4 GSM Call Drops (Influence Factors + Troubleshooting Methods and Tools + Deliverables) 20110730(合作方版)

Security Level:

2013/2/13

GSM Call Drop: Influence Factors + Troubleshooting Methods and Tools + Deliverables Prepared by: Wang Zhicheng Approved by: Qi Haofeng www.huawei.com

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.


Huawei Confidential

Change History Date

Version

2010-11-30

Version issued in December 2010

Description 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.

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.

Reviewer

Author

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)

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),

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

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)

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


Huawei Confidential

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 Confidential

Page 4

Call Drop Problem Overview Cause Analysis and Data Processing Actions and Deliverables Required for Troubleshooting Call Drops Call Drop Cases


Huawei Confidential

Page 5

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.

MS

BTS

MSC

BSC

Connection failure Error indication

Clear request Calculate call drop counter



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.


Huawei Confidential

Page 6

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_T RAF_CH _UM_C ALL_DR OPS

CM330: CELL_T RAF_CH _CALL_ DROPS_ IN_STA BLE_ST ATE

CM332:C ELL_TR AF_CH_ CALL_D ROPS_N O_MR

CM333: CELL_T RAF_CH _CALL_ DROPS_ ABIS_L NK_FAI L

CM334: CELL_T RAF_CH _CALL_ DROPS_ EQUIP_ FAIL

CM335: CELL_T RAF_CH _CALL_ DROPS_ FORCE_ HO

CM397: CELL_L OOP_ST ART_FA IL_DRO PS

CM385:C ELL_LO OP_RES TORE_F AIL_DR OPS

CM331: CELL_T RAF_CH _CALL_ DROPS_ HO_FAI L


Huawei Confidential

Page 7

Types of Call Drops Caused by Um Interface Problems in Terms of KPIs CM33C:CELL_TRAF_CH_UM_CALL_DROPS 







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.


CM330:CELL _TRAF_CH_C ALL_DROPS_ IN_STABLE_ STATE

CM3300: CELL_TR AF_CH_S TATIC_S TATE_CA LL_DROP S_ERR_I ND

CM3301 :CELL_ TRAF_C H_STAT IC_STA TE_CAL L_DROP S_CONN _FAIL

CM331:CE LL_TRAF_ CH_CALL_ DROPS_HO _FAIL

CM3302: CELL_TR AF_CH_S TATIC_S TATE_CA LL_DROP S_REL_I ND

Huawei Confidential

H3027Ca: CELL_INT RACELL_H O_FAIL_E XP_TCHF_ TRAF

H3028Ca: CELL_INT RACELL_H O_FAIL_E XP_TCHH_ TRAF

H3127Ca: CELL_INT RABSC_OU TCELL_HO _FAIL_EX P_TCHF_T RAF_NOT_ INCLUDE_ DR

Page 8

H3128Ca: CELL_INT RABSC_OU TCELL_HO _FAIL_EX P_TCHH_T RAF_NOT_ INCLUDE_ DR

H3227Ca: CELL_INT RABSC_IN CELL_HO_ FAIL_EXP _TCHF_TR AF

H3228Ca: CELL_INT RABSC_IN CELL_HO_ FAIL_EXP _TCHH_TR AF

Example: Percentages of Various Call Drops in Xingtai The 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.


Huawei Confidential

Page 9

Call Drop Problem Overview Cause Analysis and Data Processing Actions and Deliverables Required for Troubleshooting Call Drops

Call Drop Cases


Huawei Confidential

Page 10

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.




Huawei Confidential

Page 11

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.

1. Determine the scope of the call drop problem

2. Analyze the call drop causes

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

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

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

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

Yes 4-3. Provide a summary report and cases


Huawei Confidential

Page 12

No

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


Huawei Confidential

Page 13

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.


Huawei Confidential

Page 14

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


Huawei Confidential

Page 15

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.


Huawei Confidential

Page 16

Tools and Methods for Analyzing Traffic Statistics

Call drop rates and percentages of various call drops

Tools: excel template attached and OMStar to be released Method: 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.

Template for analyzing call drop data:


M3030A:Call M3030B:Call M3030C:Call M3030D:Call M3030G:Call M3030H:Call M3030I:Call M3030J:Call M3030K:Call

Huawei Confidential

Drops Drops Drops Drops Drops Drops Drops Drops Drops

on on on on on on on on on

Call Drop(RF Cause) TCH(TA) 0.00% TCH(Uplink Received Level) 81.82% TCH(Downlink Received Level) 0.00% TCH(Uplink and Downlink Received Level) 0.00% TCH(Uplink and Downlink FER) 0.00% TCH(Uplink Quality) 0.00% TCH(Downlink Quality) 9.09% TCH(Uplink and Downlink Quality) 0.00% TCH(Other) 9.09%

Page 17

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 Call Drops on TCH(TA) Call Drops on TCH(Uplink Received Level) Call Drops on TCH(Uplink Interference) Call Drops on TCH(Uplink Received Level Suddenly Decrease) Call Drops on TCH(Uplink Quality) Call Drops on TCH(Downlink Received Level) Call Drops on TCH(Downlink Interference) Call Drops on TCH(Downlink Quality) Call Drops on TCH(Downlink Received Level Suddenly Decrease) Call Drops on TCH(Uplink and Downlink Received Level) Call Drops on TCH(Uplink and Downlink Interference) Call Drops on TCH(Uplink and Downlink Quality)

Huawei Confidential

Page 18

Percentage Times 2.17% 5 41.30% 95 3.04% 7 0.00%

0

39.13% 2.17% 1.30% 10.87%

90 5 3 25

0.00%

0

0.00%

0

0.00% 0.00%

0 0

Tools and Methods for Analyzing CHRs 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.


Huawei Confidential

Page 19

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.


Huawei Confidential

Page 20

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.


Huawei Confidential

Page 21

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. DT call drops

Neighboring cell relationships

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.

Handover parameters

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


Interference problems

Due to cofrequency/adjacent -frequency interference, internetwork interference, or intermodulation interference of equipment, call drops due to bad quality occur.

Huawei Confidential

Cross coverage

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

Page 22

Terminal problems

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.

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.


Huawei Confidential

Page 23

Call Drop Problem Overview Cause Analysis and Data Processing Actions and Deliverables Required for Troubleshooting Call Drops

Call Drop Cases


Huawei Confidential

Page 24

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.

1. Determine the scope of the call drop problem

2. Analyze the call drop causes

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

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

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

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

Yes 4-3. Provide a summary report and cases


Huawei Confidential

Page 25

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.


Huawei Confidential

Page 26

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

Operation

Deliverable

Subsequent Action

Identify call drop causes by analyzing performance data In special scenarios such as network swapping, analyze and CHRs 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

1. Check results.

1. Rectify the RF tunnel faults.

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

1. Check results.

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

1. Check results.

1. Optimize parameter settings.

Check all parameters

2. Solutions and measures for optimizing parameter settings.

2. Provide a summary report and cases.

1. Check results and impacts of the differences.


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.

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.

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


2. Solutions and measures for rectifying the 2. Provide a summary report and RF tunnel faults. cases. 1. Rectify the device faults and clear the alarms.

2. Solutions and measures for rectifying the 2. Provide a summary report and device faults and clearing the alarms. cases.

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


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


2. Solutions and measures for optimizing the parameter settings.

Huawei Confidential

Page 27



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

Check network coverage (power matching and newly deployed sites)

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.

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

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

Subsequent Action

Deliverable

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. 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.

1. Optimize power matching. 2. Optimize RF coverage

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. Analysis results of neighboring relationships, such as missing neighboring cells and redundant neighboring cells. 1. Optimize neighboring relationships. 2. Conclusion in inheriting or adjusting neighboring relationships


3. Solutions for optimizing neighboring relationships.

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

1. Changes in traffic and KPIs and 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.

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. 3. Provide a summary report and cases.


Huawei Confidential

Page 28


Operation

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

Analyze frequencies after network expansion, deployment, or reconstruction

Deliverable

Subsequent Action

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 1. Traffic changes in CS and PS services and how to resolve the problem. the impacts of the changes. 2. Solutions and measures.

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

3. Provide a summary report and cases. 1. Analysis results of the frequencies used on 1. Analyze the frequencies used on the current network the current network, evaluation result of the and evaluate the frequency replanning gain by referring frequency replanning gain, and solutions and to the GSM Frequency Replanning theme and output the measures for replanning frequencies or analysis and evaluation results. 1. Replan or optimize frequencies. optimizing frequencies. 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.

Check for abrupt events such as charging policy Analyze the impacts of abrupt events on call drops and changes, weather output the analysis results. changes, and mass gatherings

2. Eliminate interference. 2. Interference analysis results and measures for eliminating interference. 3. Provide a summary report and cases. 3. Conclusion in inheriting or adjusting frequencies and solutions and measures for optimizing frequencies.

1. Impacts of abrupt events on call drops. 2. Solutions and measures.

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.

3. Provide a summary report and cases. 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 Take required actions according to the top N types of call drops causes, and characteristics of call drop and causes. causes. 2. Subsequent actions to be taken.

Huawei Confidential

Page 29

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

Identify call drop causes by analyzing performance dataand CHRs

Operation

Deliverable

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

1. Top N types of call drops and causes. In special scenarios such as network swapping, analyze 2. Subsequent actions to be taken. CHRs to determine whether calls initiated by certain types of MSs or certain subscribers always drop.


Check the reasonableness and consistency of parameter 1. Check results. settings by referring to the GSM Parameters Check 2. Solutions and measures for optimizing theme and output the check results. parameter settings.


1. Check results and impacts of the Check for BTS or BSC version differences and parameter differences. differences by referring to the GSM Parameters Check 2. Solutions and measures for optimizing theme and output the check results and impacts of the parameter settings and BTS or BSC differences. versions.

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

Subsequent Action


1. Optimize parameter settings. 2. Provide a summary report and cases.

1. Optimize parameter settings. 2. Optimize BTS or BSC versions 3. Provide a summary report and cases.

1. For call drops caused by reasonable changes in traffic and KPIs, provide an analysis report to explain the 1. Changes in traffic and KPIs and impacts 1. Analyze the changes in traffic and KPIs and output the problem objectively to the customer and provide of these changes. analysis results and the impacts of these changes. suggestions on how to resolve the problem. For call drops 2. Changes in traffic and KPIs in special caused by unreasonable changes in traffic and KPIs, 2. In a network supporting GSM900 and DCS1800 and configured with the co-BCCH, check the difference in call networking scenarios such as a dual-band troubleshoot the traffic and KPI problems. network and a network configured with codrops and traffic distribution between GSM900 and 2. Optimize traffic distribution in special scenarios such as DCS1800 and between the overlaid subcell and underlaid BCCH and the impacts of these changes. a dual-band network and a network configured with the subcell. 3. Solutions and measures. co-BCCH. 3. Provide a summary report and cases.

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 1. Traffic changes in CS and PS services the traffic changes and the impacts of the changes, including the changes in the proportions of data and CS and the impacts of the changes. services, change causes, and the correlation between the 2. Solutions and measures. traffic changes in data and CS services and the number of call drops.


Huawei Confidential

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. 3. Provide a summary report and cases.

Page 30

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

Operation

Deliverable

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.

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.

Analyze frequencies after network expansion, 2. Analyze whether there is internal and external deployment, or interference and output the analysis results. reconstruction

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

Analyze the longterm 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.

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.

2. Interference analysis results and measures for eliminating interference.

Subsequent Action

1. Replan or optimize frequencies. 2. Eliminate interference. 3. Provide a summary report and cases.

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

1. Impacts of abrupt events on call drops. 2. Solutions and measures.

1. Correlation between the long-term trends of traffic and KPIs and the trend of the call drop rate. 2. Solutions and measures.

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. 3. Provide a summary report and cases. 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. 3. Provide a summary report and cases.


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.


2. Subsequent actions to be taken.

Huawei Confidential

Page 31

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

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


Huawei Confidential

Page 32

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:


Huawei Confidential

Page 33

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.


Huawei Confidential

Page 34

Templates for Providing Supplementary Information for the Call Drop Analysis – Channel and Frequency Analysis Common 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.


Huawei Confidential

Page 35

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.


Huawei Confidential

Page 36

Templates for Providing Supplementary Information for the Call Drop Analysis – Coverage Analysis Common 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.


Huawei Confidential

Page 37

Templates for Providing Supplementary Information for the Call Drop Analysis – Neighboring Cell Analysis Common 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.


Huawei Confidential

Page 38

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.


Huawei Confidential

Page 39

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.


Huawei Confidential

Page 40

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”.


Huawei Confidential

Page 41

Required Actions – Check RF Tunnels (2) Data and Characteristics 数据源

分析模板及相关特征

Data

Performance Data

DT Data and Signaling

[Data Analysis]

[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 7. Template for ranking cells by Rx Level Difference between Main and Diversity Antenna 8. Template for ranking cells by the mean signal strength difference between the serving cell and the neighboring cell

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.

Analysis templates [Characteristics] and 1. The difference between the receive level of the main and the receive level of characteristi the diversity is great. cs 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.

2. Antenna misconnections between cells: Perform DTs along the direction of the major lobe in the cells under possible problem [Data Analysis] sites to check whether the BCCH of the major lobe in each cell is the same as the Alarm list planned BCCH. [Characteristics] 3. Interference caused by antenna intermodulation: Conduct the start idle The voltage standing timeslot test and stop idle timeslot test on wave radio (VSWR) the LMT during off-peak hours and compare alarm is reported. 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]

[Tools]

PRS, OMStar, and DownlinkAnalyse

DT software and IntferBandAnalyse


Huawei Confidential

Alarm and Log

Page 42

Required Actions – Check for Device faults and Alarms Triggering 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 Characteristics Data

Performance Data

Alarm and Log

[Data Analysis]

Analysis templates and characteristics

1. Template for analyzing device faults 2. Template for listing carriers with device faults 3. Template for identifying carriers without traffic volume or with low traffic volumes 4. Template for identifying carriers not involved in any handovers or with small numbers of handovers 5. 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-ofservice 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.


Huawei Confidential

[Data Analysis] 1. Alarm list 2. 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

Page 43

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.


Huawei Confidential

Page 44

Required Actions – Check All Parameters (2) For details about how to check all parameters, see the “2 GSM Parameters Check: Check Rules+Tools+Cases+Deliverables 20110730.PPT”. Data and Characteristics Data

Performance Data

Parameter s


[Data Analysis]

[Data Analysis]

[Data Analysis]

Perform DTs in the coverage of the following areas to check 2. Template for analyzing the distribution of call whether call drops are caused drop causes 2. Check and optimize parameter by inappropriate parameter relationships. settings: top N cells, boundaries 3. Template for analyzing the correlation of areas served by the devices between the trend of CS or PS service traffic 3. Check whether parameter settings from other vendors, areas and the trend of the call drop rate are consistent and perform other where 2G/3G interoperability is parameter checks. allowed. [Characteristics] 1. Template for analyzing call drop scopes


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


1. Check and optimize parameter settings.

[Tools]

[Tools]

PFMStudio, DAMS, CME, and OMStar

DT software and signaling analysis software

Huawei Confidential

Page 45

Required Actions – Check for Version Differences Triggering conditions: If call drops occur after the BSC, BTS, or MSC is upgraded, check for version differences. Data and Characteristics Data

Performance Data

Parameter

[Data Analysis] 1. Template for analyzing call drop scopes


2. Template for analyzing the distribution of call drop causes

[Data Analysis]

[Characteristics]

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.

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.

[Characteristics] Some version differences affect the call drop rates.

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


Huawei Confidential

Page 46

Required Actions – Analyze Neighboring Relationships (1) Triggering conditions: 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”.


Huawei Confidential

Page 47

Required Actions – Analyze Neighboring Relationships (2) Data and Characteristics Data

Performance Data


Parameter

Other Data

[Data Analysis] [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 Handover 8. 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


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 [Data Analysis] and troubleshoot the cross coverage. Handover parameters: [Characteristics] Check and optimize handover parameters 1. Problems such as missing when neighboring neighboring cells, cross coverage, and relationships are inappropriate parameter settings exist. inappropriate or large 2. After calls drop in a cell, MSs access numbers of handovers or only small numbers the network from other cells because of handovers occur. 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.

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

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]

[Tools]

Nastar and CellOpt


Huawei Confidential

[Data Analysis]

Page 48

Required Actions – Check the Parameters of the Other Vendors’ Devices in the Boundaries of HW and Other Vendors’ Devices Triggering 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 and Characteristics Data


Performance Data

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]

[Data Analysis] [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]

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.


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”. HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Page 49

Required Actions – Check Network Coverage (1) Triggering conditions: 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.


Huawei Confidential

Page 50

Required Actions – Check Network Coverage (2) Data and Characteristics Data

Performance Data


[Data Analysis]

[Data Analysis]

[Data Analysis]

1. Template for analyzing weak coverage

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

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. 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 Analysis templates and characteristics

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

7. Template for ranking cells by Rate of MRs (Excessive Coverage) 8. Template for analyzing the correlation between the trend of CS or PS service traffic and the trend of the call drop rate [Characteristics] 1. A large number of call drops are caused by low levels.

Parameter

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.

[Data Analysis]

[Characteristics]

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

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.

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

2. The call drop rate increases and traffic volume NOTE decreases after network adjustment operations such as It is difficult to identify the coverage shrink caused by power network swapping, network deployment, network matching problems and combiner faults by checking RF expansion, and RF optimization. tunnels. Therefore, you need to focus on power and 3. The proportions of weak coverage or cross coverage combiners if the RF tunnel check does not show any MRs are high for some cells. problems but the coverage shrinks.


Huawei Confidential

Other Data

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.

Page 51

Required Actions – Analyze Changes in Traffic and KPIs in Special Scenarios Triggering conditions: Analyze changes in traffic and KPIs in dual-band networks, enhanced dual-band networks, and concentric networks. Data and Characteristics Data

Performance Data [Data Analysis] 1. Template for comparing call drop trends between the two bands in a dual-band network or an enhanced dualband 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.


Huawei Confidential

Page 52

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 and Characteristics Data

Performance Data [Data Analysis]


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


Huawei Confidential

Page 53

Required Actions – Analyze Frequencies (1) Triggering conditions: 

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.


Huawei Confidential

Page 54

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 Characteristics Data

Performance Data

Other Data

[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) Analysis templates 6. Template for ranking cells by Uplink Interference and characteristics [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.

[Data Analysis] Analyze MRs and output the interference matrix. [Characteristics] There are a lot of intra-frequency and interfrequency neighboring cells generating great interference signals. [Tools] CellOpt

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.


Huawei Confidential

Page 55

Required Actions – Check for Abrupt Events Triggering 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 Characteristics Data

Performance Data [Data Analysis] 1. Template for analyzing the correlation between the trend of CS or PS service traffic and the trend of the call drop rate


[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.


Huawei Confidential

Page 56

Required Actions – Analyze the Long-Term Traffic or KPI Trends Triggering 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 and Characteristics

Data

Performance Data [Data Analysis]


1. Template for analyzing the correlation between the trend of CS or PS service traffic and the trend of the call drop rate [Characteristics] The call drop rate increases slowly with seasonal changes in traffic and increase in the subscriber number.


Huawei Confidential

Page 57

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 and Characteristics Data

Other Data [Data Analysis]


Obtain the following information by analyzing CHRs: 1. Detailed cause values of call drops 2. Top N cells with high call drop rates 3. Top N subscribers with high call drop rates 4. CHRs of VIP subscribers 5. CHRs of subscribers who complain about call drops


Huawei Confidential

Page 58

Required Actions The attached excel provides the triggering conditions, templates, data, and characteristics related to the required actions.


Huawei Confidential

Page 59

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.


Huawei Confidential

Alarm ID 1000 11270 11278 11280 20081 20082 2204 4414 3606

Page 60

Alarm Name LAPD_OML Fault Alarm Transmission LAPD Link Interrupt Alarm E1/T1 Local Alarm E1/T1 Remote Alarm Loss of E1/T1 Signals Alarm(LOS) Loss of E1/T1 Frames Alarm(LOF) TRX Commnunication Alarm TRX VSWR Alarm DRU Hardware Alarm

Identifying and Troubleshooting Call Drops Due to Other Causes Call drops due to other causes

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 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 related alarms. • problems, Call drops and due clearing 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 randomization 2. Enable Flex Tsc in limited areas 3. Enable encryption 4. Adjust ARFCNs


Huawei Confidential

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

Page 61

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. 


Huawei Confidential

Page 62

Call Drop Problem Overview Cause Analysis and Data Processing

Actions and Deliverables Required for Troubleshooting Call Drops Call Drop Cases


Huawei Confidential

Page 63

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

 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 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.


Huawei Confidential

Page 64

Case 1 – Impact of Parameter Settings of Other Vendors' Equipment on Call Drops Step 3: Take required actions. Required Action

Data Analysis Result


The call drop problem occurs in few cells.


The call drop problem occurs in few cells.


Acceptable


N/A

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

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.

Conclusion

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.

Analyze neighboring relationships (for newly deployed sites and areas where Huawei devices are Acceptable interconnected to devices from other vendors) Check network coverage (power matching and newly deployed sites)

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

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

N/A

Check CS and PS services (their proportions and changes)

This required action is not taken.

Analyze frequencies after network expansion, deployment, or reconstruction


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


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


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



Huawei Confidential

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

Page 65

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

Rectify the device faults.

The call drop rate decreases.

Check for device faults and alarms Some cells report device fault alarms. Check the parameters of the devices from other vendors in the boundaries of the areas served by the devices from other vendors

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.

The call drop rate in the top N cells in Adjust the handover parameter the boundaries of the areas served by settings of the devices from other the devices from other vendors 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.

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.


Huawei Confidential

Page 66

Case 2 – Impact of Traffic Sharing on a Dual-Band Network on Call Drops  Overview After 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.


Huawei Confidential

Page 67

Case 2 – Impact of Traffic Sharing on a Dual-Band Network on Call Drops Step 3: Take required actions. Required Action



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


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.


Conclusion

Huawei Confidential

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.

Page 68

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

Conclusion

Solution

Effect Evaluation

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 Interlayer HO Hysteresis.

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

Check all parameters Check network coverage (power matching and newly deployed sites) Analyze changes in traffic and KPIs in special scenarios (networks supporting GSM900 and DCS1800 and configured with co-BCCH)


Huawei Confidential

Page 69

Case 3 – Impact of Co-BCCH Traffic Sharing on Call Drops  Overview After 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 Step 1: Determine the scope of the call drop problem. According to the analysis of traffic statistics, the call drop problem occurs in top N cells and most top N cells are the overlaid subcells. 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.


Huawei Confidential

Page 70

Case 3 – Impact of Co-BCCH Traffic Sharing on Call Drops Step 3: Take required actions.

Step 4: Troubleshoot call drops and evaluate the result.

Required Action


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.


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.


Huawei Confidential

Page 71

Case 4 – Impact of Seasonal Changes on Call Drops  Overview After 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 Step 1: Determine the scope of the call drop problem. According to the analysis of traffic statistics, the call drop problem occurs in top N cells and on 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.


Huawei Confidential

Page 72

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. NOTE The MPD performance deterioration at the Telenor site in country N is caused by multiple causes and the season factor is only one of them. HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Page 73

Case 5 – Call Drop Troubleshooting in a Typical Area  Overview At 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. 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.


Huawei Confidential

Page 74

Case 5 – Call Drop Troubleshooting in a Typical Area Step 4: Troubleshoot call drops Step 3: Take required actions.

Required Action



Acceptable


Acceptable

and evaluate the result. Conclusion

Traffic statistics: Most call drops The Longfeng expressway bridge runs are caused low levels over the Um through a wetland preservation area, where interface. no primary network coverage is available Check all parameters and therefore the network coverage is DT data: No primary network Analyze neighboring relationships (for newly chaotic. As a result, calls are handed over coverage is available and deployed sites and areas where Huawei randomly between cells, interference is therefore the network coverage is devices are interconnected to devices from strong, and the network quality is poor. The chaotic. As a result, calls are other vendors) DT before optimization operations shows handed over randomly between that the network quality is poor and Analyze frequencies after network cells, interference is strong, and handovers are performed frequently. expansion, deployment, or reconstruction the network quality is poor.

Solution

Effect Evaluation

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.



Huawei Confidential

Page 75

Case 6 – Call Drops Due to Inappropriate Parameter Settings  Overview The 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 Step 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 low levels over the Um interface.


Huawei Confidential

Page 76

Case 6 – Call Drops Due to Inappropriate Parameter Settings Step 3: Take required actions.


Required Action



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

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


Conclusion

On the current network, if the level of a neighboring DT data: A call initiated in cell A is handed over to cell B where the level is low. As a result, cell under another BSC is the call drops after the handover. According to the moving direction of the DT car, the call greater than –82 dBm, this should be handed over to cell C where the level is higher than that in cell B. neighboring cell has a Parameters: Cell A and cell C are served by the same BSC and cell B is served by another higher priority than the BSC. For cells served by the same BSC, Inter-layer HO Threshold is set to 63 and bit 14 neighboring cells served by the same BSC as the of the 16-bit priority is set to 1. For the neighboring cells served by another BSC, Interlayer HO Threshold is set to 25. In this case, if the level is greater than the sum of Inter- serving cell. As a result, calls in the serving cell are layer HO Threshold and HO Hysteresis, bit 14 of the 16-bit priority is set to 0. On the first handed over to 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 neighboring cell served by same BSC as the serving cell. As a result, calls in the serving cell are first handed over to another BSC. This handover mechanism is inappropriate. the neighboring cell served by another BSC.


Huawei Confidential

Page 77

Solution

Effect Evaluation

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  Overview The 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 Step 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 low levels over the Um interface.


Huawei Confidential

Page 78

Case 7 – Call Drops Due to Cross Coverage Step 3: Take required actions.


Required Action



Acceptable


Acceptable


Acceptable

Analyze neighboring relationships (for newly Traffic statistics: Most call drops are caused low deployed sites and areas where Huawei devices are levels over the Um interface. interconnected to devices from other vendors) DT data: A call in cell A is not handed over to cell B when the MS is moving to a street corner. After Check network coverage (power matching and the MS passes through the street corner, the call newly deployed sites) drops because the level decreases and the network quality becomes poor.


Huawei Confidential

Conclusion

Solution

Effect Evaluation

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.


Page 79

Case 8 – Call Drops Due to Missing Neighboring Cells  Overview The 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. 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.


Huawei Confidential

Page 80

Case 8 – Call Drops Due to Missing Neighboring Cells Step 3: Take required actions. Required Action



Acceptable


Acceptable


Acceptable


Analyze neighboring relationships (for newly Traffic statistics: Most call drops are caused low levels over the Um deployed sites and areas where Huawei interface. devices are interconnected to devices from DT data: After the test MS in cell A passes through the corner of the other vendors) 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 Check network coverage (power matching as a neighboring cell of cell A and therefore drops. After the call drops, and newly deployed sites) the test MS initiates another call and accesses cell B.


Huawei Confidential

Conclusion

Solution

Effect Evaluation

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.


Page 81

See the following figure.

Case 9 – Call Drops Due to Interference  Overview The 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 Analysis Step 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. HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Page 82

Case 10 – High Call Drop Rate Due to BTS Upgrade  Overview After 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 Analysis Step 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/s BTS3012 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.


Huawei Confidential

Page 83

Case 11 – Call Drops Due to Coverage Changes Caused by Addition of Combiners  Overview After 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 Step 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 low levels over the Um interface.


Huawei Confidential

Page 84

Case 11 – Call Drops Due to Coverage Changes Caused by Addition of Combiners Step 4: Troubleshoot call drops and evaluate the result.

Step 3: Take required actions.

Required Action



Acceptable


Acceptable

Conclusion

Solution

Effect Evaluation

Analyze neighboring relationships (for newly deployed sites and areas where Acceptable Huawei devices are interconnected to devices from other vendors) Check RF tunnels for main and diversity faults, cross connections, and interference Check network coverage (power matching and newly deployed sites)

Some combiners are added to BTSs, but the power of the BTSs is not increased. Traffic statistics: Most call drops are caused low levels over the Um interface. DT data: The network coverage becomes weak after the network swapping.


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

Huawei Confidential

Page 85

The network coverage and call drop rates become normal.

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

272

Meaning of the Cause Value

Telephone Number of the Calling/Called Party

Access Time (Precise to Second)

Access Time (Precise to Millisecond)

Call Duration

MSC_REL_NORMAL _CLR (The MSC releases a call normally.)

1528101****

2010-11-12 10:38

960

163770

 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.


Huawei Confidential

Page 86

Call Flag

0

Introduction to Three Network Optimization Tools Evaluation of Working Efficiency of the Tools Used to Take Required Actions for Call Drop Analysis


Huawei Confidential

Page 87

Three Network Optimization Tools Network Optimization

 Network optimization: Network optimization involves a lot of manual

 A lot of persons, equipment, and time are required for DTs.

analysis. This consumes not only labors

 A lot of work is involved to replan the frequencies of the entire network.

and time, but also introduces risks.

 KPIs and subscriber experience cannot be closely integrated.

 Tool application: Currently, three network optimization tools can be used in basic network optimization analysis, including

 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.

TOP cell filtering, neighboring cell

 A lot of persons are involved and it is difficult to manage

optimization, and frequency optimization.

parameters.

 Tool deployment: You need to purchase a server. Ensure that the data to be analyzed by the tools are MRs and CHRs.

Nastar

PRS

DAMS

In addition, you need to add SAUs for the

BSC because a lot of data is involved. Three Network Optimization Tools


Huawei Confidential

Page 88

Support Capability of Three Network Optimization Tools Tool

Main Feature

V9R8C12SP21 V9R8C12SP23

V9R11C00

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

Nastar

Network Monitoring

Four Main Functions

RF Optimization

Network KPIs + Top N Cells + Top N TRXs

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


Huawei Confidential

Page 89

RF Optimization - Nastar Analysis of GSM-UMTS neighboring cells

UMTS

Neighboring cell analysis

Coverage analysis

GSM Frequency analysis Cell performance analysis

Assisted analysis of complaints

VIP KPI analysis 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. HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Page 90

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.

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

See the Nastar help.


Huawei Confidential

Page 91

Top N Cell Filtering - PRS

Chart

Display of various charts

Top N

Abnormal counters are highlighted.

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

same report.

Focus on the key information in the KPI report. HUAWEI TECHNOLOGIES CO., LTD.

Huawei Confidential

Page 92

Core Parameter Check - DAMS 

ye

Collect parameter check and optimization experience of experts (Rule development platform)

Entire Network Parameter Check ■ All

parameters on the entire network are checked twice a week.

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

Are the settings of some parameters inappropriate?

■

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

■

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

Twice a week

Yes

Modify parameters Parameter Modification

Parameter adjustment Parameter Parameter adjustment requirement n adjustment requirement 2 requirement 1 Top N cell/carrier identification, onsite test, and complaint handling

Check configuration or engineering parameters. (One engineer) Modify/Check parameters

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. ■

Problem resolved

Query parameter modification history

Deliver modified parameters.

Problem resolved

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


Huawei Confidential

Introduction to Three Network Optimization Tools Evaluation of Working Efficiency of the Tools Used to Take Required Actions for Call Drop Analysis


Huawei Confidential

Page 94

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

Tool

Processing Duration Required by Tools Traffic statistics: 10 minutes/BSC CHRs: 20~30 minutes/BSC

Traffic statistics: PRS and excel templates CHRs: Nastar and Insightsharp OMStar, MainDivAnalyse, Check RF tunnels for main and diversity faults, cross DownlinkAnalyse, and 5 minutes/BSC connections, and interference IntferBandAnalyse Check for device faults and alarms OMStar and alarm console 5 minutes/BSC Check all parameters Parameter check tool and OMStar 1~5 minutes/BSC Check for BTS or BSC version differences and Not available parameter differences Check the parameters of the devices from other vendors in the boundaries of the areas served by the Not available devices from other vendors Analyze neighboring relationships (for newly deployed sites and areas where Huawei devices are Nastar 30 minutes interconnected to devices from other vendors) Check network coverage (power matching and newly Not available deployed sites) Analyze changes in traffic and KPIs in special scenarios (networks supporting GSM900 and Not available DCS1800 and configured with co-BCCH) Check CS and PS services (their proportions and Not available changes) Analyze frequencies after network expansion, Nastar and MapInfo 60 minutes/BSC deployment, or reconstruction Check for abrupt events such as charging policy Not available changes, weather changes, and mass gatherings Analyze the long-term traffic trends due to seasonal Not available changes and subscriber number increase Check for complaints and call drops due to other Nastar and Insightsharp 10~30 minutes/BSC causes by analyzing CHRs Identify call drop causes by analyzing performance dataand CHRs


Huawei Confidential

Processing Duration Required by Manual Analysis Traffic statistics: 20~30 minutes/BSC CHRs: 20~30 minutes/BSC 30 minutes/BSC

30~60 minutes/BSC 30~90 minutes/BSC Not sure 10~20 minutes/cell 1~3 minutes/cell for identifying missing neighboring cells and top N cells 60 minutes/BSC 20 minutes/BSC 20 minutes

30~60 minutes/BSC A long time for obtaining data and 10 minutes for analyzing data A long time for obtaining data and 10 minutes for analyzing data Statistical analysis: 30~60 minutes/BSC Single-call CHRs: 3~10 minutes/Call

Page 95

Thank you www.huawei.com

4 GSM Call Drops (Influence Factors + Troubleshooting Methods and Tools + Deliverables) 20110730(合作方版)

Recommend Documents