ve a signalling connection, and in the radio interface dedi- cated or common channels can be used [7]. When an established signalling connection exists over the Dedicated Control Service Access Point (DC-SAP) from the access stratum, the CN reaches the UE by a dedicated connection SAP on the CN side with a context between UTRAN and UE for the given connection. This context disappears when the connection is released and a dedicated connection can be initiated only from the UE. When a dedicated connection does not exist, the CN reaches the UE through the notifi- cation SAP, where the CN message may request the UE to establish a dedicated connec- tion. The UE is addressed with a user/terminal identity and a geographical area. The location of the UE is known either at cell level (higher activity) or in a larger area consisting of several cells (lower activity). Knowing the location minimizes the number of location update messages for moving UEs with low activity and removes paging needs for UEs with high activity. The UMTS Network and Radio Access Technology 3.5.2 Impacts of Mobility Handling In the presence of a dedicated connection to the UE, the UTRAN handles the UE radio interface mobility, such as soft handover, and procedures for handling mobility in the RACH/PCH substrate. The radio network cell structure should not necessarily be known outside the UTRAN. In the absence of a dedicated connection to the UE, mobility handling occurs directly between the UE and CN outside the access stratum, e.g. through registration procedures. While paging the UE, the CN indicates a geographical area which becomes the actual paged cell in UTRAN. Within a cell structure we may use location area identities or other means to identify a geographical area independently. While a dedicated connection lasts, the UE suppresses its registrations to the CN and re- registers if required. Thus, the UTRAN does not contain any permanent location regis- ters for the UE, but only temporary contexts for the duration of the dedicated connec- tion