a roll off a = 0.22 and a bandwidth equal to the chip rate. Table 5.7 Transmitter Average Power Control Range Transmitter power control range after 10 Transmitter power control range equal TPC_cmd groups after 7 equal TPC_cmd groups TPC_cmd 1 dB step size 2 dB step size 3 dB step size Lower Upper Lower Upper Lower Upper 0,0,0,0,+1 0,0,0,0,-1 The UMTS Network and Radio Access Technology 5.3.3.1.3 Uplink Power Control TDD Through the uplink power control, the UE transmitter sets its output power taking into account the measured downlink path loss, values determined by higher layer signalling and filter response a. This power control has an initial error accuracy of less than +9 dB under normal conditions and +12dB under extreme conditions. From [2] we define the power control differential accuracy as the error in the transmitter power step, originating from a step in SIRTARGET when the parameter a = The step in SIR +TARGET is rounded to the closest integer dB value. The error does not exceed the values illustrated in Table 5.8. Table 5.8 Transmitter Power Step Tolerance in Normal Conditions SIRTARGET (dB) Transmitter power step tolerance (dB) ASIRTARGET 1 1 ASIRTARGET 2 2 < ASIRTARGET 3 3 < ASIRTARGET 10 10 < ASIRTARGET 20 20 < ASIRTARGET 30 30 < IRTARGET 1 For extreme conditions the value is +12. 5.3.3.2 Base Station In FDD the transmitter uses a quality-based power control on both the uplink and downlink to limit the interference level. In TDD the transmitter uses a quality-based power control primarily to limit the interference level on the downlink. Through inner loop power control in the downlink the FDD BS transmitter has the abil- ity to adjust the transmitter output power of a code channel in accordance with the cor- responding TPC symbols received in the uplink. In the TDD inner loop control is based on SIR measurements at the UE receiver and the corresponding TPC commands are generated by the UE, although the latte may or does also apply to the FDD. 5.3.3.2.1 Power control steps The power control step cha