ETSI TS 129 379 V19.1.0 (2026-03)

LTE; 5G; Mission Critical Push To Talk (MCPTT) call control interworking with Land Mobile Radio (LMR) systems; Stage-3 (3GPP TS 29.379 version 19.1.0 Release 19)

RTS/TSGC-0129379vj10

General Information

• Status: Not Published
• Technical Committee: 3GPP CT 1 - MM/CC/SM [lu] (formely CN1)
• Current Stage: 8 - Draft receipt by ETSI Secretariat
• Completion Date: 10-Mar-2026

Standards Content (Sample)

TECHNICAL SPECIFICATION
LTE;
5G;
Mission Critical Push To Talk (MCPTT) call control
interworking with Land Mobile Radio (LMR) systems;
Stage-3
(3GPP TS 29.379 version 19.1.0 Release 19)

3GPP TS 29.379 version 19.1.0 Release 19 1 ETSI TS 129 379 V19.1.0 (2026-03)

Reference
RTS/TSGC-0129379vj10
Keywords
5G,LTE
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ETSI
3GPP TS 29.379 version 19.1.0 Release 19 2 ETSI TS 129 379 V19.1.0 (2026-03)
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ETSI
3GPP TS 29.379 version 19.1.0 Release 19 3 ETSI TS 129 379 V19.1.0 (2026-03)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 9
1 Scope . 11
2 References . 11
3 Definitions of terms, symbols and abbreviations . 12
3.1 Terms . 12
3.2 Abbreviations . 13
4 General . 13
4.1 IWF overview . 13
4.2 Warning Header Field . 13
4.2.1 General . 13
4.2.2 Warning texts . 13
4.3 MCPTT priority calls and alerts . 14
4.4 Media security at the IWF . 14
4.5 Broadcast group calls . 14
5 Functional entities . 14
5.1 General . 14
5.2 Functional connectivity models . 15
6 Call control common procedures . 17
6.1 SDP . 17
6.1.1 SDP offer generation . 17
6.1.2 SDP answer generation . 17
6.2 Commencement modes . 18
6.2.1 Automatic commencement mode . 18
6.2.2 Manual commencement mode for private calls . 18
6.3 Receiving an MCPTT session release request . 19
6.4 Priority call conditions . 19
6.4.1 MCPTT emergency group call conditions . 19
6.4.1.1 SIP INVITE request for originating MCPTT emergency group calls . 19
6.4.1.2 Resource-Priority header field for MCPTT emergency group calls . 20
6.4.1.3 SIP re-INVITE request for cancelling MCPTT in-progress emergency group state . 20
6.4.1.4 Receiving a SIP 2xx response to a SIP request for a priority call . 21
6.4.1.5 Receiving a SIP 4xx response, SIP 5xx response or SIP 6xx response to a SIP request for a
priority group call . 22
6.4.1.6 SIP request for originating MCPTT imminent peril group calls . 22
6.4.1.7 SIP re-INVITE request for cancelling MCPTT in-progress imminent peril group state . 22
6.4.1.8 Resource-Priority header field for MCPTT imminent peril group calls . 23
6.4.1.9 Receiving a SIP INFO request in the dialog of a SIP request for a priority group call . 23
6.4.1.10 SIP re-INVITE request for cancelling the in-progress emergency group state of a group by a
third-party. 24
6.4.1.11 Resource-Priority header field values . 24
6.4.1.12 Receiving a SIP 2xx response to a SIP INVITE request for a priority adhoc group call . 25
6.4.1.13 Receiving a SIP 4xx response, SIP 5xx response or SIP 6xx response to a SIP INVITE request
for a priority adhoc group call . 25
6.4.1.14 SIP INVITE request for originating MCPTT emergency adhoc group calls . 25
6.4.1.15 SIP INVITE request for originating MCPTT imminent peril adhoc group calls . 26
6.4.2 MCPTT emergency private call conditions . 26
6.4.2.1 SIP request for originating MCPTT emergency private calls . 26
6.4.2.2 Resource-Priority header field for MCPTT emergency private calls . 26
6.4.2.3 SIP re-INVITE request for cancelling MCPTT emergency private call state . 27
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6.5 Location information . 27
6.5.1 Location information for location reporting . 27
6.6 IWF server role procedures . 28
6.6.1 Distinction of requests sent to the IWF . 28
6.6.1.1 SIP INVITE request . 28
6.6.1.2 SIP MESSAGE request . 28
6.6.1.3 SIP SUBSCRIBE request . 29
6.6.2 IWF participating role . 29
6.6.2.1 Requests initiated by a participant homed in the IWF . 29
6.6.2.1.1 SDP offer generation . 29
6.6.2.1.2 Sending an INVITE request . 30
6.6.2.1.3 IWF sending a SIP BYE request . 31
6.6.2.1.4 Priority call conditions . 31
6.6.2.1.5 Sending a SIP INVITE request on receipt of SIP 3xx response . 32
6.6.2.2 Requests terminated to the IWF . 33
6.6.2.2.1 SDP offer generation . 33
6.6.2.2.2 SIP BYE request towards the terminating IWF . 33
6.6.3 IWF controlling role . 33
6.6.3.1 Requests initiated by the IWF performing the controlling role . 33
6.6.3.1.1 Sending an INVITE request . 33
6.6.3.1.2 Sending a SIP BYE request . 34
6.6.3.1.3 Sending a SIP re-INVITE request for MCPTT emergency group call . 34
6.6.3.1.4 Sending a SIP INVITE request for MCPTT emergency group call . 35
6.6.3.1.5 Sending a SIP UPDATE request for Resource-Priority header field correction. 36
6.6.3.1.6 Generating a SIP re-INVITE request to cancel an in-progress emergency . 37
6.6.3.1.7 Populate mcptt-info and location-info MIME bodies for emergency alert . 37
6.6.3.1.8 Authorisations . 38
6.6.3.1.9 Generating a SIP 403 response for priority call request rejection . 41
6.6.3.1.10 Handling the expiry of timer TNG2 (in-progress emergency group call timer) . 41
6.6.3.1.11 Sending a SIP INFO request in the dialog of a SIP request for a priority call . 42
6.6.3.1.12 Retrieving Resource-Priority header field values . 42
6.6.3.2 Requests terminated by the IWF performing the controlling role . 42
6.6.3.2.1 Receiving a SIP BYE request . 42
6.6.3.3 Handling of the acknowledged call setup timer (TNG1) . 43
6.6.3.4 Generating a SIP NOTIFY request . 45
6.6.3.5 Handling of the group call timer (TNG3) . 46
6.6.3.5.1 General . 46
6.6.3.5.2 Interaction with the in-progress emergency group call timer (TNG2) . 46
6.6.4 IWF non-controlling role . 47
6.6.4.1 Request initiated by the IWF performing the non-controlling role of a group . 47
6.6.4.1.1 SDP offer generation . 47
6.6.4.1.2 Sending an INVITE request towards the MCPTT client . 47
6.6.4.1.3 Sending a SIP INFO request . 48
6.6.4.1.4 Sending an INVITE request towards the controlling MCPTT function . 49
6.6.4.2 Requests terminated by the non-controlling MCPTT function of an MCPTT group . 50
6.6.4.2.1 SDP answer generation . 50
6.6.4.2.2 Sending a SIP response to the SIP INVITE request . 50
6.6.4.3 Generating a SIP NOTIFY request . 51
6.6.5 Retrieving and processing a group document . 52
6.6.5.1 General . 52
6.6.5.2 Rules for joining a group session . 52
6.6.5.3 Determining the group members to invite . 52
6.6.6 Error handling . 52
6.6.6.1 Public service identity does not exist . 52
6.6.7 Session release policy . 52
6.6.7.1 Session release policy for group call . 52
6.6.7.2 Session release policy for private call . 53
6.7 Implicit floor request . 53
6.8 Confidentiality and Integrity Protection . 53
6.8.1 General . 53
6.8.1.1 Applicability and exclusions . 53
6.8.1.2 Performing XML content encryption . 53
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6.8.1.3 Performing integrity protection on an XML body . 53
6.8.1.4 Keys used in confidentiality protection procedures . 54
6.8.2 Confidentiality Protection . 54
6.8.2.1 Procedures for sending confidentiality protected content . 54
6.8.2.1.1 IWF performing any role of an MCPTT server . 54
6.8.2.2 IWF copying received XML content. 54
6.8.3 Integrity Protection of XML documents . 55
6.8.3.1 Keys used in integrity protection procedures . 55
6.8.3.2 Integrity protection at the IWF . 55
6.9 Priority sharing . 55
6.10 Void . 56
7 Registration and service authorisation . 56
8 Pre-established session . 56
9 Affiliation . 56
9.1 General . 56
9.2 Procedures . 57
9.2.1 IWF procedures towards the MCPTT system . 57
9.2.1.1 General . 57
9.2.1.2 Procedures towards the MCPTT system of an IWF serving the user homed in the IWF . 57
9.2.1.2.1 General . 57
9.2.1.2.2 Stored information . 57
9.2.1.2.3 Procedure for handling affiliation status change of a user homed in the IWF . 57
9.2.1.2.4 Receiving subscription to affiliation status procedure . 60
9.2.1.2.5 Sending notification of change of affiliation status procedure . 60
9.2.1.2.6 Sending affiliation status change towards MCPTT server owning MCPTT group procedure . 61
9.2.1.2.7 Affiliation status determination from MCPTT server owning MCPTT group procedure. . 62
9.2.1.2.8 Affiliation status determination . 65
9.2.1.2.9 Affiliation status change by implicit affiliation . 65
9.2.1.2.10 Implicit affiliation status change completion . 67
9.2.1.2.11 Implicit affiliation status change cancellation . 67
9.2.1.2.12 Automatic affiliation to configured groups procedure. 67
9.2.1.3 Procedures of MCPTT server owning the MCPTT group . 67
9.2.1.3.1 General . 67
9.2.1.3.2 Stored information . 68
9.2.1.3.3 Receiving group affiliation status change procedure . 68
9.2.1.3.4 Receiving subscription to affiliation status procedure . 69
9.2.1.3.5 Sending notification of change of affiliation status procedure . 70
9.2.1.3.6 Implicit affiliation eligibility check procedure . 71
9.2.1.3.7 Affiliation status change by implicit affiliation procedure . 71
9.2.1.3.8 Affiliation eligibility check procedure . 72
9.2.1.3.9 Receiving subscription to group dynamic data procedure . 72
9.2.1.3.10 Sending notification of change of group dynamic data procedure . 73
10 Call signalling - group call . 73
10.1 Prearranged group call . 73
10.1.2 Client derived procedures . 73
10.1.2.1 IWF originating procedures . 73
10.1.2.2 IWF performing the participating role terminating procedures . 75
10.1.2.3 MCPTT upgrade to in-progress emergency or imminent peril . 76
10.1.2.4 MCPTT in-progress emergency cancel . 76
10.1.2.5 MCPTT in-progress imminent peril cancel . 78
10.1.2.6 Reception of SIP re-INVITE request . 78
10.1.3 IWF participating role procedures . 79
10.1.3.1 Originating procedures . 79
10.1.3.1.1 On demand prearranged group call. 79
10.1.3.1.2 Sending of a SIP re-INVITE request towards MCPTT controlling function . 80
10.1.3.2 Terminating Procedures . 81
10.1.3.3 IWF participating role ending group call . 82
10.1.3.3.1 IWF ending group call on-demand . 82
10.1.3.4 End group call at the IWF performing the participating role . 82
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10.1.3.4.1 Receipt of SIP BYE request for private call on-demand . 82
10.1.3.5 Re-join procedures . 82
10.1.3.5.1 Originating procedures - on demand prearranged group call . 82
10.1.3.6 Reception of a SIP re-INVITE request for terminating a priority call . 82
10.1.4 IWF Controlling role procedures . 83
10.1.4.1 Originating Procedures . 83
10.1.4.1.1 INVITE targeted to an MCPTT client . 83
10.1.4.1.2 INVITE targeted to the non-controlling MCPTT function of an MCPTT group . 84
10.1.4.2 Terminating Procedures . 85
10.1.4.3 End group call at the IWF performing the terminating controlling role . 93
10.1.4.4 End group call initiated by the IWF performing the controlling role . 93
10.1.4.4.1 General . 93
10.1.4.4.2 SIP BYE request for releasing MCPTT session for a group call . 93
10.1.4.4.3 SIP BYE request towards a MCPTT client . 93
10.1.4.5 Re-join procedures . 94
10.1.4.5.1 Terminating procedures . 94
10.1.4.6 Late call entry initiated by IWF performing the controlling role . 95
10.1.4.7 Receipt of a SIP re-INVITE request . 95
10.1.4.8 Handling of a SIP re-INVITE request for imminent peril session . 98
10.1.5 Non-controlling role procedures . 100
10.1A Adhoc group call . 100
10.1A.1 Client derived procedures . 100
10.1A.1.1 IWF originating procedures . 100
10.1A.1.2 IWF terminating procedures. 102
10.1A.2 IWF participating role procedures . 103
10.1A.2.1 Originating procedures . 103
10.1A.2.1.1 Adhoc group call . 103
10.1A.2.2 Terminating Procedures . 104
10.1A.2.3 IWF participating role ending adhoc group call . 104
10.1A.2.3.1 IWF ending adhoc group call on-demand. 104
10.1.2.4 End adhoc group call at the IWF . 105
10.1A.2.4.1 Receipt of SIP BYE request for on demand adhoc group call . 105
10.1A.3 IWF controlling role procedures . 105
10.1A.4 IWF non-controlling role procedures . 105
10.2 Chat group (restricted) call . 105
10.2.1 Client derived procedures . 105
10.2.1.1 On-demand chat group call . 105
10.2.1.1.1 Procedure for initiating an MCPTT chat group session and procedure for joining an MCPTT

chat group session. 105
10.2.1.1.2 IWF performing the terminating participating role receives SIP re-INVITE request for an
MCPTT chat group . 106
10.2.1.1.3 MCPTT in-progress emergency cancel . 107
10.2.1.1.4 MCPTT upgrade to in-progress emergency or imminent peril . 108
10.2.1.1.5 MCPTT in-progress imminent peril cancel . 109
10.2.1.1.6 IWF performing the terminating participating role receives a SIP INVITE request for an
MCPTT chat group call . 109
10.2.2 IWF performing the participating role procedures . 110
10.2.2.1 On-demand chat group call . 110
10.2.2.1.1 MCPTT chat session establishment . 110
10.2.2.1.2 Sending of a SIP re-INVITE request towards the MCPTT controlling function . 111
10.2.2.1.3 Reception of a SIP INVITE request by an IWF performing the terminating participating role . 112
10.2.2.1.4 Reception of a SIP re-INVITE request by an IWF performing the terminating participating
role . 113
10.2.2.2 End group call at the originating participating IWF . 113
10.2.2.2.1 IWF ending on-demand chat session . 113
10.2.2.3 End group call at the terminating participating IWF . 113
10.2.2.3.1 Receipt of SIP BYE request for on-demand chat session . 113
10.2.3 IWF controlling role procedures . 113
10.2.3.1 On-demand chat group call . 113
10.2.3.1.1 Procedure for establishing an MCPTT chat session and procedure for joining an established
MCPTT chat session . 113
10.2.3.1.2 Receipt of a SIP re-INVITE request . 117
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10.2.3.1.3 Handling of a SIP re-INVITE request for imminent peril session . 121
10.2.3.2 End group call at the terminating IWF performing the controlling role . 123
10.2.3.3 End group call initiated by the IWF performing the controlling role . 123
10.2.3.3.1 General . 123
10.2.3.3.2 SIP BYE request for releasing MCPTT session for a group call . 124
10.2.3.3.3 SIP BYE request towards a MCPTT client . 124
10.2.3.3.4 Removal of participant homed in the IWF . 124
10.2.4 Non-controlling role procedures . 124
10.3 Subscription to the conference event package . 124
10.3.1 General . 124
10.3.2 IWF performing the participating role . 124
10.3.3 IWF performing the controlling role . 125
10.3.3.1 Receiving a subscription to the conference event package . 125
10.3.3.2 Sending notifications to the conference event package . 126
10.3.3.3 Sending subscriptions to the conference event package . 126
10.3.3.4 Terminating a subscription . 127
10.3.4 IWF performing the non-controlling role . 127
10.4 Remotely initiated group call . 127
10.4.1 Participating MCPTT function procedures . 127
10.4.1.1 IWF performing the participating role . 127
10.4.1.1.1 Originating procedures . 127
10.4.1.1.2 Terminating procedures . 128
10.4.1.2 IWF performing the controlling role . 128
11 Private call call control . 128
11.1 Private call with floor control . 128
11.1.1 Client derived procedures .
...