scope:

The present docuent defines three interface protocols for control of SMS functions within a GSM mobile telephone from remote terminal via an asynchronous interface.

Clause 2 defines a binary protocol ('Block Mode"). The protocol includes error protection and is stuitable for use where the link may not be completely reliable. It will be of particular use where control of remote devices is required. Efficient transfer of binary encoded user data is possible.

Clause 3 defines a character-based interfaced based on "AT" commands ("Text Mode"). This mode is suitable for unitelligent terminals emulators, and for application software built on command structures like those defined in V.25ter. Some of the commands defined in clause 3 will also be useful for implementations of clause 2 and/or clause 4, for example enabling an indication of incoming SMS message.

Clause 4 defines a character-based interface with hex-encoded binary transfer of message blocks ("PDU Mode"). This mode is suitable for software drivers based on AT command structures which do not understand the content of the message blocks and can only pass them between the MT and "upper level" software resident in the TE.

In all three modes, the terminal is considered to be in control for SMS/CBS transactions.

The present document consider the mobile termination to be single entity. Other GSM Technical Specifications describe the split of functionality between the mobile equipment and SIM.

The three "modes" referred to above, are represented in figure 0.1/GSM 07.05.

The "Block mode" is self contained mode in its own right, and when entered, control will remain within that mode until the procedures to exit the mode are executed, after which control is returned to the V.25 ter "command" state or "on-line command" state.

The "Text" adn "PDU" modes are not in themselves V.25ter states but are simply sets of commands which will operte in either the V.25ter "command" state or "on-line command" state. The "Text" and "PDU" modes are transitory states and after each operation, control is automatically returned to the V.25ter "command" state or "on-line command" state. Whilst in the V.25ter command state, the MS is availabel to handle incoming and outgoing alls such as Data or Facsimile.

In the "Block ode" and "PDU" mode a mobile is not permitted to modify any component of an SMS/CBS message received from the air interface or an SMS mesage recieved from a TE, before passing it on, except where GSM 03.40 or GSM 03.41 defines a "component modification facility" and where this "component modification facility" is supported by the mobile. In the Text Mode the mobile may be unable to display characters coded in particular coding schemes. In this case, the mobile shall behave as described in GSM 03.38 and assume the coding scheme to be the GSM default Alphabet.