CS Fallback(eRAN8.1_03).pdf

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eRAN

CS Fallback Feature Parameter

Description

Issue 03

Date 2015-08-31

HUAWEI TECHNOLOGIES CO., LTD.


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Copyright Huawei Technologies Co., Ltd. 2015. All rights reserved.

No part of this document may be reproduced or transmitted in any form or by any means without prior written

consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

All other trademarks and trade names mentioned in this document are the property of their respective

holders.

Notice

The purchased products, services and features are stipulated by the contract made between Huawei and the

customer. All or part of the products, services and features described in this document may not be within thepurchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information,

and recommendations in this document are provided "AS IS" without warranties, guarantees or

representations of any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in the

preparation of this document to ensure accuracy of the contents, but all statements, information, and

recommendations in this document do not constitute a warranty of any kind, express or implied.

Huawei Technologies Co., Ltd.

Address: Huawei Industrial Base

Bantian, Longgang

Shenzhen 518129

People's Republic of China

Website: http://www.huawei.com

Email: [email protected]

Issue 03 (2015-08-31) Huawei Proprietary and Confidential

Copyright Huawei Technologies Co., Ltd.

i
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Contents

1 About This Document.................................................................................................................. 1

1.1 Scope.............................................................................................................................................................................. 1

1.2 Intended Audience..........................................................................................................................................................2

1.3 Change History...............................................................................................................................................................2

1.4 Differences Between eNodeB Types..............................................................................................................................5

2 Overview......................................................................................................................................... 6

2.1 Overview........................................................................................................................................................................ 7

2.2 Benefits...........................................................................................................................................................................7

2.3 Architecture.................................................................................................................................................................... 7

2.4 CSFB Mechanisms....................................................................................................................................................... 10

2.4.1 CSFB toUTRAN.......................................................................................................................................................10

2.4.2 CSFB toGERAN.......................................................................................................................................................11

3 CSFB to UTRAN.......................................................................................................................... 143.1 Overview...................................................................................................................................................................... 15

3.2 Feature Classification................................................................................................................................................... 16

3.2.1 Basic CSFB to UTRAN.............................................................................................................................................16

3.2.2 Flash CSFB to UTRAN.............................................................................................................................................16

3.2.3 Ultra-Flash CSFB to UTRAN................................................................................................................................... 16

3.2.4 CS Fallback with LAI to UTRAN.............................................................................................................................17

3.2.5 E-UTRAN to UTRAN CS Steering...........................................................................................................................18

3.2.6 CS Fallback Steering to UTRAN.............................................................................................................................. 19

3.2.7 Load-based CSFB to UTRAN...................................................................................................................................21

3.3 TriggeringEvents......................................................................................................................................................... 21

3.4 Target Cell/Frequency Selection...................................................................................................................................22

3.5 Handover Decision....................................................................................................................................................... 27

3.5.1 Basic Handover Decision.......................................................................................................................................... 27

3.5.2 Flash Redirection Decision........................................................................................................................................28

3.6 Handover Execution..................................................................................................................................................... 29

3.6.1 Handover Policy Selection........................................................................................................................................ 29

3.6.2 Ultra-Flash CSFB to UTRAN................................................................................................................................... 31

3.6.3 Redirection-based CSFB Optimization for UEs in Idle Mode..................................................................................33

3.6.4 CSFB Admission Optimization for UEs in Idle Mode..............................................................................................33

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3.7 RIM Procedure Between E-UTRAN and UTRAN...................................................................................................... 34

3.7.1 RIM Procedure Through the Core Network..............................................................................................................35

3.7.2 RIM Procedure Through the eCoordinator................................................................................................................36

4 CSFB to GERAN.......................................................................................................................... 384.1 Overview...................................................................................................................................................................... 39

4.2 Feature Classification................................................................................................................................................... 39

4.2.1 Basic CSFB to GERAN.............................................................................................................................................39

4.2.2 Flash CSFB to GERAN.............................................................................................................................................40

4.2.3 CS Fallback with LAI to GERAN.............................................................................................................................40

4.2.4 CS Fallback Steering to GERAN.............................................................................................................................. 40

4.2.5 Ultra-Flash CSFB to GERAN................................................................................................................................... 41

4.3 TriggeringEvents......................................................................................................................................................... 42

4.4 Target Cell/Frequency Selection...................................................................................................................................42

4.5 Handover Decision....................................................................................................................................................... 43

4.6 Handover Execution..................................................................................................................................................... 43

4.7 RIM Procedure Between E-UTRAN and GERAN...................................................................................................... 45

5 Related Features...........................................................................................................................47

5.1 Features Related to LOFD-001033 CS Fallback to UTRAN.......................................................................................47

5.2 Features Related to LOFD-001052 Flash CS Fallback to UTRAN............................................................................. 47

5.3 Features Related to LOFD-070202 Ultra-Flash CSFB to UTRAN..............................................................................48

5.4 Features Related to LOFD-001068 CS Fallback with LAI to UTRAN....................................................................... 48

5.5 Features Related to LOFD-001088 CS Fallback Steering to UTRAN.........................................................................49

5.6 Features Related to LOFD-001078 E-UTRAN to UTRAN CS/PS Steering............................................................... 49

5.7 Features Related to LOFD-001034 CS Fallback to GERAN.......................................................................................50

5.8 Features Related to LOFD-001053 Flash CS Fallback to GERAN............................................................................. 50

5.9 Feature Related to LOFD-081283 Ultra-Flash CSFB to GERAN............................................................................... 51

5.10 Features Related to LOFD-001069 CS Fallback with LAI to GERAN..................................................................... 51

5.11 Features Related to LOFD-001089 CS Fallback Steering to GERAN.......................................................................51

6 NetworkImpact........................................................................................................................... 53

6.1 LOFD-001033 CS Fallback to UTRAN.......................................................................................................................53

6.2 LOFD-001052 Flash CS Fallback to UTRAN............................................................................................................. 54

6.3 LOFD-070202 Ultra-Flash CSFB to UTRAN..............................................................................................................54

6.4 LOFD-001068 CS Fallback with LAI to UTRAN....................................................................................................... 55

6.5 LOFD-001088 CS Fallback Steering to UTRAN.........................................................................................................55

6.6 LOFD-001078 E-UTRAN to UTRAN CS/PS Steering............................................................................................... 55

6.7 LOFD-001034 CS Fallback to GERAN.......................................................................................................................56

6.8 LOFD-001053 Flash CS Fallback to GERAN............................................................................................................. 56

6.9 LOFD-081283 Ultra-Flash CSFB to GERAN..............................................................................................................57

6.10 LOFD-001069 CS Fallback with LAI to GERAN..................................................................................................... 57

6.11 LOFD-001089 CS Fallback Steering to GERAN.......................................................................................................57

7 Engineering Guidelines............................................................................................................. 59

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7.1 LOFD-001033 CS Fallback to UTRAN.......................................................................................................................59

7.1.1 When to Use CS Fallback to UTRAN.......................................................................................................................59

7.1.2 Required Information................................................................................................................................................ 59

7.1.3 Requirements.............................................................................................................................................................60

7.1.4 Precautions.................................................................................................................................................................61

7.1.5 Data Preparation and Feature Activation...................................................................................................................61

7.1.5.1 Data Preparation..................................................................................................................................................... 61

7.1.5.2 Using the CME to Perform Batch Configuration for Newly Deployed eNodeBs..................................................66

7.1.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs............................................................... 67

7.1.5.4 Using the CME to Perform Single Configuration.................................................................................................. 68

7.1.5.5 Using MML Commands.........................................................................................................................................69

7.1.6 Activation Observation..............................................................................................................................................72

7.1.7 Deactivation...............................................................................................................................................................78

7.1.8 Performance Monitoring............................................................................................................................................79

7.1.9 Parameter Optimization.............................................................................................................................................80

7.2 RIM Procedure from E-UTRAN to UTRAN............................................................................................................... 84

7.2.1 When toUse RIM Procedure from E-UTRAN to UTRAN...................................................................................... 84


7.2.3 Requirements.............................................................................................................................................................84

7.2.4 Precautions.................................................................................................................................................................85



7.2.5.2 Using the CME to Perform Batch Configuration for Newly Deployed eNodeBs..................................................867.2.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs............................................................... 86



7.2.6 Activation Observation..............................................................................................................................................88

7.2.7 Deactivation...............................................................................................................................................................89

7.2.8 Performance Monitoring............................................................................................................................................90

7.2.9 Parameter Optimization.............................................................................................................................................90

7.3 LOFD-001052 Flash CS Fallback to UTRAN............................................................................................................. 90

7.3.1 When toUse Flash CS Fallback to UTRAN............................................................................................................. 91


7.3.3 Requirements.............................................................................................................................................................92

7.3.4 Precautions.................................................................................................................................................................92



7.3.5.2 Using the CME to Perform Batch Configuration for Newly Deployed eNodeBs..................................................96

7.3.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs............................................................... 98



7.3.6 Activation Observation............................................................................................................................................100

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7.3.7 Deactivation.............................................................................................................................................................101

7.3.8 Performance Monitoring..........................................................................................................................................102

7.3.9 Parameter Optimization...........................................................................................................................................102

7.4 LOFD-070202 Ultra-Flash CSFB to UTRAN............................................................................................................102

7.4.1 When to Use Ultra-Flash CSFB.............................................................................................................................. 102

7.4.2 Required Information.............................................................................................................................................. 102

7.4.3 Requirements...........................................................................................................................................................102

7.4.4 Precautions...............................................................................................................................................................103

7.4.5 Data Preparation and Feature Activation.................................................................................................................103

7.4.5.1 Data Preparation................................................................................................................................................... 103

7.4.5.2 Using the CME to Perform Batch Configuration for Newly Deployed eNodeBs................................................105

7.4.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs............................................................. 106

7.4.5.4 Using the CME to Perform Single Configuration................................................................................................ 107

7.4.5.5 Using MML Commands.......................................................................................................................................108


7.4.7 Deactivation.............................................................................................................................................................112


7.4.9 Parameter Optimization........................................................................................................................................... 113

7.5 LOFD-001068 CS Fallback with LAI to UTRAN..................................................................................................... 113

7.5.1 When toUse CS Fallback with LAI to UTRAN..................................................................................................... 113

7.5.2 Required Information...............................................................................................................................................113

7.5.3 Requirements........................................................................................................................................................... 114

7.5.4 Precautions...............................................................................................................................................................1157.5.5 Data Preparation and Feature Activation.................................................................................................................115



7.5.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs..............................................................115


7.5.5.5 Using MML Commands....................................................................................................................................... 115

7.5.6 Activation Observation............................................................................................................................................ 115

7.5.7 Deactivation.............................................................................................................................................................116


7.5.9 Parameter Optimization........................................................................................................................................... 116

7.6 LOFD-001088 CS Fallback Steering to UTRAN.......................................................................................................116

7.6.1 When toUse CS Fallback Steering to UTRAN.......................................................................................................117

7.6.2 Required Information...............................................................................................................................................117

7.6.3 Requirements........................................................................................................................................................... 117

7.6.4 Precautions...............................................................................................................................................................118





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7.6.7 Deactivation.............................................................................................................................................................126



7.7 LOFD-001078 E-UTRAN to UTRAN CS/PS Steering............................................................................................. 127

7.7.1 When toUse E-UTRAN to UTRAN CS/PS Steering............................................................................................. 127


7.7.3 Requirements...........................................................................................................................................................128

7.7.4 Precautions...............................................................................................................................................................128








7.7.7 Deactivation.............................................................................................................................................................133



7.8 LOFD-001034 CS Fallback to GERAN.....................................................................................................................134

7.8.1 When toUse CS Fallback to GERAN.....................................................................................................................1347.8.2 Required Information.............................................................................................................................................. 134

7.8.3 Requirements...........................................................................................................................................................135

7.8.4 Precautions...............................................................................................................................................................136






7.8.5.5 Using Feature Operation and Maintenance on the CME......................................................................................143



7.8.7 Deactivation.............................................................................................................................................................155



7.9 RIM Procedure from E-UTRAN to GERAN............................................................................................................. 158

7.9.1 When toUse RIM Procedure Between E-UTRAN and GERAN............................................................................159


7.9.3 Requirements...........................................................................................................................................................159

7.9.4 Precautions...............................................................................................................................................................160

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7.9.7 Deactivation.............................................................................................................................................................164



7.10 LOFD-001053 Flash CS Fallback to GERAN......................................................................................................... 165

7.10.1 When to Use Flash CS Fallback to GERAN......................................................................................................... 165

7.10.2 Required Information............................................................................................................................................ 166

7.10.3 Requirements.........................................................................................................................................................166

7.10.4 Precautions.............................................................................................................................................................167

7.10.5 Data Preparation and Feature Activation...............................................................................................................167

7.10.5.1 Data Preparation................................................................................................................................................. 167

7.10.5.2 Using the CME to Perform Batch Configuration for Newly Deployed eNodeBs..............................................171

7.10.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs........................................................... 173

7.10.5.4 Using the CME to Perform Single Configuration.............................................................................................. 174

7.10.5.5 Using MML Commands.....................................................................................................................................174

7.10.6 Activation Observation..........................................................................................................................................175

7.10.7 Deactivation...........................................................................................................................................................1767.10.8 Performance Monitoring........................................................................................................................................177

7.10.9 Parameter Optimization.........................................................................................................................................177

7.11 LOFD-081283 Ultra-Flash CSFB to GERAN..........................................................................................................177

7.11.1 When to Use This Feature..................................................................................................................................... 177

7.11.2 Required Information.............................................................................................................................................177

7.11.3 Requirements......................................................................................................................................................... 178

7.11.4 Precautions.............................................................................................................................................................178




7.11.5.3 Using the CME to Perform Batch Configuration for Existing eNodeBs............................................................183




7.11.7 Deactivation...........................................................................................................................................................186

7.11.8 Performance Monitoring........................................................................................................................................187


7.12 LOFD-001069 CS Fallback with LAI to GERAN................................................................................................... 188

7.12.1 When to Use CS Fallback with LAI to GERAN...................................................................................................188

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7.12.3 Requirements.........................................................................................................................................................189

7.12.4 Precautions.............................................................................................................................................................190








7.12.7 Deactivation...........................................................................................................................................................191



7.13 LOFD-001089 CS Fallback Steering to GERAN.....................................................................................................191

7.13.1 When to Use CS Fallback Steering to GERAN.................................................................................................... 191


7.13.3 Requirements.........................................................................................................................................................192

7.13.4 Precautions.............................................................................................................................................................192





7.13.5.4 Using the CME to Perform Single Configuration.............................................................................................. 1987.13.5.5 Using MML Commands.....................................................................................................................................198


7.13.7 Deactivation...........................................................................................................................................................199



7.14 Troubleshooting........................................................................................................................................................200

7.14.1 CSFB Calling Procedure Failure........................................................................................................................... 200

7.14.2 eNodeB Receiving No Measurement Report........................................................................................................ 201

7.14.3 CSFB Blind Handover Failure.............................................................................................................................. 201

7.14.4 CSFB Handover Failure........................................................................................................................................ 202

8 Parameters...................................................................................................................................204

9 Counters...................................................................................................................................... 254

10 Glossary.....................................................................................................................................313

11 Reference Documents.............................................................................................................314

12 Appendix...................................................................................................................................315

12.1 CSFB to UTRAN......................................................................................................................................................315

12.1.1 Combined EPS/IMSI Attach Procedure................................................................................................................ 315

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12.1.2 CSFB Based on PS Handover............................................................................................................................... 316

12.1.3 Signaling procedure of redirection to CDMA2000 1xRTT...................................................................................318

12.1.4 Flash CSFB............................................................................................................................................................320

12.1.5 Ultra-Flash CSFB to UTRAN............................................................................................................................... 321

12.1.6 Redirection-based CSFB Optimization for UEs in Idle Mode..............................................................................323

12.1.7 CSFB for SMS.......................................................................................................................................................324

12.1.8 Emergency Call..................................................................................................................................................... 324

12.1.9 CSFB for LCS....................................................................................................................................................... 325

12.2 CSFB to GERAN......................................................................................................................................................325

12.2.1 Combined EPS/IMSI Attach Procedure................................................................................................................ 325

12.2.2 CSFB Based on PS Handover............................................................................................................................... 325

12.2.3 CSFB Based on CCO/NACC................................................................................................................................ 327

12.2.4 CSFB Based on Redirection..................................................................................................................................328

12.2.5 Flash CSFB............................................................................................................................................................330

12.2.6 Ultra-Flash CSFB to GERAN............................................................................................................................... 331

12.2.7 CSFB for SMS.......................................................................................................................................................334

12.2.8 Emergency Call..................................................................................................................................................... 334

12.2.9 CSFB for LCS....................................................................................................................................................... 334

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1About This Document

1.1 Scope

This document describes circuit switched fallback (CSFB), including its technical principles,

related features, network impact, and engineering guidelines.

This document covers the following features:

l LOFD-001033 CS Fallback to UTRAN

l LOFD-001052 Flash CS Fallback to UTRAN

l LOFD-070202 Ultra-Flash CSFB to UTRAN

l

LOFD-001068 CS Fallback with LAI to UTRANl LOFD-001088 CS Fallback Steering to UTRAN

l LOFD-001078 E-UTRAN to UTRAN CS/PS Steering

l LOFD-001034 CS Fallback to GERAN

l LOFD-001053 Flash CS Fallback to GERAN

l LOFD-001069 CS Fallback with LAI to GERAN

l LOFD-001089 CS Fallback Steering to GERAN

l LOFD-081283 Ultra-Flash CSFB to GERAN

If Huawei devices are used in the GERAN or UTRAN to which CS fallback is performed,

refer to the following documents to obtain details about CSFB implementation in thecorresponding network:

l GERAN: CS Fallback Feature Parameter Descriptionin GBSS Feature Documentation.

l UTRAN:Interoperability Between UMTS and LTE Feature Parameter Descriptionin

RAN Feature Documentation.

Any managed objects (MOs), parameters, alarms, or counters described herein correspond to

the software release delivered with this document. Any future updates will be described in the

product documentation delivered with future software releases.

This document applies only to LTE FDD. Any "LTE" in this document refers to LTE FDD,

and "eNodeB" refers to LTE FDD eNodeB.

This document applies to the following types of eNodeBs.

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ChangeType

Change Description Parameter Change AffectedEntity

Feature

change

Added the measurement-specific

DRX configuration for Ultra-Flash

CSFB to GERAN. For details, see

4.2.5 Ultra-Flash CSFB to

GERAN.

None Macro,

micro, and

LampSite

eNodeBs

Added the random selection

optimization switch for CSFB. For

details, see 3.4 Target Cell/

Frequency Selectionand 7.1.5.1

Data Preparation.

Added the

RsvdSwPara1_bit23

option in the reserved

parameter

eNBRsvdPara.

RsvdSwPara1.

Macro,

micro, and

LampSite

eNodeBs

Editorial

change

None None -

eRAN8.1 01 (2015-03-23)

This issue includes the following changes.

Change Type Change Description ParameterChange

Affected Entity

Feature change Added the UE compatibility

risk optimization for ultra-flashCSFB. For details, see 7.11.5.1

Data Preparation.

Added the

UltraFlashCsfbComOptSwoption

to the

GlobalProcSwitc

h.UeCompatSwitc

hparameter.

Macro, micro,

and LampSiteeNodeBs

Editorial

change

None None -

eRAN8.1 Draft A (2015-01-15)

Compared with Issue 06 (2014-12-30) of eRAN7.0, Draft A (2015-01-15) of eRAN8.1

includes the following changes.

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Change Type

Change Description ParameterChange

AffectedEntity

Feature

change

Supported the cell-level blind handling switch for

CSFB in CS Fallback to UTRAN or GERAN and

Flash CS Fallback to UTRAN or GERAN

scenarios.

l For details about the switch, see 3.2.1 Basic

CSFB to UTRANand 3.4 Target Cell/

Frequency Selection.

l For details about handover policy selection,

see 3.6.1 Handover Policy Selection.

l For details about scenario-specific parameter

preparations, see section "Data Preparation" in

engineering guidelines.

l For details about scenario-specificconfigurations, see "Using the CME to

Perform Batch Configuration for Newly

Deployed eNodeBs" and "Using MML

Commands" in section "Activation" in

engineering guidelines.

Added the

CellHoParaCf

g.HoModeSwit

chparameter.

Macro,

micro,

and

LampSite

eNodeBs

Added the feature LOFD-081283 Ultra-Flash

CSFB to GERAN.

l For details about the feature description, see

4.2.5 Ultra-Flash CSFB to GERAN.

l For details about the signaling procedure, see

12.2.6 Ultra-Flash CSFB to GERAN.

l For details about related features and network

impact, see 5.9 Feature Related to

LOFD-081283 Ultra-Flash CSFB to

GERANand 6.9 LOFD-081283 Ultra-Flash

CSFB to GERAN.

l For details about engineering guidelines, see

7.11 LOFD-081283 Ultra-Flash CSFB to

GERAN.

l Added the

GeranExte

rnalCell.Ul

traFlashCs

fbInd

parameter.l Added the

GeranUltr

aFlashCsfb

Switch

option in

the

ENodeBAl

goSwitch.

HoAlgoSwi

tch

parameter.

Macro,

micro,

and

LampSite

eNodeBs

Added the configuration of the round-robin

function for L2U blind redirections.

l For details about the switch, see 3.4 Target

Cell/Frequency Selection.

l For details about scenario-specific data

preparations, see 7.1.5.1 Data Preparation.

l For details about the function activation, see

7.1.5.5 Using MML Commands.

Added the

CSFallBackBl

indHoCfg.Utr

anCsfbBlindR

edirRrSw

parameter.

Macro,

micro,

and

LampSite

eNodeBs

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Change Type

Change Description ParameterChange

AffectedEntity

Added SPID-based mobility management. For

details about the function, see 3.4 Target Cell/

Frequency Selection, 3.5.1 Basic Handover

Decision, and 3.5.2 Flash Redirection Decision.

None Macro,

micro,

and

LampSite

eNodeBs

Ultra-flash CSFB to GERAN uses the DRX-

based measurement, which is controlled by the

CellDrxPara.DrxForMeasSwitchparameter.

l For details about the parameter, see 4.2.5

Ultra-Flash CSFB to GERAN.

l For details about data preparations and MML

configurations, see related sections in 7.11

LOFD-081283 Ultra-Flash CSFB toGERAN.

Added the

CellDrxPara.

DrxForMeasS

witch

parameter.

Macro,

micro,

and

LampSite

eNodeBs

Editoria

l change

Changed "blind handling" to "blind handover".

For details, see descriptions of blind handover in

this document.

None -

1.4 Differences Between eNodeB Types

The features described in this document are implemented in the same way on macro, micro,

and LampSite eNodeBs.

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2OverviewIn an early phase of EPS construction, operators who own a mature UTRAN or GERAN can

protect their investments in legacy CS networks and reduce their investments in the EPS by

using legacy CS networks to provide CS services.

Currently, CSFB and voice over IP (VoIP) over IP multimedia subsystem (IMS) are the two

standard solutions to provide voice services for E-UTRAN UEs. After the technological

maturity, industry chain, and deployment costs of the two methods are well weighed, CSFB is

chosen to serve as an interim solution for voice service access before mature commercial use

of IMS.

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2.1 Overview

With the CSFB solution, when a UE initiates a CS service, the mobility management entity

(MME) instructs the UE to fall back to the legacy CS network before the UE performs the

service. CSFB is a session setup procedure. UEs fall back to CS networks before CS sessions

are set up, and they always stay in the CS networks during the CS sessions. For details, see

3GPP TS 23.272 V8.5.0.

The eNodeB handles the CSFB for different types of CS services in a uniform way such as the

voice service, SMS, LCS, and emergency calls.

2.2 Benefits

CSFB brings the following benefits:

l Facilitates voice services for the LTE network.

l Helps operators reduce costs by reusing legacy CS networks and not deploying an IMS

network.

2.3 Architecture

CSFB is applicable to scenarios where the CS network of the UTRAN/GERAN has the same

or larger coverage area than that of the E-UTRAN.

Figure 2-1shows the network architecture for CSFB to UTRAN/GERAN.

Figure 2-1Network architecture for CSFB to UTRAN/GERAN

Table 2-1describes the elements of the network architecture in Figure 2-1.

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Table 2-1Elements of the network architecture for CSFB to UTRAN/GERAN

NE Function

SGs interface l Is an interface between the MME and the MSC server.

l Assists mobility management and paging between the EPS and theCS network.

l Transmits mobile originated (MO) and mobile terminated (MT)

SMS messages.

l Transmits messages related to combined attach and combined TAU/

LAU.

UE l Is capable of accessing the EPS and accessing the UTRAN,

GERAN, or both.

l Supports combined EPS/IMSI (IMSI is short for international

mobile subscriber identity) attach, combined EPS/IMSI detach, and

combined TAU/LAU.

l Supports CSFB mechanisms, such as PS redirection and PS

handover.

NOTE

CSFB-capable UEs must support SMS over SGs, but UEs that support SMS over

SGs are not necessarily CSFB-capable.

MME l Supports the SGs interface to the MSC/VLR.

l Selects the VLR and location area identity (LAI) based on the

tracking area identity (TAI) of the serving cell.

l Forwards paging messages delivered by the MSC.

l Performs public land mobile network (PLMN) selection andreselection.

l Supports combined EPS/IMSI attach, combined EPS/IMSI detach,

and combined TAU/LAU.

l Routes CS signaling.

l Supports SMS over SGs.

l Supports RIM, which is required when flash CSFB or CCO with

NACC is used as the CSFB mechanism. (CCO is short for cell

change order and NACC is short for network assisted cell change.)

MSC l Supports combined EPS/IMSI attach.

l Supports SMS over SGs.

l Forwards paging messages transmitted through the SGs interface.

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NE Function

E-UTRAN l Forwards paging messages related to CSFB.

l Selects target cells for CSFB for E-UTRAN UEs.

l Supports one or more of the following functions:

PS redirection to UTRAN or GERAN, if PS redirection is used

as the CSFB mechanism.

PS handover to UTRAN or GERAN, if PS handover is used as

the CSFB mechanism.

CCO without NACC to GERAN, if CCO without NACC is used

as the CSFB mechanism; RIM for acquiring the system

information of GERAN cells, if NACC is used as the CSFB

mechanism.

RIM for acquiring the system information of UTRAN or

GERAN cells, in addition to PS redirection, if flash CSFB isused as the CSFB mechanism.

UTRAN/

GERAN

Supports one or more of the following functions:

l Incoming handovers from the E-UTRAN, if PS handover is used as

the CSFB mechanism.

l RIM for delivering the system information of GERAN cells to

eNodeBs, if CCO with NACC is used as the CSFB mechanism.

l RIM for delivering the system information of UTRAN or GERAN

cells to eNodeBs, in addition to PS redirection, if flash CSFB is

used as the CSFB mechanism.

NOTEThe UTRAN and GERAN do not need to provide extra functions to support PSredirection. The GERAN does not need to provide extra functions to support

CCO without NACC.

SGSN l Supports the follow-up procedures performed for the PS handover,

including data forwarding, path switching, RAU, and encryption

and authentication.

l Supports RIM, which is required when flash CSFB or CCO with

NACC is used as the CSFB mechanism.

eCoordinator Is a network element provided by Huawei, and is optional. The

eCoordinator supports the RIM procedure.

To implement CSFB to provide CS services for UEs on the E-UTRAN, all mobile switching

centers (MSCs) that serve overlapping areas with the E-UTRAN coverage must be upgraded

to support functions involving the SGs interface. The SGs interface is between an MSC and a

mobility management entity (MME), and functions involving the SGs interface include

combined attach, combined TAU/LAU (TAU is short for tracking area update, and LAU is

short for location area update), paging, and SMS. If the live network uses an MSC pool, only

one or multiple MSCs in the MSC pool need to be upgraded to support the SGs interface.

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2.4 CSFB Mechanisms

2.4.1 CSFB to UTRAN

Based on the capabilities of UEs and networks, three fallback mechanisms are available for an

eNodeB to perform CSFB to UTRAN:

l R8 PS Redirection

After receiving a CS Fallback Indicator, the eNodeB sends an RRC Connection Release

message containing frequency information about the target UTRAN to the UE. Based on the

received frequency information, the UE searches for a UTRAN cell, obtains the system

information of the UTRAN cell, and initiates initial access and CS services.

l R9 PS Redirection (Flash CSFB)

After receiving a CS Fallback Indicator, the eNodeB sends an RRC Connection Release

message containing information about a target UTRAN frequency as well as system

information about multiple target cells to the UE. Based on the received frequency

information, the UE searches for a UTRAN cell. As the UE obtains system information about

the target cell, the UE initiates initial access and CS services in the target cell, thereby

reducing voice delay.

l PS Handover

The UE is handed over to the UMTS network through the PS handover procedure between the

eNodeB and the UMTSnetwork. After the handover, the UE initiates CS services in the targetcell.

Table 2-2describes the requirements of the three CSFB mechanisms on the network side and

UEs.

Table 2-2Requirements of CSFB to UTRAN on the network side and UEs

NE R8 PS Redirection R9 Redirection (FlashCSFB)

PS Handover

UE l Support combined

EPS/CS attach andcombined TA/LA

update.

l Support CSFB by R8

PS Redirection.

l Support R9 PS

Redirection with SIB.l The other

requirements are the

same as those of R8

PS Redirection.

l Support PS

Handover.l The other

requirements are

the same as those

of R8 PS

Redirection.

eNodeB Support CSFB by R8 PS

Redirection.

l Support the RIM

procedure.

l The other


same as those of R8

PS Redirection.

Support PS Handover.

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NE R8 PS Redirection R9 Redirection (FlashCSFB)

PS Handover

UTRAN N/A Support the RIM

procedure.


MME l Support combined

EPS/CS attach and

combined TA/LA

update.

l Support the CSFB

procedure.

l Support the RIM

procedure.

l The other


same as those of R8

PS Redirection.


SGSN N/A Support the RIM

procedure.


MSC l Support combined

EPS/CS attach andcombined TA/LA

update.

l Support the CSFB

procedure.

The requirements are the

same as those of R8 PSRedirection.

The requirements are

the same as those ofR8 PS Redirection.

2.4.2 CSFB to GERAN

Based on the capabilities of UEs and networks, five fallback mechanisms are available for an

eNodeB to perform CSFB toGERAN:l R8 PS Redirection

For details, see 2.4.1 CSFB to UTRAN.

l R9 PS Redirection (Flash CSFB)


l CCO

After receiving a CS Fallback Indicator, the eNodeB sends aMobilityFromEUTRACommand

message containing information about a target GERAN cell to the UE, and instructs the UE to

access the target cell. The UE needs to be synchronized to the specified cell, obtains system

information about the target cell, and accesses the cell to initiate CS services.

l CCO with NACC

When the LTE-to-GSM RIM procedure is enabled, which indicates that NACC is enabled, the

eNodeB delivers system information about the target cell when triggering CCO. The UE

directly initiates access and a CS service to the target cell and does not need to read system

information about the target cell, shortening delays.

l PS Handover


Table 2-3describes the requirements of the five CSFB mechanisms on the network side andUEs.

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Table 2-3Requirements of CSFB to GERAN on the network side and UEs

NE R8 PSRedirection

R9 Redirection(Flash CSFB)

CCO CCO withNACC

PSHandover

UE l Supportcombined

EPS/CS

attach and

combined

TA/LA

update.

l Support

CSFB by

R8 PS

Redirection.

lSupport R9PS

Redirection

with SIB.

l The other

requirements

are the same

as those of

R8 PS

Redirection.

lSupportCCO.

l The

other

require

ments

are the

same as

those of

R8 PS

Redirect

ion.

lSupportNACC

l The

other

requirem

ents are

the same

as those

of R8 PS

Redirecti

on.

lSupportPS

handove

r.

l The

other

require

ments

are the

same as

those of

R8 PS

Redirect

ion.

eNodeB Support CSFB

by R8 PS

Redirection.

l Support the

RIM

procedure.

l The other

requirements

are the same

as those of

R8 PS

Redirection.

Support

CCO.

l Support

the RIM

procedur

e.

l The

other

requirem

ents are

the same

as those

of R8 PS

Redirecti

on.

Support PS

Handover.

GERAN N/A Support the RIM

procedure.

N/A Support the

RIM

procedure.

Support PS

Handover.

MME l Support

combined

EPS/CS

attach andcombined

TA/LA

update.

l Support the

CSFB

procedure.

l Support the

RIM

procedure.

l The other

requirements

are the same

as those of

R8 PS

Redirection.

The

requiremen

ts are the

same asthose of R8

PS

Redirection

.

l Support

the RIM

procedur

e.

l The

other

requirem

ents are

the same

as those

of R8 PS

Redirecti

on.

Support PS

Handover.

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NE R8 PSRedirection

R9 Redirection(Flash CSFB)

CCO CCO withNACC

PSHandover

SGSN N/A Support the RIM

procedure.

N/A Support the

RIM

procedure.

Support PS

Handover.

MSC l Support

combined

EPS/CS

attach and

combined

TA/LA

update.

l Support the

CSFB

procedure.

The

requirements are

the same as

those of R8 PS

Redirection.

The

requiremen

ts are the

same as

those of R8

PS

Redirection

.

The

requirement

s are the

same as

those of R8

PS

Redirection.

The

requiremen

ts are the

same as

those of R8

PS

Redirection

.

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3CSFB to UTRANThis chapter describes each CSFB to UTRAN feature, CSFB procedure, and RIM procedure

between E-UTRAN and UTRAN.

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3.1 Overview

CSFB to UTRAN can be implemented in different ways and includes the following features/

functions:

l LOFD-001033 CS Fallback to UTRAN

l LOFD-001052 Flash CS Fallback to UTRAN

l LOFD-070202 Ultra-Flash CSFB to UTRAN

l LOFD-001068 CS Fallback with LAI to UTRAN

l LOFD-001078 E-UTRAN to UTRAN CS/PS Steering

l LOFD-001088 CS Fallback Steering to UTRAN

l Load-based CSFB to UTRAN

CSFB ProcedureFigure 3-1shows the CSFB to UTRAN procedure.

Figure 3-1CSFB to UTRAN procedure

Measurement and Blind Handover

The eNodeB determines whether to trigger UTRAN measurements or blind handling forCSFB to UTRAN based on the status of the blind handling switch first.

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l If this option is selected, the eNodeB triggers blind handover directly.

l If this option is cleared, the eNodeB determines whether to trigger inter-RAT

measurements or blind handover based on the UE capability:

If the UE supports UTRAN measurements, the eNodeB triggers inter-RAT

measurements.

If the UE does not support UTRAN measurements, the eNodeB triggers a blind

handover.

For details about the measurement and handover, see Overview of Mobility Management in

Connected Mode Feature Parameter Description.

3.2 Feature Classification

3.2.1 Basic CSFB to UTRANThis section describes the optional feature LOFD-001033 CS Fallback to UTRAN. The

UtranCsfbSwitchoption of the ENodeBAlgoSwitch .HoAlgoSwitchparameter specifies

whether to enable this feature.

When a UE initiates a CS service in the E-UTRAN, the MME sends an S1-AP message

containing CS Fallback Indicator to the eNodeB, instructing the eNodeB to transfer the UE as

well as the CS service to a target network. For details about signaling procedures of MOC and

MTC, see 12.1 CSFB to UTRAN.

3.2.2 Flash CSFB to UTRAN

This section describes the optional feature LOFD-001052 Flash CS Fallback to UTRAN. TheUtranFlashCsfbSwitchoption of the ENodeBAlgoSwitch .HoAlgoSwitchparameter

specifies whether to enable this feature.

This feature is an enhancement to the optional feature LOFD-001033 CS Fallback to

UTRAN. When this feature is activated after enabled LOFD-001033 CS Fallback to UTRAN,

the eNodeB obtains the UTRAN cell information through the RIM procedures and then sends

the EUTRAN-to-UTRAN redirection message including the obtained UTRAN cell

information to the UE. In this case, the UE can access a UTRAN cell without obtaining

UTRAN cell information. This reduces the access delay. For details about how the UTRAN

cell information is delivered to the eNodeB through the RIM procedure, seeInteroperability

Between UMTS and LTE Feature Parameter Description.

This feature requires that the eNodeB can obtain UTRAN cell information through the RIM

procedures and the networks and UEs involved must comply with 3GPP Release 9 or later.

For details about the RIM procedure, see 3.7 RIM Procedure Between E-UTRAN and

UTRAN.

Other procedures are the same as those in CSFB to UTRAN. For details, see 3.2.1 Basic

CSFB to UTRAN.

3.2.3 Ultra-Flash CSFB to UTRAN

This section describes the optional feature LOFD-070202 Ultra-Flash CSFB to UTRAN. The

UtranUltraFlashCsfbSwitchoption of the ENodeBAlgoSwitch .HoAlgoSwitchparameterspecifies whether to enable this feature. This feature is a Huawei-proprietary feature. To

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enable this feature, the MME, MSC, and RNC must be all provided by Huawei and support

this feature.

When a UE initiates a CS service setup request in an LTE cell that does not support VoIP, this

feature enables the eNodeB to hand over the UE to the UTRAN through the SRVCC

procedure. It prepares CS resources on the UTRAN in advance and omits unnecessarysignaling processes during UTRAN access, thereby shortening the access delay for CSFB by

1s and improving user experience significantly. Compared with the standard procedure, the

ultra-flash CSFB to UTRAN procedure for Huawei omits certain signaling processes. For

details, see 12.1.5 Ultra-Flash CSFB to UTRAN.

The measurement procedure and blind handover procedure for this feature are the same as

those in CSFB to UTRAN. For details, see 3.2.1 Basic CSFB to UTRAN.

NOTE

The following table describes the parameters that must be set in the GLOBALPROCSWITCHMO to

turn on the UE compatibility switch when UEs do not support Ultra-Flash CSFB, resulting in UE

compatibility problems.

3.2.4 CS Fallback with LAI to UTRAN

This section describes the optional feature LOFD-001068 CS Fallback with LAI to UTRAN.

This feature is under license control and is not controlled by a switch.

This feature mainly applies to the following scenarios:

l In a multi-PLMN or national roaming scenario

An LAI consists of a PLMN ID and a LAC. In the CSFB with LAI function, the PLMN

ID identifies the CS network that the UE has registered with and will fall back to after

fallback.

If the serving E-UTRAN cell has multiple neighboring UTRAN or GERAN cells with

different PLMN IDs or the serving PLMN differs from the target PLMN, the operator

can use CSFB with LAI to achieve CSFB to a PLMN of the LAI preferentially.

l In a tracking area (TA) that overlaps multiple location areas (LAs)

The eNodeB selects a CSFB target cell with the same LAC as that mapped to the

network to which the UE has attached. An LAU is not required after CSFB, and

therefore the CSFB delay does not include the LAU time.

The eNodeB obtains the value of the LAI from the MME using an Initial Context Setup Req

or UE Context Mod Req message.

This feature is an enhancement to the optional feature LOFD-001033 CS Fallback to

UTRAN. With this feature, the eNodeB selects a target frequency or cell for measurement or

blind handover based on the LAI sent by the MME.

l In a measurement procedure, the eNodeB selects only an inter-RAT frequency on which

the PLMN ID of a neighboring cell is the same as that in the LAI received. The follow-

up measurement procedure is similar to that in CS Fallback to UTRAN. For details, see

3.4 Target Cell/Frequency Selection.

The difference is that the eNodeB sorts neighboring cells in the following order after

receiving measurement reports from a UE:

a. Neighboring cells with PLMN IDs and LACs the same as those in the LAI

b. Neighboring cells with PLMN IDs the same as that in the LAI but LACs different

from that in the LAI

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If no frequency or neighboring cell can be selected based on the LAI, the processing is

the same as that when no LAI is received.

l In a blind handover procedure, the eNodeB first selects a target cell for blind handover.

If no neighboring UTRAN cell is configured, the eNodeB preferentially selects the

UTRAN frequencies whose PLMN ID is the same as that in the LAI. The follow-upprocedure is the same as that described in 3.4 Target Cell/Frequency Selection.

If neighboring UTRAN cells are configured, the eNodeB preferentially selects the

operating UTRAN frequencies of the neighboring UTRAN cells whose PLMN ID is the

same as that in the LAI. The eNodeB then sorts thefrequencies based on the blind

handover priorities of the neighboring cells and frequency priorities for connected mode.

For details, see 3.4 Target Cell/Frequency Selection.

The eNodeB selects a target cell in the following order of preference:

a. Neighboring cell whose PLMN ID and LAC are the same as those in the LAI

b. If no neighboring cells described in aexist, the eNodeB selects the neighboring

cells with PLMN IDs the same as that in the LAI but LACs different from that inthe LAI.

c. If no neighboring cells described in aand bexist, the eNodeB selects the

neighboring cells with PLMN IDs the same as the serving PLMN ID of the UE.

If the InterPlmnHoSwitchoption of the ENodeBAlgoSwitch .HoAlgoSwitch

parameter is selected, the eNodeB also selects cells whose PLMN IDs are in the

target PLMN list.

3.2.5 E-UTRAN to UTRAN CS Steering

This section describes the CS steering function in the optional feature LOFD-001078 E-

UTRAN to UTRAN CS/PS Steering. For details about the PS steering function in this feature,seeInter-RAT Mobility Management in Connected Mode Feature Parameter Description.

This feature applies to a scenario where service steering is required in a UTRAN with

multiple UTRA frequencies. By setting CS service priorities for UTRA frequencies, the

operator can achieve CSFB from E-UTRAN only to the UTRA frequency that has a high CS

service priority.

CS Steering in CSFB

This function is an enhancement to the CS Fallback to UTRAN feature. The enhancements

are as follows:

l During inter-RAT measurement on the UTRAN, frequencieswith a high CS service

priority are preferentially measured.

The UtranFreqLayerMeasSwitch option of the ENodeBAlgoSwitch .FreqLayerSwtich

parameter specifies whether to enable this function.

If the option is selected, the eNodeB preferentially selects frequencies with a high CS

service priority specified by the UtranNFreq. CsPriorityparameter as the measurement

targets. A larger value of this parameter indicates a higher priority. If this parameter is set

to Priority_0(Priority 0)fora frequency, the eNodeB does not select this frequency as

the measurement target. The follow-up measurement procedure is similar to that in CS

Fallback to UTRAN. For details, see 3.4 Target Cell/Frequency Selection.

l

During blind handover, cells working on frequencies with a high CS service priority arepreferentially selected.

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The UtranFreqLayerBlindSwitch option of the ENodeBAlgoSwitch.FreqLayerSwtich

parameter specifies whether to enable this function.

If the option is selected, the eNodeB preferentially selects cells working on frequencies

with a high CS service priority specified by the UtranNFreq.CsPriorityparameter. A

larger value of this parameter indicates a higher priority. If this parameter is set toPriority_0(Priority 0)for a frequency, the eNodeB does not select cells working on this

frequency. The follow-up blind handover procedure is the same as that in CS Fallback to

UTRAN. For details, see 3.4 Target Cell/Frequency Selection.

LAI-based CS Steering in CSFB

This function is an enhancement to the CS Fallback with LAI to UTRAN feature. The

enhancements ar

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