owo300040 wcdma coverage problem analysis issue1.00
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5/20/2018 OWO300040 WCDMA Coverage Problem Analysis ISSUE1.00
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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Coverage
Problem Analysis
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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.
Foreword
The coverage problem is common in WCDMA radio network
optimization. In this course, we will discuss how to find and
resolve the WCDMA coverage problems.
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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Classification Of Coverage Problem
2. Coverage Optimization Flow
3. Case Analysis
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Classification Of Coverage Problem
Weak coverage
Coverage holes
Cross-cell coverage
Pilot pollution
Imbalanced between uplink and downlink
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Weak Coverage
Pilot signal is lower than the minimum access threshold of
UE. For example, RSCP threshold is -115dBm, and Ec/Io
threshold is -18dB
Solution
Adjust antenna for increasing coverage
Use RRU, repeaters or leakage cable
Construct a new NodeB
Use indoor distributed coverage system
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Coverage Holes
Pilot signal is higher than the minimum access level but
lower than the request of the services (voice, video phone
PS64 etc.)
Solution:
Adjust antenna for increasing coverage
Use RRU (Radio Remote Unit), repeater or mini site
Adjust the Max Radio Link power for the services
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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.
Solution
Adjust tilt angel and azimuth of antenna
Avoid antenna propagation directed to the road
Adjust pilot power, and reduce coverage areas of NodeB
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Pilot Pollution
Multiple pilot signals are received in one point, but there is no
primary pilot strong enough
Judgement
There are more than 3 cells
Pilot signal level CPICH_RSCP>-95dBm
(CPICH_RSCP1st- CPICH_RSCP4th)
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Imbalanced between Uplink and Downlink
Uplink coverage is limited:
Transmit power of UE is maximum but cannot meet uplink
BLER requirements
Due to uplink interference
Downlink coverage is limited:
Transmit power of downlink dedicated channel code is
maximum but cannot meet downlink BLER requirements
Due to downlink interference
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Contents
1. Classification Of Coverage Problem
2. Coverage Optimization Flow
3. Case Analysis
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Contents
2. Coverage Optimization Flow
2.1 Optimization Target in Different Stage
2.2 Preparation for Optimization
2.3 Coverage Data Analysis
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In Single Site Verification Stage
Page12
Focus on:
Weak Coverage
Coverage Holes
Check whether the coverage area of cell is consistent with
planning
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In RF Optimization Stage
Page13
Focus on:
Cross-Cell Coverage
Pilot pollution
Check:
Interference:
RTWP in uplink
RSSI measured by Scanner and UE in downlink
Ec/No with and without cell load
RSCP: Whether RSCP is strong enough
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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.
In Parameter Optimization Stage
Page14
Focus on:
Soft Handover Ratio
Too high soft handover ratio results in capacity limitation
Typical soft handover ratio: 30%~40%
Performance KPI
Whether the traffic distribution is consistent with planning
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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved. Page15
Contents
2. Coverage Optimization Flow
2.1 Optimization Target in Different Stage
2.2 Preparation for Optimization
2.3 Coverage Data Analysis
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Preparation
Site Distribution, Site Configuration,Antenna Configuration
Pilot Prediction, Service Distribution
PlanningResult
Drive Test Tool
Performance Management tool
Signaling Analysis ToolAnalysis Tools
CPICH PowerMax FACH Power
Sintrasearch etc.
ConfigurationParameters
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Planning Result
Knowing planning result is important for coverage problem
analysis
Including
Site Distribution
Site Configuration
Antenna Configuration
Pilot Prediction
Service Distribution
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Analysis Tools
Including
Drive Test Tools, such as Genex Probe and Genex Assistant
Performance Management tool, such as iManager PRS
Signaling Analysis Tool, such as LMT
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Configuration Parameters
The radio configuration parameters to be adjusted for
solving coverage problems include
CPICH TX Power
MaxFACHPower
QqualminQrxlevmin
SintrasearchSintersearchSsearchrat
PreambleRetransMax
IntraFILTERCOEFIntraCellIndividualOffset
RLMaxDLPwrRLMinDLPwroriented to service
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Configuration Parameters
PCPICHPower
Parameter name: PCPICH transmit power [0.1dBm]
Recommended value: 330, namely 33dBm
MaxFachPower
Parameter name: Max transmit power of FACH [0.1dB]
Recommended value: 10, namely 1dB
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Configuration Parameters
Qqualmin
Parameter name: Min quality level
Recommended value: -18, namely -18dB
Qrxlevmin
Parameter name: Min Rx level
Recommended value: -58, namely -115dBm
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Configuration Parameters
IdleSintrasearch
Parameter name: Intra-freq cell reselection threshold for idle
mode
Recommended value: 127, namely none
ConnSintrasearch
Parameter name: Intra-freq cell reselection threshold for
connected mode
Recommended value: 127, namely none
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Configuration Parameters
IdleSintersearch
Parameter name: Inter-freq cell reselection threshold for idle
mode
Recommended value: 127, namely none
ConnSintersearch
Parameter name: Inter-freq cell reselection threshold for
connected mode
Recommended value: 127, namely none
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Configuration Parameters
SsearchRat
Parameter name: Inter-RAT cell reselection threshold
Recommended value: 127, namely none
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Configuration Parameters
PowerRampStep
Parameter name: Power increase step
Recommended value: 2, namely 2dB
PreambleRetransMax
Parameter name: Max preamble retransmission
Recommended value: 20
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Configuration Parameters
FilterCoef
Parameter name: Intra-freq meas L3 filter coeff
Recommended value: D3, namely K=3
CIO
Parameter name: Cell oriented Cell Individual Offset
Recommended value: 0, namely 0dB
CIOOffset
Parameter name: Neighboring cell oriented CIO
Recommended value: 0, namely 0dB
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Configuration Parameters
RlMaxDlPwr/RlMinDlPwr
Parameter name: RL Max/Min DL TX power
Page27
ServiceRL Max Downlink Transmit
Power (dB)
RL Min Downlink
Transmit Power (dB)Downlink SF
CS Domain
12.2 kbps AMR -3 -18 128
28 kbps -2 -17 64
32 kbps -2 -17 64
64 kbps 0 -15 32
PS Domain
8 kbps -8 -23 128
32 kbps -4 -19 64
64 kbps -2 -17 32
144 kbps 0 -15 16
256 kbps 2 -13 8
384 kbps 4 -11 8
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Contents
2. Coverage Optimization Flow
2.1 Optimization Target in Different Stage
2.2 Preparation for Optimization
2.3 Coverage Data Analysis
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Coverage Data Analysis
Downlink Coverage
Analysis
RSCP
Dominant Cell
Comparison between UE
and Scanner
DL Tx Power Distribution
Soft Handover Ratio
Page29
Uplink Coverage Analysis
Uplink Interference (RTWP)
UE Tx Power
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Downlink Coverage Analysis
RSCP Analysis
Page30
The RSCP is lower than -95dBm
Coverage
hole
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Downlink Coverage Analysis
Dominant Cell Analysis
Page31
Dominant cell
changes frequently,
No Dominant Cell
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Downlink Coverage Analysis
Comparison between UE and Scanner
Page32
UE
Scanner
Boundary of cells are
shown more clearly by
Scanner than UE
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Downlink Coverage Analysis
DL Tx Power Distribution
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Downlink Coverage Analysis
Soft Handover Ratio
Soft Handover Ratio is defined by Drive Test:
Page34
PointsofNumber
CriterionSHOeSatisfy thwhichPointsofNumberRatioHandoverSoft
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Downlink Coverage Analysis
Soft Handover Ratio
Page35
Number of Points
which are used to get
SHO Ratio
Pilot Pollution
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Uplink Coverage Analysis
RTWP Analysis
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Uplink Coverage Analysis
UE Tx Power
Page37
Red Point shows the
UE Tx Power is higher
than 20dBm
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KPI Analysis
Coverage problem affects:
RRC Setup Successful Rate
RAB Setup Successful Rate
Call Drop Rate
Handover Successful Rate
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Contents
1. Classification Of Coverage Problem
2. Coverage Optimization Flow
3. Case Analysis
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Case 1
From drive test, the RSCP in the blue circle is lower than -90dBm,which means the weak coverage
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Weak
Coverage
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Case 1
The simulation shows that signal in some zones is bad
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Weak
Coverage
If the distance between the
site is low, the RSCP is
more than -80dBm
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Case 1
The distribution of the sites is not density proportional:
Page42
Smallest site
distance: 0.62km
Largest sitedistance: 1.37km
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Case 2
After swap, the uses complain the mobile cannot camp on
3G, and the distance between complaint point and site is
2km
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Case 2
Possible reasons:
Hardware fault
Installation fault, such as high VSWR
Engineering parameter fault
Cell Parameters fault, such as improper PCPICH power
There is no alarm, and VSWR is normal
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Case 2
The site of 3G_Westfort_NGA is built on the mountain, and
the height is 60meter
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3G_Westfort_NGA,
the SC of the 1st
Sector Cell is 138
Drive test result of
SC138
Mountain
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Case 2
The downtilt of Cell SC138 is set as 6 in engineering
parameter table
Check the tilt configuration in NodeB :
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Current Tilt is set as 6,
which means 0.6
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Case 2
Modify the Tilt from 6 to 60, the problem is resolved.
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Case 3
The RRC Setup Success Ratio of the following 2 cells are
around 92%:
Checking the relative counters, most of the RRC failure is
indicated with the counter RRC.FailConnEstab.NoReply
Page48
Cell
ID
VS.RR
C.FailC
onnEstab.Cell
VS.RRC
.AttCon
nEstab.Cell
VS.RRC
.Rej.RL.
Fail
VS.RRC
.Rej.AA
L2.Fail
VS.RRC
.Rej.Po
wer.Cong
VS.RRC
.Rej.UL.
CE.Cong
VS.RRC
.Rej.DL.
CE.Cong
VS.RRC
.Rej.Co
de.Cong
VS.RRC
.Rej.Oth
er.Cong
RRC.Fai
lConnE
stab.NoReply
2242 2025 28361 0 0 0 18 0 0 0 2007
2722 1908 21414 0 0 0 0 0 0 0 1908
Cell RRC Setup Success Ratio
2242 92.86
2722 91.09
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Case 3: Analysis
Usually the counter RRC.FailConnEstab.NoReply is caused bythe weak coverage
Checking the IOS data, the Ec/No of most RRC requests are low.
This is the reason that NoReply from UE for RRC Connection
Setup
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Case 3: Analysis
Checking the states of neighbour cells: some WCDMA cell
are not activated yet, so the UEs located in other cells camp
on the Cell2242 and Cell2722
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Case 3: Solution
Modify the parameters of inter-RAT cell reselection to make
UE easier to reselect to 2G cell:
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Parameters Default Value Modified Value
Qqualmin -18dB -16dBQrxlevmin -115dBm -101dBm
SsearchRat 4dB 2dB
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Case 3: Result
After Modification, the RRC Connection Setup SuccessfulRate improved:
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Summary
In this course, we have discussed coverage relatedproblems:
Classification Of Coverage Problem
Weak coverage
Coverage holes
Cross-cell coverage
Pilot pollution
Imbalanced between uplink and downlink
Coverage Optimization Flow
Case Analysis
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