The present document specifies the services provided by the Access Stratum to the rest of the system. The adopted architecture is given by TS 23.101 [2].

The present document describes the main functions visible at the boundary between the Access Stratum and the rest of the system, it describes in general terms the information flows, both control and user data, over this boundary and relevant for the Access Stratum.

The present document is the basis of the detailed specifications of the protocols which rule the information flows, both control and user data, between the Access Stratum and the parts of UMTS outside the Access Stratum, and of the detailed specifications of the UTRAN. These detailed specifications are to be found in other Technical Specifications.