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WCDMA Coverage Problems Analysis WCDMA Coverage Problems Analysis
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08 WCDMA RNO Coverage Problem Analysis

Nov 16, 2015

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08 WCDMA RNO Coverage Problem Analysis
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  • WCDMA Coverage Problems AnalysisWCDMA Coverage Problems Analysis

  • 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:

  • 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

  • Coverage Problems ClassificationCoverage Problems ClassificationCoverage Problems Classification

    Signal dead zone

    Coverage void

    Cross-cell coverage

    Pilot pollution

    Imbalance of uplink and downlink

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • Coverage Analysis FlowCoverage Analysis FlowCoverage Analysis Flow

    Prepared knowledgePrepared knowledge

    Coverage data analysis

  • 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

  • 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

  • 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)

  • Coverage Analysis FlowCoverage Analysis FlowCoverage Analysis Flow

    Prepared knowledgePrepared knowledge

    Coverage data analysis

  • 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

  • Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data

    Coverage void

    Downlink coverage

    1. Analysis of pilot coverage strength

  • Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data

    Downlink coverage

    2. Analysis of primary cell

    No primary cell

  • 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

  • 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

  • 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

  • Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data

    Pilot pollution

    Downlink coverage

    5. Analysis of soft handover ratio

  • Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data

    Uplink coverage

    1. Analysis of uplink interference

  • Analysis of Drive Test DataAnalysis of Drive Test DataAnalysis of Drive Test Data

    Uplink coverage

    2. Uplink transmit power distribution of UE (micro cellular)

  • 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

  • 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

  • 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

  • Coverage Enhancement TechnologyCoverage Enhancement Technology

    NodeB configuration adjustment

    Sectorized configuration

    High-power PA

  • 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%.

  • 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%.

  • 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

  • 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.

  • 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.

  • 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.

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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.

  • 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.

  • 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

  • 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.

  • 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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • Thank you!