For internal use only!!!
LTE Power Control
Dariusz Tomeczko
Network Engineering
NWS NetEng GSM & LTE Migration
March 2012
For internal use only
1
© Nokia Siemens Netw orks
LTE Pow er Control/ Netw ork Engineering
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PUCCH
For internal use only
2
© Nokia Siemens Netw orks
LTE Pow er Control/ Netw ork Engineering
Introduction to Power Control in LTE
DOWNLINK
UPLINK
• Open Loop Power Control
• General rule: fixed PSD1), semi-static
UE Tx output power is basically
controlled with P0, alpha parameters
which determine target eNB Rx
sensitivity and path loss compensation
weight respectively.
Release: RL10/RL15TD onwards
eNB Tx power is fixed among available frequency resources.
Basic configuration is characterized by flat Power Spectral
Density – all subcarriers are transmitted with the same power;
total Tx power is maximum when all PRBs are scheduled
On top, PDCCH Power Control could be applied to distribute the
power between users to achieve higher number of UEs
satisfying PDCCH PC BLER target
Release: RL10/RL15TD onwards
• Closed Loop Power Control
Algorithm is improved with SINR/RSSI
matrix which is taken into account when
deciding about correction component for
PC equation.
Release: RL20/RL15TD onwards
•Control channel power boosting
Offsets determine power shifts for subcarriers which carry
PCFICH/PHICH or cell-specific Reference Signal. Offsets are
usually defined in relation to other OFDM symbols.
Release: RL30/RL25TD onwards
• PDSCH power boosting
If there is still Tx power availale and it is not needed for other
resources, it can be used to boost allocated PDSCH resources.
Release: RL60
1)
For internal use only
3
© Nokia Siemens Netw orks
This is not true for 2Tx antennas and MIMO_COMP=3dB
LTE Pow er Control/ Netw ork Engineering
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
4
© Nokia Siemens Netw orks
LTE Pow er Control/ Netw ork Engineering
UL Power Control – Principles
WCDMA vs. LTE
•General aim of power control is to find the balance between power needed
for the given transmission to achieve satisfactory performance of this
connection and level of interferences to other users.
• Simultaneously, battery consumption on the UE side needs to be addressed as
well
• In WCDMA UL is non-orthogonal and there is a strong need to cope with
intra-cell interferences
• This is not the case in LTE UL where the main source of interferences are
inter-cell interferences
For internal use only
5
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
UL Power Control – Principles
PSD vs. Tx Power
• Power control does not control the absolute UE Tx power but the Power
Spectral Density (PSD) for a device.
• The PSDs at the eNodeB from different users have to be close to each
other so the receiver does not work over a large range of powers.
• Primary means of controlling the bit rate in LTE is to adapt the MCS and
transmission bandwidth and not the Tx power
• Different data rates mean different Tx bandwidths so the absolute Tx
power of the UE will also change. PC makes that the PSD is constant
independently of the Tx bandwidth.
For internal use only
6
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
UL Power Control – Principles
Closed and Open Loop PC in LTE UL
• Pathloss and shadowing conditions are addressed by coarse power control
i.e. Open Loop Power Control
• Around the PSD operating point set by the Open Loop Power Control, fast
Closed Loop Power Control adjusts the power to fine tune the final power
settings used by the UE and to address e.g. fast fading effects
• However, there is no need to make the Closed Loop PC as fast as in WCDMA
Power per resource block = basic open-loop operating point + dynamic offset
UE controls the Tx power to keep
the transmitted power spectral
density (PSD) constant
independent of the allocated
transmit bandwidth (#PRBs)
If no feedback from eNodeB (in
the PDCCH UL PC command)
the UE performs open loop PC
based on path loss
measurements
Power Control is performed for each UE separately and
there is an independent Power Control for PUSCH and
PUCCH
For internal use only
7
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
If there is a feedback from
eNodeB the UE corrects the
PSD when receiving PC
commands from eNodeB (in
the PDCCH UL PC
command)
PC commands (up and
down) based on UL quality
and signal level
measurements
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
8
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
UL Power Control for PUSCH
PPUSCH (i) :PUSCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUSCH (i ) = min {PCMAX ,10 log10 ( M PUSCH (i )) + PO_PUSCH ( j ) +  ( j )  PL +  TF (i ) + f (i )} dBm
max.
allowed UE
power
number of
scheduled
RBs
For internal use only
9
© Nokia Siemens Netw orks
PUSCH
Operating
point
Pathloss
compensation
LTE Pow er Control/.Netw ork Engineering
Pathloss
MCS
dependent
factor
Outcome
of Closed
Loop PC
UL Power Control for PUSCH
PPUSCH (i) :PUSCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUSCH (i ) = min {PCMAX ,10 log 10 ( M PUSCH (i )) + PO_PUSCH ( j ) +  ( j )  PL +  TF (i ) + f (i )} dBm
max.
allowed UE
power
number of
scheduled
RBs
PUSCH
Operating
point
Pathloss
compensation
Pathloss
MCS
dependent
factor
Maximum allowed UE power (23 dBm for class 3)
For internal use only
10
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Outcome
of Closed
Loop PC
UL Power Control for PUSCH
PPUSCH (i) :PUSCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUSCH (i ) = min {PCMAX ,10 log 10 ( M PUSCH (i )) + PO_PUSCH ( j ) +  ( j )  PL +  TF (i ) + f (i )} dBm
max.
allowed UE
power
number of
scheduled
RBs
PUSCH
Operating
point
Pathloss
compensation
Pathloss
MCS
dependent
factor
Outcome
of Closed
Loop PC
Number of scheduled RBs (known from the scheduling grant)
(The UE Tx Power increases proportionally to # of PRBs)
For internal use only
11
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
UL Power Control for PUSCH
PPUSCH (i) :PUSCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUSCH (i ) = min {PCMAX ,10 log 10 ( M PUSCH (i )) + PO_PUSCH ( j ) +  ( j )  PL +  TF (i ) + f (i )} dBm
max.
allowed UE
power
number of
scheduled
RBs
PUSCH
Operating
point
Pathloss
compensation
Pathloss
MCS
dependent
factor
• PO_PUSCH(j) = PO_NOMINAL_PUSCH(j) + PO_UE_PUSCH(j)
• j = 0 -> PUSCH transmission with semi-persistent grant (not in RL30)
• j = 1 -> PUSCH transmission with dynamic scheduling
• j = 2 -> PUSCH transmission for random access
cell specific component
signalled from system
information for j = 0, 1
UE specific component
provided by higher
layers (RRC) for j = 0, 1
LNCEL:p0NomPusch
(Nominal power for UE
PUSCH TX power calculation)
LNCEL:p0UePusch (Power
offset for UE PUSCH TX power
calculation)
Range: -126...24 dBm, step 1
dBm
Default: -106 dBm ; GMC: -106
Range: -8...7 dB, step 1 dB
Default: 0 dB; GMC: 0
VENDOR PARAMETER (HIDDEN)
For internal use only
12
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Outcome
of Closed
Loop PC
Random access: j=2
PO_NOMINAL_PUSCH(2):
PO_PRE +  Preamble_Msg3
PO_UE_PUSCH(2) = 0
LNCEL: ulpcIniPrePwr (Preamble initial received
target power)
Range: 0 (-120 dBm), ... ,15 (-90 dBm), step 2 dBm
Default: 8 (-104 dBm); GMC: -104 dBm
LNCEL: deltaPreMsg3 (Delta preamble random
access message 3)
Range: -1 (-2 dB), ... 6 (12 dB), step 1 (2 dB)
Default: 1 (0 dB); GMC: 1
UL Power Control for PUSCH
PPUSCH (i) :PUSCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUSCH (i ) = min {PCMAX ,10 log 10 ( M PUSCH (i )) + PO_PUSCH ( j ) +  ( j )  PL +  TF (i ) + f (i )} dBm
max.
allowed UE
power
number of
scheduled
RBs
PUSCH
Operating
point
Pathloss
compensation
Pathloss
MCS
dependent
factor
Outcome
of Closed
Loop PC
pathloss [dB] = referenceSignalPower – higher layer filtered RSRP
RSRP calculation for
pathloss calculation is
done in accordance with
filter coefficient
LNCEL: filterCoeff (Filter coefficient)
Range: 0 (fc0), 1 (fc1), 2 (fc2), 3 (fc3), 4 (fc4), 5 (fc5), 6 (fc6), 7 (fc7), 8 (fc8), 9
(fc9), 10 (fc11), 11 (fc13), 12 (fc15), 13 (fc17), 14 (fc19)
Default: 4 (fc4); GMC: fc4
Path loss compensation factor is adjustable by O&M.
α is a cell – specific parameter
LNCEL: ulpcAlpha (Alpha)
Range: 0 (alpha 0), 1 (alpha 0.4), 2
(alpha 0.5), 3 (alpha 0.6), 4 (alpha 0.7), 5
(alpha 0.8), 6 (alpha 0.9), 7 (alpha 1)
Default: 7 (alpha 1); GMC: alpha 1
α  [0.0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]
No compensation
For internal use only
13
© Nokia Siemens Netw orks
Partial compensation
Pathloss is only partially compensated to
reduce inter-cell interferences
LTE Pow er Control/.Netw ork Engineering
Random access grant: j=2
 (2) = 1 (i.e. full PL compensation)
Full compensation (conventional
Power Control)
Pathloss is fully compensated
UL Power Control for PUSCH
PPUSCH (i) :PUSCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUSCH (i ) = min {PCMAX ,10 log 10 ( M PUSCH (i )) + PO_PUSCH ( j ) +  ( j )  PL +  TF (i ) + f (i )} dBm
max.
allowed UE
power
number of
scheduled
RBs
PUSCH
Operating
point
Pathloss
compensation
TF (i ) = 10 log10 (2 MPRK s − 1)
0
Pathloss
for K S = 1.25
otherwise
MCS
dependent
factor
Outcome
of Closed
Loop PC
LNCEL: deltaTfEnabled (Enabled TB size impact
to UE PUSCH power calculation)
Range: 0 (false), 1 (true)
Default: 0 (false); GMC: false
MPR = TBS/NRE with NRE: number of RE, TBS = Transport Block Size
•
•
•
Could be seen as dynamic offset of the TX power: when the BTS changes the MCS for the
UE then the UE indirectly may adapt the power
Increase the power if the Transport Format (MCS, TBS size, Number of Resource Blocks) it
is so selected to increase the number of bits per Resource Element
This recalculation could be disabled
For internal use only
14
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
15
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
UL Power Control for PUCCH
PPUCCH (i) :PUCCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUCCH (i ) = min{ PMAX , P0_PUCCH + PL + h(nCQI , nHARQ ) +  F_PUCCH ( F ) + g (i )} dBm
max.
allowed UE
power
PUCCH
operating
point
For internal use only
16
© Nokia Siemens Netw orks
Pathloss
PUCCH format
dependent part
LTE Pow er Control/.Netw ork Engineering
Compensation factor
for various PUCCH
formats
Outcome
of Closed
Loop PC
UL Power Control for PUCCH
PPUCCH (i) :PUCCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUCCH (i ) = min{ PMAX , P0_PUCCH + PL + h(nCQI , nHARQ ) +  F_PUCCH ( F ) + g (i )} dBm
max.
allowed UE
power
PUCCH
operating
point
Pathloss
PUCCH format
dependent part
Compensation factor
for various PUCCH
formats
Maximum allowed UE power (23 dBm for class 3)
For internal use only
17
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Outcome
of Closed
Loop PC
UL Power Control for PUCCH
PPUCCH (i) :PUCCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUCCH (i ) = min{ PMAX , P0_PUCCH + PL + h(nCQI , nHARQ ) +  F_PUCCH ( F ) + g (i )} dBm
max.
allowed UE
power
PUCCH
operating
point
Pathloss
PUCCH format
dependent part
Compensation factor
for various PUCCH
formats
Outcome
of Closed
Loop PC
• PO_PUCCH = PO_NOMINAL_PUCCH + PO_UE_PUCCH
cell specific component
signalled from system
information
UE specific component
provided by higher layers
LNCEL:p0NomPucch (Nominal power
for UE PUCCH TX power calculation)
LNCEL:p0UePucch (Power offset for
UE PUCCH TX power calculation)
Range: -127...-96 dBm, step 1 dBm
Default: -100 dBm ; GMC: -100
For internal use only
18
© Nokia Siemens Netw orks
Range: -8...7 dB, step 1 dB
Default: 0 dB; GMC: 0
VENDOR PARAMETER (HIDDEN)
LTE Pow er Control/.Netw ork Engineering
UL Power Control for PUCCH
PPUCCH (i) :PUCCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUCCH (i ) = min{ PMAX , P0_PUCCH + PL + h(nCQI , nHARQ ) +  F_PUCCH ( F ) + g (i )} dBm
max.
allowed UE
power
PUCCH
operating
point
Pathloss
PUCCH format
dependent part
Compensation factor
for various PUCCH
formats
Always full pathloss compensation (α = 1)
For internal use only
19
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Outcome
of Closed
Loop PC
UL Power Control for PUCCH
PPUCCH (i) :PUCCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUCCH (i ) = min{ PMAX , P0_PUCCH + PL + h(nCQI , nHARQ ) +  F_PUCCH ( F ) + g (i )} dBm
max.
allowed UE
power
•
PUCCH
operating
point
Pathloss
For PUCCH format 2, 2a, 2b
and normal cyclic prefix
For PUCCH format 2 and
extended cyclic prefix h n
For internal use only
20
© Nokia Siemens Netw orks
Outcome
of Closed
Loop PC
Compensation factor
for various PUCCH
formats
(
)
h nCQI , n HARQ = 0
For PUCCH format 1,1a and 1b
•
•
PUCCH format
dependent part
(
h nCQI , n HARQ
( CQI , n HARQ )
)

 nCQI
10 log10 
=
 4
0


 if nCQI  4


otherwise

 nCQI + n HARQ 
 if nCQI + n HARQ  4
10 log10 

=
4


0
otherwise

LTE Pow er Control/.Netw ork Engineering
n: number of information bits
UL Power Control for PUCCH
PPUCCH (i) :PUCCH Power in subframe i
Open Loop (OL)
Closed Loop (CL)
PPUCCH (i ) = min{ PMAX , P0_PUCCH + PL + h(nCQI , nHARQ ) +  F_PUCCH ( F ) + g (i )} dBm
max.
allowed UE
power
PUCCH
operating
point
Name
Pathloss
PUCCH format
dependent part
Compensation factor
for various PUCCH
formats
Outcome
of Closed
Loop PC
Abbreviation
Range
Description
Default
dFListPucch
n/a
SEQUENCE (see below)
n/a
DeltaF PUCCH Format 1
dFpucchF1
0 (-2 dB), 1 (0 dB), 2 (2 dB)
UL power offset for
PUCCH format 1
1 (0 dB)
0
DeltaF PUCCH Format 1b
dFpucchF1b
0 (1 dB), 1 (3 dB), 2 (5 dB)
UL power offset for
PUCCH format 1b
0 (1 dB)
1
DeltaF PUCCH Format 2
dFpucchF2
0 (-2 dB) , 1 (0 dB), 2 (1
dB), 3 (2 dB)
UL power offset for
PUCCH format 2
1 (0 dB)
0
DeltaF PUCCH Format 2a
dFpucchF2a
0 (-2 dB), 1 (0 dB), 2 (2 dB)
UL power offset for
PUCCH format 2a
1 (0 dB)
0
DeltaF PUCCH Format 2b
dFpucchF2b
0 (-2 dB), 1 (0 dB), 2 (2 dB)
UL power offset for
PUCCH format 2b
1 (0 dB)
0
LNCEL:DeltaF PUCCH list
For internal use only
21
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
GMC
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
22
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
UL Power Control for SRS
Open Loop (OL)
Closed Loop (CL)
PSRS (i ) = min{PCMAX , PSRS_OFFSET + 10 log10 ( M SRS ) + PO_PUSCH ( j ) +  ( j )  PL + f (i )}
max.
allowed UE
power
Offset
BW for
SRS
PUSCH
Operating
point
Pathloss
compensation
Pathloss
LNCEL: srsPwrOffset (Power offset for SRS transmission power calculation)
Range: 0..15, step 1
Default: 7; GMC: 7
Note: For deltaTfEnabled = 'true' (-> KS = 1.25) the actual parameter value is "srsPwrOffset-3"
corresponding to the dB-range of -3 dB to 12 dB in steps of 1 dB. For deltaTfEnabled = 'false' (-> KS = 0)
the actual parameter value is "-10.5 + 1.5 * srsPwrOffset" value corresponding to the dB-range -10.5 dB to
12 dB in steps of 1.5 dB
For internal use only
23
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Outcome
of Closed
Loop PC
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
24
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Performance of Open Loop UL Power Control
Influence of alpha and P0 on mean cell throughput and
instantaneous user throughput:
Results from: Navin Hathiramani, Lorena Serna, LTE Optimization Guidelines
For internal use only
25
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Performance of Open Loop UL Power Control
Influence of alpha and P0 on perceived UE throughput:
Results from: Navin Hathiramani, Lorena Serna, LTE Optimization Guidelines
For internal use only
26
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
27
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
Sequence of steps that is followed once Closed Loop UL
Power Control is enabled
LNCEL:ulpcEnable (Enable closed loop uplink
power control)
Range: 0 (false), 1 (true)
Default: 0 (false); GMC: true
Clipping
Weighting
Long-term
filtering/averaging
Decision matrix
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
28
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
Clipping
Weighting
Long-term
filtering/averaging
Decision matrix
Average received RSSI per UE per TTI is calculated
separately for:
- PUSCH/PUCCH/SRS
for all PRBs allocated to the UE
Average received SINR per UE per TTI is calculated
separately for:
- PUSCH/PUCCH/SRS for all PRBs allocated to the
UE
- PUSCH/PUCCH for all PRBs that possibly could be
allocated to the UE for this channel
It is possible to exclude PUSCH/PUCCH from the
calculation process
LNCEL:ulpcPuschEn (Include PUSCH
measurements in CL power control)
LNCEL:ulpcPucchEn (Include PUCCH
measurements in CL power control)
Range: 0 (false), 1 (true)
Default: 1 (true); GMC: true
Range: 0 (false), 1 (true)
Default: 1 (true); GMC: true
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
29
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
All UE/TF specific factors are subtracted i.e.:
•  TF
•  PF_PUCCH
• h(n)
• PO_UE_PUSCH
Clipping
Weighting
Long-term
filtering/averaging
• PO_UE_PUCCH
from corresponding RSSI/SINR values on TTI
basis to:
-reduce the number of PC windows for different
transport formats to one, hence transport format
independent processing of the quality and level
measurements shall be applied,
-normalize a UE specific power offset
Decision matrix
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
30
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
Clipping process is applied in the following way:
Averaged received level per TTI per UE:
RSSI *** := min(max(RSSI min,RSSI***)RSSImax)
*** PUSCH/UE,
Clipping
PUCCH/UE,
SRS/UE
LNBTS: ulpcRssiMax (Upper limit for RSSI value in CL power control)
Range: -127 dBm, .., 0 dB, step 1 Default: 0 dBm; GMC: 0 VENDOR SPECIFIC
LNBTS: ulpcRssiMin (Lower limit for RSSI value in CL power control)
Range: -127 dBm, .., 0 dB, step 1 Default: -127 dBm; GMC: -127 VENDOR SPECIFIC
Weighting
Averaged received SINR per TTI per UE:
Long-term
filtering/averaging
SINR*** := min(max(SINRmin,SINR***)SINRmax)
*** PUSCH/UE, PUSCH/cell, PUCCH/UE, PUCCH/cell, SRS/cell
LNBTS: ulpcSinrMax (Upper limit for SINRvalue in CL power control)
Range: -47 dB, .., 80 dB, step 1 Default: 40 dB; GMC: 40 VENDOR SPECIFIC
Decision matrix
LNBTS: ulpcSinrMin (Lower limit for SINR value in CL power control)
Range: -47 dB, .., 80 dB, step 1 Default: -40 dB; GMC: -40 VENDOR SPECIFIC
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
31
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Composite SINR and RSSI for PUCCH and PUSCH are
calculated
PUSCH and SRS - composite SINR and RSSI:
Transformation into
independent format
C _ SINRPUSCH / SRS =
SINRPUSCH / UE  WF _ PUSCH _ UE + SINRPUSCH / cell  WF _ PUSCH _ CELL + SINRSRS / cell  WF _ SRS _ CELL
WF _ PUSCH _ UE + WF _ PUSCH _ CELL + WF _ SRS _ CELL
C _ RSSI PUSCH / SRS =
Clipping
RSSI PUSCH / UE  WF _ PUSCH _ UE + RSSI SRS / UE  WF _ SRS _ UE
WF _ PUSCH _ UE + WF _ SRS _ UE
LNBTS: ulpcWfPuschUe (Weighting factor for UE scope measurements on PUSCH)
Range: 1, .., 100, step 1 Default: 1; GMC: 1 VENDOR SPECIFIC
LNBTS: ulpcWfPuschcell (Weighting factor for cell scope measurements on PUSCH)
Range: 1, .., 100, step 1 Default: 1; GMC: 1 VENDOR SPECIFIC
Weighting
PUCCH - composite SINR and RSSI:
Long-term
filtering/averaging
C _ SINRPUCCH =
SINRPUCCH / UE  WF _ PUCCH _ UE + SINRPUCCH / cell  WF _ PUCCH _ CELL
WF _ PUCCH _ UE + WF _ PUCCH _ CELL
C _ RSSI PUCCH = RSSI PUCCH / UE
LNBTS: ulpcWfPucchUe (Weighting factor for UE scope measurements on PUCCH)
Decision matrix
Range: 1, .., 100, step 1 Default: 1; GMC: 1 VENDOR SPECIFIC
LNBTS: ulpcWfPucchcell (Weighting factor for cell scope measurements on PUCCH)
Range: 1, .., 100, step 1 Default: 1; GMC: 1 VENDOR SPECIFIC
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
32
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
The results are filtered via low pass filter first order
(exponential moving average):
y (n) = c  y (n − 1) + (1 − c)  x(n)
x: input (modulation independent, composite RSSI, SINR), per TTI
y: output (filtered RSSI, SINR), over several TTIs
c: filter coefficient defined by averaging constant and time interval of input values
c = exp(-T/T avg ) i.e. impact = (1/e) at t = -T avg
Clipping
Example: T = TTI = 1ms, T avg = 25 ms → c = 0.96
LNCEL: ulpcReadPeriod (Time interval for power command decisions)
Range: 10..2000 ms, step 10 ms
Default: 50 ms; GMC: 50
Weighting
Separate averaging time values are used if UL data is available:
Long-term
filtering/averaging
LNBTS: ulpcCchavgtcont (Averaging time for continuous PUCCH measurements)
Range: 0.2, .., 100 ms, step 0.1 ms Default: 20 ms; GMC: 200 VENDOR SPECIFIC
LNBTS: ulpcSchavgtcont (Averaging time for continuous PUSCH measurements)
Range: 0.2, .., 100 ms, step 0.1 ms Default: 20 ms; GMC: 200 VENDOR SPECIFIC
Decision matrix
and if UL data is not available:
LNBTS: ulpcCchavgtdisc (Averaging time for discontinuous PUCCH measurements)
Range: 0.2, .., 100 ms, step 0.1 ms Default: 50 ms; GMC: 500 VENDOR SPECIFIC
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
33
© Nokia Siemens Netw orks
LNBTS: ulpcSchavgtdisc (Averaging time for discontinuous PUSCH measurements)
Range: 0.2, .., 100 ms, step 0.1 ms Default: 50 ms; GMC: 500 VENDOR SPECIFIC
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
LNCEL: ulpcUpqualSch (Upper
SINR threshold for PUSCH power
command decision)
Range: -47..80 dB, step 1 dB
Default: 11 dB; GMC: 20
Choice between {-1; 0; +1; +3 dB} is done
via comparing outputs of the filter with the
twodimensional decision matrix
LNCEL: ulpcUpqualCch (Upper
SINR threshold for PUCCH power
command decision)
Range: -47..80 dB, step 1 dB
Default: 4 dB; GMC: 4
Decision matrix
SINR
+ 1 dB or
+ 3 dB
Weighting
Long-term
filtering/averaging
Decision matrix
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
34
© Nokia Siemens Netw orks
1
UP_QUAL_**
Clipping
LNCEL:ulpcLowqualSch (Lower
SINR threshold for PUSCH power
LOW_QUAL_**
command decision)
Range: -47..80 dB, step 1 dB
Default: 8 dB; GMC: 18
LNCEL:ulpcLowqualCch (Lower
SINR threshold for PUCCH power
command decision)
Range: -47..80 dB, step 1 dB
Default: 1 dB; GMC: 1
- 1 dB
+ 1 dB or
+ 3 dB
- 1 dB
2
0 dB
4
+ 1 dB or
+ 3 dB
-1 dB
5
+ 1 dB or
+ 3 dB
7
LOW_LEV_**
6
+ 1 dB or
+ 3 dB
8
UP_LEV_**
LNCEL: ulpcLowlevCch (Lower
RSSI threshold for PUCCH
power command decision)
LNCEL: ulpcUplevCch (Upper
RSSI threshold for PUCCH
power command decision)
Range: -127..0 dBm, step 1 dBm
Default: -103 dBm; GMC: -103
Range: -127..0 dBm, step 1 dBm
Default: -98 dBm; GMC: -98
LNCEL: ulpcLowlevSch (Lower
RSSI threshold for PUSCH
power command decision)
LNCEL: ulpcUplevSch (Upper
RSSI threshold for PUSCH
power command decision)
Range: -127..0 dBm, step 1 dBm
Default: -103 dBm; GMC: -103
Range: -127..0 dBm, step 1 dBm
Default: -98 dBm; GMC: -98
LTE Pow er Control/.Netw ork Engineering
3
9
RSSI
Closed Loop UL Power Control
Calculation of RSSI and
SINR on UE basis
Transformation into
independent format
Range: 0 (false), 1 (true) Default: true; GMC: true
VENDOR SPECIFIC, VALUE FALSE NOT
SUPPORTED
In the current implementation power control commands are sent:
• for PUSCH - with the help of the UL scheduling grant for the PUSCH,
i.e. whenever an UE is scheduled, it will get a TPC command
together with being informed which resources and transport format is
assigned.
•
for PUCCH if DL has been assigned, format 1 is used
•
Clipping
LNBTS: ulpcAccuEnable (PUSCH TPC
commands accumulation enabled)
if there is no DL grant, TPC commands are not scheduled for these UEs
(leading to use of open loop PC only)
f(i) = f(i-1) + d PUSCH (i - KPUSCH)
i.e. recursive determination
where d PUSCH is the signalled TPC in subframe i-KPUSCH
For FDD: KPUSCH = 4
Weighting
Long-term
filtering/averaging
The option of sending absolute values is not supported.
The accumulated DELTA PUCCH and DELTA PUSCH values are
constantly monitored. Maximum/minimum cumulated DELTA
PUCCH/PUSCH values could not be exceeded.
LNBTS: ulpcCumpucchmax (Maximum cumulative delta PUCCH)
Range: -127 dB, .., 127 dB, step 1 Default: 127 dB; GMC: 127 VENDOR SPECIFIC
LNBTS: ulpcCumpucchmin (Minimum cumulative delta PUCCH)
Decision matrix
Range: -127 dB, .., -127 dB, step 1 Default: -127 dB; GMC: -127 VENDOR SPECIFIC
LNBTS: ulpcCumpuschmax (Maximum cumulative delta PUSCH)
Range: -127 dB, .., 127 dB, step 1 Default: 127 dB; GMC: 127 VENDOR SPECIFIC
Commanding
PUCCH/PUSCH delta
values to the UE
For internal use only
35
© Nokia Siemens Netw orks
LNBTS: ulpcCumpuschmin (Minimum cumulative delta PUSCH)
Range: -127 dB, .., -127 dB, step 1 Default: -127 dB; GMC: -127 VENDOR SPECIFIC
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Broadcast of P0_NOMINAL_PUSCH, P0_NOMINAL_PUCCH, ALPHA, Pmax,
eNodeB deltaFListPUCCH and deltaPreambleMsg3. UE specific parameters
P0_UE_PUSCH, P0_UE_PUCCH, DELTA_TF_ENABLED, ACCUMULATION
ENABLED, P_SRS_OFFSET and filterCoefficient signaled via RRC-DCCH
Transmit power derived from open loop PC
UE
open loop PC
DELTA_PUSCH and DELTA_PUCCH via PDCCH, MPUSCH from the scheduling grant
Data using transmit power derived from open and closed loop
closed loop PC
DELTA_PUSCH and DELTA_PUCCH via PDCCH, MPUSCH from the scheduling grant
period of no UL data transfer (DRX)
resuming UL data transfer
smooth transition
towards open
loop PC
UL data transfer using transmit power derived from open loop
component
DELTA_PUSCH and DELTA_PUCCH via PDCCH, MPUSCH from the scheduling grant
closed loop PC
Data using transmit power derived from open and closed loop
For internal use only
36
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Common Power Control Info in SIB2 (1/2)
For internal use only
37
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Common Power Control Info in SIB2 (2/2)
For internal use only
38
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Common Power Control Info in RRC Connection Reconfiguration message (1/3)
For internal use only
39
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Common Power Control Info in RRC Connection Reconfiguration message (2/3)
For internal use only
40
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Common Power Control Info in RRC Connection Reconfiguration message (3/3)
For internal use only
41
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Dedicated Power Control Info (1/3)
see next slide
For internal use only
42
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Dedicated Power Control Info (2/3)
For internal use only
43
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Closed Loop UL Power Control
Dedicated Power Control Info (3/3)
For internal use only
44
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PUCCH
For internal use only
45
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
ToC
Influence of CL PC settings on UL LTE throughput
Low level: -93 & High level: -88
Low qual: 18 & High qual: 20
Best peak tput
achieved in bad
conditions when target
levels are set high.
For high loaded networks,
lower target levels could
be set to reduce
interference levels.
Low level: -101 & High level:-96
Low qual: 8 & High qual: 10
Lower target levels reduce UE tx
power leading to higher BLER/lower
MCS/lower tput even in good
conditions. But if every UE in the area
reduce their TX power than overall
interference is reduced and tput will
improve. That is the main reason of
fractional path loss(alpha): Improve
the cell edge performance rather than
improving the cell capacity
CLPC OFF
Worst tput in bad
conditions when CLPC
control is off
Slide from: Shomik Pathak, RRM Algorithms in TTI Traces and related System Performance
For internal use only
46
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Influence of CL PC settings on UL LTE throughput
30000
25
20
25000
20000
10
15000
5
0
10000
-5
5000
-10
0
-15
<-110 -110-- -108-- -106-- -104-- -102-- -100-- -98-- -96-- -94-- -90-- -88-- -84-- -82-- -80-- -78-- -74-- -72-- -70-- -68-- -66-108 106 104 102 100
98
96
94
92
88
86
82
80
78
76
72
70
68
66
64
RSRP dBm
test
Data
CL PC set2 - Average of Average of MAC Uplink Throughput
CL PC set2 - Average of Average of UE TX
CL PC set1 - Average of Average of MAC Uplink Throughput
CL PC set1 - Average of Average of UE TX
Average of RSRP
CL set 1: ulpcUpqualSch = 11, ulpcLowqualSch = 8 (DEFAULT values)
CL set 2: ulpcUpqualSch = 17, ulpcLowqualSch = 14
Results from: Navin Hathiramani, Lorena Serna, LTE Optimization Guidelines
For internal use only
47
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Tx Pwr dBm
Throughput kbps
15
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PUCCH
For internal use only
48
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
DL power settings
Example with 2x2 MIMO
Type B symbol
• The general rule is to keep flat Power Spectral Density in
downlink
• However, there are several exceptions to this rule
• Two types of OFDM symbols
(OFDM symbol = complete set of orthogonal subcarriers as
an output of FFT operation) could be distinguished
• Symbol A does not carry the cell-specific Reference Signal
• Symbol B carries the cell-specific Reference Signal
pMax – dlCellPwrRed – dlpcMimoComp – 10log10(#PRBsx12)
Type A symbol
pMax – dlCellPwrRed – dlpcMimoComp + 10log10(P_B) – 10log10(#PRBsx12)
depends on antenna configuration and dlRsBoost, set by the system to achieve the maximum RF
power in such a way that sum power of OFDM symbol does not exceed the committed average power
index
LNCEL: dlpcMimoComp (MIMO power
compensation)
Range: 0..10 dB, step 0.01 dB
Default: 0 dB; GMC: 0
pMax – dlCellPwrRed + dlRsBoost – 10log10(#PRBsx12)
LNCEL: pMax (Maximum output power)
Range: 0 (10.0 dBm), 1 (37.0), 2 (39.0), 3 (40.0),
4For(41.8),
5 (43.0), 6 (44.8), 7 (46.0), 8 (47.8)
internal use only
Default:
GMC:
49
© Nokia
Siemens-;Netw
orks39.0
LNCEL: dlCellPwrRed (Cell power reduce)
Range: 0..20 dB, step 0.1 dB
Default: 0 dB; GMC: 0
LTE Pow er Control/.Netw ork Engineering
LNCEL: dlRsBoost (Downlink reference
signals transmission power boost)
Range: 0 (0dB), 1 (1.77dB), 2 (3dB), 3
(4.77dB), 4 (6dB)
Default: 0 dB; GMC: 0dB
DL power settings
•
Advantages of RS power boost:
• Better channel estimation
• RS is used for coherent demodulation as the information about channel response. Its wrong
reception may cause demodulation errors and finally throughput degradation
• RS boost improves decoding of cell under higher interference conditions and may also improve
handover performance
• It is recommended to use dlRsBoost to boost the RS instead of dlpcMimoComp since
dlpcMimoComp affects all PDSCH REs (3 dB less power)
• It is also possible to boost the Tx power of:
• PCFICH channel to improve detection of PCFICH
• PCFICH informs about the number of PDCCH symbols per subframe; in case it is not properly
received, the whole subframe is lost causing user throughput degradation
• To be applied in special cases
• PHICH channel to assure higher reliability of PHICH
• PHICH carries ACK/NACK messages in response to uplink transmission; in case there are too
many misdetections (ACK→NACK), PUSCH will be unnecessary loaded with
retransmissions causing capacity degradation and additional UE power consumption
• However, usually PHICH is not the limit link as far as LiBu is concerned
LNCEL: dlPcfichBoost (Downlink PCFICH
transmission power boost)
LNCEL: dlPhichBoost (Downlink PHICH
transmission power boost)
Range: 0..6 dB, step 0.1 dB
Default: 0 dB; GMC: 0
Range: 0..6 dB, step 0.1 dB
Default: 0 dB; GMC: 0
For internal use only
50
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
DL power settings
• To maintain RF power, PCFICH/PHICH channel boost is performed at the cost of
PDCCH power.
• However, the power de-boosting of PDCCH may be reduced to keep the 1% BLER target for PDCCH.
• Negative power boost for RS/PCFICH/PHICH could not be applied
• Boosts are applied in the following order:
• RS > PCFICH > PHICH
so if the power is not enough, PHICH boost is reduced firstly, then PCFICH – if needed.
• If RS/PCFICH/PHICH boost, CQI as reported by the UE should be adjusted by the
system (reported value may be too optimistic)
• Moreover, it is also possible to reuse the power of non-allocated REs around
PSS/SSS to boost the power of synch signals by 10log10(72/62) (via vendor
specific parameter).
LNBTS: dlSynchBoost (Downlink synch signal
transmission power boost)
– No influence on PDCCH power basket.
Range: 0 (false), 1 (true)
Default: false; GMC: false
VENDOR SPECIFIC, HIDDEN
For internal use only
51
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
LTE Power Control
Contents
▪ Introduction to LTE Power Control
▪ UL Power Control
▪ Principles
▪ UL open loop PC part
▪ PUSCH
▪ PUCCH
▪ SRS
▪ Performance
▪ UL closed loop PC part
▪ Algorithm
▪ Performance
▪ DL Power Control
▪ Settings
▪ DL Power Control for PDCCH
For internal use only
52
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
DL Power Control for PDCCH
• DL Power Control for PDCCH is an additional mechanism interacting with
DL AMC for PDCCH in order to make the signaling as robust as possible
(and in turn improve KPIs like HO sucess ratio, CSSR, throughput etc.)
• DL-PC-CCH aims at 1% target BLER but cannot modify aggregation level
assignments
• Required SNR or CQI to satisfy the 1% is known from the
rdPdcchAggTables.
• Main actions performed by DL-PC-CCH:
– Power reduction on CCEs with assigned AGG level higher than required
▪ the aggregation level could be (much) higher than required (in case of AGG1) or only slightly higher
than required to achieve 1% BLER (AGG2, AGG4, AGG8)
– Power boosting on CCEs with assigned AGG level lower than required
▪ Those are the UEs with AGG-8 and AGG-4, where this has been done automatically during the
PDCCH scheduling process according to enableLowAgg (to save PDCCH resources) and also all
other UEs where a lower Aggregation than required has been assigned during PDCCH scheduling
to avoid PDCCH blocking.
– Equal power relocation among all scheduled CCEs
LNCEL: enableLowAgg (Enable lower aggregation selection for PDCCH LA)
For internal use only
53
© Nokia Siemens Netw orks
Range: 0 (false), 1 (true)
Default: 0; GMC: true
LTE Pow er Control/.Netw ork Engineering
DL Power Control for PDCCH
1,00
0,90
0,80
AGG-1
0,70
AGG-2
0,50
0,40
0,30
AGG-8
AGG-4
CDF
0,60
0,20
0,10
0,00
-26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0
~20% AGG-1
~32% AGG-2
~25% AGG-4
~23% AGG-8
(SINR>11dB)
(4<SINR<11dB)
(0<SINR<4dB)
(SINR<0dB)
~10% UEs will not meet the 1%
BLER target for PDCCH and need
additional improvement (power
boosting).
Average AGG level = 3.68
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30
SNIR [dB]
For internal use only
54
© Nokia Siemens Netw orks
The SINR CDF at full load would
lead to the following AGG
utilization:
LTE Pow er Control/.Netw ork Engineering
DL Power Control for PDCCH
• PDCCH Power Control can be enabled/disabled by O&M switch
• Maximum transmit power of the Power Amplifier cannot be exceeded (pMax; O&M)
• Reduction, boosting and relocation range is strictly defined and is always considered as the
limit for power level modification
• DL-PC-CCH operates together with DL-AMC-CCH on TTI basis
• DCI messages with more than one CCE (AGG-…>1) have a flat PSD,
thus all CCEs belonging to one scheduled UE are transmitted with the same power
Name
Abbreviation
Range
Enable PDCCH
power control
LNCEL:enablePcPdcch
PDCCH PC
maximum power
boost
Default
GMC
true, false
true
true
LNBTS:pdcchPcBoost
HIDDEN, VENDOR SPECIFIC
0...10 dB, step 0.1 dB
4 dB
40
PDCCH PC
maximum power
reduction
LNBTS:PdcchPcRed
HIDDEN, VENDOR SPECIFIC
0...10 dB, step 0.1 dB
6 dB
60
PDCCH PC
maximum power
relocation
LNBTS:pdcchPcReloc
HIDDEN, VENDOR SPECIFIC
0...10 dB, step 0.1 dB
3 dB
30
For internal use only
55
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
Description
DL Power Control for PDCCH – PDCCH power
reduction
Power reduction is high during
high PdcchCQI, since Cqi is
higher than or equal to what is
required for 1% target BLER
Power reduction is nonexistent during low
PdcchCQI, since it
requires all available
power to maintain < 1%
target BLER
Slide from: Shomik Pathak, RRM Algorithms in TTI Traces and related System Performance
For internal use only
56
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
ToC
ToC
Thanks for your attention
For internal use only
57
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering
ToC
References
Shomik Pathak, RRM Algorithms in TTI Traces and related System Performance
Navin Hathiramani, Lorena Serna, LTE Optimization Guidelines
RRM SFS RL30
CFAM LTE430 feature
RA4121 RL20 Power Control training materials
RA4121 RL20 UL/DL Scheduler training materials
Piotr Godziewski, NEI RL30 DL Power Boosting for control channels
For internal use only
58
© Nokia Siemens Netw orks
LTE Pow er Control/.Netw ork Engineering