OMD0560 Power control ISSUE1.1Adjust the transmitting power of BTS
and MS when needed.
Based on measurement reports of BTS and MS
Purpose
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.
1. During handover, MS will access the target cell with the maximum
transmitting power (associated handover command) allowed by the
target cell. But if “MS power prediction after HO” is enable, then
MS will use the optimized power to access the target cell.
2. During intra-cell handover, the current power will be
retained.
3. Power control can be implemented on TCH carriers only, BCCH
carrier is not allowed power control. Because MS needs to measure
the receiving level of BCCH from the adjacent cell. It will be
inaccurate when power control is performed on BCCH.
4. Power control is performed independently for each channel.
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It takes 3 measurement report periods(480ms/period) from command
sending to execution.
SA0
SA1
SA0
SA0
SA1
SA1
SA2
SA2
SA2
SA3
SA3
SA3
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 new power level and TA
MS begins to set up a new SACCH header to report the new TA and
power control message.
When MS accesses the network via RACH channel, its transmitting
power is the “MS max. TX power level” get from the system
information sent on BCCH. MS send the first message on dedicated
channel also uses the “MS max TX power level” ,this is not under
the control of the system before the power control command which
carried on SACCH of SDCCH or TCH. The implementation procedure is
as follows:
1. According to the uplink receiving level and receiving quality
reported by BTS, consider the maximum transmitting power of MS, BSC
calculates the proper transmitting power for the MS.
2. Power control command and the TA value will be transmitted to MS
at layer 1 header carried by each downlink SACCH block.
3. MS receives the power control command carried by SACCH header at
the end of each SACCH report period, Then MS will carry out the
command in the beginning of next report period. MS can change power
2dB per 13 frames (60ms) maximum.
4. After MS executed the power control command, it will set the
current power class at the layer 1 message header of the next
uplink SACCH, and transmit it to BTS in the measurement report.
Therefore, it will take 3 measurement report periods for the new
power class (in each power control command) to be available.
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Power Control Overview
Huawei power control algorithm: HW I and HW II power control
Measurement report pre-processing
Power control algorithm
algorithm
HWII power control is developed based on HWI. It’s more sensitive
and the data configuration is simpler. For details, see later
sections.
Huawei can support 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 measurement report
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. If measurement report
pre-processing is “yes”, power control is processed in BTS, and
when setting it “no”, power control is processed in BSC.
Set pre-processing “yes” is to reduce the signaling load in Abis
interface.
i.e.:
1.If Abis E1 is in 15:1 mode, it should be set “yes”, otherwise the
Abis capacity for speed is not enough;
2.BTS22C 0110 version should be set “No”;
3.Satellite transmission BTS should be set “yes”;
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MR pre-processing
comparison of uplink power control with downlink power
control
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Measurement report pre-processing
HW I Power Control
In HWI power control, after the BSC or BTS performs pre-processing
(interpolation and filtering) on the original measurement report,
it will start HWI power control algorithm, and send the power
control command.
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Network
HW I Power Control
The original data of power control is from measurement report. MS
submits a measurement report to the network on SACCH channel every
480ms, the content reported by MS is the downlink measurement
values which received by MS.
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Uplink measurement report
Downlink measurement report
There are two kind of measurement report for system: FULL (full
measurement) and SUB (sub measurement).
FULL--Averaging over 100 TCH bursts(except four idle frames of four
26-multiframes).
SUB--Averaging over 12 bursts(four SACCH bursts, eight TCH
bursts).
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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.
HW I Power Control
Measurement report serial number n+4
Consecutive measurement report flow
3 missing measurement reports
The network receives the measurement reports n and n+4, which are
with discontinuous serial numbers. Therefore the three missed
measurement reports n+1, n+2 and n+3 will be filled up with some
algorithm.
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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.
HW I Power Control
Filter
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[BTS power control table]
HW I Power Control
The parameter configuration for HW I includes two sheets: [BTS
power control table] and [MS power control table] for downlink and
uplink power control. When the “HW_1” in “PC algorithm ” is
selected, the network will perform power control according to these
two sheets.
Only some of key parameters are listed above.
Parameter name
DL RX_LEV Expected
The expected signal level of MS in stable status, Expected stable
downlink signal level > downlink edge HO thresholdOtherwise,
ping-pang HO will be caused.
063
DL RX_LEV Compensation
The power adjustment value varies with this parameter. The
adjustment value caused by power level equal to the difference
between the expected signal level and the actual receiving signal
level multiply this factor.
0100
DL Qual. Expected
07 Levels
DL Qual.Compensation
The power adjustment value varies with this parameter. The
adjustment value caused by signal quality equal to 10*difference
between the expected signal quality level and the actual receiving
signal quality level multiply this factor.
0100
MAX PC Step
Levels 0~16, 2dB each step
8
24.unknown
Period
Time interval for implementing two power control commands (unit
count of SACCH period)
110
Filter length for DL RX_LEV
Content: indicating the number of measurement reports in which the
average of uplink signal strength is taken before MS power
adjustment at stable stage. The purpose is to remove the influence
of some abnormal reports. When the filter length is too long, the
influence due to abnormal reports will be weakened, but the MS
power adjustment is not timely.
132
Indicating the minimum transmitting power value supported by the
BTS
0~36
Indicating the maximum transmitting power value supported by the
BTS.
0~56
HW I Power Control
Parameter name
initial RX_LEV expected
The expected BTS receiving signal level in the initial stage when
MS access the network.
0~63dBm
Stable EX_LEV Expected
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
UL RX_LEV compensation
Give an adjustment for the power control level value, the actual
power level value MS should change is the result of this parameter
multiply the difference between the expected uplink signal level
and the actual BTS receiving signal level.
0~100
UL Qual. compensation
The power adjustment value varies with this parameter. The
adjustment value caused by signal quality equal to 10*difference
between the expected signal quality level and the actual receiving
signal quality level times this factor.
0100
Max PC step
The maximum level of MS power that can be dynamically
adjusted.
Level 1~16, 2dB/level.
Value range
Value recommended
PC interval
Time interval between the implementations of two power control
algorithms; unit: SACCH period
0~30
Filter length for Initial RX_LEV
This is the number of measurement reports required for predicting
the signal strength at the initial stage. Unit: Measurement
reports
1~32
Filter length for stable RX_LEV
This is the number of measurement reports required for predicting
the signal strength at the stable power control stage. Unit:
Measurement reports
1-31
5
Filter length for Qual.
This is the number of the measurement reports required for
assessing signal quality at the stable stage. Unit: Number of
measurement reports
1~30
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
HW I Power Control
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
Error tolerance: Measured in dB, varies with MS transmitting
power.
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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
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.
HW I Power Control
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. compensation” is
20, and the max. PC step is 16dB.
HW I Power Control
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
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 it’s
necessary 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 for calculation, 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
Answers for question 2:
Query the error tolerance table, the tolerance of level 3 is 4dB,
the power to be adjusted for the second time is 2.8, which is less
than 4 and up to the requirement, so the final uplink receiving
level is -74dBm in stable status.
Exercise
Power control algorithm implementation
HW I I Power Control
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Measurement report pre-processing
General power control judgement
The power control demand according to receiving quality
HWII power control is performed in four steps.
Pre-processing of the measurement reports (interpolation and
filtering),
2. Calculate power control demand according to the receiving
level,
3. Calculate power control demand according to the receiving
quality,
4. Make comprehensive judgment on the receiving level and 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.
HW I I Power Control
When power control is performed based on the receiving level, it
adopts three step sizes respectively for different receiving
qualities band:
“MAX. Adj. Value for Qual. Zone 0 (receiving quality level 0)
“MAX. Adj. Value for Qual. Zone 1 (receiving quality level
1~2)
“MAX. Adj. Value for Qual. Zone 2 (receiving quality level
3~7)
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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.
HW I I Power Control
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Note:
1. Control as required when either level or quality needs to be
controlled.
2. When the controls based on signal level and quality are in an
opposite direction, and the level requires decreasing power, so no
action should be performed for power control; when the level
requires increasing power, then just perform as level
required.
3. When they work in the same direction, perform according to the
larger value.
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
Power control algorithm implementation
HW I I Power Control
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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
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
measurement report 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.
HW II Power Control
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The expected receiving signal level: 30
The power control will be more effective with measurement report
compensation.
HW II Power Control
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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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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The expected receiving signal level: 30
The power control with prediction filter will be more effective
than that with mean filter
HW II Power Control
Mean filter power control
Prediction filter power control
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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
Automatic adjustable step size:
When the power control caused by receiving level in HWII power
control algorithm, the power control will be performed also
considering the receiving quality which are set into three quality
zones (0, 1~2, ≥3). Each quality zone allow different maximum
adjustment step size. The worse the quality is, the less the
adjustable step size will be.
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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
DL RX_LEV upper thrsh/lower thrsh
UL Qual upper thrsh/lower thrsh
DL Qual upper threh/lower threh
*
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
HW II Power Control
*
HW II Power Control
filter length for UL RX_LEV
How many uplink measurement reports obtained for the average uplink
signal level to be used for uplink power control adjustment.
1~20
filter length for DL RX_LEV
How many downlink measurement reports obtained for the average
downlink signal level to be used for downlink power control
adjustment.
1~20
filter length for UL Qual.
How many uplink measurement reports obtained for the average uplink
quality level to be used for uplink power control adjustment.
1~20
filter length for DL Qual.
How many downlink measurement reports obtained for the average
downlink quality level to be used for downlink power control
adjustment.
1~20
MR compensation allowed
If “yes”, System put the currently received measurement report into
the measurement report compensation queue, and record the
transmitting power information according to MS and BTS power
values. And then interpolation, compensate the receiving level
value of the record measurement report according to the power
change information.
Yes, no
UL MR number predicted
The number of uplink pred. MR in the filter using for power control
judgment.
0~3 reports
DL MR number predicted
The number of downlink pred. MR in the filter using for power
control judgment.
0~3 reports
HW II Power Control
Note: when configuring s-strength thresholds that: upper/lower
thresholds> edge handover threshold + inter-cell handover
hysteresis.
This is designed to avoid handover caused by improper power
control.
Parameter name
1~30
(SACCH period)
UL RX_LEV upper 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 + lower
threshold)/2]. This decrement value should consider together with
the maximum step size allowed for different quality zone which the
receiving signal quality located.
0~63
UL RX_LEV lower threshold
This parameter specifies the uplink signal level lower threshold.
When the signal level higher than this value, calculate a power
increase [= (upper threshold + lower threshold)/2- receiving
level]. This increase also consider together with the maximum step
size allowed for different quality zone which the receiving signal
quality located.
0~63
Level 0~7
UL Qual. lower threshold
This parameter specifies the uplink quality lower threshold for
power control
Level 0~7
HW II Power Control
DL RX_LEV upper threshold
This parameter specifies the downlink signal level upper threshold.
When the signal level higher than this value, calculate a power
decrement [=receiving level – (upper threshold + lower
threshold)/2]. This decrement should consider together with the
maximum step size allowed for different quality zone which the
receiving signal quality located.
0~63
DL EX_LEV lower threshold
This parameter specifies the downlink signal level lower threshold.
When the signal level higher than this value, calculate a power
increase [= (upper threshold + lower threshold)/2- receiving
level]. This increase also consider together with the maximum step
size allowed for different quality zone which the receiving signal
quality located.
0~63
DL Qual. upper threshold
This parameter specifies the downlink quality upper threshold for
power control
Level 0~7
DL Qual. lower threshold
This parameter specifies the downlink quality lower threshold for
power control
Level 0~7
HW II Power Control
max. adj. value for Qual. Zone 0
This parameter specifies the maximum power adj. step size allowed
when adj. the power according to the signal level when the Rx
quality is 0.
0~30dB
max. adj. value for Qual. Zone 1
This parameter specifies the maximum power adj. step size allowed
when adj. the power according to the signal level when the Rx
quality is 1 or 2.
0~30dB
max. adj. value for Qual. Zone 2
This parameter specifies the maximum power adj. step size allowed
when adj. the power according to the signal level when the Rx
quality is equal to or more than 3.
0~30dB
adj. PC value by Rx Qual.
Specifying the adj. step size allowed when the power control is
adjusted according the receiving signal quality. That is to say,
the step size is constant for power control by quality, but the
step size varies with quality in case of power control by signal
level.
0~4dB
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?
Exercise
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 “power control 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.
Exercise
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, Needn’t adjust.
Therefore, the uplink stable receiving level = (-81) + 8 =
-73dBm.
Exercise
and quality
↓ AdjStep_Lev ↓ AdjStep_Qul ↓
Parameter
name
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
adjustment value caused by power level equal to the
difference
between the expected signal level and the act ual receiving
signal level multiply this factor.
0100 80
07
adjustment value caused by signal quality equal to
10*difference between the expected signal quality level and
the
actual receiving signal quality level multiply this factor.
0100 20
command
Levels
(unit count of SACCH period)
110
Content: indicating the number of measurement reports in
which the average of uplink signal strength is taken before
MS
power adjustment at stable stage. The purpose is to remove
the influence of some abnormal reports . When the filter
length
is too long, the influence due to abnormal reports will be
weakened, but the MS power adjustment is not timely .
132
the BTS
by the BTS.
The expected BTS receiving signal level in the initial stage
when MS access the network.
0~63dBm 30
Expected stable signal level > uplink margin HO threshold
(HO parameter). Otherwise, “ping -pang” HO will be caused.
0~63dBm 30
Give an adjustment for the power control level value, the
actual power level value MS should change is the result of
this parameter multiply the difference between the expected
uplink signal level and the actual BTS receiving signal
level.
0~100 80
UL Qual.
adjustment value caused by signal quality equal to
10*difference between the expected signal quality level and
the actual receiving signal quality level times this factor.
0100 20
The maximum level of MS power that can be dynamically
adjusted.
How many uplink measurement report s obtained for the average
uplink signal level to be used for uplink power control
adjustment.
1~20 6
How many downlink measurement report s obtained for the
average
downlink signal level to be used for downlink power control
adjustment.
How many uplink measurement report s obtained for the average
uplink quality level to be used fo r uplink power control
adjustment.
1~20 6
How many downlink measurement report s obtained for the
average
downlink quality level to be used for downlink power control
adjustment.
If “yes”, System put the currently received measurement report
into
the measurement report compensation queue, and record the
transmitting power information according to MS and BTS power
values. And then interpolation, compensate the receiving
level
value of the record meas urement report according to the
power
change information.
number
predicted
The number of uplink pred. MR in the filter using for power
control
judgment.
number
predicted
The number of downlink pred. MR in the filter using for power
control judgment.
calculate a power decrement [=receiving level – (upper
threshold + lower threshold)/2 ]. This decrement should
consider together with the maximum step size allowed for
different quality zone which the receiving signal quality
located.
calculate a power increase [= (uppe r threshold + lower
threshold)/2- receiving level]. This increase also consider
together with the maximum step size allowed for different
quality zone which the receiving signal quality located.
0~63 30
DL Qual. upper
threshold for power control
Level 0~7 0
threshold for power control
Level 0~7 2
range
Recommended
value
PC interval Time between two power control command implementation
1~30
(SACCH
period)
5
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 + lower
threshold)/2]. This decrement value should consider together
with
the maximum step size allowed for different quality zone
which
the receiving signal quality located.
0~63 35
This parameter specifies the uplink signal level low er
threshold.
When the signal level higher than this value, calculate a
power
increase [= (upper threshold + lower threshold )/2- receiving
level].
This increase also consider together with the maximum step
size
allowed for different quality zone which the receiving signal
quality located.
0~7
power control