W-Handover and Call Drop Problem Optimization Guide-20081223-A-3.3

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Product name Confidentiality level

WCDMA RNP For internal use only

Product version

Total 200 pages 3.3

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

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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Optimizing some cases, adding new cases, and removing outdated cases and terms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

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

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Date Version Description Author

2007-08-09 3.2 Adding HSUPA-related description. Zhang Hao

2008-12-15

3.3 Adding MBMS-related description. Yearly review

WangDekai / Hu Wensu

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Figures

SHO DT data analysis flow...20

Optimization flow for HHO CQT...25

Inter-RAT handover CQT flow...27

DT/CQT flow for HSDPA handover...30

Movement of the MBMS UE between PTM cells...31

Analysis flow for handover traffic statistics data...34

Voce inter-RAT outgoing handover flow...37

Flow chart for analyzing call drop...45

Judgment tree for call drop causes...48

Flow for analyzing call tracing...52

SHO relative threshold...56

Signaling flow recorded by UE before call drop...57

Scrambles recorded by UE active set and scanner before call drop...58

Scrambles in UE active set before call drop...59

UE intra-frequency measurement control point before call drop...60

Analyzing signaling of UE intra-frequency measurement control before call drop...60

Confirming missing neighbor cell without information from scanner...61

Location relationship of 2G redundant neighbor cells...63

Pilot pollution near Yuxing Rd...64

Best ServiceCell near Yuxing Rd...64

The 2nd best ServiceCell near Yuxing Rd...65

The 3rd best ServiceCell near Yuxing Rd...65

The 4th best ServiceCell near Yuxing Rd...66

Composition of pilot pollution near Yuxing Rd...66

RSSI near Yuxing Rd...67

RSCP of Best ServiceCell near Yuxing Rd...67

RSCP of SC270 cell near Yuxing Rd...68

Pilot pollution near Yuxing Rd. after optimization...69

Best ServiceCell near Yuxing Rd. after optimization...69

RSCP of best ServiceCell near Yuxing Rd. after optimization...70

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Turning corner effect-signals attenuation...71

Turning corner effect-signal attenuation recorded by the UE...71

Turning corner effect-traced signaling recorded by the RNC...72

Needle point-signal variance...73

Call drop distribution of PS384K intra-frequency hard handover...74

Signal distribution of cell152 vs. cell88 (signal fluctuation in handover areas)...75

Reporting 1D event...76

Increasing hysteresis to reduce frequently reporting of 1D event...77

Attenuation relationship of RSCP and Ec/No...78

Indoor 3G RSCP distribution...82

Analyzing weak signals...90

Uplink interference according to RNC signaling...92

Uplink interference according to UE signaling...92

Uplink interference information recorded by UE...93

RTWP variation of the cell 89767...93

RTWP variation of the cell 89768...94

Pilot information recorded by scanner...96

UMTS QoS structure ...101

SRB and TRB at user panel...102

Signaling flow for adding radio link...109

Signaling flow for deleting radio link...111

SHO signaling flow for adding and deleting radio link...113

Measurement model...115

Example 1A event and trigger delay...117

Periodic report triggered by 1A event...118

Example of 1C event...119

Example 1D event...120

Restriction from hysteresis to measurement report...120

Example of 1E event...121

Example of 1F event...121

Ordinary HHO flow (lur interface and CELL_DCH state)...123

Ordinary inter-CN HHO flow...125

Intra-NodeB synchronization serving cell update...132

Inter-NodeB synchronization serving cell update...134

Inter-NodeB HS-DSCH cell update after radio link is added...136

Inter-NodeB HS-DSCH cell update during HHO (single step method)...138

DPCH intra-frequency HHO with HS-DSCH serving cell update...140

DPCH inter-frequency HHO with HS-DSCH serving cell update...141

handover from HSDPA to R99...142

Intra-frequency handover from R99 to R5...142

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DPCH SHO with handover from R99 to HSDPA...145

Inter-NodeB SHO with handover from HSDPA to R99 (V17)...146

Intra-frequency HHO with handover from R5 to R99...147

Intra-frequency HHO with handover form R99 to R5...147

Intra-frequency HHO with handover from R5 to R99 (V17)...148

Inter-frequency HHO from HS-PDSCH to DCH...149

Inter-frequency HHO from DCH to HS-PDSCH...150

Handover between HSDPA and GPRS...151

Flow for direct retry during setup of a service...152

Direct retry triggered by traffic...152

Switch of channel type...154

Intra-frequency SHO between two HSUPA cells...158

Signaling for HSUPA cell update triggered by a 1D event...158

Signaling for HSUPA cell update triggered by a 1D event (reported by the monitor set)...159

Intra-frequency HHO between two HSUPA cells...159

Signaling for intra-frequency HHO between two HSUPA cells...160

Inter-frequency HHO between two HSUPA cells...160

Signaling for inter-frequency HHO between two HSUPA cells...161

Inter-RNC HSUPA handover...162

SHO from a HSUPA cell to a non-HSUPA cell...164

Addition of an R99 cell when the service is on the E-DCH...165

Intra-frequency HHO from a HSUPA cell to a non-HSUPA cell...166

Signaling for intra-frequency HHO from a HSUPA cell to a non-HSUPA cell...166

Inter-frequency HHO from a HSUPA cell to a non-HSUPA cell...167

Signaling for inter-frequency HHO from a HSUPA cell to a non-HSUPA cell...168

SHO from a non-HSUPA cell to a HSUPA cell...169

SHO from a non-HSUPA cell to a HSUPA cell (triggered by a 1B event)...169

Intra-frequency HHO from a non-HSUPA cell to a HSUPA cell...170

Signaling for intra-frequency HHO from a non-HSUPA cell to a HSUPA cell...170

Inter-frequency HHO from a non-HSUPA cell to a HSUPA cell...171

Direct retry from an R99 cell to a HSUPA cell...172

Direct retry from a HSUPA cell to an R99 cell...172

Direct retry from a HSUPA cell to another HSUPA cell...173

Switch between HSUPA channel types...173

Signaling flow for handover from WCDMA to GSM...175

Tracing signaling of handover from WCDMA to GSM...175

Signaling flow for handover from GSM to WCDMA...178

Tracing signaling of handover from GSM to WCDMA...179

Flow of handover from WCDMA to GPRS (1)...182

Flow of handover from WCDMA to GPRS (2)...182

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Signaling flow for handover from GPRS to WCDMA (1)...185

Signaling flow for handover from GPRS to WCDMA (2)...186

Data configuration in the location area cell table...192

Data configuration of neighbor cell configuration table...193

Configuration table for external 3G cells...195

Configuration table for GSM inter-RAT neighbor cells...196

Configuration table for 2G reselection parameters...197

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Tables

Handover performance indexes and reference values...15

HSDPA handover performance indexes and reference value...16

HSUPA handover performance indexes and reference value...16

CDR index and reference value...18

SHO failure indexes...35

HHO failure indexes...35

Traffic statistics indexes of CS inter-RAT handover preparation failure...37

Traffic statistics indexes of PS inter-RAT outgoing handover failure...38

Types of CDR indexes...44

Thresholds of EcIo and Ec...45

Traffic statistics indexes for analyzing causes to call drop...50

Relationship between the filter coefficient and the corresponding tracing time...57

2G handover times...62

Best servers and other cells...66

Timers and counters related to the synchronization and asynchronization...103

Timers and counters related to call drop at lub interface...106

Flow of serving cell update triggered by different events in SHO...131

Scenarios of handover between HSDPA and R99 (V17)...143

Handover between two HSUPA cells...157

Handover between a HSUPA cell and a non-HSUPA cell...162

Parameters of handover from 3G to 2G...189

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

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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

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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:

 Traffic Statistics Analysis for HSDPA Handover  Handover Between HSDPA and R99

 Direct Retry of HSDPA  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:

 1Introduction

 2Handover and Call Drop Performance Indexes  3Handover Index Optimization

 4CDR Index Optimization  5FAQs Analysis

 6Summary

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

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2

Handover and Call Drop Performance Indexes

2.1 Handover Performance Indexes

According to RNA KPI baseline document, 2.1 lists the handover performance indexes and reference values.

Table 1.1 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% PS UL64K/DL 144K DT&Stat. 80% PS UL64K/DL 384K DT&Stat. 75% Inter-frequency HHO success rate Voice DT&Stat. 92% VP DT&Stat. 90% PS UL64K/DL 64K DT&Stat. 90% PS UL64K/DL 144K DT&Stat. 87% PS UL64K/DL 384K DT&Stat. 85% Inter-RAT handover success rate

Voice handover out DT&Stat. 95% PS handover out DT&Stat. 92%

SHO ratio N/A DT 35%

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2.1 lists the HSDPA handover performance indexes and reference value.

Table 1.2 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 by WCDMA&GSM Performance Research Department.

Table 1.3 HSUPA handover performance indexes and reference value

Index Service Reference value

Success rate of inter-cell SHO in HSUPA (including adding, replacing, and deleting)

PS (HSUPA) –

Success rate of inter-cell 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)

–

Success rate of inter-cell intra-frequency HHO in

HSUPA PS (HSUPA)

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Index Service Reference value Success rate of

intra-frequency HHO from a HSUPA cell to a non-HSUPA cell

PS (HSUPA)

–

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)

–

Success rate of inter-cell 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 by WCDMA&GSM Performance Department.

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2.2 Call Drop Performance Indexes

2.2 lists the CDR index and reference value.

Table 1.4 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 HSDPA) DT 3% PS Stat. 10% PS (UL HSUPA/DL HSDPA) DT 3%

The values listed in 2.2 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.

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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

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Figure 1.2 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-intra-frequency missing neighbor

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cell.

 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.  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)

 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:

 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:

 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, CPICH_RSCP>ThRSCP_Absolute_.

 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, CPICH_Number>ThN

 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. (ThN +1)_{strong pilot is smaller than a threshold, no best server strong}

enough exists in the point. Namely,

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Based on previous descriptions, pilot pollution exists if all the following conditions are met:

 The number of pilots satisfying CPICH_RSCP>ThRSCP_Absolute is more than N

Th _.



(

C P IC H

_

R S C P

1st

−

C P IC H

_

R S C P

(T hN+1)th

)

<

T h

R S C P_R ela tiv e

SetThRSCP_Absolute =−95dBm,ThN =3, and ThRSCP _Relative =5dB , the judgment standards

for pilot pollution are:

 The number of pilots satisfying CPICH_RSCP>−95dBm is larger than 3. 

(

C P IC H

_

R S C P

1st

−

C P IC H

_

R S C P

4th

)

<

5 d B

Improper Configuration of SHO Algorithm Parameters

Solve the following two problems by adjusting handover algorithm parameters.

 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.

 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.

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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:

 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.

 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.

 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.

 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.

 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:

 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

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handover controlled by PS service rate threshold of handover cell. The 1D event of intra-frequency measurement events determines intra-intra-frequency HHO.

 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.

 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

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Figure 1.1 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:

 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.

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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.

 Increase the CIO of two inter-frequency cells.

 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

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Figure 1.1 Inter-RAT handover CQT flow

Data Configuration

Inter-RAT handover fails due to incomplete configuration data, so pay attention to the following data configuration.

 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)

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 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.

 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:

 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.

 Missing neighbor cell causes call drop.

 The signals fluctuate frequently so call drop occurs.

 Handset problems causes call drop. For example, the UE fails to hand over

back or to report inter-RAT measurement report.

 The best cell changes upon Physical channel reconfiguration.

 Excessive inter-RAT cell are configured (solve it by optimizing number of

neighbor cells).

 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:

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 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:

 Handover in HSDPA system

 Handover between HSDPA and R99 cells  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).

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Figure 1.1 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:

 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.

 Whether the protection time length of HSDPA handover is proper. Now the

baseline value is 0s. Set it by running SET HOCOMM.

 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.

 Whether the protection time length of D2H handover is proper. Now the

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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 1.2 Movement of the MBMS UE between PTM cells

PTM Cell B PTM Cell A PTM Cell B PTM Cell A PTM Cell B PTM Cell A PTM Cell B PTM Cell A

Step1: UE uses PTM RB to receive MBMS from Cell A only

Step2: UE uses PTM RB to receive MBMS from A and B

Step3 : UE re-selects to Cell B but still receive MBMS from Cell A and B

Step4 : Far from Cell A, UE uses PTM RB to receive MBMS from Cell B only

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

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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:

 Optimize cell reselection parameters to guarantee that the UE can be

reselected to the best cell in time.

 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.

 Guarantee that the transmission time difference of the UE between different

links meets the requirement of soft combing or selective combining*.

 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

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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.

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Figure 1.3 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.

 Check the SHO success rate of entire network and cell in busy hour. If they

are not qualified, analyze the problematic cells in details.

 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.

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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.

 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:

 Outgoing HHO Success Rate = Outgoing HHO Success Times/Outgoing

HHO Times

 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.

3.2.2 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.

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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.

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Figure 1.1 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 3.2.3.

Table 1.1 Traffic statistics indexes of CS inter-RAT handover preparation failure

Failure cause Analysis

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:

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.

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.

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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 3.2.3.

Table 1.1 Traffic statistics indexes of PS inter-RAT outgoing handover failure

Failure cause Analysis

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

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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

 H-H (HS-DSCH to HS-DSCH) intra-frequency serving cell update  H-H inter-frequency serving cell update

 HSDPA-R99 intra-frequency switch  HSDPA-R99 inter-frequency switch  HSDPA-GPRS switch

The traffic statistics indexes are defined as below:

 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.

 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.

 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.

 Success rate of H-to-R99 intra-frequency SHO = successful times of switch

from 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.

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 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.

When the RNC sends the UE the PHYSICAL CHANNEL RECONFIGURATION 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.

 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

When the RNC sends the UE the PHYSICAL CHANNEL RECONFIGURATION 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.

 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 DSCH in the same cell, the RNC counts the successful times of switch from DCH to HS-DSCH in the HSDPA serving cell.

 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:

 Success rate of SHO between HSUPA cells (including adding, replacing,

and deleting) = attempt times of active set update/complete times of active set update.

 Success rate of SHO serving cell update between HSUPA cells =

successful times of SHO serving cell update/attempt times of SHO serving cell update.

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 Success rate of reconfiguration from DCH to E-DCH in the cell (SHO,

intra-frequency HHO, and inter-intra-frequency HHO) = successful times of handover from DCH to E-DCH/attempt times of handover from DCH to E-DCH.

 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.

 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.

 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.

 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.

 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.

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3.3 SHO Cost Optimization

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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:

 Any BCH message (system information)

 The RRC Release message with the release cause Not Normal.

 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:

 After the service is set up, the RNC sends CN the RAB RELEASE

REQUEST message.

 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:

%

*

Success

CSRABSetup

iggedByRNC

CSRabrelTr

CDR

CS

_

100 ∑

∑

=

PS CDR is calculated as below:

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%

*

Success

PSRABSetup

iggedByRNC

PSRabrelTr

CDR

PS

_

100 ∑

∑

=

The failure cause indexes are sorted in 4.1.2.

Table 1.2 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 force by MML O&M intervention

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

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Figure 1.2 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.

4.2.1 lists the thresholds of Ec/Io and Ec (from an RNP result of an operator, just for reference).

Table 1.1 Thresholds of EcIo and Ec

Service Bit rate of _service DL EbNo _thresholdsEcIo Ec thresholds

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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.

 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.

 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:

 Lack of NodeBs

 Incorrectly configured sectors

 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.

W-Handover and Call Drop Problem Optimization Guide-20081223-A-3.3

W-Handover and Call Drop Problem Optimization

Guide

(For internal use only)

Huawei Technologies Co., Ltd.

All Rights Reserved

Revision Records

Contents

Figures

Tables

W-Handover and Call Drop Problem Optimization Guide

Key words:

Abstract:

Acronyms and abbreviations:

1

Introduction

2

Handover and Call Drop Performance Indexes

2.1

Handover Performance Indexes

2.2

Call Drop Performance Indexes

3

Handover Index Optimization

3.1

DT/CQT Index Optimization Flow

3.1.1

SHO DT Index Optimization Flow

Inputting Analysis Data

Obtaining When and Where the Problem Occurs

Missing Neighbor Cell

Pilot Pollution

(

C P IC H

_

R S C P

−

C P IC H

_

R S C P

)

<

T h

(

C P IC H

_

R S C P

−

C P IC H

_

R S C P

)

<

5

d B

Improper Configuration of SHO Algorithm Parameters

Abnormal Equipment

Reperforming Drive Test and Locating Problems

Adjustment and Implementation

3.1.2

HHO CQT Flow

HHO Types

Optimization Flow of HHO CQT

Adjustment

3.1.3

Inter-RAT Handover CQT Flow

Flow Chat

Data Configuration

Causes

3.1.4

DT/CQT Flow for HSDPA Handover

Type

Methods

Flow

3.1.5

DT/CQT Flow for HSUPA Handover

3.1.6

SHO Ratio Optimization

3.1.7

MBMS Mobility Optimization