scope:

This European Telecommunication Standard (ETS) gives the stage 2 description of Unstructured Supplementary Service Data (USSD). The unstructured supplementary service data (USSD) mechanism allows the MS user and a PLMN operator defined application to communicate in a way which is transparent to the MS and to intermediate network entities. The mechanism allows development of PLMN specific supplementary services. The following diagram shows how handling of USSD is carried out, independently of the applications.