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POWER CONTROL

POWER CONTROL. UMTS Seminar. Principles. The two main capabilities of Power Control in a WCDMA system are as follows: To maintain the quality of connections (including common channels needed, for example, for call access) To minimize the transmitted power in both uplink and downlink.

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POWER CONTROL

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  1. POWER CONTROL UMTS Seminar

  2. Principles • The two main capabilities of Power Control in a WCDMA system are as follows: • To maintain the quality of connections (including common channels needed, for example, for call access) • To minimize the transmitted power in both uplink and downlink

  3. Key Characteristics • Control channel power setting (DL only, Fixed) – Setting of the output power for CPICH, P-CCPCH, S-CCPCH, SCH, PICH, AICH • Open loop power control (Subject to power control) – Power control during random access# (UL) – DL DPDCH/DPCCH setting (and DL ramping) – DL power drift prevention (mitigation of power drift during SHO) – UL DPDCH/DPCCH setting • Inner loop power control – Fast power regulation towards a SIRtarget • Outer loop power control – Regulation of SIRtarget towards desired BLER

  4. Control Channel Power Setting • PCPICH_POWER = 6..43 dBm (default = 30.0) • For the common control channels below the power is relative the CPICH • MAX_FACH1_POWER = -35..15 dB, (1.8) • MAX_FACH2_POWER = -35..15 dB, (1.5) • BCH_POWER = -35..15 dB, (-3.1) • P_SCH_POWER = -35..15 dB, (-1.8) • S_SCH_POWER = -35..15 dB, (-3.5) • AICH_POWER = -35..15 dB, (-6.0) • PICH_POWER = -10..5 dB (-7.0) • PCH_POWER = -35..15 dB (-0.4)

  5. Power Control on Dedicated Channels • Radio Link Setup, RAB Establishment • Soft Handover, Power Balancing • Compressed Mode, Inter-Frequency Handover

  6. UL Power Control Overview

  7. Power Ramping on RACH The power of the first preamble is controlled by UL open loop PC, as well as the ramping step, the preamble threshold and “the number of retransmission attempts”

  8. Initial Power Setting on DL DPCCH/DPDCH • Initial DL DPDCH power at call setup • This is done in the RNC and the result is transferred to the RBS • The algorithm uses SF, measure Ec/I0 on PCPICH, transmitted power on PCPICH and the service requirements (SIRDPDCH_init) as input • PDL_DPDCH = PPCPICH + (SIRDPDCHinit - (Ec/ No)PCPICH) + Cbackoff -10log(SFDL_DPDCH/2) • Initial DL DPCCH power • PDL_DPCCH_TFCI = PDL_DPDCH + PO1 • PDL_DPCCH_TPC = PDL_DPDCH + PO2 • PDL_DPCCH_PILOT = PDL_DPDCH + PO3

  9. Uplink Power Control The initial uplink power in DPCCH is determined according to equation (8). This provides reliable setup of the radio link, while avoiding excessive power, which causes unnecessary interference

  10. Outer loop control SIRtarget SIRest TPC = up/down UL Inner Loop Power Control SIRest in RBS (on pilot) The UL inner loop power control should keep the estimated SIR of a radio link set at the SIRtarget TPC sent to UE UL inner power control algorithm controls simultaneously the power of the DPCCH and its associated DPDCH by increasing/decreasing the power in steps of 1 dB (the same adjustment for both DPCCH and DPDCH) according to SIRest >= SIRtarget  TPC = “down” SIRest < SIRtarget  TPC = “up”

  11. UL outer loop power control SIRtarget only within certain limits i.e. SIR_MIN ≤ SIRtarget ≤ SIR_MAX A jump regulator is choosing algorithm 0 i.e. ULOUTERLOOPREGULATOR=0 If CRC=OK then the SIRtarget is lowered by UL_SIR_STEP/UP_DOWN_RATIO If CRC=NG then the SIRtarget is increased by UL_SIR_STEP

  12. CRC = OK SIRtarget = 5.9 + 1[-1/(1x199) + 0/1] dB =5.895 dB Will continue to drop until another CRC = NG is detected SIRtarget = 4.9 + 1[-0/(1x199) + 1/1] dB =5.9 dB CRC = NG Jump Regulator Example SIRtarget ulInitSirTarget (speech = 4.9 dB) Transport block number

  13. SIRtarget = 5.8 dB Outer Loop updating of SIRtarget Jump regulator Result CRC NG => 5.900 dB SIRtarget = 4.9 dB SIRtarget = 5.9 dB CRC OK => 5.895 dB CRC OK => 5.890 dB CRC OK => 5.885 dB CRC OK => 5.880 dB CRC OK => 5.875 dB CRC OK => 5.870 dB CRC OK => 5.865 dB CRC OK => 5.860 dB Resolution of signaling is limited to 0.1 dB CRC OK => 5.855 dB CRC OK => 5.850 dB CRC OK => 5.845 dB CRC OK => 5.840 dB CRC OK => 5.835 dB CRC OK => 5.830 dB CRC OK => 5.825 dB CRC OK => 5.820 dB CRC OK => 5.815 dB Iub CRC OK => 5.810 dB RNC CRC OK => 5.805 dB RBS CRC OK => 5.800 dB

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