CS Fallback for Dual-Radio UEs

DESCRIPTION

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Copyright

© Ericsson AB 2011. All rights reserved. No part of this document may bereproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due tocontinued progress in methodology, design and manufacturing. Ericsson shallhave no liability for any error or damage of any kind resulting from the useof this document.

Trademark List

All trademarks mentioned herein are the property of their respective owners.These are shown in the document Trademark Information.

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Contents

Contents

1 Introduction 1

1.1 Basic Characteristics 1

1.2 Benefits 1

1.3 Additional Information 1

2 Feature Operation 3

2.1 Network Requirements 3

2.2 Feature Operation Sequence Diagram 3

2.3 Process Steps 5

3 Parameters 7

3.1 Introduced Parameters 7

3.2 Affected Parameters 7

4 Network Impact 9

4.1 Capacity 9

4.2 Paging 9

5 Associated Features 11

5.1 Prerequisite Features 11

5.2 Affected Features 11

5.3 Related Features 11

5.4 Affected System Functions 11

6 Performance 13

6.1 KPIs 13

6.2 Counters 13

6.3 Events 13

7 O&M Information 15

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CS Fallback for Dual-Radio UEs

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Introduction

1 Introduction

This document describes the 1xRTT CS Fallback for Dual-Radio UEs featureand its main benefits and impacts in the LTE RAN.

When CS Fallback for Dual-Radio UEs is enabled, LTE radio failures and LTEpaging to the UE is prevented while on a 1xRTT CS call.

1.1 Basic Characteristics

This section describes the basic characteristics of the feature.

FDD FAJ 121 0845, CS Fallback for Dual-Radio UEs

Replaces: N/A

Dependencies

This feature has no prerequisite features.

This feature affects no other features.

1.2 Benefits

This section describes the benefits of this feature.

The CS Fallback for Dual-Radio UEs feature is a licensed feature. It allowsUser Equipment (UE) in either RRC_CONNECTED or RRC_IDLE to gracefullydisconnect its RRC connection from the LTE network to answer or initiatea CS call on 1xRTT. These disconnections no longer appear as radio linkfailures in Performance Management (PM) counters. This feature also preventssuperfluous paging to UE that are unavailable because they are handling aspeech call on 1xRTT.

1.3 Additional Information

More information about this feature and related topics can be found in thefollowing documentation:

• 3GPP TS 23.272

• 3GPP TS 36.331

• 3GPP TS 36.413

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• 3GPP TS 36.300

• 3GPP2 X.S0004-321-E v2.0

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Feature Operation

2 Feature Operation

This section describes the CS Fallback for Dual-Radio UEs feature in moredetail, including network configuration requirements and operation flows.

2.1 Network Requirements

This feature has no prerequisite network configuration requirements.

2.2 Feature Operation Sequence Diagram

Figure 1 shows a basic indication of the feature steps.

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CS Fallback for Dual-Radio UEs

L0000369A

LTE

1xRTT

LTE

1xRTT

1. UE connected to LTE and 1xRTT networks

2. UE initiates or is paged by 1xRTT CS call

3. UE connected to 1xRTT network only

Figure 1 Basic Feature Flow for CS Fallback for Dual-Radio UEs

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Feature Operation

2.3 Process Steps

This section describes the main process steps for the feature flow as shownin Figure 2.

Step descriptions are presented in Section 2.3.2 on page 6.

L0000370A

1. UE is E-UTRAN attached and registered with 1xRTT

10. 1xRTT MO or MT call establishment per 3GPP2 specifications

2. UE decisionto perform MOcall in 1xCS

6. E-UTRAN triggers RRC connection release

8. MME suspends all bearers for the UE

4. S1 UE Context

Modification Request

3. Extended Service Request

5. S1 UE Context

ModificationResponse

7. S1 UEContext Release

Request

9. S1 UE Context Release

1xRTT dual

mode UE

1xRTT IWS

1xRTTMSC SGWE-UTRAN MME

Figure 2 Signaling Flow Chart

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CS Fallback for Dual-Radio UEs

2.3.1 Initialization

Once the feature is enabled, SIB8 messages sent to the UE containing thecsfb-SupportForLimitedDualRadioUEs parameter.

2.3.2 Signaling Flow

The following scenario occurs when the user decides to make a MobileOriginating call or is about to receive a Mobile Terminating (MT) call:

1 The UE is E-UTRAN RRC_CONNECTED or E-UTRAN RRC_IDLE andregistered with 1xRTT.

2 The user of the UE performs a Mobile Originating CS call or is about toreceive a MT CS call.

3 The UE sends an extended service request to the MME over NAS (passingtransparently through the eNodeB).

4 The MME sends a S1 UE Context Modification indicating CS Fallbackrequired. If the UE is in RRC_IDLE state, the MME sends a S1 UE ContextSetup Request message indicating CS Fallback required.

5 The E-UTRAN sends a S1 UE Context Modification Response. If theUE is in RRC_IDLE state, the E-UTRAN sends a S1 UE Context SetupResponse message.

6 E-UTRAN performs a RRC Connection Release.

7 A S1 UE Context Release Request is sent to MME.

8 MME suspends all bearers for the UE

9 MME sends a UE Context Release to the E-UTRAN.

10 The 1xRTT Mobile Originating or MT Call is established.

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Parameters

3 Parameters

This section describes the parameters introduced by the CS Fallback forDual-Radio UEs feature and parameters affected by activating the feature.

3.1 Introduced Parameters

Table 1 describes the parameters introduced by the feature.

Table 1 Introduced Parameters

Parameter Description

featureStateCsfbForLimitedDualRadioUE Indicates whether the CS Fallback for Limited Dual-Radio UEslicensed feature is ACTIVATED or DEACTIVATED

licenseStateCsfbForLimitedDualRadioUE Indicates whether the licensed state of the CS Fallback for LimitedDual-Radio UEs feature is ENABLED or DISABLED

serviceStateCsfbForLimitedDualRadioUE Indicates if the CS Fallback for Limited Dual-Radio UEs feature isoperable or inoperable

3.2 Affected Parameters

The implementation of this feature affects no parameters.

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Network Impact

4 Network Impact

This section describes how the CS Fallback for Dual-Radio UEs feature impactsthe network functions and capabilities.

4.1 Capacity

This section provides information on the impact of the feature on networkcapacity.

This feature provides a small increase in radio capacity by freeing wasted LTEradio resources of dual mode UE that engages in CS calls on the 1xRTTnetwork.

4.2 Paging

Dual-Band UE on CS calls in 1xRTT networks is not paged by the LTE network.

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Associated Features

5 Associated Features

This section describes how the CS Fallback for Dual-Radio UEs feature affectsother features and functions.

5.1 Prerequisite Features

This feature has no prerequisite features.

5.2 Affected Features

This feature affects no other feature.

5.3 Related Features

This feature is not related to any other feature.

5.4 Affected System Functions

Table 2 lists functions affected by the CS Fallback for Dual-Radio UEs feature.

Table 2 Affected System Functions

Function Description

CS Call Setup Time on1xRTT

This feature increases the CS call setup time on 1xRTT for dual-radio UEbecause the radio connection on LTE must be removed before the 1xRTT callcan be setup. CS call setup time on 1xRTT for dual-radio UE is still faster thansingle-radio UE because they are already connected to the 1xRTT network.

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Performance

6 Performance

This section describes performance indicators, counters, and events associatedwith the CS Fallback for Dual-Radio UEs feature.

6.1 KPIs

Table 3 lists the main Key Performance Indicators (KPIs) associated with theCS Fallback for Dual-Radio UEs feature.

Table 3 KPIs

KPI Description

Drop Call Rate Enabling the CS Fallback for Dual-Radio UEs feature reduces the dropcall rate (pmErabRelAbnormalEnb / (pmErabRelAbnormalEnb +pmErabRelNormalEnb)) because pmErabRelNormalEnb is peggedwhen releasing the radio link prior to fallback and that the UE can no longerpeg pmErabRelAbnormalEnb once it disconnects from LTE.

6.2 Counters

Table 4 lists the counters associated with the CS Fallback for Dual-Radio UEsfeature.

Table 4 Counters in MO EUtranCellFDD

Counter Description

pmErabRelNormalEnb Total number of normal E-RAB Releases triggeredby RBS per cell

pmUeCtxtRelNormalEnb Total number of normal UE Context Releases percell initiated by the RBS

pmErabRelNormalEnbAct Total number of normal UE Context Releases percell initiated by the RBS and where data is lost

pmUeCtxtRelNormalEnbAct Total number of normal UE Context Releases percell initiated by the RBS and where data is lost

INTERNAL_PROC_UE_CTXT_RELEASE_ENB Cause value (CS Fallback Triggered) for theprocedure event sent for UE Context Release

More information about counters can be found in Managed Object Model RBS.

6.3 Events

This feature has no associated events.

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O&M Information

7 O&M Information

This section provides Operation and Maintenance (O&M) information for theCS Fallback for Dual-Radio UEs feature.

Activating the CS Fallback for Dual-Radio UEs feature requires thatthe corresponding license is installed. For more information onhandling licenses, see the document License Management. TheCS Fallback for Dual-Radio UEs feature is activated by setting thefeatureStateCsfbForLimitedDualRadioUE parameter to ACTIVATED.The operation state of the CS Fallback for Dual-Radio UEs feature can bechecked with the parameter serviceStateCsfbForLimitedDualRadioUE.

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