7.4 MGW Initiated

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

The following clauses describe the additional requirements for MGW initiated call clearing in the bearer independent CS core network.

7.4.1 GMSC server

7.4.1.1 Bearer released on the destination side

After the GMSC server has received the Bearer Released procedure from the MGW, it shall send the Release message to the succeeding node. Once the succeeding node has sent the Release Complete message, the GMSC server releases any MGW allocated resources for the destination side. The GMSC server uses the Release Termination procedure to request the MGW to remove the destination side bearer termination.

The call clearing to the incoming side is performed as described in clause 7.1.1.2, call clearing to the outgoing side.

7.4.1.2 Bearer released on the originating side

After the GMSC server has received the Bearer Released procedure from the MGW, the GMSC server sends the Release message to the preceding node. Once the preceding node has sent the Release Complete message, the GMSC server releases any MGW allocated resources for the originating side. The GMSC server uses the Release Termination procedure to request the MGW to remove the originating side bearer termination.

If the call is already established towards the destination side, call clearing to the destination side is performed as described in clause 7.1.1.2, call clearing to the outgoing side.

7.4.2 MSC server

7.4.2.1 Bearer released on the access side

After the MSC server has received the Bearer Released procedure from the MGW, the MSC server initiates the call clearing towards the UE and requests release of the allocated radio resources as described in 3GPP TS 23.108 [18]. Once the call clearing and the radio resources release have been completed, the MSC server releases any MGW allocated resources for the access side. The MSC server uses the Release Termination procedure to request the MGW to remove the access side bearer termination.

If the call is already established towards the network side, call clearing to the network side is performed as described in clause 7.2, call clearing to the network side.

7.4.2.2 Bearer released on the network side

After the MSC server has received the Bearer Released procedure from the MGW, the MSC server sends the Release message to the preceding/succeeding node. Once the preceding/succeeding node has sent the Release Complete message, the MSC server releases any MGW allocated resources for the network side. The MSC server uses the Release Termination procedure to request the MGW to remove the network side bearer termination (bullet 1 and bullet 2 in figure 7.8).

Call clearing to the UE is performed as described in clause 7.1.2.2, call clearing to the UE (bullet 3 in figure 7.8).

7.4.2.3 Example

Figure 7.7 shows the network model for an MGW initiated clearing of a mobile call. The "squared" line represents the call control signalling. The "dotted" line represents the bearer control signalling (not applicable in A/Gb mode for the A-interface) and the bearer. The MSC server seizes one context with two bearer terminations in the MGW. Bearer termination T1 is used for the bearer towards RNC/BSC and bearer termination T2 is used for the bearer towards succeeding MGW.

Figure 7.7: MGW Initiated Call Clearing (Network model)

Figure 7.8 shows the message sequence example for the MGW initiated clearing of a mobile call. After the MSC server is notified that the MGW has released the network side bearer, the MSC server initiates call clearing of the network side and the access side. After the call clearing towards the UE and the radio resource release have been completed the MSC server requests release of the access side bearer termination. Once the preceding/succeeding node has indicated that call clearing has been completed, the MSC server requests the release of the network side bearer termination.

Figure 7.8: MGW Initiated Call Clearing (message sequence chart)