09.133GPPSignalling interworking between ISDN supplementary services Application Service Element (ASE) and Mobile Application Part (MAP) protocolsTS
4.1 GSM CCBS Architecture Overview
The stage 1 of the CCBS service is defined in GSM 02.93.
The network architecture to support the CCBS service in GSM networks is defined in GSM 03.93. For convenience, the architecture is shown again in this specification. Figure 4.1.1 is an architectural overview of the CCBS service when interworking between the originating and the destination networks involved. The originating network may be a mobile network or a fixed network and the destination network may also be a mobile network or a fixed network.
The call related signalling (see ETS 300 356-18) for CCBS is performed on ISUP links on the following interfaces:
VMSC A – GMSC B;
VMSC A – DLE;
OLE – GMSC B;
whereas the specific CCBS procedures (see ETS 300 356-18) are performed via the SSAP protocol, which is signalled on the following interfaces:
HLR A – HLR B;
HLR A – DLE;
OLE – HLR B.
This specification only describes the MAP – SSAP protocol interworking.
Figure 4.1: Architectural overview showing common point of interworking
4.2 GSM CCBS – ISDN CCBS ASE Interworking Overview
The non-call related signalling procedures for CCBS between the originating network and the destination network are defined in ETS 300 356-18 as the ISDN CCBS-ASE. The GSM network also uses these signalling procedures for CCBS without any changes. The ISDN CCBS ASE protocol is supported in GSM networks in the HLR A (originating network) and HLR B (destination network). Therefore no protocol interworking for ISDN CCBS-ASE is needed for the CCBS service between GSM networks and ISDN networks.
In GSM networks, the CCBS functionality is distributed across several network entities (see GSM 03.93) including the HLR, VLR, MSC and the MS. The HLR shall provide any necessary signalling interworking between the MAP protocol for call completion services on the MAP D-interface (between the VLR and the HLR) and ISDN CCBS-ASE protocol between the originating and destination networks.
The MAP protocol for CCBS service is specified in GSM 09.02. The ISDN CCBS-ASE protocol is specified in ETS 300 356‑18. This specification clarifies the interworking within the HLR between these protocols.
4.3 Overview on the use of CCBS procedures and parameters values
A GSM subscriber can roam while there is an active CCBS request. The called party address (MSISDN) information is used to initiate a dialogue with the destination network on the SSAP interface. The dialogue on the SSAP interface is opened and maintained while there is an active CCBS request (see ETS 300 356-18). However, the dialogues on the MAP D interface can be closed and reopened as necessary (see GSM 09.02 and GSM 03.93) and use the IMSI information for addressing.
4.4 Mapping between MAP and SSAP application layer messages
The mapping of MAP messages on the D interface and SSAP messages between the originating and destination networks is described. The precise coding of these messages is given in GSM 09.02 and ETS 300 356-18.
4.4.1 MAP D-interface to SSAP interface mapping in HLR A
Table 4.1: Mapping of GSM 09.02 (MAP) operations to ETS 300 356-18 (SSAP) operations
EraseCCEntry/ A GSM 03.93 Event (note 1)
A GSM 03.93 Event (note 2)
A GSM 03.93 Event (note 3)
NOTE 1 This event may be local to HLR A. See GSM 03.93 for a dynamic description of possible events in HLR A leading to a CCBS request being cancelled. The SSAP CcbsCancel operation can include a cause code parameter; this shall be set to the appropriate value corresponding to the actual dynamic event by HLR A (e.g. cCBS-T3-Timeout, cCBS-T4-Timeout).
NOTE 2 This event may be local to HLR A. See GSM 03.93 for a dynamic description of possible events in HLR A leading to a CCBS request being suspended.
NOTE 3 This event may be local to HLR A. See GSM 03.93 for a dynamic description of possible events in HLR A leading to a CCBS request being resumed.
4.4.2 SSAP interface to MAP D-interface interface mapping in HLR A
SetReportingState/A GSM 03.93 Event (note 1)
NOTE 1 This event may be local to HLR A. See GSM 03.93 for a dynamic description of possible events in HLR A resulting from a CCBS request being cancelled. The SSAP CcbsCancel operation can include a cause code parameter(e.g. cCBS-T7-Timeout, cCBS-T9-Timeout).