13.17 Alternate Speech/Fax

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

The procedures for facsimile group 3 transparent/non-transparent shall be followed in accordance with 3GPP TS 43.045 [24] and 3GPP TS 23.146 [25]. The following clauses describe the additional requirements for the bearer independent CS core network. If out-of-band transcoder control is applied for a speech call, it shall be performed in accordance with 3GPP TS 23.153 [3].

Call and bearer establishment shall be handled as described in the Call Establishment clause. In order to change from speech to fax (or vice versa), the MSC server shall modify the access bearer as described in clause 13.18.1.

If the MGW responds with an error to any of the procedures initiated by the MSC server, or the MSC server receives a Bearer Failure procedure from the MGW, the MSC server may either clear the call or reject the change from speech to fax (or vice versa).

After this possible modification, the MGW shall seize an interworking function if a PLMN Bearer Capability [4] has been supplied to the access side bearer termination. When the MSC server receives an answer indication, it shall request activation of the interworking function using the Activate Interworking Function procedure.