wcdma network performance analysis guide
TRANSCRIPT
Guide to Analysis of WCDMA Network Performance For Internal Use Only
2008-11-29 All Rights Reserved Page 1 of 80
Product Name Confidentiality Level
WCDMA RNP For Internal Use Only
Product Version
1.0 Total 80 Pages
Guide to Analysis of WCDMA Network
Performance (For Internal Use only)
Prepared by:
Brainstorming and Case
Group Date: August 28, 2006
Reviewed by: Date:
Reviewed by: Date:
Approved by: Date:
Huawei Technologies Co., Ltd
All Rights Reserved
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2008-11-29 All Rights Reserved Page 2 of 80
Revision History
Date Revision
Version Description Author
August 28,
2006 1.00 First draft is finished. Zuo Yanzhong
September
24, 2006 1.1
Some errors are revised and subsequent
optimization parts are simplified according to review
comments. The emphasis is to find problems.
Analysis based on observation points and
subsequent analysis data requirements are added.
He Fengming
October 20,
2006 1.2
The document is revised according to the review
comments of the CCB. He Fengming
October 28,
2006 1.3 Alarm analysis is added. He Fengming
2008-11-29 1.31 Review yearly Xiao Zhao
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Contents
1 Overview..........................................................................................................................................8
1.1 Purpose of the Document ......................................................................................................8
1.2 Users of the Document ..........................................................................................................9
2 Necessary Conditions of Performance Analysis and Quality Early Warning ........................10
2.1 Creating Network Planning and Network Optimization Parameter Archives.......................10
2.2 Signaling Flows of UTRAN and Basic Principles of WCDMA .............................................11
2.2.1 Mastery of Signaling Flows and Basic Principles......................................................11
2.2.2 Fast Makeup of Knowledge Points ...........................................................................12
2.3 Familiarization of UTRAN PIs ..............................................................................................12
2.4 Use of the Nastar Tool .........................................................................................................13
2.4.1 Relations between Traffic Statistics PIs and Network Problems...............................14
2.4.2 Mastery of Advanced Functions of the Nastar Tool...................................................15
2.5 Summary..............................................................................................................................16
3 Three Steps of Performance Analysis and Quality Early Warning..........................................17
3.1 Step 1: Knowledge of Network Conditions ..........................................................................17
3.1.1 Historic Performance Index of Network ....................................................................18
3.1.2 Parameter Revision History ......................................................................................21
3.1.3 Network Operation History ........................................................................................24
3.2 Step 2: Preparations for Performance Analysis ...................................................................24
3.2.1 Starting Time of Performance Analysis and Quality Early Warning ..........................24
3.2.2 Preparation of Master Data .......................................................................................25
3.3 Step 3: Ideas and Methods of Performance Analysis and Quality Early Warning...............27
3.3.1 Conventional Methods of Performance Analysis ......................................................27
3.3.2 Analysis Method of Alarm Data .................................................................................28
3.3.3 Quick Analysis of Some PIs ......................................................................................34
3.3.4 Commonly Seen PIs and Corresponding Analysis Idea ...........................................34
3.3.5 General Idea of Performance Analysis and Quality Early Warning ..........................35
3.3.6 Procedures and Methods of Performance Analysis and Quality Early Warning .......36
4 Observation Point and Analysis Examples of Typical Problems ............................................50
4.1 Observation Points of Typical Problems ..............................................................................51
4.1.1 RRC Establishment Analysis Observation Point.......................................................51
4.1.2 RAB Establishment Analysis Observation Point .......................................................54
4.1.3 Call Drop Analysis Observation Point .......................................................................57
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4.1.4 Soft Handover Analysis Observation Point ...............................................................60
4.1.5 CS/PS Intersystem Handover Analysis Observation Point .......................................61
4.1.6 Traffic Analysis Observation Point.............................................................................66
4.1.7 Key Interface Flow Analysis Observation Point ........................................................68
4.1.8 HSDPA Analysis Observation Point ..........................................................................72
4.2 Example of Analysis Based on Observation Point...............................................................72
4.3 Summary..............................................................................................................................77
5 Closing of Performance Analysis and Quality Early Warning .................................................78
5.1 Basic Requirements for Analysis Conclusion ......................................................................78
5.2 Output Analysis Report ........................................................................................................79
5.3 Summary..............................................................................................................................79
6 References ....................................................................................................................................80
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Figures
Figure 1 Measurement of performance index......................................................................... 13
Figure 2 Trend figure of call drop rate..................................................................................... 20
Figure 3 Revision history of baseline parameters................................................................... 23
Figure 4 History of network operations ................................................................................... 24
Figure 5 Alarm analysis processing flow................................................................................. 29
Figure 6 Performance analysis flow........................................................................................ 37
Figure 7 Performance analysis flow (Continued).................................................................... 38
Figure 8 Performance analysis of RRC establishment success rate...................................... 45
Figure 9 Performance analysis of RAB establishment success ............................................. 47
Figure 10 Special topic analysis.............................................................................................. 51
Figure 11 General information about RRC setup.................................................................... 73
Figure 12 Distribution of RRC setup scenario ........................................................................ 74
Figure 13 Comparison of RRC setup scenario success rate.................................................. 74
Figure 14 Analyzing the cause of RRC rejection .................................................................... 75
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Guide to Analysis of WCDMA Network Performance
Keywords
Performance analysis, quality early warning, KPI, Nastar tool
Abstract
Network performance analysis and quality early warning aim to accurately and
effectively find network performance and quality problems and give early warnings.
This document describes the general ideas, methods and procedures of UMTS
network performance analysis and quality early warning. It is intended to provide
reference for analysis operations and early warning actions of various regional
divisions and representative offices and to improve the efficiency of UMTS network
performance analysis and quality early warning.
Acronyms and Abbreviations
Abbreviation Full Spelling
ALCAP Access Link Control Application Part
APS ATM Protection Switching
CCP Communication Control Port
CDL Call Detail Log
CDR Call Drop Rate
CE Channel Element
CHR Call History Record
CHR Calling History Record
CN Core Network
GPS Global Positioning System
IOS Intelligent Optimization System
KPI Key Performance Index
MSP Multiplex Section Protection
MTP3B Message Transfer Part
NCP NodeB Control Port
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Abbreviation Full Spelling
NEMU NodeB Environment Monitor Unit
NMON NodeB Monitor Unit
NodeB NodeB
PI Performance Index
RAB Radio Access Bearer
RF Radio Frequency
RNC Radio Network Controller
RRC Radio Resource Control
RRU Radio Remote Unit
SAAL Signaling ATM Adaptation Layer
SCCP Signaling Connection Control Part
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1 Overview A commercial network requires regular performance analysis and observation of QoS
and running status, together with a timely early warning of abnormal or potential risks.
Network performance analysis and quality early warning offer direct guidance to
network optimization and expansion.
Performance analysis and quality early warning aim to accurately and effectively find
network performance and quality problems and give early warnings. What skills must
network optimization engineers and network maintenance engineers master to
monitor a network effectively? What principles, flows and procedures must be followed
in performance analysis and quality early warning to ensure the accuracy and
timeliness of analysis results? Based on Huawei's performance analysis practice in
multiple commercial UMTS networks and the analysis experiences of the Performance
Dept. and the Tool Dept., this document expounds the flows and procedures of
performance analysis and quality early warning, together with other related
precautions.
In this document:
� Version of the performance analysis tool: NastarV400R001C03B020
� RNC version: BSC6800V100R006C01B071
� NodeB version: BTS3812EV100R006C02B040
1.1 Purpose of the Document
In network performance analysis, engineers often encounter the following problems:
1) How to start network performance analysis? What skills are prerequisite to
effective network monitoring?
2) How to make performance analysis? How to make a fast, effective analysis by
using so many performance indexes (PIs) provided by traffic statistics tools? Is
there any reasonable flow?
3) “I do not know much about internal implementation of product modules, nor can I
understand many CHRs. Can I make performance analysis? ”To what extent
does performance analysis depend on a mastery of CHR?
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4) For multiple abnormal KPIs, the Nastar tool offers the causes such as RF.RLCRst,
RF.ULSync and UuNoReply. How to make further analysis?
5) If the call drop rate of a network PS is 5%, is any early warning needed? What are
the early warning principles?
Some other questions are not listed here.
In the first performance analysis, engineers tend to make a mistake: They expect to
find the one-to-one correspondence between traffic statistics PIs and causes of
problems. They first export a large quantity of traffic statistics indexes in analysis. For
example, they export WCDMA Performance Monitoring Report from the Nastar tool
once every week and pick out abnormal PIs. Then, they expect to find out the causes
of those abnormal PIs from an encyclopedia.
The causes of some problems, such as cell power resource congestion (Power.Cong)
and IUB bandwidth restricted (IUB.Band), can be directly found from the PIs of the
Nastar tool. But it is very hard to find out the causes of many network problems simply
by querying PIs. The complexity of a UMTS network determines that performance
analysis and quality early warning are comprehensive and systematic. These jobs
require that analysts should master necessary skills and use normalized methods to
analyze network performance while getting familiar with current network conditions.
This document does not aim to provide a valuable book, through which performance
analysts can easily analyze the running quality and performance of a network simply
by querying traffic statistics KPIs. Instead, by expounding the general ideas and
necessary procedures of performance analysis, the document normalizes network
analysis and early warning actions and corrects network monitoring mistakes, to
improve the efficiency of performance analysis and quality early warning.
1.2 Users of the Document
This document is directly intended for the network optimization engineers and network
maintenance engineers of regional divisions and representative offices. Performance
analysis and quality early warning require a good knowledge of on-site network
conditions and network operations, and fast analysis and location of changes in
performance indexes.
This document can also be used for reference by other network monitoring engineers.
In remote network performance analysis, the engineers in the Headquarters or other
engineers need to get the latest traffic statistics data and know about the recent
network operations. “To gain a decisive victory a thousand miles away”, the first and
foremost prerequisite is to acquire a good knowledge of the “war situation” a thousand
miles away.
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2 Necessary Conditions of Performance Analysis and Quality Early
Warning
The necessary skills of performance analysis and quality early warning include being
familiar with signaling flow and basic principles, knowing about traffic statistics PIs of
product implementation, and mastering each function of the Nastar tool. The following
expounds these skills one by one, but the emphasis is laid on the extent of mastery
and the methods of a quick mastery.
2.1 Creating Network Planning and Network Optimization Parameter Archives
Parameter monitoring is an important task of network monitoring as well as an
important means of knowing about network performance transition. For every
monitored network, we should first create initial network planning and network
optimization parameter archives. Then, we should make timely maintenance to keep
them consistent with actual system configuration. For a network managed by Huawei,
we may set up a flow or a mechanism to notify customers before changing any
parameter to synchronously update both parties’ parameters. Practice proves that this
may greatly reduce performance hazards caused by human factors. For other
networks, customers may maintain networks themselves by updating regularly, or
updating parameter archives in case of any big change in networks, such as upgrade
and problem optimization. For specific templates and parameter values, see Guide to
WCDMA Parameter Setting of the corresponding on-site RNC version. In actual
operations, we should keep complete operation records. For details, see 3.1.2
“Parameter Revision History”.
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2.2 Signaling Flows of UTRAN and Basic Principles of WCDMA
2.2.1 Mastery of Signaling Flows and Basic Principles
Case: In several cells of a site, traffic statistics analysis shows that the success rate of
RRC connection establishment decreases and that the cause of RRC connection
failure is mainly RRC.Fail.ConnEstab.NoReply. In the performance analysis of this
problem, engineers wonder whether too small CCP bandwidth configuration of this site
makes RNC unable to receive any Complete response from UE. May I ask whether
the Complete message is related to restricted CCP bandwidth? How is an RRC
connection established based on the protocol stack of the Uu interface and the Iub
interface? When RRC is set up on dedicated channels and common channels
respectively, what are the differences in the signaling flow and protocol stack
implementation?
The Nastar tool provides the query of numerous indexes oriented to service process,
algorithm process and resource use. The counter implementation of these indexes in
a product is based on the following:
1) Signaling flows of the UTRAN, such as RRC connection establishment flow, RAB
establishment flow, and soft handover flow.
2) Specific statistics in protocol modules, such as counter statistics in
RLC/MAC/PDCP protocol modules and link measurement counter statistics in
SAAL/MTP3-B modules. We can achieve an accurate understanding of these
statistical points only if we have mastered the basic principles of WCDMA network
planning and got familiar with protocol stacks of standard interfaces.
A good knowledge of the protocol stacks and service flows of WCDMA enables
performance analysis to have a definite object in view. The Nastar template provides
the query functions oriented to basic PIs, but an analysis of these PIs alone cannot
easily help find network problems. If you are familiar enough with signaling flows and
basic principles, you can skillfully pick out other PIs from traffic statistics indexes and
make an auxiliary analysis. You can better understand the internal relations between
abnormal KPIs and coverage, uplink interference, load or transmission. This makes
your analysis go in a right direction.
Some engineers who have just come into contact with performance analysis say that
when they see some abnormal indexes from the daily report of the Nastar tool, they do
not know how to make an in-depth analysis. In this case, first ask yourself whether you
are familiar enough with basic signaling flows of the UTRAN and protocol stacks of
WCDMA. If no, you cannot but be at a loss and need to take this lesson as soon as
possible. If you have mastered related knowledge points, you may participate in the
discussion of performance analysis methodology. The prerequisite to Chapter 3 of this
document is engineers’ mastery of basic flows and principles.
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To sum up, the mastery of signaling flows and basic principles is necessitated by the
following:
1) Abnormality location and analysis can have a definite object in view. We can
quickly search for other related indexes based on flows and basic principles and
make an auxiliary analysis.
2) Getting familiar with flows and principles helps associate abnormal PIs with
network problems (such as coverage and interference) and roughly determine the
nature of problems according to abnormal PIs, to select corresponding special
topic functions (coverage and interference) of the Nastar tool for an in-depth
analysis.
3) The mastery of signaling flows and basic principles helps analyze CHR. Although
CHR is the implementation of product internal modules, a good knowledge of
signaling and basic principles helps quickly get involved in CHR analysis.
2.2.2 Fast Makeup of Knowledge Points
Performance analysis requires that engineers should master basic signaling flows, get
familiar with protocol stacks of standard interfaces and know about related algorithms
for product implementation. For numerous RRM algorithms, engineers need to know
about their concepts even if they cannot acquire a good knowledge of them. If the
analyzed commercial networks contain some algorithms, engineers need to learn
them well.
Those engineers unfamiliar enough with flows and principles are suggested to learn
the following slides to acquire a quick knowledge of signaling flows of basic services
get familiar with protocol stacks of various WCDMA standard interfaces and know
about basic functions of various protocol modules.
1) Advanced Training for W Network Planning----Signaling Flow.ppt
2) Advanced Training for W Network Planning ----WCDMA Handover Principles.ppt
If a network to be analyzed involves DCCC, HSDPA or CMB, you need to obtain
related information to form a basic concept of these algorithms or services before
making any performance analysis.
2.3 Familiarization of UTRAN PIs
After you have mastered basic signaling flows, you need to know about the statistics of
the performance indexes of the current product. Performance analysis is directly
based on these PIs provided by the product. For example, the product version
RNCV100R006B071 does not make statistics of the causes of RB configuration and
RB reconfiguration failure of CMB service. Therefore, we cannot make an in-depth
analysis of the cause of RB failure during CMB performance analysis.
In performance analysis, engineers need to keep querying Performance Index
Reference Help and HUAWEI RAN KPI for Performance Management of a
corresponding version. We must be familiar with common performance indexes and
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measurement points. Only in this way can the second query of traffic statistics or
auxiliary query of PIs have a definite object. At present, the common analysis indexes
include “RNC integrated performance measurement” and “cell measurement” shown
in the following figure. Performance analysis engineers first need to get familiar with
the PIs of both. They also need to know as much about other PIs as possible to
broaden the vision of performance analysis.
Figure 1 Measurement of performance index
2.4 Use of the Nastar Tool
The most essential functions of the Nastar tool are performance query and
performance report. Both of the functions do not need separate training. After the
Nastar tool is installed, nearly everyone can use them. Performance analysts’ tool
skills should not always remain at the use of both the functions because that is far
from enough.
Performance analysts’ mastery of the Nastar tool includes the following three levels:
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1) Provide performance analysis results at the level of traffic statistics PIs. Make a
special topic analysis of each service flow based on the familiarization of
signaling flows and the UTRAN KPI, and find out abnormal observation points in
a network. Some abnormal observation points correspond to problem causes
such as Power.Cong while most cannot such as RLCRst, ULSync, UuNoReply,
and so on. Analysis examples are shown in 4.2 “Example of Analysis Based on
Observation Point”.
2) Analyze the relations between traffic statistics PIs and network problems. Define
the nature of such problems.
3) Analyze real network problems by combining the advanced functions of the
Nastar.
2.4.1 Relationship Between Traffic Statistics PIs and Network Problems
Through observation point analysis, we have been able to make a preliminary analysis
of network performance. According to observation point indexes such as power
resource congestion, restricted transmission resource, and insufficient code resource,
we can give a simple quality early warning. But there are still many other performance
problems from which we cannot conclude directly.
For example, call drop analysis shows that many causes of call drop are RLCRst,
ULSync, and UUNoReply. How can we make an in-depth analysis? As shown in the
following table, the learning of signaling flows and basic principles, and topical
analysis practice may help summarize and analyze possible causes of abnormal PIs.
Table 1 Relationship between traffic statistics PIs and causes of call drop
Actual Cause of
Call Drop
Traffic
Statistics PIs for Call Drop
RF Cause
Uplink Interference
Overload
Flow
Transmission
Abnormal
Equipment
Abnormal Mobile
Phone
OM Operation
VS.RAB.RelReqCS.OM √
VS.RAB.RelReqCS.RABPreempt √
VS.RAB.Loss.CS.RF.RLCRst √ √ √
VS.RAB.Loss.CS.RF.ULSync √ √ √
VS.RAB.Loss.CS.RF.DLSync √ √
VS.RAB.Loss.CS.RF.UuNoReply √ √ √ √ √ √
VS.RAB.Loss.CS.Aal2Loss √
VS.Call.Drop.CS.Other √ √ √
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Other special topics, such as RRC access, soft handover, and CS foreign handover,
can also be summarized and analyzed similarly. Performance analysis itself is a
process of continuous experience summarization. We can directly find out the causes
of some PIs, but we can only define the scope of problems for some others and
determine the idea of subsequent analysis according to the scope. If you are not so
skilled in summarizing the relationship between traffic statistics PIs and network
problems, you may make a classified analysis as described in the above table. When
experience is accumulated to some extent, you can “govern by doing nothing that
goes against nature”. That is, upon seeing any abnormal PI, you can naturally
determine the scope of the problem, have a clear idea of next step and judge what
advanced function of the Nastar tool should be selected for an in-depth analysis (The
next section describes the advanced functions of the Nastar).
2.4.2 Mastery of Advanced Functions of the Nastar Tool
Problems: What functions does the Nastar for WCDMA tool have? Can you really
skillfully use the Nastar tool? Consultation to many performance analysis engineers
shows that not many of them can skillfully use each function of this tool. Many people
use the Nastar tool only for simple query of traffic statistics indexes and fast output of
reports.
The Nastar for WCDMA tool integrates years of Huawei’s experiences in network
optimization of WCDMA. It uses the method of data analysis and data mining by
discarding the dross and selecting the essential and eliminating the false and retaining
the true. Fast and effectively, it analyzes network performance and locates network
fault. The Nastar tool is the crystallization of the wisdom of the R&D, Performance
Dept., Maintenance Dept. and Network Planning and Optimization Dept. of Huawei.
Powerful enough, this tool is not used only for fast output of reports and customized
query of traffic statistics indexes. Performance analysts must master each function of
the Nastar tool.
In an in-depth analysis of network performance, we need to use various functions of
the Nastar tool flexibly. To sum up, performance analysis is how to determine the
scope of problems from the whole to the part, how to define the nature of problems
from traffic statistics PIs and how to properly select related functions of the Nastar for
an in-depth analysis. Chapter 3 describes how to determine the scope and nature of
problems, but a skillful use of various functions of this tool is the basis for performance
analysis.
In an in-depth performance analysis, the following functions of the Nastar tool need to
be used:
1) Customization and second query of PI
2) Optimization solution to Intra-frequency adjacent cell
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3) Pilot pollution solution. In pilot pollution analysis, no IOS data needs to be
imported, but CHR, PERF/engineering parameters and configuration files should
be imported.
4) Coverage analysis solutions. When traffic statistics analysis shows that there is
the problem of coverage within a cell, we need to make IOS tracing and import
the traced IOS data to Nastar for coverage analysis. This coverage analysis
includes common downlink pilot channel coverage analysis, link quality analysis,
and overshoot analysis.
5) Interference analysis solutions. Interference analysis helps effectively find out
external interference or internal problems of equipment. By means of
main-diversity signal strength analysis and according to certain algorithms, we
can locate multiple possible causes of radio interference or abnormal signal.
Interference analysis is a small but practical function. It helps on-site engineers
find problems. The master data of interference analysis includes RTWP data,
configuration data, and engineering parameters.
6) Configuration verification
7) CHR analysis means
The advanced functions of the Nastar will not be described further in this document. If
you need them, please query the Help of the Nastar tool and master each function
through repeated practices.
2.5 Summary
Chapter 2 mainly describes the knowledge and skills required for performance
analysis and quality early warning. It includes the understanding of UTRAN signaling
flow and basic principles, the familiarization of the UTRAN KPI and the mastery of the
functions of the Nastar tool. These three parts are associated with each other.
Signaling flow and principles are the very basis. We can understand each PI of a
product only when we have mastered signaling flow and principles. Based on the
familiarization of each PI, we can gradually master each function of this tool through
special topic practice of the Nastar.
Having laid a solid foundation, we can effectively make network performance analysis
and quality early warning by combining the methodology described in Chapter 3.
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3 Three Steps of Performance Analysis and Quality Early Warning
In reality, performance analysis and quality early warning include three steps:
knowledge of network conditions, preparations for performance analysis, and methods
and flows of performance analysis. Among the steps, there is a definite sequential
relationship. Each step helps gradually determine the scope and nature of network
problems. Then, we analyze, conclude and judge whether an early warning to network
quality is needed.
3.1 Step 1: Knowledge of Network Conditions
Case: An engineer undertook responsibility for the performance analysis of a network.
Two weeks later, I consulted him about the trend of voice call drop rate of this network
last month and difference between the call drop rate of workdays and that of holidays.
He answered he did not know. When I asked him what operations of upgrade or
cutover were made in this network last month, he answered he did not know. When I
asked him what modifications were made to the parameters of this network in the past
month, he answered he did not know. This engineer makes network analysis in the
following way: He exports the traffic statistics PIs of this network from the Nastar tool
once a week. Then, he browses various indexes, and gives an analytical conclusion to
those apparently abnormal PIs, such as transmission restricted and power congestion.
For those cells with abnormal PIs and with cause value equal to other, he browses
CHR to look for any clue.
Apparently, such performance analysis is too casual. An analysis and comparison of
performance indexes should be based on early records of this network. We should not
simply make a lateral comparison with other networks or apply baseline indexes
mechanically. The baseline indexes defined by Huawei are only for reference or final
standard requirements. At present, each network has respective coverage and
capacity. Accurate analysis and high-quality early warning must be based on the
present conditions of this network.
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Before making performance analysis, we need to acquire a good knowledge of
present network conditions, including early network performance indexes, modification
records of network parameters, and operation history of networks.
3.1.1 Historic Performance Index of Network
Network performance analysis includes normal performance analysis and specific
performance analysis. Generally, a commercial network focuses on normal
performance. As shown in the following table, normal performance includes traffic
analysis, call completion rate analysis, handover analysis, and call drop rate analysis.
Table 2 Normal performance KPI of network
AMR DL12.2 Erlang
VP DL Erlang
CS Erlang
PS UL Erlang
PS DL Erlang
PS UL Throughput
Traffic
PS DL Throughput
RRC Connection Setup Success Rate (service) (>98%)
RRC Connection Setup Success Rate (other) (>95%)
AMR RAB Assignment Success Rate (>98%)
Video Call RAB Assignment Success Rate (>98%)
Access
PS RAB Assignment Success Rate (>97%)
Soft Handover Factor based on Radio Link Number (<50%)
Soft Handover Success Rate (>99%)
Inter-Freq Hard Handover Success Rate (>95%)
CS Inter-RAT Handover Success Rate (from UTRAN to GSM)
(>96%)
HO
PS Inter-RAT Handover Success Rate (from UTRAN to GSM)
(>92%)
CS AMR Call Drop Rate (<1.5%)
R99
CDR
VP Call Drop Rate (<3%)
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PS Service Drop Rate (<5%)
HSDPA RLC Traffic Volume (MBytes)
HSDPA Mean UE Traffic
HSDPA RLC Throughput (Mbps)
Access HSDPA RAB Setup Success Rate (>97%)
HS-DSCH Service Cell Change Success Rate (with SHO)(>99%)
HS-DSCH Service Cell Change Success Rate (with Intra
HHO)(>95%)
HS-DSCH Service Cell Change Success Rate (with Inter
HHO)(>95%)
HS-DSCH to DCH Handover Success Rate (>95%)
HO
DCH to HS-DSCH Handover Success Rate (>95%)
HS
DP
A:
CDR HSDPA Service Drop Rate (<5%)
Specific performance analysis means that this network has specific functions or
algorithms and that specific attention should be paid to these functions or algorithms.
For example, if network provides HSDPA, HSUPA, and MPMS services, records of
performance indexes must contain corresponding KPI.
For each normal or specific performance which requires continuous observation and
analysis, engineers must keep history. They had better archive them in the form of
visual figures or trend tables (also save corresponding DATA), and update them
anytime. Keeping a record of performance indexes helps an overall observation of the
running quality of a network within a period of time, and makes engineers more acute
to analyze network indexes and judge whether any in-depth location analysis is
needed.
The following trend figure shows the voice call drop rate and VP call drop rate of a
network in a period of time.
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Chart 9. Drop Call Rate
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
3.5%
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05
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Drop Call Rate Voice(3G)
Drop Call Rate Video(3G)
Figure 2 Trend figure of call drop rate
The trend figure clearly shows the call drop trend of this network in the past months.
When we get any new data of call drop rate, we need to compare it with the recent
indexes in this figure to judge whether the call drop rate is abnormal.
In the early days of network commercialization, when indexes were not stable enough,
more information should be recorded for comparison. For example, when analyzing
call drop rate, we may record top 10 cells of a certain day or week. In a subsequent
comparative analysis of call drop rate, we have more pertinent information.
The following table shows the PS call drop analysis of TOP10 cells in a network on a
certain day.
Table 3 PS call drop analysis of top 10 cells
PS Call Drop(2006-08-18) PS Call Drop Rate(2006-08-18)
CellId CellName
PS Call
Drops CellId CellName
PS Call
Drops rate
22192 KingNamH_CDE 116 58681 MKK_A 90.27%
58681 MKK_A 102 16181 Ellen_AB 35.39%
14282 EHTunnl_B 83 16351 ManHong_ABE 40.96%
16351 ManHong_ABE 77 16352 ManHong_CD 35.68%
16352 ManHong_CD 71 22191 KingNamH_AB 61.54%
22191 KingNamH_AB 64 22192 KingNamH_CDE 18.38%
16181 Ellen_AB 63 44441 TsLokEst_AD 36.59%
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PS Call Drop(2006-08-18) PS Call Drop Rate(2006-08-18)
CellId CellName
PS Call
Drops CellId CellName
PS Call
Drops rate
44461 UWTSEst_A 56 44461 UWTSEst_A 30.11%
58111 DyPlzCi_A 40 58111 DyPlzCi_A 90.91%
44441 TsLokEst_AD 30 14282 EHTunnl_B 41.50%
In subsequent analysis of PS call drop rate, we may make a comparative analysis of
top ten cells and observe whether any change has taken place, whether the PS call
drop indexes of these cells rise abnormally. Based on recent network parameter
modifications and network operations, we judge whether any in-depth performance
analysis is needed.
Other KPIs that need a careful observation, such as call completion rate and foreign
handover success rate, need to be similarly recorded as described above.
3.1.2 Parameter Revision History
Parameter revision during network optimization requires clear records. The impact of
parameter revision on networks can be analyzed by combining revision history and
performance indexes of traffic statistics. If traffic is not heavy, the impact of regional
parameter revision on KPI may be unapparent, nor can it be easily observed. But
when traffic rises suddenly some day, if early parameters are unreasonable, the bad
impact of parameter revision on KPI will be clearly seen. A complete record of
parameter revision may contribute to network performance analysis.
For example, the following table shows the revision history of a network. When
creating a parameter revision history table, performance analysis engineers may give
flexible consideration, but the general principle is visual. Thus, query can be made in
the order of revision time. If the revision history involves any specific region, they must
be clearly marked.
Revision of On-Site Baseline Parameters
NO Date Problem Description
1 2006.01.02
Change the maximum permissible uplink transmit power to 24
because some mobile phones support the maximum transmit
power of 24 dBm. Increase this parameter to improve restricted
uplink coverage. See the tables “Cell_SelReselParas_CR” and
“Cell_CACParas_CR”.
2 2006.01.03 Adjust the maximum and the minimum downlink power of voice,
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Revision of On-Site Baseline Parameters
NO Date Problem Description
VP, PS64, PS144, and PS384 according to on-site optimization
to improve network quality and call drop. See the table
“Cell_TrafficPower_CR”.
3 2006.02.04 Change the intra-frequency rerouting starting threshold to -4
dBm. See the table “Cell_SelReselParas_CR”.
4 2006.02.05
Change the admission and congestion parameter settings of
Hong Kong Island. For details, see CELL_CACPara and
CELL_LCCPara.
5 2006.02.06
Change intra-frequency measurement parameters including
Layer 3 filtering coefficient, 1A1B relative threshold, and delay
trigger time and so on. See the table
“Cell_IntraFreqHOMrParas_CR”.
6 2006.02.07
For some cells to tunnels and underground 3G-2G handover
and change of inter-RAT measurement starting threshold and
decision threshold, see the table
“Cell_IntraFreqHOMrParas_CR”.
7 2006.02.08
Turn on the common channel flow control switch of the IUR
interface because an IUR interface is configured between the
RNC1 and RNC2 of the current SUNDAY.
8 2006.03.09
Adjust the inter-frequency power of some cells from 33 dBm to
a smaller value. The reasons are as follows:
NodeB is a 10 W base station and its inter-frequency power is
30 dB.
Share indoor distribution system and RF requirements with
other operators.
In network optimization, the inter-frequency power of some cells
is adjusted to 30 or 28 dBm.
9 2006.03.10 Turn on the UE state transition switch.
10 2006.03.11
The static transition switch is turned off to avoid the possible
call drop caused by some mobile phones not supporting static
transition.
11 2006.03.12
The downlink blind detection switch is turned off to avoid
one-way audio caused by some mobile phones not supporting
blind detection.
12 2006.04.13 T314 and T315 are set to 0. Disable Cell Update caused by
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Revision of On-Site Baseline Parameters
NO Date Problem Description
RLFAILURE.
13 2006.04.14 Change the number of continuous synchronization indication to
1. See the table “CellBasicInfo”.
14 2006.04.15 Change the minimum access quality to -20 dB. See the table
“Cell_SelReselParas_CR”.
15 2006.04.16 Change times of random access preamble retransmission to 20
times. See the table “CellPrachParas”.
16 2006.05.17
To avoid poor streaming quality caused by code transmit power
limit, the maximum service code transmit power of PS 144 is
increased by 2 dB and is the pilot channel power +2 dB. See
the table “Celltrafficpower”.
17 2006.05.18
To check the adjacent cells that miss configuration or potential
adjacent cells, turn on the monitoring set reporting switch. See
the table “SWITCH”.
18 2006.05.19
The uplink BE service rate negotiation threshold is 8K and the
downlink BE service rate negotiation threshold is 64K. See the
table “SWITCH”.
19 2006.06.20
Add cell location configuration information. The maximum
coverage distance of a cell antenna is 500 m. Activate the
AGPS location activation identifier. See “CellSMLCParas”.
20 2006.06.21 The maximum retransmission times of location measurement
can be set to 0. See the table “SWITCH”.
21 2006.07.22 The hard handover hysteresis is 6 (3 dB). 2D trigger time is 640
ms.
22 2006.07.23 NBMULCACALGOSELSWITCH uplink admission switch is
turned off. See the table “SWITCH”.
23 2006.07.24
Change inter-RAT cell reselecting starting threshold
(Ssearchrat) to 3, inter-frequency cell reselecting starting
threshold (Sintersearch) to 5 and intra-frequency cell
reselecting starting threshold (Sintrasearch) to 8.
Figure 3 Revision history of baseline parameters
Baseline parameter records may as well indicate known defects and patches of the
current version. There is no product version without any defect. Sometimes there is a
product BUG. Sometimes there may be restricted algorithm function. The network
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analysis of a certain version demands a good knowledge of the known defects of a
product.
3.1.3 Network Operation History
Network operation records include the cutover of NodeB, the upgrade of RNC and
NodeB, and transmission expansion. They aim to help a comparative analysis of traffic
statistics index and a quick analysis of network performance.
Refer to the following network operation records.
Figure 4 History of network operations
When engineers start performance analysis, they must get related network operation
records. Generally, customers or on-site customer service will maintain a related
record table.
3.2 Step 2: Preparations for Performance Analysis
3.2.1 Starting Time of Performance Analysis and Quality Early Warning
3.2.1.1 Periodic Analysis
In a stable commercial network, performance analysis and quality early warning are
periodic. It generally includes daily report analysis and weekly report analysis. Daily
report analysis ensures timely network monitoring. It helps quickly find and eliminate
any burst KPI deterioration. In daily report analysis, users’ distribution (workdays and
holidays) and their calling habits (commuter time and working time) may cause small
KPI fluctuation in the observed time period. For a region with small traffic, call drop
rate, call completion rate, and handover success rate are of no statistical significance.
We should not analyze network performance problems according to them alone.
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With a week as the unit, weekly report analysis has more statistical sample points.
According to one-week statistics, we may give an accurate early warning to traffic
change, transmission, power, and code resource. Thus, we can more easily find
network problems such as coverage, interference, and pilot pollution.
Performance monitoring requires that the same emphasis should be laid upon daily
report analysis and weekly report analysis. Daily report analysis helps eliminate burst
influence, such as base station reset and intermittent transmission failures. Weekly
report analysis helps locate network coverage problems and interference problems.
Quality early warning actions include comparative check of whole-network parameters,
check of whole-network unidirectional adjacent cells, and check of whole-network
missing adjacent cells and pilot pollution. These actions are periodically executed. The
period can be flexibly set according to the frequency of network parameter
modifications or operations. Quality early warning actions may be fully executed once
a month or a quarter.
3.2.1.2 Trigger Analysis
Normal performance monitoring period takes day as the minimum unit. Use the Nastar
tool to output Daily report to observe network KPI and judge whether an in-depth
analysis is needed. Several scenarios are triggered by events. When a corresponding
event happens, we need to get traffic statistics data and make a detailed analysis. The
granularity of traffic statistics data is generally less than 24 hours. We may need to
analyze the traffic statistics data for half a day (or a whole day) or several hours. In the
following cases, traffic statistics KPI needs our major concern.
1) Important holidays: During important holidays, such as the Spring Festival,
Christmas Day, Buddha’s Birthday, and Pilgrimage to Mekka, the network traffic
of this region will climb to a new high. As to whether product equipment and
network design can withstand large-scale traffic shock, we need to upload traffic
statistics data hour by hour and monitor network performance at any moment.
2) Equipment upgrade and major parameter modification: For general upgrade and
parameter modification, we may analyze the network KPI by observing Daily
report. For highly risky upgrade and parameter modification, we need to get traffic
statistics data quickly and make an analysis with the granularity of 12 or six
hours.
3) Natural disaster: Earthquakes or typhoon may have a direct impact on networks.
To avoid affecting network communication, we need to analyze traffic statistics
data as soon as possible and observe the extent of the damage to networks.
3.2.2 Preparation of Master Data
The master data of performance analysis must be accurate, timely and integral.
Accuracy means that Nastar engineering parameters must be very accurate and will
be updated along with RF adjustment of network. Timeliness means that traffic
statistics data of network needs to be uploaded as soon as possible. Data integrity
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means that no traffic statistics data should be omitted. Otherwise, there may be
relatively fewer call attempts and call drop times of a network or a cell, which cannot
fully reflect network quality.
Specifically speaking, master data includes:
1) Nastar engineering parameters. Multiple analysis functions of the Nastar tool,
such as missing adjacent cell analysis, interference analysis, and coverage
analysis, are closely related to engineering parameters. The accuracy of
engineering parameters determines the credibility of related analysis results of
the Nastar tool.
2) Traffic statistics data
3) Configuration data
4) CHR data. It is not used only for CHR analysis of the Nastar tool. In missing
adjacent cell analysis and unidirectional adjacent cell analysis, CHR data is
needed. If CHR data is only used for abnormal flow location analysis, we may
selectively import CHR data according to the frame number of a cell to be
analyzed.
5) RTWP data (optional). It is chiefly used for interference analysis. It may be
omitted if interference analysis is definitely unnecessary.
6) IOS data (optional). It is used for an in-depth location analysis of many network
abnormality problems, such as coverage.
7) General schedule of engineering parameters (optional). It is required for
geographic analysis.
CHR data records the information generated during a call. It will be recorded in the call
logs of the system if some conditions are satisfied. It may record the signaling flow
status before the call drop of a mobile phone, measurement report information
reported by a mobile phone before call drop and signal condition when a mobile phone
is accessed. In summary, CHR is oriented to all users involved in 3G services and
records the context information of a mobile phone in a conversation. It is output when
preset conditions are satisfied.
IOS sampling tracing is to start measurement oriented to one or more users within a
cell according to preset conditions. Sample data can be set. IOS sampling tracing is
active data collection initiated by users. It may require that a mobile phone should
actively report the measurement reports on the mobile phone side, such as downlink
pilot RSCP and EcIo, or require that NodeB and RNC should report special
measurement information.
In contrast, CHR data traces all the users within a RNC that satisfies tracing conditions.
It covers a large scope. IOS traces one or more users within a specific cell. It covers a
small scope, but goes deeper.
As to the use of RTWP data and IOS data, we generally determine whether to start the
interference analysis and coverage analysis of the Nastar tool for an in-depth
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performance analysis according to early performance analysis. If it is really necessary,
we need to start tracing to get RTWP data and IOS data.
3.3 Step 3: Ideas and Methods of Performance Analysis and Quality Early Warning
This part summarizes the early experiences of multiple commercial networks in
performance analysis, and educes section 3.3.2 “General Idea of Performance
Analysis and Quality Early Warning” from historical experiences. According to the
general idea, section 3.3.3 “Quick Analysis of Some PIs” systematically describes
the methods and procedures of performance analysis.
3.3.1 Conventional Methods of Performance Analysis
For different network problems, there are different methods of performance analysis.
Acquire a good knowledge of the running status and problems of existing network, and
then select one or more proper analytical methods. The commonly used methods of
performance analysis are as follows:
1) TOPN worst cell
According to traffic statistics indexes such as call drop rate, connection success rate,
and soft handover failure rate, get the busy-hour average or all-day average as
required, find out the worst N cells, and make them as the emphasis of fault analysis
and optimization. Or you may determine the priority order of optimization based on
this.
2) Time trend figure
Trend figure of traffic statistics index is a commonly used method of traffic analysis.
Analysis engineers may draw the change trend figure of one or more indexes of the
whole network, Cluster or a single cell by hour, day or week and find the change law of
traffic statistics indexes.
3) Region location
The change of network performance index always takes place in some regions. Traffic
increase, traffic model change, radio environment change, base station faults or
uplink/downlink interference leads to the index variation of these regions. The index
variation affects performance indexes of the whole network. We may compare the
network performance indexes before and after the variation, mark the base station or
sector with the greatest network performance variation on an electronic map, and
make a detailed analysis of problematic regions.
4) Contrast
A traffic statistics index is always affected by multiple factors. Some factors change
while others may not. We may properly select comparison objects, confirm the
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existence of problems and analyze the causes. When observing indexes, we should
not focus on only their absolute values, but on their relative values.
Besides a longitudinal comparison, we should, if necessary, make a latitudinal
comparison of networks in different regions, for example, upgrade. We may refer to
the index change and causes after similar network upgrade.
3.3.2 Analysis Method of Alarm Data
Performance analysis is made by using the Nastar tool while alarm analysis is made
by using the Omstar. In the course of performance analysis, whether at the RNC level
or at the cell level, it is recommended to analyze alarm data first and confirm whether
any related equipment alarm affects PI. If equipment and transmission are both normal,
an in-depth analysis of specific PIs may greatly improve efficiency.
Alarm analysis methods must be used together with KPI analysis. An independent
analysis is meaningless, nor can it solve network quality problems effectively.
Generally speaking, the KPIs in our daily concern are traffic, access performance,
RAB establishment success rate, handover, and call drop. What alarms can these
KPIs be related to? We have simply classified service-related alarms as follows:
Performance of traffic: transmission congestion alarm, broken link alarm, and CE
resource congestion (DSP abnormality alarm)
RRC access performance: related to congestion alarm, such as CN congestion, CPU
congestion, base station baseband congestion, and IUB interface transmission
congestion
RAB establishment success rate: related to transmission congestion and RF coverage
Handover performance: related to clock or resource congestion
Call drop rate: Call drop caused by RF and by unavailability of a cell or a base station
According to the above-mentioned characteristics, we associate KPIs with alarms
while analyzing problems. Then, we analyze traffic statistics indexes to determine
whether alarm is the root cause of the decrease in KPIs. If yes, recover alarm and
check whether performance indexes resume to normal.
In alarm analysis, there is no need to analyze the detailed cause of alarm generation.
We only need to analyze the extent of the impact of this alarm on network
performance. If this alarm does not affect network performance, analyze other
problems. If this alarm does affect network performance, we need to analyze how
alarm is associated with KPIs. If alarm is closely associated with KPIs, we need to
recover alarm to verify the correctness of analysis results. The general process is as
follows:
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Figure 5 Alarm analysis processing flow
Network quality is always affected by one major alarm. In alarm analysis, we will find
that multiple alarms may affect service. Some of them are only accompanying alarms.
We need to distinguish between major alarms and accompanying alarms. Otherwise,
we cannot locate the root cause. The following table shows the impact of commonly
seen alarms on performance and is for your reference in problem solving.
Deterioration of network quality
Collect and analyze alarm
information
Does the alarm affect KPI?
Analysis of
other problems
Does the alarm correlate to the decreased KPI?
Find out and recover major
alarms
Does KPI resume to normal?
End
Yes
Yes
Yes
Yes
No
No
No
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Table 4 Alarm influence
Alarm Type Performance Impact
Trunk alarm
Trunk alarm has a fatal impact on network quality. If network
quality is worsened and there is any trunk alarm, it is generally
believed that it is trunk fault that causes worsening of the network
quality.
There are a variety of trunk alarms. Trunk alarm does not
necessarily lead to the worsening of network quality. This type of
alarm always has numerous accompanying alarms. We need to
combine associated alarms and make an analysis for accurate
location.
Some alarms will make a base station unavailable, thus causing
coverage “hole”. This may not be found from KPIs, but will cause
the cell of the base station adjacent to this base station to have a
greater probability of RF call drop. In the case of a large-scale
network, the impact is concealed. From the perspective of KPIs, it
can only be considered that this falls within the normal fluctuation
range. But the unavailability caused by this type of alarm will
have a bad impact on users’ feelings. Maybe some customers
will make complaints. In this case, we should not make an
analysis only from the association of KPIs with alarm. We need to
focus on whether alarm makes a cell unavailable. The impact of
this alarm on KPI is implicit.
Loopback alarm, configuration alarm, and mismatch alarm do not
appear in network operation, so they do not deserve our
attention. Slip frame overrun alarm and high bit error alarm
depend on specific conditions. If they appear often, they will have
an impact on network quality. If they are seldom generated, it can
be believed that they have no impact on network quality. Among
the RNC alarms, the alarms about APS and MSP have no impact
on service. These are the alarms of additional functions. If they
are not used, this type of alarm does not appear in network
operation. Other alarms, more or less, affect service. They affect
capacity, access, handover, and call drop caused by RF.
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Alarm Type Performance Impact
Signaling alarm
Most alarms may be signaling link alarms caused by trunk alarm.
In analyzing this type of alarm, we need to make clear whether
there is any trunk alarm. If there is any trunk alarm, we need to
analyze them by associating signaling link alarms with trunk
alarms. Note that NodeB categorizes AAL2PATH alarm as a
signaling alarm while RNC categorizes AAL2PATH alarm as a
trunk alarm.
Signaling alarm will unexceptionally have a certain impact upon
service, sometime a fatal impact. For example, NCP/ALCAP
alarm directly causes the unavailability of a base station, so a
coverage “hole” appears. The alarms of MTP3B link, SCCP and
SAAL link will have a direct impact on service availability. If the
link with a core network is interrupted, the link will also be
interrupted between UE and the core network. All related
services become unavailable.
Configuration error alarm, syntactical error alarm, unknown
message, and packet boundary-crossing may appear in
interconnecting partners’ equipment. But they will not affect
existing network quality if other processes are normal. The
system information “11 limiting adjacent cell data” is an event
alarm. Handover is not affected either. Among RNC alarms, there
are some event alarms. If these event alarms are often
generated, they will affect network quality. If they seldom occur, it
can be believed that they do not affect network quality.
QoS alarm
QoS alarm directly affects service communication quality and
KPIs.
For the alarms of NodeB, generally cell blocking appears in
network operation only when this cell is not needed. Therefore,
we need not pay any attention to this type of alarm. Simulated
load starting alarm is used for testing and does not appear in
network operation either. Cell unavailability will directly cause a
coverage “hole”. Call drop caused by RF will also appear. Too
small output power of a cell will also cause coverage problems
and there will be poor coverage in some places. This causes call
drop due to RF. From the perspective of KPIs, call drop rate rises
slightly.
The service alarm of RNC is an event alarm and affects service
slightly. But the loss of a large number of measurement results
may cause some algorithm problems, for example, power control
failure. If event alarms are often generated, they may affect KPIs,
but the impact is limited.
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Alarm Type Performance Impact
Hardware alarm
The alarms which involve a service board and a main control
board may affect service. The alarm of a board other than a
service board does not affect any network quality.
Among the hardware boards of NodeB, all the boards except the
NMON board are related to service. The alarms of these boards
may lead to deterioration of network quality. But the extent of
impact depends on alarm type. A RF board is also related to
service and directly affects quality of the air interface of networks.
All boards of RNC products are basically related to service.
Board hardware fault of the WRSS frame and WRBS frame may
deteriorate network quality. Power alarm and fan alarm do not
affect service. A faulty WGRU board affects location service, but
does not affect any other service or KPIs. Therefore, no
consideration should be given to this for the time being.
Software alarm
Software alarm is generated by the running software part of a
product. It is unrelated to hardware structure, but closely related
to the software structure of the system. Among the software parts
of NodeB and RNC, some involve service while others are not
related to service, but related to equipment maintenance.
Software function alarms related to service need our attention.
Those alarms unrelated to service function do not need our
attention.
In analyzing the software alarm of NodeB, we need not pay any
attention to the alarms of the operation and maintenance part.
Other software alarms are generally unrelated to service and do
not appear in normal network operation. These alarms will be
involved only when there is any operation of system software
upgrade. But generally, the software upgrade of NodeB will
interrupt service.
In the software parts of RNC, the switching subsystem and the
service processing subsystem are related to service, but the
operation and maintenance subsystem is unrelated to service
and may not be considered.
The software alarms of RNC are mostly the alarms of the
operation and maintenance subsystem. That is, they are
associated with BAM database system. Host software alarm is
seldom seen and some are generated during network
construction. The alarms generated during network operation are
the KPIs which only affect network capacity and network access.
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Alarm Type Performance Impact
Running alarm
This type of alarm is generated when the software system runs
abnormally. Most of them are system abnormality caused by
software design defects after long-term running. They may also
be generated when system running exceeds software design
specifications. We need to know about product specifications and
functions before we analyze network quality well. Most alarms
are unrelated to service.
The running alarms of NodeB will mostly be seen during the early
days of network construction. This is because some configuration
has not been fixed yet. These running alarms are seldom seen
during normal operation. LICENSE alarm and DSP/CPU alarm
will affect the capacity, access and handover of the system.
The running alarms of RNC are mostly generated during network
construction because some configuration or parameter settings
are not fully frozen during network construction. These alarms
helps effectively analyze and solve some problems existing
during network construction. They will be eliminated in formal
network optimization to avoid affecting network quality.
Communication
alarm
Communication alarms are mainly internal communication
alarms of a product, especially the maintenance channel
communication between boards. Generally speaking,
maintenance channel fault does not affect any service, but
service channel fault is bound to affect service. When a
communication link generates any alarm, link fault will lead to
corresponding communication interruption.
The internal communication alarm of NodeB does not affect
normal service running.
The communication link of RNC is related to service, so the
interruption of internal links between corresponding boards will
have a certain impact as a trunk alarm does.
Among the communication alarms of RNC, BAM-related link fault
will not affect service, but the alarms which involve a board may
affect service. The impact is fatal and generally leads to the
unavailability of a cell or a base station. Thus, some coverage
“hole” problems appear.
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Alarm Type Performance Impact
Environment
alarm
An environment alarm generally does not affect the service and
KPI of the system. But some environment alarms deteriorate
product performance or functions of some products. They will be
analyzed accordingly. Among the environment alarms of RNC,
GPS antenna alarm affects only location service instead of any
other service.
Power alarm
Generally, power alarm does not affect service at all, but
hardware alarm caused by power alarm may make service
abnormal. This case will be analyzed accordingly.
Processing error
alarm Processing error alarm involves only RNC instead of NodeB.
3.3.3 Quick Analysis of Some PIs
According to the values of indexes, we can quickly analyze network performance
based on the following PIs:
� Capacity PIs, such as downlink capacity, uplink capacity, effective utilization of
codes, and bandwidth utilization
� Transmission index, such as aal2path
� Cell unavailability duration VS.Cell.UnavailTime.OM
Before using the Nastar tool for an in-depth analysis, we may export the
above-mentioned commonly seen PIs and judge whether there is any problem with
network. This analysis method may greatly improve efficiency, but is not systematic
enough.
3.3.4 Commonly Seen PIs and Corresponding Analysis Idea
1) Among the causes of call drop, if VS.RAB.Loss.CS.RF.RLCRst,
VS.RAB.Loss.CS.RF.ULSync, VS.RAB.Loss.CS.RF.DLSync, and
VS.RAB.Loss.CS.RF.UuNoReply take a large proportion, we should first analyze
RF problems.
2) Judge whether overload leads to abnormal release.
If VS.RAB.RelReqCS.RABPreempt leads to call drop for many times, it can be
confirmed that the cell load has reached the admission threshold. If congestion
makes many users released, it can be confirmed that the load of this cell has
reached the congestion threshold. We may also make an analysis by associating
call drop times with the downlink load of a cell. If the downlink load of a cell is high
within the period with much call drop (by viewing the indexes VS.MeanTCP,
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VS.MinTCP, and VS.MaxTCP, or starting the downlink transmit power
measurement of this cell), start load problem analysis.
3) If call drop rate of the whole network suddenly becomes relatively high, generally
the following factors may lead to this and we need to make the following check: (1)
Iu interface transmission analysis: analyze alarms to see whether there is any
problem with the transmission for the Iu CS interface and the Iu PS interface. (2)
RNC equipment analysis: analyze alarms to see whether RNC boards reset and
whether there is any equipment fault. (3) whole-network traffic analysis: Find out
whether sudden increase in registered users and traffic leads to the increase in
call drop rate and check whether the system is upgraded or patched.
…
In dealing with special topic exercises, Chapter 2 points out that there is need to
summarize the relationship between traffic statistics PIs and network problems
(section 2.4.1). This section summarizes commonly used experiences in analysis of
commercial networks. It also expounds the analysis idea of commonly seen PIs. The
abstraction of this experience forms the following parts:
3.3.5 General Idea of Performance Analysis and Quality Early Warning
By referring to the historical experience of performance analysis and considering the
analysis functions provided by the Nastar tool and the Omstar tool, we may
summarize the principles of performance analysis and quality early warning: gradually
narrow the scope of problems and define the nature of problems from the
macroscopical to the microscopical and from the whole to the part. For the problems of
different nature, we use respective functions of the Nastar tool for an in-depth analysis
and thus obtain analysis results.
Concretely speaking, the analysis idea can be summarized as follows:
1) First analyze RNC whole-network indexes macroscopically, and observe daily
reports and weekly reports to check whether KPIs are normal. Then, query other
PIs or cell indexes.
2) If KPIs are abnormal, it is recommended to make a comparative analysis of
TOPN cells and TOPN users. Observe whether regional deterioration or some
users leads to the decrease in whole-network KPIs and whether integral indexes
of network decrease. If there are a small number of on-net users, the abnormality
of an individual user or cell may probably affect whole-network KPI performance.
This is especially apparent in PS service.
3) If integral indexes of the network decrease, we need to analyze whether there is
any problem with RNC equipment or whether IU interface transmission is
restricted.
4) Whether RNC-level analysis or cell-level analysis, it is recommended to check
alarms first to make sure whether there is any problem with equipment and
transmission.
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5) After defining the nature of problems, properly use different functions of the
Nastar tool for an analysis.
3.3.6 Procedures and Methods of Performance Analysis and Quality Early
Warning
3.3.6.1 Flowchart of Performance Analysis Procedures
According to the general idea, we may determine the specific procedures of
performance analysis and quality early warning. It is mentioned in 3.2.2 “Preparation
of Master Data” that RTWP data and IOS data can be obtained only if there is specific
tracing, and is needed only at a specific stage of performance analysis.
The following flowchart shows the main procedures of performance analysis, but the
performance analysis flow is not completely a one-way process. From the perspective
of time, performance analysis is also a day-after-day process of gradual analysis,
repeated optimization and continuous observation. After a problem is analyzed,
possibly there is need to adjust parameters, increase transmission and solve
equipment problems. Upon finishing network optimization and network maintenance,
continue observing network indexes, contrastively adjust traffic statistics performance,
and confirm the effects after the change. From the perspective of flow, we may omit
some procedures or lay an emphasis upon the observation of a certain part according
to on-site scenarios.
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Figure 6 Performance analysis flow
(1) Overall analysis of network KPI
Is there any KPI deterioration?
(2) RNC equipment/IU transmission/parameter
Is there any equipment
problem/transmission fault?
(3) KPI analysis of TopN cells
Is there any cell equipment problem?
Solve RNC equipment/IU transmission problems.
Solve cell equipment problems
(5) Analysis of cell load problems
Is there any overload problem?
Whole-network traffic statistics
Traffic statistics Alarm
Cell traffic statistics
(4) Analysis of cell-related equipment
Cell traffic statistics RNC and Node B alarm
Traffic statistics: IUB bandwidth CE resource Equipment resource Radio resource
Solve overload problems
A
END
Y
N
N
Y
Y
N
N
Y
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Figure 7 Performance analysis flow (Continued)
(6) Analysis of cell interference problems
Is there any interference
problem? Solve cell interference problems
A
CHR: NodeB RTWP Cell load information Special interference analysis
(7) Analysis of cell coverage problems
Is there any coverage problem?
CHR: Pilot pollution Extraction of coverage information IOS Trace: Analysis of cell coverage quality
Solve cell coverage problems
(8) Analysis of cell parameter problems
Is there any parameter problem?
CHR: Optimization of adjacent cells Configuration verification Parameter optimization
Solve parameter problems
(9) CHR flow/terminal performance
Is there any terminal performance
problem? Terminal defect list
CHR: Statistical analysis of mobile phone problems
B
N
Y
Y
N
Y
N
Y
N
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1) Overall analysis of network KPI
� Step 1 of performance analysis and quality early warning is to make an overall
analysis of network KPIs. The KPIs include, but are not limited to traffic, call
completion rate, handover success rate, and call drop rate, shown as follows. For
those which contain specific services, such as HSDPA and CMB, or specific
algorithms, we also need to observe the integral indexes of corresponding KPIs.
� Analyze the KPI of daily report or weekly report as required. From WCDMA
Performance Monitoring Report output by the Nastar tool, we can also obtain a
visual overall analysis.
� The judgment of whether the KPI is abnormal must be based on the comparison
with early history. We may observe the extent of relative change instead of the
absolute value of the KPI.
� When there is no apparent change in the KPI, there are two processing modes:
End the current performance analysis and analyze TOPN cell. When there are a
large number of network cells, the performance deterioration of very few base
stations may not apparently affect the overall network KPI. These abnormal cells
can be found out by contrasting TOPN analysis.
� When the relative value of the KPI is not apparently changed but its absolute
value always cannot reach standards and no analysis conclusion has been drawn,
we need to analyze specific causes according to traffic statistics data and
conduct quality early warning.
Table 5 Overall analysis of network KPIs
AMR DL12.2 Erlang 13.08 (11:00–12:00)
VP DL Erlang 0.39 (17:00–18:00)
CS Erlang 15.86 (18:00 – 19:00)
PS UL Erlang 167.19 (21:00–22:00)
PS DL Erlang 554.03 (21:00–22:00)
PS UL Throughput 2675.06 (21:00–22:00)
Traffic
PS DL Throughput 8864.55 (21:00–22:00)
RRC Connection Setup Success Rate
(service) (>98%) 99.78% (135343/135638)
RRC Connection Setup Success Rate
(other) (>95%) 99.31% (170930/172122)
R99
Access
AMR RAB Assignment Success Rate
(>98%) 99.66% (18595/18659)
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Video Call RAB Assignment Success
Rate (>98%) 99.57% (230/231)
PS RAB Assignment Success Rate
(>97%) 99.59% (95524/95918)
Soft Handover Factor based on Radio
Link Number (<50%) 22.66%
Soft Handover Success Rate (>99%) 99.72% (318538/319439)
Inter-Freq Hard Handover Success
Rate (>95%) N/A (0/0)
CS Inter-RAT Handover Success Rate
(from UTRAN to GSM) (>96%) 98.76% (6198/6276)
HO
PS Inter-RAT Handover Success Rate
(from UTRAN to GSM) (>92%) 96.10% (44834/46653)
CS AMR Call Drop Rate (<1.5%) 0.35% (66/18595)
VP Call Drop Rate (<3%) 0.87% (2/230) CDR
PS Service Drop Rate (<5%) 5.08% (4854/95524)
HSDPA RLC Traffic Volume (MBytes) 19373
HSDPA Mean UE 68.18 (18:00–19:00) Traffic
HSDPA RLC Throughput (Mbps)
Access HSDPA RAB Setup Success Rate
(>97%) 98.24% (14360/14617)
HS-DSCH Service Cell Change
Success Rate (with SHO) (>99%) 99.73% (10391/10419)
HS-DSCH Service Cell Change
Success Rate (with Intra HHO) (>95%) N/A
HS-DSCH Service Cell Change
Success Rate (with Inter HHO) (>95%) N/A
HS-DSCH to DCH Handover Success
Rate (>95%) 99.38% (961/967)
HO
DCH to HS-DSCH Handover Success
Rate (>95%) 83.28% (792/951)
HS
DP
A
CDR HSDPA Service Drop Rate (<5%) 1.39% (200/14360)
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2) Analysis of RNC equipment problem/IU transmission problem/parameter
� RNC equipment problem and IUR interface transmission problem may affect the
whole-network KPI.
� IU interface transmission problem and core network problem will affect the
whole-network KPI directly.
� If the performance indexes of network cells are universally deteriorated, basic
causes are related to the RNC board reset and restricted IU interface
transmission. Equipment problems and intermittent transmission failure can be
checked by the Omstar tool. Transmission bandwidth restricted can be checked
by observing transmission-related PIs from traffic statistics.
� Another case of affecting the overall KPI of RNC: RNC-level parameter change. If
the whole-network KPI becomes apparently abnormal, we need to make sure
whether any RNC-level parameter change has been made recently and carefully
check the impact of this parameter on the network.
3) KPI analysis of TOPN cell
� The number of TOPN cells can be increased according to the network scale. The
number of the Nastar tools is 10 by default. If there are too few TOPN cells, some
cells with abnormal performance may be ignored.
� The WCDMA Performance Monitoring Report output by the Nastar tool lists the
TOPN with normal KPIs. According to this report, we may pick out important cells
from TOPN cells and make an in-depth analysis.
� A comparison of the indexes of TOPN cells with those of history TOPN cells helps
judge whether cell performance indexes are normal. It is recommended to use
the above-mentioned trend analysis figure for comparison. Make sure whether
TOPN cell Id changes and what the amplitude of change in TOPN cell KPI is. This
is simple but visual.
� TOPN cell problems must be analyzed together with cell traffic. For example, a
pure observation of the call drop rate of a cell is meaningless. If a cell has one call
drop, but there is only one call attempt, the call drop rate is 100%.
4) Cell equipment analysis:
� Cell equipment analysis means analyzing the equipment of TOPN cells of last
step. Likewise, subsequent load problem analysis and interference problem
analysis are oriented to TOPN cells.
� The equipment that affects cell performance KPI includes the antenna feeder
equipment and the uplink/downlink processing board of a base station. Generally,
related equipment alarms can be observed either on the NodeB side or on the
RNC side.
� The transmission restricted and intermittent transmission failure of a base station
will affect related cell indexes. Intermittent transmission failure is observed by
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using the Omstar tool. We make an auxiliary analysis by using the cell
unavailability PI (VS.Cell.UnavailTime.OM) provided by the Nastar tool.
5) Analysis of cell load problems
� The indexes directly related to cell load include average uplink/downlink occupied
CE of a cell (VS.LC.ULCreditUsed.CELL/2, VS.LC.DLCreditUsed.CELL) and the
maximum uplink/downlink occupied CE (VS.LC.ULCreditUsed.CELL.Max/2,
VS.LC.DLCreditUsed.CELL.Max). When the maximum uplink/downlink occupied
CE approaches 128 or the average occupied CE is around 60, expansion should
be considered.
� Causes for cell load problems include: change of traffic model; the main coverage
service of this cell is designed to be VP64, but actually there are a large number
of 384k services. During holidays, relatively concentrated population leads to the
increase in traffic.
� High load may cause CE congestion, power congestion, code congestion, and
transmission congestion. We should make an analysis by observing
corresponding PI.
� In load problem analysis, when much power congestion occurs, actual load is not
necessarily very high. In this case, we need to analyze admission strategy and
judge whether admission parameters are properly set.
6) Analysis of cell interference problems
� Causes of interference: UE self-correlation interference. If there are many UEs in
a conversation within a cell, interference will increase. Interference is also caused
by external interference source and by pilot pollution.
� Whether there is any uplink interference within a cell can be judged by observing
the RTWP indexes in traffic statistics, that is, the average RTWP of a cell and the
maximum RTWP of a cell. If the average RTWP of a cell is as high as -95 dBm or
higher, it is possible that there is uplink interference. Observe the maximum
RTWP. If RTWP peak, such as -70 dBm, is often seen, the cause may be the
power of access process or handover process.
� An in-depth interference analysis requires that the interference analysis function
of the Nastar should be started. If a cell has severe interference, we need to trace
its RTWP data. Import the RTWP data, configuration data and engineering
parameter to the Nastar tool, and start the interference analysis function. In this
way, we can effectively find external interference or internal equipment problems.
This function locates multiple possible causes of radio interference or abnormal
signals by analyzing main-diversity signal strength and according to certain
algorithm categorization.
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7) Analysis of cell coverage problems
� Coverage problems include poor coverage, excessive coverage, pilot pollution,
and missing configuration of adjacent cells.
� Poor coverage leads to poor performance of an air interface. In traffic statistics, a
large number of PIs, such as RF.RLCRst, RF.ULSync and UuNoReply, are
related to poor coverage.
� For an in-depth analysis of poor coverage and excessive coverage, we need to
provide the IOS data of the analyzed cell and enable the coverage analysis
function of the Nastar to make a statistical analysis of the coverage strength of
the pilot and the link quality of service.
� Pilot pollution analysis does not need any IOS data. The pilot pollution analysis
function of the Nastar tool needs CHR data, engineering parameter, configuration
data, and traffic statistics data. The principles of pilot pollution analysis are to
make statistics according to 1C measurement reports and signal quality of active
set and monitoring set when 1C reports are reported, together with the number of
branches of cell power splitting output in engineering configuration parameters.
� The intra-frequency adjacent cell check of the Nastar tool can be fully used to find
those adjacent cells that miss configuration. In using this function, we need to
turn on the detection set reporting switch. The principles of this function are to
judge whether any adjacent cell misses configuration by making statistics of
detection set reports and cell signal strength reported.
8) Analysis of parameter problems: (What factors lead to parameter change?
Insufficient bandwidth, missing configuration of adjacent cells, comparison of
cutover tool with the Nastar tool)
� If the KPI deterioration of a cell is not closely related to equipment, load,
interference or coverage, we need to check cell parameters carefully.
� We need to make sure whether the history (see 3.1.3 “Network Operation
History”) of network operations contains any parameter adjustment related to this
cell, including adjustment of adjacent cell relationship and RF parameter
adjustment. If cell parameter adjustment has been made recently, we need to
make a careful analysis. Meanwhile, the impact of early parameter adjustment on
the recent KPI should not be eliminated. We also need to check whether there is
a big increase in the traffic of this cell. If traffic increases sharply, the
unreasonableness of cell parameters will be easily found.
� The configuration verification function of the Nastar tool can help quickly check
the parameter changes of the same version made on a different day.
9) Analysis of CHR process and terminal performance problems
� The prerequisite to network planning performance analysis is stable product
performance and normal equipment. But the bug of actual networks and products
always exists. We need to define whether the problem lies in product
implementation through performance analysis.
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� In the early performance analysis, many RAN equipment problems have been
found. In cell performance analysis, sometimes abnormal access or call drop still
occurs even if there is no high load, a cell has normal signal coverage and there
is correct parameter configuration. In this case, we need to enable the CHR
analysis function of the Nastar tool and use signaling process to make an
analysis. The dot information of CHR involves the implementation of a product
internal module. CHR analysis does not aim to accurately locate a problem, but to
determine the scope of the problem and failure location of abnormal processes.
Then, feedback the result to product R&D personnel to provide auxiliary
information about the location by the R&D personnel.
� Besides RAN equipment problem, terminal problems cannot be excluded in
performance analysis. Many of them have been found in an actual network.
Sometimes, a terminal transmits at a fixed power and the conditions that a
terminal satisfies measurement reports fail to be reported in time. For the sake of
query, terminal problems found in existing network can be classified and included
in a list.
� RAN equipment problems and terminal problems seldom appear, therefore they
are put at the end of performance analysis. In analyzing abnormal PIs, after
excluding multiple possible causes, we should dare to doubt equipment problems
and give reasonable evidence based on CHR.
3.3.6.2 Proper Use of Functions of the Nastar
The previous section describes the processes and procedures of performance
analysis. In one word, performance analysis is proper use of the Nastar tool. This
document first describes performance analysts’ necessary skills and then expounds
related preparations for performance analysis. Finally, one thing is certain. That is, we
should know how to analyze a complex network by using a specific function of the
Nastar.
The Help document of the Nastar tool describes main related functions of the Nastar:
� Quick index query
� Output reports based on a template
� Coverage analysis, interference analysis, and configuration verification analysis
A tool is only a platform. How to make an effective analysis with this tool requires
continuous summarization of experiences. Now take for example the analysis of RRC
establishment success rate and RAB establishment success rate to expound when the
Nastar functions should be used in performance analysis. This serves as the example
of performance analysis methods.
The Nastar functions are described in section 2.4.2 “Mastery of Advanced Functions
of the Nastar Tool”. For the sake of the figure analysis as follows, these functions are
summarized as [Query Function], [Customization Query], [Daily Report Output],
[TOPN Query], [Coverage Analysis], [Cross Coverage], [Missing Configuration of
Adjacent Cell], [Load Analysis], [Interference Analysis], and [Configuration Verification].
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The difference between [Query Function] and [Customization Query] is that the former
can be directly exported from the performance analysis template of the Nastar tool
while the latter is customized as required.
1. Performance analysis of RRC establishment success rate
Query TOPN cells with the most RRC establishment failures with the Nastar. Make the
following performance analysis in terms of each TOPN cell.
Figure 8 Performance analysis of RRC establishment success rate
1) [Daily Report Output] Use a network optimization tool to analyze RNC traffic
statistics data, output daily reports and get related indexes of RRC establishment
success rate, mainly including RRC establishment success rate of service and
non-service.
2) Judge whether the KPI satisfies network requirements according to the defined
threshold or a comparison of the history.
2. Do indexes satisfy the
requirements?
3. Subdivide into cell equipment
problems
4. Query equipment alarm
5. Coverage quality problem
9. Cell reselecting problem
11. Overload admission problem
6. Ec/Io analysis
7. Overshoot analysis
8. Missing configuration of
adjacent cell
10. Analysis of adjacent cell
coverage quality
12. Load and interference
analysis
Y
N
Y
N
1. Query RRC establishment by using the
network performance analysis function
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3) [TOPN Query] Subdivide RNC-level indexes into cell-level indexes and find out
10 cells with the worst indexes.
4) [Customization Query] and [Omstar query] Customize the unavailability indexes
of the queried cell or find equipment alarm information with the Omstar, and judge
whether the problem lies in equipment or transmission.
5) [Customization Query] Query results indicate that possible performance problems
include coverage problems, cell reselecting problems and admission problems
(We need to determine the type of problems according to the previous basic KPI
analysis. Then, we use the Nastar tool for a corresponding analysis.)
6) [Coverage Analysis] Enable cell coverage quality analysis to exclude coverage
problems.
7) [Overshoot Analysis] Enable overshoot analysis to exclude possible overshoot.
8) [Missing Configuration of Adjacent Cell] Enable the analysis of missing adjacent
cells to exclude the possibility of missing configuration of adjacent cells.
9) [Configuration Verification] Enable parameter analysis to exclude parameter
configuration problems.
10) [Coverage Analysis] Adjacent cell coverage quality analysis.
11) [Customization Query][Configuration Verification] Query the PIs with load
admission failure and check parameters to judge whether load admission is too
high.
12) [Customization Query][Interference Analysis] Query cell load PIs or enable the
interference analysis function to eliminate interference problems and overload
problems.
2. Performance analysis of RAB establishment success rate
Query TOPN cells with the most RAB establishment failures by using Nastar. Make the
following performance analysis in terms of each TOPN cell.
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Figure 9 Performance analysis of RAB establishment success
1) [Query Function] First use the network performance analysis and query function
of a network optimization tool to query the RAB establishment success rate of
various RNC-level services, including AMR service, VP service, and PS service
with a typical rate.
2) Judge whether each RAB establishment KPI satisfies requirements based on the
history.
3) [TOPN Query] Subdivide RNC-level indexes into cell-level indexes and find out
10 cells with the worst indexes. Among cell-level indexes, some statistical points
of RAB establishment failure can be used for the isolation of equipment problems
or network performance problems.
4) [Customization Query] or [Omstar tool query] We can use the Omstar tool to
query equipment problems or transmission problems. We may customize PI
query, for example, query the index VS.Cell.UnavailTime.OM.
2. Do indexes satisfy the
requirements?
3. Subdivide into cell equipment
problems
4. Query equipment
alarm
5. Coverage quality
problems
8. Intra-frequency
handover problem
10. Overload admission
problems
6. Ec/Io
analysis
7. Missing configuration of
adjacent cell
9. Analysis of adjacent cell
coverage quality
11. Load and interference
analysis
Y
N
Y
N
1. Query RAB establishment success rate by using the performance
analysis function
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5) [Customization Query] RAB failure causes can be categorized as coverage
problems, handover problems and overload rejection problems. For the standard
for the categorization, refer to Table 1 in section 2.4.1.
6) [Coverage Analysis] Enable cell coverage quality analysis to exclude coverage
problems.
7) [Missing Configuration of Adjacent Cell] Enable the analysis of missing adjacent
cells to exclude the problem of missing configuration of adjacent cells.
8) [Customization Query] Query related PIs to make sure whether the problem lies
in handover.
9) [Configuration Verification] Enable parameter optimization analysis to exclude
handover parameter configuration problems.
10) [Customization Query] Query related PIs to make sure whether there is any
overload.
11) [Customization Query] and [Interference Analysis] Query load-related PIs and
enable interference analysis to exclude interference problems and overload
problems.
3.3.6.3 Routine Analysis and Quality Early Warning
This document does not distinguish between performance analysis and quality early
warning. Quality early warning is defaulted to occur during performance analysis. We
confirm whether quality early warning is necessary according to performance analysis
results.
Quality early warning includes performance KPI deterioration early warning and
potential quality risk early warning. When any KPI deterioration is found during
performance analysis, we give a timely early warning, find network problems and
optimize network to avoid continuous deterioration of network performance. Potential
risk early warning is not driven by any KPI deterioration event. Therefore, we need to
make routine network check according to certain rules and give an early warning to
those that do not conform to rules.
Routine analysis and quality early warning include the following aspects:
1) Check unidirectional adjacent cells. Normally, the intra-frequency adjacent cell
relationship of the UMTS network is configured as bi-directional. If some cells are
only configured with unidirectional adjacent cell relationship, we need to give an
early warning to those scenarios that cannot give special reasons for their
particularity.
2) Check the adjacent cells that miss configuration. Using the missing adjacent cell
check function, regularly check whole-network adjacent cell relationship. We
need to give an early warning to the adjacent cells that apparently miss
configuration.
3) Check RTWP. Regularly check the average RTWP and the maximum RTWP of
whole-network cell. It is found from actual network that some cells have a
relatively high RTWP, but their call drop rate and call drop times are not
necessarily quite deteriorated. No matter what the KPI performance of a cell is,
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we need to give an early warning to the cells with a relatively high RTWP and find
out corresponding causes.
4) Check pilot pollution. Actual measurement and theoretical analysis have given us
a conclusion. Pilot pollution is not necessarily linked to call drop, but we need to
optimize the regions with severe pilot pollution. We should regularly check
whole-network pilot pollution with the Nastar and give an early warning to the
regions with severe pilot pollution.
Routine check is also based on the basic query function and advanced special topic
function of the Nastar. Its period can be flexibly set according to existing network
conditions. For example, routine check can be made once a month or a quarter.
Another trigger factor of routine check and quality early warning is network cutover.
When large-scale relocation and cutover occur in a network, be sure to make routine
check by using the configuration verification function and missing adjacent cell check
function of the Nastar. The complexity of the UMTS network parameters determines
the fact that whole-network check is necessary in case of large-scale relocation. A
quality early warning should be given as soon as possible to parameter inconsistency
or parameter omission.
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4 Observation Point and Analysis Examples of Typical Problems
An observation point is a PI which reflects a specific performance problem. The
analysis based on an observation point is a process that goes deeper based on the
familiarization of the UTRAN PI. Observation point analysis associates signaling
process with performance index. Observation points are categorized as follows:
1) RRC establishment analysis observation point
2) RAB establishment analysis observation point
3) Soft handover analysis observation point
4) Call drop analysis observation point
5) CS/PS intersystem handover analysis observation point
6) Traffic analysis observation point
7) Key interface process analysis observation point
8) HSDPA analysis observation point
An in-depth performance analysis can be made only after you have gained a mastery
of observation points. The Nastar tool provides special topic query of most observation
points. We may also make special topic query of other observation points by means of
customization. Special topic drilling analysis of basic observation point helps deepen
the understanding of signaling processes and various PIs and strengthen the mastery
of the Nastar tool.
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Figure 10 Special topic analysis
4.1 Observation Points of Typical Problems
4.1.1 RRC Establishment Analysis Observation Point
Table 6 RRC Establishment Observation Point
Observation
Point Condition
Possible
Cause Analysis Idea
Categories of
RRC
establishment
requests
Observe various
types of RRC
connection
establishment
requests and
their proportional
distribution. If any
abnormality, we
need to give an
early warning.
If there are many streaming class called
service requests (accounting for over 10%
of total connection establishment
requests), we need to pay much attention
to them. This is because when UE changes
from DCH status into IDLE status, PS
needs to transmit packets, then ps paging
occurs and the corresponding RRC
requests are streaming class called service
requests. If there are too many requests of
this type, it is possible that the timer from
DCH status to IDLE status is not properly
set.
AAL2
establishment
failure
It is generally caused by insufficient
transmission resource or transmission
fault. You may query the cell downlink
throughput at the moment from associated
traffic statistics indexes. If it is lower than
200 kbps, transmission fault may occur.
RRC
establishment
failure
Number of RRC
connection
establishment
failures (>=5);
RRC connection
establishment
failure rate
(>=10%)
RL
establishment
failure
It may be caused by NodeB fault or
insufficient NodeB resource. You may
query the maximum downlink CE of a cell
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Observation
Point Condition
Possible
Cause Analysis Idea
from associated traffic statistics index. If
the maximum uplink CE is less than 20,
then traffic is not high and the problem lies
in abnormal NodeB equipment.
Power
congestion
RRM admission decision cannot establish
any new RRC connection due to too high
radio load within a cell. In this case, you
need to query the maximum RTWP and the
maximum TCP of the cell to confirm uplink
congestion or downlink congestion and
judge whether any expansion is necessary.
Meanwhile, we should check whether
related admission strategy settings, such
as DCCC, are proper.
Uplink CE
congestion
Uplink CE resource admission congestion
within an RNC. You need to query the
number of uplink CEs of a cell from
relevant parameters and judge whether to
expand CE. If the number of uplink CEs is
less than 20, then traffic is not high and the
problem may lie in abnormal NodeB
equipment.
At present, RNC does not make an
accurate estimate of CE resource. It is
quite possible that RNC judges CE to be
sufficient, but actual NodeB CE resource is
insufficient. In addition, inconsistent
capability of RNC and NodeB may also
lead to NodeB RL establishment failure.
Downlink CE
congestion
Downlink CE resource admission
congestion within an RNC. You need to
query the number of downlink CEs of a cell
from relevant parameters and judge
whether to expand CE. If the number of
uplink CEs is less than 40, traffic is not high
and the problem may lie in abnormal
NodeB equipment.
At present, RNC does not make an
accurate estimate of CE resource. It is
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Observation
Point Condition
Possible
Cause Analysis Idea
quite possible that RNC judges CE to be
sufficient, but actual NodeB CE resource is
insufficient. In addition, inconsistent
capability of RNC and NodeB may also
lead to NodeB RL establishment failure.
Code
congestion
Code resource fails to be allocated during
RRC connection establishment. Code
congestion is generally caused by too
many network users. It may be seen in high
traffic scenarios with microcell coverage.
You may query the effective utilization of
codes from associated traffic statistics
indexes. If the effective utilization of codes
is lower than 30%, it is possible that the
code distribution algorithm is abnormal.
Other
congestion
leads to RRC
rejection.
Generally the congestion caused by
unknown insufficient resources. For
example, license resource and high CPU
utilization make flow control and FMR
processing capacity insufficient. In addition,
E1 fault also appears. This cause value is
dotted.
Transmission
congestion
Transmission congestion is mainly caused
by insufficient transmission resource. You
may query the downlink cell throughput
from associated traffic statistics indexes. If
the downlink cell throughput is lower than
200 kbps, it is possible that there is
abnormal equipment. The power-down of a
base station once led to transmission
interruption, but the cause in traffic
statistics is transmission congestion.
Other factors
lead to RRC
rejection.
Abnormal causes. We need to make
in-depth location based on RNC logs. The
known problem is that the system
redirection function of the network is
enabled. During redirection, a mobile
phone does not support GSM and thus
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Observation
Point Condition
Possible
Cause Analysis Idea
failure rejection occurs.
No response
from UE
This is generally caused by poor coverage.
The downlink FACH and RACH have
unbalanced coverage.
Other factors
lead to RRC
establishment
failure.
This is generally caused by an RNC fault.
At present, there is a problem with traffic
statistics mode, which may lead to some
wrong dotting of this cause.
There was a problem with the designated
access DSP of node B. The RRC
CONNECTION SETUP REQUEST
message fails to be sent to RNC. The
RACH packet decoding of this cell fails. We
may make a judgment by checking whether
the index
VS.MAC.CRNCIubBytesRACH.Tx is
abnormal.
4.1.2 RAB Establishment Analysis Observation Point
Table 7 RAB establishment observation point
Observation
Point Condition
Possible
Cause Analysis Idea
Transmission
network
Generally transmission equipment fault or
insufficient transmission capacity. You
need to query the transmission utilization of
that time.
Migration
In starting migration, RNC receives a RAB
establishment request, but does not
process it. This is mainly caused by flow
nesting and seldom occurs. It is related to
user behavior sequence. This is generally
avoided in a core network.
CS/PS RAB
establishment
failure
Number of
CS/PS RAB
establishment
failures (>=5);
CS/PS RAB
establishment
failure rate
(>=10%)
Power
congestion
RRM admission decision cannot establish
any new RRC connection due to too high
radio load within a cell. In this case, you
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Observation
Point Condition
Possible
Cause Analysis Idea
need to query the maximum RTWP and the
maximum TCP of the cell to make sure of
uplink congestion or downlink congestion
and judge whether any expansion is
necessary. Meanwhile, we should check
whether related admission strategy
settings, such as DCCC, are proper.
Uplink CE
congestion
Uplink CE resource admission congestion
within an RNC. You need to query the
number of uplink CEs of a cell from
relevant parameters and judge whether to
expand CE. If the number of uplink CEs is
less than 20, then traffic is not high and the
problem may lie in abnormal NodeB
equipment.
At present, RNC does not make an
accurate estimate of CE resource. It is
quite possible that RNC judges CE to be
sufficient, but actual NodeB CE resource is
insufficient. In addition, inconsistent
capability of RNC and NodeB may also
lead to NodeB RL establishment failure.
Downlink CE
congestion
Downlink CE resource admission
congestion within an RNC. You need to
query the number of downlink CEs of a cell
from relevant parameters and judge
whether to expand CE. If the number of
uplink CEs is less than 40, then traffic is not
high and the problem may lie in abnormal
NodeB equipment.
At present, RNC does not make an
accurate estimate of CE resource. It is
quite possible that RNC judges CE to be
sufficient, but actual NodeB CE resource is
insufficient. In addition, inconsistent
capability of RNC and NodeB may also
lead to NodeB RL establishment failure.
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Observation
Point Condition
Possible
Cause Analysis Idea
Code
congestion
Code resource fails to be allocated during
RRC connection establishment. Code
congestion is generally caused by too
many network users. It may be seen in high
traffic scenarios with microcell coverage.
You may query the effective utilization of
codes from associated traffic statistics
indexes. If the effective utilization of codes
is lower than 30%, it is possible that the
code distribution algorithm is abnormal.
Transmission
congestion
Transmission congestion is mainly caused
by insufficient transmission resource. You
may query the downlink cell throughput
from associated traffic statistics indexes. If
the downlink cell throughput is lower than
200 kbps, it is possible that there is
abnormal equipment. The power failure of
a base station once led to transmission
interruption, but the cause in traffic
statistics is transmission congestion.
Others Abnormal causes. We need to make an
in-depth location based on RNC logs.
Air interface
failure
The air interface failure occurring during
RB establishment is generally caused by
poor coverage or mobile phone
compatibility.
Configuration
not supported
The compatibility of a mobile phone itself
becomes faulty in some unknown
scenarios. For example, when a Huawei
mobile phone drops network abnormally, it
may not release any RB. When PS RB is
set up next time, this case may occur. This
case also happens to the SE V800 mobile
phone.
Physical
channel failure
This generally occurs when FACH migrates
to DCH and sets up RB. The downlink
physical layer of a terminal is not
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Observation
Point Condition
Possible
Cause Analysis Idea
synchronized, which leads to RB
establishment failure. This is mainly caused
by poor coverage.
Cell update
The Cell Update flow occurs during RB
establishment. This nested flow leads to
RB establishment failure.
Illegal
configuration
UE considers parameter configuration
illegal. Network and terminals have an
inconsistent understanding of parameter
processing. If RB establishment failure
occurs in the domain of CS, it is possible
that a user dials a wrong telephone number
and at once goes onhook. RB SETUP
failure may also occur at this time. The
cause is illegal configuration.
No response
from UE
Generally poor coverage makes UE unable
to receive any RB establishment command.
Parameter error
RNC considers the parameter delivered by
a core network invalid. You need further
cell signaling tracing to determine the
cause. Among the known causes is that the
uplink subscription and activation
application information of user PS service
exceeds the capacity of a mobile phone, or
that the network negotiation rate in PDP
activation acceptance messages is less
than the minimum guaranteed rate.
4.1.3 Call Drop Analysis Observation Point
Table 8 CS/PS call drop observation point
Observation
Point Condition
Possible
Cause Analysis Idea
CS/PS call
drop
High CS/PS call
drop rate OM intervention
Call drop caused by operation and
maintenance. For example, the execution
of TRG RABRel on LMT causes users to
be released.
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Observation
Point Condition
Possible
Cause Analysis Idea
RAB
preemption
High-priority users preempt low-priority
users when admission is rejected. This
causes a link to be released. This kind of
call drop occurs in the case of load and
insufficient resource. Determine whether
expansion is necessary according to the
number of occurrences.
UTRAN
Within a cell, UTRAN leads to abnormal
link release. This case generally
corresponds to processing abnormality. We
need to make a further analysis by means
of CDL.
Uplink/downlink
RLC reset
Uplink or downlink signaling RB reaches
the maximum retransmission times and
resets. This causes a link to be released.
This case is mainly caused by poor
coverage quality (including missing
configuration of adjacent cells and small
handover area).
Uplink
synchronization
failure
RNC receives RL Failure reported by
NodeB, which causes a link to be
abnormally released. In this case, poor
coverage quality (including missing
configuration of adjacent cells and small
handover area) makes UE abnormally shut
down the transmitter, or uplink
demodulation out-of-sync.
Downlink
synchronization
failure
Receive the Cell Update message reported
by a mobile phone. The cause is downlink
RL Failure, which makes a link abnormally
released. In this case, poor coverage
quality (including missing configuration of
adjacent cells and small handover area)
makes UE abnormally shut down the
transmitter, or uplink demodulation
out-of-sync.
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Observation
Point Condition
Possible
Cause Analysis Idea
The UU
interface makes
no response.
RNC delivers a message and waits for the
response from a mobile phone, but timeout
occurs. For example, waiting for RB
reconfiguration completion message times
out and waiting for active set update
completion times out. This case is
generally caused by poor coverage.
Other RF
causes RF cause; due to poor coverage quality
Abnormal AAL2
link
RNC finds that the AAL2 Path of the IU CS
interface is abnormal and starts abnormal
release. It is possible that the transmission
equipment of the Iu interface is abnormal.
The known problem is that immediate
normal release during RB establishment is
classified by traffic statistics into abnormal
release.
Abnormal
GTPU
RNC finds that the GTPU of the IU PS
interface is abnormal and starts abnormal
release. The cause may be equipment fault
or defect.
Others
Possibly the call drop (but traffic statistics
does not dot) occurring during flow
interaction or cell update, or abnormal call
drop and cell blocking caused by the
transmission fault of the Iub interface, RNC
internal cause, and Bug. There may be call
drop for abnormal causes. We need to
make an analysis based on RNC logs. The
call drop caused by violent change (corner
effect or driving out from the shadow area
of a building) of uplink signal is known to be
classified into this cause.
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4.1.4 Soft Handover Analysis Observation Point
Table 9 Soft handover analysis observation point
Observation
Point Condition
Possible
Cause Analysis Idea
Soft
handover
rate
Soft handover
rate based on
cell resource
allocation and
soft handover
rate based on
IUB transmission
resource
allocation.
Possible causes of too high (>= 40%) a
soft handover rate:
1) Handover parameter setting makes
addition easy, but deletion difficult.
2) In the early days of network
construction, there are few base
stations and insufficient coverage.
Therefore, capacity gives way to
quality.
3) The CN side of some partners does
not deliver Iu release. After a user’s
dial-up access is disconnected, there
is only user plane release instead of
signaling plane release. Users have
soft handover even after a network is
disconnected.
Configuration
not supported
UE considers that the content of the active
set update of RNC adding/deleting a link is
not supported. Generally, this scenario will
not appear in commercial use.
Synchronization
reconfiguration
not supported
UE gives the feedback that the softer/soft
handover process of RNC adding/deleting
a link is incompatible with other concurrent
processes. RNC has guaranteed serial
flow processing. Soft handover execution
failure is mainly caused by the problematic
processing of some mobile phones.
Soft
handover
execution
failure
Number of
soft/softer
handover failures
(>=5) and
soft/softer
handover failure
rate (>=10%)
Illegal
configuration
UE considers that the content of the active
set update of RNC adding/deleting a link is
illegal. Generally, this scenario will not
appear in commercial use..
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Observation
Point Condition
Possible
Cause Analysis Idea
No response
from UE
RNC does not receive the active set
update command response for
adding/deleting a link. This is the main
cause of softer/soft handover failure. This
happens in the region with poor coverage
or a small handover area. It needs RF
optimization.
4.1.5 CS/PS Intersystem Handover Analysis Observation Point
Table 10 Intersystem handover observation point
Observation
Point Condition Possible Cause Analysis Idea
Hard
handover
preparation
failure
Preparation
failures (>=5) of
hard handover
into this cell and
preparation
failure rate
(>=10%) of hard
handover into
this cell
Radio link establishment failure occurs
during RL establishment. For details, see
the RL establishment process analysis of
the IUB interface.
For other causes, we need to make a
further analysis based on RNC logs.
A target cell has
no wireless
network
resource
available.
A target cell has no resource available, or
there is some RNC parameter
configuration error. We need to make an
analysis based on RNC logs.
Transition
timeout of target
system
The problem often lies in CN parameter
configuration or a related link connection.
We need to make an analysis based on
RNC logs.
Preparation
failure of
transition out
of cell
accompanied
by hard
handover
Preparation
failures (>=5) of
transition out of
cell accompanied
by hard handover
and preparation
failure rate
(>=10%) of
transition out of
cell accompanied
by hard handover Transition failure
in the target
CN/RNC or
system
It generally corresponds to core network
configuration error.
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Observation
Point Condition Possible Cause Analysis Idea
Transition in the
target CN/RNC
or system not
supported
Generally, RNC does not support some
hard handover parameters. We need to
make an analysis based on RNC logs.
Transition
objective not
allowed
Often an MSC parameter configuration
error. We need to check the parameter
configuration of a core network.
OM intervention Failure caused by operation and
maintenance
No available
resource
Often an MSC parameter is configured
incorrectly, or a target RNC has no
resource available.
Undefined Failure causes are not defined in traffic
statistics.
Others We need to make an analysis based on
RNC logs.
Waiting for
transition
command
timeout
A core network does not return a
corresponding command of handover
preparation request. In this case, there is
some problem with the parameter
configuration or related link connection of
a core network. We need to analyze the
cause according to the signaling trace of
the core network and BSS.
Preparation
failure of
RNC-level
foreign
outgoing
handover
Preparation
failures (>=5) of
RNC-level
CS/PS domain
intersystem
outgoing
handover,
preparation
failure rate
(>=10%)of CS
domain
intersystem
outgoing
handover Transition
cancelled
Upon requesting handover preparation,
RNC receives the release command from
a core network. Two cases: intersystem
handover request occurs during signaling
process like location update. The location
update flow has been finished before one
flow is finished. The core network starts
release; the user who sets up a call goes
onhook during handover preparation, and
the core network starts release. No
handover is finished in either case, but
either is normal flow nesting.
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Observation
Point Condition Possible Cause Analysis Idea
Transition
timeout
It generally corresponds to core network
configuration error. We need to analyze
the cause according to the signaling
tracing of a core network and a BSS.
Transition failure
in the target
CN/RNC or
system
The problem often lies in the parameter
configuration or related link connection of
a core network. We need to analyze the
cause according to the signaling tracing of
a core network and a BSS.
Unknown target
RNC
The problem often lies in an MSC
parameter configuration error. That is, the
LAC of the target cell fails to be
configured. We need to check the
parameter configuration of a core network.
This case is often seen after the
adjustment of 2 G network.
No available
resource
The problem often lies in an MSC
parameter configuration error, or BSC has
no resource available. We need to analyze
the cause according to the signaling
tracing of a core network and a BSS.
Others
We need to analyze the cause according
to the signaling tracing of a core network
and a BSS.
Transition
timeout
The problem often lies in the parameter
configuration or related link connection of
a core network. We need to analyze the
cause according to the signaling tracing of
a core network and a BSS.
Preparation
failure of
Cell-level
foreign
outgoing
handover
Preparation
failures (>=5) of
CELL-level CS
domain
intersystem
outgoing
handover and
preparation
failure rate
(>=10%) of CS
Transition failure
in the target
CN/RNC or
system
It generally corresponds to core network
configuration error or BSS not supporting.
We need to analyze the cause according
to the signaling tracing of a core network
and a BSS.
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Observation
Point Condition Possible Cause Analysis Idea
Transition in the
target CN/RNC
or system not
supported
In this case, a BSC does not support some
parameters of intersystem handover
requests. We need to analyze the cause
according to the signaling tracing of a core
network and a BSS.
domain
intersystem
outgoing
handover.
Others
We need to analyze the cause according
to the signaling tracing of a core network
and a BSS.
Configuration
not supported
UE considers that the command for hard
handover out of a cell is not supported.
The problem generally lies in the
compatibility of a mobile phone.
Physical channel
failure
Possibly poor coverage or severe
interference
Synchronization
reconfiguration
not supported
UE gives the feedback that hard handover
process is incompatible with other
concurrent processes. The problem may
lie in the compatibility of a mobile phone
itself.
Cell Updating
Procedure
Cell update happens during hard
handover out of a cell. This flow nesting
leads to the failure of hard handover out of
a cell.
Illegal
configuration
UE considers that the command for hard
handover out of a cell is illegal. The
problem generally lies in the compatibility
of a mobile phone.
Outgoing
hard
handover
failures within
NODE B,
between
different
NodeBs
within RNC,
and between
RNCs
Failures (>=5) of
hard handover
out of a cell,
failure rate
(>=10%) of hard
handover out of a
cell
Others We need to make a further analysis based
on RNC logs.
Failure of
transition out
of a cell
accompanied
by hard
Execution
failures (>=5) of
transition out of a
cell accompanied
by hard
Configuration
not supported
UE considers that the command for
transition out of a cell accompanied by
hard handover is not supported. The
problem generally lies in the compatibility
of a mobile phone.
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Observation
Point Condition Possible Cause Analysis Idea
Physical channel
failure
Possibly poor coverage or severe
interference
Synchronization
reconfiguration
incompatible
UE gives the feedback that the hard
handover process of RNC adding a link is
incompatible with other concurrent
processes. The problem may lie in the
compatibility of a mobile phone itself.
Illegal
configuration
UE considers that the command for
transition out of a cell accompanied by
hard handover is illegal. This case seldom
occurs.
Configuration
not finished
handover handover,
execution failure
rate (>=10%) of
transition out of a
cell accompanied
by hard handover
Others We need to make a further analysis based
on RNC logs.
Configuration
not supported
The handover command terminal in a
network does not provide support. The
problem generally lies in the compatibility
of a mobile phone.
CS/PS
foreign
handover
failure
CS/PS domain
intersystem
handover failures
(>=5), CS/PS
domain
intersystem
handover failure
rate (>=10%)
Physical channel
failure
1) Poor 2 G signal or severe interference
leads to UE access failure.
2) The channel parameters, including
the encryption mode sent from
network to UE, are inconsistent with
those of a BSC. We need to compare
and confirm the parameters of a
terminal and those of a BSC. Physical
channel failure generally occurs in a
network with partners’ equipment as
the CN. We need to check the
encryption algorithm configuration of
an MSC and an SGSN.
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Observation
Point Condition Possible Cause Analysis Idea
Others
We need to make a further analysis
according to RNC logs, together with the
signaling tracing of a core network and a
BSS. Improper service capability
configuration of 2 G cell makes high-rate
service unable to start a pressing mould,
which leads to system PS handover
failure.
4.1.6 Traffic Analysis Observation Point
Table 11 Traffic analysis observation point
Observation
Point Condition Analysis Idea
Uplink CE
Lay an emphasis upon
the analysis of “average
uplink CE resource
occupied” and “the
maximum uplink CE
resource occupied”.
Observe whether “the maximum uplink CE
resource occupied” approaches 128. If it does, an
early warning needs to be given to expansion.
Normally, when the “average uplink CE resource
occupied” is less than 60 CE Erlang,
whole-network busiest-hour cell traffic is very
small.
Downlink CE
Lay an emphasis upon
the analysis of “average
downlink CE resource
occupied” and “the
maximum downlink CE
resource occupied”
Observe whether “the maximum downlink CE
resource occupied” approaches 128. If it does, an
early warning needs to be given to expansion.
Normally, when the “average downlink CE
resource occupied” is less than 60 CE Erlang,
whole-network busiest-hour cell traffic is very
small.
Average transmit
power of cell
List the average TCP,
the maximum TCP and
the minimum TCP of a
cell.
If the average transmit power of a cell is large and
there is small traffic, it indicates that there is poor
downlink coverage.
Maximum
transmit power of
cell
List the average TCP,
the maximum TCP and
the minimum TCP of a
cell.
If the maximum transmit power of a cell is large
and there is small traffic, it indicates that power
peak shock may lead to power congestion.
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Observation
Point Condition Analysis Idea
Minimum
transmit power of
cell
Observe whether the
minimum transmit power
of a cell is abnormal.
If the minimum transmit power of a cell is
abnormal, the transmit channel may become
faulty.
Average RTWP
List the average RTWP,
the maximum RTWP,
and the minimum RTWP
of a cell.
If the average RTWP of a cell is higher than -95
dBm, there may be downlink interference.
Maximum RTWP Observe whether there
are many peaks.
Among various items, RTWP peaks, for example,
-70 dBm, often appear. This may be caused by the
power of access process or handover process.
Minimum RTWP
Observe whether the
minimum RTWP is less
than -105.5 dBm.
If the minimum RTWP is lower than -108 dBm, a
channel fails to be corrected, or a base station
encounters power-down.
Effective
utilization of
codes
Observe whether the
code utilization is
abnormal.
If the effective utilization of codes is not high (<=
30%), but code congestion leads to access failure,
it is possible that the code distribution algorithm is
abnormal.
Uplink
throughput of cell
Observe the uplink
throughput of a cell.
Observe whether the uplink throughput of a cell is
great. If it amounts to 75% of the transmission
capability of a base station, transmission
expansion needs to be considered.
Downlink
throughput of cell
Observe the downlink
throughput of a cell.
Observe whether the downlink throughput of a cell
is great. If it amounts to 75% of the transmission
capability of a base station, transmission
expansion needs to be considered..
Cell status
monitoring
List the cell unavailability
duration and its
proportion.
This is generally caused by transmission
interruption or intermittent transmission failure.
Some offices are greatly influenced by weather
due to the use of microwave transmission.
Thunder storm always leads to intermittent
transmission failure.
Missing
configuration of
adjacent cell
List the number of cell
1A events.
If 1A events often happen within many
consecutive days, there may be missing
configuration of adjacent cells.
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Observation
Point Condition Analysis Idea
Excess
configuration of
adjacent cells
Pilot Pollution: List the number of cell
1C events.
If 1C events often happen within many
consecutive days, there may be pilot pollution.
4.1.7 Key Interface Flow Analysis Observation Point
Table 12 Key interface flow analysis observation point
Observation
Point Condition
Possible
Cause Analysis Idea
Radio
network layer
The problem may lie in the compatibility
of a mobile phone. A mobile phone
terminal may detect the SQN error of in
an AUTN message, which leads to
failure. Cause value: Synch failure!
Respective encryption modes of CS
domain and PS domain may also lead to
a security mode failure.
Transmission
layer
Correspond to transmission link
abnormality.
Network
optimization
Security mode
flow failure
IU security mode
failures, IU
security mode
failure rate
Undefined
OM
intervention
RL failure of IUR interface caused by
operation and maintenance
Hardware
failure
This generally corresponds to equipment
abnormality. We should first query
related equipment alarm.
RL
establishment
failure of the IUR
interface
RL
synchronization
configuration
failure of the IUR
interface
RL addition
failure of the IUR
List the number of
RL establishment
failures (>= 5) of
the Iur interface of
the SRNC, RL
establishment
failure rate (>=
10%) of the Iur
interface of the
SRNC, and main
failure causes.
RNC resource
unavailable
This is caused by insufficient RNC
internal resource. You need to query the
quantity of related users to judge
whether there is any equipment
abnormality.
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Observation
Point Condition
Possible
Cause Analysis Idea
Configuration
not supported
UE considers that the RL configuration
content of RNC establishment is not
supported. The problem lies in the
compatibility of a mobile phone.
Others Abnormal causes. We need to make an
analysis based on RNC logs.
interface
No response
This generally corresponds to equipment
abnormality. We need to query whether
there is any power-down.
Configuration
not supported
The problem lies in the compatibility of a
mobile phone itself in some unknown
scenarios.
No available
resource
Insufficient RNC internal resource or
abnormal RNC equipment. You need to
query cell CE resource from relevant
parameters to judge whether there is any
equipment abnormality. Equipment is
known to encounter repeated power
failure and air-conditioner fault due to
thunder storm. As a result, high
temperature leads to abnormality of
various kinds. Besides, the NLPA board
encounters shutdown.
Equipment
fault
This generally corresponds to equipment
abnormality. We should first query
related equipment alarm.
OM
intervention
RL establishment failure caused by
operation and maintenance (for example,
cell blocking)
NodeB makes
no response
The problem may lie in cell unavailability
or equipment fault. You need to query
the cell unavailability duration from
relevant parameters to judge whether
there is any equipment fault.
RL
establishment
failure of the
IUB interface RL
reconfiguration
failure of the IUB
interface
RL addition
failure of the IUB
interface
List the number of
RL establishment
failures of the IUB
interface, RL
establishment
failure rate of the
Iub interface, and
main failure
causes.
Others RL establishment failure caused by
abnormal factors. We need to make an
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Observation
Point Condition
Possible
Cause Analysis Idea
analysis based on RNC logs
RL reconfiguration failure caused by
abnormal factors. We need to make an
analysis based on RNC logs. The known
causes are that transmission congestion
(Received Iub AAL2 type1 setup
response message from AL but result is
5 not success!) and improper T314/T315
parameter setting make there not be any
opportunity of RL reconfiguration. RL
addition failure caused by abnormal
factors. We need to make an analysis
based on RNC logs. It is known that RL
addition failure caused by restricted IUB
transmission bandwidth will be classified
into this cause value.
Configuration
not supported
The problem lies in the compatibility of a
mobile phone itself in some unknown
scenarios. For example, when a Huawei
mobile phone drops network abnormally,
it may not release any RB. When PS RB
is reestablished next time, this case may
occur. This case also happens to SE
V800 mobile phone. Or when some UEs
implement VP and high-speed (greater
than or equal to 64K) PS service, failure
may also due to unsupported capability.
Physical
channel
failure
This generally occurs when FACH
migrates to DCH and establishes RB.
The downlink physical layer of a terminal
is not synchronized, which leads to RB
establishment failure. This is mainly
caused by poor coverage.
Cell update
The Cell Update flow occurs during RB
establishment. This nested flow leads to
RB establishment failure.
RB
establishment
failure
RB
reconfiguration
failure
RB deletion
failure
RB establishment
failure generally
corresponds to
poor air interface
coverage or a
mobile phone
compatibility
problem.
Illegal
configuration
UE considers parameter configuration
illegal. Network and terminals have an
inconsistent understanding of parameter
processing. If RB establishment failure
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Observation
Point Condition
Possible
Cause Analysis Idea
occurs in the domain of CS, it is possible
that a user dials a wrong telephone
number and immediately goes onhook.
RB SETUP failure may also occur at this
time. The cause is illegal configuration.
Or when a 3 G terminal as the caller
implements VP service, the called party
resides in a GSM network and does not
support VP service. Thus, after RNC
receives an RAB assignment request, a
core network immediately delivers the
Disconnect command upon Call
Proceeding (the cause is Bearer
capability not authorized). But UE has
just received an RB_SETUP command
at this time and has no time to complete
RB establishment. Upon receiving this
Disconnect command, UE initiates a
response “RB establishment failure” and
RNC returns RAB establishment failure.
No response
from UE
Generally poor coverage makes UE
unable to receive any RB command. In
Hong Kong, the balance mechanism of
IUB once made signaling established on
one E1, but service was established on
another E1. Thus, there has been no
problem with signaling, but RB
establishment may fail. In this case, it is
this cause value that is returned.
RB bearer
distribution of
uplink/downlink
service
Uplink/downlink
RB bearer
distribution of BE
service
Observe whether
the number of
various types of
RB service bearer
and the
proportion are
abnormal. If there
is any
abnormality, an
early warning
needs to be given
PS has a large amount of 128k, 144k,
and 384k RB bearer. This will consume a
large number of resources and there is
poor coverage. We need to verify
whether RB bearer is consistent with
actual demands with first-line personnel.
Observe whether the RB distribution of
BE service is rational. According to the
distribution, DCCC strategy and related
system parameters can be adjusted.
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4.1.8 HSDPA Analysis Observation Point
RNC1.6 version supports the following KPI monitoring: HSDPA service establishment
success rate, HSDPA call drop rate, HSDPA cell throughput, H <-> H
intra-/inter-frequency serving cell update success rate and H <-> R99 intra-frequency
handover success rate. It does not support the following KPI monitoring: HSDPA
average uplink and downlink throughput for a single user, H <-> R99 inter-frequency
handover success rate, H -> GPRS intersystem handover success rate, statistics of
the causes for HSDPA service establishment failure, statistics of the causes for
HSDPA call drop failure, statistics of the causes for H <-> H intra-/inter-frequency
serving cell update failure, statistics of the causes for H <-> R99 intra-/inter-frequency
handover failure, statistics of the causes for H -> GPRS intersystem handover failure.
Therefore, we cannot use traffic statistics for HSDPA all-KPI monitoring and analysis,
but need to use other supplementary means. It is recommended to use driving test
and signaling tracing for routine monitoring of the indexes not supported by RNC1.6
version. Meanwhile, analyze and locate KPI abnormality.
RNC1.7 traffic statistics is being collated and remains to be supplemented.
4.2 Example of Analysis Based on Observation Point
Take RRC establishment problem analysis for example.
1. Overall analysis of RRC establishment
As shown in Figure 10 the task window of the Nastar is embedded with the special
topic analysis of call completion rate——RRC Setup Analysis. Double click to start this
query to get the general information about RNC-level RRC establishment. As shown in
the following figure, RRC establishment success rate reaches 98.84%. Most of RRC
establishment failure is because there is no response to RRC Setup command
delivery (7,373 times). Eighteen failures are because of RRC Setup Reject.
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Figure 11 General information about RRC setup
The main cause of the exemplified RRC establishment failure is that there is no
response to RRC Setup command delivery. It is unbalanced coverage of downlink
FACH and uplink RACH. For an early network, coverage cannot be guaranteed, so
there are a large number of areas with poor coverage quality. These areas with poor
coverage always correspond to intersystem rerouting areas. On the other hand, where
there are many users or equipment problems within a cell, RRC establishment
rejection is also a major cause of RRC establishment failure.
2. Analysis of RRC establishment scenario
One important reason for RRC establishment failure is poor coverage. We may make
a further analysis by using the establishment cause distribution and success rate of
different RRCs establishment. Get results by starting related query and selecting
Scenario Analysis to present a selected RNC in the form of a pie chart and a bar chart.
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Figure 12 Distribution of RRC setup scenario
Figure 13 Comparison of RRC setup scenario success rate
Scenario Analysis makes a comparative analysis of several commonly used scenarios.
The pie chart shows the RRC establishment distribution of a main scenario. The
example in the chart indicates that RRC establishment requests mainly exist in
network registration with REG as the cause. When an LAC area is not well planned or
there is poor coverage (the margin of LAC division is in a prosperous area), there may
be a lot of registration. On the other hand, the cause of RRC establishment during
intersystem reselecting of this mobile phone is registration. A large number of mobile
phones fail to be registered due to poor coverage and will try again and again. Thus,
the cause of RRC establishment is registration in many cases. This indicates that
there is poor network coverage in some areas.
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As shown in Figure 13, the bar chart compares the RRC establishment success rates
of various main scenarios. It can be seen from the examples in the figure that the
called voice service has the highest RRC establishment success rate while the calling
voice has the lowest success rate (which corresponds to a large amount of UENoRsp
analyzed earlier). The RRC establishment success rate of registration is also relatively
low. In Huawei networks, the present resident threshold is Ec/Io greater than -18 dB.
The intersystem reselecting starting threshold is Ec/Io less than -14 dB. A low
registration success rate indicates that some terminals have attempted to register at a
network in the areas without good coverage (Ec/Io is between -14 dB and -18 dB). The
called RRC establishment success rate is as high as 99.3%. If the called party starts
RRC establishment, it indicates that he is covered by a PCH. From another point of
view, this indicates that the RRC establishment success rate of expected network
coverage area may be very high.
3. Analysis of RRC establishment rejection
Another cause of RRC establishment failure is RRC establishment rejection. In the
case of RRC establishment rejection, generally too many users lead to admission
rejection, or cell equipment fault leads to access failure. RRC establishment rejection
always corresponds to some areas instead of a large network area. RRC
establishment rejection is generally analyzed based on problematic areas. In the
query results of RRC Setup Analysis, start related query to make TOPN query of Cell
RRC Analysis. Query results cover two pages, which respectively list 10 cells with the
most VS.RRC.FailConnEstab.Cell and VS.RRC.SuccConnEstab.Rate.Cell. For the 10
cells with the most RRC establishment failures and the cells with the most Rej, start
Cell RRC Reject Analysis of related query to analyze the causes for rejection.
Figure 14 Analyzing the cause of RRC rejection
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According to the results of Cell RRC Reject Analysis, draw a pie chart of cause
distribution for a selected cell. Figure 14 is an exemplified pie chart of cause
distribution of RRC rejection. In this example, two RRC rejections of a cell are
because of Power Congestion. The following shows the commonly seen causes of
rejection:
1) Power Congestion: RRM makes an admission algorithm decision. Downlink
admission decision occurs. Therefore, RRM starts RRC establishment rejection.
This often occurs when heavy network load leads to congestion. Further, we may
start Cell Traffic Load Analysis of related query, pay much attention to the
maximum RTWP and the maximum TCP of this cell and make sure whether there
is uplink congestion or downlink congestion. For congestion, we may check
whether a threshold is properly set and judge whether there is any radio
interference, whether expansion is necessary.
2) CE Congestion: This is mainly because RNC considers CE resource insufficient.
CE congestion always corresponds to many users. These users exceed CE
capacity and we need to expand the capacity of this area. Further, we may start
Cell Traffic Load Analysis of related query, know about the quantity of DCH User
and predict the required CEs according to the traffic model.
3) RL Fail: During RRC establishment, NodeB considers establishment fails. This
may be NodeB fault or insufficient NodeB resource. Further, we may start Cell
Traffic Load Analysis of related query and know about the quantity of DCH users.
Determine whether the problem lies in insufficient resource or equipment fault by
analyzing the board configuration, CE configuration and logs of a corresponding
NodeB.
4) AAL2 Fail: This is mainly the AAL2 Path establishment failure of an Iub interface.
It is generally caused by insufficient transmission resource or transmission
problems. Further, we may start Cell Traffic Load Analysis of related query, know
about the quantity of DCH users and compare it with the AAL2 Path bandwidth of
transmission configuration. Thus, we can determine whether the problem lies in
equipment or insufficient transmission resource.
5) Redir.Inter.Att: Inter-frequency redirection failure starts rejection.
6) Redir.Intrat: Foreign redirection failure starts rejection.
7) Code Congestion: This is mainly because of insufficient resource. Insufficient
code resource may be seen in high traffic scenarios with microcell coverage, and
expansion is necessary. Cell OVSF Code Allocation Analysis of related query
helps analyze the use of channel codes and clarify main services.
8) Other: This is mainly an RNC internal processing problem. Its cause needs to be
confirmed according to R&D logs.
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4.3 Summary
Make a similar analysis of several other special topics according to the
above-mentioned idea of the RRC connection analysis. Keep summarizing
experiences in your analysis. Special topic analysis will help greatly improve basic
skills of performance analysis.
Basic special topic analysis practice contributes to the following aspects:
1) Consolidate signaling flow and deepen an understanding of each UTRAN PI.
Performance analysis has a more definite object in view.
2) Basic special topic analysis enables us to make a preliminary analysis of network
performance and locate simple problem causes.
3) Summarize the relationship between performance KPIs and network problems,
and lay a foundation for the use of other Nastar functions and an in-depth
analysis of network performance.
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5 Closing of Performance Analysis and Quality Early Warning
5.1 Basic Requirements for Analysis Conclusion
Performance early warning analysis is a key step to find problems accurately and
timely. It is also the basis for subsequent problem location and problem solving as well
as the prerequisite to formulating a subsequent scheme. If on-site personnel and a
regional division are unable to locate a problem, it is quite possible that the
Headquarters needs to participate in the location. Even the R&D personnel should be
organized to tackle this problem. To improve efficiency and avoid duplication of labor,
we have put forward the following requirements for an analysis conclusion:
� Do verify related observation points of an early warning problem one by one, and
draw a basic conclusion.
� Do make a definite description of equipment alarm.
� Do have a definite location of analysis range, for example, what cells and what
UEs are problematic and whether there is any problem with transmission.
� Do expound carefully the deduction process of an early warning conclusion.
� Do provide subsequent test methods, suggested solutions, and candidate
schemes.
� Do make a preliminary judgment of the signaling flow that may be involved, for
example, signaling flow abnormality, location of abnormality, or cause
distribution.
� If a problem is estimated to escalate to a higher level, do carry necessary data.
For details, refer to respective problem location guides and provide pertinent
excerpts. For example, there is no need to send back whole-day driving test data
and use it for the analysis of a call drop point. There should be a simple
description of data, such as point of time of problem occurrence and the mapping
between the time and sequence number of different data.
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5.2 Output Analysis Report
If any abnormality problem or quality risk occurs during performance analysis, we
need to work out a report in time. The report should include performance problem
description and suggestions on problem solving.
For the call drop caused by other, if we cannot find out the cause from CHR
information, we need to include the dotting information of CHR in the report and
submit analysis suggestions to the product R&D personnel. The R&D personnel will
analyze the specific cause.
5.3 Summary
According to network performance analysis results, formulate optimization strategies,
implement optimization schemes, and compare the indexes before and after the
optimization to obtain optimization implementation effects. In this way, one
performance analysis is closed. But performance analysis and quality early warning
come full circle. The increase in network registration users, change in traffic model,
and equipment transmission abnormality require that engineers should show
continuous concern for network performance, summarize experiences and use proper
methods to improve the efficiency of performance analysis.
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6 References � UTRAN KPI Analysis Guide-20051010-A-1.0
� UMTS Performance Department—RAN Performance Optimization Idea
� GENEX Nastar WCDMA User Manual (CHN)
� Guide to Analysis of UMTS Network Planning Remote Network Performance
-20060524
� UMTS Radio Performance Department— Commercial Network Index
Optimization_Call Drop Rate Optimization (V1.0)
� Alarm Analysis Guide