tion takes place when the network is having a high load, and resources used by non-real-time services are needed for real time users or higher priority Parameter Planning URA_PCH CELL_PCH CELL_DCH CELL_FACH Figure 2.44 Packet data transfer states non-real-time services. The target and overload thresholds define the operating space of the packet scheduler - the RRM functionality that controls allocated packet data bit rates. In the case of an overload situation packet data services are downgraded until the measured load reaches the load target. If the load is on a marginal load area no action is taken as the non-real-time services are not allowed to be upgraded and no downgrading takes place. On a feasible load area packet data services are upgraded if there is a capacity request indicating that one or more non-real-time services requires more capacity. Figure 2.44 shows the different packet transfer states. In idle mode no service has been established and no radio bearer has been established. In Cell_DCH the dedicated physical channel carries the data and the throughput can vary according to allocated resources. In Cell_FACH the common channels (FACH on the downlink and RACH on the uplink) are used to transmit small amounts of data. The UE moves first to the Cell_DCH state when there is a date to be transferred; if there is a period of inactivity both in the uplink and downlink the dedicated channel is released and the UE moves to the Cell_FACH state. From Cell_FACH the UE moves back to Cell DCH if the data buffer becomes full and a capacity request is sent. The UE moves from Cell_FACH to Cell_PCH or URA_PCH if a prolonged period of inactivity triggers an inactivity timer. The selection to move to URA_PCH is made if the mobile has been changing cells several times in the location update period; if the UE stays within a cell then Cell_PCH is selected. In Cell_PCH the UE camps on one cell area and indicates using a cell update message whether it has data to transfer or if it changes a cell. On URA_PCH the UE mows w