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Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA RadioFrequency Optimization
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Page2Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
ForewordRF (Radio Frequency) optimization is the most important
step to ensure the quality of the network.RF optimization will solve network problems related to
neighbor cell list, coverage and interference.
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Page3Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
ObjectivesUpon completion of this course, you will be able to:
Know the steps of RF optimizationKnow how to solve the RF problems cased by neighbor cell list,
poor coverage and interference
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Page4Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
ContentsRF Optimization Workflow
Typical Problems Analysis in RF optimization
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Page5Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization WorkflowStart
Preparation:Set the optimization targetDivide the optimization clusterDraw out the test route linePrepare the DT tools
Data Collection:DT testIndoor DT testRNC configuration data
The DT result is satisfiedwith optimization target?
RF optimizationfinished
Y
Problem Analysisneighbor cell listpoor coveragepilot pollutionhandoverinterference
N
Adjustment:Engineering parameters adjustNeighbor cell list adjust
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Page6Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization Workflow
5%Pilot pollutionPercentage
30%-40%SHO Percentage
Scanner result 95%CPICH RSCP
-95dBm
Scanner result
95%CPICH Ec/Io
-12dB
CPICH Ec/Io -12dB & RSCP -95dBm
95%Coverage Probability
RemarkReference
ValueTarget Item
Set RF optimization target, for example:
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Page7Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization WorkflowRF optimization clusters division
Cluster is the area for one time drive test
One cluster should contains 15 to 25 sites
Cluster division should consider the following factor, such as:Terrain
Traffic
Route line
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Page8Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization WorkflowPreparation for DT (drive test)
HardwareTest phoneScanner
GPS
SoftwareDrive test software, for example, GENEX Probe
Drive test post process software, for example, GENEXAssistant
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Page9Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
ContentsPreparation of RF Optimization
Typical Problems Analysis in RF optimization
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Page10Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
ContentsTypical Problems Analysis in RF optimization
RF case related to neighbor cell listRF case related to bad coverage
RF case related to interference
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Page11Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1Description
In DT, call drop happenedCheck the signaling trace at UE side
Call DropAfter call drop, begin
to readsystem information
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Page12Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Data analysis
Check cell information from UE active set and cell information
from scanner at call drop points.From ScannerFrom UE
No SC170 cell!!
Why?
Case 1
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Page13Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Data analysis
Checking monitor set
Missing neighbor cell
Delayed handover
Check monitor set forthe scramble measuredby scanner
SC 170 is not in monitor set
Case 1
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Page14Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Data analysis
Check the latest measurement control measurement control
Search for the latest intra-frequency measurement control
Call droppoint
Case 1
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Page15Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Measurement ID is 1. It is Intra-
frequency measurement control
Check the list of intra-frequencyneighbor cell in measurement
control and no SC 170
The primary scrambleof the cell is 6
Case 1
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Page16Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Add neighbor cells in neighbor cell list
Summary
In the beginning stage of network, it is very common thatmissing neighbor cell cased cause call drop.
Analysis with signaling procedure is the common way to find
and solve the problemSome problems can be avoided if the Combined Neighbor Cell
Algorithm is switched on.
Case 1
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Page17Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Phenomenon description
In DT, call drop
happened at cell A
Case 2
Cell B (PSC277)
Cell A(PSC58)
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Page18Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Phenomenon description
In Cell A, UE keeps reporting PSC 277 1A event.
RNC received this event and send Active Set Update to UE
according to the signaling trace record
UE send Active Set Update complete to RNC
Then, RNC send Active Set Update to delete PSC 277 from
active set
Finally call drop happened due to RL failure
Case 2
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Page19Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Problem Analysis
From the signaling trace of DT, it looks like the handover is
complete successfully.
But, according to the signaling trace from CDT, the handover
failed actually.
Case 2
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Page20Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Problem Analysis
Signaling trace from CDT shows:
Case 2
UE NodeB RNC
Measurement control (1A Event for PSC 227)
Radio Link Setup
Radio Link Setup Response
Active set update
Active set update complete
Radio Link Failure
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Page21Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Cell B (PSC277)
Cell A (PSC58)
Cell C (PSC277)Problem Analysis
After checking the
neighbor cell list, the
following problem is
found
Cell C has the same
PSC as Cell B
Case 2
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Page22Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
277C
277B
58A
PSCCell ID
CA
AC
NCell IDCell ID
Cell B(PSC277)
Missingconfiguring
NCellMistake forconfiguring
NCell
Case 2Problem Analysis
The neighbor cell list shows
Cell C(PSC277)
Cell A(PSC58)
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Page23Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Problem Analysis
Based on the analysis above, the new NodeB is not the one of
cell B, but the one of cell C
Even the cell C prepared resource for UE according to the RNC
command of Radio Link Setup, it can not find the UE uplinksignal.
That does why the Radio Link Failure is sent by NodeB
Case 2
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Page24Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Change the wrong neighbor cell list
Case 2
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Page25Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
Phenomenon for wrong neighbor cell listFrom DT, radio link branch is added into active set, then deleted
from active set repeatedly.
SHO success rate is lowRadio link failure is low in the wrong neighbor cell, for example, cell
C in case 2
Call drop is high in the cell with wrong neighbor cell, for example,cell A in case 2
Case 2
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Page26Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
About SHO event, UE will only report PSC to RNC inMeasurement Report
RNC will find the right cell according to the neighbor cell list
between cell ID and PSCThis problem is mainly happened in dense urban when is PSC
is reused a lot
Case 2
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Page27Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
DescriptionCase 3
14603 (Frequency A)
14602 (Frequency B) 14031 (Frequency B)
Inter-frequency handover based on coverage
14605 (Frequency C)
Inter-frequency handover based on capacity
Call drop rate high
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Page28Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
UE is in Cell 14602 with frequency B
When 14602 is in high load level, UE will be handed over to
14603 with another frequency A
When 14603 is in high load level, UE will be handed over to14605 with frequency C
Because frequency A and C are not used continuously at this
area, UE has to be handed over to Cell 14031 with frequency B
14603 and 14605 can share the load level, but the call drop
rate in 14603 is very high.
Case 3
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Page29Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Because its difficult to do drive test for collecting signaling
trace, the IOS (Information of Subscriber) trace is used.
Based on the analysis for the call dropped UE, there is one
thing is common:Before call drop in 14603, all UEs initiated compress mode, and
send Measurement Report to RNC periodically, but handover is
not triggered.
Case 3
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Page30Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
AnalysisCase 3
2D Event
Compressmode
Inter-frequencymeasurement
control
Inter-frequencyMeasurement
report
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Page31Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Open Inter-frequency Measurement Control, the Cell 14605
with frequency C is put in the first place
And in the following measurement report, UE only report Cell
14605But the cell 14605 cell signal level is lower than -90dBm, which
can not trigger handover, till call drop.
Case 3
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Page32Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Measurement Control
Case 3Cell 14605 with
Frequency C
Cell 14031 withFrequency B
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Page33Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Measurement Report
Case 3
Cell 14605 withFrequency C
Cell 14605 CPICH& Ec/Io
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Page34Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Question
Why the handover can not be triggered?
Since the network give UE the information of cell 14605 and
cell 14031, Why UE only report cell 14605?
Did UE measure cell 14031, just not report it?Or, UE never measure cell 14031, just 14605?
Case 3
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Page35Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
UE report cell 14605 CPICH RSCP is 19, which is -96dBm.
After checking the RNC configuration file, this CPICH RSCP
level can not trigger inter-frequency handover
Actually, because cell 14605 and 14603 are in one sector,their signal level should be same.
Case 3
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Page36Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
If UE can report cell 14031, the handover may be triggered
After analyze the compress mode principle, it is found that UE
can only monitor 1 WCDMA frequency in the gap of compress
mode.
Case 3
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Page37Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Because UE can not measure cell 14031 with frequency B,
only monitor cell 14605 with frequency C, and meanwhile cell
14605 and 14603 signal level are the same, the call dropped
due to the poor signal of 14605 and 14603
How to make UE monitor cell 14031 with frequency B instead
of 14605 with frequency C?
Case 3
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Page38Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Delete the neighbor relation from 14603 with frequency A to
14605 with frequency C
Add the neighbor relation from 14602 with frequency B to
14605 with frequency C
Case 3
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Page39Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
SolutionCase 3
14603 (Frequency A)
14602 (Frequency B) 14031 (Frequency B)
14605 (Frequency C)
Inter-frequency handover based on coverage
Inter-frequency handover based on capacity
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Page40Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
Do not configure two different frequency neighbor cells in
WCDMA system
Case 3
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Page41Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Contents
Typical Problems Analysis in RF optimization
RF case related to neighbor cell list
RF case related to bad coverage
RF case related to interference
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Page42Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
In drive test for RF optimization, call drop happened in the
circle area
Case 1
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Page43Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
After analyze the signal level of this area, the call drop is
caused by discontinuous coverage of the cell with PSC 442
Case 1
Problem Zone
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Page44Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
After checking the RF
transmission
environment, the signal
is blocked by the glass
wall
Case 1
The Wall
Call drop
Antenna
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Page45Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Solution 1: Decrease the downtilt to increase the signal level
Maybe the problem area will become better, but due to the wall,
this problem may still exist nearby.
Solution 2:Increase the antenna height
After checking the installation condition, its very hard to increase
the height
Even increased the height, the problem may still exist due to the
wall.
Case 1
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Page46Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Solution 3:
Move the antenna position if possible, and the main direction
antenna is parallel with the side of the wall
Case 1
OriginalPosition
New
Position
WallMove the antenna position to
right about 15 meters
considering the installation
condition
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Page47Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Solution 3:
About the antenna downtilt, two strategies are designed.
First, 10 degrees
Case 1
10 Degree
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Page48Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Solution 3:
Second, 5 degrees
Case 1
5 Degree
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Page49Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
Before RF adjustment, site survey should be done.
Find the problem and the reason, design several strategies for
the adjustment
One time adjustment, and check the performance at the sametime. Adjustment and performance checking should be done at
the same to improve the work efficiency.
Case 1
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Page50Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
In drive test for RF optimization, the area Ec/Io is bad
Case 2
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Page51Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Checking the cell distribution at this area
Case 2
PSC185
PSC184PSC186
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Page52Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
One site with 3 cells, PSC184, 185 and 186 cover this area
Two cells, PSC 184 and 185, are separated to two sectors to
cover different direction
Case 2
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Page53Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
The area is covered by different cell PSC 184 and 185
No dominant cell PSC 184 and 185 is the best cell crossly in
this area
Case 2
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Page54Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Change the sector PSC, or combine some sector
Previously, 3 cells
PSC 184: sector 1 & sector 3
PSC 185: sector 2 & sector 4PSC 186: sector 5
After adjustment, 2 cells:
PSC184: sector1 & sector3
PSC185: sector4 & sector5
Delete sector 2
Case 2
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Page55Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
After adjustment, the drive test for PSC 184 and 185
Case 2
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Page56Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
The comparison result for scanner Ec/Io
Case 2
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Page57Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
The comparison result for UE Ec/Io
Case 2
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C 3
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Page59Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
In drive test for RF optimization, bad Ec/Io is found on the
bridge
Case 3
C 3
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Page60Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check the RSCP value of scanner, the result shows the RSCP
value is good.
Case 3
Based on this, pilot pollution
need be considered in this
area.
Check the top N pilot RSCP
and Ec/Io in scanner result
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C 3
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Page62Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Case 3
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
Case 3
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Page63Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
On the bridge, the signal from different cell can cover this area
due to reflection of the river and no building.
From DT, following cell cover this area:
Site 1 cell A
Site 2 cell C
Site 3 cell C
Site 4 cell CSite 5 cell C
Case 3
Case 3
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Page64Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Need to find the
best cell
Check the map,
the site 6 is very
near to the
bridge.
Case 3
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
Site 6
Case 3
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Page65Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
After checking site 6 RF
environment, it is difficult to
increase the antenna height or
move site 6 position to avoid
the blocking caused by the
building
Case 3
The residence buildingsare much higher thanantenna, which block
the signal of site 6
Case 3
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Page66Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Then, site 1 cell
A can be the
best cell to
cover this area
Case 3
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
Case 3
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Page67Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Then, try to
increase the
signal of site 1
cell A, and
decrease other
cells
To confirm this,
DT for site 1 cell
A needs to be
done
Case 3
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
Case 3
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Page68Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Increase the signal of site 1 cell A
Change the antenna downtilt from 10 to 7
Increase CPICH Tx power 1.5 dB higher
Decrease other cell signal change the antenna downtilt
From 7 to 10 for site 2 cell C
From 5 to 8 for Site 3 cell C
From 9 to 11 for site 4 cell CFrom 9 to 11 for site 5 cell C
Case 3
Case 3
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Page69Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Confirmation
After the modification, the DT shows the pilot pollution area
as below
Case 3
Case 3
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Page70Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Confirmation
The Ec/Io comparison
Case 3
After
Before
Case 3
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Page71Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
To solve the pilot pollution, the following issues has be
considered
Find the reason caused pilot pollution
Due to no strong signal
Due to too much strong signal
After the adjustment, the DT has to be done at this cluster to
confirm that no new problem appeared
Case 3
Case 4
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Page72Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
In DT, video call quality is decreased at the problem
area. Also, the PS call drop happened several times
Case 4
Problem Area
3G Antenna
2G Antenna
Case 4
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Page73Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
RSCP distribution in DT
Case 4
Problemarea
Case 4
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Page74Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Ec/Io distribution in DT
Case 4
Problemarea
Problemarea
Case 4
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Page75Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Checking the RF environment, the antenna is installed on 10-
meter platform
2G and 3G antenna are installed at one platform, but 3G
antenna is a little bit inner than 2G antenna.
After finishing DT in 2G, signal level is very stable
Case 4
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Page76Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
If 3G and 2G antenna are installed at the same place, the
problem may be solved.
Problem Area
3G Antenna
2G Antenna
The short wall of this
platform may block
the signal of 3G
Since 2G antenna is
near to the border, the
wall influence 2G little
Wall
Case 4
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Page77Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Solution 1
Increase the antenna height can solve this problem
Solution 2
Move the installation place near to the border
Solution 3
3G and 2G use the same place
Case 4
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Page78Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Solution 3 is adopted
Road
RX
RX
T
X/
RX
T
X/
RX
2G
BTS
3G
NodeB
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Case 4
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Page80Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
Sharing the same installation place for 3G and 2G is
very common, and several strategies can solve the
problem
In this situation, 3G and 2G can share the feeder
system, or can only share the installation platform.
Considering the factors of the installation and related
resource, a easiest and simplest method should be
adopted
Case 5
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Page81Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
In DT, call drop happened a lot in the area
Case 5
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Page82Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
Check the DT information, SC304 is in active set with
the signal level RSCP -76dBm and Ec/Io -18
Analysis
Consider the pilot pollutionBut only 1 cell in active set and 1 Cell in monitor set
Consider the missing neighbor cell
But the cell in monitor set has very good quality
RSCP -65dBm and Ec/Io -6
Case 5
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Page83Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check the signaling trace at UE sideBefore call drop, UEsends measurement
report to RNC with 1Aevent for cell 298
Case 5
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Page84Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check the signaling trace at RNC side
RNC sent Active Set Update toUE, but no response. Then, RNCsend release RRC connection
Call Drop
Case 5
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Page85Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Based on the DT and signaling trace, this call drop
can be take as handover failure
For example
cell56 vs cell041
-30
-20
-10
0
time
E c
N o cell56
cell041
Case 5
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Page86Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Around the corner, the original cell 304 signal level
drop very quickly because of the building
shadowing, and the neighbor cell 298 increase
very quickly.
After UE sent measurement report to RNC, cell
304 has become very bad when RNC sent active
set update.
Case 5
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Page87Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Adjustment
Since cell 298 has better coverage at this area,
handover can happen earlier
Decrease the coverage performance at this area Increase the downtilt from 5 to 9
Adjust the direction from 0 to 310
Increase the coverage performance at this area
Decrease the downtilt from 5 to 4
Adjust the direction from 300 to 270
Case 5
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Page88Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Adjustment
Result after adjustment
Handoverarea
HandoverareaBefore After
Case 5
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Page89Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Adjustment
Comparison of Ec/Io of UE
Before After
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Page90Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
Confirm the corner effect by analyzing signaling
trace at UE and RNC
About corner effect, Taking the method make the
handover happen earlier, such as RF optimizationOther method can also adopted
Modify 1A event
Modify CIO (Cell Individual Offset)
Contents
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Page91Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Typical Problems Analysis in RF optimization
RF case related to neighbor cell list
RF case related to bad coverage
RF case related to interference
Case 1
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Page92Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
-105.4-101.6-822006-5-16 17:00KwongYu3625031
-105.5-94.89-74.32006-5-16 17:00KwongYu2625021
-105.3-102.34-74.52005-5-16 17:00KwongYu1625011
VS.MinRTWPVS.MeanRTWPVS.MaxRTWPTime(As hour)CellNameCellIdRNCId
Description
From traffic statistic, the following RTWP problem is found
Case 1
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Page93Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Connect to the problem NodeB, and monitor the RTWP
Cell 62501 RTWP
Case 1
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Page94Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Cell 62502 RTWP
Case 1
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Page95Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Cell 62503 RTWP
Case 1
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Page96Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
The main diversity antenna is interfered seriously
Can not find any relation between interference and time,
and the interference appears randomly
Check the neighbor site, no interference
Deduction
Inter-modulation cause the interference, could be
Inter-modulation caused by bad connectorsInter-modulation by GSM
Case 1
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Page97Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check the RF environment
Case 1
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Page98Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check the RF environment
No blocking or any reflection due to the glass wall
The site RF condition is very good
Case 1
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Page99Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
2G and 3G share the feeder system
Case 1
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Page100Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check 2G frequency planning
Sector 1 544 with hopping frequency 821
544 1811.6MHz & 821 1867MHz
Sector 2 538 with hopping frequency 821
538 1808.6MHz & 821 1867MHz
Sector 3 858 with hopping frequency 821
858 1874.4MHz & 821 1867MHz
Case 1
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Page101Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Calculate the third order intermodulation
Cell 1 1922.4MHz
Cell 2 1925.4MHz
Cell 3 1859.6MHz
Check cell 2 uplink interference
The interval of 2 interference is
821-544
Case 1
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Page102Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Conclusion
The third intermodulation of cell 1 and cell 2 is just in WCDMA
uplink band
Case 1
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Page103Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Solution
Change the hopping frequency of DSC
Confirmation
Check the RTWP again, the values are normal
Case 1
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Page104Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Summary
Characteristics of inner system interference
The RTWP result are not same at the main and diversity antenna
The amplitude of interference is big, and the difference is more than 10
dB
High RTWP will appear in a duration, and will not change so frequentlyHigh RTWP will not show in a certain time each day, but randomly
Case 2
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Page105Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Description
In a commercial network of country U, the following RTWP
problem is found from traffic statistic
-105.65-92.65-97.722005-11-15 2:00Pocitos_C11643201
-104.65-96-97.12005-11-15 20:00Palacio_C11461201
-105.65-91-96.742005-11-15 0:00Ciudad Vieja_C11623201
-97.65-93.65-96.622005-11-15 17:00Centro_C11932201
-105.66-87.65-95.862005-11-15 4:00Centenario_C11942201
-105.66-88.65-93.942005-11-15 4:00Aguada_C11912201
RTWP_MINRTWP_MAXRTWP_MEANTime(As hour)CellNameCellIdRNCId
Case 2
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Page106Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Connect to the problem NodeB, and monitor the RTWP
Take one site as example
Case 2
A l i
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Page107Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
The main and diversity antenna have the same
interference trend
The different between main and diversity is less than
10dB
Case 2
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Page108Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Check the location of the sites with high RTWP
High
Medium
Low
Case 2
A l i
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Page109Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
All the problem cells are in the third sector of the NodeB,
and the direction is to the northwest
Many cells at this area show high interference, and the
cells with low RTWP are at low place
Case 2
Analysis
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Page110Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Analyze the RTWP in the nearly one month, the
interference shows randomly, but if appears, usually onewhole day, or several days
The interference shows with high traffic, and also with
low traffic. No evidence shows it is related to the traffic
Case 2
Analysis
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Page111Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Maybe the interference comes from outside and the
northwest direction
Case 2
Analysis
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Page112Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Use YBT250 to do the interference checking
Case 2
Analysis
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Page113Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
All the test results show the interference comes from the
same direction to the country A
But the distance to country A from the test place is
around 50Km to 200Km
Case 2
Analysis
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Page114Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Frequency analysis
U Country UMTS frequency
1900MHz
A country GSM frequency
1900MHz
Case 2
Analysis
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Page115Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Analysis
Maybe the interference comes from A country, but looks
like impossible because the distance (50 to 200Km) isbeyond the transmission
To confirm this problem, use A country cell phone at the
area with high RTWP
The result shows the phone does receive the A country
DSC
Case 2
Conclusion
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Page116Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Conclusion
The interference comes from A country GSM
Even the distance is very far, the area between the
border is covered by a large water area
Due to reflection the water, the signal can be transmitted
far away
Case 2
Conclusion
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Page117Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
After known the reason, the following character of this
kind of interference is foundRelated to the weather
Rain day, no interference
Cloudy day, less interference Sunny day, high interference
Related to the seasons also
Problems show at Summer more than Winter
Case 2
Summary
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Page118Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
y
Characteristics of external interference
The RTWP result are same at the main and diversity antenna
The amplitude of interference is small, and the difference is less than 10
dB
The interference exists at large area, not just one cell, also including
neighbor cells
The direction of external interference is obvious
The cell with high antenna is easier to be interferenced
Summary
RF optimization
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Page119Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Neighbor cell list optimization
Coverage performance optimization
Interference optimization
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Thank youwww.huawei.com