Download - 08 WCDMA RNO Coverage Problem Analysis
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WCDMA Coverage Problems AnalysisWCDMA Coverage Problems Analysis
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Course ObjectivesCourse Objectives
Analyze problems of pilot coverage and service coverage, and then solve them
Measure the coverage performance of a network
Know coverage enhancement technology
After learning the course, you can:
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ContentsContentsContents
Training.huawei.com
Coverage problems classification
Coverage analysis flow
Coverage enhancement technology
Typical coverage problems analysis
Key items at each stage of network optimization
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Coverage Problems ClassificationCoverage Problems ClassificationCoverage Problems Classification
Signal dead zone
Coverage void
Cross-cell coverage
Pilot pollution
Imbalance of uplink and downlink
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Coverage Problems ClassificationCoverage Problems ClassificationCoverage Problems Classification
Signal dead zone
In the zone, pilot signal is lower than the minimum access
threshold of mobile phone. For example, RSCP threshold is
-115 dBm, and Ec/Io threshold is -18 dB, such as valley,
opposite of the sidehill, elevator well, tunnel, underground
garage or basement, and inside of the high buildings.
Solutions:
Construct a new NodeB
Add coverage areas
Use RRU and repeaters
Use leakage cable and micro cell
Use indoor distributed coverage system
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Coverage Problems ClassificationCoverage Problems Classification
Coverage void
In the area, pilot signal is lower than minimum requirement in
full-coverage areas (such as Voice, VP, PS128K), but better
than the minimum access threshold of mobile phone.
Solutions
Construct micro NodeBs or repeaters
Use high-gain antenna, increase antenna height, reduce the
mechanism tilt angle of antenna
Optimize power configuration of full-coverage services (in scenes
without large capacity requirements
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Coverage Problems ClassificationCoverage Problems Classification
Cross-cell coverage
Coverage areas of some NodeB are beyond the planned range,
and forms pilot areas satisfying full-coverage services in
coverage areas of other NodeBs.
Solutions:
Adjust tilt angel and azimuth of antenna
Avoid antenna propagation directed to the road
Use the shield effect of peripheral buildings
Adjust pilot power, and reduce coverage areas of NodeB
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Coverage Problems ClassificationCoverage Problems ClassificationCoverage Problems Classification
Pilot Pollution
Multiple pilot signals are received in one point, but there is
primary pilot strong enough.
If over three pilots meet and
, there is pilot pollution.
Solutions:
Consider pilot pollution at planning stage to facilitate later network
optimization.
Adjust distribution and antenna parameters
Lower pilot power
Merge NodeB sectors or remove redundancy sectors without
affecting capacity
dBmRSCPCPICH 95_ >
dBRSCPCPICHRSCPCPICH thst 5)__( 41
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Coverage Problems ClassificationCoverage Problems ClassificationCoverage Problems Classification
Imbalance of uplink and downlink
In target coverage areas, uplink coverage is limited (the transmit
power of UE is maximum but cannot meet uplink BLER
requirements), or downlink coverage is limited (the transmit
power of downlink dedicated channel code is maximum but
cannot meet downlink BLER requirements)
Imbalance of uplink and downlink due to uplink interference
Imbalance of uplink and downlink due to limited downlink power
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ContentsContentsContents
Training.huawei.com
Coverage problems classification
Coverage analysis flow
Coverage enhancement technology
Typical coverage problems analysis
Key items at each stage of network optimization
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Coverage Analysis FlowCoverage Analysis FlowCoverage Analysis Flow
Prepared knowledgePrepared knowledge
Coverage data analysis
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Planning SchemesPlanning SchemesPlanning Schemes
Analyzing problems of pilot coverage and service
coverage is based on knowing planning schemes of
target areas. The schemes include:
Site distribution
NodeB configuration
Antenna configuration
Pilot coverage prediction
Service load distribution
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Tools for AnalysisTools for AnalysisTools for Analysis
The analysis of coverage data contains drive test call and
the BAM of pilot census data, traffic measurement of current
network, UL RTWP alarm of each cell, and user call flow
traced by RNC.
Drive test BAM (such as Actix and Genex Assistant)
Traffic measurement tools
UL RTWP alarm system
Testability log
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Configuration Parameters AdjustmentConfiguration Parameters AdjustmentConfiguration Parameters Adjustment
The radio configuration parameters to be adjusted for
solving coverage problems include:
CPICH TX Power
MaxFACHPower
Sintrasearch, Sintersearch, and Ssearchrat
PreambleRetransMax
Intra-FILTERCOEF
Intra-CellIndividalOffset
RLMaxDLPwr and RLMinDLPwr (oriented to services)
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Coverage Analysis FlowCoverage Analysis FlowCoverage Analysis Flow
Prepared knowledgePrepared knowledge
Coverage data analysis
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Coverage Data AnalysisCoverage Data AnalysisCoverage Data Analysis
Analysis of coverage data include:
Analysis of drive test data
Analysis of traffic measurement data
Analysis of tracing data
Analysis of user complaints
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Coverage void
Downlink coverage
1. Analysis of pilot coverage strength
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Downlink coverage
2. Analysis of primary cell
No primary cell
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Difference in soft handover areas
Downlink coverage
3. Comparative analysis of UE and Scanner coverage
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Frequency Accumulation %
Downlink coverage
4. Analysis of downlink code transmit power distribution
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
According to the Scanner drive test data, the soft handover area ratio
is defined as follows:
The soft handover ratio from the perspective of traffic is defined as follows:
Downlink coverage
5. Analysis of soft handover ratio
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Pilot pollution
Downlink coverage
5. Analysis of soft handover ratio
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Uplink coverage
1. Analysis of uplink interference
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Uplink coverage
2. Uplink transmit power distribution of UE (micro cellular)
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Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data
Uplink coverage
2. Uplink transmit power distribution of UE (macro cellular)
Uplink coveragerestricted
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Analysis of Traffic Measurement DataAnalysis of Traffic Measurement DataAnalysis of Traffic Measurement Data
Traffic measurement indexes
The effect on access success ratio, congestion ratio, call drop ratio, and
handover success ratio from the coverage
Traffic distribution
The coverage problem caused by traffic volume measurement and
imbalance of service distribution
Excessive busy cells and idle cells
The effect on the coverage based on the load adjustment
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ContentsContents
Training.huawei.com
Coverage problems classification
Coverage analysis flow
Coverage enhancement technology
Typical coverage problems analysis
Key items at each stage of network optimization
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Coverage Enhancement TechnologyCoverage Enhancement Technology
NodeB configuration adjustment
Sectorized configuration
High-power PA
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Coverage Enhancement TechnologyCoverage Enhancement TechnologyCoverage Enhancement Technology
TMA
Tower mounted amplifier (TMA) improves the uplink coverage
performance by reducing the total noise factor of NodeB receiving
subsystem, and the coverage gain depends on the mechanism of
receiving subsystem and the feeder loss.
When the WCDMA network shares feeders with the GSM system,
the coverage gain is the greatest. If the system capacity is restricted
in downlink, the TMA reduces the system capacity. Typically, the
capacity loss ranges from 6% to 10%.
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Coverage Enhancement TechnologyCoverage Enhancement TechnologyCoverage Enhancement Technology
Transceiver diversity
In the downlink, provided with the time switched transmit diversity
(TSTD) and space time transmit diversity (STTD), you can add the
RAKE receiver number of UE and improve the quality to increase the
coverage range, improve the system capacity and reduce the NodeB
number.
In the uplink, adopting four-antenna receiving diversity decreases the
requirements on Eb/No needed by demodulation. The gain of four-
antenna receiving diversity is 2.5 dB to 3.0 dB. You can improve the
uplink sensitivity by 2.5 dB to 3.0 dB, and reduce the site quantity by
25%-30%.
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Coverage Enhancement TechnologyCoverage Enhancement TechnologyCoverage Enhancement Technology Repeaters
Repeaters expand the coverage range of primary cell. WCDMA
repeaters are similar to analog repeaters, the noise and signal are
amplified at the same time.
The repeater increases the Eb/No required by uplink and downlink
demodulation. Most repeaters do not use uplink receiving diversity
technology. In this way, Eb/No required in uplink demodulation
increases dramatically.
If the system capacity is restricted in uplink, using repeaters leads to
decrease of the system capacity.
If the system capacity is restricted in downlink, the effect on the system
capacity from the repeater depends on:
Link budget between primary NodeB and repeater
Repeater power transmission setup
Maximum path loss related to repeater coverage area
Service allocation between host cell and repeater
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Coverage Enhancement TechnologyCoverage Enhancement TechnologyCoverage Enhancement Technology
Remote RF amplifier
The remote RF amplifier allows physical separation of NodeB RF
module from baseband module so that the RF module is placed far
away without using long feeder.
The uplink and downlink budget improves and RF being remote
means that coverage performance increases but the capacity does
not reduce. Compared with the remote coverage through the RRU,
the TMA adds the maximum path loss and introduces insertion loss
to reduce the EIRP of NodeB.
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Coverage Enhancement TechnologyCoverage Enhancement TechnologyCoverage Enhancement Technology
Micro-cellular
The urban and dense urban areas require high density of NodeB, so the site
selection is difficult. The micro-cellular can meet the high capacity and
applicable for city and dense city.
The feature of micro-cellular solution is that micro-cellular requires Eb/No and
quick fading margin needed in demodulation, increases channel code
orthogonality, but reduces neighbor cell interference and soft handover
margin. When micro-cellular and macro-cellular have the same power, the air
interface volume of micro-cellular is twice of that of macro-cellular.
Indoor coverage
You can perform indoor deep coverage using indoor distributed antennas,
and this proves efficient.
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Coverage Enhancement TechnologyCoverage Enhancement TechnologyCoverage Enhancement Technology
Omni transmission sectorized receive technology
In the Omni Transmission Sectorized Receive technology (OTSR),
signals are transmitted in the omni-direction and received in three
sectors. Because the gain of directional antenna is higher than that of
omni-directional antenna, the coverage radius is farther.
At the earlier stage of network construction when lower capacity is
required, OTSR can reduce the network construction cost and
improve the coverage range.
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ContentsContentsContents
Training.huawei.com
Coverage problems classification
Coverage analysis flow
Coverage enhancement technology
Typical coverage problems analysis
Key items at each stage of network optimization
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Coverage Void Problems Caused by Improper Site Planning
Coverage Void Problems Caused by Coverage Void Problems Caused by Improper Site PlanningImproper Site Planning
Case 1
As shown in this figure, in part of coverage areas, the pilot signal strength is lower than 90 dBm, lower much than that of surrounding areas, so coverage void occurs.
Coverage signal strength < -90 dBm
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Analysis
Coverage signal strength < -90 dBm
Coverage signal strength > -70 dBm
Coverage Void Problems Caused by Improper Site Planning
Coverage Void Problems Caused by Coverage Void Problems Caused by Improper Site PlanningImproper Site Planning
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Coverage Void Problems Caused by Improper Site Planning
Coverage Void Problems Caused by Coverage Void Problems Caused by Improper Site PlanningImproper Site Planning
Irregular mesh structure causes coverage void
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Cross-cell Coverage Problems caused by Improper Site Selection
CrossCross--cell Coverage Problems caused by cell Coverage Problems caused by Improper Site SelectionImproper Site Selection
Case 2
If a site is over high, cross-cell coverage occurs easily, so intra-frequency interference to other sites occurs.
Red indicates cross-cell
coverage areasby the
first sector of Road 27 Site
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Cross-cell Coverage Problems caused by Improper Site Selection
CrossCross--cell Coverage Problems caused by cell Coverage Problems caused by Improper Site SelectionImproper Site Selection
Solution
Increase mechanism tilt angle and adjust direction angle to solve
cross-cell coverage problems for high sites.
Red indicates
Part cross-cell
coverage areas
in Wenhua Rd.
by the first sector
of Rd. 27 Site
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Coverage Restriction Problems Caused by Improper Installation of Antennas
Coverage Restriction Problems Caused by Coverage Restriction Problems Caused by Improper Installation of AntennasImproper Installation of Antennas
Case 3
The Pilot Network: 701070_ParkLaneHotel site of S project covers the
Victoria Park and the antenna is mounted on the platform (10 meters high), as shown in this picture. At the optimization phase after the network
construction, before the traffic light under the antenna, Video Phone mosaic
adds and image quality is worse and PS 384K service is reactivated.
New 3G antenna
Call drop occurs easily
by traffic lights
Existing 2G antenna
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Coverage Restriction Problems Caused by Improper Installation of Antennas
Coverage Restriction Problems Caused by Coverage Restriction Problems Caused by Improper Installation of AntennasImproper Installation of Antennas
Analysis
From the perspective of planning, 3G network and 2G network co-locate.
Compared with 2G coverage test data, 2G network has not large signal fluctuation under the road and site, that is, if the antennas of 3G network
and 2G network are in the same location, the roads 3G coverage is
performed by 701070_ParkLaneHotel_Podium site. The problem lie in than
3G antenna is so close to the platform that the wall blocks the signal and installation conditions of antenna are not met.
Meanwhile, 2G antenna and installation components affect the 3G antenna
pattern.
Solution Change least without affecting the 2G coverage, connect the transceiver
feeders of 3G and 2G respectively with two ports of external broad frequency polarization antenna, and connect other transceiver feeders of 3G
and 2G with two antennas of internal broad frequency antennas.
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Coverage Restriction Problems Caused by Incorrect Installation of Antennas
Coverage Restriction Problems Caused by Coverage Restriction Problems Caused by Incorrect Installation of AntennasIncorrect Installation of Antennas
Case 4
In the Pilot network of S project, 701640_ElzHse1 site has only one cell
and combines transmitter A, B and C (It is not OTSR, but the
combination of three antenna receiving signals and distribution of
NodeB transmission signal).
During the antenna installation at the NodeB construction phase, all the
transmission feeders are combined to sector A by mistake, so sector B
and C have no signals to transmit and the coverage effect is worse. The
problem is found after RF engineers test RTWP interference at the site.
Before the problem is found, the single site test is passed. The problem
even remains in the later network optimization test until RF engineers
identifies it during testing RTWP interference.
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Coverage Restriction Problems Caused by Incorrect Installation of Antennas
Coverage Restriction Problems Caused by Coverage Restriction Problems Caused by Incorrect Installation of AntennasIncorrect Installation of Antennas
The figure shows the comparison of pilot RSCP before and after the antenna installation correction.
After antenna is corrected
Before antenna is corrected
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Coverage Restriction Problems Caused by Incorrect Installation of Antennas
Coverage Restriction Problems Caused by Coverage Restriction Problems Caused by IncorrectIncorrect Installation of AntennasInstallation of Antennas
Analysis The pilot RSCP before the antenna correction in the previous figure
shows that the signals close to the bottom of the site are below -76 dBm. Comparing the coverage of three sectors, obviously, you can find that the coverage of sector A is 20 dB stronger than that of sector B and sector C. From the perspective of current single site test Checklist, it is difficult to find the pilot RSCP is larger than -85 dBm, especially for the micro-cellular site.
Most sites of S project share 2G sites location or sector. Therefore, use the 2G coverage distribution to check whether the 3G coverage isnormal.For example, compare the distribution area ranging from -90 dBm to -80 dBm. Currently, the minimum work level of 2G network is about -60 dBm, and only when the minimum working level at the bottom of 3Gsites also should reach about -60 dBm, the sites are basically normal.
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ContentsContents
Training.huawei.com
Coverage problems classification
Coverage analysis flow
Coverage enhancement technology
Typical coverage problems analysis
Key items at each stage of network optimization
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Single Site Test StageSingle Site Test StageSingle Site Test Stage
Signal dead zone
Concern the major coverage target of each transmitter and
confirm whether the signal dead zone is present based on the
specified target.
Coverage void
Concern whether the continuous coverage of full-coverage
service can be guaranteed.
Planning verification
Concern the difference between the digital map and actual
environment, and perform a comparison and verification
between the coverage prediction and actual drive test data.
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Evaluation Stage before OptimizationEvaluation Stage before OptimizationEvaluation Stage before Optimization
Uplink and downlink interference
Concern the change of uplink RTWP of each cell, Scanner in
the drive test or RSSI of UE.
Ec/Io mean
Under the unloaded downlink and loaded downlink, concern
whether the areas less than the mean value affects continuous
coverage of full-coverage service
RSCP mean
Concern whether areas with the mean value affect seamless
coverage of full coverage service.
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RF Optimization StageRF Optimization StageRF Optimization Stage
Cross-cell coverage
Concern the repeated coverage due to inconsistent height of
sites.
Pilot pollution
Concern whether the ping-pong handover exists in the soft
handover area to reduce the intra-frequency interference.
Over large areas of soft handover
Concern volume restriction due to over large areas of soft
handover.
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Network Optimization Project Acceptance StageNetwork Optimization Project Acceptance StageNetwork Optimization Project Acceptance Stage
Traffic measurement indexes
Concern the inconsistency between the specified coverage
target and actual user traffic distribution.
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SummarySummarySummary
The network optimization can improve quality of the
whole network used by the mobile users and use
network resources more effectively. Although the
coverage indexes are not reflected in the KPI, the
coverage optimization is the basic requirement for
improving the network performance. The radio
performance optimization can take effect only based
on the coverage optimization.
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Thank you!