ETSI TS 124 281 V16.12.0 (2026-03)

LTE; Mission Critical Video (MCVideo) signalling control; Protocol specification (3GPP TS 24.281 version 16.12.0 Release 16)

RTS/TSGC-0124281vgc0

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;
Mission Critical Video (MCVideo) signalling control;
Protocol specification
(3GPP TS 24.281 version 16.12.0 Release 16)

3GPP TS 24.281 version 16.12.0 Release 16 1 ETSI TS 124 281 V16.12.0 (2026-03)

Reference
RTS/TSGC-0124281vgc0
Keywords
LTE
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ETSI
3GPP TS 24.281 version 16.12.0 Release 16 2 ETSI TS 124 281 V16.12.0 (2026-03)
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ETSI
3GPP TS 24.281 version 16.12.0 Release 16 3 ETSI TS 124 281 V16.12.0 (2026-03)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 18
1 Scope . 19
2 References . 19
3 Definitions, symbols and abbreviations . 22
3.1 Definitions . 22
3.2 Symbols . 24
3.3 Abbreviations . 24
4 General . 25
4.1 MCVideo overview . 25
4.2 URI and address assignments . 26
4.3 MCVideo media . 26
4.4 Warning header field . 26
4.4.1 General . 26
4.4.2 Warning texts . 26
4.5 MCVideo session identity . 31
4.6 MCVideo priority calls and alerts . 31
4.6.1 MCVideo emergency group calls . 31
4.6.2 MCVideo emergency private calls . 32
4.6.3 MCVideo emergency alerts . 34
4.6.4 MCVideo imminent peril group call . 35
4.7 Communication security . 36
4.7.1 Media security . 36
4.7.2 Signalling security . 36
4.8 Protection of sensitive application data. . 37
4.9 MCVideo client ID . 37
4.10 Off-network MCVideo . 38
5 Functional entities . 38
5.1 General . 38
5.2 MCVideo client . 38
5.3 MCVideo server . 39
5.3.1 General . 39
5.3.2 Functional connectivity models . 40
5.3.3 Failure case . 41
5.4 MCVideo UE-to-network relay . 41
6 Common procedures. 41
6.1 Introduction . 41
6.2 MCVideo client procedures . 42
6.2.0 Distinction of requests at the MCVideo client . 42
6.2.0.1 SIP MESSAGE request . 42
6.2.1 SDP offer generation . 42
6.2.2 SDP answer generation . 43
6.2.3 Commencement modes . 44
6.2.3.1 Automatic commencement mode . 44
6.2.3.1.1 Automatic commencement mode for private calls . 44
6.2.3.1.2 Automatic commencement mode for group calls . 45
6.2.3.2 Manual commencement mode . 45
6.2.3.2.1 Manual commencement mode for private calls . 45
6.2.3.2.2 Manual commencement mode for group calls . 45
6.2.4 Leaving an MCVideo session initiated by MCVideo client . 46
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6.2.4.1 On-demand session case . 46
6.2.5 Releasing an MCVideo session initiated by MCVideo client . 46
6.2.5.1 On-demand session case . 46
6.2.5.2 Pre-established session case . 46
6.2.6 Receiving an MCVideo session release request. 47
6.2.7 Void . 47
6.2.8 Priority call conditions . 47
6.2.8.0 General . 47
6.2.8.1 MCVideo emergency group call conditions . 47
6.2.8.1.1 SIP INVITE request for originating MCVideo emergency group calls . 47
6.2.8.1.2 Resource-Priority header field for MCVideo emergency group calls . 48
6.2.8.1.3 SIP re-INVITE request for cancelling MCVideo in-progress emergency group state. 48
6.2.8.1.4 Receiving a SIP 2xx response to a SIP request for a priority call . 49
6.2.8.1.5 Receiving a SIP 4xx response, SIP 5xx response or SIP 6xx response to a SIP request for a

priority group call . 50
6.2.8.1.6 Determining authorisation for initiating or cancelling an MCVideo emergency alert. 50
6.2.8.1.7 Determining authorisation for cancelling the in-progress emergency state of an MCVideo
group . 51
6.2.8.1.8 Determining authorisation for originating a priority group call . 51
6.2.8.1.9 SIP request for originating MCVideo imminent peril group calls . 52
6.2.8.1.10 Determining authorisation for cancelling an imminent peril group call . 52
6.2.8.1.11 SIP re-INVITE request for cancelling MCVideo in-progress imminent peril group state . 52
6.2.8.1.12 Resource-Priority header field for MCVideo imminent peril group calls . 53
6.2.8.1.13 Receiving a SIP INFO request in the dialog of a SIP request for a priority group call . 53
6.2.8.1.14 SIP re-INVITE request for cancelling the in-progress emergency group state of a group by a
third-party . 54
6.2.8.1.15 Retrieving Resource-Priority header field values . 54
6.2.8.1.16 Resource-priority header field namespaces for MCVideo . 55
6.2.8.1.17 Priority group call conditions upon receiving call release . 55
6.2.8.1.18 Emergency private call conditions upon receiving call release . 55
6.2.8.2 Request for an originating broadcast group call . 56
6.2.8.3 MCVideo emergency private call conditions . 56
6.2.8.3.1 Authorisations . 56
6.2.8.3.2 SIP request for originating MCVideo emergency private calls . 57
6.2.8.3.3 Resource-Priority header field for MCVideo emergency private calls . 57
6.2.8.3.4 Receiving a SIP 2xx response to a SIP request for an MCVideo emergency private call . 58
6.2.8.3.5 Receiving a SIP 4xx response, SIP 5xx response or SIP 6xx response to a SIP request for an
MCVideo emergency private call . 58
6.2.8.3.6 SIP re-INVITE request for cancelling MCVideo emergency private call state . 58
6.2.8.3.7 Receiving a SIP INFO request in the dialog of a SIP request for a priority private call. 59
6.2.8.3.8 SIP re-INVITE request for cancelling the MCVideo emergency private call state by a third-
party . 60
6.2.8.3.9 Retrieving a KMS URI associated with an MCVideo ID . 60
6.2.9 Location information . 61
6.2.9.1 Location information for location reporting . 61
6.3 MCVideo server procedures . 61
6.3.1 Distinction of requests sent to the MCVideo server . 61
6.3.1.1 SIP INVITE request . 61
6.3.1.2 SIP MESSAGE request . 62
6.3.1.3 SIP SUBSCRIBE request . 63
6.3.2 Participating MCVideo Function . 64
6.3.2.1 Requests initiated by the served MCVideo user. 64
6.3.2.1.1 SDP offer generation . 64
6.3.2.1.2 SDP answer generation . 64
6.3.2.1.3 Sending an INVITE request on receipt of an INVITE request . 65
6.3.2.1.4 Response to an INVITE request . 65
6.3.2.1.5 Sending a SIP BYE request on receipt of a SIP BYE request . 66
6.3.2.1.6 Priority call conditions . 66
6.3.2.1.7 Generating a SIP re-INVITE request on receipt of a SIP re-INVITE request . 68
6.3.2.1.8 Sending a SIP INVITE request on receipt of SIP 3xx response . 68
6.3.2.2 Requests terminated to the served MCVideo user . 69
6.3.2.2.1 SDP offer generation . 69
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6.3.2.2.2 SDP answer generation . 69
6.3.2.2.3 SIP INVITE request towards the terminating MCVideo client . 69
6.3.2.2.4 Response to a SIP INVITE request . 70
6.3.2.2.5 Automatic Commencement Mode . 71
6.3.2.2.6 Manual Commencement Mode . 73
6.3.2.2.7 Void . 74
6.3.2.2.8 SIP BYE request towards the terminating MCVideo client . 74
6.3.2.2.9 Populate MIME bodies . 75
6.3.2.2.10 Generating a SIP re-INVITE request towards the terminating MCVideo client . 75
6.3.2.2.11 Generating a SIP MESSAGE request towards the terminating MCVideo client . 75
6.3.2.3 Processing I_MESSAGEs containing MKFC and MKFC-ID . 76
6.3.2.3.1 General . 76
6.3.2.3.2 Processing an I_MESSAGE containing MKFC and MKFC-ID . 76
6.3.3 Controlling MCVideo function . 76
6.3.3.1 Request initiated by the controlling MCVideo function . 76
6.3.3.1.1 SDP offer generation . 76
6.3.3.1.2 Sending an INVITE request . 77
6.3.3.1.3 Receipt of a SIP response to a SIP INVITE request . 78
6.3.3.1.4 Sending a SIP BYE request . 78
6.3.3.1.5 Sending a SIP re-INVITE request for MCVideo emergency group call . 78
6.3.3.1.6 Sending a SIP INVITE request for MCVideo emergency group call . 79
6.3.3.1.7 Sending a SIP UPDATE request for Resource-Priority header field correction. 80
6.3.3.1.8 Generating a SIP re-INVITE request . 81
6.3.3.1.9 Generating a SIP re-INVITE request to cancel an in-progress emergency . 81
6.3.3.1.10 Generating a SIP MESSAGE request for notification of in-progress emergency or imminent
peril status change . 81
6.3.3.1.11 Populate mcvideo-info and location-info MIME bodies for emergency alert . 82
6.3.3.1.12 Authorisations . 83
6.3.3.1.13 Generating a SIP 403 response for priority call request rejection . 86
6.3.3.1.14 Sending a SIP re-INVITE request for MCVideo imminent peril group call . 86
6.3.3.1.15 Handling the expiry of timer TNG2 (in-progress emergency group call timer) . 87
6.3.3.1.16 Validate priority request parameters . 87
6.3.3.1.17 Sending a SIP INFO request in the dialog of a SIP request for a priority call . 88
6.3.3.1.18 Retrieving Resource-Priority header field values . 88
6.3.3.1.19 Generating a SIP MESSAGE request to indicate successful receipt of an emergency alert or
emergency cancellation . 89
6.3.3.2 Requests terminated by the controlling MCVideo function . 89
6.3.3.2.1 SDP answer generation . 89
6.3.3.2.2 Receipt of a SIP INVITE request . 89
6.3.3.2.3 Sending a SIP response to a SIP INVITE request . 90
6.3.3.2.4 Receiving a SIP BYE request . 91
6.3.3.3 Handling of the acknowledged call setup timer (TNG1) . 91
6.3.3.4 Generating a SIP NOTIFY request . 93
6.3.3.5 Handling of the group call timer (TNG3) . 94
6.3.3.5.1 General . 94
6.3.3.5.2 Interaction with the in-progress emergency group call timer (TNG2) . 95
6.3.3.6 Generation of I_MESSAGEs containing MKFC and MKFC-ID . 95
6.3.3.6.1 General . 95
6.3.3.6.2 Creation of an I_MESSAGE containing MKFC . 95
6.3.4 Non-controlling MCVideo function of an MCVideo group . 96
6.3.4.1 Request initiated by the non-controlling MCVideo function of an MCVideo group . 96
6.3.4.1.1 SDP offer generation . 96
6.3.4.1.2 Sending an INVITE request towards the MCVideo client . 96
6.3.4.1.3 Sending a SIP INFO request . 97
6.3.4.1.4 Sending an INVITE request towards the controlling MCVideo function . 98
6.3.4.2 Requests terminated by the non-controlling MCVideo function of an MCVideo group . 99
6.3.4.2.1 SDP answer generation . 99
6.3.4.2.2 Sending a SIP response to the SIP INVITE request . 99
6.3.4.3 Generating a SIP NOTIFY request . 100
6.3.5 Retrieving and processing a group document . 101
6.3.5.1 General . 101
6.3.5.2 Rules for retrieving Group Document(s) . 101
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6.3.5.3 Rules for joining a group session . 104
6.3.5.4 Rules for initiating a prearranged group session . 105
6.3.5.5 Determining the group members to invite . 105
6.3.6 Affiliation check . 106
6.3.7 Error handling . 106
6.3.7.1 Public service identity does not exist . 106
6.3.8 Session release policy . 106
6.3.8.1 Session release policy for group call . 106
6.3.8.2 Session release policy for private call . 107
6.4 Implicit transmit media request . 107
6.5 Handling of MIME bodies in a SIP message. 107
6.6 Confidentiality and Integrity Protection . 108
6.6.1 General . 108
6.6.1.1 Applicability and exclusions . 108
6.6.1.2 Performing XML content encryption . 108
6.6.1.3 Performing integrity protection on an XML body . 108
6.6.1.4 Verifying integrity of an XML body and decrypting XML elements . 108
6.6.2 Confidentiality Protection . 109
6.6.2.1 General . 109
6.6.2.2 Keys used in confidentiality protection procedures . 109
6.6.2.3 Procedures for sending confidentiality protected content . 109
6.6.2.3.1 MCVideo client . 109
6.6.2.3.2 MCVideo server . 110
6.6.2.3.3 Content Encryption in XML elements . 110
6.6.2.3.4 Attribute URI Encryption . 110
6.6.2.4 Procedures for receiving confidentiality protected content . 111
6.6.2.4.1 Determination of confidentiality protected content . 111
6.6.2.4.2 Decrypting confidentiality protected content in XML elements . 111
6.6.2.4.3 Decrypting confidentiality protected URIs in XML attributes . 111
6.6.2.5 MCVideo server copying received XML content . 112
6.6.3 Integrity Protection of XML documents . 112
6.6.3.1 General . 112
6.6.3.2 Keys used in integrity protection procedures . 114
6.6.3.3 Sending integrity protected content . 114
6.6.3.3.1 MCVideo client . 114
6.6.3.3.2 MCVideo server . 114
6.6.3.3.3 Integrity protection procedure . 115
6.6.3.4 Receiving integrity protected content. 115
6.6.3.4.1 Determination of integrity protected content . 115
6.6.3.4.2 Verification of integrity protected content. 115
6.7 Priority sharing . 116
6.8 Support for multiple devices . 116
7 Registration and service authorisation . 116
7.1 General . 116
7.2 MCVideo client procedures . 116
7.2.1 SIP REGISTER request for service authorisation . 116
7.2.1AA SIP REGISTER request without service authorisation . 118
7.2.1A Common SIP PUBLISH procedure . 118
7.2.2 SIP PUBLISH request for service authorisation and MCVideo service settings . 118
7.2.3 Sending SIP PUBLISH for MCVideo service settings only . 119
7.2.4 Determination of MCVideo service settings . 120
7.2.5 Receiving a CSK key download message . 121
7.3 MCVideo server procedures . 122
7.3.1 General . 122
7.3.1A Confidentiality and Integrity Protection . 122
7.3.2 SIP REGISTER request for service authorisation . 123
7.3.3 SIP PUBLISH request for service authorisation and service settings . 124
7.3.4 Receiving SIP PUBLISH request for MCVideo service settings only . 126
7.3.5 Receiving SIP PUBLISH request with "Expires=0" . 127
7.3.6 Subscription to and notification of MCVideo service settings . 127
7.3.6.1 Receiving subscription to MCVideo service settings . 127
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7.3.6.2 Sending notification of change of MCVideo service settings . 127
7.3.7 Sending a CSK key download message . 128
7.4 Coding . 128
7.4.1 Extension of MIME types . 128
7.4.1.1 General . 128
7.4.1.2 Extension of application/poc-settings+xml MIME type . 128
7.4.1.2.1 Introduction . 128
7.4.1.2.2 Syntax . 128
8 Affiliation . 130
8.1 General . 130
8.2 Procedures . 130
8.2.1 MCVideo client procedures . 130
8.2.1.1 General . 130
8.2.1.2 Affiliation status change procedure . 131
8.2.1.3 Affiliation status determination procedure . 131
8.2.1.4 Procedure for sending affiliation status change request in negotiated mode to target MCVideo
user . 132
8.2.1.5 Procedure for receiving affiliation status change request in negotiated mode from authorized
MCVideo user . 133
8.2.1.6 Subscription to group dynamic data . 133
8.2.2 MCVideo server procedures . 134
8.2.2.1 General . 134
8.2.2.2 Procedures of MCVideo server serving the MCVideo user . 134
8.2.2.2.1 General .
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