TABLE OF CONTENTS In GSM as in many other 2G systems, the radio resource protocol states were generally divided into two groups: the idle and the connected states. In the idle state no dedicated radio resources existed between the UE and the base station. We should observe, however, that the idle state is a rather poor name, as the mobile station is far from being "idle." There are several idle-mode tasks it must handle, tasks such as neighbor cell monitoring, cell reselection, paging channel reception, and broadcast data reception. In the connected state, however, a duplex radio connection is in place. The boundary between the idle and the connected mode is pretty clear; it is the existence of a dedicated radio resource.
The idle state in UMTS is similar to GSM as well as to those we find in other 2G systems: there is no uplink connection whatsoever. The UE has to monitor its radio environment regularly and, when necessary, perform a cell-reselection task. The reception of the broadcast system information and paging messages belong to the UE's idle-mode tasks.
The connected state is different from the corresponding state in circuit-switched 2G systems, but it has similarities with the packet-switched GPRS system. The connected mode is divided into four states (see Figure 7.22).
CELL_DCH is a state in which a dedicated connection exists in both directions. This state is entered while an RRC connection is established, and it is abandoned when the connection is...
