5.3 Signalling procedures during the "active" state

24.0083GPPCore network protocolsMobile radio interface Layer 3 specificationRelease 18Stage 3TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.3.1 User notification procedure

The mobile terminating user notification procedure allows the network to notify a mobile station of any appropriate call-related event during the "active" state of a call. The procedure consists in the network sending a NOTIFY message to the mobile station. No state change occurs at any of the interface sides following the sending or the receipt of this message (but an appropriate indication may optionally be generated in the mobile station).

The mobile originating notification procedure allows the mobile station to notify the remote user of any appropriate call-related event during the "active" state of a call by sending a NOTIFY message containing a notification indicator to the network; upon receipt of this message, the network sends a NOTIFY message containing the same notify indicator to the other user involved in the call. No state change occurs at any of the interface sides following the sending or the receipt of this message.

5.3.2 Call rearrangements

Call rearrangements on the radio interface are not supported by explicit messages (e.g. SUSPEND and RESUME messages as defined in ETSI ETS 300 102-1 [70]). However if a remote non-PLMN user initiates call rearrangements, the network shall inform the mobile station by means of a NOTIFY message. In a similar way the mobile station can inform the network about rearrangements by sending a NOTIFY message (e.g. change of user equipment connected to the mobile station).

5.3.3 Codec Change Procedure

During a speech call in UMTS, if a mobile station supports more than one UMTS codec, the network can change the UMTS codec via RRC procedures. In order to request the mobile station to change the codec, the network shall send the new selected codec type in the NAS Synchronisation Indicator IE (RRC protocol), see subclause 5.2.1.11.

5.3.4 Support of Dual Services

The behaviour described in this subclause is used to realize the following required services throughout subclause 5.3.4. The mobile station is not obliged to support the network originated in-call modification procedure. In that case, the mobile station shall, when receiving a MODIFY message, treat the message as unknown and react as described in subclause 8.4. If the mobile station is already prepared to support the procedure in both directions, it shall act as described in this subclause.

Alternate Speech/Group 3 fax (Teleservice 61 according to 3GPP TS 22.003 [4]).

5.3.4.1 Service Description

This circuit switched service allows the two users on a point-to-point connection to use the connection between them for different information transfer during the same call, but not at the same time.

If the negotiation during call establishment leads to the recognition of the above mentioned services, the in-call modification procedure is allowed to be executed within the current call by changing from one call mode to the other.

In some cases the in-call modification procedure makes it necessary to change the channel configuration by allocating a new channel and in other cases to change channel configuration parameters while keeping the previously allocated channel. This change is determined by the network, which initiates either the channel assignment procedure, handover procedure or channel mode modify procedure (see clause 3).

The capability and the initial mode desired must be identified by the mobile station by identifying each mode of operation with a separate information element during call establishment. Further the type of change between the modes must be identified by means of the repeat indicator:

mode 1 "alternate" mode 2.

5.3.4.2 Call establishment

For both mobile originating and mobile terminating calls, the normal call establishment procedures apply.

5.3.4.2.1 Mobile Originating Establishment

The service is requested by the originating mobile station by transferring a SETUP message to the network containing the BC repeat indicator IE, the bearer capability 1 information element, and the bearer capability 2 information element. The first mode of operation ("call mode") shall be indicated by the bearer capability 1 information element and the second call mode by the bearer capability 2 information element.

A low layer compatibility may optionally be specified for each call mode in a low layer compatibility I and low layer compatibility II information element. In that case:

– the SETUP message shall contain the LLC repeat indicator IE and both low layer compatibility I and low layer compatibility II information elements. The low layer compatibility I information element then corresponds to the bearer capability 1 information element and the low layer compatibility II information element to the bearer capability 2 information element;

– if no low layer compatibility specification applies for one of the two call modes, the corresponding low layer compatibility IE (low layer compatibility I or low layer compatibility II) shall indicate "not applicable";

– the LLC repeat indicator shall specify the same repeat indication as the BC repeat indicator IE.

Similarly, a high layer compatibility may optionally be specified for each call mode in a high layer compatibility i and high layer compatibility ii information element. In that case:

– the SETUP message shall contain the HLC repeat indicator IE and both high layer compatibility i and high layer compatibility ii information elements. The high layer compatibility i information element then corresponds to the bearer capability 1 information element and the high layer compatibility ii information element to the bearer capability 2 information element;

– if no high layer compatibility specification applies for one of the two call modes, the corresponding high layer compatibility IE (high layer compatibility i or high layer compatibility ii) shall indicate "not applicable";

– the HLC repeat indicator shall specify the same repeat indication as the BC repeat indicator IE.

The receiving entity shall ignore whether the LLC repeat indicator IE or HLC repeat indicator are contained in the message or not; it shall also ignore the repeat indication of an LLC repeat indicator IE or HLC repeat indicator IE. If the low layer compatibility II IE is not contained in the message and the low layer compatibility I IE is contained in the message, the receiving entity shall relate it to a call mode indicated in the message that does not specify speech (if any). If the high layer compatibility ii IE is not contained in the message and the high layer compatibility i IE is contained in the message, the receiving entity shall relate it to a call mode indicated in the message that does not specify speech (if any).

The specific part of the network which is sensitive to the call mode shall examine each mode described in the bearer capabilities included in the SETUP message by performing compatibility checking as defined in Annex B. If as a result of this compatibility checking the network decides to reject the call, then the network shall initiate call clearing as specified in subclause 5.4 with the following causes:

a) #57 "bearer capability not authorized";

b) #58 "bearer capability not presently available";

c) #65 "bearer service not implemented";

d) #70 "only restricted digital information bearer capability is available".

5.3.4.2.2 Mobile Terminating Establishment

The service is indicated to the called mobile station by a SETUP message coded in the same manner as in the mobile originating call establishment. As specified for normal terminating call establishment, the service may be indicated by the called mobile station in the CALL CONFIRMED message.

The destination mobile station shall perform the compatibility checking as defined in Annex B for both required modes if indicated in the SETUP message. If as a result of compatibility checking the mobile station decides to reject the call, the mobile station shall initiate call clearing according to the procedures of subclause 5.4 with one of the following causes:

a) #57 "bearer capability not authorized";

b) #58 "bearer capability not presently available";

c) #65 "bearer service not implemented";

d) #88 "incompatible destination".

The mobile station may accept the call if the first mode indicated is free irrespective of whether the other mode is free or busy.

5.3.4.3 Changing the Call Mode

In order to change the call mode, the following in-call modification procedures shall be used.

Either side of the radio interface may act as the requesting user to invoke the in-call modification.

Upon each successful completion of the in-call modification procedure, the call changes to the next mode negotiated and agreed during the establishment phase of the call.

The in-call modification procedures are completely symmetrical at the radio interface.

5.3.4.3.1 Initiation of in-call modification

The procedure is initiated by the requesting originating side in the "active" state of the call. It shall send a MODIFY message including the new mode to be changed to. The requesting originating side shall also start timer T323 and enter the "mobile originating modify" state (mobile station side) or the "mobile terminating modify" state (network side). The new mode given in the MODIFY message shall be one of those already negotiated and agreed during the establishment phase of the call. If the data call direction is different from the direction of the call setup a reverse call setup direction IE shall be included in the MODIFY message; otherwise this IE shall not be included.

If the in-call modification is originated by the mobile station, the mobile station shall reserve any internal resources necessary to support the next call mode, stop sending Bm-channel information; and stop interpreting received Bm-channel information according to the old call mode.

If the in-call modification is originated by the network, the network may reserve any internal resources necessary to support the next call mode. The network shall stop sending Bm-channel information and stop interpreting received Bm-channel information according to the old call mode at the latest when it changes the channel configuration.

Upon receipt of the MODIFY message, the destination side shall check to ensure that the requested call mode can still be supported and if so, it shall initiate the reservation of any resources necessary to support the next call mode; start T324 (mobile station side only) if the in-call modification procedure is triggered as a result of a service change from speech to UDI/RDI multimedia modes; and enter the "mobile originating modify" (network side) or "mobile terminating modify" state (mobile station side).

5.3.4.3.2 Successful completion of in-call modification

If the destination network/mobile station receives a MODIFY message with a new mode which is already the actual one of the call the network/mobile station shall remain in the "active" state; send a MODIFY COMPLETE message with the actual mode; and shall not initiate anything else.

If the requested mode is speech and if during call establishment the network received a Supported Codec List IE, the network shall use this list to select the codec for UTRAN. If no Supported Codec List information element is received, then for UTRAN the network shall select the default UMTS speech codec according to subclause 5.2.1.11.

Codecs for GERAN shall be selected from the codecs indicated in the Supported Codec List information element or in the Bearer Capability information element. If neither a Supported Codec List information element nor a Bearer Capability information element is received, then for GERAN the network shall select GSM full rate speech version 1.

If the Supported Codec List IE is received, then the network shall indicate the codec selected for Iu mode to the mobile station via RANAP and RRC protocol in the NAS Synchronisation Indicator IE (see subclause 5.2.1.11).

If the in-call modification was originated by the mobile station, the mobile station and the network shall proceed as follows:

If the requested mode is not the actual one and can be supported by the network it shall change the channel configuration, if required, and step on to any internal resources necessary to support the next call mode. If the requested mode is a data or facsimile mode, it shall also perform the appropriate means to take the direction of the data call into account. After successful change of the channel configuration it shall start sending user information according to the next call mode and start interpreting received user channel information according to the next call mode; send a MODIFY COMPLETE message with the new call mode included and enter the "active" state (network side). If the MODIFY message had contained a reverse call setup direction IE, the same IE shall be included in the MODIFY COMPLETE message.

Upon receipt of the MODIFY COMPLETE message the mobile station shall: initiate the alternation to those resources necessary to support the next call mode; stop timer T323; and enter the "active" state (mobile station side).

If the in-call modification was originated by the network, the mobile station and the network shall proceed as follows:

If the requested mode is not the actual one and can be supported by the mobile station it shall reserve any internal resources necessary to support the next call mode.

NOTE: For a change from speech to a different call mode, user interaction may be required, before the mobile decides that the requested mode can be supported.

If the requested mode is a data or facsimile mode, it shall also perform the appropriate means to take the direction of the data call into account. The mobile station shall send a MODIFY COMPLETE message with the new call mode included, stop timer T324 and enter the "active" state (mobile station side). If the MODIFY message had contained a reverse call setup direction IE, the same IE shall be included in the MODIFY COMPLETE message. If the old call mode is speech, the mobile station shall continue sending Bm-channel information and interpreting received Bm-channel information for speech until the network modifies its channel configuration.

After receipt of the MODIFY COMPLETE message the network shall: reserve any internal resources necessary to support the next call mode, stop sending Bm-channel information, and stop interpreting received Bm-channel information according to the old call mode, unless these actions were already performed earlier. Furthermore, the network shall change the channel configuration, if required; after successful change of the channel configuration initiate the alternation to those resources necessary to support the next call mode; stop timer T323; and enter the "active" state (network side).

The mobile station shall start sending user information according to the next call mode and start interpreting received user channel information according to the next call mode as soon as a suitable channel for the new mode is available.

In both cases:

For an alternate speech/facsimile group 3 service (refer to subclause 5.3.4) the old resources may still be kept reserved.

The reaction of the originating side if it had included a reverse call setup direction IE in the MODIFY message, but the destination side did not include the IE in the MODIFY COMPLETE message is implementation dependent.

5.3.4.3.3 Change of the channel configuration

In case the requested bearer capability cannot be supported by the current channel configuration the network shall initiate the assignment procedure and change the channel configuration accordingly.

5.3.4.3.4 Failure of in-call modification

5.3.4.3.4.1 Network rejection of in-call modification

If the network cannot support the change to the requested call mode or if the change of the channel configuration fails the network shall: release the resources which had been reserved for the alternation: send a MODIFY REJECT message with the old bearer capability and with cause # 58 "bearer capability not presently available" to the initiating mobile station; and enter the "active" state. If the change of the channel configuration fails, the network shall return to the internal resources required for the old call mode.

Upon receipt of the MODIFY REJECT message with the old bearer capability the initiating mobile station shall: stop timer T323; release any resources which had been reserved for the alternation; resume sending user channel information according to the present call mode; resume interpreting received user channel information according to the present call mode; and enter the "active" state.

5.3.4.3.4.2 Mobile station rejection of in-call modification

If the mobile station cannot support the change to the requested call mode, the mobile station shall: stop timer T324; release any resources which had been reserved for the alternation; send a MODIFY REJECT message with the old bearer capability and cause # 58 "bearer capability not presently available", and enter the "active" state.

Upon receipt of the MODIFY REJECT message the network shall: stop timer T323, release any resources which had been reserved for the alternation.

5.3.4.3.4.3 Time-out recovery

Upon expiration of T323 in either the mobile station or the network the procedures for call clearing shall be initiated (see subclause 5.4) with cause # 102 "recovery on timer expiry".

Upon expiration of T324 the mobile station shall: release any resources which had been reserved for the alternation; send a MODIFY REJECT message with the old bearer capability and cause #58 "bearer capability not presently available"; and enter the "active" state.

5.3.4.4 Abnormal procedures

If a MODIFY, MODIFY COMPLETE or MODIFY REJECT message is received in the "disconnect indication", "disconnect request" (mobile station side only) or "release request" state then the received message shall be discarded and no action shall be taken.

If a MODIFY COMPLETE message indicating a call mode which does not correspond to the requested one is received or if a MODIFY REJECT message indicating a call mode which does not correspond to the actual one is received then the received message shall be discarded and no action shall be taken.

If a MODIFY message indicating a call mode which does not belong to those negotiated and agreed during the establishment phase of the call, is received, then a MODIFY REJECT message with the actual call mode and with cause # 57 "bearer capability not authorized" shall be sent back.

Figure 5.10a/3GPP TS 24.008 In-call modification sequence initiated by MS

Figure 5.10b/3GPP TS 24.008 In-call modification sequence initiated by network

5.3.5 User initiated service level up- and downgrading (A/Gb mode and GERAN Iu mode only)

The user initiated service level up- and downgrading is applicable for non-transparent multislot data services, only. By means of this procedure the user can request a change of the "maximum number of traffic channels" and/or "wanted air interface user rate" parameters, to be assigned by the network.

5.3.5.1 Initiation of service level up- and downgrading

The procedure is initiated by the mobile station in the "active" state of the call. It shall:

‑ send a MODIFY message including the wanted value of the "maximum number of traffic channels" and/or the "wanted air interface user rate" parameters;

‑ not change any of the other, possibly negotiated, parameters of the bearer capability information element;

‑ start timer T323; and

‑ enter the "mobile originating modify" state.

Any internal resources necessary to support the next service parameters shall be reserved. If a dual service was negotiated at call setup, the mobile station shall initiate the service level up- or down-grading only during the data phase of the dual service.

Upon receipt of the MODIFY message, the network shall check if the indicated maximum number of traffic channels can be supported and enter the "mobile originating modify" state.

5.3.5.2 Successful completion of service level up- and downgrading

The network may upon reception of the MODIFY message initiate a change of the channel configuration assigned to the mobile station.

As a response to the MODIFY message the network sends a MODIFY COMPLETE message including the bearer capability negotiated at call setup and enters the "active" state.

Upon receipt of the MODIFY COMPLETE message the mobile station shall stop timer T323 and enter the "active" state.

5.3.5.3 Rejection of service level up- and downgrading

If a change of bearer service is requested together with a change of the "maximum number of traffic channels" and/or the "wanted air interface user rate", or if the current used service is not a data service where up- and downgrading is applicable, or if the receiver chooses not to grant the request, the network shall:

‑ send a MODIFY REJECT message with bearer capability negotiated at call setup and with cause #58 "bearer capability not presently available";

‑ enter the "active" state.

Upon receipt of the MODIFY REJECT message with the bearer capability negotiated at call setup, the mobile station shall: stop timer T323 and enter the "active" state.

5.3.5.4 Time-out recovery

Upon expiration of T323 in the mobile station the procedures for call clearing shall be initiated with cause #102 "recovery on timer expiry".

5.3.6 Support of multimedia calls

5.3.6.1 Service description

The 3GPP circuit-switched multimedia call is based on the 3G-324M (see 3GPP TS 26.111 [80]), which is a 3GPP-variant of the ITU-T Recommendation H.324 [146]. CS Multimedia telephony is a Bearer Service, which utilizes the Synchronous Transparent Data service (BS30), see 3GPP TS 22.002 [3].

At the multimedia call setup the required call type, 3G-324M, is indicated, for the network to be able to invoke appropriate interworking functionality. In the peer end the H.324 information is used to invoke the terminal application. In addition to H.324 indication the terminal must select Information Transfer Capability (ITC) for the multimedia call. The ‘correct’ ITC depends on the peer end and the transporting networks; an all-ISDN call is a UDI/RDI call, and a call, which involves PSTN, is an analog "3.1 kHz audio" call.

For the case when the setup of a multimedia call is not successful, fallback to speech is specified.

Users may also request a service change between UDI/RDI multimedia and speech modes during a call (see 3GPP TS 23.172 [97]).

5.3.6.2 Call establishment

For both mobile originating and mobile terminating calls, the normal call establishment procedures apply, with the exceptions specified in the following subclauses.

For further description of the function of MSC/IWF in the following clauses, see 3GPP TS 29.007 [38].

5.3.6.2.1 Mobile originated multimedia call establishment

At call setup the required call type, 3G-324M, is indicated by the originating MS in the SETUP message, with the bearer capability IE parameter Other Rate Adaption set to "H.223 and H.245".

For analogue multimedia, the support of a fallback to speech is requested by including two bearer capability IEs, multimedia first and speech as the second BC in the SETUP message. The MS shall indicate fallback to speech by these two BC IEs and the associated Repeat Indicator set to "support of fallback".

For UDI/RDI multimedia, the support of a fallback and service change is requested by including two bearer capability IEs, with the first BC as the preferred service in the SETUP message. The MS shall indicate service change and fallback by these two BC IEs and the associated Repeat Indicator set to "support of service change and fallback".

If the bearer capability IE is received from the MS either in A/Gb or GERAN Iu mode and indicates no A/Gb mode support for the requested bearer service, the network shall consider it as a request to perform an inter-system handover to UTRAN Iu mode, as described in 3GPP TS 23.009 [114] subclause 14.2.

The bearer compatibility checking in the network is according to subclause 5.3.4.2.1.

If the MS requested for an analogue multimedia call with fallback to speech, or for a UDI/RDI multimedia call with fallback and service change, and the network accepts the call, the network has the following options for the inclusion of bearer capability IEs in the CALL PROCEEDING message:

– if the network accepts the requested analogue multimedia call and supports fallback to speech, both multimedia and speech bearer capability IEs shall be included;

– if the network accepts the requested UDI/RDI multimedia call and supports fallback and service change, both multimedia and speech bearer capability IEs shall be included. The order of the bearer capability IEs determines the preferred service, and the network may reverse the order of these IEs (see 3GPP TS 23.172 [97], subclause 4.2.1);

– if the network accepts a multimedia (only) call, a multimedia bearer capability IE shall be included;

– if the network accepts a speech (only) call, a speech bearer capability IE shall be included;

– for a UDI/RDI multimedia call, if the network accepts the requested speech call and supports service change, both multimedia and speech bearer capability IEs shall be included. The order of the bearer capability IEs determines the preferred service, and the network may reverse the order of these IEs (see 3GPP TS 23.172 [97], subclause 4.2.1);

– if the network received a UDI/RDI multimedia bearer capability IE with FNUR equal to 32kbit/s and a speech bearer capability IE in the SETUP message, the network shall not release the call, but shall reply with one bearer capability IE only, as specified in 3GPP TS 23.172 [97].

NOTE: Service change and fallback for UDI/RDI multimedia calls is not supported with Fixed Network User Rate set to 32 kbit/s (see 3GPP TS 23.172 [97]).

If the MS requested for a multimedia call only, and the network accepts the call, the network shall always include a single multimedia bearer capability IE in the CALL PROCEEDING message.

The originating user shall determine (possibly by pre-configuration of the terminal) whether a digital connection is required or if the call will be an analog modem call. If the call is expected to be digital the multimedia bearer capability IE parameter ITC is set to UDI/RDI. In an analog call the multimedia bearer capability IE parameter ITC is set to "3,1 kHz audio ex PLMN". Additionally required modem type is indicated (Other Modem Type = V.34).

5.3.6.2.1.1 Fallback

If the network, during the setup of an H.324-call, detects that the transit network or the called end does not support an H.324 call (e.g. because of a failure in the modem handshaking in case of an analogue multimedia call), then the network initiates the in-call modification procedure (see subclause 5.3.4.3) towards the MS to modify the call mode to speech, if the MS had included a speech bearer capability IE in the SETUP message.

In case of a UDI/RDI multimedia call with service change and fallback, if the network detects that the called end does not support speech, then it initiates an in-call modification procedure towards the MS to modify the call mode to multimedia, if the first bearer capability IE was for a speech call.

5.3.6.2.2 Mobile terminating multimedia call

At call setup the required call type, 3G-324M, is indicated by the network in the SETUP message, with the bearer capability IE parameter. Other Rate Adaption set to ‘H.223 and H.245’. ITC is either ‘3,1 kHz audio ex PLMN’ or ‘UDI/RDI’.

For analogue multimedia, if the network supports fallback to speech and the subscriber has subscription to speech, two bearer capability IEs, multimedia first and speech as the second BC are included in the SETUP message. The network shall indicate fallback to speech by these two BC IEs and the associated Repeat Indicator set to "support of fallback".

For UDI/RDI multimedia, if the network supports fallback and service change, and the subscriber has subscription to speech, two bearer capability IEs, with the first BC as the preferred service are included in the SETUP message. The network shall indicate service change and fallback by these two BC IEs and the associated Repeat Indicator set to "service change and fallback".

The bearer capability IE(s) may (in the case of the single numbering scheme) be missing from the SETUP message.

The bearer compatibility checking in the MS is according to subclause 5.3.4.2.2.

The MS shall indicate the supported call type(s) in the CALL CONFIRMED message, which is the acknowledgement to SETUP. If the network offered an analogue multimedia call with fallback to speech, or a UDI/RDI multimedia call with fallback and service change, the MS has the following options for the inclusion of bearer capability IEs in the CALL CONFIRMED message:

– if the MS/user accepts the offered analogue multimedia call and supports fallback to speech, both multimedia and speech bearer capability IEs shall be included;

– if the MS/user accepts the offered UDI/RDI multimedia call, and supports fallback and service change, both multimedia and speech bearer capability IEs shall be included. The order of the BC IEs determines the preferred service, and the MS/user may reverse the order of these IEs;

– if the MS/user accepts the offered multimedia call, but does not support fallback or service change, only a multimedia bearer capability IE shall be included;

– if the MS/user wishes a speech (only) call a speech bearer capability IE is included;

– for a UDI/RDI multimedia call, if the MS/user accepts the offered speech call and supports service change, both speech and multimedia bearer capability IEs shall be included. The order of the BC IEs determines the preferred service, and the MS/user may reverse the order of these IEs.

If the network offered a multimedia call only, and the MS/user accepts the call, the MS shall always include a single multimedia bearer capability IE in the CALL CONFIRMED message.

If the SETUP contained no bearer capability IE the network shall perform compatibility checking of the CALL CONFIRMED message in the same way as the compatibility checking of the SETUP message in the mobile originating call case, described in subclause 5.3.6.2.1.

5.3.6.2.2.1 Fallback to speech

If modem handshaking fails (in a modem call), the call mode will be modified to speech if a speech bearer capability IE was included. The modem signalling is inband, so the call must have reached the active state, when these conclusions about the presence of modems can be done. The call modifications are realized through the in-call modification procedure, by which the network requests the MS to modify the call mode (see subclause 5.3.4.3).

NOTE: Fallback from digital (UDI) H.324-call to speech after call setup is not a valid case at the terminating side.

5.3.6.3 In-call modification in the "active" state

The in-call modification procedure as described in subclause 5.3.4.3 shall be used to:

– trigger a service change between speech and UDI/RDI multimedia modes, when service change has been agreed at call setup;

– trigger a network-initiated service upgrade from speech to UDI/RDI multimedia modes (see 3GPP TS 23.172 [97]). The network shall initiate this procedure only if the mobile station indicated support of the enhanced network-initiated in-call modification procedure in the Call Control Capabilities IE at call establishment. In this case, the MODIFY message shall include the Network-initiated Service Upgrade indicator IE; or

– modify the multimedia bearer capability for an analogue multimedia call (restricted to the network initiated in-call modification only). In this case, the network shall send a MODIFY message including the new Bearer Capability to be changed to. The following bearer capability parameters can be modified with the procedure (see 3GPP TS 29.007 [38]):

– Fixed Network User Rate (analogue multimedia calls only).

5.3.6.3.1 Void

5.3.6.3.2 Void

5.3.6.3.3 Void

5.3.6.3.3.1 Void

5.3.6.3.3.2 Void

5.3.6.4 Multimedia CAT during the alerting phase of a mobile originated call

A mobile station supporting multimedia CAT during the alerting phase of a mobile originated multimedia call establishment shall indicate support of this capability to the network in the Call Control Capabilities information element in the SETUP message.

The network may generate a multimedia CAT to such a mobile station before it has reached the "active" state of a call. To do so, the network shall through connect the traffic channel towards the source of the multimedia CAT and send a progress indicator IE indicating user attachment with progress description #9 "In-band multimedia CAT available" in either an ALERTING message or a PROGRESS message that is sent to the mobile station during call establishment.

On reception of an ALERTING or a PROGRESS message the mobile station shall proceed as specified elsewhere in clause 5; if the progress indicator IE indicated user attachment with progress description #9 "In-band multimedia CAT available", the mobile station shall:

– attach the user connection for multimedia as soon as an appropriate channel in multimedia mode is available; and

– set up an H.324 call.

It is up to the network to ensure that no undesired end-to-end through connection with the called party takes place during the establishment of a mobile terminated call.

The mobile station shall not abort the call if an error or H.324 call clearing occurs during the setup or the lifetime of the H.324 call during the alerting phase; the call control entity of the calling mobile station shall remain in its current state.

Upon reception of a new request from the network to attach the user connection with progress description #9 "In-band multimedia CAT available", the mobile station shall release any on-going H.324 call, and set up a new H.324 call.

NOTE: The network can request the mobile station to restart a new H.324 call during the alerting phase of the call e.g. during call forwarding scenarios to transmit to the calling party the multimedia CAT of the forwarded-to party.

The network may initiate the in-call modification procedure (see subclause 5.3.4.3) towards the MS in the "call delivered" state to modify the call mode to speech, if service change has been agreed at call setup.

Upon receiving an indication that the call has been accepted, the call control entity of the network shall send a CONNECT message to its peer entity at the calling mobile station; start timer T313 and enter the "connect indication" state. This message indicates to the call control entity of the calling mobile station that a connection has been established through the network.

On reception of a CONNECT message, the mobile station shall proceed as specified elsewhere in clause 5; the mobile station shall release any on-going H.324 call and set up a new H.324 call towards the called party.

Mobile stations supporting multimedia CAT during the alerting phase of a mobile originated multimedia call establishment should also support the Media Oriented Negotiation Acceleration procedures specified in ITU-T Recommendation H.324 Amendment 1 [117] and ITU-T Recommendation H.324 Amendment 2 [118].

5.3.6.5 DTMF transmission during a multimedia call

A mobile station supporting multimedia CAT during the alerting phase of a mobile originated multimedia call establishment should support transmission of DTMFs during a H.324 call using the H.245 UserInputIndication message (see ITU-T H.245 [119]) if it has attached the user connection for multimedia and an appropriate channel is available.

NOTE: DTMF can be used to convey to the network the end user request to stop or copy an on-going multimedia CAT.

5.3.6.6 vSRVCC handover to a circuit-switched multimedia call

Upon vSRVCC handover to a traffic channel suitable for a data call, the MS shall use a single bearer capability IE for multimedia with ITC set to "UDI" and FNUR set to 64 kbit/s for the call.

NOTE: After the MS has attached the user connection (see subclause 5.2.4.3), the MS initially uses predefined codecs for voice and video as specified in 3GPP TS 26.111 [80]. Additionally, the MS can perform in-band codec re-negotiation using H.245 signalling according to the procedures defined in 3GPP TS 26.111 [80].