Content for TS 23.292 Word version: 18.0.0

1… 4… 5… 7… 7.2… 7.3… 7.3.2.2… 7.3.2.2.4… 7.4… 7.4.2.2… 7.4.2.2.3… 7.4.2.2.7… 7.5… 7.6… 7.6.1.2.2.6… 7.6.1.2.3… 7.6.1.2.3.5… 7.6.1.2.3.6… 7.6.2… 7.6.2.7 7.6.2.8… 7.6.2.11… 7.6.3… 7.7… 7.7.2… 7.9… 7.9.2… 7.9.2.4 7.9.2.5 8… A… G… H… H.5… H.5.3…

7.4.2.2.3 Terminations with CS media using the I1 reference point 7.4.2.2.4 Terminations with CS media using CS control with I1 augmentation 7.4.2.2.5 Terminations with CS media when not using Gm or I1
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7.4.2.2.3 Terminations with CS media using the I1 reference point |R9| p. 51

Figure 7.4.2.2.3-1 provides an example flow for a call destined to an ICS UE attached to an MSC server enhanced for ICS, where the incoming session is delivered over the I1 reference point and the media is established via the CS network.

Copy of original 3GPP image for 3GPP TS 23.292, Fig. 7.4.2.2.3-1: ICS UE Terminations with CS media information flows using I1 reference point when using an MSC Server enhanced for ICS

Figure 7.4.2.2.3-1: ICS UE Terminations with CS media information flows using I1 reference point when using an MSC Server enhanced for ICS
(⇒ copy of original 3GPP image)

Step 1.

An incoming SIP INVITE is received at the S-CSCF of the B party from UE A.

Step 2.

The S-CSCF executes terminating initial filter criteria and forwards the INVITE to the SCC AS.

Step 3.

The SCC AS sends a Session Progress response to the S-CSCF.

Step 4.

The S-CSCF forwards the Session Progress response to UE A.

Steps 5a - 6a are for the case of T-ADS performed by the SCC AS.

Step 5a.

The SCC AS performs Terminating Access Domain Selection and if informed of the UE capability for I1 during IMS registration, chooses the CS domain for the setup of the media.

Step 6a.

The SCC AS terminates the session from the A-party and establishes a new session over I1 by sending an Incoming Call Request to the B-party via the HSS and MSC Server. The Incoming Call Request contains an indication to inform the UE to initiate the CS bearer establishment procedure. The Incoming Call Request also contains a dynamic SCC AS PSI (DN) to enable the SCC AS to later on correlate the outgoing service control signalling with the incoming CS bearer control signalling.

Steps 5b - 10 are for the case of UE assisted T-ADS.

Step 5b.

Alternatively, in the case of UE assisted T-ADS the SCC AS performs initial T-ADS selecting IMS for the service control signalling when UE-B is registered in the IMS.

Step 6b.

The SCC AS terminates the session from the A-party and establishes a new session by sending an INVITE to the B-party via the I/S-CSCF. The INVITE contains options that enable UE-B to choose a CS bearer for bidirectional speech media transport if it determines that this is not supported by serving PS Access Network. The INVITE also contains a dynamic SCC AS PSI (DN) to enable the SCC AS to later on correlate the outgoing service control signalling with the incoming CS bearer control signalling. When the T-ADS function selects the Gm reference point for service control, the SCC AS prevents the S-CSCF from selecting the contact address of the MSC server, and the S-CSCF selects the IP-CAN.

Step 7b.

The I/S-CSCF sends the INVITE to B-party.

Step 8-10.

In the case where the access network does not support simultaneous PS and CS, UE-B responds with a Session Progress message and in the event the "IMS voice over PS session supported indication" indicates voice is not supported as defined in TS 23.401. UE-B shall indicate in the Session Progress message that a CS bearer is required for the session and that further signalling for the session will be via I1. The S-CSCF forwards the Session Progress message to the SCC AS.

Step 11.

The ICS UE sends a CS Setup message to the MSC Server using the SCC AS PSI DN to establish the CS Bearer Control Signalling Path. This will establish the circuit bearer between the UE and IMS.

Step 12.

The MSC Server responds with a call proceeding message and begins to set up the CS Bearer Control Signalling Path.

Step 13.

The MSC Server sends an INVITE towards the I/S-CSCF containing the SCC AS PSI and an SDP Offer with the media description from the MGW. The MSC Server adds the User Location Information (e.g. CGI or SAI) and/or UE Time Zone Information to the INVITE.

Step 14.

The I/S-CSCF forwards the INVITE to the SCC AS.

Step 15.

The SCC AS continues the session setup towards the A-party for the original INVITE in Step 1. The response contains an SDP answer with the media description from the SDP offer received in Step 13.

Step 16.

The SCC AS completes the set-up of the CS Bearer Signalling Path towards ICS UE B which involves sending a 200 OK in response to the INVITE in Step 14. The ICS UE B, the MSC Server and the SCC AS complete the setup of the CS Bearer Control Signalling Path and the Service Control Signalling Path with UE A.

Step 17.

UE-B sends a Ringing indication to the SCC AS via I1.

Step 18-19.

The SCC AS sends a Ringing message to the remote end.

Step 20.

UE-B sends a Connecting message to the SCC AS via I1.

Step 21-22.

The SCC AS sends a 200 OK message to the remote end in response to the INVITE received at step 2. For video call, to complete the session and bearer setup, the specific handling as described in clause 7.4.2.2.1 applies.

Figure 7.4.2.2.3-2 provides an example flow for a call destined to an ICS UE attached to an MSC server where the incoming session is delivered over the I1 reference point and the media is established via the CS network.

Copy of original 3GPP image for 3GPP TS 23.292, Fig. 7.4.2.2.3-2: ICS UE Terminations with CS media information flows using I1 reference point when using an MSC Server

Figure 7.4.2.2.3-2: ICS UE Terminations with CS media information flows using I1 reference point when using an MSC Server
(⇒ copy of original 3GPP image)

Steps 1-12 in Figure 7.4.2.2.3-2 are identical to steps 1-12 in Figure 7.4.2.2.3-1.

At Steps 13 and 14, the MSC server sends the IAM to an MGCF using the SCC AS PSI DN which is subsequently inter-worked to an INVITE containing the SCC AS PSI and an SDP Offer from the MGW.

Steps 15-23 in Figure 7.4.2.2.3-2 are identical to steps 14-22 in Figure 7.4.2.2.3-1.

7.4.2.2.4 Terminations with CS media using CS control with I1 augmentation |R9| p. 56

Standard CS terminating procedures are used to deliver the incoming session to the ICS UE as described in Figure 7.4.2.2.3-1 when the ICS UE is attached to an MSC server enhanced for ICS, and in Figure 7.4.2.2.3-2 when the ICS UE is attached to an MSC server. Additional IMS parameters can be optionally communicated to the ICS UE using I1 after the incoming session has been delivered.

7.4.2.2.5 Terminations with CS media when not using Gm or I1 p. 56

Figure 7.4.2.1.2-1 provides an example flow for a call destined to an ICS UE attached to an MSC server enhanced for ICS, where the incoming session is delivered using standard CS terminating procedures.

If an ICS UE is attached to an MSC server where the incoming session is delivered to it using standard CS terminating procedures, an example call flow is shown in Figure 7.4.2.1.3-1.