Content for TS 24.173 Word version: 18.0.0

1… 4… J… K… M…

J.1 Scope J.2 EPS aspects when connected to the IM CN subsystem J.3 Application usage of SIP
...

J (Normative) IP-Connectivity Access Network specific concepts when using EPS to access IM CN subsystem |R9| p. 18

J.1 Scope p. 18

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 Evolved Packet System (EPS).

J.2 EPS aspects when connected to the IM CN subsystem p. 18

J.2.1 Procedures at the UE p. 18

J.2.1.1 Service Specific Access Control p. 18

The following information is provided by lower layer:

BarringFactorForMMTEL-Voice: barring rate for MMTEL voice;
BarringTimeForMMTEL-Voice: barring timer for MMTEL voice;
BarringFactorForMMTEL-Video: barring rate for MMTEL video; and
BarringTimeForMMTEL-Video: barring timer for MMTEL video.

Upon request from a user to establish a multimedia telephony communication session as described in clause 5.2, the UE shall:

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;
retrieve SSAC related information mentioned above from lower layers;

NOTE 1:
The values of SSAC related information retrieved from lower layers can depend on whether the UE has an Access Class with a value in the range 11..15 or not. Determination of the values of the SSAC related information is described in clause 5.3.3.10 of TS 36.331.
if video is offered in the multimedia telephony communication session:
1. if back-off timer Tx is running, reject the multimedia telephony communication session establishment and skip the rest of steps below; or
2. else, then:
  1. draw a new random number "rand1" that is uniformly distributed in the range 0 ≤ rand1 < 1; and
  2. if the random number "rand1" is lower than BarringFactorForMMTEL-Video, then skip the rest of steps below and continue with session establishment as described in clause 5.2;
    
    NOTE 2:
    If the BarringFactorForMMTEL-Video is set to 1, the session is exempted from barring.
  3. else, then;
    1. draw a new random number "rand2" that is uniformly distributed in the range 0 ≤ rand2 < 1; and
    2. start back-off timer Tx with the timer value calculated using the formula:
      Tx = (0,7 + 0,6*rand2) * BarringTimeForMMTEL-Video; and
    3. reject the multimedia telephony communication session establishment and skip the rest of steps below;
if audio is offered in the multimedia telephony communication session:
1. if back-off timer Ty is running, reject the multimedia telephony communication session establishment and skip the rest of steps below; or
2. else, then;
  1. draw a new random number "rand3" that is uniformly distributed in the range 0 ≤ rand3 < 1; and
  2. if the random number "rand3" is lower than BarringFactorForMMTEL-Voice, then skip the rest of steps below and continue with session establishment as described in clause 5.2;
    
    NOTE 3:
    If the BarringFactorForMMTEL-Voice is set to 1, the session is exempted from barring.
  3. else, then;
    1. draw a new random number "rand4" that is uniformly distributed in the range 0 ≤ rand4 < 1; and
    2. start timer Ty with the timer value calculated using the fomula:
      Ty = (0,7 + 0,6*rand4) * BarringTimeForMMTEL-Voice; and
    3. reject the multimedia telephony communication session establishment;
  NOTE 4:
  If the multimedia telephony communication implemenation and the access stratum protocol implementation are located in separate physical entities, it is expected that the interconnecting protocol supports the transfer of information elements needed for the service specific access control enforcement.

Service Specific Access Control is not activated when the UE is in other radio accesses (e.g. UTRAN/GERAN). And when UE camping on E-UTRAN moves to other radio accesses (e.g. UTRAN/GERAN), back-off timer (Tx or Ty or both) shall be stopped if running.

J.2.1.2 Smart Congestion Mitigation |R12| p. 19

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; and
MT-MMTEL-video-ended.

Upon request from a user to establish an originating multimedia telephony communication session as described in clause 5.2, and if the session establishment is continued after performing the Service Specific Access Control as specified in clause J.2.1.1:

if only audio or only real-time text or only both audio and real-time text (see clause 4.2 for 3GPP systems) are 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 continue with session establishment as described in clause 5.2;
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 continue with session establishment as described in clause 5.2.

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.

J.2.1.3 MMTEL request timeouts |R14| p. 20

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.

J.2.1.4 Abnormal cases |R15| p. 20

Upon request from a user to establish a MMTEL voice or an MMTEL video session as described in clause 5.2, if:

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 T3325 (see TS 24.008); and
an originating initial INVITE transaction, for which a 2xx response has not yet been received, exists;

then:

if a provisional response has been received, the UE shall cancel INVITE transaction; and
if an alternative radio access network is available:
1. if the service request was not accepted due to congestion, the UE shall attempt the MMTEL voice or an MMTEL video session on the alternative radio access network; or
2. if the service request resulted in starting timer T3325, the UE should attempt the MMTEL voice or an MMTEL video session on the alternative radio access network.

J.3 Application usage of SIP |R14| p. 22

J.3.1 Procedures at the UE p. 22

J.3.1.1 3GPP PS data off p. 22

J.3.1.1.1 General p. 22

The UE may support the 3GPP PS data off.

If the UE supports the 3GPP PS data off:

the UE can be configured with:
1. up to two indications whether the MMTEL voice is a 3GPP PS data off exempt service, one indication is valid for the UE camping in the HPLMN or the EHPLMN, and the other indication is valid for any VPLMN the UE is roaming in; and
2. up to two indications whether the MMTEL video is a 3GPP PS data off exempt service, one indication is valid for the UE camping in the HPLMN or the EHPLMN, and the other indication is valid for any VPLMN the UE is roaming in;
the UE may support being configured with the indication whether the MMTEL voice is a 3GPP PS data off exempt service using one or more of the following methods:
1. the EF3GPPPSDATAOFF described in TS 31.102;
2. the MMTEL_voice_exempt node of TS 24.275, if the UE is in the HPLMN or the EHPLMN; and
3. the MMTEL_voice_roaming_exempt node of TS 24.275, if the UE is in the VPLMN.
If the UE is configured with both the MMTEL_voice_exempt node of TS 24.275 and the EF3GPPPSDATAOFF described in TS 31.102, then the EF3GPPPSDATAOFF shall take precedence;
If the UE is configured with both the MMTEL_voice_roaming_exempt node of TS 24.275 and the EF3GPPPSDATAOFF described in TS 31.102, then the EF3GPPPSDATAOFF shall take precedence; and
the UE may support being configured with the indication whether the MMTEL video is a 3GPP PS data off exempt service using one or more of the following methods:
1. the EF3GPPPSDATAOFF described in TS 31.102;
2. the MMTEL_video_exempt node of TS 24.275, if the UE is in the HPLMN or the EHPLMN; and
3. the MMTEL_video_roaming_exempt node of TS 24.275, if the UE is in the VPLMN.
If the UE is configured with both the MMTEL_video_exempt node of TS 24.275 and the EF3GPPPSDATAOFF described in TS 31.102, then the EF3GPPPSDATAOFF shall take precedence;
If the UE is configured with both the MMTEL_video_roaming_exempt node of TS 24.275 and the EF3GPPPSDATAOFF described in TS 31.102, then the EF3GPPPSDATAOFF shall take precedence.

When the UE is only configured with the indication valid for the UE camping in the HPLMN or the EHPLMN, the UE shall use this indication also when the UE is in the VPLMN.

J.3.1.1.2 Enforcement p. 22

If the 3GPP PS data off status is "active":

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 EPS IP-CAN bearer, 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;
NOTE 1:
When the 3GPP PS data off status is "active", an MMTEL session which is not MMTEL voice and which is not MMTEL video (e.g. MMTEL session with only fax) is released.
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 an EPS IP-CAN bearer, 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;
NOTE 2:
When the 3GPP PS data off status is "active", an MMTEL session which is not MMTEL voice and which is not MMTEL video (e.g. MMTEL session with only fax) cannot be initiated.
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 EPS IP-CAN bearer, 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 an EPS IP-CAN bearer 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;
NOTE 3:
If the UE doesn't send an intitial SIP INVITE due to conditions as described in bullet c.2, the UE can attempt a request for a service equivalent to MMTel voice via the CS domain – if supported and available – and, otherwise, the UE can attempt the service according to TS 24.229 and as described in clause 5.2 via non-3GPP access.
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 an EPS IP-CAN bearer, 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 an EPS IP-CAN bearer and with:
  1. an SDP offer; or
  2. an SDP answer;
  with video; and
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 EPS IP-CAN bearer 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 EPS IP-CAN bearer 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 EPS IP-CAN bearer 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.
NOTE 4:
Which of the bullets 1), 2), and 3) the UE performs is influenced by other 3GPP PS data off exempt services.

J.3.2 Procedures at the multimedia telephony application server p. 24

J.3.2.1 3GPP PS data off p. 24

A multimedia telephony application server supporting the 3GPP PS data off can be configured with:

up to two indications whether the MMTEL voice is a 3GPP PS data off exempt service, one indication is valid for the UE camping in the HPLMN or the EHPLMN, and the other indication is valid for any VPLMN the UE is roaming in; and
up to two indications whether the MMTEL video is a 3GPP PS data off exempt service, one indication is valid for the UE camping in the HPLMN or the EHPLMN, and the other indication is valid for any VPLMN the UE is roaming in.

When the multimedia telephony application server is only configured with the indication valid for the UE camping in the HPLMN or the EHPLMN, the multimedia telephony application server shall use this indication also when the UE is in the VPLMN.

If the multimedia telephony application server supports the 3GPP PS data off, the multimedia telephony application server shall support obtaining registration state information from a received third-party SIP REGISTER request including information contained in the body of the third-party SIP REGISTER request as specified in TS 24.229, of the served UE.

If a received registration state information of the served UE indicates a Contact header field with the g.3gpp.ps-data-off media feature tag with the "active" value:

the multimedia telephony application server shall not send according to TS 24.229 a SIP message related to a multimedia telephony communication session as described in clause 5.2 with:
1. an SDP offer; or
2. an SDP answer;
containing 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;
towards a contact address (or via a registration flow) of the served UE such that the contact address (or the registration flow) was registered or re-registered by a SIP REGISTER request with a P-Access-Network-Info header field with "3GPP-GERAN", "3GPP-UTRAN", "3GPP-E-UTRAN" or "3GPP-NR" access class, and with the "network-provided" header field parameter;
if the multimedia telephony application server is not configured with indication that MMTEL voice is a 3GPP PS data off exempt service for the served UE, the multimedia telephony application server shall not send according to TS 24.229 a SIP message related to the IMS multimedia telephony communication service with:
1. an SDP offer; or
2. an SDP answer;
containing media streams:
1. with only audio;
2. with only real-time text; or
3. with only audio and real-time text;
towards a contact address (or via a registration flow) of the served UE such that the contact address (or the registration flow) was registered or re-registered by a SIP REGISTER request with a P-Access-Network-Info header field with "3GPP-GERAN", "3GPP-UTRAN", "3GPP-E-UTRAN" or "3GPP-NR" access class, and with the "network-provided" header field parameter; and
if the multimedia telephony application server is not configured with indication that MMTEL video is a 3GPP PS data off exempt service for the served UE, the multimedia telephony application server shall not send according to TS 24.229 a SIP message related to a multimedia telephony communication session as described in clause 5.2, with:
1. an SDP offer; or
2. an SDP answer;
containing media streams with video towards a contact address (or via a registration flow) of the served UE such that the contact address (or the registration flow) was registered or re-registered by a SIP REGISTER request with a P-Access-Network-Info header field with "3GPP-GERAN", "3GPP-UTRAN", "3GPP-E-UTRAN" or "3GPP-NR" access class, and with the "network-provided" header field parameter.