W-Handover and Call Drop Guide

W-Handover and Call Drop Problem Optimization Guide For internal use only
Product name Confidentiality level
WCDMA RNP For internal use only
Product version
3.3 Total 201 pages
W-Handover and Call Drop Problem Optimization
Guide
(For internal use only)
Prepared by Jiao Anqiang Date 2006-03-16
Reviewed by Xie Zhibin, Dong Yan, Hu
Wensu, Wan Liang, Yan
Lin, Ai Hua, Xu Zili, and
Hua Yunlong
Date
Reviewed by Wang Chungui Date
Approved by Date
Huawei Technologies Co., Ltd.
All Rights Reserved
2009-10-10 All rights reserved Page 1 of 201

Revision Records
Date Version Description Author
2005-02-01 2.0
Completing V2.0 W-Handover and Call Drop
Problems.
Cai Jianyong,
Zang Liang, and
Jiao Anqiang
2006-03-16 3.0
According to V3.0 guide requirements,
reorganizing and updating V2.0 guide, focusing
more on operability of on-site engineers. All traffic
statistics is from RNC V1.5. The update includes:
Updating flow chart for handover problem
optimization
Moving part of call drop due to handover problem
to handover optimization part
Specifying operation-related part to be more
applicable to on-site engineers
Updating RNC traffic statistics indexes to V1.5
Integrating traffic statistics analysis to NASTAR of
the network performance analysis
Optimizing some cases, adding new cases, and
removing outdated cases and terms
Moving content about handover and call drop to the
appendix, and keeping operations related to them in
the body
Adding explanations to SRB&TRB and RL
FAILURE.
Jiao Anqiang
2006-04-30
3.1
Adding HSDPA-related description HSDPA
handover DT/CQT flow, definitions of traffic
statistics in HSDPA handover, HSDPA handover
problems. Adding algorithms and flows of HSDPA
handover.
Zhang Hao and
Li Zhen

Date Version Description Author
2006-10-30
3.11
Adding V17-related handover description as below:
Changes in signaling flow for H2D HHO
Changes in triggering events of H2D and D2H
D2H handover in HSDPA based on traffic and
timers
Updating description of HSDPA serving cell and
traffic statistics of HSDPA-DCH handover
Adding call drop indexes in HSDPA DT/statistics
Wang Dekai
2007-08-09 3.2 Adding HSUPA-related description. Zhang Hao
2008-12-15
3.3
Adding MBMS-related description.
Yearly review
WangDekai /
HuWensu

Contents
1 Introduction .............................................................................................................................14
2 Handover and Call Drop Performance Indexes......................................................................16
2.1 Handover Performance Indexes ......................................................................................16
2.2 Call Drop Performance Indexes .......................................................................................19
3 Handover Index Optimization .................................................................................................20
3.1 DT/CQT Index Optimization Flow.....................................................................................20
3.1.1 SHO DT Index Optimization Flow...........................................................................20
3.1.2 HHO CQT Flow .....................................................................................................24
3.1.3 Inter-RAT Handover CQT Flow..............................................................................27
3.1.4 DT/CQT Flow for HSDPA Handover ......................................................................29
3.1.5 DT/CQT Flow for HSUPA Handover ......................................................................32
3.1.6 SHO Ratio Optimization.........................................................................................32
3.1.7 MBMS Mobility Optimization ..................................................................................32
3.2 Traffic Statistics Analysis Flow.........................................................................................34
3.2.1 Analysis Flow for SHO Traffic Statistics .................................................................35
3.2.2 Analysis Flow of HHO Traffic statistics...................................................................36
3.2.3 Traffic Statistics Analysis Flow for Inter-RAT Handover..........................................37
3.2.4 Traffic Statistics Analysis for HSDPA Handover .....................................................40
3.2.5 Traffic Statistics Analysis for HSUPA Handover .....................................................41
3.3 SHO Cost Optimization....................................................................................................43
4 CDR Index Optimization..........................................................................................................44
4.1 Definition of Call Drop and Traffic Statistics Indexes ........................................................44
4.1.1 Definition of DT Call Drop ......................................................................................44
4.1.2 Descriptions of Traffic Statistics Indexes ................................................................44
4.2 DT/CQT Optimization Flow..............................................................................................45
4.2.1 Call Drop Cause Analysis ......................................................................................46
4.2.2 Frequently-adjusted Non-handover Algorithm Parameters......................................48
4.2.3 Judgment Tree for Call Drop Causes .....................................................................49
4.3 Traffic Statistics Analysis Flow.........................................................................................50
4.3.1 Analyzing RNC CDR..............................................................................................51
4.3.2 Analyzing Causes to Call Drop...............................................................................51
4.3.3 Check Cells ...........................................................................................................52
4.3.4 Further DT for Relocating Problems.......................................................................52
4.4 Optimization Flow for Tracing Data..................................................................................52
4.4.1 Obtaining Single Subscriber Tracing Message .......................................................53
4.4.2 Obtaining Information about Call Drop Point ..........................................................53
4.4.3 Analyzing Call Drop due to SRB Reset ..................................................................54
4.4.4 Analyzing Call Drop due to TRB Reset...................................................................54
4.4.5 Analyzing Abnormal Call Drop ...............................................................................54
4.4.6 Performing CQT to Recheck Problems ..................................................................55
2008-12-22 All rights reserved Page4 , Total201

4.5 Optimization Process for MBMS Call Drop.......................................................................55
5 FAQs Analysis.........................................................................................................................56
5.1 SHO Problems ................................................................................................................56
5.1.1 Over High SHO Rate due to Improper SHO Relative Threshold .............................56
5.1.2 Delayed Handover due to Over Great Intra-frequency Filter Coefficient..................57
5.1.3 Missing Neighbor Cell............................................................................................58
5.1.4 Redundant Neighbor Cells.....................................................................................62
5.1.5 Pilot Pollution.........................................................................................................65
5.1.6 Turning Corner Effect ............................................................................................71
5.1.7 Needlepoint Effect .................................................................................................74
5.1.8 Quick Change of Best server Signal.......................................................................75
5.2 HHO Problems ................................................................................................................77
5.2.1 Intra-frequency Ping-pong HHO due to Improperly Configured 1D Event Hysteresis77
5.2.2 Delayed Origination of Inter-frequency Measurement due to Improper Inter-frequency
Measurement Quantity ..................................................................................................78
5.3 Inter-RAT Handover Problems.........................................................................................80
5.3.1 Ping-pong Reselection...........................................................................................80
5.3.2 PS Inter-RAT Ping-pong Handoff ...........................................................................81
5.3.3 Failure in handoff from 3G to the 2G network .........................................................82
5.3.4 Inter-RAT Handover Call Drop ...............................................................................84
5.4 Call Drop Problems .........................................................................................................91
5.4.1 OverWeak Coverage ............................................................................................91
5.4.2 Uplink Interference ................................................................................................92
5.4.3 Abnormal Equipment .............................................................................................95
5.5 HSDPA-related Problems ................................................................................................97
5.5.1 HSDPA Handover Problems..................................................................................97
5.5.2 HSDPA Call Drop ..................................................................................................98
5.6 HSUPA Problems..........................................................................................................100
6 Summary................................................................................................................................101
7 Appendix................................................................................................................................102
7.1 SRB&TRB Reset ...........................................................................................................102
7.1.1 RAB ....................................................................................................................102
7.1.2 SRB ....................................................................................................................103
7.2 RL FAILURE .................................................................................................................104
7.3 SHO Flow......................................................................................................................109
7.3.1 Analyzing Signaling Flow for Adding Radio Link...................................................109
7.3.2 Analyzing Signaling Flow for Deleting Radio Link.................................................112
7.3.3 Analyzing Signaling Flow for Adding and Deleting Radio Link ..............................113
7.3.4 SHO Algorithm ....................................................................................................116
7.4 Ordinary HHO Flow.......................................................................................................123
7.4.1 Ordinary HHO (lur Interface and CELL_DCH State) .............................................123
7.4.2 Inter-CN HHO Flow..............................................................................................125
7.5 HHO Algorithm..............................................................................................................128
7.5.1 Intra-frequency HHO Algorithm............................................................................128
7.5.2 Inter-frequency HHO Algorithm............................................................................128
7.6 Concept and Classification of HSDPA Handover............................................................130
7.6.1 Concept of HSDPA Handover..............................................................................130
7.6.2 Classification of HSDPA Handover ......................................................................130
7.6.3 Signaling Flow and Message Analysis of HSDPA Handover.................................131
7.6.4 HS-PDSCH Serving Cell Update due to DPCH SHO............................................132
7.6.5 HS-PDSCH Serving Cell Update due to DPCH HHO............................................139
7.6.6 DPCH Intra-frequency HHO with HS-DSCH Serving Cell Update.........................140
7.6.7 DPCH Inter-frequency HHO with HS-DSCH Serving Cell Update.........................141

7.6.8 Handover Between HSDPA and R99 ...................................................................143
7.6.9 Handover between HSDPA and GPRS................................................................152
7.6.10 Direct Retry of HSDPA.......................................................................................152
7.6.11 Switch of Channel Type .....................................................................................154
7.7 Concept and Classification of HSUPA Handover............................................................157
7.7.1 Basic Concepts....................................................................................................157
7.7.2 Classification of HSUPA Handover ......................................................................157
7.7.3 Signaling Flow and Message Analysis of HSUPA Handover.................................158
7.7.4 SHO from a HSUPA Cell to a Non-HSUPA Cell ...................................................164
7.7.5 SHO from a Non-HSUPA Cell to a HSUPA Cell ...................................................169
7.7.6 Handover Between a HSUPA Cell and a GSM/GPRS Cell ...................................172
7.7.7 Direct Retry of HSUPA.........................................................................................172
7.7.8 Switch between Channel Types...........................................................................174
7.8 Handover from WCDMA to GSM...................................................................................175
7.9 Handover from GSM toWCDMA ...................................................................................179
7.10 Handover from WCDMA to GPRS................................................................................182
7.11 Handover from GRPS toWCDMA................................................................................186
7.12 Parameters of Handover from 3G to 2G Network .........................................................189
7.13 Data Configuration for Supporting Bi-directional Roaming and Handover Between WCDMA and
GSM/GPRS........................................................................................................................192

Figures
Figure 3-1 SHO DT data analysis flow................................................................................................ 21
Figure 3-2 Optimization flow for HHO CQT......................................................................................... 26
Figure 3-3 Inter-RAT handover CQT flow............................................................................................ 28
Figure 3-4 DT/CQT flow for HSDPA handover .................................................................................... 31
Figure 3-5 Movement of the MBMS UE between PTM cells................................................................ 32
Figure 3-6 Analysis flow for handover traffic statistics data.................................................................. 35
Figure 3-7 Voce inter-RAT outgoing handover flow ............................................................................. 38
Figure 4-1 Flow chart for analyzing call drop ...................................................................................... 46
Figure 4-2 Judgment tree for call drop causes.................................................................................... 49
Figure 4-3 Flow for analyzing call tracing............................................................................................ 53
Figure 5-1 SHO relative threshold ...................................................................................................... 57
Figure 5-2 Signaling flow recorded by UE before call drop.................................................................. 58
Figure 5-3 Scrambles recorded by UE active set and scanner before call drop ................................... 59
Figure 5-4 Scrambles in UE active set before call drop....................................................................... 60
Figure 5-5 UE intra-frequency measurement control point before call drop ......................................... 61
Figure 5-6 Analyzing signaling of UE intra-frequency measurement control before call drop................ 61
Figure 5-7 Confirming missing neighbor cell without information from scanner.................................... 62
Figure 5-8 Location relationship of 2G redundant neighbor cells......................................................... 64
Figure 5-9 Pilot pollution near Yuxing Rd............................................................................................ 65
Figure 5-10 Best ServiceCell near Yuxing Rd. .................................................................................... 65
Figure 5-11 The 2nd best ServiceCell near Yuxing Rd. ....................................................................... 66
Figure 5-12 The 3rd best ServiceCell near Yuxing Rd......................................................................... 66
Figure 5-13 The 4th best ServiceCell near Yuxing Rd......................................................................... 67
Figure 5-14 Composition of pilot pollution near Yuxing Rd. ................................................................. 67
Figure 5-15 RSSI near Yuxing Rd....................................................................................................... 68
Figure 5-16 RSCP of Best ServiceCell near Yuxing Rd....................................................................... 68
Figure 5-17 RSCP of SC270 cell near Yuxing Rd................................................................................ 69

Figure 5-18 Pilot pollution near Yuxing Rd. after optimization.............................................................. 70
Figure 5-19 Best ServiceCell near Yuxing Rd. after optimization......................................................... 70
Figure 5-20 RSCP of best ServiceCell near Yuxing Rd. after optimization........................................... 71
Figure 5-21 RSCP of SC270 cell near Yuxing Rd. after optimization ................................................... 71
Figure 5-22 Turning corner effect-signals attenuation ......................................................................... 72
Figure 5-23 Turning corner effect-signal attenuation recorded by the UE ............................................ 72
Figure 5-24 Turning corner effect-traced signaling recorded by the RNC............................................. 73
Figure 5-25 Needle point-signal variance............................................................................................ 74
Figure 5-26 Call drop distribution of PS384K intra-frequency hard handover....................................... 75
Figure 5-27 Signal distribution of cell152 vs. cell88 (signal fluctuation in handover areas)................... 76
Figure 5-28 Reporting 1D event ......................................................................................................... 77
Figure 5-29 Increasing hysteresis to reduce frequently reporting of 1D event...................................... 78
Figure 5-30 Attenuation relationship of RSCP and Ec/No.................................................................... 79
Figure 5-31 Indoor 3G RSCP distribution............................................................................................ 83
Figure 5-32 Analyzing weak signals.................................................................................................... 91
Figure 5-33 Uplink interference according to RNC signaling ............................................................... 93
Figure 5-34 Uplink interference according to UE signaling .................................................................. 93
Figure 5-35 Uplink interference information recorded by UE ............................................................... 94
Figure 5-36 RTWP variation of the cell 89767..................................................................................... 94
Figure 5-37 RTWP variation of the cell 89768..................................................................................... 95
Figure 5-38 Pilot information recorded by scanner.............................................................................. 97
Figure 7-1 UMTS QoS structure....................................................................................................... 102
Figure 7-2 SRB and TRB at user panel............................................................................................. 103
Figure 7-3 Signaling flow for adding radio link....................................................................................110
Figure 7-4 Signaling flow for deleting radio link..................................................................................112
Figure 7-5 SHO signaling flow for adding and deleting radio link........................................................114
Figure 7-6 Measurement model.........................................................................................................116
Figure 7-7 Example 1A event and trigger delay .................................................................................118
Figure 7-8 Periodic report triggered by 1A event................................................................................119
Figure 7-9 Example of 1C event ....................................................................................................... 120
Figure 7-10 Example 1D event......................................................................................................... 121
Figure 7-11 Restriction from hysteresis to measurement report......................................................... 121
Figure 7-12 Example of 1E event ..................................................................................................... 122
Figure 7-13 Example of 1F event ..................................................................................................... 122

Figure 7-14 Ordinary HHO flow (lur interface and CELL_DCH state) ................................................ 124
Figure 7-15 Ordinary inter-CN HHO flow .......................................................................................... 126
Figure 7-16 Intra-NodeB synchronization serving cell update............................................................ 133
Figure 7-17 Inter-NodeB synchronization serving cell update............................................................ 135
Figure 7-18 Inter-NodeB HS-DSCH cell update after radio link is added ........................................... 137
Figure 7-19 Inter-NodeB HS-DSCH cell update during HHO (single step method) ............................ 139
Figure 7-20 DPCH intra-frequency HHO with HS-DSCH serving cell update..................................... 141
Figure 7-21 DPCH inter-frequency HHO with HS-DSCH serving cell update..................................... 142
Figure 7-22 handover from HSDPA to R99 ....................................................................................... 143
Figure 7-23 Intra-frequency handover from R99 to R5...................................................................... 143
Figure 7-24 DPCH SHO with handover from HSDPA to R99 (inter-NodeB)....................................... 145
Figure 7-25 DPCH SHO with handover from R99 to HSDPA............................................................. 146
Figure 7-26 Inter-NodeB SHO with handover from HSDPA to R99 (V17) .......................................... 147
Figure 7-27 Intra-frequency HHO with handover from R5 to R99 ...................................................... 148
Figure 7-28 Intra-frequency HHO with handover form R99 to R5 ...................................................... 148
Figure 7-29 Intra-frequency HHO with handover from R5 to R99 (V17)............................................. 149
Figure 7-30 Inter-frequency HHO from HS-PDSCH to DCH.............................................................. 150
Figure 7-31 Inter-frequency HHO from DCH to HS-PDSCH.............................................................. 151
Figure 7-32 Handover between HSDPA and GPRS.......................................................................... 152
Figure 7-33 Flow for direct retry during setup of a service................................................................. 153
Figure 7-34 Direct retry triggered by traffic........................................................................................ 153
Figure 7-35 Switch of channel type................................................................................................... 155
Figure 7-36 Intra-frequency SHO between two HSUPA cells............................................................. 159
Figure 7-37 Signaling for HSUPA cell update triggered by a 1D event............................................... 159
Figure 7-38 Signaling for HSUPA cell update triggered by a 1D event (reported by the monitor set).. 160
Figure 7-39 Intra-frequency HHO between two HSUPA cells ............................................................ 160
Figure 7-40 Signaling for intra-frequency HHO between two HSUPA cells ........................................ 161
Figure 7-41 Inter-frequency HHO between two HSUPA cells ............................................................ 161
Figure 7-42 Signaling for inter-frequency HHO between two HSUPA cells ........................................ 162
Figure 7-43 Inter-RNC HSUPA handover.......................................................................................... 163
Figure 7-44 SHO from a HSUPA cell to a non-HSUPA cell ................................................................ 165
Figure 7-45 Addition of an R99 cell when the service is on the E-DCH.............................................. 166
Figure 7-46 Intra-frequency HHO from a HSUPA cell to a non-HSUPA cell ....................................... 167
Figure 7-47 Signaling for intra-frequency HHO from a HSUPA cell to a non-HSUPA cell ................... 167

Figure 7-48 Inter-frequency HHO from a HSUPA cell to a non-HSUPA cell ....................................... 168
Figure 7-49 Signaling for inter-frequency HHO from a HSUPA cell to a non-HSUPA cell ................... 169
Figure 7-50 SHO from a non-HSUPA cell to a HSUPA cell ................................................................ 170
Figure 7-51 SHO from a non-HSUPA cell to a HSUPA cell (triggered by a 1B event)......................... 170
Figure 7-52 Intra-frequency HHO from a non-HSUPA cell to a HSUPA cell ....................................... 171
Figure 7-53 Signaling for intra-frequency HHO from a non-HSUPA cell to a HSUPA cell ................... 171
Figure 7-54 Inter-frequency HHO from a non-HSUPA cell to a HSUPA cell ....................................... 172
Figure 7-55 Direct retry from an R99 cell to a HSUPA cell................................................................. 173
Figure 7-56 Direct retry from a HSUPA cell to an R99 cell................................................................. 173
Figure 7-57 Direct retry from a HSUPA cell to another HSUPA cell.................................................... 174
Figure 7-58 Switch between HSUPA channel types .......................................................................... 174
Figure 7-59 Signaling flow for handover from WCDMA to GSM......................................................... 176
Figure 7-60 Tracing signaling of handover from WCDMA to GSM..................................................... 176
Figure 7-61 Signaling flow for handover from GSM to WCDMA ........................................................ 179
Figure 7-62 Tracing signaling of handover from GSM to WCDMA..................................................... 180
Figure 7-63 Flow of handover from WCDMA to GPRS (1)................................................................. 183
Figure 7-64 Flow of handover from WCDMA to GPRS (2)................................................................. 183
Figure 7-65 Tracing signaling of handover from WCDMA to GPRS................................................... 184
Figure 7-66 Signaling flow for handover from GPRS to WCDMA (1) ................................................. 186
Figure 7-67 Signaling flow for handover from GPRS to WCDMA (2) ................................................. 187
Figure 7-68 Data configuration in the location area cell table ............................................................ 193
Figure 7-69 Data configuration of neighbor cell configuration table ................................................... 194
Figure 7-70 Configuration table for external 3G cells ........................................................................ 196
Figure 7-71 Configuration table for GSM inter-RAT neighbor cells .................................................... 197
Figure 7-72 Configuration table for 2G reselection parameters ......................................................... 198
Figure 7-73 Parameter configuration table for inter-RAT handover.................................................... 199

Tables
Table 2-1 Handover performance indexes and reference values ......................................................... 16
Table 2-2 HSDPA handover performance indexes and reference value............................................... 17
Table 2-3 HSUPA handover performance indexes and reference value............................................... 17
Table 2-4 CDR index and reference value........................................................................................... 19
Table 3-1 SHO failure indexes ............................................................................................................ 36
Table 3-2 HHO failure indexes............................................................................................................ 36
Table 3-3 Traffic statistics indexes of CS inter-RAT handover preparation failure................................. 38
Table 3-4 Traffic statistics indexes of PS inter-RAT outgoing handover failure ..................................... 39
Table 4-1 Types of CDR indexes......................................................................................................... 45
Table 4-2 Thresholds of EcIo and Ec .................................................................................................. 46
Table 4-3 Traffic statistics indexes for analyzing causes to call drop.................................................... 51
Table 5-1 Relationship between the filter coefficient and the corresponding tracing time...................... 58
Table 5-2 2G handover times.............................................................................................................. 63
Table 5-3 Best servers and other cells ................................................................................................ 67
Table 7-1 Timers and counters related to the synchronization and asynchronization.......................... 104
Table 7-2 Timers and counters related to call drop at lub interface .................................................... 107
Table 7-3 Flow of serving cell update triggered by different events in SHO........................................ 132
Table 7-4 Scenarios of handover between HSDPA and R99 (V17) .................................................... 144
Table 7-5 Handover between two HSUPA cells ................................................................................. 158
Table 7-6 Handover between a HSUPA cell and a non-HSUPA cell ................................................... 163
Table 7-7 Parameters of handover from 3G to 2G............................................................................. 190

W-Handover and Call Drop Problem Optimization Guide
Key words:
Handover, call drop, and optimization
Abstract:
This document, aiming at network optimization of handover success rate and call drop rate, details
the specific network operation flow. In addition, it analyzes common problems during network
optimization.
Acronyms and abbreviations:
Acronyms and Abbreviations Full Spelling
AMR Adaptive MultiRate
CHR Call History Record
CDR Call Drop Rate
DCCC Dynamic Channel Configuration Control
RAN Radio Access Network
RNP Radio Network Planning
SRB Signaling Radio Bearer
TRB Traffic Radio Bearer
SHO Soft Handover
HHO Hard Handover
PCH Physical Channel
CN Core Network
O&M Operation and maintenance
MNC Mobile Network Code
MCC Mobile Country Code
LAC Location Area Code
CIO Cell Independent Offset
HSUPA High Speed Uplink Packet Access
E-DCH Enhanced uplink Dedicated Channel
E-AGCH E-DCH Absolute Grant Channel

E-RGCH E-DCH Relative Grant Channel

1 Introduction
This document aims to meet the requirements by on-site engineers on solving handover and
call drop problems and making them qualified during network optimization. It describes the
methods for evaluating network handover and call drop performance, testing methods,
troubleshooting methods, and frequently asked questions (FAQs).
The appendix provides fundamental knowledge, principles, related parameters, and data
processing tools about handover and call drop. This document serves to network KPI
optimization and operation and maintenance (O&M) and helps engineers to locate and solve
handover and call drop problems.
The RRM algorithms and problem implementation in this document are based on V16 RNC. If
some RRM algorithms are based on V17 RNC, they will be highlighted. HSUPA is introduced in
V18 RNC, so the algorithms related to HSUPA are based on RNC V18. The following sections
are updated:
l Traffic Statistics Analysis for HSDPA Handover
l Handover Between HSDPA and R99
l Direct Retry of HSDPA
l Switch of Channel Type
Actually handover is closely relevant to call drop. Handover failure probably leads to call drop.
Therefore handover-caused call drop is arranged in handover success rate optimization part.
The CDR optimization includes all related to call drop except handover-caused call drop.
This document does not include usage of related tools.
This document includes the following 12 chapters:
l 1 Introduction
l 2 Handover and Call Drop Performance Indexes
l 3 Handover Index Optimization
l 4 CDR Index Optimization
l 5 FAQs Analysis
l 6 Summary
l 7 Appendix

The traffic statistics analysis is based on RNC V1.5 counter. It will be updated upon the update
of RNC counters.

2 Handover and Call Drop Performance Indexes
2.1 Handover Performance Indexes
According to RNA KPI baseline document, Table 2-1 lists the handover performance indexes
and reference values.
Table 2-1 Handover performance indexes and reference values
Index Service Statistics method Reference
value
SHO success rate CS&PS DT&Stat. 99%
Intra-frequency HHO
success rate
Voice DT&Stat. 90%
VP DT&Stat. 85%
PS UL64K/DL 64K DT&Stat. 85%
Inter-frequency HHO
success rate
Voice DT&Stat. 92%
VP DT&Stat. 90%
Inter-RAT handover
success rate
Voice handover out DT&Stat. 95%
PS handover out DT&Stat. 92%
SHO ratio N/A DT 35%
SHO cost N/A Stat. 40%

Table 2-2 lists the HSDPA handover performance indexes and reference value.
Table 2-2 HSDPA handover performance indexes and reference value
Index Service Reference value
HSDPA-HSDPA intra-frequency
serving cell update PS (HSDPA) 99%
HSDPA-HSDPA inter-frequency
serving cell update PS (HSDPA) 92%
HSDPA-R99 intra-frequency handover PS (HSDPA) 99%
HSDPA-R99 inter-frequency handover PS (HSDPA) 90%
Success rate of R99-to-HSDPA cell
handover PS (HSDPA) 85%
HSDPA-to-GPRS inter-RAT handover PS (HSDPA) 92%
Note: The HSDPA handover KPIs are to be updated after formal issue byWCDMA&GSM Performance
Research Department.
Table 2-3 HSUPA handover performance indexes and reference value
Success rate of inter-cell
SHO in HSUPA (including
adding, replacing, and
PS (HSUPA) –
deleting)
SHO serving cell update in
HSUPA
PS (HSUPA)
–
Success rate of
DCH-to-E-DCH
reconfiguration in SHO
mode (including replacing
and deleting)
PS (HSUPA)
–
Success rate of
E-DCH-to-DCH
reconfiguration in SHO
mode (including replacing
and deleting)
PS(HSUPA)
–
intra-frequency HHO in
HSUPA
PS (HSUPA)
–

Success rate of
–
intra-frequency HHO from a
HSUPA cell to a
PS (HSUPA)
non-HSUPA cell
Success rate of
DCH-to-E-DCH
reconfiguration in single-link
mode (the second step of
inter- or intra-frequency
HHO from a non-HSUPA
cell to a HSUPA cell)
PS (HSUPA)
–
inter-frequency HHO in
HSUPA
PS (HSUPA)
–
Success rate of
inter-frequency HHO from a
HSUPA cell to a
non-HSUPA cell
PS (HSUPA)
–
Success rate of
HSUPA-to-GPRS inter-RAT
handover
PS (HSUPA) 92%
Note:
The HSUPA handover KPIs are unavailable and to be updated after formal issue byWCDMA&GSM
Performance Department.
Decide the specific value according to project requirements or contract requirements of commercial network

2.2 Call Drop Performance Indexes
Table 2-4 lists the CDR index and reference value.
Table 2-4 CDR index and reference value
Index Service Statistics
method
Reference
value
CDR
Voice DT&Stat.&CQT 2%
VP DT&Stat.&CQT 2.5%
PS planned full
coverage rate DT&CQT 3%
PS (UL DCH full
coverage rate/DL
DT 3%
HSDPA)
PS Stat. 10%
PS (UL HSUPA/DL
HSDPA) DT 3%
The values listed in Table 2-4 are only for reference. Decide the specific value according to
project requirements or contract requirements of commercial network.
The call drop rate of HSDPA is not defined yet, so engineers use call drop rate of PS
temporarily.

3 Handover Index Optimization
3.1 DT/CQT Index Optimization Flow
DT and CQT are important to network evaluation and optimization. DT/CQT KPIs act as
standards for verifying networks. Overall DT helps to know entire coverage, to locate missing
neighbor cells, and to locate cross-cell coverage. HHO and inter-RAT handover are used in
coverage solutions for special scenarios, in while CQT is proper.
The following sections describe the DT/CQT index optimization flow in terms of SHO, HHO, and
inter-RAT handover.
3.1.1 SHO DT Index Optimization Flow
Figure 3-1 shows the SHO DT data analysis flow.

Figure 3-1 SHO DT data analysis flow
Inputting Analysis Data
Perform DT. Collect DT data, related signaling tracing, RNC CHR, and RNC MML scripts.
Obtaining When and Where the Problem Occurs
During the test, SHO-caused call drop might occur or SHO might fail, so record the location and
time for the problem occurrence. This prepares for further location and analysis.

Missing Neighbor Cell
During the early optimization, call drop is usually due to missing neighbor cell. For
intra-frequency neighbor cells, use the following methods to confirm intra-frequency missing
neighbor cell.
l Check the active set Ec/Io recorded by UE before call drop and Best Server Ec/Io
recorded by Scanner. Check whether the Best Server scramble recorded by
Scanner is in the neighbor cell list of intra-frequency measurement control before call
drop. The cause might be intra-frequency missing neighbor cell if all the following
conditions are met:
− The Ec/Io recorded by UE is bad.
− The Best Server Ec/Io is good.
− No Best Server scramble is in the neighbor cell list of measurement control.
l If the UE reconnects to the network immediately after call drop and the scramble of
the cell that UE camps on is different from that upon call drop, missing neighbor cell
is probable. Confirm it by measurement control (search the messages back from call
drop for the latest intra-frequency measurement control message. Check the
neighbor cell list of this measurement control message)
l UEs might report detected set information. If corresponding scramble information is
in the monitor set before call drop, the cause must be missing neighbor cell.
Missing neighbor cell causes call drop. Redundant neighbor cells impacts network performance
and increases the consumption of UE intra-frequency measurement. If this problem becomes
more serious, the necessary cells cannot be listed. Therefore pay attention to redundant
neighbor cells when analyzing handover problems. For redundant neighbor cells, see 5 .
Pilot Pollution
Pilot pollution is defined as below:
l Excessive strong pilots exist at a point, but no one is strong enough to be primary
pilot.
According to the definition, when setting rules for judging pilot pollution, confirm the following
content:
l Definition of strong pilot
Whether a pilot is strong depends on the absolute strength of the pilot, which is
measured by RSCP. If the pilot RSCP is greater than a threshold, the pilot is a
strong pilot. Namely, RSCP Absolute CPICH RSCP Th _ _ >
.
l Definition of "excessive"
When judging whether excessive pilots exist at a point, the pilot number is the
judgment criteria. If the pilot number is more than a threshold, the pilots at a point
are excessive. Namely, N CPICH _ Number > Th
l Definition of "no best server strong enough"
When judging whether a best server strong enough exist, the judgment criteria is the
relative strength of multiple pilots. If the strength different of the strongest pilot and
the No. ( +1) N Th strong pilot is smaller than a threshold, no best server strong
enough exists in the point. Namely,

l st Th th RSCP lative CPICH RSCP CPICH RSCP Th 1 ( N 1) _ Re ( _ - _ ) < +
Based on previous descriptions, pilot pollution exists if all the following conditions are met:
l The number of pilots satisfying RSCP Absolute CPICH RSCP Th _ _ >
is more
than N Th .
l st Th th RSCP lative CPICH RSCP CPICH RSCP Th 1 ( N 1) _ Re ( _ - _ ) < +
SetTh dBm RSCP Absolute 95 _ = - , = 3 N Th , and Th dB RSCP lative 5 _ Re = , the judgment standards
for pilot pollution are:
l The number of pilots satisfying CPICH _ RSCP 95dBm > - is larger than 3.
l
CPICH RSCP CPICH RSCP dB st th ( _ _ ) 5 1 4 - <
Improper Configuration of SHO Algorithm Parameters
Solve the following two problems by adjusting handover algorithm parameters.
l Delayed handover
According to the signaling flow for CS services, the UE fails to receive active set update
command (physical channel reconfiguration command for intra-frequency HHO) due to
the following cause. After UE reports measurement message, the Ec/Io of original cell
signals decreases sharply.When the RNC sends active set update message, the UE
powers off the transmitter due to asynchronization. The UE cannot receive active set
update message. For PS services, the UE might also fail to receive active set update
message or perform TRB reset before handover.
Delayed handover might be one of the following:
− Turning corner effect: the Ec/Io of original cell decreases sharply and that of the
target cell increases greatly (an over high value appears)
− Needlepoint effect: The Ec/Io of original cell decreases sharply before it increases
and the Ec/Io of target cell increase sharply for a short time.
According to the signaling flow, the UE reports the 1a or 1c measurement report of
neighbor cells before call drop. After this the RNC receives the event and sends the
active set update message, which the UE fails to receive.
l Ping-pong Handover
Ping-pong handover includes the following two forms
− The best server changes frequently. Two or more cells alternate to be the best server.
The RSCP of the best server is strong. The period for each cell to be the best server is
short.
− No primary pilot cell exists. Multiple cells exist with little difference of abnormal
RSCP. The Ec/Io for each cell is bad.
According to the signaling flow, when a cell is deleted, the 1A event is immediately
reported. Consequently the UE fails because it cannot receive the active set update
command.

Abnormal Equipment
Check the alarm console for abnormal alarms. Meanwhile analyze traced message, locate the
SHO problem by checking the failure message. For help, contact local customer service
engineers for confirm abnormal equipment.
Reperforming Drive Test and Locating Problems
If the problem is not due to previous causes, perform DT again and collect DT data. Supplement
data from problem analysis.
Adjustment and Implementation
After confirming the cause to the problem, adjust the network by using the following pertinent
methods:
l For handover problems caused by pilot pollution, adjust engineering parameters of
an antenna so that a best server forms around the antenna. For handover problems
caused by pilot pollution, adjust engineering parameters of other antennas so that
signals from other antennas becomes weaker and the number of pilots drops.
Construct a new site to cover this area if conditions permit. If the interference is from
two sectors of the same NodeB, combine the two cells as one.
l For abnormal equipment, consult customer service engineer for abnormal equipment
and transport layer on alarm console. If alarms are present on alarm console,
cooperate with customer service engineers.
l For call drop caused by delayed handover, adjust antennas to expand the handover
area, set the handover parameters of 1a event, or increase CIO to enable handover
to occur in advance. The sum of CIO and measured value is used in event
evaluation process. The sum of initially measured value and CIP, as measurement
result, is used to judge intra-frequency handover of UE and acts as cell border in
handover algorithm. The larger the parameter is, the easier the SHO is and UEs in
SHO state increases, which consumes resources. If the parameter is small, the SHO
is more difficult, which might affects receiving quality.
l For needle effect or turning corner effect, setting CIO to 5 dB is proper, but this
increases handover ratio. For detailed adjustment, see SHO-caused call drop of
FAQs Analysis.
l For call drop caused by Ping-pong handover, adjust the antenna to form a best
server or reduce Ping-pong handover by setting the handover parameter of 1B event,
which enables deleting a cell in active set to be more difficult. For details, increase
the 1B event threshold, 1B hysteresis, and 1B delay trigger time.
3.1.2 HHO CQT Flow
HHO Types
HHO includes the following types:
l Intra-frequency HHO
The frequency of the active set cell before HHO is the same as that of the cell after HHO.
If the cell does not support SHO, HHO might occur. HHO caters for cross-RNC

intra-frequency handover without lur interface, limited resources at lur interface, and
handover controlled by PS service rate threshold of handover cell. The 1D event of
intra-frequency measurement events determines intra-frequency HHO.
l Inter-frequency HHO
The frequency of the active set cell before HHO is different from that of the cell after
HHO. HHO helps to carry out balanced load between carriers and seamless proceeding.
Start compression mode to perform inter-frequency measurement according to UE
capability before inter-frequency HHO. HHO judgment for selecting cell depends on
period measurement report.
l Balanced load HHO
It aims to realize balanced load of different frequencies. Its judgment depends on
balanced load HHO.
Inter-frequency coverage usually exists in special scenarios, such as indoor coverage, so CQT
are used. The following section details the optimization flow for inter-frequency CQT.
Optimization Flow of HHO CQT
Figure 3-2 shows the optimization flow for HHO CQT.

Figure 3-2 Optimization flow for HHO CQT
Adjustment
The optimization flow for HHO is similar with that of SHO and the difference lies in parameter
optimization.
Confirming inter-frequency missing neighbor cell is similar to that of intra-frequency. When call
drop occurs, the UE does not measure or report inter-frequency neighbor cells. After call drop,
the UE re-camps on the inter-frequency neighbor cell.
HHO problems usually refer to delayed handover and Ping-pong handover.
Delayed HHO usually occurs outdoor, so call drop occurs when the UE is moving. There are
three solutions:
l Increase the threshold for starting compression mode.
The compression mode starts before inter-frequency or inter-RAT handover. Measure the
quality of inter-frequency or inter-RAT cell by compression mode. Compression mode
starts if the CPICH RSCP or Ec/Io meets the conditions. RSCP is usually the triggering
condition.
The parameter "inter-frequency measurement quantity" decides to use CPICH Ec/No or
Ec/Io as the measurement target for inter-frequency handover.When setting
"inter-frequency measurement quantity", check that the cell is at the carrier coverage
edge or in the carrier coverage center. If intra-frequency neighbor cells lie in all direction
of the cell, the cell is defined as in the carrier coverage center. If no intra-frequency cell
lies in a direction of the cell, the cell is defined as at the carrier coverage edge.

In the cell at the carrier coverage edge, when UE moves along the direction where no
intra-frequency neighbor cell lies, the CPICH Ec/No changes slowly due to the identical
attenuation rate of CPICH RSCP and interference. According to simulation, when
CPICH RSCP is smaller than the demodulation threshold (–100 dBm or so), the CPICH
Ec/No can still reach –12 dB or so. Now the inter-frequency handover algorithm based
on CPICH Ec/No is invalid. Therefore, for the cell at the carrier coverage edge, using
CPICH RSCP as inter-frequency measurement quantity to guarantee coverage is more
proper.
In the cell in the carrier coverage center, use CPICH RSCP as inter-frequency
measurement quantity, but CPICH Ec/No can better reflect the actual communication
quality of links and cell load. Therefore use CPICH Ec/No as inter-frequency
measurement quantity in the carrier coverage center (not the cell at the carrier coverage
edge), and RSCP as inter-frequency measurement quantity in the cell at the carrier
coverage edge.
In compression mode, the quality of target cell (inter-frequency or inter-RAT) is usually
measured and obtained. The mobility of MS leads to quality deterioration of the current
cell. Therefore the requirements on starting threshold are: before call drop due to the
quality deterioration of the current cell, the signals of the target cell must be measured
and reporting is complete. The stopping threshold must help to prevent compression
mode from starting and stopping frequently.
The RNC can distinguish CS services from PS services for inter-frequency measurement.
If the RSCP is smaller than –95 dBm, compression mode starts. If the RSCP is greater
than –90 dBm, compression mode stops. Adjust RSCP accordingly for special scenarios.
l Increase the CIO of two inter-frequency cells.
l Decrease the target frequency handover trigger threshold of inter-frequency
coverage.
For Ping-pong HHO problems, solve them by increasing HHO hysteresis and delay trigger time.
The intra-frequency HHO optimization is similar to that of inter-frequency. Decrease the
hysteresis and delay trigger time of 1D event according to local radio environment to guarantee
timely handover.
3.1.3 Inter-RAT Handover CQT Flow
Flow Chat
Figure 3-3 shows the inter-RAT handover CQT flow.

Figure 3-3 Inter-RAT handover CQT flow
Data Configuration
Inter-RAT handover fails due to incomplete configuration data, so pay attention to the following
data configuration.
l GSM neighbor configuration is complete on RNC. The configuration includes:
− Mobile country code (MCC)
− Mobile network code (MNC)
− Location area code (LAC)
− GSM cell identity (CELL ID)
− Network color code (NCC)
− Base station color code (BCC)
− Frequency band indicator (FREQ_BAND)
− Frequency number
− Cell independent offset (CIO)
Guarantee the correctness of the previous data and GSM network.

l Add location area cell information near 2G MSC to location area cell list of 3G MSC.
The format of location area identity (LAI) is MCC + MNC + LAC. Select LAI as LAI
type. Select Near VLR area as LAI class and add the corresponding 2G MSC/VLR
number. The cell GCI format is: MCC + MNC + LAC + CI. Select GCI as LAI type.
Select Near VLR area as LAI class and add the corresponding 2G MSC/VLR
number.
l Add data of WCDMA neighbor cells on GSM BSS. The data includes:
− Downlink frequency
− Primary scramble
− Main indicator
− MCC
− MISSING NEIGHBOR CELL
− LAC
− RNC ID
− CELL ID
According to the strategies of unilateral handover of inter-RAT handover, if the data
configuration is complete, the inter-RAT handover problems are due to delayed handover. A
frequently-used solution is increasing CIO, increasing the threshold for starting and stopping
compression mode, increasing the threshold to hand over to GSM.
Causes
The causes to call drop due to 3G-2G inter-RAT handover are as below:
l After the 2G network modifies its configuration data, it does not inform the 3G
network of modification, so the data configured in two networks are inconsistent.
l Missing neighbor cell causes call drop.
l The signals fluctuate frequently so call drop occurs.
l Handset problems causes call drop. For example, the UE fails to hand over back or
to report inter-RAT measurement report.
l The best cell changes upon Physical channel reconfiguration.
l Excessive inter-RAT cell are configured (solve it by optimizing number of neighbor
cells).
l Improperly configured LAC causes call drop (solve it by checking data configuration).
3.1.4 DT/CQT Flow for HSDPA Handover
Type
According to the difference of handover on DPCH in HSDPA network, the HSDPA handover
includes:
l SHO or softer handover of DPCH, with HS-PDSCH serving cell update

l Intra-frequency and inter-frequency HHO of DPCH, with HS-PDSCH serving cell
update
According to different technologies used in the serving cell before and after handover, HSDPA
handover includes:
l Handover in HSDPA system
l Handover between HSDPA and R99 cells
l Handover between HSDPA and GPRS cells
Methods
For HSDPA service coverage test and mobility-related test (such as HHO on DPCH with
HS-PDSCH serving cell update, handover between HSDPA and R99, and inter-RAT handover),
perform DT to know the network conditions.
For location of HSDPA problems and non-mobility problems, perform CQT (in specified point or
small area).
Flow
When a problem occurs, check R99 network. If there is similar problem with R99 network, solve
it (or, check whether the R99 network causes HSDPA service problems, such as weak coverage,
missing neighbor cell. Simplify the flow).
Figure 3-4 shows the DT/CQT flow for HSDPA handover.

Figure 3-4 DT/CQT flow for HSDPA handover
The problems with handover of HSDPA subscribers are usually caused by the faulty handover
of R99 network, such as missing neighbor cell and improper configuration of handover
parameters. When the R99 network is normal, if the handover of HSDPA subscribers is still
faulty, the cause might be improper configuration of HSDPA parameters. Engineers can check
the following aspects:
l Whether the HSDPA function of target cell is enabled and the parameters are
correctly configured. Engineers mainly check the words of cell and whether the
power is adequate, whether the HS-SCCH power is low. These parameters might
not directly cause call drop in handover, but lead to abnormal handover and lowered
the user experience.
l Whether the protection time length of HSDPA handover is proper. Now the baseline
value is 0s. Set it by running SET HOCOMM.
l Whether the threshold for R99 handover is proper. The handover flow for HSDPA is
greatly different from that of R99, so the handover of R99 service may succeed while
the HSDPA handover may fail. For example, in H2D handover, when the UE reports
1b event, it triggers RB reconfiguration in the original cell, reconfigures service
bearer to DCH, and updates the cell in active set. If the signals of the original cell
deteriorate quickly now, the reconfiguration fails.
l Whether the protection time length of D2H handover is proper. Now the baseline
value is 2s. Set it by running SET HOCOMM.

3.1.5 DT/CQT Flow for HSUPA Handover
The DT/CQT flow for HSUPA handover is similar to that for HSDPA. For details, refer to DT/CQT
Flow for HSDPA Handover.
For the test of HSUPA service coverage and mobility-related tests (such as the test of success
rate of HSUPA serving cell update), perform DT to know the network conditions. For locating
HSUPA problems and the problems unrelated to mobility, perform CQT (in specified spot or
area).
3.1.6 SHO Ratio Optimization
This part is to be supplemented.
3.1.7 MBMS Mobility Optimization
Currently, the radio network controller (RNC) V18 supports only the broadcast mode of the
multimedia broadcast multicast service (MBMS); the MBMS user equipment (UE) moves only
between point-to-multipoint (PTM) cells.
Figure 3-5 Movement of the MBMS UE between PTM cells
The movement of the MBMS UE between PTM cells is similar to the movement of UE
performing PS services in the CELL-FACH state. The UE performs the handover between cells

through cell reselection and obtains a gain through soft combining or selective combining
between two cells to guarantee the receive quality of the service. The UE first moves to the
target cell and then sends a CELL UPDATE message to notify the serving radio network
controller (SRNC) that the cell where the UE stays is changed. The SRNC returns a CELL
UPDATE CONFIRM message. The UE receives an MBMS control message from the MCCH in
the target cell and determines whether the MBMS radio bearer to be established is consistent
with that of the neighboring cell. If they are consistent, the original radio bearer is retained. The
MBMS mobility optimization, which guarantees that the UE obtains better quality of service at
the edge of cells, covers the following aspects:
l Optimize cell reselection parameters to guarantee that the UE can be reselected to
the best cell in time.
l Guarantee that the power of the FACH in each cell is large enough to meet the
coverage requirement of the MBMS UE at the edge of the cells.
l Guarantee that the transmission time difference of the UE between different links
meets the requirement of soft combing or selective combining*.
l Guarantee that the power, codes, transmission, and CE resources of the target cell
are not restricted or faulty, and that the MBMS service is successfully established.
The UE can simultaneously receive the same MBMS service from two PTM cells and combine
the received MBMS service. The UE supports two combining modes:
Soft combining: The transmission time difference between the current cell and the neighboring
cell is within (one TTI + 1) timeslots and the TFCI in each transmission time interval (TTI) is the
same.
Selective combining: The transmission time difference between the current cell and the
neighboring cell is within the reception time window stipulated by the radio link controller (RLC).
The SCCPCH is decoded and the transmission blocks are combined in the RLC PDU phase

3.2 Traffic Statistics Analysis Flow
The traffic statistics data is important to network in terms of information source. In addition, it is
the major index to evaluate network performance.
The handover traffic statistics data is includes RNC-oriented data and cell-oriented data. RNC
–oriented data reflects the handover performance of entire network, while cell-oriented data
helps to locate problematic cells.
The analysis flow for SHO, HHO, inter-RAT handover, and HSDPA handover is similar, but the
traffic statistics indexes are different from them.
Figure 3-6 shows the analysis flow for handover traffic statistics data.

Figure 3-6 Analysis flow for handover traffic statistics data
3.2.1 Analysis Flow for SHO Traffic Statistics
The SHO success rate is defined as below:
SHO success rate = SHO successful times/SHO times
According to the flow, SHO includes SHO preparation process and SHO air interface process.
The SHO preparation process is from handover judgment to RL setup completion. The SHO air
interface process is active set update process.
l Check the SHO success rate of entire network and cell in busy hour. If they are not
qualified, analyze the problematic cells in details.
l Sort the SHO (or softer handover) failure times of the cell by TOP N and locate the
cells with TOP N failure times. List the specific indexes of failure causes. If locating
specific causes from traffic statistics is impossible, analyze the corresponding CHR.
Table 3-1 lists the detailed traffic statistics indexes to SHO (or softer handover) failure
and analysis.

Table 3-1 SHO failure indexes
Failure causes Analysis
Configuration nonsupport The UE thinks the content of active set update for RNC to add/delete links
does not support SHO. This scenario seldom exists in commercial networks.
Synchronization
reconfiguration
nonsupport
The UE feeds back that the SHO (or softer handover) for RNC to add/delete
links is incompatible with other subsequent processes. The RNC
guarantees serial processing upon flow processing. This cause is due to the
problematic UE.
Invalid configuration The UE thinks the content of active set update for RNC to add/delete links is
invalid. This scenario seldom exists in commercial networks.
No response from UE
The RNC fails to receive response to active set update command for
adding/deleting links. This is a major cause to SHO (or softer handover)
failure. It occurs in areas with weak coverage and small handover area. RF
optimization must be performed in the areas.
l Perform DT to re-analyze problems. The traffic statistics data provides the trend and
possible problems. Further location and analysis of problems involves DT and CHR
to the cell. DT is usually performed on problematic cells and signaling flow at the UE
side and of RNC is traced. For details, see 3.1.3 .
3.2.2 Analysis Flow of HHO Traffic statistics
The HHO traffic statistics includes outgoing HHO success rate and incoming HHO success rate:
l Outgoing HHO Success Rate = Outgoing HHO Success Times/Outgoing HHO
Times
l Incoming HHO Success Rate = Incoming HHO Success Times/Incoming HHO
Times
Upon HHO failure, pay attention to indexes related to internal NodeB, between NodeBs, and
between RNCs.
Table 3-2 lists the HHO failure indexes.
Table 3-2 HHO failure indexes
Failure cause Analysis
HHO preparation failure
Radio link setup failure Analyze RL setup failure.
Other causes Analyze the problem further based on CHR logs.
Internal NodeB/Between NodeBs/Between RNCs HHO failure
Configuration
nonsupport
The UE thinks it cannot support the command for outgoing HHO,
because it is incompatible with HHO.
PCH failure The cause is probably weak coverage and strong interference.
Synchronization
reconfiguration
nonsupport
The UE feeds back HHO is incompatible with other consequent processes
due to compatibility problems of UE.

Cell update Cell update occurs upon outgoing HHO. These two processes lead to
outgoing HHO failure.
Invalid configuration The UE thinks the command for outgoing HHO as invalid. This is a
compatibility problem of UE.
Other causes Analyze the problem further based on CHR logs.
3.2.3 Traffic Statistics Analysis Flow for Inter-RAT Handover
The inter-RAT handover success rate includes voice inter-RAT handover success rate and PS
inter-RAT handover success rate.
Voice Inter-RAT Outgoing Handover Success Rate = Voice Inter-RAT Outgoing Handover
Success Times/Voice Inter-RAT Outgoing Handover Attempt Times
Voice Inter-RAT Outgoing Handover Success Times: when the RNC sends a RELOCATION
REQUIRED message.
Voice Inter-RAT Outgoing Handover Attempt Times: during CS inter-RAT outgoing, when the
RNC receives an IU RELEASE COMMAND message, with the reason value Successful
Relocation, or Normal Release.
PS Inter-RAT Outgoing Handover Success Rate = PS Inter-RAT Outgoing Handover Success
Times/PS Inter-RAT Outgoing Handover Implementation Times
PS Inter-RAT Outgoing Handover Success Times: the RNC sends a CELL CHANGE ORDER
FROM UTRAN message to UE.
PS Inter-RAT Outgoing Handover Implementation Times: when the RNC receives an IU
RELEASE COMMAND message, with the reason value Successful Relocation, or Normal
Release.
Voice Inter-RAT Outgoing Handover Success Rate
The voice inter-RAT outgoing handover includes handover preparation process and
implementation process.
Figure 3-7 shows the voice inter-RAT outgoing handover flow.

Figure 3-7 Voce inter-RAT outgoing handover flow
During CS inter-RAT outgoing handover process, when the RNC sends a RELOCATION
REQUIRED message to CN, if the current CS service is AMR voice service, count it as an
inter-RAT handover preparation. When the RNC receives the IU RELEASE COMMAND
message replied by CN, count it as inter-RAT outgoing handover success according to the
SRNC cell being used by UE.
If CS inter-RAT handover fails, check the failure statistics indexes listed in Table 3-3.
Table 3-3 Traffic statistics indexes of CS inter-RAT handover preparation failure
RNC-level inter-RAT outgoing handover preparation failure
Expiration of
waiting for SRNS
relocation
command
The CN does not respond the corresponding command for handover
preparation request, because the CN parameter configuration or the
corresponding link connection is problematic. To solve this problem,
analyze the causes according to CN and BSS signaling tracing.
SRNS relocation
cancellation
After the RNC requests handover preparation, it receives the release
command from CN. This includes the following two cases:
l The inter-RAT handover request occurs during signaling process like
location update, so the flow is not complete before location update is
complete. Finally the CN sends a release message.
l The subscribers that are calling hang UE before handover preparation,
so the CN sends a release message.
The previous two cases, despite incomplete handover, are normal nesting
flows.
SRNS relocation
expiration
It corresponds to incorrect configuration of CN, so you must analyze the
causes according to CN and BSS signaling tracing.
SRNS relocation
failure in target
CN/RNC/system
It corresponds to incorrect configuration of CN or BSS nonsupport, so you
must analyze the causes according to CN and BSS signaling tracing.

Unknown target
RNC
It corresponds to incorrect configuration of MSC parameters without
information like LAC of target cell, so you must check the parameter
configuration. It occurs easily after adjustment of 2G networks.
Unavailable
resource
It corresponds to incorrect configuration of MSC parameters or unavailable
BSC resources, so you must analyze the causes according to CN and BSS
signaling tracing.
Other causes Analyze the causes according to CN and BSS signaling tracing.
Cell-level inter-RAT outgoing handover preparation failure
SRNS relocation
expiration
The CN parameter configuration or the corresponding link connection is
problematic, so you must analyze the causes according to CN and BSS
signaling tracing.
SRNS relocation
failure in target
CN/RNC/system
It corresponds to incorrect configuration of CN or BSS nonsupport, so you
must analyze the causes according to CN and BSS signaling tracing.
SRNS relocation
nonsupport in
target
CN/RNC/system
The BSC fails to support some parameters of inter-RAT handover request,
so you must analyze the causes according to CN and BSS signaling
tracing.
Other causes Analyze the causes according to CN and BSS signaling tracing.
RNC-level/CELL-level inter-RAT outgoing handover failure
Configuration
nonsupport
The UE fails to support the handover command in the network, so the UE
is incompatible with the handover command.
PCH failure The 2G signals are weak or the interference is strong so the UE fails to
connect to the network.
Other causes Analyze the problem further according to CHR logs and CN/BSS signaling
tracing.
PS Inter-RAT Handover Success Rate
After the RNC sends the CELL CHANGE ORDER FROM UTRAN message, the PS inter-RAT
outgoing handover fails if it receives the CELL CHANGE ORDER FROM UTRAN FAILURE
message. You must check the indexes listed in Table 3-4.
Table 3-4 Traffic statistics indexes of PS inter-RAT outgoing handover failure
RNC-level/CELL-level PS inter-RAT outgoing handover preparation failure
Configuration
nonsupport
The UE fails to support the handover command of the network, because
the UE is incompatible with the command.
PCH failure The 2G signals are weak or the interference is strong, so the UE fails to
access the network.
Radio network
layer cause
The UE is probably incompatible. The UE detects that the sequence
number of SNQ in the AUTN message is correct, so the handover fails.
The value is synchronization failure.
Transport layer
cause The corresponding transport link is abnormal.

Other causes You must analyze the causes according to CN and BSS signaling tracing.
3.2.4 Traffic Statistics Analysis for HSDPA Handover
HSDPA switch includes
l H-H (HS-DSCH to HS-DSCH) intra-frequency serving cell update
l H-H inter-frequency serving cell update
l HSDPA-R99 intra-frequency switch
l HSDPA-R99 inter-frequency switch
l HSDPA-GPRS switch
The traffic statistics indexes are defined as below:
l Success rate of H-H intra-frequency serving cell update = (Times of successful
update of serving cell)/(attempt times update of serving cell)
When the RNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message,
if the serving cell is updated, engineers count the attempt times of serving cell in the
original serving cell.When the RNC receives the PHYSICAL CHANNEL RECFG
COMPLETE message, if the serving cell changes, the RNC counts the times of
successful update of serving cells in the original serving cell when the UE is in the SHO
mode not in the HHO mode.
l Success rate of H-H inter-frequency serving cell update = Times of successful
outgoing inter-frequency HHO from HS-DSCH to HS-DSCH/Times of requested
outgoing inter-frequency HHO from HS-DSCH to HS-DSCH
When the RNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message,
and the inter-frequency HHO is from HS-DSCH to HS-DSCH, the RNC counts the times
of requested outgoing inter-frequency HHO from HS-DSCH to HS-DSCH.When the
RNC receives the PHYSICAL CHANNEL RECFG COMPLETE message from UE, and
the inter-frequency HHO is from HS-DSCH to HS-DSCH, engineers count the times of
successful outgoing inter-frequency HHO from HS-DSCH to HS-DSCH.
l Success rate of H-H inter-frequency serving cell update = successful times of
outgoing inter-frequency HHO from HS-DSCH to HS-DSCH/attempt times HHO from
DCH to HS-DSCH in the cell
When the RNC sends the UE the PHYSICAL CHANNEL RECONFIGURATION
message, if the switch is the inter-frequency HHO from HS-DSCH to HS-DSCH, the
RNC counts the successful times of inter-frequency HHO from HS-DSCH to HS-DSCH
in the cell.
l Success rate of H-to-R99 intra-frequency SHO = successful times of switch from
HS-DSCH to DCH in multi-link mode in the cell/attempt times switch from HS-DSCH
to DCH in multi-link mode in the cell.
Success rate of R99-to-H intra-frequency SHO = successful times of switch from
DCH to HS-DSCH in multi-link mode in the cell/attempt times switch from DCH to
HS-DSCH in multi-link mode in the cell.
In the DCCC or RAB MODIFY process, if the RNC decides to switch the channel in the
cell, it sends the UE the RF RECONFIGURATION message. According to the channel
state of the UE before and after reconfiguration, the RNC counts the previous indexes in
the HSDPA serving cell.

l Success rate of H-to-R99 intra-frequency HHO = successful times of outgoing
intra-frequency HHO from HS-DSCH to DCH in the cell/attempt times outgoing
intra-frequency HHO from HS-DSCH to DCH in the cell.
message, if the switch is the intra-frequency switch from HS-DSCH to DCH, the RNC
counts the attempt times of inter-frequency HHO from HS-DSCH to DCH in the cell.
When the RNC receives the PHYSICAL CHANNEL RECFG COMPLETE message
from the UE, if the switch is the intra-frequency HHO from HS-DSCH to DCH, the
RNC counts the successful times of outgoing intra-frequency HHO from HS-DSCH to
DCH in the cell.
Success rate of H-to-R99 inter-frequency switch update
The RNC algorithm is unavailable now, so this index is unavailable.
l Success rate of H-to-R99 inter-frequency switch update = successful times of
outgoing HHO from HS-DSCH to DCH in the cell/attempt times outgoing
inter-frequency HHO from HS-DSCH to DCH in the cell
message, if the switch is the inter-frequency switch from HS-DSCH to DCH, the RNC
counts the attempt times inter-frequency HHO from HS-DSCH to DCH in the cell.When
the RNC receives the PHYSICAL CHANNEL RECFG COMPLETE message from the
UE, if the switch is the inter-frequency HHO from HS-DSCH to DCH, the RNC counts
the successful times of outgoing inter-frequency HHO from HS-DSCH to DCH in the
cell.
Success rate of R99-to-H
The RNC algorithm is unavailable now, so this index is unavailable.
l Success rate of R99-to-H switch = successful times of switch from DCH to
HS-DSCH in the cell/attempt times of switch from DCH to HS-DSCH in the cell
In the DCCC or RAB MODIFY process, if the RNC decides to switch the channel in the
cell, it sends the UE the RF RECONFIGURATION message. According to the channel
state of the UE before and after reconfiguration, the RNC counts the attempt times of
switch from DCH to HS-DSCH in the HSDPA serving cell. In the DCCC or RAB
MODIFY process, if the RNC receives the RB RECONFIGURATION COMEPLTE
message from UE, and the reconfiguration enables UE to switch from the DCH to
HS-DSCH in the same cell, the RNC counts the successful times of switch from DCH to
HS-DSCH in the HSDPA serving cell.
l Success rate of H-to-GPRS handover update
The traffic statistics does not include the index, and the index will be supplemented later.
The causes to failure and analysis methods will be summarized later.
3.2.5 Traffic Statistics Analysis for HSUPA Handover
The traffic statistics indexes for HSUPA are defined as below:
l Success rate of SHO between HSUPA cells (including adding, replacing, and
deleting) = attempt times of active set update/complete times of active set update.
l Success rate of SHO serving cell update between HSUPA cells = successful times
of SHO serving cell update/attempt times of SHO serving cell update.

l Success rate of reconfiguration from DCH to E-DCH in the cell (SHO,
intra-frequency HHO, and inter-frequency HHO) = successful times of handover from
DCH to E-DCH/attempt times of handover from DCH to E-DCH.
l Success rate of reconfiguration from E-DCH to DCH in the cell (including adding and
replacing) = successful times of handover from E-DCH to DCH in SHO
mode/attempt times of handover from E-DCH to DCH in SHO mode.
l Success rate of intra-frequency HHO serving cell between HSUPA cells = successful
times of intra-frequency HHO serving cell between HSUPA cells/attempt times of
intra-frequency HHO serving cell between HSUPA cells.
l Success rate of intra-frequency HHO from E-DCH to DCH from a HSUPA cell to a
non-HSUPA cell = successful times of intra-frequency HHO from E-DCH to
DCH/attempt times of intra-frequency HHO from E-DCH to DCH.
l Success rate of inter-frequency HHO serving cell update between HSUPA cells =
successful times of inter-frequency HHO serving cell update between HSUPA
cells/attempt times of inter-frequency HHO serving cell update between HSUPA
cells.
l Successful times of inter-frequency HHO from a HSUPA cell to a non-HSUPA cell =
successful times of inter-frequency HHO from E-DCH to DCH/request times of
inter-frequency HHO from E-DCH to DCH.

3.3 SHO Cost Optimization
To be supplemented.

4 CDR Index Optimization
4.1 Definition of Call Drop and Traffic Statistics Indexes
4.1.1 Definition of DT Call Drop
According to the air interface signaling recorded at the UE side, during connection, DT call drop
occurs when the UE receives:
l Any BCH message (system information)
l The RRC Release message with the release cause Not Normal.
l Any of the CC Disconnect, CC Release Complete, CC Release message with the
release cause Not Normal Clearing, Not Normal, or Unspecified.
4.1.2 Descriptions of Traffic Statistics Indexes
A generalized CDR consists of CN CDR and UTRAN CDR. RNO engineers focus on UTRAN
CDR, so the following sections focus on KPI index analysis at UTRAN side.
The related index at UTRAN side is the number of RAB for each service triggered by RNC. It
consists of the following two aspects:
l After the service is set up, the RNC sends CN the RAB RELEASE REQUEST
message.
l After the service is set up, the RNC sends CN the IU RELEASE REQUEST
message. Afterwards, it receives the IU RELEASE COMMAND sent by CN.
Upon statistics, sort them by specific services. Meanwhile, traffic statistics includes the cause to
release of RAB of each service by RNC.
CS CDR is calculated as below:
å =
CS _ CDR 100 å
* %
CSRabrelTriggedByRNC
CSRABSetupSuccess
PS CDR is calculated as below:

å =
PS _ CDR 100 å
* %
PSRabrelTriggedByRNC
PSRABSetupSuccess
The failure cause indexes are sorted in Table 4-1.
Table 4-1 Types of CDR indexes
CDR type Cause Corresponding signaling process
Due to air
interface
RF RLC reset and RL Failure
Expiration
of process
timer
RB RECFG
Expiration of PHY/TRCH/SHO/ASU
HHO failure
Not due to
air
interface
Hardware
failure
The transport failure between RNC and NodeB. NCP
reports failure.
FP synchronization failure.
Transport
layer failure ALCAP report failure
Subscribers
are
released by
O&M intervention
force by
MML
The definition of RAN traffic statistics call drop is according to statistics of lu interface signaling,
including the times of RNC's originating RAB release request and lu release request. The DT
call drop is defined according to the combination of messages at air interface and from
non-access lay and cause value. They are inconsistent.
4.2 DT/CQT Optimization Flow
Figure 4-1 shows flow chart for analyzing call drop.

Figure 4-1 Flow chart for analyzing call drop
4.2.1 Call Drop Cause Analysis
Call drop occurs usually due to handover, which is described in chapter 3 . The following
sections describe the call drop not due to handover.
Weak Coverage
For voice services, when CPICH Ec/Io is greater than –14 dB and RSCP is greater than –100
dBm (a value measured by scanner outside cars), the call drop is usually not due to weak
coverage. Weak coverage usually refers to weak RSCP.
Table 4-2 lists the thresholds of Ec/Io and Ec (from an RNP result of an operator, just for
reference).
Table 4-2 Thresholds of EcIo and Ec
Service Bit rate of
service DL EbNo EcIo
thresholds Ec thresholds
CS 12.2 12.2 8.7 –13.3 –103.1

CS 64 64 5.9 –11.9 –97.8
PS 64 64 5.1 –12.7 –98.1
PS 128 128 4.5 –13.3 –95.3
PS 384 384 4.6 –10.4 –90.6
Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink by
the following methods.
l If the uplink transmission power reaches the maximum before call drop, the uplink
BLER is weak or NodeB report RL failure according to single subscriber tracing
recorded by RNC, the call drop is probably due to weak uplink coverage.
l If the downlink transmission power reaches the maximum before call drop and the
downlink BLER is weak, the call drop is probably due to weak downlink coverage.
In a balanced uplink and downlink without uplink or downlink interference, both the uplink and
downlink transmit power will be restricted. You need not to judge whether uplink or downlink is
restricted first. If the uplink and downlink is badly unbalanced, interference probably exists in the
restricted direction.
A simple and direct method for confirming coverage is to observe the data collected by scanner.
If the RSCP and Ec/Io of the best cell is low, the call drop is due to weak coverage.
Weak coverage might be due to the following causes:
l Lack of NodeBs
l Incorrectly configured sectors
l NodeB failure due to power amplifier failure
The over great indoor penetration loss causes weak coverage. Incorrectly configured sectors or
disabling of NodeB will occur, so at the call drop point, the coverage is weak. You must
distinguish them.
Interference
Both uplink and downlink interference causes call drop.
In downlink, when the active set CPICH RSCP is greater than –85 dBm and the active set Ec/Io
is smaller than –13 dB, the call drop is probably due to downlink interference (when the
handover is delayed, the RSCP might be good and Ec/Io might be weak, but the RSCP of Ec/Io
of cells in monitor set are good). If the downlink RTWP is 10 dB greater than the normal value
(–107 to –105 dB) and the interference lasts for 2s–3s, call drop might occur. You must pay
attention to this.
Downlink interference usually refers to pilot pollution. When over three cells meets the handover
requirements in the coverage area, the active set replaces the best cell or the best cell changes
due to fluctuation of signals. When the comprehensive quality of active set is bad (CPICH Ec/Io
changes around –10 dB), handover failure usually causes SRB reset or TRB reset.
Uplink interference increases the UE downlink transmit power in connection mode, so the over
high BLER causes SRB reset, TRB reset, or call drop due to asynchronization. Uplink
interference might be internal or external. Most of scenario uplink interference is external.
Without interference, the uplink and downlink are balanced. Namely, the uplink and downlink
transmit power before call drop will approach the maximum. When downlink interference exists,

the uplink transmit power is low or BLER is convergent. When the downlink transmit power
reaches the maximum, the downlink BLER is not convergent. It is the same with uplink
interference. You can use this method to distinguish them.
Abnormality Analysis
If the previous causes are excluded, the call drop might due to problematic equipment. You
need to check the logs and alarms of equipment for further analysis. The causes might be as
below:
l An abnormal NodeB causes failure of synchronization, so links keeps being added
and deleted.
l The UE does not report 1a measurement report so call drop occurs.
You need to focus on the call drop due to abnormal testing UE, which occurs easily during CQT.
Namely, the data recorded in DT does not contain the information reported by UE for a period.
HSPA Call Drop Analysis
For HSPA call drop analysis, refer to previous causes to R99 call drop.
4.2.2 Frequently-adjusted Non-handover Algorithm Parameters
The frequently-adjusted non-handover algorithm parameters in call drop are as below:
Maximum Downlink Transmit Power of Radio Link
Configuring the transmit power of dedicated link to a great value helps to eliminate call drop
points due to weak coverage, but it brings interference. The power of a single subscriber is
allowed to be great, so the subscriber might impact other subscribers or lower downlink capacity
of system when the subscriber consumes great power at the edge of a cell.
The configuration of downlink transmit power is usually provided by link budget. An increase or
decrease of 1–2 dB has little impact on call drop in signal DT, but it can be seen from traffic
statistics indexes. The CDR of some cells is high due to weak coverage, you can increase the
maximum transmit power of DCH. The access failure probability of some cells is high due to
over high load, you can lower the maximum downlink transmit power of radio link.
Maximum Retransmission Times of Signaling and Services
When the BLER of the channel is high, the signaling is reset because the retransmission
reaches the maximum times. A reset of signaling causes call drop. The services using AM mode
for service transmission will also retransmit signaling. If the retransmission reaches the
maximum times, the signaling is reset. The system configures the maximum reset times. When
the reset times reaches the maximum, the system starts to release the service, which causes
call drop.
The default configuration of system guarantees that burst blocks will not cause abnormal call
drop, and call drop occurs when UE moves to an area with weak coverage and when the reset
is time, so the system releases resources. In some scenarios, burst interference or needle
effect exists, so 100% block error occurs during burst interference. If you want have less call
drop, increase the retransmission times improper to resist burst interference.
This parameter is configured for RNC.

4.2.3 Judgment Tree for Call Drop Causes
Based on various causes to call drop, the judgment tree for analyzing call drop is as shown in
Figure 4-2.
Figure 4-2 Judgment tree for call drop causes
Preparing Data
The data to be prepared include:
l Data files collected by DT
l Single subscriber tracing recorded by RNC
l CHR recorded by RNC
Obtaining Call Drop Location
You need to use special software to process DT data. For example, the software Assistant helps
to obtain call drop time and location, PICH data collected by scanner, information about active
set and monitor set collected by UE, and the signaling flow.

Analyzing Signal Variation of Best server From Scanner
Analyze the signal variation of best server from scanner.
l If the signals of best server are stable, analyze RSCP and Ec/Io.
l If the signals of best server fluctuate sharply, you must analyze the quick variation of
best server signals and the situation without best server. Consequently you can
analyze call drop due to ping-pong handover.
Analyzing RSCP and Ec/Io of Best cell
Observe the RSCP and Ec/Io of best cell according to scanner.
l If both RSCP and Ec/Io are bad, call drop must be due to weak coverage.
l If RSCP is normal but Ec/Io is bad (delayed handover is excluded, intra-frequency
neighbor cell interference), call drop must be due to downlink interference.
l If both RSCP and Ec/Io are normal,
When the cell in UE active set is inconsistent with the best cell according to scanner, call
drop must be due to missing neighbor cell and delayed handover.
When the cell in UE active set is consistent with the best cell according to scanner, call
drop must be due to uplink interference or must be abnormal.
Re-perform DT to Solve Problems
A DT might not help to collect all information needed to locate call drop problems, so further DTs
are needed. In addition, you can confirm whether the call drop point is random or fixed by
further DT. You must eliminate fixed call drop points, but you can choose to eliminate random
call drop points.
4.3 Traffic Statistics Analysis Flow
When analyzing traffic statistics indexes, you need to check RNC call drop indexes and master
the overall situation of network operation. Meanwhile, you must analyze the cell concern for
detailed call drop indexes. You can obtain call drop of different services and approximate
causes to call drop by using traffic statistics analyzers.
To analyze traffic statistics indexes, you must analyze the cells with obviously abnormal indexes.
If the KPIs of the cell are good, there must be problems with version, hardware, transport,
antenna-feeder, or data. Based on alarms, you can check these aspects.
If there are no abnormalities, you can form a list of cells with bad KPIs by classifying sector
carriers. Analyze traffic statistics indexes of these cells (such as more indexes related, analyzing
the interval between two periods, indexes leading to call drop, and handover indexes), and
check the causes to call drop based on CHR. When solving problems, you need to focus on one
index and combine other indexes.
When the traffic volume reaches a certain level, the traffic statistics indexes work. For example,
a CDR of 50% does not indicate a bad network. Only when the absolute value of call times, call
success times, and total times of call drop is meaningful in terms of statistics, the traffic statistics
indexes work.
The flow for analyzing traffic statistics is as below.

4.3.1 Analyzing RNC CDR
The RNC CDR involves the number of RAB of each service triggered by RNC, including two
aspects:
l After a service is established successfully, the RNC sends CN the RAB RELEASE
REQUEST message.
l After a service is established successfully, the RNC sends CN the IU RELEASE
REQUEST message, and then receives the IU RELEASE COMMAND message sent
by CN.
AMR CDR = VS.RAB.Loss.CS.RF.AMR / VS.RAB.SuccEstab.AMR.
VP CDR = VS.RAB.Loss.CS.Conv64K / VS.RAB.SuccEstCS.Conv.64.
To analyze PS call drop of various rates, you can analyze the following indexes:
l VS.RAB.Loss.PS.64K / VS.RAB.SuccEstPS.64
Based on analysis of previous indexes, you can obtain the performance of various services and
rates in the network, as well as SHO/HHO call drop. More important, you can obtain the cells
with bad indexes and periods.
4.3.2 Analyzing Causes to Call Drop
In traffic statistics analysis, you must analyze the major causes to call drop.
Table 4-3 lists the major indexes for analyzing traffic statistics.
Table 4-3 Traffic statistics indexes for analyzing causes to call drop
OM interference The O&M tasks cause call drop.
Causes due to RAB
preemption
High-priority preemption causes release of CS links. This kind of call drop
occurs when the load and resources are limited. Performing expansion
depends on the times of occurrence.
Causes due to UTRAN
The causes due to UTRAN in the cell lead to abnormal release of link. This
corresponds to abnormal process, so you must further analyze it based on
CHR.
Uplink RLC reset Uplink RLC reset causes release of links, because the coverage quality
(including missing neighbor cell and over mall handover area) is bad.
Downlink RLC reset Downlink SRB reset causes release of links, because the coverage quality
(including missing neighbor cell and over mall handover area) is bad.
Uplink synchronization
failure
Uplink synchronization failure causes abnormal release of links. The
coverage quality (including missing neighbor cell and over mall handover
area) is bad, so the UE powers off the transmitter abnormally or uplink
demodulation is asynchronous.

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