5 Network entity functions

23.1353GPPMulticall supplementary serviceRelease 17Stage 2TS

The following SDL diagrams describe the procedures within individual network entities for handling Multicall.

5.1 General

The MSC shall check whether the maximum number of bearers has been reached for both MO and MT call. In counting of the current number of bearers for the target subscriber, the following situations are counted as an active bearer.

– Call in set-up.

– Established call.

– Call on hold.

– Call on hold and established call on the same bearer.

– Call on hold and MO call in Setup on the same bearer.

5.2 MO call

5.2.1 Functional requirements of serving MSC

Figure 8: Procedure Check_OG_Multicall_MSC.

This procedure is called when the MSC receives a Setup message from the MS. After handover procedure completion to another MSC, N_br_SN as defined for the target MSC shall overwrite the previous N_br_SN.

Figure 8: Procedure Check_OG_Multicall_MSC

5.2.2 Functional requirements of VLR

Figure 9: Procedure Check_OG_Multicall_VLR.

This procedure is called when the VLR receives a Send Info For Outgoing Call message from the MSC.

Figure 9: Procedure Check_OG_Multicall_VLR

5.3 MT call

5.3.1 Functional requirements of serving MSC

Figure 10: Procedure Check_MT_Multicall_MSC.

This procedure is called when the MSC receives a Page MS message or a Search For MS message from the VLR. The maximum number of bearers (N_br) indicates the minimum value of N_br_User, N_br_SN and N_br_UE. After handover to another MSC is completed, N_br_SN, as defined for the target MSC, shall overwrite the previous N_br_SN.

"Call in Setup" means that the MS is engaged in at least one call that has not reached the established phase (called party answer).

The test "Call waiting" takes the "Yes" exit if a waiting call has been offered to the subscriber but the outcome of offering the call has not been determined.

Figure 11: Procedure Establish_Terminating_TCH_Multicall.

This procedure is called when the MSC receives a Call Confirmed or a Connect message from the MS. If the MS indicates "No bearer" as the value of the Stream Identifier in the Call Confirmed message the test "Bearer allocation pending" takes the "Yes" exit.

Figure 12: Procedure MC_TCH_Check

This procedure is called when the MSC needs to establish a terminating TCH.

Figure 10: Procedure Check_MT_Multicall_MSC

Figure 11: Procedure Establish_Terminating_TCH_Multicall

Figure 12: Procedure MC_TCH_Check

5.3.2 Functional requirements of VLR

Figure 13: Procedure Get_CW_Subscription_Info_Multicall_VLR.

This procedure is called when the VLR receives a Page MS negative response message or a Search For MS negative response message with the negative response IE set to "Busy (More Calls Possible)".

Figure 13: Procedure Get_CW_Subscription_Info_Multicall_VLR