ISO/IEC 21989:2002 specifies the Short Message Service (SMS).

SMS enables a user to send and receive Short Messages (SMs) to and from another user.

This service is based on GSM 03.40. The Service Centre functionality described in ISO/IEC 21989:2002 is equal to the functionality of a Service Centre in GSM 03.40. Thus, for interoperability with a GSM network, it is only necessary to implement a QSIG interface.

NOTE 1 The interworking with other air interfaces is not precluded, but is outside the scope of this International Standard.

NOTE 2 The Short Message Service is a special kind of basic service but is described in this document in the style of a supplementary service.

Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. ISO/IEC 21989:2002 contains the stage 1 and stage 2 specifications of SMS. The stage 1 specification specifies the service as seen by users of PISNs. The stage 2 specification identifies the functional entities involved in the service and the information flows between them.