TABLE OF CONTENTS The cell-reselection procedure may also trigger the cell-update procedure. This procedure is used to update the UTRAN registers about the location of the UE. Note that in 3G, the mobility concept is handled separately in both the UTRAN and the CN.
The CN level of mobility is handled with MM tasks. There are two location concepts at the CN level. Location areas are used by the circuit-switched network and routing areas by the packet-switched network. The location area of a UE is stored in the MSC/VLR, where it is used to route the paging messages to the right area. The routing area information of a UE is stored in the SGSN, where it is used for packet-switched paging. If a UE crosses a location area/routing area border, it initiates a location area/routing area update toward the CN. Optionally, the network may also demand that these registrations be done periodically. A successful registration will be acknowledged by the network, which may at the same time issue a new temporary mobile subscriber identity (TMSI) to the UE. If the CN has to page the UE, it will usually do so by referring to its recently assigned alias: the TMSI.
At the UTRAN level, the location concepts are the registration area and the cell area, which are independent of the CN location concepts. The UTRAN location concepts are only valid and used when the UE is in the RRC connected mode. They are also only visible within the...
