Content for TS 23.172 Word version: 18.0.0

1… 4… 4.2.2… 4.2.3 4.2.4 4.2.5… 4.2.5.2 4.3… 4.3.2… 4.3.3… 4.3.3.1.3 4.3.3.1.4 4.3.3.1a… 4.3.4 4.3.5… 4.3.5.2 4.3.6…

4.2.5 Network-initiated Service change in the active state 4.2.5.1 Network-initiated Service change in the active state starting with multimedia in Iu mode
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4.2.5 Network-initiated Service change in the active state |R6| p. 14

When the visited MSC of either party can no longer support an ongoing multimedia call, for example due to degraded coverage conditions (including UTRAN to GERAN only transitions), the visited MSC of this party shall initiate a service-change from multimedia to speech, following the procedures described below.

If the visited MSC is again able to support the multimedia at a later point in time while the speech call is still ongoing, the same visited MSC may initiate a service change from speech to multimedia as stated in TS 22.101. The details for the service change from speech to multimedia are described in clause 4.2.5.2.

For a downgrade from multimedia to speech the visited MSC shall initiate an In-Call Modification procedure towards the terminal it serves using the MODIFY message. The visited MSC shall also invoke the service change procedure (see clause 4.3.5) towards the remote side. The terminals on both sides will react as described in clause 4.2.4.

The Visited MSC shall only initiate a Network Initiated Service Upgrade from speech to multimedia if the terminal has indicated support for Network Initiated Service Upgrade Capability during the call establishment phase, as detailed in TS 24.008. When sending the Modify request to the local terminal the MSC shall include the Network-initiated Service Upgrade indicator. A visited MSC receiving an incoming Network Initiated Service Upgrade procedure from the core network shall also include the Network-initiated Service Upgrade indicator within the MODIFY request to the local terminal.

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.14a: Network-Initiated Service change from multimedia to speech requested, accepted

Figure 4.14a: Network-Initiated Service change from multimedia to speech requested, accepted
(⇒ copy of original 3GPP image)

(no figure)

Figure 4.14b: void

(no figure)

Figure 4.14c: void

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.14c1: Network-Initiated Service change from speech to multimedia requested, accepted

Figure 4.14c1: Network-Initiated Service change from speech to multimedia requested, accepted
(⇒ copy of original 3GPP image)

If the served terminal rejects the service change from speech to multimedia, the initiating MSC shall maintain the original service. If the remote side rejects the service change from speech to multimedia, the initiating MSC shall initiate a service change procedure towards the served terminal to revert to the original service.

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.14c2: Network-Initiated Service change from speech to multimedia requested, rejected by user A

Figure 4.14c2: Network-Initiated Service change from speech to multimedia requested, rejected by user A
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.14c3: Network-Initiated Service change from speech to multimedia requested, rejected by user B

Figure 4.14c3: Network-Initiated Service change from speech to multimedia requested, rejected by user B
(⇒ copy of original 3GPP image)

4.2.5.1 Network-initiated Service change in the active state starting with multimedia in Iu mode p. 16

For a network initiated service change from multimedia in Iu mode to speech, the visited MSC shall use the following procedure.

In order to request a notification from the RNC when it detects a lack of sufficient resources or radio signal degradation, the visited MSC shall include an Alternative RAB Parameters IE in the RANAP RAB Assignment Request or RANAP Relocation Request message indicating the RAB configuration for speech in addition to the RAB configuration for multimedia, when it establishes or modifies the radio access bearer for multimedia at the Iu interface.

When the radio access network detects a lack of sufficient resources to sustain the multimedia RAB configuration, it shall inform the visited MSC by sending a RANAP Modify Request message (see TS 25.413) to the visited MSC. The visited MSC shall then:

initiate an In-Call Modification procedure to speech towards the terminal it serves using the MODIFY message; and
invoke the service change procedure (see clause 4.3.5) towards the remote side,
trigger the RAB modification by sending a RANAP RAB Assignment with the RAB requested to be Modified to the RNC.

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.14d: Network-Initiated Service change from UTRAN multimedia to speech requested, accepted

Figure 4.14d: Network-Initiated Service change from UTRAN multimedia to speech requested, accepted
(⇒ copy of original 3GPP image)