2 Reference Configuration

27.0023GPPTerminal Adaptation Functions (TAF) for services using asynchronous bearer capabilitiesTS

3GPP TS 27.001 [10], 3GPP TS 23.101 [6] and 3GPP TS 24.002 [3] describe the basic reference configurations.

2.1 Customer Access Configuration

This configuration is as shown in figure 1 of 3GPP TS 24.002 [3]. The present document specifically refers to the Mobile Terminations (MTs) which support terminals of the type TE1 and TE2 with asynchronous capabilities. The TAF is functionally a part of an MT1, MT2 or MT0 with an integral asynchronous data capability.

2.2 Terminal Adaptation Function (TAF)

The TAF provides facilities to allow manual or automatic call control functions associated with circuit switched services. The following functions are also included:

‑ Conversion of electrical, mechanical, functional and procedural characteristics of the ITU-T  V series and ISDN type interfaces to those required by the PLMN.

‑ Bit rate adaptation of the ITU-T  V series data signalling rates and the ISDN 64 kbit/s to that provided in the PLMN.

‑ The mapping functions necessary to convert automatic calling and/or automatic answering procedures of the ITU-T  recommendation V.250 [22] and parameters for asynchronous operation.

‑ The mapping functions necessary to convert S interface signalling to the PLMN Dm channel signalling.

‑ Flow control (in some cases resulting in non‑transparency of data as described in 4.3).

‑ Layer 2 Relaying (see annex A).

‑ In‑call modification function.

‑ Synchronization procedure, which means the task of synchronizing the entry to and the exit from the data transfer phase between two user terminals. This is described in 3GPP TS 27.001 [10].

‑ Filtering of channel control information as described in 3GPP TS 27.001 [10].

‑ Terminal compatibility checking.

– Splitting and combining of the data flow in case of multiple substream data configurations.