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Content for  TS 24.173  Word version:  18.0.0

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M IP-Connectivity Access Network specific concepts when using 5GS to access IM CN subsystem  M.1 Scope  M.2 5GS aspects when connected to the IM CN subsystem  M.3 Application usage of SIP  $ Change history 

 

M (Normative)  IP-Connectivity Access Network specific concepts when using 5GS to access IM CN subsystem |R15|  p. 30

M.1  Scope  p. 30

The present annex defines IP-CAN specific requirements for a multimedia telephony communication service and associated supplementary services in the IP Multimedia (IM) Core Network (CN) subsystem, where the IP-CAN is 5G System (5GS).

M.2  5GS aspects when connected to the IM CN subsystem  p. 30

M.2.1  Procedures at the UE  p. 30

M.2.1.1  Indications to lower layers about start and stop of MMTEL sessions  p. 30

The following information is provided to the non-access stratum:
  • MO-MMTEL-voice-started;
  • MO-MMTEL-voice-ended;
  • MO-MMTEL-video-started;
  • MO-MMTEL-video-ended;
  • MT-MMTEL-voice-started;
  • MT-MMTEL-voice-ended;
  • MT-MMTEL-video-started;
  • MT-MMTEL-video-ended;
  • for 3GPP access only, handover of ongoing MMTEL voice call from non-3GPP access; and
  • for 3GPP access only, handover of ongoing MMTEL video call from non-3GPP access.
Upon request from a user to establish an originating multimedia telephony communication session as described in clause 5.2:
  1. if the multimedia telephony communication session to be established is an emergency session, then skip the rest of steps below and continue with session establishment as described in clause 5.2;
  2. if only audio or only real-time text or only both audio and real-time text (see clause 4.2 for 3GPP systems) are offered in the multimedia telephony communication session, and no other originating multimedia telephony communication session initiated with offering only audio or only real-time text or only both audio and real-time text exists, the UE sends the MO-MMTEL-voice-started indication to the non-access stratum and
    1. if the barring result is "not-barred", continue with session establishment as described in clause 5.2; and
    2. if the barring result is "barred", reject the multimedia telephony communication session establishment and skip the rest of steps below; and
  3. if video is offered in the multimedia telephony communication session, and no other originating multimedia telephony communication session initiated with offering video exists, the UE sends the MO-MMTEL-video-started indication to the non-access stratum and
    1. if the barring result is "not-barred", continue with session establishment as described in clause 5.2; and
    2. if the barring result is "barred", reject the multimedia telephony communication session establishment and skip the rest of steps below.
When a terminating multimedia telephony communication session starts (i.e. an INVITE is received), the terminating multimedia telephony communication session is offering only audio or only real-time text or only both audio and real-time text (i.e. in the SDP offer in the INVITE request), and no other terminating multimedia telephony communication session started with offering only audio or only real-time text or only both audio and real-time text exists, the UE sends the MT-MMTEL-voice-started indication to the non-access stratum.
When a terminating multimedia telephony communication session starts (i.e. an INVITE is received), the terminating multimedia telephony communication session is offering video (i.e. in the SDP offer in the INVITE request), and no other terminating multimedia telephony communication session started with offering video exists, the UE sends the MT-MMTEL-video-started indication to the non-access stratum.
When an originating multimedia telephony communication session ends (i.e. a response to a BYE or a failure response to the initial INVITE request is transferred), the originating multimedia telephony communication session was initiated with offering only audio or only real-time text or only both audio and real-time text (i.e. in the SDP offer in the initial INVITE request), and no other originating multimedia telephony communication session initiated with offering only audio or only real-time text or only both audio and real-time text exists, the UE sends the MO-MMTEL-voice-ended to the non-access stratum.
When an originating multimedia telephony communication session ends (i.e. a response to a BYE or a failure response to the initial INVITE request is transferred), the originating multimedia telephony communication session was initiated with offering video (i.e. in the SDP offer in the initial INVITE request), and no other originating multimedia telephony communication session initiated with offering video exists, the UE sends the MO-MMTEL-video-ended indication to the non-access stratum.
When a terminating multimedia telephony communication session ends (i.e. a response to a BYE or a failure response to the initial INVITE request is transferred), the terminating multimedia telephony communication session was initiated with offering only audio or only real-time text or only both audio and real-time text (i.e. in the SDP offer in the initial INVITE request), and no other terminating multimedia telephony communication session initiated with offering only audio or only real-time text or only both audio and real-time text exists, the UE sends the MT-MMTEL-voice-ended indication to the non-access stratum.
When a terminating multimedia telephony communication session ends (i.e. a response to a BYE or a failure response to the initial INVITE request is transferred), the terminating multimedia telephony communication session was initiated with offering video (i.e. in the SDP offer in the initial INVITE request), and no other terminating multimedia telephony communication session initiated with offering video exists, the UE sends the MT-MMTEL-video-ended indication to the non-access stratum.
When an ongoing originating multimedia telephony communication session is handed over from non-3GPP access to 3GPP access:
  1. if only audio or only real-time text or only both audio and real-time text (see clause 4.2 for 3GPP systems) are used in the multimedia telephony communication session, the UE sends the MO-MMTEL-voice-started indication and the handover of ongoing MMTEL voice call from non-3GPP access indication to the non-access stratum; and
  2. if video is used in the multimedia telephony communication session, the UE sends the MO-MMTEL-video-started indication and the handover of ongoing MMTEL video call from non-3GPP access indication to the non-access stratum.
When an ongoing terminating multimedia telephony communication session is handed over from non-3GPP access to 3GPP access:
  1. if only audio or only real-time text or only both audio and real-time text (see clause 4.2 for 3GPP systems) are used in the multimedia telephony communication session, the UE sends the MT-MMTEL-voice-started indication and the handover of ongoing MMTEL voice call from non-3GPP access indication to the non-access stratum; and
  2. if video is used in the multimedia telephony communication session, the UE sends the MT-MMTEL-video-started indication and the handover of ongoing MMTEL video call from non-3GPP access indication to the non-access stratum.
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M.2.1.2  MMTEL request timeouts  p. 32

If the UE supports timer RequestTimeout, then upon a request from a user to establish an originating multimedia telephony communication session as described in clause 5.2, the UE shall start timer RequestTimeout when sending an initial INVITE request.
The UE may support being configured for the RequestTimeout timer with the operator's IMS multimedia telephony communication service policy as specified in TS 24.275.
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M.2.1.2A  Registration and authentication  p. 32

If:
  1. the UE includes a "+g.3gpp.icsi-ref" header field parameter equal to "urn:urn-7:3gpp-service.ims.icsi.mmtel" in the Contact header field of the SIP REGISTER request; and
  2. the IP-CAN of 5GS indicated that interworking without N26 is supported as specified in TS 24.501;
the UE should include a transport=tcp URI parameter in the Contact header field of the SIP REGISTER request.
If:
  1. the UE changes from another IP-CAN to an IP-CAN of 5GS; and
  2. the IP-CAN of 5GS indicated that interworking without N26 is supported as specified in TS 24.501;
the UE may perform re-registration of a previously registered public user identity bound to the other IP-CAN. In this case, if the UE includes a "+g.3gpp. icsi-ref" header field parameter equal to "urn:urn-7:3gpp-service.ims.icsi.mmtel" in the Contact header field of the SIP REGISTER request, the UE should include a transport=tcp URI parameter in the Contact header field of the SIP REGISTER request.
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M.2.1.3  Abnormal cases  p. 32

Upon request from a user to establish an MMTEL voice or an MMTEL video session as described in clause 5.2, if
  1. the UE receives, from the lower layers, a notification that the service request
    1. was not accepted due to congestion; or
    2. resulted in starting timer T3525 (see TS 24.501); and
  2. an originating initial INVITE transaction, for which a 2xx response has not yet been received, exists;
then:
  1. if a provisional response has been received, the UE shall cancel the INVITE transaction; and
  2. if an alternative radio access network is available, the UE shall attempt the MMTEL voice or an MMTEL video session on the alternative radio access network.
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M.3  Application usage of SIP  p. 33

M.3.1  Procedures at the UE  p. 33

M.3.1.1  3GPP PS data off  p. 33

M.3.1.1.1  General  p. 33
The requirements in clause J.3.1.1.1 apply.
Additionally, the following requirements apply.
In case of SNPN, if the UE supports the 3GPP PS data off:
  1. the UE can be configured with:
    1. up to two indications of whether the MMTEL voice is a 3GPP PS data off exempt service for each subscribed SNPN whose entry exists in the "list of subscriber data", one indication is valid for the UE camping in the subscribed SNPN, and the other indication is valid for any non-subscribed SNPN the UE is camping in using the subscribed SNPN's credentials;
    2. up to two indications of whether the MMTEL video is a 3GPP PS data off exempt service for each subscribed SNPN whose entry exists in the "list of subscriber data", one indication is valid for the UE camping in the subscribed SNPN, and the other indication is valid for any non-subscribed SNPN the UE is camping in using the subscribed SNPN's credentials;
    3. an indication of whether the MMTEL voice is a 3GPP PS data off exempt service for PLMN subscription, valid for any non-subscribed SNPN the UE is camping in using the PLMN subscription; and
    4. an indication of whether the MMTEL video is a 3GPP PS data off exempt service for PLMN subscription, valid for any non-subscribed SNPN the UE is camping in using the PLMN subscription;
  2. for a subscribed SNPN whose entry exists in the "list of subscriber data", the UE may support being configured with the indication of whether the MMTEL voice is a 3GPP PS data off exempt service using one or more of the following methods:
    1. the MMTEL_voice_exempt node of TS 24.275, if the UE is in the subscribed SNPN; and
    2. the MMTEL_voice_exempt_non_subscribed_SNPN node of TS 24.275, if the UE is in the non-subscribed SNPN.
    For PLMN subscription, the UE may support being configured with the indication of whether the MMTEL voice is a 3GPP PS data off exempt service using the following method:
    1. the MMTEL_voice_exempt_non_subscribed_SNPN node of TS 24.275, if the UE is in the non-subscribed SNPN; and
  3. for a subscribed SNPN whose entry exists in the "list of subscriber data", the UE may support being configured with the indication of whether the MMTEL video is a 3GPP PS data off exempt service using one or more of the following methods:
    1. the MMTEL_video_exempt node of TS 24.275, if the UE is in the subscribed SNPN; and
    2. the MMTEL_video_exempt_non_subscribed_SNPN node of TS 24.275, if the UE is in the non-subscribed SNPN.
    For PLMN subscription, the UE may support being configured with the indication of whether the MMTEL video is a 3GPP PS data off exempt service using the following method:
    1. the MMTEL_video_exempt_non_subscribed_SNPN node of TS 24.275, if the UE is in the non-subscribed SNPN.
When the UE is only configured with the indication valid for the UE camping in the subscribed SNPN, the UE shall use this indication also when the UE is in the non-subscribed SNPN.
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M.3.1.1.2  Enforcement  p. 34
If the 3GPP PS data off status is "active":
  1. the UE shall release according to TS 24.229 any multimedia telephony communication session as described in clause 5.2, which is not an IMS emergency call, established with a UE's contact address containing an IP address associated with a 5GS QoS flow using NG-RAN, with media streams:
    1. other than only audio;
    2. other than only real-time text;
    3. other than only audio and real-time text; and
    4. not including video;
  2. the UE shall not send according to TS 24.229 a SIP message related to a multimedia telephony communication session as described in clause 5.2, which is not an IMS emergency call, from a UE's contact address containing an IP address associated with a 5GS QoS flow using NG-RAN, and with:
    1. an SDP offer; or
    2. an SDP answer;
    with media streams:
    1. other than only audio;
    2. other than only real-time text;
    3. other than only audio and real-time text; and
    4. not including video;
  3. if the UE is not configured with indication that MMTEL voice is a 3GPP PS data off exempt service:
    1. the UE shall release according to TS 24.229 any multimedia telephony communication session as described in clause 5.2, which is not an IMS emergency call, established with a UE's contact address containing an IP address associated with an 5GS QoS flow using NG-RAN, with only audio, only real-time text or only audio and real-time text; and
    2. the UE shall not send according to TS 24.229 a SIP message related to a multimedia telephony communication session as described in clause 5.2, which is not an IMS emergency call, from a UE's contact address containing an IP address associated with a 5GS QoS flow using NG-RAN and with:
      1. an SDP offer; or
      2. an SDP answer;
      with only audio, only real-time text or only audio and real-time text;
  4. if the UE is not configured with indication that MMTEL video is a 3GPP PS data off exempt service:
    1. the UE shall release according to TS 24.229 any multimedia telephony communication session as described in clause 5.2, which is not an IMS emergency call, established with a UE's contact address containing an IP address associated with a 5GS QoS flow using NG-RAN, and with video;
    2. the UE shall not send according to TS 24.229 a SIP message related to a multimedia telephony communication session as described in clause 5.2, which is not an IMS emergency call, from a UE's contact address containing an IP address associated with a 5GS QoS flow using NG-RAN and with:
      1. an SDP offer; or
      2. an SDP answer;
      with video; and
  5. if the UE is not configured with indication that MMTEL voice is a 3GPP PS data off exempt service and the UE is not configured with indication that MMTEL video is a 3GPP PS data off exempt service:
    1. the UE shall de-register the binding of a UE's contact address containing an IP address associated with an 5GS QoS flow using NG-RAN from IM CN subsystem according to TS 24.229;
    2. the UE shall re-register the binding of a UE's contact address containing an IP address associated with an 5GS QoS flow using NG-RAN with IM CN subsystem with a Contact header field without the g.3gpp.icsi-ref media feature tag; or
    3. the UE shall re-register the binding of a UE's contact address containing an IP address associated with an 5GS QoS flow with IM CN subsystem with a Contact header field with the g.3gpp.icsi-ref media feature tag not including the urn:urn-7:3gpp-service.ims.icsi.mmtel ICSI according to TS 24.229.
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M.3.1.2  Establishing an MMTEL session  p. 35

If the UE is establishing an MMTEL session offering audio and if the IP-CAN of 5GS indicated that interworking without N26 is supported as specified in TS 24.501, the UE should transmit the SIP INVITE request using TCP as transport protocol.

M.3.2  Procedures at the multimedia telephony application server  p. 35

M.3.2.1  3GPP PS data off  p. 35

The requirements in clause J.3.2.1 apply.
Additionally, the following requirements apply.
When serving a UE in an SNPN using an entry of "list of subscriber data", a multimedia telephony application server supporting the 3GPP PS data off can be configured with:
  1. up to two indications of whether the MMTEL voice is a 3GPP PS data off exempt service, one indication is valid for the UE camping in the subscribed SNPN, and the other indication is valid for any non-subscribed SNPN the UE is camping in using the subscribed SNPN's credentials; and
  2. up to two indications of whether the MMTEL video is a 3GPP PS data off exempt service, one indication is valid for the UE camping in the subscribed SNPN, and the other indication is valid for any non-subscribed SNPN the UE is camping in using the subscribed SNPN's credentials.
When the multimedia telephony application server is only configured with the indication valid for the UE camping in the subscribed SNPN, the multimedia telephony application server shall use this indication also when the UE is in the non-subscribed SNPN.
When serving a UE in an SNPN using PLMN subscription, a multimedia telephony application server supporting the 3GPP PS data off can be configured with:
  1. an indication of whether the MMTEL voice is a 3GPP PS data off exempt service, valid for any non-subscribed SNPN the UE is camping in using the PLMN subscription; and
  2. an indication of whether the MMTEL video is a 3GPP PS data off exempt service, valid for any non-subscribed SNPN the UE is camping in using the PLMN subscription.
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$  Change history  p. 37

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