23.2053GPPBearer-independent circuit-switched core networkRelease 17Stage 2TS
The procedures for facsimile group 3 transparent service toward a GSM BSS shall be followed in accordance with 3GPP TS 43.045 . The following clauses describe the additional requirements for the bearer independent CS core network.
Call and bearer establishment shall be handled as described in the Call Establishment clause with the addition that the Rate Change Event Notification shall be requested. If the MGW detects a mismatch between the radio channel rate to the facsimile transmission speed then it shall indicate this to the MSC server by use of the rate change procedure. The MSC server shall initiate a new Assignment towards the GSM RAN and if successful modify the PLMN Bearer Capability and GSM Channel Coding at the associated access bearer termination using the Modify Bearer Characteristics procedure as described in 16.2.41 to signal to the MGW that fax transmission can continue. The sequence is shown in Figure 13.19/1.
Figure 13.19/1: GSM access Channel Mode Modify message
For AoIP terminations the Configure RTP Connection Point Procedure may be used instead of the Modify Bearer Characteristics procedure.