Emergency Call Handling for CS Fallback.pdf

Emergency Call Handling for CS Fallback

USER 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 2

2 Feature Operation 3

2.1 Network Configuration Requirements 3

2.2 Feature Overview 3

2.3 Entering CS Fallback Priorities for Emergency Calls 3

3 Parameters 5

3.1 Introduced Parameters 5

3.2 Affected Parameters 5

4 Network Impact 7

5 Associated Features 9

5.1 Prerequisite Features 9

5.2 Affected Features 9

5.3 Related Features 9

5.4 Affected System Functions 9

6 Performance 11

6.1 KPIs 11

6.2 Counters 11

6.3 Events 11

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Introduction

1 Introduction

This document describes the Emergency Call Handling for CS Fallback feature.

The main characteristics of the feature are presented below.

The Emergency Call Handling for CS Fallback feature enables the operatorto apply unique frequency and frequency group priorities for emergencycalls. The operator might prefer to use the WCDMA network as CS fallbackfor ordinary calls while the GSM network is preferred for emergency calls.When the eNodeB receives a CS Fallback request from the MME indicatingan emergency call the eNodeB applies the priorities for emergency call CSfallback, when selecting the frequency or frequency group to which CS fallbackis applied. If the Emergency Call Handling for CS Fallback feature has not beenactivated, the eNodeB applies the CS fallback priorities for normal calls. If theEmergency Call Handling for CS Fallback feature has been activated but thepriority parameters have not been configured, the default value (=0, lowestpriority) will be applied.

The feature also introduces a number of counters to enhance the observabilityof CS Fallback for emergency calls.

1.1 Basic Characteristics

Feature identity:FAJ 221 0991, Emergency Call Handling for CS Fallback

Dependencies

This feature requires the following RAN features to be active:

CS Fallback to GERAN and UTRAN

Coverage-Triggered GERAN Session Continuity

Coverage-Triggered WCDMA Session Continuity

This feature affects the following RAN features:

This feature affects no other features.

1.2 Benefits

The Emergency Call Handling for CS Fallback feature offers the operator thepossibility to apply separate priorities for CS fallback for emergency calls ascompared to CS fallback for ordinary voice calls. This allows the operator to

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direct emergency calls to the network that has the best positioning performanceand thus comply to the FCC phase 2 requirements on positioning accuracyfor such calls.

Emergency calls will be directed to the network resources the operatorconsiders best to handle such calls.

1.3 Additional Information

This section provides a reference or link to other sources of information whichmay provide useful background information in regards to the feature.

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

3GPP TS 23.272- Circuit Switched (CS) fallback in Evolved Packet System(EPC); Stage 2

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Feature Operation

2 Feature Operation

This section describes the Emergency Call Handling for CS Fallback feature inmore detail, including network configuration requirements.

2.1 Network Configuration Requirements

This section provides a list of the network configuration prerequisites which arerequired for the feature to work correctly.

The following network configuration prerequisites must be fulfilled at featureactivation:

The feature CS Fallback to GERAN and UTRAN must be activated in theeNodeB

The feature Coverage-Triggered GERAN Session Continuity must beactivated in the eNodeB

The feature Coverage-Triggered WCDMA Session Continuity must beactivated in the eNodeB

2.2 Feature Overview

The Emergency Call Handling for CS Fallback feature enables the operator toapply unique frequency and frequency group priorities for emergency calls.As an example the operator might prefer to use the WCDMA network as CSfallback for ordinary calls while the GSM network is preferred for emergencycalls.

2.3 Entering CS Fallback Priorities for Emergency Calls

The operator is expected to enter the priority level for each UTRAN frequencyand each GERAN frequency group with a relation to the cell. If the same priorityis set for two or more frequencies/frequency groups then no deterministicprioritization among those will take place. To achieve a deterministic behavioreach frequency/frequency group must have a unique priority. The concernedpriority parameters are shown in Section 3 on page 5 .

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Parameters

3 Parameters

This section describes the parameters introduced by the Emergency CallHandling for CS Fallback feature and parameters affected by activating thefeature.

3.1 Introduced Parameters

Table 1and Table 2 describe the parameters introduced by the feature:

Table 1 Introduced Parameter in UtranFreqRelation MO

Parameter Description

csFallbackPrioEc csFallbackPrioEc provides the priority for a UTRAN frequencyat CS fallback of an emergency call.

Priority levels 0 to 7 are defined where 7 is the highest priority.The priority is set for each UTRAN frequency relation to the cell.

Table 2 Introduced Parameter in GeranFreqGroupRelation MO

Parameter Description

csFallbackPrioEc csFallbackPrioEc provides the priority for a GERAN frequencygroup at CS fallback of an emergency call.

Priority levels 0 to 7 are defined where 7 is the highest priority. Thepriority is set for each GERAN frequency group relation to the cell.

3.2 Affected Parameters

No parameters are affected by the implementation of this feature

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Network Impact

4 Network Impact

There is no impact on the network resulting from the implementation of thisfeature.

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Associated Features

5 Associated Features

This section describes how the Emergency Call Handling for CS Fallbackfeature affects other features and functions.

5.1 Prerequisite Features

Table 3 lists prerequisite features to the Emergency Call Handling for CSFallback feature, that is, they must be active prior to introducing the EmergencyCall Handling for CS Fallback feature.

Table 3 Prerequisite Features

Feature Description

CS Fallback to GERAN and UTRAN This feature allows an LTE device to drop back to the legacyWCDMA or GSM network if IMS VoIP capabilities are notsupported

Coverage-Triggered GERAN SessionContinuity

The purpose of the Coverage-Triggered GERAN SessionContinuity feature is the following: To manage the redirectionof User Equipment (UE) in RRC_CONNECTED mode towardsa GERAN network when the UE measures poor coverage inthe current LTE frequency. The redirection is controlled bythe network and triggered by UE measurement reports ofthe serving LTE cell. To provide system information aboutalternative GERAN networks that can be used by an UE inRRC_IDLE mode

Coverage-Triggered WCDMA SessionContinuity

The purpose of the Coverage-Triggered WCDMA SessionContinuity feature is the following: To manage the redirectionof User Equipment (UE) in RRC_CONNECTED mode towardsa WCDMA network when the UE measures poor coveragein the current LTE frequency. The redirection is controlledby the network and triggered by UE measurement reports ofthe serving LTE cell. To provide system information aboutalternative WCDMA networks that can be used by an UE inRRC_IDLE mode

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

This feature affects no system functions.

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Performance

6 Performance

This section describes performance indicators, counters, and events associatedwith the Emergency Call Handling for CS Fallback feature.

6.1 KPIs

This feature has no associated Key Performance Indicators (KPIs).

6.2 Counters

The important counters and events associated with the Emergency CallHandling for CS Fallback feature are listed in Table 4.

Table 4 Counters

Counter Description

pmUeCtxtRelCsfbGsm Number of CS fallback attemps performed towards thisGSM frequency group, counted per EUTRAN cell

pmUeCtxtRelCsfbGsmEm Number of emergency CS fallback attempts towards thisGSM frequency group, counted per EUTRAN cell

pmUeCtxtRelCsfbWcdma Number of CS fallback attempts performed towards thisWCDMA frequency, counted per EUTRAN cell

pmUeCtxtRelCsfbWcdmaEm Number of emergency CS fallback attempts towards thisWCDMA frequency, counted per EUTRAN cell

pmUeCtxtRelCsfbLimitedDualRadioUeCdma

Number of CS fallback attempts for limited dual radio UELTE/1xRTT, counted per EUTRAN cell

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

6.3 Events

Table 5 lists the events associated with the Emergency Call Handling for CSFallback feature.

Table 5 Events

Event Event Parameter Description

INTERNAL_EVENT_UE_MOBILITY_EVAL

EVENT_PARAM_MOBILITY_DECISION

Indicates the decision the mobilityevaluation has taken.


EVENT_PARAM_MOBILITY_TRIGGER

Indicates the trigger for performinga mobility evaluation.

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Event Event Parameter Description


EVENT_PARAM_REDIRECT_RELEASE_INFO

Information about what technologythe RRC release will redirect the UEto


EVENT_PARAM_RELEASE_WITH_REDIRECT_REASON

If the mobility decision is Releasewith Redirect, this parameterindicates the reason. Otherwise,unavailable.

More information about events can be found in PM Event List.

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toc1 Introduction1.1 Basic CharacteristicsDependencies1.2 Benefits1.3 Additional Information2 Feature Operation2.1 Network Configuration Requirements2.2 Feature Overview2.3 Entering CS Fallback Priorities for Emergency Calls3 Parameters3.1 Introduced Parameters3.2 Affected Parameters4 Network Impact5 Associated Features5.1 Prerequisite Features5.2 Affected Features5.3 Related Features5.4 Affected System Functions6 Performance 6.1 KPIs6.2 Counters6.3 Events

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Emergency Call Handling for CS Fallback.pdf