21.3 Transfer of call handling

29.0023GPPMobile Application Part (MAP) specificationRelease 17TS

21.3.1 General

The message flow for successful transfer of call handling to forward a call is shown in figure 21.3/1.





5) I_REL (Note 1)

6) I_IAM (Note 1)

NOTE 1: TUP or ISUP may be used in signalling between MSCs, depending on the network type between the MSCs. For further details on the TUP and ISUP procedures refer to the following ITU-T Recommendations & ETSI specification:

– Q.721‑725 ‑ Telephone User Part (TUP);

– ETS 300 356-1 ‑ Integrated Services Digital Network (ISDN); Signalling System No.7; ISDN User Part (ISUP) version 2 for the international interface; Part 1: Basic services.

NOTE 2: Services printed in italics are optional.

Figure 21.3/1: Message flow for transfer of call handling

If the HLR indicated in the response to the original request for routeing information that forwarding interrogation is required, the GMSC executes the Send Routeing Information procedure with the HLR to obtain forwarding information; otherwise the GMSC uses the forwarding data which were sent in the MAP_RESUME_CALL_HANDLING req/ind.

21.3.2 Process in the VMSC

The MAP process in the VMSC to retrieve routeing information for a mobile terminating call is shown in figure 21.3/2. The MAP process invokes macros not defined in this clause; the definitions of these macros can be found as follows:

Receive_Open_Cnf see clause 25.1.2;

Check_Confirmation see clause 25.2.2.

If the capacity of a message signal unit in the lower layers of the protocol is enough to carry all the information which has to be sent to the GMSC, the test "Segmentation needed?" takes the "No" exit; otherwise the test takes the "Yes" exit.

21.3.3 Process in the GMSC

The MAP process in the GMSC to handle a request for the GMSC to resume call handling is shown in figure 21.3/3. The MAP process invokes a macro not defined in this clause; the definition of this macro can be found as follows:

Receive_Open_Ind see clause 25.1.1;

If the parameter All Information Sent was present in the MAP_RESUME_CALL_HANDLING indication, the test "All Information Sent" takes the "Yes" exit; otherwise the test takes the "No" exit.

Figure 21.3/2: Process RCH_VMSC

Figure 21.3/3: Process RCH_GMSC