41389209-09-Power-Control-Rev-A-libre.pdf
Transcript of 41389209-09-Power-Control-Rev-A-libre.pdf
Power Control
Christofer LindheimerWRAN System Management
Commercial in confidence Power Control 2005-09-262
Outline
Why is Power Control important in WCDMA? How different channels are Power Controlled Power Control for Dedicated Channels in up- and
downlink– Open Loop Power Control / Initial Power Setting– Outer Loop Power Control– Inner Loop Power Control
Power Balancing in SHO
Commercial in confidence Power Control 2005-09-263
Why Power Control
Maintain quality of connection– Maintain acceptable quality throughout a coverage area – Avoid excessive quality
Limit transmitted power – Minimize interference in the system=maximizing capacity
Battery/Energy Consumption– UE and Battery backups
L1 >> L2 ⇒ PRX,2 >> PRX,1
PTX,2 PTX,1L2
PRX,2 L1
PRX,1if PTX,2 = PTX,1
PowerControl !
Commercial in confidence Power Control 2005-09-264
Outline
Why is Power Control important in WCDMA? How different channels are Power Controlled Power Control for Dedicated Channels in up- and
downlink– Open Loop Power Control / Initial Power Setting– Outer Loop Power Control– Inner Loop Power Control
Power Balancing in SHO
Commercial in confidence Power Control 2005-09-265
Mapping of transport channels to physical channels
Physical Channels Logical ChannelsTransport Channels
CCCHCommon Control Channel
DCCHDedicated Control Channel
PCCHPaging Control Channel
BCCHBroadcast Control Channel
DTCHDedicated Traffic Channel
PCH (DL)Paging Channel
FACH (DL)Forward Access Channel
BCH (DL)Broadcast Channel
RACH (UL)Random Access
Channel
DCH (DL/UL)Dedicated Channel
Common Transport Channels
PRACH (UL)Physical Random Access Channel
AICHAcquisition Indication Channel
P-CCPCH (DL)Primary Common Control Physical Channel
S-CCPCH (DL)Secondary Common Control Physical Channel
PICH (DL)Paging Indication Channel
DPDCH (UL/DL)Dedicated Physical Data Channel
DPCCH (UL/DL)Dedicated Physical Control Channel
DPCH - Dedicated Physical Channel
POWER CONTROL
Primary CPICH
Primary SCH
Secondary SCH
Commercial in confidence Power Control 2005-09-266
Power control ”type” dependent on channel type Common Channels - Fixed power
– P-CPICH, P-SCH, S-SCH, P-CCPCH (BCH), S-CCPCH (PCH, FACH), AICH, PICH
– Several UEs anywhere in the cell simultaneously use these channels Maintain quality throughout coverage area
– All (DL) common channels set relative to P-CPICH
Dedicated Channels – Dynamic Power control– One UE per DPCH channel– Optimize power for each individual link– All dedicated channels have an absolute-valued maximum
power (both in UL and DL)
Commercial in confidence Power Control 2005-09-267
Common Uplink Channel-PRACH Open Loop Power Control
-Hello!
-Hello!
-Hello!
• RACH preamble is sent with a stepwise increase in powerP_PRACH=L_PCPICH (@UE) + RTWP (UL @ RBS) + constantValueCprach (+ powerOffsetP0)
•Once detected, AICH in DL respond, (powerOffsetPpm added)
• Preamble power increases interrupted after maximum number of reattempts
Commercial in confidence Power Control 2005-09-268
Outline
Why is Power Control important in WCDMA? How different channels are Power Controlled Power Control for Dedicated Channels in up- and
downlink– Open Loop Power Control / Initial Power Setting– Outer Loop Power Control– Inner Loop Power Control
Power Balancing in SHO
Commercial in confidence Power Control 2005-09-269
Power Control of Dedicated Channels -Overview
CRC = Cyclic Redundancy Check
SIR = Signal to Interference Ratio
TPC = Transmit Power Commands
Initial Power Setting in UL and DL uses Open Loop . It ensures reliable connection setup, minimal impact on existing connections (UL) and avoids excessive power (DL).
RNC
P(Start value)
Open loop
P(SIR-Target,UL)
SIR-Target,UL
CRC-Error,UL
UL-Outer loop
The RNC and UE use Outer Loop power control to calculate UL and DL quality targets to which the UE and RNC shall adjust its transmitted power.
DL-Outer loop UE specific
P(SIR-Target, DL)
Inner loop
DL-TPCUL-TPC
The RBS and UE use Inner Loop to send UL and DL TPC’s(transmit power commands).
1500 Hz!
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Power Control of Dedicated Channels –Downlink, Initial Power Setting, Open Loop DL Initial Power dependent on
– CPICH Power primaryCpichPower
– Ec/No reported by UE Ec/No_PCPICH
– SIR Target dlInitSirTarget
– Spreading Factor SF_DL_DPDCH
– An offset to control initial output power level cBackOff
P_DL_DPDCH=primaryCpichPower + (dlInitSirTarget-Ec/No_PCPICH) + cBackOff + 10 log (2/SF_DL_DPDCH)
Commercial in confidence Power Control 2005-09-2611
Power Control of Dedicated Channels –Downlink, Inner Loop Power Control
DPDCH/DPCCH
Present slot power P(k) = P(k-1) + P TPC(k) dBm
PTPC(k) = + 0.5 dB for ‘UP’or – 0.5 dB for ‘down’
P(k-1) = Previous slot power
DPCCH: TPC Command = ‘Up or Down’
DPDCH
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Power Control of Dedicated Channels –Uplink initial power setting, Open Loop
UL Initial Power dependent on– CPICH Power
primaryCpichPower
– RTWP measured in RBS RTWP
– SIR Target (dependent on SF of DPDCH) ulInitSirTarget
– Spreading Factor SF_DPCCH
– An offset to control initial output power level cPO
– RSCP of PCPICH as measured in the UE
P_UL_DPCCH_INIT=primaryCpichPower + RTWP+ulInitSirtarget+ cPO - 10 log (SF_DPCCH) - RSCP_PCPICH
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Power Control of Dedicated Channels –Uplink, Outer Loop Power Control
Increases UL SIR target whenever a transport block is erroneously received and decreases the UL SIR target whenever a transport block is correctly received
SIR target adjustments äå BLER requirements
JUMP Algorithm
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Power Control of Dedicated Channels –Uplink, Inner Loop Power Control
RBS estimates the SIR of the pilot symbols (SIR_UL_RLS) and compares it to the SIR_TARGET.
If SIR_UL_RLS ≥SIR_TARGET ⇒ TPC Command =‘down’
If SIR_UL_RLS < SIR_TARGET ⇒ TPC Command =‘up’
DPDCH/DPCCH
TPC Command = ‘Up or Down’
DPCCH/DPDCH determined by gain-factors
Present slot power P(k) = P(k-1) + PTPC(k) dBm
Commercial in confidence Power Control 2005-09-2615
Outline
Why is Power Control important in WCDMA? How different channels are Power Controlled Power Control for Dedicated Channels in up- and
downlink– Open Loop Power Control / Initial Power Setting– Outer Loop Power Control– Inner Loop Power Control
Power Balancing in SHO
Commercial in confidence Power Control 2005-09-2616
Power Control of Dedicated Channels –Downlink, Power Control in SHO Initial Power Setting
– Aim to equalize the power transmission from different RBS’s (considering differences in PCPICH power and handover margin)
Up
TPC = Up TPC = Down
Node-B power drift is likely– Independent BER per link ⇒ different interpretations of received
TPC in different cells can occur
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Power Control of Dedicated Channels –Downlink, Power Balancing
Prevents different radio links involved in a connection from transmitting different DL power.
Preference
Power
Power adjustment
Time
Cell 1
Cell 2
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Power Control of Dedicated Channels –Uplink, Power Control in SHO
TPC = Up
TPC = Up & Down
TPC from cell to UE
One inner loop in respective Node-B One separate TPC from each cell in the active set
– All “increase” ⇒ increase UE power– ≥ 1 “decrease” ⇒ decrease UE power
TPC = Down
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Summary
Inner loop PC– Fast PC included in every timeslot– 1500 Hz– Measure the actual SIR & Compare with SIR-target– SIR ≥ SIR-target ⇒ Decrease power – SIR < SIR-target ⇒ Increase power
Outer loop PC– Adjust SIR-target based on BLER performance– Slower, per TTI basis updates– UL: Jump algorithm
Open loop PC– Initial power setting
In SHO: Power balancing (DL)
RNC
P(Start value)
Open loop
P(SIR-Target,UL)
SIR-Target,UL
CRC-Error,UL
UL-Outer loop
DL-Outer loop UE specific
P(SIR-Target, DL)
Inner loop
DL-TPCUL-TPC
1500 Hz!
Questions and Answers
Commercial in confidence Power Control 2005-09-2621