8 Use of terminal adaptation functions

23.1463GPPRelease 17Technical realization of facsimile Group 3 non-transparentTS

The protocol stack of the connection type is shown in figure 4.

The TAFs described in 3GPP TS 27.002 for asynchronous bearer capabilities in the non‑transparent mode. The interchange signalling mapping is in accordance with 3GPP TS 27.002.

8.1 Principles of terminal adaptation functions

The TAF, located at both PLMN ends, is in charge of:

‑ call set-up, in particular the BC negotiation;

‑ establishment and maintenance of a Layer2 protocol link between the FA and the TAF according to 3GPP TS 27.002, where applicable;

– establishment and maintenance of an L2RCOP link between the TAFs according to 3GPP TS 27.002;

– initiation of the In-Call Modification (ICM) procedure.

The basic approach of the present document for facsimile group 3 is:

‑ to use the network support of BS 20 NT as defined in 3GPP TS 27.001, 3GPP TS 27.002 and 3GPP TS 29.007.

8.2 Specific TAFs for facsimile service

In order to perform the procedures described in the present document, the UE and the IWF environment shall be designed to transmit and receive facsimile data continuously with flow control. This specifically applies between RLP entities, L2RCOP (within TAF) entities, and between the FA and the TAF entities within the UE or the IWF.

Furthermore, the RLP entity shall be able to make error recovery by using the SREJ command/response.