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…

4.3.5 Service change during the active state 4.3.5.1 Mid-Call Codec Modification Procedure For Service Change
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4.3.5 Service change during the active state p. 40

Whenever an In-Call Modification procedure is invoked by a terminal, unless it is not allowed as determined at call setup, the following shall take place:

if the current mode is the speech mode and the MODIFY message contains a multimedia BC-IE, the normal Out of-Band Transcoder Control procedures shall be invoked in order to change the Selected Codec to the 3G 324.M/3G-324.M2 codec;
if the current mode is the multimedia mode and the MODIFY message contains a speech BC-IE, the normal Out of-Band Transcoder Control procedures shall be invoked in order to change the Selected Codec to the preferred speech codec.

When a visited MSC invokes Network-initiated Service change in the active state (see clause 4.2.5), this visited MSC shall also invoke the normal Out of-Band Transcoder Control procedures in order to change the Selected Codec to speech or to the 3G 324.M/3G-324.M2 codec, respectively.

For a User-initiated service change from speech to multimedia, the visited MSC shall use the 3G-324.M codec as Selected Codec.

If the visited MSC received the 3G-324.M2 codec in the available codec list, the visited MSC shall use the 3G-324.M2 codec as Selected Codec for a Network-initiated Service change procedure from speech to multimedia.

If the visited MSC did not receive the 3G-324.M2 codec in the available codec list, depending on operator policy, the visited MSC may either use the 3G-324.M codec as Selected Codec for a Network-initiated Service change procedure from speech to multimedia, or the visited MSC may not perform a Network-initiated Service change procedure from speech to multimedia.

If the 3G-324.M2 codec is used as Selected Codec in BICC signalling, the 3G-324.M codec shall be signalled instead to the MGW.

The Codec Modification procedure shall be supported for service change. The use of mid-call codec negotiation procedure is optional for service change.

When a MSC detects through an Out-of-Band Transcoder Control procedure that the selected codec has changed from a speech codec to the 3G-324.M codec, or vice-versa, it shall initiate an In-Call Modification procedure towards the UE with a MODIFY message containing the multimedia BC-IE (or the speech BC-IE), unless the new mode has been denied at call setup (see clause 4.2.4).

4.3.5.1 Mid-Call Codec Modification Procedure For Service Change p. 41

The Codec Modification procedures as defined in TS 23.153 shall be applied with the following specific additional rules for the Service Change procedure.

In order to prevent the MGW generating an error or seizing resources during the interim period, when its terminations are being altered and it may have a speech codec on one side of the context and the 3G-324M codec on the other side the Server shall modify the Stream-mode of the affected terminations to inactive during the Service change and shall restore the stream mode to active - (send/receive - bothway) on completion of the service change procedure. In order to restore the stream mode to active, the MSC servers shall use the "Modify Bearer Characteristics" procedure for Iu terminations and for Nb terminations towards the succeeding node with respect to the "Modify Codec" message. The MSC servers shall use the "Confirm Bearer Characteristics" procedure for Nb terminations towards the preceding node with respect to the "Modify Codec" message.

If the affected termination's stream mode is inactive a MGW shall not reject a "Modify Bearer Characteristics" or a "Reserve Bearer Characteristics" procedure because the multimedia codec and a speech codec are interconnected simultaneously in the same context.

For a service change where the CN shall initiate the IuUP on the Nb interface, the MSC server terminating the service change shall trigger the IuUP initialisation towards the core network by setting the IuUP initialisation direction to "out" in the "Confirm Bearer Characteristics" procedure for the corresponding termination towards the core network.

Example call flows are shown in Figure 4.3.5.1-1 to Figure 4.3.5.1-10.

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-1: Service change speech to MuMe

Figure 4.3.5.1-1: Service change speech to MuMe
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-2: Service change speech to MuMe (continued)

Figure 4.3.5.1-2: Service change speech to MuMe (continued)
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-3: Service change MuMe to AMR

Figure 4.3.5.1-3: Service change MuMe to AMR
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-4: Service change MuMe to AMR (continued)

Figure 4.3.5.1-4: Service change MuMe to AMR (continued)
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-5: Service change MuMe to PCM(G.711)

Figure 4.3.5.1-5: Service change MuMe to PCM(G.711)
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-6: Service change MuMe to PCM(G.711) (continued)

Figure 4.3.5.1-6: Service change MuMe to PCM(G.711) (continued)
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-7: Network-initiated service change from MuMe to speech

Figure 4.3.5.1-7: Network-initiated service change from MuMe to speech
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-8: Network-initiated service change from MuMe to speech (continue)

Figure 4.3.5.1-8: Network-initiated service change from MuMe to speech (continue)
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-9: Network-initiated service change speech to MuMe

Figure 4.3.5.1-9: Network-initiated service change speech to MuMe
(⇒ copy of original 3GPP image)

Copy of original 3GPP image for 3GPP TS 23.172, Fig. 4.3.5.1-10: Network-initiated service change speech to MuMe (continued)

Figure 4.3.5.1-10: Network-initiated service change speech to MuMe (continued)
(⇒ copy of original 3GPP image)