18 (G)MSC MGW Tandeming

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

In all call flow examples a (G)MSC server may tandem (either during call setup or during an active call, as part of an application layer service invocation) the bearer through one or more MGWs under its control, in order to access bearer resources which may be distributed over a number of specialised MGWs.

18.1 Example of use of MSC MGW Tandeming during call setup to provide bearer access to specialised MGW resources

Figure 18.1A: MSC before MGW Tandeming during call setup to provide bearer access
to specialised MGW resources (Network model)

Figure 18.1B: MSC after MGW Tandeming during call setup to provide bearer access
to specialised MGW resources (Network model)

The figure 18.2 below shows the message sequence example for MSC MGW Tandeming during call setup to provide bearer access to specialised MGW resources. In the example, after the signalling towards MSC server A and the bearer towards the MGW B is established, MSC server A requests the MGW B to tandem the bearer and terminate it at MGW C, where specialised bearer resources which are not available at MGW B may be provided.

Figure 18.2: MSC MGW Tandeming during call setup to provide bearer access
to specialised MGW resources (message sequence chart)