y producing a blocking effect. Thus, a closed-loop power control feature is used. In the uplink direction, the base station makes measurements of the power received from different mobiles in terms of SIR (signal-to-interference ratio). It then compares these with the target SIR. If SIR measured is greater than SIRtarget the BS will request the mobiles to reduce their transmitted power. A similar phenomenon happens in the downlink, but in this case the targets are the mobiles that are located on the cell edges, in order to provide them with sufficient power and reduce external cell interference. Something else that is used in these networks is 'slow power control', also known as 'outer-loop power control'. This is used for controlling the SIRtarget in a base station. The process is based on the needs of individual single links and is responsible for maintaining RADIO NETWORK PLANNING PROCESS quality targets in the base station and the network. As the open outer-loop power control process is based on propagation aspects in the downlink, and is not sufficient as the uplink and downlink frequencies are quite different from each other, closed-loop power control is used. The BTS receives a signal from the UE and, based on its measurements, directs the mobile to increase or decrease its power level. And these measurements are based on the received signal level per bit to the interference signal level. In the uplink direction, after the higher layers have set the uplink power, the UL control procedure starts. The power in the UL is controlled (or set) by the network. In fast power control, it adjusts the uplink power transmitted by the UE. This control is based on the SIRtarget. Another power control mode is the compressed mode. This is used in both the uplink and downlink directions, to provide faster power control. In this mode, larger steps are used so as to recover the power level for the SIR to move closer to SIRtarget (The compressed mode, or slotted mode, is needed to make inter-system or inter-frequency handovers