6.power control
TRANSCRIPT
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OMF010003 Power Control
ISSUE1.4
Wireless Training Department
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Power control overview
HWpower control
HWpower control
Course Contents
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Power Control Overview
Power control
Adjust the transmitting power of BTS and MS when needed.
Based on measurement reports of BTS and MS
Purpose
Save the power of BTS and MS;
Reduce the interference of the network;
Increase the quality of the network.
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Power Control Overview
Power control includes uplink power control and downlink
power control, Which are performed independently
Uplink power control: Adjust TX power of MS to let BTS receive
stable signal, reduce the uplink co-channel and adjacent
channel interference, reduce power consumption of MS.
Downlink power control: Adjust BTS TX power to let MS receive
stable signal, reduce the downlink co-channel and adjacent
channel interference, reduce power consumption of BTS.
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Power Control Overview
Process of power control commands
It takes 3 measurement report periods(480ms/period) from
command sending to execution.
SA SA1A SAA1A1 SA2A2A2 SA3A3A3
BTS sends the command for power
control and TA in SACCH header.
MS obtains SACCH
block
MS begins to send the
measurement report of the
last multi-frame.
In the 26 multi-frames,frame 12 sends
SACCH.
BTS receives the
measurement report
SACCCH report period:
26X4=104 frames (480ms)
MS adopts the newpower level and TA
MS begins to set up a new SACCH header
to report the new TA and power control
message.
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Power Control Overview
Huawei power control algorithm: HW I and HW II power control
Measurement reportpre-processing
Power control algorithm
selection
Yes
HW I power control
algorithm
HW II power control
algorithm
GSM0508 power control
algorithm
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Power Control Overview
Power control judgment and the selection of HWI algorithm or
HWII algorithm
Power control algorithm selected in power control data table
Power control judgment is controlled by BTS measurementreport pre-processing item which can be selected in handover
control data table
MR. Pre-process (measurement report pre-processing): This
switch decide where power control be processed. Ifmeasurement report pre-processing is yes, power control is
processed in BTS, and when setting it no, power control is
processed in BSC.
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Power control overview
HWpower control
HWpower control
Course Contents
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HW I Power Control
HW I power control
Process of HW I power control
MR pre-processing
Data configuration for HW I power control comparison of uplink power control with downlink power control
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Process of HW I power control
Measurement report
pre-processing
Aim achieved ?
Power control calculation and
adjustment
N
Y
HW I Power Control
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Original data of power control -- measurement report
Network
Downlinkmeasurement
report
Uplink MR
BTS
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Uplink
measurementreport
Downlink
measurement
report
HW I Power Control
Measurement report
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Measurement report pre-processing -- interpolation
Each measurement report has a serial number. When the serial
numbers are discontinuous, this indicates that some
measurement reports must be missed. In this case, the network
will fill up the measurement report according to interpolation
algorithm.
MR MRMRMR MR
Measurement report
serial number n
Measurement report
serial number n+4
Consecutive measurement report flow
3 missing measurement reports
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Measurement report pre-processing -- filtering
Calculate average results of several consecutive measurement
reports to obtain the current information, reduce the influence of
some abnormal measurement reports for the judgment of power
control.
MRMR MRMR
MR MR
Consecutive measurement report flow
Filter
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[BTS power control table]
HW I power control data configuration and parameter
introduction
Parametername
Meaning Valuerange
Recommended value
DL RX_LEVExpected
The expected signal level of MS in stable status, Expected
stable downlink signal level > downlink edge HO threshold
Otherwise, ping-pang HO will be caused.
063 35
DL RX_LEVCompensation
The power adjustment value varies with this parameter. Theadjustment value caused by power level equal to the differencebetween the expected signal level and the actual receivingsignal level multiply this factor.
0100 80(signal ex-signalrx)*80%=adjust
ment value
DL Qual.Expected
Expected signal quality of MS in stable status. 0 7
Levels
1
DLQual.Compensation
The power adjustment value varies with this parameter. Theadjustment value caused by signal quality equal to10*difference between the expected signal quality level and theactual receiving signal quality level multiply this factor.
0100 20[10*(qualityRX-qualityEX)*20%]
MAX PCStep
maximum adjustment range in one BTS power controlcommand
Levels0~16,2dB eachstep
8
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HW I Power Control
[BTS power control table]
Parametername
Meaning Valuerange
Recommended value
BTS PCPeriod
Time interval for implementing two power control commands(unit count of SACCH period)
110 5
Filter lengthfor DL
RX_LEV
Content: indicating the number of measurement reports inwhich the average of uplink signal strength is taken before MS
power adjustment at stable stage. The purpose is to removethe influence of some abnormal reports. When the filter lengthis too long, the influence due to abnormal reports will beweakened, but the MS power adjustment is not timely.
132 5
BTS Minpower
Indicating the minimum transmitting power value supported bythe BTS
0~36 4
BTS Maxpower
Indicating the maximum transmitting power value supportedby the BTS.
0~56 According toBTS type
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[MS power control data table]Parameter
nameMeaning Value range Recom-
mendedvalue
initialRX_LEVexpected
The expected BTS receiving signal level in the initial stagewhen MS access the network.
0~63dBm 30
Stable
EX_LEVExpected
The expected BTS receiving signal level in stable status.
Expected stable signal level > uplink margin HO threshold(HO parameter). Otherwise, ping-pang HO will be caused.
0~63dBm 30
UL RX_LEVcompensati
on
Give an adjustment for the power control level value, theactual power level value MS should change is the result ofthis parameter multiply the difference between the expecteduplink signal level and the actual BTS receiving signal level.
0~100 80
UL Qual.Expected
The expected BTS receiving signal quality in stable status.
UL Qual.
compensation
The power adjustment value varies with this parameter. The
adjustment value caused by signal quality equal to10*difference between the expected signal quality level andthe actual receiving signal quality level times this factor.
0100 20
Max PCstep
The maximum level of MS power that can be dynamicallyadjusted.
Level 1~16,2dB/level.
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Parameter name Meaning Value
rangeValuerecommended
PC interval Time interval between the implementations of twopower control algorithms; unit: SACCH period
0~30 5
Filter length forInitial RX_LEV
This is the number of measurement reportsrequired for predicting the signal strength at theinitial stage. Unit: Measurement reports
1~32 2
Filter length forstable RX_LEV
This is the number of measurement reportsrequired for predicting the signal strength at thestable power control stage. Unit: Measurementreports
1-31 5
Filter length forQual.
This is the number of the measurement reportsrequired for assessing signal quality at the stablestage. Unit: Number of measurement reports
1~30 6
[MS power control table]
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HW I power control judgment
The adjustment on the current output power=(Expected signal
strength in stable status - strength of signal currently received) *
up (down) link compensating factor +[quality of uplink(downlink)
currently received - expected uplink(downlink) quality]*10*
uplink(downlink) quality compensating factor
The final adjustment power level should be no more than the
maximum power control step size, the formula for stable level is:
stable level = currently level + the adjustment value on current
out put power
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HW I Power Control
Power control will not occur in case of these three conditions
Both level and quality equal to the setting values (HW I power
control), or level and quality are within threshold band(HW II
power control)
Adjusting range less than error tolerance
Adjusting range less than minimum power control step
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HW I power control judgment
Before judging the signal level to be adjusted, query the error
tolerance table according to the current transmitting power level.
Adjustment will not be done if the power adjustment value is less
than the error tolerance value.
Error tolerance table for 900M and 1800M is as follows:
HW I Power Control
1800M:
Level
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Error tolerance 2 2 2 2 2 2 2 2 2 3 3 3 3 3 4 4 4 2 2 2
900M
Level
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Error tolerance 2 2 2 4 4 4 4 4 4 4 4 4 4 4 4 4 6 6 6 6
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Comparison uplink and downlink of HW I power control .
Similarity:
1. To avoid frequently changes of signal level, the PC interval time
between the two consecutive uplink and downlink power control are
limited.
2. To reduce the influence caused by abnormal reports, all
measurement reports should be filtered.
3. Both uplink and downlink power controls include level-specific
and quality-specific power controls.
4. Both uplink and downlink power controls have maximum power
control step size limit and compensating factor.
HW I Power Control
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Comparison uplink and downlink of HW I power control .
Differentia:
1. Including power control for the stable status, MS also has power
control when MS access the network, thus to reduce transmitting
power of MS as soon as possible.
2. For uplink, precautions are ready for increase MS transmitting
power in case HO fails.
3. For downlink, there are maximum and minimum transmitting
power limits in power control data configuration.
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HW I power control exercise
Given conditions:
900M MS transmitting at the maximum power, uplink receiving level
of the 900M BTS is 60dBm, uplink quality level is always 0.
Parameter configuration in [BTS power/MS power control table] is
as follows stable RX_LEV Expected is 35, UL RX_LEV
Compensation is 80, UL Qual. expected is 1, and UL Qual.
compensationis 20, and the max. PC step is 16dB.
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HW I power control exercise
Question:
1. Suppose that power control will no longer be done once the
power value to be adjusted is less than 2dB, what is the
approximate stable power value after power control with the above
data configuration?
2. According to the error tolerance list, suppose the initial MS
transmitting power is level 3, what is the maximum uplink receiving
level in stable status after power control?
Exercise
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HW I power control exercise Answers for question 1:
Stable level = current actual level + [(expected signal intensity in
stable status current actual level) * uplink path loss compensating
factor] + [actual current quality expected uplink signal quality) * 10 *
uplink quality compensating factor] = -60+[(-75-(-60))*80 ]+[(0-
1)*10*20] = -60-12-2-74dBm. Now itsnecessary to adjust -14dB
(no larger than the maximum power control step size), but it needs
further adjustment because it fails to reach -75dBm, the expected
signal level in stable status. Use -74 in the above formula again forcalculation, and the power to be adjusted is -2.8dB. Because no
power control adjustment will be done when the power value to be
adjusted is smaller than -2, it still needs to be changed 2dB lower, so
the uplink receiving level is -76dBm at last.
Exercise
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Power control overview
HWpower control
HWpower control
Course Contents
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Power control judgment process
HW I I Power Control
Measurement report pre-processing
The power control demand
according to the receiving
level
General power controljudgement
Send the power controlcommand
The power control
demand according to
receiving quality
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Power control demand based on receiving level.
After measurement report pre-processing, the power control
module makes a comparison between the expected signal level
and the current receiving signal level.
Calculate the transmitting power level step size to be adjusted,
making the receiving level value closer to the expected value.
Adopt variable step size when adjusting the transmitting power
according to the receiving level, so as to achieve the expected
level as soon as possible.
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Power control demand based on receiving quality
After measurement report pre-processing, the power control
module makes comparison between the expected quality level
and the current receiving quality level.
Calculate the step size of the transmitting power level to be
adjusted.
Increase the transmitting power in case of poor receiving quality
Decrease the transmitting power in case of good receiving
quality
Adopt fixed step size when adjust the transmitting power
according to the receiving quality.
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General power control judgment
Power control by receiving
level
Power control by receiving
quality
Power control by signal level
and quality
AdjStep_Lev AdjStep_Qul
max(AdjStep_Lev,AdjStep_Qul) AdjStep_Lev AdjStep_Qul No action
AdjStep_Lev No action AdjStep_Lev
AdjStep_Lev AdjStep_Qul AdjStep_Lev
AdjStep_Lev AdjStep_Qul
max(AdjStep_Lev,AdjStep_Qul)
AdjStep_Lev No action AdjStep_Lev
No action AdjStep_Qul AdjStep_Qul
No action AdjStep_Qul AdjStep_Qul
No action No action No action
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HW I I power control
Power control algorithm implementation
Main feature of HW I I Power control
HW I I Power Control
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HW II power control has the following advantages:
Measurement report compensation -- makes power control
judgment more accurate
Measurement report prediction --to avoid power control later
than needed, the delay is dangerous in case of poor level or bad
quality
Power control expected signal level and quality threshold falls
within a band, this avoids receiving signal level fluctuate up and
down frequently
HW II Power Control
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Measurement report compensation Purpose: Ensure the accuracy of selection of the history
measurement report before filtering.
Implementation steps:
1. Put the current receiving measurement report into the measurementreport compensation queue.
2. Record the changed information of the transmitting power according
to the MS and BTS power levels in the measurement report.
3.After finish the measurement report compensation, system will
compensate the receiving level of the history measurement report
according to the power change information. The compensated
measurement reports will be the original data in the filter process.
4. Filter the compensated measurement reports.
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Measurement report compensation
The expected receiving signal level: 30
The power control will be more effective with measurement report
compensation.
X axis
2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 222 23 24 25 26 27 28 29 3 3 32 33 34 35 36 37 38 39 44 42 43 44 45 46 47 48 49 51234
567
Yaxi
s
Power control diagram when there is
measurement report compensation
Diagram when there is no power control
Power control diagram when there is no
measurement report compensation
Power control effect diagram of measurement report compensation
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Measurement report prediction
Purpose
to avoid power control later than needed, the delay is dangerous in
case of poor level or bad quality
Implementation procedure
1. Analyze the tendency of MR by the historical measurement
reports after interpolation.
2. Guide by the tendency, to predict the values of measurement
report to be received. There are 0~3 measurement reports
prediction, which are configured on OMC.
3. Filter the interpolated, compensated and predicted measurement
reports, and implement power control judgment.
HW II Power Control
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Measurement report prediction
2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2222 23 24 25 26 27 28 29 33 32 33 34 35 36 37 38 39 4 442 43 44 45 46 47 48 49 5X axis
152253354455
Y
ax
is
No power controlMean filter power
control
Prediction filter power
control
Diagram of power control effect comparison between prediction filter and mean filter
The expected receiving signal level: 30
The power control with prediction filter will be more effective than that with
mean filter
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Adaptive power control:
Adaptive power control refers to changeable power control
strategy according to the communication environment, it makes
power control more effective and stable.
Automatically change the adjustable maximum step size of power
control according to different communication environment (different
receiving quality).
Adopt different power control strategies according to different
communication environments (different receiving quality and level).
HW II Power Control
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Power control within the upper/lower thresholds
As for HW II power control in case of calculating power control
step size according to signal level and quality, the signal level
and quality have upper/lower thresholds. Power control will not
execute if the signal level and quality is within the threshold
bands.
Avoid the signal level up-and-down caused by power control.
HW II Power Control
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Simple parameter configuration
All needed to do is to configure simple parameters as follows:
Signal level and quality upper/lower thresholds of up/down link
Three kinds of step sizes for adjustment by level
Step size for adjustment by quality
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[HW II power control table] main parameters 1:
Parameter
nameMeaning
Value
range
Recommen
ded value
filter lengthfor UL
RX_LEV
How many uplink measurement reports obtained for the averageuplink signal level to be used for uplink power control adjustment.
1~20 6
filter lengthfor DL
RX_LEV
How many downlink measurement reports obtained for the averagedownlink signal level to be used for downlink power controladjustment.
1~20 6
filter lengthfor UL Qual.
How many uplink measurement reports obtained for the averageuplink quality level to be used for uplink power control adjustment.
1~20 6
filter lengthfor DL Qual.
How many downlink measurement reports obtained for the averagedownlink quality level to be used for downlink power controladjustment.
1~20 6
MRcompensation allowed
If yes, System put the currently received measurement report intothe measurement report compensation queue, and record thetransmitting power information according to MS and BTS powervalues. And then interpolation, compensate the receiving level
value of the record measurement report according to the powerchange information.
Yes, no Yes
UL MRnumber
predicted
The number of uplink pred. MR in the filter using for power controljudgment.
0~3 reports 2
DL MRnumber
predicted
The number of downlink pred. MR in the filter using for powercontrol judgment.
0~3 reports 2
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[HW II power control table] main parameters
2:Parameter
nameMeaning Value
rangeRecommended
value
PC interval Time between two power control command implementation 1~30(SACCHperiod)
5
UL RX_LEVupper
threshold
This parameter specifies the uplink signal level upper threshold.When the signal level higher than this value, calculate a power
decrement [=receiving level - (upper threshold + lowerthreshold)/2]. This decrement value should consider together withthe maximum step size allowed for different quality zone whichthe receiving signal quality located.
0~63 35
UL RX_LEVlowerthreshold
This parameter specifies the uplink signal level lower threshold.When the signal level higher than this value, calculate a powerincrease [= (upper threshold + lower threshold)/2- receiving level].This increase also consider together with the maximum step sizeallowed for different quality zone which the receiving signalquality located.
0~63 25
UL Qual.upperthreshold
This parameter specifies the uplink quality upper threshold. Level0~7
0
UL Qual.lowerthreshold
This parameter specifies the uplink quality lower threshold forpower control
Level0~7
2
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[HW II power control table] main parameters--3Parameter
nameMeaning Value range
Recommen
ded value
DL RX_LEVupper threshold
This parameter specifies the downlink signal level upperthreshold. When the signal level higher than this value,calculate a power decrement [=receiving level (upperthreshold + lower threshold)/2]. This decrement shouldconsider together with the maximum step size allowed fordifferent quality zone which the receiving signal qualitylocated.
0~63 40
DL EX_LEVlower threshold
This parameter specifies the downlink signal level lowerthreshold. When the signal level higher than this value,calculate a power increase [= (upper threshold + lowerthreshold)/2- receiving level]. This increase also considertogether with the maximum step size allowed for differentquality zone which the receiving signal quality located.
0~63 30
DL Qual. upperthreshold This parameter specifies the downlink quality upperthreshold for power control Level 0~7 0
DL Qual. lowerthreshold This parameter specifies the downlink quality lowerthreshold for power control Level 0~7 2
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[HW II power control table] main parameters--4Parameter
nameMeaning Value range Recommende
d value
max. adj. valuefor Qual. Zone
0
This parameter specifies the maximum power adj.step size allowed when adj. the power according tothe signal level when the Rx quality is 0.
0~30dB 16
max. adj. value
for Qual. Zone1
This parameter specifies the maximum power adj.
step size allowed when adj. the power according tothe signal level when the Rx quality is 1 or 2.
0~30dB 8
max. adj. valuefor Qual. Zone
2
This parameter specifies the maximum power adj.step size allowed when adj. the power according tothe signal level when the R x quality is equal to ormore than 3.
0~30dB 4
adj. PC valueby Rx Qual.
Specifying the adj. step size allow ed when thepower control is adjusted according the receivingsignal quality. That is to say, the step size isconstant for power control by quality, but the stepsize varies with quality in case of power control bysignal level.
0~4dB 4
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Exercises for HW II power control
Given conditions:
The uplink receiving level is -85dBm, the quality is level 4. Power
control algorithm is HW II.
Data configuration is as follows: Uplink signal level upper threshold:
-60dBm, uplink signal level lower threshold: - 80dBm. Uplink signal
upper quality threshold: level 0. Uplink signal lower quality threshold:
level 2. The adjustable step size of quality band 0 is 16dB, of quality
band 1 is 8dB, and of quality 2 is 4 dB. The adjustable step size for
power control by quality is 4dB.
Question: What will be the uplink stable receiving level after
power control?
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Exercises for HW II power control
Answer.
First, transmitting power to be added according to receiving level =
(uplink signal level upper threshold + uplink signal level lower
threshold)/2-actual receiving level (-60 + (-80))/2-(-85)(-70)-(-
85)15dB. As the receiving quality is level 4, only adjustable step
size of quality band 2 can be used -- increase 4dB.
Second, the transmitting power to be increased according to
receiving quality = as powercontrol adjustment step size by quality
is 4dB, thus increase 4dB, the same as adjustment by signal level.
Therefore, according to the general judgement on power control,
4dB should be increased for adjustment either by level or by quality.
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Exercises for HW II power control
Answer .
After the implementation of step 1 power control, the receiving level
becomes: -85dBm + 4dB=-81dBm, Suppose the quality reach
already in level 2 here, it still fails within the expected band -
80dBm~-60dBm. Therefore, it needs to be adjusted.
First: adjust by level -- repeat the previous step: adjustment by level
= (-70) (-81) = 11db, i.e. to increase 11dB. If the receiving quality
has been improved to level 2, and the adjustable step size with
quality band 1 is 8dB. Then, the result of adjustment by level is to
increase 8dB.
Second: adjustment by quality--as the receiving quality value is
between 0 and 2, Needntadjust.
Therefore, the uplink stable receiving level = (-81) + 8 = -73dBm.
Exercise
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