4.5.3 Retrieval of routeing information

23.0783GPPCustomised Applications for Mobile network Enhanced Logic (CAMEL) Phase 4Release 17Stage 2TS

4.5.3.1 Retrieval of routeing information in the GMSC

The functional behaviour of the GMSC is specified in 3GPP TS 23.018 [12]. The procedures specific to CAMEL are specified in this subclause:

– Procedure CAMEL_Set_ORA_Parameters;

– Procedure CAMEL_MT_GMSC_INIT;

– Procedure CAMEL_MT_MSC_ALERTING;

– Procedure CAMEL_MT_GMSC_ANSWER;

– Procedure CAMEL_MT_GMSC_DISC1;

– Procedure CAMEL_MT_GMSC_DISC2;

– Procedure CAMEL_MT_GMSC_DISC3;

– 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;

– Procedure CAMEL_MT_LEG2_GMSC;

– Process CAMEL_MT_LEG1_GMSC;

– Procedure CAMEL_MT_RECONNECT_GMSC;

– Procedure CAMEL_T_SCUDIF_MSC.

NOTE: Procedure CAMEL_MT_GMSC_DISC3 applies to CAMEL Phase 1 only.

The procedure Send_ACM_If_Required is specified in 3GPP TS 23.018 [12].

The procedure CAMEL_MT_LEG2_GMSC supervises the terminating party only. The process CAMEL_MT_LEG1_GMSC supervises the originating party only. Hence, signals from the destination exchange are received by the procedure CAMEL_MT_LEG2_GMSC and signals from the originating exchange are received by the process CAMEL_MT_LEG1_GMSC.

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

4.5.3.1.1 Action of the GMSC on receipt of Int_Release_Call

An ISUP Release message is sent to the originating exchange and resources are released.

4.5.3.1.2 Action of the GMSC on receipt of Int_Error

The GMSC checks the default call handling parameter in the T‑CSI.

If the default call handling is release call, an ISUP Release message 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 continues call handling without CAMEL support.

4.5.3.1.3 Action of the GMSC on receipt of Int_Continue

If an FTN has been stored then the information received from the HLR is used to overwrite the 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 then a Send Routeing Info information flow including a T‑CSI suppression parameter is sent to the HLR. The Send Routing Info information flow includes an indication of which CAMEL Phases are supported by the GMSC/gsmSSF.

4.5.3.1.4 Action of the GMSC on receipt of Int_Continue_With_Argument

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

If no FTN has been stored then a Send Routeing Info information flow including a T‑CSI suppression parameter is sent to the HLR. The Send Routing Info information flow includes an indication of which CAMEL phases are supported by the GMSC/gsmSSF.

The MSC shall replace the call parameters by the information received in the Int_Continue_With_Argument signal. Call parameters which are not included in the Int_Continue_With_Argument message are unchanged.

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.

4.5.3.1.5 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 29.078 [36]): Calling Partys Category and Generic Number. If received, the Announcement Suppression Indicator is stored. The further processing is described in subclause 4.5.3.1.3 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 CS_gsmSSF, an ISUP Release Message is sent to the originating exchange. The MSC then releases all call resources and the procedure CAMEL_MT_GMSC_INIT returns result=fail.

Otherwise the following parameters, if received, are used to overwrite the corresponding ISUP parameters (for mapping see 3GPP TS 29.078 [36]): 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 signal 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.

4.5.3.1.6 Action of the GMSC on receipt of Send_Routeing_Info Negative Response (in state Wait_For_Routeing_Info_2)

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

4.5.3.1.7 Action of the GMSC on receipt of Send_Routeing_Info ack with MSRN (in state Wait_For_Routeing_Info_2)

An ISUP IAM with the MSRN as the called party number is constructed.

4.5.3.1.8 Action of the GMSC on receipt of Send_Routeing_Info ack with FTN (in state Wait_For_Routeing_Info_2)

The information received from the HLR is used to overwrite the corresponding call parameters (for details see 3GPP TS 23.018 [12]). The redirection counter is incremented.

4.5.3.1.9 Action of the GMSC on receipt of Send_Routeing_Info ack with O‑CSI and/or D‑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 the FTN. The O‑CSI and/or D‑CSI is stored.

4.5.3.1.10 Action of the GMSC in procedure CAMEL_MT_ETC

In the 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".

4.5.3.1.11 Action of the GMSC in procedure CAMEL_MT_GMSC_Notify_CF

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

The Int_DP_T_No_Answer signal and Int_DP_T_Busy signal include a parameter to indicate that the call has encountered conditional call forwarding. The gsmSSF will transfer this parameter to the Event Report BCSM information flow which it sends to the gsmSCF.

4.5.3.1.12 Action of the MSC on receipt of Int_Disconnect_Leg (Leg 2)

If the MSC receives Int_Disconnect_Leg (Leg 2) signal from the gsmSSF, in response to an Initial DP information flow, the MSC will continue the handling of the calling party (Leg1) without routeing the call to a destination.

Figure 4.41-1: Procedure CAMEL_Set_ORA_Parameters (sheet 1)

Figure 4.42-1: Procedure CAMEL_MT_GMSC_INIT (sheet 1)

Figure 4.42-2: Procedure CAMEL_MT_GMSC_INIT (sheet 2)

Figure 4.42-3: Procedure CAMEL_MT_GMSC_INIT (sheet 3)

Figure 4.42-4: Procedure CAMEL_MT_GMSC_INIT (sheet 4)

Figure 4.42-5: Procedure CAMEL_MT_GMSC_INIT (sheet 5)

Figure 4.42-6: Procedure CAMEL_MT_GMSC_INIT (sheet 6)

Figure 4.42-7: Procedure CAMEL_MT_GMSC_INIT (sheet 7)

Figure 4.42-8: Procedure CAMEL_MT_GMSC_INIT (sheet 8)

Figure 4.43-1: Procedure CAMEL_MT_MSC_ALERTING (sheet 1)

Figure 4.43-2: Procedure CAMEL_MT_MSC_ALERTING (sheet 2)

Figure 4.43-3: Procedure CAMEL_MT_MSC_ALERTING (sheet 3)

Figure 4.44-1: Procedure CAMEL_MT_GMSC_ANSWER (sheet 1)

Figure 4.44-2: Procedure CAMEL_MT_GMSC_ANSWER (sheet 2)

Figure 4.44-3: Procedure CAMEL_MT_GMSC_ANSWER (sheet 3)

Figure 4.45-1: Procedure CAMEL_MT_GMSC_DISC1 (sheet 1)

Figure 4.46-1: Procedure CAMEL_MT_GMSC_DISC2 (sheet 1)

Figure 4.46-2: Procedure CAMEL_MT_GMSC_DISC2 (sheet 2)

Figure 4.47-1: Procedure CAMEL_MT_GMSC_DISC3 (sheet 1)

Figure 4.48-1: Procedure CAMEL_MT_GMSC_DISC4 (sheet 1)

Figure 4.48-2: Procedure CAMEL_MT_GMSC_DISC4 (sheet 2)

Figure 4.48-3: Procedure CAMEL_MT_GMSC_DISC4 (sheet 3)

Figure 4.49-1: Procedure CAMEL_MT_GMSC_DISC5 (sheet 1)

Figure 4.49-2: Procedure CAMEL_MT_GMSC_DISC5 (sheet 2)

Figure 4.49-3: Procedure CAMEL_MT_GMSC_DISC5 (sheet 3)

Figure 4.50-1: Procedure CAMEL_MT_GMSC_DISC6 (sheet 1)

Figure 4.51-1: Procedure CAMEL_MT_ETC (sheet 1)

Figure 4.51-2: Procedure CAMEL_MT_ETC (sheet 2)

Figure 4.51-3: Procedure CAMEL_MT_ETC (sheet 3)

Figure 4.51-4: Procedure CAMEL_MT_ETC (sheet 4)