13.18 Modification of the Access Bearer

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

13.18.1 Modification of Bearer Characteristics

The modification of the access bearer is possible during a call establishment and during an active call. If the MSC server needs to modify the access bearer, the existing bearer termination in the MGW is modified or a new access side bearer termination is created. The modification of the access bearer shall be performed in accordance with 3GPP TS 25.413 [26] or 3GPP TS 48.008 [27].

13.18.1.1 Iu mode

If the link characteristics for the existing access bearer need to be changed and the MSC server previously received a notification from the MGW that modification of link characteristics of the current transport connection is supported [refer to 26], the MSC server shall use the Modify Bearer Characteristics procedure to provide the MGW with the new bearer characteristics for the existing access side bearer termination. After the MGW has replied, the MSC server shall initiate the access bearer modification towards RAN.

If the MSC server has not previously received a notification from the MGW that modification of existing link characteristics is supported, the MSC server shall use the Prepare Bearer procedure to request the MGW to add a new context and a new access side bearer termination, and to provide a bearer address and a binding reference. After the MGW has replied, the MSC server shall initiate the access bearer modification towards RAN using the provided bearer address and the binding reference. Upon successful access bearer modification, the MSC server shall connect the new access side bearer termination to the old context and release the old access side bearer termination.

If the user plane mode of the modified access bearer is "Support Mode", the Iu UP will also be re-initialised as defined in [20].

13.18.1.2 A/Gb mode

The MSC server shall use the Modify Bearer Characteristics procedure for A interface TDM termination and may use the Modify Bearer Characteristics procedure or the Configure RTP Connection procedure for AoIP termination to the MGW to provide the new bearer characteristics for the existing access side bearer termination. After the MGW has replied, the MSC server shall initiate the access bearer modification towards GERAN.

13.18.2 IWF Protocol Change

If the MSC server has requested indication on IWF protocol events, the MGW informs the MSC server about changes related to IWF protocol, using the Protocol Negotiation Result and Rate Change procedures.

For AoIP terminations there shall be no change to the AoIP Transport Layer Address (MGW) and AoIP Transport Layer Address (BSS) for Rate Changes in data calls. Instead the MSC shall include the previously returned Local Connection Address in any subsequent Assignment request to the BSS.