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)

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)

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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ETSI
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
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
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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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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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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 media to existing PS session . 101
6.3.3.11 Local End Initiation case: Removing media from split PS sessions . 101
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6.3.3.12 Remote End Initiation case: Removing media from split PS sessions . 101
6.3.4 Void . 101
6.3.5 Service continuity for ICS UE using MSC Server assisted mid-call feature while maintaining CS
media . 101
6.4 Operator Policy and User Preferences . 101
6.5 Execution of supplementary services . 102
6.5.1 General . 102
6.5.2 Originating Identification Presentation (OIP) . 102
6.5.3 Originating Identification Restriction (OIR) . 103
6.5.4 Terminating Identification Presentation (TIP) . 103
6.5.5 Terminating Identification Restriction (TIR) . 103
6.5.6 Communication Diversion (CDIV) . 103
6.5.7 Communication Hold (HOLD) . 103
6.5.8 Communication Barring (CB). 103
6.5.9 Message Waiting Indication (MWI) . 103
6.5.10 Conference (CONF) . 103
6.5.11 Explicit Communication Transfer (ECT) . 104
6.5.12 Advice of Charge (AOC) . 104
6.5.13 Closed User Groups (CUG) . 104
6.5.14 Three-Party (3PTY) . 104
6.5.15 Flexible Alerting (FA) . 104
6.5.16 Communication Waiting (CW) . 104
6.5.17 Completion of Communications to Busy Subscriber (CCBS)/Completion of Communications by No
Reply (CCNR) . 104
6.5.18 Customized Alerting Tones (CAT) . 104
6.5.19 Malicious Communication IDentification (MCID) . 104
6.5.20 Reverse Charging . 104
6.5.21 Personal Network Management (PNM) . 105
6.5.22 Customized Ringing Signal (CRS) . 105
6a Procedures and flows for Inter-UE Transfer . 105
6a.0 Introduction . 105
6a.0.1 Void . 105
6a.1 IUT general procedures . 105
6a.1.1 General . 105
6a.1.2 Remote Leg Update . 105
6a.2 Information flows for Collaborative Session establishment . 105
6a.2.1 Establish Collaborative Session by transferring media . 105
6a.2.2 Establish Collaborative Session with new media. 106
6a.2.3 Establish Collaborative Session at originating IMS session setup . 107
6a.2.4 Establish Collaborative Session at terminating IMS session setup . 109
6a.3 Media Transfer within Collaborative Session . 110
6a.3.1 Controller UE initiated media transfer from Controller UE to Controllee UE . 110
6a.3.1.1 Controller UE and Controllee UE belong to the same subscription . 110
6a.3.1.2 Controller UE and Controllee UE belong to different subscriptions . 111
6a.3.2 Controller UE initiated media transfer from Controllee UE to Controller UE . 112
6a.3.3 Controller UE initiated media transfer from Controllee UE to another Controllee UE . 113
6a.3.3.1 Controller UE and Controllee UEs belong to the same subscription . 113
6a.3.3.2 Controller UE and Controllee UEs belong to different subscriptions . 114
6a.3.3a Controllee UE Initiated Transfer Media from one Controllee UE to another Controllee UE . 116
6a.3.4 Void . 117
6a.3.4.1 Void. 117
6a.3.4.2 Void. 117
6a.4 Media adding/deleting/modifying within Collaborative Session . 118
6a.4.1 Controller UE initiated add new media on Controller UE . 118
6a.4.2 Controller UE initiated add new media on Controllee UE . 118
6a.4.2.1 Controller UE and Controllee UE belong to the same subscription . 118
6a.4.2.2 Controller UE and Controllee UE belong to different subscriptions . 119
6a.4.3 Controller UE Initiated Release Media (media flow on the Controller UE) . 121
6a.4.4 Controller UE Initiated Release Media (media flow on the Controllee UE) . 122
6a.4.4.1 Controller UE and Controllee UE belong to the same subscription . 122
6a.4.4.2 Controller UE and Controllee UE belong to different subscriptions . 123
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6a.4.4a Controller UE initiated modify media (media flow on the Controllee UE) . 124
6a.4.4a.1 Controller UE and Controllee UE belong to the same IMS subscription . 124
6a.4.4a.2 Controller UE and Controllee UE belong to different IMS subscriptions under the same operator . 125
6a.4.5 Controllee UE initiated release media on itself. 126
6a.4.6 Controllee UE initiated modify media on itself . 127
6a.4.6.0 General . 127
6a.4.6.1 Controller UE and Controllee UE belong to the same IMS subscription . 127
6a.4.6.2 Controller UE and Controllee UE belong different IMS subscriptions under the same operator . 128
6a.4.6a Controllee UE initiated add new media on another Controllee UE . 129
6a.4.7 Remote party initiated add new media . 130
6a.4.8 Remote party initiated release media . 132
6a.4.9 Remote party initiated media modification . 133
6a.4a Transfer of Collaborative Session Control . 133
6a.4a.1 Controller UE transfers Collaborative Session Control to a Controllee UE without Media Transfer. 133
6a.4a.2 Controller UE transfers Collaborative Session Control to another UE with Media Transfer . 135
6a.4a.3 Transfer of Collaborative Session Control upon loss of Controller UE . 136
6a.4a.4 Transfer of Collaborative Session Control with media flows upon loss of Controller UE . 137
6a.4a.5 Transfer of Collaborative Session Control initiated by the target UE . 139
6a.5 Collaborative Session release . 140
6a.5.1 Controller UE Initiated Release Collaborative Session . 140
6a.5.2 Remote Party Initiated Release Collaborative Session . 141
6a.6 Inter-UE Transfer without establishing a Collaborative Session . 141
6a.6.1 Inter-UE Transfer initiated by the source UE . 141
6a.6.2 Inter-UE Transfer initiated by the target UE. 143
6a.7 Execution of supplementary services . 144
6a.7.1 General . 144
6a.7.2 Originating Identification Presentation (OIP) . 144
6a.7.3 Originating Identification Restriction (OIR) . 144
6a.7.4 Terminating Identification Presentation (TIP) . 144
6a.7.5 Terminating Identification Restriction (TIR) . 144
6a.7.6 Communication Diversion (CDIV) . 144
6a.7.7 Communication Hold (HOLD) . 144
6a.7.7.1 Controller UE invoking the HOLD service on the media flow on a Controllee UE . 145
6a.7.8 Communication Barring (CB). 145
6a.7.9 Message Waiting Indication (MWI) . 145
6a.7.10 Conference (CONF) . 146
6a.7.11 Explicit Communication Transfer (ECT) . 146
6a.7.12 Advice of Charge (AOC) . 146
6a.7.13 Closed User Groups (CUG) .
...