5 General Circuit Switched Core Network Domain Architecture

23.2053GPPBearer-independent circuit-switched core networkRelease 17Stage 2TS

5.1 Logical Architecture

The overall CS core network logical architecture is shown in figure 1.

5.1.1 CS Core Network Nodes

5.1.1.1 MSC Server

The MSC server mainly comprises the call control and mobility control parts of a GSM/UMTS MSC as described in 3GPP TS 23.002 [2]. It is also integrated with a VLR to hold the mobile subscriber’s service data and CAMEL related data.

The MSC server terminates the user-network signalling (see 3GPP TS 24.008 [4]) and translates it into the signalling over the Nc interface. The MSC Server terminates the Iu control plane signalling and its transport bearer (see 3GPP TS 25.413 [26] and 3GPP TS 25.412 [30]). It also terminates the signalling over the Mc interface with the Media Gateway.

The MSC server controls the parts of the call state model that pertain to connection control for media channels in an MGW. It also contains the "Call Control Function" in the BICC model.

5.1.1.2 GMSC Server

The GMSC server mainly comprises the call control and mobility control parts of a GSM/UMTS GMSC as described in 3GPP TS 23.002 [2].

The GMSC server terminates the signalling over the Nc interface and the call control interfaces to the external networks. It also terminates the signalling over the Mc interface towards the Media Gateway.

The GMSC server controls the parts of the call state model that pertain to connection control for media channels in an MGW. It also contains the "Call Control Function" in the BICC model.

5.1.1.3 Media Gateway

The Media Gateway terminates the signalling over the Mc interface from the (G)MSC servers. The Media Gateway terminates the Iu transport network control plane signalling with its transport bearer (see 3GPP TS 25.410 [31] and 3GPP TS 25.414 [32]). The Media Gateway also terminates the Iu user plane protocol (see 3GPP TS 25.415 [20]). It also terminates the bearer control signalling and the transport bearer over the Nb interface (see 3GPP TS 29.414 [21] and 3GPP TS 29.415 [7]).

The Media Gateway contains bearer terminations and media manipulation equipment (e.g. transcoders, echo cancellers, or tone senders). It may perform media conversion and framing protocol conversion.

5.1.2 CS Core Network Interfaces and Reference Points

5.1.2.1 Mc Interface

The Mc reference point in the present document considers the aspects of the interface between the (G)MSC server and the MGW. The H.248 protocol [5] together with 3GPP specific extensions/packages shall be used over the Mc interface.

5.1.2.2 Nc Interface

The Network-Network based call control is used over the Nc interface. Any suitable call control protocol may be used over the Nc interface (e.g. BICC).

5.1.2.3 Nb Interface

The bearer control signalling and transport are carried over the Nb interface.

5.2 Network Interworking

5.2.1 Interworking on the Nc Reference Point

Interworking between the Nc reference point, call control protocols and ISUP is defined within the 3GPP stage 3 documentation for each protocol (or by references specified in stage 3 documentation [6]).

5.2.2 Interworking on the Nb Reference Point

The interworking is specified in 3GPP TS 29.415 [7] and 3GPP TS 29.414 [21].