + Top N TRXs

RF Optimization Frequency Optimization + Neighboring Cell Optimization + Interference Analysis + Overlay Analysis

Customer Experience VIP Guarantee + Complain Handling

Parameters Management

Query & Sharing of Data + All Network Parameter Check + Modification & Management


VIP KPI analysis

Assisted analysis of complaints

Cell performance analysis

Frequency analysis

Coverage analysis

Neighboring cell analysis

Analysis of GSM-UMTS neighboring cellsUMTS

GSM

RF Optimization - Nastar

Note: For information about how to use these three network optimization tools, see their help files which you can obtain after you install the tools.


Analyzing CHRs by Using the Nastar

Using the cell performance analysis function provided by the Nastar,

you can analyze CHRs to quickly locate common problems at the

network level and provide methods for backtracking abnormal

problems.

See the Nastar help.

Start

Create an E2E task for cell performance data analysis

Create a task for importing cell

performance data

Check the completeness of cell performance analysis data

Create a task for cell performance analysis

Check the results of the cell performance analysis

Export the report of the cell performance analysis

End


Display of various charts

The same indicator is displayed in different charts. Different parameters are displayed in different charts in the

same report.

Top N Cell Filtering - PRS

Focus on the key information in the KPI report.

Top N Abnormal counters are highlighted.Chart


ye

Check all parameters on the entire network (Parameter check of the DAMS)

Are the settings of some parameters

inappropriate?

Modify parameters

Problem resolved

Collect parameter check and optimization experience of experts

(Rule development platform)

Twice a week

Parameter adjustment

requirement 1

Parameter adjustment requirement 2

Parameter adjustment requirement n

Entire Network Parameter Check

■ All parameters on the entire network are checked twice a week.

■ If any parameter settings are inappropriate, engineers can modify them directly.

■ Personnel are specially assigned for checking all parameters on the entire network.

Parameter Modification■ Parameter modification involves engineering parameters and configuration parameters. Onsite

engineers modify the engineering parameters and system engineers modify the configuration parameters.■ Configuration parameters are classified into different levels. Low-level configuration parameters can be modified by any engineers and high-level configuration parameters can be modified only by system engineers.

■ Parameter modification must be checked by the DAMS and approved by the personnel specially assigned for checking parameters.■ The DAMS manages the parameter modification

history.

Check configuration or engineering parameters.

(One engineer)

Modify/Check parameters

Deliver modified parameters.

Problem resolved

Top N cell/carrier identification, onsite test, and complaint handling

Query parameter modification history

Parameter management: Check/Export parameters and manage parameter modification history

Core Parameter Check - DAMS

Yes

xx


Introduction to Three Network Optimization Tools

Evaluation of Working Efficiency of the Tools

Used to Take Required Actions for Call Drop Analysis


Appendix – Evaluation of Working Efficiency of the Tools Used to Take Required Actions for Call Drop Analysis

Required Action ToolProcessing Duration Required by Tools

Processing Duration Required by Manual Analysis

Identify call drop causes by analyzing performance dataand CHRs

Traffic statistics: PRS and excel templates CHRs: Nastar and Insightsharp

Traffic statistics: 10 minutes/BSC CHRs: 20~30 minutes/BSC

Traffic statistics: 20~30 minutes/BSC CHRs: 20~30 minutes/BSC


OMStar, MainDivAnalyse, DownlinkAnalyse, and IntferBandAnalyse

5 minutes/BSC 30 minutes/BSC

Check for device faults and alarms OMStar and alarm console 5 minutes/BSC 30~60 minutes/BSC Check all parameters Parameter check tool and OMStar 1~5 minutes/BSC 30~90 minutes/BSC Check for BTS or BSC version differences and parameter differences

Not available Not sure


Not available 10~20 minutes/cell


Nastar 30 minutes 1~3 minutes/cell for identifying missing neighboring cells and top N cells


Not available 60 minutes/BSC


Not available 20 minutes/BSC


Not available 20 minutes


Nastar and MapInfo 60 minutes/BSC 30~60 minutes/BSC


Not availableA long time for obtaining data and 10 minutes for analyzing data


Not availableA long time for obtaining data and 10 minutes for analyzing data


Nastar and Insightsharp 10~30 minutes/BSC Statistical analysis: 30~60 minutes/BSC Single-call CHRs: 3~10 minutes/Call

Thank youwww.huawei.com

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