08 Wcdma Rno Coverage Problem Analysis.pdf

08 WCDMA RNO Coverage Problem Analysis WCDMA Coverage Problems AnalysisWCDMA Coverage Problems Analysis Course ObjectivesCourse Objectives � Analyze problems of pilot coverage and service coverage, an[.]

WCDMA Coverage Problems Analysis

Course Objectives

Analyze problems of pilot coverage

and service coverage, and then solve

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Coverage problems classification

Coverage analysis flow

Coverage enhancement technology Typical coverage problems analysis Key items at each stage of network optimization

Coverage Problems Classification

Signal dead zone

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

 Use indoor distributed coverage system

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

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 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

dB RSCP

CPICH RSCP

( 1 − 4 <

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

 Imbalance of uplink and downlink due to limited downlink power

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Coverage problems classification

Coverage analysis flow

Coverage enhancement technology Typical coverage problems analysis Key items at each stage of network optimization

Coverage Analysis Flow

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

 Service load distribution

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

 Testability log

Configuration Parameters Adjustment

The radio configuration parameters to be adjusted for solving coverage problems include:

Coverage Analysis Flow

Coverage 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 Data

Coverage void

Downlink coverage

1 Analysis of pilot coverage strength

Analysis of Drive Test Data

Downlink coverage

2 Analysis of primary cell

No primary cell

Analysis of Drive Test Data

Difference in soft handover areas

Downlink coverage

3 Comparative analysis of UE and Scanner coverage

Analysis of Drive Test Data

Frequency Accumulation %

Downlink coverage

4 Analysis of downlink code transmit power distribution

Analysis of Drive Test Data

According to the Scanner drive test data, the soft handover area ratio

Analysis of Drive Test Data

Pilot pollution

Downlink coverage

5. Analysis of soft handover ratio

Analysis of Drive Test Data

Uplink coverage

1 Analysis of uplink interference

Analysis of Drive Test Data

Uplink coverage

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

Analysis of Drive Test Data

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

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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Coverage problems classification Coverage analysis flow

Coverage enhancement technology

Typical coverage problems analysis Key items at each stage of network optimization

Coverage Enhancement Technology

NodeB configuration adjustment

 Sectorized configuration

 High-power PA

Coverage Enhancement Technology

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, thecapacity loss ranges from 6% to 10%

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 theRAKE receiver number of UE and improve the quality to increase the coverage range, improve the system capacity and reduce the NodeBnumber

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

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 downlinkdemodulation Most repeaters do not use uplink receiving diversity technology In this way, Eb/No required in uplink demodulation

 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 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

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

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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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

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

Improper Site Planning

Coverage Void Problems Caused by

Improper Site Planning

Coverage Void Problems Caused by

Improper Site Planning

Irregular mesh structure causes coverage void

Cross-cell Coverage Problems caused by

Improper Site Selection

Cross-cell Coverage Problems caused by

Improper Site Selection

by the first sector

of Road 27 Site

Cross-cell Coverage Problems caused by

Improper Site Selection

Cross-cell Coverage Problems caused by

Improper Site Selection

Coverage Restriction Problems Caused by

Improper Installation of Antennas

Coverage Restriction Problems Caused by

Improper Installation of Antennas

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

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

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

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

Coverage Restriction Problems Caused by

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.

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

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

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

Traffic measurement indexes

Concern the inconsistency between the specified coverage target and actual user traffic distribution

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