8.3.1 Retrieval of routeing information in the GMSC

03.783GPPCcustomized Applications for Mobile network Enhanced Logic (CAMEL) Phase 2Release 1998Stage 2TS

The functional behaviour of the GMSC is specified in 3GPP TS 03.18 [3]. The procedures specific to CAMEL are specified in this subclause:

– Procedure CAMEL_Set_ORA_Parameters

– Procedure CAMEL_MT_GMSC_INIT

– Procedure CAMEL_MT_GMSC_ANSWER

– Procedure CAMEL_MT_GMSC_DISC1

– Procedure CAMEL_MT_GMSC_DISC2

– Procedure CAMEL_MT_GMSC_DISC4,

– Procedure CAMEL_MT_GMSC_DISC5,

– Procedure CAMEL_MT_GMSC_DISC6

– Procedure CAMEL_MT_CTR,

– Procedure CAMEL_MT_ETC

– Procedure CAMEL_Start_TNRy,

– Procedure CAMEL_Stop_TNRy.

– Procedure CAMEL_MT_GMSC_Notify_CF.

The procedure Send_ACM_If_Required is specified in 3GPP TS 03.18 [3].

The following paragraphs gives details on the behaviour of the GMSC in the procedure CAMEL_MT_GMSC_INIT.

8.3.1.1 Action of the GMSC on receipt of Int_Release_Call

An ISUP_Release is sent to the originating exchange and resources are released.

8.3.1.2 Action of the GMSC on receipt of Int_Error

The GMSC checks in T-CSI the default Call Handling parameter.

If the default call handling is release call, an ISUP_Release is sent to the originating exchange. The MSC then releases all call resources and the procedure CAMEL_MT_GMSC_INIT returns result=fail.

If the default call handling is continue call, the MSC continue call handling without CAMEL support.

8.3.1.3 Action of the GMSC on receipt of Int_Continue

If a FTN has been stored the information received from HLR is used to overwrite corresponding call parameters. Note that the MSISDN is replaced by the FTN as the Called party number. The redirection counter is incremented.

If no FTN has been stored, a Send Routeing Info message including a T-CSI suppression parameter is sent to the HLR. The Send Routing Info includes an indication which phase of CAMEL is supported by the GMSC/gsmSSF.

8.3.1.4 Action of the GMSC on receipt of Int_Connect

If the Destination Number received from the gsmSCF (via the gsmSSF) is the same as the ISUP Called party number, i.e. the MSISDN, the following parameters, if received, are used to overwrite the corresponding ISUP parameters (for mapping see 3GPP TS 09.78 [5]): Calling Partys Category and Generic Number. If received, the Announcement Suppression Indicator is stored. The further processing is described in subclause 8.3.1.3 with the addition that the Announcement Suppression indicator, if stored, is sent to the HLR in the Send_Routeing_Info message.

If:

– the Destination Number received from the gsmSCF (via the gsmSSF) is not the same as the stored ISUP Called party number, i.e. the MSISDN; and

– a CUG active indication was received from the HLR ; and

– CUG information was received in the ISUP_IAM for the incoming call,

then an exception event is reported to the process gsmSSF, an ISUP_Release is sent to the originating exchange and all resources are released.

Otherwise the following parameters, if received, are used to overwrite the corresponding ISUP parameters (for mapping see 3GPP TS 09.78 [5]): Destination Number, Calling Partys Category, Generic Number, Original Called Party ID, Redirecting Party ID and Redirection Information. Call parameters that are not included in the Int_Connect message are unchanged.

As a network operator option loop prevention mechanisms may cause the redirection information to be ignored or modified (e.g., if the Redirection counter has been decreased).

Signalling limitations or regulatory requirements may require the Calling Partys Category, Generic Number, Original Called Party Number and Redirecting Party ID to be ignored or modified.

The network signalling system shall indicate that this is an internal network number.

8.3.1.5 Action of the GMSC on receipt of Send_Routeing_Info Negative Response (at state Wait_For_Routeing_Info_2)

An exception event is reported to the process gsmSSF. If the Announcement Suppression indicator has been received from the gsmSCF (via the gsmSSF) any announcements or tones shall be suppressed.

8.3.1.6 Action of the GMSC on receipt of Send_Routeing_Info ack with MSRN (at state Wait_For_Routeing_Info_2)

An ISUP_IAM with the MSRN as Called party number is constructed.

8.3.1.7 Action of the GMSC on receipt of Send_Routeing_Info ack with FTN (at state Wait_For_Routeing_Info_2)

The information received from HLR is used to overwrite corresponding call parameters (for details see 3GPP TS 03.18 [3]). The redirection counter is incremented.

8.3.1.8 Action of the GMSC on receipt of Send_Routeing_Info ack with O-CSI and FTN (at state Wait_For_Routeing_Info_2)

The information received from the HLR is used to overwrite corresponding call parameters. The redirection counter is incremented. The Called Party Number is set to FTN.

8.3.1.9 Action of the GMSC in procedure CAMEL_MT_ETC

In procedure CAMEL_MT_ETC (sheet 2) the GMSC will remain in the Wait_For_Assiting_Answer state until it receives an ISUP Answer Message (ANM) or timeout occurs. This is to ensure that a call record is always generated for every successful establishment of a temporary connection to a gsmSRF, especially in the case where the connection is between PLMNs.

NOTE: This means that it may not be possible to access an SRF which does not generate an ISUP Answer Message (ANM).

If a Progress message is sent towards the MS the progress indicator shall indicate "In Band Information".

8.3.1.10 Action of the GMSC in procedure CAMEL_MT_GMSC_Notify_CF

The Forwarding reason is taken from the Send Routeing Info ack (for early call forwarding) or the Resume Call Handling (for Optimal Routeing of Late Call Forwarding).

The Int_DP_T_No_Answer and Int_DP_T_Busy messages include a parameter to indicate that the call has encountered conditional call forwarding. The gsmSSF will transfer this parameter to the CAP_Event_Report_BCSM message which it sends to the gsmSCF.

Note: The GMSC may receive a CF Conditional in the first Send Routeing Information ack. This CF may lead to a notification to the gsmSCF, depending on the presence of T-CSI in this first Send Routeing Information ack and on the dynamic arming of the T-Busy EDP by the gsmSCF.
Some GMSCs may not send the notification to the gsmSCF in above described scenario. In this case, the procedure continues the call processing.
As the rationale of the Notification of Call Forwarding principle is to inform the gsmSCF of notification after the second Send Routeing Information ack, the behaviour of these GMSC is not erroneous.

Figure 23a: Procedure CAMEL_Set_ORA_Parameters (sheet 1)

Figure 24a: Procedure CAMEL_MT_GMSC_INIT (sheet 1)

Figure 24b: Procedure CAMEL_MT_GMSC_INIT (sheet 2)

Figure 24c: Procedure CAMEL_MT_GMSC_INIT (sheet 3)

Figure 24d: Procedure CAMEL_MT_GMSC_INIT (sheet 4)

Figure 24e: Procedure CAMEL_MT_GMSC_INIT (sheet 5)

Figure 24f: Procedure CAMEL_MT_GMSC_INIT (sheet 6)

Figure 24g: Procedure CAMEL_MT_GMSC_INIT (sheet 7)

Figure 24h: Procedure CAMEL_MT_GMSC_INIT (sheet 8)

Figure 25a: Procedure CAMEL_MT_GMSC_ANSWER (sheet 1)

Figure 26a: Procedure CAMEL_MT_GMSC_DISC1 (sheet 1)

Figure 27a: Procedure CAMEL_MT_GMSC_DISC2 (sheet 1)

Figure 27b: Procedure CAMEL_MT_GMSC_DISC2 (sheet 2)

Figure 28a: Procedure CAMEL_MT_GMSC_DISC4 (sheet 1)

Figure 28b: Procedure CAMEL_MT_GMSC_DISC4 (sheet 2)

Figure 28c: Procedure CAMEL_MT_GMSC_DISC4 (sheet 3)

Figure 29a: Procedure CAMEL_MT_GMSC_DISC5 (sheet 1)

Figure 29b: Procedure CAMEL_MT_GMSC_DISC5 (sheet 2)

Figure 29c: Procedure CAMEL_MT_GMSC_DISC5 (sheet 3)

Figure 30a: Procedure CAMEL_MT_GMSC_DISC6 (sheet 1)

Figure 31a: Procedure CAMEL_MT_ETC (sheet 1)

Figure 31b: Procedure CAMEL_MT_ETC (sheet 2)

Figure 31c: Procedure CAMEL_MT_ETC (sheet 3)

Figure 32a: Procedure CAMEL_MT_CTR (sheet 1)

Figure 32b: Procedure CAMEL_MT_CTR (sheet 2)

Figure 32c: Procedure CAMEL_MT_CTR (sheet 3)

Figure 32d: Procedure CAMEL_MT_CTR (sheet 4)

Figure 33a: Procedure CAMEL_MT_GMSC_Notify_CF (sheet 1)