Training wcdma rf optimization gsm to umts

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential
Internal
www.huawei.com
WCDMA RF Optimization
Process
GSM-to-UMTS Training Series V1.0
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HUAWEI TECHNOLOGIES CO., LTD. HUAWEI
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Page 1
Revision History
Cheng
Fangyuan
The notes on major concepts are
added in P10.
The notes on the optimization
process are added in P9.
The concept of pilot pollution is
added in P36.
“Optimization principles for soft
handover” is added in P41.
1.12009-01-12
Liu Nanchuan
The notes are added in P20 and
P22.1.2
2009-01-20
Gao BoFirst draft is completed.1.02008-12-31
AuthorDescriptionVersionDate

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As a phase in network optimization,
RF optimization is to optimize radio
frequency (RF) signals. RF optimization
can control the pilot pollution and soft
handover ratio in the drive test while
optimizing the signal coverage, thus
ensuring normal distribution of radio
signals before service parameters are
optimized.
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l Upon completion of this course, you
will be able to familiarize yourself with
the following contents:
[Position of RF optimization in the
entire optimization process
[Specific process for RF
optimization
[Troubleshooting for RF
optimization

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References
l W-RF Optimization Guideline
l W-Handover and Call Drop
Optimization Guideline
l W-Interference Processing
Guideline

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Chapter 1 Network Optimization
Process
Chapter 2 Overview of RF
Optimization Process
Chapter 3 RF Troubleshooting
Chapter 4 RF Optimization Cases

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New site access
Single site verification
Cluster of sites ready?
RF optimization
Service test and
parameter optimization
Optimization objectives
reached?
N Y Y
N
Network Optimization Flowchart
Optimization end

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Network Optimization Process
l Single site verification
As the first phase of the optimization, the single site verification is to test the
functions of each new site. The objectives of the single site verification are to
ensure correct site installation and parameter configuration.
l RF optimization
Once the installation and verification of all the sites in the planned area are
complete, RF (or cluster) optimization starts immediately. As one of main
phases in network optimization, RF optimization can control the pilot pollution
and soft handover ratio in the drive test while optimizing the signal coverage,
thus ensuring normal distribution of radio signals before service parameters are
optimized. RF optimization covers the optimization of the hardware of the
antenna system and the list of neighboring cells. When RF optimization is
tested for the first time, all the cells in the area should be traversed as much as
possible to rectify hardware faults.

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Process

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RF Optimization Flowchart
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Objectives of RF Optimization
lRF optimization is to solve the problems such as signal coverage, pilot pollution, and soft
handover ratio in the drive test. In practice, however, carriers have different KPI requirements,
index definitions, and considerations. Therefore, the objectives of RF optimization should be
to meet the requirements of coverage and handover KPIs in contracts (commercial office) or
planning reports (pilot office) and the indexes should be defined according to the
requirements of contracts.
≤5%Pilot pollution ratio
The soft handover ratio in the RF optimization phase
should be 5% to 10% lower than the target value. This is
because the later optimization will cause a rise of soft
handover ratio.
30%-40%Soft handover ratio
Test result from the Scanner, with no service carried
outdoors
≥ 95%CPICH RSCP ≥ -95 dBm
Test result from the Scanner, with no service carried
outdoors
≥ 95%CPICH Ec/Io ≥ -12 dB
Perform test on the acceptance route that should not cover
any area without coverage.
The downlink CPICH Ec/Io of the planned full-coverage
service is greater than or equal to -12 dB and the downlink
CPICH RSCP is greater than or equal to -95 dBm.
≥95%Coverage ratio
Remarks
Reference
Value
Acceptance Item
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Cluster division in a project
Preparations for RF Optimization
lDivide clusters and ensure that all the sites in clusters are working
Considering the characteristics of the UMTS system, for example, the coverage and capacity
affect each other and the frequency reuse factor is 1, RF optimization should be implemented on
the basis of a group of or a cluster of sites instead of a single site. In this way, the interference
from an intra-frequency neighboring cell is also considered in RF optimization. Before adjusting a
site, you must analyze the effect of the adjustment on neighboring sites in detail.

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l Determine the test route
[Before the drive test, you should determine the test route with
the customer. The test route should cover the route predefined
by the customer. If the route predefined by the customer cannot
be covered, you should notify the customer of the information in
time.
[The KPI test route is a core one in the test route of RF
optimization, and its optimization is a core task in RF
optimization. In addition, the test route should also cover main
streets, important places, and VIP/VIC.

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l Test route in a
project

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Arrange for test tools
Before RF optimization, you should arrange for necessary software,
hardware, and documents to ensure smooth test and analysis. The
preparations are listed as follows:
1. Software
Map display and route data
making
Mapinfo4
Performance analysis, health
check, and problem location
Genex Nastar3
DT data analysis and neighboring
cell check
Genex Assistant2
Drive testGenex Probe1
RemarksFunctionNameNo.

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2. Hardware
DC converted to AC, more
than 300 W
Vehicle-mounted
inverter
4
PM1.3G/512M/20G/USB/COM
/PRN
Portable PC3
At least
two test
terminals
U626, Qualcomm, and so on
Test terminal and
data cable
2
DTI ScannerFrequency scanner1
RemarksContentEquipmentNo.

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3. Documents
Used for indoor testYesPlan of floors to be tested7
No
Checklist for single site
verification
6
NoSite survey report5
Yes
Network configuration
parameters
4
YesKPI requirements3
Mapinfo or printed
document
YesMap2
YesEngineering parameter table1
RemarksMandatoryDocumentNo.

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Process

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Chapter 3 RF
Troubleshooting
3.1 Coverage Analysis
3.2 Pilot Pollution
Analysis
3.3 Handover Analysis

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Coverage Analysis
l As a major content in RF optimization, coverage analysis
focuses on signal distribution.
Classification of coverage problems:
l Poor coverage
l Cross coverage
l Uplink and downlink unbalance
l Area without dominant cell

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Poor Coverage
lConcept: The RSCP of pilot signals in the coverage area is smaller than -95
dBm.
lEnvironment: valley, mountainside back, elevator shaft, tunnel, underground
garage, basement, inside of a high building, and so on.
lConsequence: Full-coverage services are difficult to access the network; the
call drops; the UE cannot camp on a cell and even drops from the network due
to failure to initiate location update and location registration requests.
Countermeasures:
lIncrease the pilot power, adjust the azimuth and tilt of the antenna, raise the
antenna, and replace the antenna with an antenna with a higher gain to
optimize the coverage.
lAdd new BTSs or increase the coverage of neighboring BTSs to extend the
overlapped coverage between two BTSs and ensure an appropriate soft
handover area. (Note that co-channel interference and adjacent-channel
interference may be caused after the coverage is increased.)
lAdd new BTSs or RRUs to extend the coverage.
lUse the solutions such as the RRU, indoor distribution system, leaky cable,
and directional antenna.

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Cross Coverage
lConcept: The area covered by a BTS exceeds the planned scope
and discontinuous dominant areas are formed in the areas covered by
other BTSs.
lEnvironment: hills and areas along roads and harbors
lConsequence: handover failure and “island” effect
Countermeasures:
lDo not have the antenna face the road or use surrounding
buildings or other obstacles to decrease the cross coverage.
(Note that co-channel interference with other BTSs may be
caused.)
lFor a BTS that is located at a high place, replace the site
address, adjust the pilot power, or use an RET antenna to
decrease the coverage and eliminate the “island” effect.

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Uplink and Downlink Unbalance
lConcept: In the target coverage area, the uplink coverage of the symmetrical service
is poor (the requirements of the uplink BLER cannot be met even if the transmit power
of the UE reaches a maximum value), or the downlink coverage is poor (the
requirements of the downlink BLER cannot be met even if the code transmit power of
the downlink DCH reaches a maximum value).
lConsequence: The call is easy to drop due to poor uplink coverage.
Countermeasures:
lFor the uplink and downlink unbalance caused by uplink
interference, monitor the RTWP alarm of the BTS to check
whether the interference exists. For details, see the W-
Interference Processing Guideline.
lFor poor uplink coverage, add a TMA.
lFor poor downlink coverage, adjust power settings if the
capacity is sufficient, or replace the power amplifier with a larger
one.

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Area Without Dominant Cell
lConcept: There is no dominant cell or the dominant cell changes
frequently in the area.
lConsequence: Frequent handover occurs; the system efficiency falls; the
call is easy to drop.
Countermeasures:
lFor the area without dominant cell, adjust the tilt and
azimuth of the antenna to increase the coverage of a cell with
good signals (or a near cell) and decrease the coverage of
other cells with poor signals (or far cells).

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Questions
l Summarize the reasons, environments, phenomena, and
countermeasures of coverage problems.
l What factors should be considered in planning to ensure
smooth optimization?

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Process for Coverage Analysis
Downlink coverage analysis
Downlink coverage analysis is to analyze the CPICH RSCP obtained in the drive test. The
quality standard of the CPICH RSCP should be defined on the basis of the optimization
standard. Assume that the optimization standard of the CPICH RSCP is as follows:
The proportion of the CPICH_RSCP greater than or equal to -95 dBm is greater than or
equal to 95%.
According to the test result from the Scanner with no service carried outdoors, the quality
standard is defined as follows:
l Good: CPICH_RSCP ≥ -85 dBm
l Fair: -95 dBm ≤ CPICH_RSCP < -85 dBm
l Poor: CPICH_RSCP < -95 dBm
Analysis methods:
1. Analysis of pilot coverage intensity
2. Analysis of a dominant cell
3. Analysis of the coverage comparison between the UE
and Scanner

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Analysis of Pilot Coverage Intensity
RSCP for 1st Best ServiceCell

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Analysis of a Dominant Cell
l The analysis of a dominant cell is to analyze the cell
scrambling code information obtained in the drive test.
l The contents to be checked are as follows:
1. Cell with poor coverage
2. Cell with cross coverage
3. Area without dominant cell

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Area Without Dominant Cell
SC for the 1st Best ServiceCell

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Analysis of Coverage Comparison Between
the UE and Scanner

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Process for Coverage Analysis
Uplink coverage analysis
Uplink coverage analysis is to analyze the UE Tx Power obtained in the drive test. The quality
standard of the UE Tx Power should be defined on the basis of the optimization standard.
Assume that the optimization standard of the UE Tx Power is as follows:
The proportion of the UE Tx Power smaller than or equal to 10 dBm is greater than or equal to
95%.
Assume that the maximum transmit power of the UE is 21 dBm, according to the test result of the
voice services on the UE, the quality standard is defined as follows:
l Good: UE_Tx_Power ≤ 0 dBm
l Fair: 0 dBm < UE_Tx_Power ≤ 10 dBm
l Poor: UE_Tx_Power > 10 dBm
Analysis methods:
1. Analysis of uplink interference
2. Distribution of uplink transmit powers of the UE

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Distribution of Uplink Transmit Powers of the UE
UE Tx
Power is
too high.

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Chapter 3 RF
Troubleshooting
3.2 Pilot Pollution
Analysis

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Definition and Decision Standard of the Pilot
Pollution
Definition: There are too many strong pilots at a point, but the point lacks a
dominant pilot that is strong enough.
When the following conditions are reached, the pilot pollution occurs at the point:
The number of pilots with CPICH_RSCP greater than ThRSCP_Absolute is greater
than ThN.
(CPICH_RSCP1st - CPICH_RSCP(ThN +1)th) < ThRSCP_Relative
If ThRSCP_Absolute = -100 dBm, ThN = 3, and ThRSCP_Relative = 5 dB,
the decision standard of the pilot pollution is as follows:
l 1. The number of pilots with CPICH_RSCP greater than -100 dBm is greater
than three.
l 2. The difference between the strongest pilot and weakest pilot is smaller than 5
dB.
l When conditions 1 and 2 are both reached, the pilot pollution occurs.

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Causes and Impact
l Causes
[The layout of cells is improper.
[The position of the BTS or the height of the antenna is too
high.
[The azimuth of the antenna is set improperly.
[The tilt of the antenna is set improperly.
[The pilot power is set improperly.
[The coverage area is affected by the environment.

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Causes and Impact
l Impact
When the pilot pollution occurs, the following problems may be
caused:
1. Ec/Io decrease
2. Handover call drop
3. Capacity decrease

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How to Rectify Pilot Pollution
1. Adjust the antenna
2. Adjust the pilot power
3. Use the RRU or micro cell
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Chapter 3 RF
Troubleshooting
3.2 Pilot Pollution
Analysis

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Handover Analysis
In the RF optimization phase, the related handover problems can be
solved through optimizing neighboring cells and controlling the soft
handover ratio. You can control the size and location of a handover
area through adjusting RF parameters to decrease the call drop due
to sharp changes of signals and improve the handover success ratio.
For analysis of other handover problems, see the W-Handover and
Call Drop Optimization Guideline.

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Neighborhood Optimization
The optimization of neighboring cells covers two cases: adding a neighboring cell
and deleting a neighboring cell.
l Missed configuration of a neighboring cell: When a cell with strong signals does
not join the active set, the interference rises and even the call drops.
l Redundant neighboring cell: When there are too many messages of neighboring
cells, signaling overheads are increased greatly and a required neighboring cell
cannot be added when neighboring cells are fully configured.
In the RF optimization phase, the missed configuration of a neighboring cell is a
major consideration. The specific analysis methods are follows:
1. Analysis based on the DT result
2. Analysis based on Scanner data
3. Analysis based on UE data

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Analysis of Soft Handover Ratio
Definition of soft handover ratio
According to the DT data collected on the Scanner, you
can obtain the soft handover ratio. The soft handover
ratio is defined as follows:
Soft handover ratio = Number of points matching handover
conditions collected on the Scanner in the DT / Total
number of points collected on the Scanner in the DT

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Analysis of Soft Handover Ratio
Optimization principles for soft handover:
1. The soft handover ratio in the RF optimization phase should be 5% to 10% lower
than the target KPI value.
2. If the large-scale coverage optimization and pilot pollution adjustment are complete,
and the soft handover ratio approximates to the target value, you do not need to
specially optimize the soft handover ratio and only need to properly adjust related
parameters in the parameter optimization phase.
3. If the soft handover ratio is too large, you should shrink the coverage area to
decrease or change the soft handover area. You should ensure that the
adjustment does not expand the existing area with poor coverage, cause a new
area with poor coverage, or cause more pilot pollutions.

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Process

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Chapter 4 RF Optimization
Cases
4.1 Cases for Coverage
Problems
4.2 Cases for Pilot Pollution
4.3 Cases for Missed
Neighboring Cell
Configuration

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Improper Settings of Engineering Parameters
Cause Poor Coverage
Symptom: Coverage near Xiajiao Sugar Refinery (before optimization)

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Cause Poor Coverage
Analysis
The RSCP of the pilot in the area in a red circle is smaller than -95
dBm, indicating poor coverage. In the area, the call may drop.
As shown in the figure in P44, the area is mainly covered by cell B
of Xiajiao Sugar Refinery and partially covered by cell A of Materials
Building. The first consideration is to adjust the two cells to enhance
the coverage in the area. According to the site survey report, cell A
of Materials Building is facing high buildings. In this case, the
problem cannot be solved through adjusting the antenna in the cell.

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Cause Poor Coverage
lAdjustment measures: Keep the antenna parameters in cell A of Materials
Building unchanged and adjust the antenna azimuth in cell B of Xiajiao Sugar
Refinery from 170° to 165° and the tilt from 10° to 8°.
Coverage near Xiajiao Sugar Refinery (after optimization)

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Improper Site Address Causes Cross
Coverage
Cross coverage before optimization

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Coverage
Analysis
In a pilot office, the height of the site on the Erqi Road exceeds 60 m,
which is about 20 m higher than the average height of its surrounding
buildings. Therefore, the cross coverage is easy to form, which causes
co-channel interference with other sites.
Generally, if a site is located at a high place, you can replace the
antenna with the fixed electrical tilt 2° with an antenna with the fixed
electrical tilt 6°. As the site on the Erqi Road is located on the coverage
edge, you can adjust the azimuth and tilt of the antenna to decrease
the interference with other sites. In this optimization, the preferable
solution to the cross coverage is to increase the mechanical tilt and
adjust the azimuth instead of to replace the antenna.

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Coverage
lAdjustment measures: Increase the tilt to 4°. After the adjustment, the cross
coverage is improved greatly. The cross coverage, however, still occurs in some
areas on the road.
Cross coverage in some areas after optimization

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Improper Antenna Installation Causes Limited Coverage
Limited coverage caused when the antenna is installed without considering platform blocking

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Improper Antenna Installation Causes Limited
Coverage
Analysis
In a project, the antennas of the site are placed on the platform (10 m high), as
shown in the figure in P50. In the optimization phase after network construction,
VP mosaics often increase before the traffic light under the antennas. In this
case, the image quality becomes poor and the PS 384k service is re-activated.
According to the planning, the 3G network and 2G network share a site address.
According to the 2G test data, the signals do not fluctuate greatly at the
intersection and under the site. That is, if the 3G and 2G antennas are located
at the same place, the 3G coverage at the intersection should also come from
the site. Therefore, the causes for the problem are summarized as follows: (1)
The 3G antenna is installed close to the wall of the platform, which blocks the
propagation of signals. (2) The 2G antenna and its installation parts affect the
pattern of the 3G antenna, which makes the radiation pattern of the 3G antenna
vary. According to the installation scenario of the antennas, it is very difficult to
replace the location of the 3G antenna.

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Improper Antenna Installation Causes Limited
Coverage
lAdjustment measures: To avoid affecting 2G coverage, use the following solution with the
minimum changes: Connect the 3G Tx/Rx feeder and 2G Tx/Rx feeder to two ends of the wideband
polarized antenna close to the road, and then connect the 3G Rx feeder and 2G Rx feeder to two
ends of the wideband polarized antenna far from the road, as shown in the following figure.
Feeder optimization

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Cases
Problems
Neighboring Cell
Configuration

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Data Analysis Before Optimization:
1. Find a pilot pollution point
Pilot pollution near the Yuxing Road: cell 270 is designed to cover the area.

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2. Analyze the distribution of cell signals
near the pilot pollution point
Best serving cell near the Yuxing Road
2nd best serving cell near the Yuxing Road

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2. Analyze the distribution of cell signals
near the pilot pollution point
3rd best serving cell near the Yuxing Road 4th best serving cell near the Yuxing Road
Composition of pilot pollution on the Yuxing Road

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3. Analyze the distribution of RSSIs near
the pilot pollution point
RSSIs near the Yuxing Road
RSCPs for the best serving cell
near the Yuxing Road

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4. Analyze the distribution of RSCPs in
related cells
RSCPs in cell 270 near the Yuxing Road

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Data Analysis After Optimization
Pilot pollution near the Yuxing Road
after optimization
Best serving cell near the Yuxing Road
after optimization

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Data Analysis After Optimization
RSCPs for the best serving cell
near the Yuxing Road after optimization
RSCPs for cell 270
near the Yuxing Road after optimization

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Cases
Problems
Neighboring Cell
Configuration

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Missed Neighboring Cell Configuration
Causes Call Drop
lAccording to the measurement result of the active set on the UE, the Ec/Io quality near the
place where the call drops is very poor, and the signal strength of the serving cell is very poor
(continuously lower than -15 dB) before the call drop, and the current serving cell corresponds to
scrambling code 209, as shown in the following figure.
Ec/Io information in the active set measured on the UE before the call drop

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Causes Call Drop
lAccording to the measurement data on the Scanner, the signal measured on the Scanner is always
good at the place where the signal measured on the UE is very poor before the call drop, and the
signal belongs to the cell corresponding to scrambling code 128, as shown in the following figure.
Ec/Io information in the active set measured on the Scanner before the call drop

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Causes Call Drop
Analysis
l As shown in the figures in P62 and P63, the neighboring cell corresponding to scrambling code
128 may not be configured. To confirm the inference, view the message process near the place
where the call drops. Find the latest intra-frequency measurement control message, and then
check whether scrambling code 128 is contained in the list of intra-frequency neighboring cells.
According to the result, scrambling code 128 is not contained in the list of intra-frequency
neighboring cells. Therefore, the call drop is caused by missed neighboring cell configuration.
l If only the UE data is available in the test, you can determine whether a required neighboring cell is
not configured in the following way:
[ Determine the scrambling codes of all the cells in the active set and monitored set measured
on the UE before the call drop.
[ Determine the scrambling code of the cell on which the UE camps after the call drop, and then
compare the scrambling code with the scrambling codes in the active set and monitored set
before the call drop. If the scrambling code is not in the list of scrambling codes in the active
set and monitored set, the call drop may be caused by missed neighboring cell configuration.
[ Check the list of neighboring cells for confirmation.

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Common Adjustment Measures in RF
Optimization
The adjustment measures in the RF optimization phase cover two aspects: list
of neighboring cells and engineering parameters. Most coverage and
interference problems can be solved through adjusting the following
engineering parameters (arranged in descending order by priority):
[ Antenna tilt
[ Antenna azimuth
[ Antenna height
[ Antenna location
[ Antenna type
[ TMA (for example, add a TMA)
[ Site type (for example, change the site supporting a 20 W power amplifier
to the site supporting a 40 W power amplifier)
[ Site location
[ Site or RRU (for example, add a site or an RRU)

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Summary
l RF optimization focuses on improving the distribution of network
signals to provide a good radio environment for subsequent
optimization of service parameters.
l The DT is a main test method in RF optimization and other test
methods serve as a supplement.
l The coverage, pilot pollution, and handover problems are mainly
analyzed in RF optimization, and the analysis of other problems serve
as a supplement. Based on the analysis of the three problems, you can
solve related handover, call drop, access, and interference problems.
l The engineering parameters are mainly adjusted in RF optimization,
and the cell parameters are adjusted in the parameter optimization
phase (except the adjustment of the list of neighboring cells).

Thank You
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Training wcdma rf optimization gsm to umts

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