UMTS Networks : Architecture, Mobility and Services

UMTS Radio Access Network 135
Figure 5.33 Basic structure of system information in the UTRAN
The RNC may handle the constructing process together with the BS (e.g., when
modifying system information scheduling). Nevertheless, the controlling function of
system information belongs entirely to the RNC. Once the RNC has structured the
system information data it forwards the information to the BS to be broadcast over the
air interface to the UE. Based on the air interface situation the BS informs the RNC
about the ability to broadcast system information on the Uu interface (Figure 5.34).
5.3.2.2 Initial Access and Signalling Connection Management
Before the RNC can map any requested RABs to the RB, it needs to create the
signalling connection between the UE and the CN. In this context, 3GPP TR 25.990
defines the signalling connection as an acknowledgement-mode link between the UE and
the CN to transfer higher layer information between the entities in the Non Access