4 Assumed UMTS Architecture

25.3013GPPRadio interface protocol architectureTS

Figure 1 shows the assumed UMTS architecture as outlined in [1]. The figure shows the UMTS architecture in terms of its entities User Equipment (UE), UTRAN and Core Network. The respective reference points Uu (Radio Interface) and Iu (CN-UTRAN interface) are shown. The figure illustrates furthermore the high-level functional grouping into the Access Stratum and the Non-Access Stratum.

The Access Stratum offers services through the following Service Access Points (SAP) to the Non-Access Stratum:

– General Control (GC) SAPs;

– Notification (Nt) SAPs; and

– Dedicated Control (DC) SAPs.

The SAPs are marked with circles in Figure 1.

Figure 1: Assumed UMTS Architecture

The model in Figure 1 distinguishes the end AS entities [1], which provide the services to higher layers, from the local entities, which provide services over respectively the Uu and the Iu reference points.

The Uu Stratum (UuS) block includes the radio interface protocol stack described in subclause 5.1.