19.2.3 Procedure in MSC‑B

29.0023GPPMobile Application Part (MAP) specificationRelease 17TS

This clause describes the handover or relocation procedure in MSC‑B; it covers basic handover or relocation from the controlling MSC (MSC‑A) and subsequent handover or relocation.

The MAP process in MSC‑B to handle handover or relocation is shown in figure 19.2/5. The MAP process invokes macros not defined in this clause; the definitions of these macros can be found as follows:

Receive_Open_Ind see clause 25.1.1;

Receive_Open_Cnf see clause 25.1.2;

Check_Indication see clause 25.2.1.

Check_Confirmation see clause 25.2.2.

Communication between the MAP handover process and the Handover Control application is represented by the HO_CA_MESSAGE service. For a detailed description of the interworking between the Handover Control applications in different MSCs for the inter-MSC handover procedure, see 3GPP TS 23.009 [21].

The ordering of allocation of handover number and radio resources shown in the SDL diagrams is not mandatory.

19.2.3.1 Basic handover

The handling in MSC‑B for basic inter-MSC handover is shown in sheets 1 to 7 of figure 19.2/5.

Sheet 2: If the MAP_PREPARE_HANDOVER indication included a parameter requesting multiple bearers but MSC‑B does not support multiple bearers, MSC‑B sends a MAP_PREPARE_HANDOVER response indicating that multiple bearers are not supported, and waits for a possible MAP_PREPARE_HANDOVER indication requesting handover of a single bearer.

Sheet 6: If the original MAP_PREPARE_HANDOVER indication included a parameter indicating that handover number allocation is not required, MSC‑A may send a further MAP_PREPARE_HANDOVER request to request the allocation of a handover number (or one or more relocation numbers).

19.2.3.2 Handling of access signalling

The Handover Control application in MSC‑A may forward access signalling to any of the MS, RNS‑B or BSS‑B using the MAP_FORWARD_ACCESS_SIGNALLING service; any of the MS, RNS‑B or BSS‑B may forward access signalling to the Handover Control application in MSC‑A using the MAP_PROCESS_ACCESS_SIGNALLING service. These are non-confirmed services. Signals to or from any of the MS, RNS‑B or BSS‑B are routed through the Handover Control application in MSC‑B.

19.2.3.3 Subsequent handover

The handling in MSC‑B for subsequent inter-MSC handover is shown in sheet 8 of figure 19.2/5.

While the MAP process in MSC‑B is waiting for the completion of subsequent handover, it relays access signalling between MSC‑A and the MS, RNS‑B or BSS‑B through the Handover Control application as described in clause 19.2.3.2.