WCDMA Coverage Problems Analysis
Course Objectives
Course Objectives
Analyze problems of pilot coverage
and service coverage, and then solve
them
Measure the coverage performance of
a network
Know coverage enhancement
technology
Contents
Contents
Contents
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 Classification
Coverage Problems Classification
Coverage Problems Classification
Signal dead zone
Coverage void
Cross-cell coverage
Pilot pollution
Coverage Problems Classification
Coverage Problems Classification
Coverage 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
Coverage Problems Classification
Coverage 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 Classification
Coverage 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
Coverage Problems Classification
Coverage Problems Classification
Coverage 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 dBm RSCP CPICH_ >−95 dB RSCP CPICH RSCP CPICH _ st _ th) 5 ( 1 − 4 <
Coverage Problems Classification
Coverage Problems Classification
Coverage 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
Contents
Contents
Contents
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 Flow
Coverage Analysis Flow
Coverage Analysis Flow
Prepared knowledge
Prepared knowledge
Coverage data analysis
Planning Schemes
Planning Schemes
Planning 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
Tools for Analysis
Tools for Analysis
Tools 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
Configuration Parameters Adjustment
Configuration Parameters Adjustment
Configuration 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
Coverage Analysis Flow
Coverage Analysis Flow
Coverage Analysis Flow
Prepared knowledge
Prepared knowledge
Coverage data analysis
Coverage Data Analysis
Coverage Data Analysis
Coverage Data Analysis
Analysis of coverage data include:
Analysis of drive test data
Analysis of traffic measurement data
Analysis of tracing data
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Coverage void
Downlink coverage
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Downlink coverage
2. Analysis of primary cellAnalysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Difference in soft handover areas
Downlink coverage
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Frequency Accumulation %
Downlink coverage
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis 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
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Pilot pollution
Downlink coverage
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Uplink coverage
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
Uplink coverage
Analysis of Drive Test Data
Analysis of Drive Test Data
Analysis of Drive Test Data
上行覆盖受限 上行覆盖受限 上行覆盖受限 上行覆盖受限
Uplink coverage
2. Uplink transmit power distribution of UE (macro cellular)
Uplink coverage restricted
Analysis of Traffic Measurement Data
Analysis of Traffic Measurement Data
Analysis 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
Contents
Contents
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 Technology
Coverage Enhancement Technology
NodeB configuration adjustment
Sectorized configuration
Coverage Enhancement Technology
Coverage Enhancement Technology
Coverage 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 Technology
Coverage Enhancement Technology
Coverage 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 Technology
Coverage Enhancement Technology
Coverage 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
Coverage Enhancement Technology
Coverage Enhancement Technology
Coverage 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 Technology
Coverage Enhancement Technology
Coverage 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 Technology
Coverage Enhancement Technology
Coverage 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.
Contents
Contents
Contents
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 Planning
Improper 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 Planning
Improper Site Planning
Coverage Void Problems Caused by
Improper Site Planning
Coverage Void Problems Caused by
Coverage Void Problems Caused by
Improper Site Planning
Improper Site Planning
Cross-cell Coverage Problems caused by
Improper Site Selection
Cross
Cross
-
-
cell Coverage Problems caused by
cell Coverage Problems caused by
Improper Site Selection
Improper 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 areas by the first sector of Road 27 Site
Cross-cell Coverage Problems caused by
Improper Site Selection
Cross
Cross
-
-
cell Coverage Problems caused by
cell Coverage Problems caused by
Improper Site Selection
Improper 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
Coverage Restriction Problems Caused by
Improper Installation of Antennas
Coverage Restriction Problems Caused by
Coverage Restriction Problems Caused by
Improper Installation of Antennas
Improper 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 Antennas
Improper 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 road’s 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 Antennas
Incorrect 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 Antennas
Incorrect 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
Incorrect
Incorrect
Installation of Antennas
Installation 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 is normal.
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 3G sites also should reach about -60 dBm, the sites are basically normal.
Contents
Contents
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 Stage
Single Site Test Stage
Single 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 Optimization
Evaluation Stage before Optimization
Evaluation 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 Stage
RF Optimization Stage
RF 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 Stage
Network Optimization Project Acceptance Stage
Network Optimization Project Acceptance Stage
Traffic measurement indexes
Concern the inconsistency between the specified coverage target and actual user traffic distribution.