ETSI TS 123 237 V15.2.0 (2019-10)

Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; IP Multimedia Subsystem (IMS) Service Continuity; Stage 2 (3GPP TS 23.237 version 15.2.0 Release 15)

RTS/TSGS-0223237vf20

General Information

• Status: Published
• Publication Date: 30-Sep-2019
• Technical Committee: 3GPP SA 2 - Architecture
• Current Stage: 12 - Completion
• Completion Date: 01-Oct-2019

Standards Content (Sample)

ETSI TS 123 237 V15.2.0 (2019-10)






TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS);
LTE;
IP Multimedia Subsystem (IMS) Service Continuity;
Stage 2
(3GPP TS 23.237 version 15.2.0 Release 15)

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3GPP TS 23.237 version 15.2.0 Release 15 1 ETSI TS 123 237 V15.2.0 (2019-10)



Reference
RTS/TSGS-0223237vf20
Keywords
GSM,LTE,UMTS
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3GPP TS 23.237 version 15.2.0 Release 15 2 ETSI TS 123 237 V15.2.0 (2019-10)
Intellectual Property Rights
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Legal Notice
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
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Modal verbs terminology
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"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI

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3GPP TS 23.237 version 15.2.0 Release 15 3 ETSI TS 123 237 V15.2.0 (2019-10)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 9
Introduction . 9
1 Scope . 10
2 References . 10
3 Definitions, symbols and abbreviations . 12
3.1 Definitions . 12
3.2 Abbreviations . 14
4 High level principles and architectural requirements . 14
4.1 Basic Assumptions . 14
4.1.0 General . 14
4.1.1 PS-CS Access Transfer . 14
4.1.2 PS-PS Access Transfer . 15
4.1.3 Inter-UE Transfer . 15
4.2 Architectural Requirements . 16
4.2.1 General Requirements . 16
4.2.2 Access Transfer Requirements . 16
4.2.3 IUT Requirements . 17
4.3 Service Continuity . 19
4.3.1 Session Transfer concepts . 19
4.3.1.1 General . 19
4.3.1.2 Access Transfer concepts . 19
4.3.1.2.1 General Access Transfer concepts . 19
4.3.1.2.2 Access Transfer (PS – CS) concepts . 19
4.3.1.2.2A MSC Server assisted mid-call feature . 20
4.3.1.2.3 Co-existence of ICS UE and MSC Server assisted mid-call feature . 20
4.3.1.3 Inter-UE Transfer concepts . 21
4.3.1.3.1 General . 21
4.3.1.3.2 Controller UE and Controllee UE operations . 21
4.3.1.3.2.1 Overview . 21
4.3.2 Void . 21
4.3.3 Information used for IMS Service Continuity . 21
5 Architecture model and reference points . 22
5.1 Overview . 22
5.2 Reference Architecture for non emergency session . 23
5.2.1 General . 23
5.2.2 Architecture when using ATCF enhancements. 23
5.3 Functional Entities . 24
5.3.1 SCC AS . 24
5.3.2 IMS Service Continuity UE . 25
5.3.2.1 Access Transfer Functions . 25
5.3.2.2 IUT Functions and Roles . 26
5.3.2.2.1 Functions . 26
5.3.2.2.2 Controller UE Role . 26
5.3.2.2.3 Controllee UE Role . 26
5.3.3 Emergency Access Transfer Function (EATF) . 27
5.3.4 Access Transfer Control Function (ATCF) . 27
5.3.4.1 General . 27
5.3.4.2 ATCF inclusion . 28
5.3.5 Access Transfer Gateway (ATGW) . 28
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3GPP TS 23.237 version 15.2.0 Release 15 4 ETSI TS 123 237 V15.2.0 (2019-10)
5.3.6 HSS . 28
5.3.7 MSC Server . 28
5.4 Signalling and bearer paths for IMS Service Continuity . 29
5.4.1 General . 29
5.4.2 Sessions with PS media flow(s) . 29
5.4.2a Sessions with PS media flow(s) using ATCF . 29
5.4.3 Sessions with CS media . 30
5.4.3a Sessions with CS media flow(s) using ATCF . 30
5.5 IUT Collaborative Sessions . 30
5.6 Reference Architecture for SRVCC emergency session . 31
6 Procedures and flows for Access Transfer . 32
6.0 Introduction . 32
6.1 Registration . 32
6.1.1 General . 32
6.1.2 Registration using ATCF enhancements. 32
6.1.3 Registration: CS to PS - Single Radio . 34
6.1.3.1 IMS Registration by UE . 34
6.1.3.2 UE IMS Registration change update . 34
6.2 Origination and Termination . 35
6.2.1 Origination . 35
6.2.1.1 Origination Procedures . 35
6.2.1.2 Originating sessions that use CS media . 35
6.2.1.3 Originating sessions that use only PS media flow(s) . 36
6.2.1.3a Originating sessions that use only PS media flow(s) - fallback to CS domain in pre-alerting phase . 37
6.2.1.4 Originating sessions for (v)SRVCC that use ATCF enhancements . 38
6.2.1.5 Originating sessions for CS to PS - Single Radio . 38
6.2.2 Termination. 39
6.2.2.1 Termination Procedures . 39
6.2.2.2 Terminating sessions that use CS media . 39
6.2.2.3 Terminating sessions that use only PS media flow(s) . 40
6.2.2.3a Terminating sessions that use only PS media flow(s) - fallback to CS domain in pre-alerting
phase . 41
6.2.2.4 Terminating sessions over Gm where speech media is not accepted by the UE . 42
6.2.2.5 Terminating sessions for (v)SRVCC that use ATCF enhancements . 43
6.2.2.6 Terminating sessions for CS to PS - Single Radio . 43
6.3 Access Transfer . 44
6.3.1 Access Transfer Procedure . 44
6.3.1.1 Introduction . 44
6.3.1.2 Access Transfer Procedures . 44
6.3.1.2a Access Transfer Procedures using ATCF enhancements . 45
6.3.1.3 Enablement of Access Transfer procedures . 45
6.3.1.3a Enablement of Access Transfer procedures using ATCF enhancements . 46
6.3.1.4 Execution of Access Transfer procedures . 46
6.3.1.4a Execution of Access Transfer procedures using ATCF enhancements . 46
6.3.1.5 Remote Leg Update. 46
6.3.1.6 Source Access Leg Release . 47
6.3.1.7 Access Transfer Information for ATCF . 47
6.3.2 Access Transfer Information flows . 48
6.3.2.0 General . 48
6.3.2.1 PS – CS Access Transfer . 48
6.3.2.1.1 PS – CS Access Transfer: PS to CS - Dual Radio . 48
6.3.2.1.1a PS – CS Access Transfer: PS to CS – Dual Radio with Session State Information . 49
6.3.2.1.2 PS – CS Access Transfer: CS to PS - Dual Radio . 51
6.3.2.1.2a PS – CS Access Transfer: CS to PS – Dual Radio with Session State Information . 52
6.3.2.1.2b CS - PS Access Transfer: CS to PS - Dual Radio, incoming voice call in alerting phase . 52
6.3.2.1.2c CS - PS Access Transfer: CS to PS - Dual Radio, outgoing voice call in pre-alerting state or
in alerting phase . 53
6.3.2.1.2d PS - CS Access Transfer: PS to CS - Dual Radio, outgoing voice or video call in pre-alerting
state or in alerting phase . 53
6.3.2.1.2e PS - CS Access Transfer: PS to CS - Dual Radio, incoming voice call in alerting phase . 54
6.3.2.1.3 Subsequent Access Transfers . 56
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3GPP TS 23.237 version 15.2.0 Release 15 5 ETSI TS 123 237 V15.2.0 (2019-10)
6.3.2.1.4 PS – CS Access Transfer: PS to CS – Single Radio . 56
6.3.2.1.4a PS – CS Access Transfer: PS to CS – Single Radio with Session State Information . 57
6.3.2.1.4b PS to CS Access Transfer: PS to CS – Single Radio; using I1 reference point . 59
6.3.2.1.4c PS - CS Access Transfer: PS to CS - Single Radio, incoming voice or video call in pre-
alerting or alerting phase . 61
6.3.2.1.4d PS - CS Access Transfer: PS to CS - Single Radio, outgoing voice or video call in pre-
alerting state or in alerting phase . 62
6.3.2.1.4e PS - CS Access Transfer: PS to CS - Single Radio, voice and video . 64
6.3.2.1.5 PS – CS Access Transfer for voice and video, Dual Radio . 66
6.3.2.1.6 PS – CS Access Transfer: PS to CS – Dual Radio, mid-call service with an active speech and
video session . 67
6.3.2.1.7 PS – CS Access Transfer: PS to CS – Dual Radio, mid-call service with one inactive speech
and video session . 67
6.3.2.1.7a PS - CS Access Transfer: PS to CS - Single Radio, mid-call service with an incoming waiting

call in alerting phase . 68
6.3.2.1.7b PS - CS Access Transfer: PS to CS - Single Radio, mid-call service with an outgoing call in
pre-alerting state or in alerting phase. 70
6.3.2.1.7c PS - CS Access Transfer: PS to CS - Single Radio, mid-call service with an incoming call in
alerting phase and a held session . 72
6.3.2.1.8 PS - CS Access Transfer: Conferencing - for UEs not using ICS capabilities . 74
6.3.2.1.9 PS – CS Access Transfer: PS to CS – Single Radio using ATCF enhancements . 75
6.3.2.1.10 PS - CS Access Transfer: CS to PS - Single Radio . 78
6.3.2.2 PS - PS Access Transfer . 81
6.3.2.2.1 PS-PS Access Transfer with full media transfer . 81
6.3.2.2.2 PS-PS Access Transfer with partial media transfer . 82
6.3.2.2.3 PS-PS Access Transfer with full media transfer for an incoming call in early dialog phase . 82
6.3.2.2.4 PS-PS Access Transfer with full media transfer for an outgoing call in early dialog phase . 84
6.3.2.3 PS - PS in conjunction with PS - CS Access Transfer . 85
6.3.2.3.1 PS - PS in conjunction with PS - CS Access Transfer: PS to CS for UEs not using ICS
capabilities . 85
6.3.2.3.2 PS - PS in conjunction with PS - CS Access Transfer: CS to PS for UEs not using ICS
capabilities . 87
6.3.2.3.3 PS – PS in conjunction with PS - CS Access Transfer: PS to CS for UEs with ICS capabilities
- Using Gm reference point . 87
6.3.2.3.4 PS - PS in conjunction with PS - CS Access Transfer: CS to PS for UEs with ICS capabilities
- Using Gm reference point . 89
6.3.2.3.5 PS – PS in conjunction with PS – CS Access Transfer: Active/Held sessions - Using Gm
reference point . 89
6.3.2.3.6 PS – PS in conjunction with PS – CS Access Transfer: Explicit Communication Transfer -
Using Gm reference point. 90
6.3.2.3.7 PS – PS in conjunction with PS – CS Access Transfer: Conferencing - Using Gm reference
point . 90
6.3.2.3.8 PS – PS in conjunction with PS – CS Access Transfer: PS to CS – using I1 reference point . 90
6.3.2.3.9 PS - PS in conjunction with PS - CS Access Transfer: CS to PS - using I1 reference point . 92
6.3.2.3.10 PS - PS in conjunction with PS - CS Access Transfer: PS to CS for Active/Held sessions -
using I1 reference point . 92
6.3.2.3.11 PS - PS in conjunction with PS - CS Access Transfer: CS to PS for Active/Held sessions -
using I1 reference point . 93
6.3.3 Media Adding/Deleting . 93
6.3.3.1 Local End Initiation case: Adding new PS media to existing CS session . 93
6.3.3.2 Local End Initiation case: Incorporating existing CS media in new IMS Session and Gm Service
Control . 94
6.3.3.3 Local End Initiation case: Adding PS media to IMS session with CS media . 95
6.3.3.4 Remote End Initiation case: Adding new PS media to existing CS session . 96
6.3.3.5 Remote End Initiation case: Incorporating existing CS media in new IMS Session and Gm
Service Control . 97
6.3.3.6 Remote End Initiation case: Adding PS media to IMS session with CS media . 98
6.3.3.7 Local End Initiation case – Removing media from split CS and PS sessions . 99
6.3.3.8 Remote End Initiation case – Removing media from split CS and PS sessions . 100
6.3.3.9 Local End Initiation case: Adding new PS media to existing PS session. 101
6.3.3.10 Remote End Initiation case: Adding new PS
...