wcdma rf optimization
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www.huawei.com
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.
Forewordl RF (Radio Frequency) optimization is the most important step to
ensure the quality of the network.
l 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.
Objectivesl Upon completion of this course, you will be able to:
p Know the steps of RF optimization
p Know 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.
Contents
l RF Optimization Workflow
l Typical Problems Analysis in RF optimization
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Page5Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization WorkflowStart
Preparation:
l Set the optimization target
l Divide the optimization cluster
l Draw out the test route line
l Prepare the DT tools
Data Collection:
l DT test
l Indoor DT test
l RNC configuration data
The DT result is satisfied
with optimization target?
RF optimization
finished
Y
Problem Analysis
l neighbor cell list
l poor coverage
l pilot pollution
l handover
l interference
N
Adjustment:
l Engineering parameters adjust
l Neighbor cell list adjust
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Page6Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization Workflow
5%Pilot pollution Percentage
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
Value Target Item
l Set RF optimization target, for example:
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Page8Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
RF Optimization Workflowl Preparation for DT (drive test)
p Hardware
n Test phone
n Scanner
n GPS
p Software
n Drive test software, for example, GENEX Probe
n Drive test post process software, for example, GENEX Assistant
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Page9Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Contentsl Preparation of RF Optimization
l Typical Problems Analysis in RF optimization
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Page10Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Contents
l Typical Problems Analysis in RF optimization
p RF case related to neighbor cell list
p RF case related to bad coverage
p RF case related to interference
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Page11Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Description
p In DT, call drop happened
p Check the signaling trace at UE side
Call Drop After call drop, begin
to read
system information
From the tracing result we can see that after UE send measurement
report it doesnt receive response from network and starts to read
system information. It means UE loses connection with network andgoes back to idle mode. It is a call drop.
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Page13Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Data analysis
p Checking monitor set
p Missing neighbor cell
p Handover failure
Check monitor set for
the scramble measured
by UE
SC 170 is not in monitor set
Case 1
We check the monitor set of the UE, still can not find the cell with
SC170.
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Page14Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Data analysis
p Check the latestmeasurement contro l measurement contro l
Search for the latest intra-
frequency measurement control
Call droppoint
Case 1
In order to confirm the guess for missing neighboring cell we check the
measurement control signaling from network because we can find the
configured neighboring cells in the signaling.
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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-frequency
neighbor cell in measurement
control and no SC 170
The primary scramble
of the cell is 6
Case 1
The result shows that there is no cell with SC170 in measurement
control signaling. So the case is confirmed and it is because of missing
neighboring cell.
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Page16Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Add neighbor cells in neighbor cell list
l Summary
p In the beginning stage of network, it is very common that missing
neighbor cell cased cause call drop.
p Analysis with signaling procedure is the common way to find and
solve the problem
p Some 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.
l Phenomenon description
p In DT, call drop
happens at cell A
Case 2
Cell B (PSC277)
Cell A
(PSC58)
Call drop happens at cell A when UE is moving from cell A to cell B.
The primary code is 58 in cell A and it is 277 in cell B.
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Page18Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Phenomenon description
p In Cell A, UE keeps reporting PSC 277 1A event.
p RNC receives this event and send Active Set Update to UE according
to the signaling trace record
p UE sends Active Set Update complete to RNC
p Then, RNC sends Active Set Update to delete PSC 277 from activeset
p Finally call drop happens due to RL failure
Case 2
UE detected that the signal of SC277 is good and report 1A event to
network. Network receives 1A event and decides to trigger soft
handover, so it send active set update to UE and then UE send activeset update complete to network. From these phenomenon It seems that
the soft handover procedure is complete.
But after that network sends active set update again to UE and the
content in active set update is to delete SC277. It is abnormal. Finally
call drop happens.
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Page19Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Problem Analysis
p From the signaling trace of DT, it looks like the handover is complete
successfully.
p But, according to the signaling trace from CDT (call detailed tracing),
the handover fails actually.
Case 2
Drive test just shows the signaling in the Uu interface. In this case it
looks like normal for active set update and active set update complete.
But if we trace all corresponding signaling from CDT we can find thehandover is not successful.
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Page20Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Problem Analysis
p Signaling trace from CDT shows:
Case 2
UE NodeB RNC
Measurement report (1A Event for PSC 227)
Radio Link Setup
Radio Link Setup Response
Active set update
Active set update complete
Radio Link Failure
The signaling tracing result from CDT shows that NodeB can not
synchronize radio link with UE so it reports radio link failure to RNC. So
handover fails and call drops. But why the previous signaling is normal?
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Page21Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Cell B (PSC277)
Cell A (PSC58)
Cell C (PSC277)
l Problem Analysis
p After checking the
neighbor cell list, the
following problem is
found
p Cell C has the same
PSC as Cell B
Case 2
We check the neighboring cell list of cell A and find the problem. Cell C
which is far away from cell A has the same scrambling code 277 with
cell B.
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Page22Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
277C
277B
58 A
PSCCell ID
C A
AC
NCell IDCell ID
Cell B
(PSC277)
Missing
configuringNCell Mistake forconfiguring
NCell
Case 2l Problem Analysis
p The neighbor cell list shows
Cell C
(PSC277)
Cell A
(PSC58)
Cell B should be the neighboring cell of cell A but the actual
configuration is that cell C is the neighboring cell of cell A. It is obviously
wrong configuration and it causes handover failure and call drop.
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Page23Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Problem Analysis
p Based on the analysis above, the new NodeB is not the one of cell
B, but the one of cell C
p Even the cell C prepared resource for UE according to the RNC
command of Radio Link Setup!, it can not find the UE uplink signal.
p That is why the Radio Link Failure! is sent by NodeB
Case 2
After RNC receives 1A event for SC277, it asks NodeB to prepare radio
resource. But this NodeB is not the one for cell B but for cell C. Cell C is
far away from cell A can the NodeB can not find the UE, so the NodeBsends radio link failure to RNC.
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Page24Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Change the wrong neighbor cell list
Case 2
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Page25Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Summary
p Phenomenon for wrong neighbor cell list
n From DT, radio link branch is added into active set, then deleted from
active set repeatedly.
n SHO success rate is low
n Radio link failure is high in the wrong neighbor cell, for example, cell C in
case 2
n 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.
l Summary
p About SHO event, UE will only report PSC to RNC in Measurement
Report
p RNC will find the right cell according to the neighbor cell list
between cell ID and PSC
p This 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.
Contents
l Typical Problems Analysis in RF optimization
p RF case related to neighbor cell list
p RF case related to bad coverage
p RF case related to interference
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Page28Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Description
p In drive test for RF optimization, call drop happened in the circle
area
Case 1
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Page29Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p 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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Page30Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p 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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Page31Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Solution 1: Decrease the downtilt to increase the signal level
n Maybe the problem area will become better, but due to the wall, this
problem may still exist nearby.
p Solution 2:Increase the antenna height
n After checking the installation condition, it"s very hard to increase the
height
n Even increased the height, the problem may still exist due to the wall.
Case 1
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Page32Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Solution 3:
n Move the antenna position if possible, and the main direction antenna
is parallel with the side of the wall
Case 1
Original
Position
New
Position
Walln Move the antenna position to right
about 15 meters considering the
installation condition
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Page33Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Solution 3:
n About the antenna downtilt, two strategies are designed.
n First, 10 degrees
Case 1
10 Degree
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Page34Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Solution 3:
n Second, 5 degrees
Case 1
5 Degree
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Page35Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Summary
p Before RF adjustment, site survey should be done.
p Find the problem and the reason, design several strategies for the
adjustment
p One time adjustment, and check the performance at the same time.
Adjustment and performance checking should be done at the same
to improve the work efficiency.
Case 1
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Page36Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Description
p In drive test for RF optimization, bad Ec/Io is found on the bridge
Case 2
Bad Ec/Io
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Page37Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p Check the RSCP value of scanner, the result shows the RSCP value
is good.
Case 2
p Based on this, pilot pollution
need be considered in this area.
p Check the top N pilot RSCP and
Ec/Io in scanner result
From the drive test result of scanner we can see that there are five cells
with strong signal level.
All the RSCP values of the cells are around -80dBm. It means thesignal level is high enough. But all the Ec/Io values are less than -13dB,
it means the signal quality is not good.
In the area several strong pilots coexist and the signal quality is bad. It
is typical pilot pollution.
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Page38Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p From the DT result, it shows the RSCP value is strong, but the
Ec/Io is bad.
p And the signal level of different cell are very similar.
p Find the cells which cover this area
Case 2
We want to find which cells can cover the area with pilot pollution and
try to make a dominant cell in this area.
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Page39Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
Case 2
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
We find that signals from five cells can be detected in the area.
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Page40Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p On the bridge, the signal from different cell can cover this area due
to reflection of the river and no building.
p From DT, following cell cover this area:
n Site 1 cell A
n Site 2 cell C
n Site 3 cell C
n Site 4 cell C
n Site 5 cell C
Case 2
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Page41Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p Need to find the
best cell
p Check the map,
the site 6 is very
near to the
bridge.
Case 2
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
Site 6
To solve pilot pollution, a dominant cell need to be found. From the map
we can see that site 6 is very near to the area and we can try to use this
site to make a dominant cell.
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Page42Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p 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 2
The residence buildings
are much higher than
antenna, which blockthe signal of site 6
But the signal of site 6 is blocked by high buildings, so it can not be
used.
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Page43Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p Then, site 1 cell
A can be the best
cell to cover this
area
Case 2
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
We try site 1 again because it is also very near to the area.
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Page44Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p Then, try to
increase the
signal of site 1
cell A, and
decrease other
cells
p To confirm this,
DT for site 1 cell
A needs to be
done
Case 2
Site 1 Cell A
Site 5 Cell C
Site 2 Cell C Site 3 Cell C
Site 4 Cell C
The solution is to strengthen the signal of site 1 while weaken the signal
from other sites.
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Page45Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Increase the signal of site 1 cell A
n Change the antenna downtilt from 10 to 7
n Increase CPICH Txpower 1.5 dB higher
p Decrease other cell signal # change the antenna downtilt
n From 7 to 10 for site 2 cell C
n From 5 to 8 for Site 3 cell C
n From 9 to 11 for site 4 cell C
n From 9 to 11 for site 5 cell C
Case 2
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Page46Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Confirmation
p After the modification, the DT shows the pilot pollution area as
below
Case 2
No pilot pollution
After the modification we perform drive test again. The result shows the
pilot pollution is cleared.
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Page48Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Summary
p To solve the pilot pollution, the following issues has be considered
n Increase one of the pilots and decrease the others in the same time
n After the adjustment, the DT has to be done at this cluster to confirm
that no new problem appeared
Case 2
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Page50Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p RSCP distribution in DT
Case 3
Bad RSCP
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Page51Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p Ec/Io distribution in DT
Case 3
Problem
area
Problem
areaBad Ec/Io
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Page52Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p Checking the RF environment, the antenna is installed on 10-
meter platform
p 2G and 3G antenna are installed at one platform, but 3G antenna
is a little bit inner than 2G antenna.
p After finishing DT in 2G, signal level is very stable
Case 3
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Page53Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Analysis
p If 3G and 2G antenna are installed at the same place, the problem
may be solved.
Case 3
Problem Area
3G Antenna
2G Antenna
p The short wall of this
platform may block the
signal of 3G
p Since 2G antenna isnear to the border, the
wall influence 2G little
Wall
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Page54Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
l Solution
p Solution 1
n Increase the antenna height can solve this problem
p Solution 2
n Move the installation place near to the border
p Solution 3
n 3G and 2G use the same place
Case 3
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Page55Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 3
l Solution
p Solution 3 is adopted
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Page56Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 3
l Summary
p Sharing the same installation place for 3G and 2G is very
common, and several strategies can solve the problem
p In this situation, 3G and 2G can share the feeder system, or
can only share the installation platform.
p Considering the factors of the installation and related
resource, a easiest and simplest method should be adopted
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Page57Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4l Description
p In DT, call drop happensa lot in the area
Call drops in
this corner
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Page58Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Description
p Check the DT information, SC304 is in active set with the signal
level RSCP -76dBm and Ec/Io -18dB
l Analysis
p Consider the pilot pollution
n But only 1 cell in active set and 1 Cell in monitor set
p Consider the missing neighbor cell
n But the cell in monitor set has very good quality RSCP -65dBm and
Ec/Io -6dB
The drive test result shows that there is one cell in active set. RSCP is -
76dBm and Ec/Io is -18dB. It means the signal level is high but the
quality is bad.Pilot pollution can result in high signal level but bad signal quality but
there is only one cell in active set. So it is not pilot pollution.
In monitor set we can find a cell with good RSCP and Ec/Io. So it is not
neither because of missing neighboring cell.
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Page59Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Analysis
p Check the signaling trace at UE side
Before call drop, UE
sends measurement
report to RNC with 1A
event for cell 298
From the signaling tracing result in UE side we can see that UE sends
measurement report with 1A event for SC298 to network, but it can not
receive active set update from network.
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Page60Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Analysis
p Check the signaling trace at RNC side
RNC sent Active Set Update toUE, but no response. Then, RNC
send release RRC connection
Call Drop
The signaling tracing result in RNC side shows that RNC can receive
measurement report from UE and it sends active set update to UE, but
RNC can not receive response (active set update complete) from UE.So RNC release the connection.
From the signaling tracing result in both sides we can see that RNC
already sent active set update but UE can not receive it.
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Page61Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Analysis
p Based on the DT and signaling trace, this call drop can be
considered as handover failure
p The following figure shows the signaling change at the corner.
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Page62Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Analysis
p 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.
p After UE sent measurement report to RNC, cell 304 has become
very bad when RNC sent active set update.
At the corner Ec/Io of the cell 304 decreases while Ec/Io of the cell 298
increases. So the UE sends measurement report with 1A event to
network.But Ec/Io of the cell 304 decreases so fast. When RNC is sending
active set update, Ec/Io is so bad that UE can not receive the signaling
from cell 304. Finally handover fails and call drop happens.
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Page63Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Adjustment
p Since cell 298 has better coverage at this area, handover can
happen earlier
n Decrease cell 304 coverage performance at this area
# Increase the downtilt from 5 to 9
# Adjust the direction from 0 to 310
n Increase cell 298 coverage performance at this area
# Decrease the downtilt from 5 to 4
# Adjust the direction from 300 to 270
This case shows a typical corner effect. Ec/Io of the source cell
increases too fast while Ec/Io of the target cell decreases too fast, So
UE can not receive active set update from network.The solution method is to move the handover area from the corner to
other place.
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Page64Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Adjustment
p Result after adjustment
Handover
area
Handover
area
Before After
From the result we can see that the handover area is moved to other
place.
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Page65Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Adjustment
p Comparison of Ec/Io of UE
Before After
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Page66Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 4
l Summary
p Confirm the corner effect by analyzing signaling trace at UE
and RNC
p About corner effect, Taking the method make the handover
happen earlier, such as RF optimization
p Other method can also adopted
n Modify 1A event
n Modify CIO (Cell Individual Offset)
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Page67Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Contents
l Typical Problems Analysis in RF optimization
p RF case related to neighbor cell list
p RF case related to bad coverage
p RF case related to interference
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Page69Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Connect to the problem NodeB, and monitor the RTWP
p Cell 62501 RTWP
Curve with red color shows RTWP in main diversity antenna.
Curve with blue color shows RTWP in secondary diversity antenna.
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Page70Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Cell 62502 RTWP
RTWP in main diversity is too high but secondary antenna is normal.
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Page71Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Cell 62503 RTWP
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Page72Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1l Analysis
p The main diversity antenna is interfered seriously
p Can not find any relation between interference and time, and
the interference appears randomly
p Check the neighbor sites, no interference
l Deduction
p Inter-modulation cause the interference, could be
n Inter-modulation caused by bad connectors
n Inter-modulation by GSM
Only main diversity antenna has high RTWP and the interference
appears randomly, it means that the high RTWP is not caused by heavy
traffic.The neighbor sites have no interference, it means the high RTWP is not
caused by outside interference.
So maybe the high RTWP is caused by inter-modulation.
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Page73Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Check the RF environment
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Page74Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Check the RF environment
n No blocking or any reflection due to the glass wall
n The site RF condition is very good
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Page75Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p 2G and 3G share the feeder system
This site is a 2G&3G co-site. So maybe the high RTWP is caused by
2G&3G inter-modulation.
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Page76Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Check 2G frequency planning
n Sector 1 # 538 with hopping frequency 821
# 538 # 1808.6MHz & 821 # 1867MHz
n Sector 2 # 544 with hopping frequency 821
# 544 # 1811.6MHz & 821 # 1867MHz
n Sector 3 # 858 with hopping frequency 821
# 858 # 1874.4MHz & 821 # 1867MHz
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Page77Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Calculate the third order intermodulation
n Cell 1 # 1925.4MHz (2*1867-1808.6)
n Cell 2 # 1922.4MHz (2*1867-1811.6)
n Cell 3 # 1859.6MHz (2*1867-1874.4)
p The frequency used for WCDMA in this NodeBis 1922.4MHz
The third order inter-modulation is most popular in inter-modulation.
From the result we can see that in cell 2 the result of the third order
inter-modulation is the frequency used by this NodeB. So the highRTWP is confirmed to be caused by inter-modulation.
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Page78Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Analysis
p Conclusion
n The third inter-modulation of cell 2 is just in WCDMA uplink band
which is used by the NodeB. So RTWP in cell 2 is high while cell 1
and cell 3 are normal.
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Page79Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Solution
p Change the hopping frequency of GSM
l Confirmation
p Check the RTWP again, the values are normal
We can change the frequency of inter-modulation by changing the
hopping frequency of GSM.
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Page80Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 1
l Summary
p Characteristics of inner system interference
n The RTWP result are not same at the main and diversity antenna
n The amplitude of interference is big, and the difference is more than 10 dB
n High RTWP will appear in a duration, and will not change so frequently
n High RTWP will not show in a certain time each day, but randomly
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Page81Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Description
p 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_MEAN Time(Ashour)CellNameCellIdRNCId
Several sites have high mean RTWP.
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Page82Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Connect to the problem NodeB, and monitor the RTWP
p Take one site as example
Check one NodeB with high RTWP and find that sector C has problem
while other two sectors are normal.
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Page83Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p The main and diversity antenna have the same interference
trend
p The different between main and diversity is less than 10dB
Main diversity antenna and secondary antenna have similar RTWP. So
it is not caused by inter-modulation.
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Page84Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Check the location of the sites with high RTWP
High
Medium
Low
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Page85Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p All the problem cells are in the third sector of the NodeB,
and the direction is to the northwest
p Many cells at this area show high interference, and the cells
with low RTWP are at low place
Only one sector in the NodeBs with problems has high RTWP. All the
sectors with high RTWP face the same direction (northwest).
All the sites with high RTWP are at high location. While the sites at lowlocation are normal.
From these phenomenon we can guess there are outside interference
from northwest.
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Page86Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Analyze the RTWP in the nearly one month, the
interference shows randomly, but if appears, usually one
whole day, or several days
p The interference shows with high traffic, and also with low
traffic. No evidence shows it is related to the traffic
Continue to analyze the phenomenon. The interference is not related to
the traffic.
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Page87Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Maybe the interference comes from outside and the
northwest direction
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Page88Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Use YBT250 to do the interference checking
Use frequency scanner to check outside interference.
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Page89Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p All the test results show the interference comes from the
same direction # to the country A
p But the distance to country A from the test place is around
50Km to 200Km
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Page90Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Frequency analysis
n U Country UMTS frequency
# 1900MHz
n A country GSM frequency
# 1900MHz
U country UMTS and A country GSM use the same bind. So maybe A
country GSM system can cause interference to U country UMTS.
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Page91Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Analysis
p Maybe the interference comes from A country, but looks like
impossible because the distance (50 to 200Km) is beyond the
transmission
p To confirm this problem, use A country cell phone at the area
with high RTWP
p The result shows the phone does receive the A country GSM
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Page92Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Conclusion
p The interference comes from A country GSM
p Even the distance is very far, the area between the border
is covered by a large water area
p Due to reflection the water, the signal can be transmitted
far away
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Page93Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Conclusion
p After known the reason, the following character of this
kind of interference is found
n Related to the weather
# Rain day, no interference
# Cloudy day, less interference
# Sunny day, high interference
n Related to the seasons also
# Problems show at Summer more than Winter
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Page94Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.
Case 2
l Summary
p Characteristics of external interference
n The RTWP result are same at the main and diversity antenna
n The amplitude of interference is small, and the difference is less than 10 dB
n The interference exists at large area, not just one cell, also including neighbor
cells
n The direction of external interference is obvious
n The cell with high antenna is easier to be interferenced
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Summaryl RF optimization
p Neighbor cell list optimization
p Coverage performance optimization
p Interference optimization
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Thank youwww.huawei.com
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