Section: 5.2.2.3.2 Receipt of CALL CONFIRMED and ALERTING by the network
Content: The call control entity of the network in the "call present" state, shall, upon receipt of a CALL CONFIRMED message: stop timer T303, start timer T310 and enter the "mobile terminating call confirmed" state. In Iu mode, network shall include the SI received in the CALL CONFIRMED message into the RABid and send it back to the mobile station. For RABid see 3GPP TS 25.413[ UTRAN Iu interface Radio Access Network Application Part (RANAP) signalling ]  [19c] and 3GPP TS 44.118[ None ]  [111]. If the network receives the CALL CONFIRMED message with no SI, the network shall set the SI value to 1. For speech calls, if the CALL CONFIRMED message contains a Supported Codec List information element, 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. Codec information that does not apply to the currently serving radio access shall be used by the network if an inter-system change occurs. The call control entity of the mobile station having entered the "mobile terminating call confirmed" state, if the call is accepted at the called user side, the mobile station proceeds as described in subclause 5.2.2.5. Otherwise, if the signal information element was present in the SETUP message user alerting is initiated at the mobile station side; if the signal information element was not present in the SETUP message, user alerting is initiated when an appropriate channel is available. Here, initiation of user alerting means: - the generation of an appropriate tone or indication at the mobile station; and - sending of an ALERTING message by the call control entity of the MS to its peer entity in the network and entering the "call received" state. The call control entity of the network in the "mobile terminated call confirmed" state shall, upon receipt of an ALERTING message: send a corresponding ALERTING indication to the calling user; stop timer T310; start timer T301, and enter the "call received" state. In the "mobile terminating call confirmed" state or the "call received" state, if the user of a mobile station is User Determined User Busy then a DISCONNECT message shall be sent with cause #17 "user busy". In the "mobile terminating call confirmed" state, if the user of a mobile station wishes to reject the call then a DISCONNECT message shall be sent with cause #21 "call rejected".