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27 series - R interface protocols and terminal adaptation functions

27.005 - Use of Data Terminal Equipment - Data Circuit terminating Equipment (DTE-DCE) interface for Short Message Service (SMS) and Cell Broadcast Service (CBS) 27.103 - Not available in this release 27.003 - Terminal Adaptation Functions (TAF) for services using Synchronous bearer capabilities 27.002 - Terminal Adaptation Functions (TAF) for services using Asynchronous bearer capabilities 27.001 - General on Terminal Adaptation Functions (TAF) for Mobile Stations (MS) 27.010 - Terminal Equipment to User Equipment (TE-UE) multiplexer protocol 27.060 - Packet domain; Mobile Station (MS) supporting Packet Switched services 27.007 - AT command set for User Equipment (UE) Up to the UMTS specifications


The mobile equipment (ME) contains all the components of the UE apart from the UICC. In voice mobiles, the ME is usually a single device, but in the case of data terminals, the functions are often split in two:

  • MT: This handles radio transmission and reception (eg a plug-in UMTS card for a laptop).
  • TE: This handles data input and output (eg the laptop itself).

The 27 series covers the R interface between the MT and the TE, and the terminal adaptation function (TAF) that the MT requires in order to communicate with the TE. The R interface is not fully specified by 3GPP: instead, it can use a variety of open standards such as IrDA or PCMCIA. A few issues are specified here, however:

  • The mechanisms that are used to transfer CS data streams, PS data streams and SMS messages between the TE and the MT.
  • A set of AT commands, which are used to exchange signalling messages between the TE and the MT.
  • The functions that the MT requires in order to transfer signalling messages and data between the R interface and the radio interface.
  • A multiplexer protocol, which allows the simultaneous transfer of several different data streams over a single serial link.


IrDAInfrared data association
MTMobile termination
TETerminal equipment
CSCircuit switched
PCMCIAPersonal computer memory card international association
PSPacket switched
SMSShort message service
TAFTerminal adaptation function
UEUser equipment
UICCUniversal integrated circuit card
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