9.12 CS Call Clearing

3GPP43.318Generic Access Network (GAN)Release 17Stage 2TS

9.12.1 CS Call Release

The following figure shows CS call clearing initiated by the MS. This scenario assumes that the MSC uses Iu Release to release the call (i.e., versus a separate RAB Release then Iu Release).

Figure 52: MS initiated CS Call release

1. The MS sends the Disconnect message to the CN to release the call. This message is contained in the GA-RRC UL DIRECT TRANSFER message between MS and GANC. The GANC forwards the Disconnect message to the CN (i.e., using the RANAP Direct Transfer message).

2. The CN responds with a Release message to the GANC. The GANC forwards this message to the MS using the GA-RRC DL DIRECT TRANSFER message.

3. The MS responds with the Release Complete message. This message is contained within the GA-RRC UL DIRECT TRANSFER message between MS and GANC. The GANC forwards the Disconnect message to the CN.

4. The CN triggers the release of connection as described in clause 9.7.2.

9.12.2 CS Channel Release

The following figure shows CS channel release (i.e., user plane only) corresponding to the Iu RAB Release procedure.

Figure 53: CS channel release

1. The CN indicates to the GANC to release the RAB allocated to the MS (identified by the RAB ID), via the RANAP RAB Assignment Request message.

2. The GANC commands the MS to release the CS user plane channel (but maintain the CS signalling connection), using the GA-RRC DEACTIVATE CHANNEL message. The message includes the CN Domain ID (indicating CS) and the RAB ID.

3. The MS confirms CS channel release to the GANC using the GA-RRC DEACTIVATE CHANNEL COMPLETE message. The MS remains in the GA-RRC-CONNECTED state.

4. The GANC confirms resource release to CN using the RAB Assignment Response message.