Section: 5.3.6.4 Multimedia CAT during the alerting phase of a mobile originated call
Content: 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].