14 wcdma rno rf optimization
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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA RNO
RF Optimization
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Review
This lecture introduces the various stages involved
in optimizing a 3G radio network and focuses
mainly on the RF Optimization phase.
Step-by-step approach for the analysis of drivesurvey data collected by Scanner and test UE is
presented. The analysis is carried out using the
post processing tool.
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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Network Optimization PhasesFlow Chart
New SiteIntegrated
Single Site Verification
RF Optimization
Cluster of SitesReady?
Service Test and
Parameter Optimization
Regular Reference RouteTesting and Stats Analysis
Re-optimizationNeeded?
Y
N
N
Y
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Network Optimization Phases Step 1
Single Site Verification
To verify the functionality of every new site.
Objectives
To ensure there are no faults related to hardware
installation or parameter settings.
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Network Optimization Phases Step 2
RF Optimization
Once most the sites in a given area are integrated and
verified, RF (or Cluster) optimization could begin.
Objectives
To optimize coverage while in the same time keeping
interference and pilot pollution under control over the
target area. This phase also includes the verification and
optimization of the 3G neighbor lists.
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Network Optimization Phases Step 3
Services Testing & Parameters Optimization
To be conducted in areas of good RF conditions in order
to exclude any coverage issues. Such testing does not
need to be performed for each cell but the drive route
must include different clutter types and environments.
Objectives
To assess the performance and identify any need for
specific parameter optimization.
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Network Optimization Phases Step 4
Regular Reference Route Testing & Stats Analysis Constant monitoring and evaluation of the network
performance can be based on drive test as well as traffic
statistic analysis.
Results of the regular analysis may necessitate re-visits
to the RF optimization and/or parameters tuning.
Objectives
To identify any new issues that could arise, for example,
as a result of increase in traffic or changes in the
environment.
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RF Optimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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RF Optimization - Preparation Clutters
RF optimization should be carried out for groups or clusters ofsites rather than on single site basis, because the cells
performance (capacity, coverage and quality) will influence each
other.
Cluster division in a project
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RF Optimization - Preparation Drive Routes
Cluster drive surveys should include the coverage areas of each celland all the major roads and streets as well as any other important
locations.
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RF Optimization - Preparation Tools
DTI, Anritsu or Agilent scanner
Huawei U626, Qualcomm UE, etc
Huawei Genex Assistant or Actix Analyzer
GPS
GARMIN SeriesGPS
DTI Scanner(Built-in GPS)
AnritsuScanner
Trimble SeriesGPS
QualcommTM6250/ 6275
AT CommandSupported
Mobile
HuaweiWCDMA/HSDPA
Data card
*Support WCDMA
1800/1900/2100M
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RF Optimization - TargetsItem Requirements Comments
CPICH RSCP Target - 85 dBm Corresponds to outdoormeasurements.Minimum -95 dBm
CPICH Ec/Io Target -8 dB Applicable for unloaded network.Minimum - 14 dB
Active Set size
(estimated) Target 3 Based on scanner data.
Pilot pollutionMax % < 10 % % of time a cell is seen as a pilot
polluter.Threshold 8 dB Relative to best server when cell
is not in Active Set.UE Tx power Max 95 % For e1a, e1b & e1c
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RF Optimization Flow ChartDrive Test
Identify any RF Issues
Identify candidatecells for changes
Identify nature ofrequired changes
Determine amountof changes
Implement changes
Repeat Drive Test
Finish
N Problem Resolved?
Y
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RF Optimization - Solutions
Antenna down tilt
Antenna azimuth
Antenna location
Antenna height
Antenna type
Site location
New site
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RFOptimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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RF Analysis Approaches Cell Dominance
Cells with no dominance at all
A site was not radiating during the drive survey
Very poor dominance can also be caused by blocking of the
antenna. So a site visit must be made to verify the antenna
clearance.
Cells with either excessive or poor dominance
This could be due to a high site or non-optimum antenna down tilts.
Cells with too large dominance will be causing interference to
adjacent cells resulting in poorer quality and capacity.
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Areas of non-dominance: Areas where there is not a single clear dominant cell and
where the best server changes too frequently.
Result: Excessive number of soft hand off events reducing
the system efficiency and increasing the probability of call
drops.
UE vs. Scanner Best Serving Cells:
Comparison between the UE and scanner SC plots.
Significant differences between the plots may indicate a
missing neighbor or failed soft handoff problem.
RF Analysis Approaches Cell Dominance
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RF Analysis Approaches CellDominance
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RF Analysis Approaches CPICHCoverage
Check areas of poor coverage, suggestion value as
below:
Good: RSCP -85 dBm
Fair: -95 dBm RSCP < -85 dBm
Poor: RSCP < - 95 dBm
Examine the RSCP coverage on per cell bases in order
to highlight any cells that have too large a footprint.
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RF Analysis Approaches CPICHCoverage
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RF Analysis ApproachesInterference
CPICH Ec/Io Plot
Good: Ec/Io -8 dB
Fair: -14 dB Ec/Io < -8 dB
Poor: Ec/Io < - 14 dB
The -8 dB threshold takes into account the expected future interference
increase as a result of increased traffic.
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RF Analysis ApproachesInterference
Because the RSCP Level is POOR,the fundamental cause of low Ec/Io isPOOR COVERAGE
-15.5
-104
-20
-19
-18
-17
-16
-15
-14
Ec/Io RSCP
-120
-115
-110
-105
-100
-95
-90
Whats the
problem?
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RF Analysis ApproachesInterference
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RF Analysis Approaches ULCoverage Uplink Coverage (UE Tx Power)
High UE Tx power means possible poor uplink coverage.
Areas of high Tx power should be compared to the CPICH
pilots to verify if the problem only exists on the uplink.
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RF Analysis Approaches ULCoverage
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RF Analysis Approaches PilotPollution
Definition of Pilot Pollution:
Within a certain margin (which is called ThRSCP_Relative) to the
best server, and all the pilots should be > -100dBm
The pilot number (whose strength > best server strength
ThRSCP_Relative) > ThN (ThN means active set size, normally 3)
Cells which are frequently seen as polluters (e.g. >8% time)
should be marked and investigated.
Pilot Pollution results should be used in conjunction with the
Estimated Active Set Size
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-62
-64 -66 -68 -69
-81
-90
-85
-80
-75
-70
-65
-60
SC1 SC2 SC3 SC4 SC5 SC6
RSC
P(dBm)
Active Set Pilot Pollution
Margin
Not
Pilot Pollution
RF Analysis Approaches PilotPollution
ThRSCP_Relative was set 8 dB here
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RF Analysis Approaches PilotPollution
SC Count % in Pollution Set8 206 12.9%
9 165 10.3%
10 157 9.8%
11 156 9.7%
12 148 9.2%
13 135 8.4%
16 95 5.9%
17 94 5.9%
18 76 4.7%
19 74 4.6%
20 73 4.6%
21 56 3.5%
32 54 3.4%
35 39 2.4%
37 33 2.1%
43 19 1.2%
48 8 0.5%
53 7 0.4%
67 3 0.2%
80 2 0.1%
130 2 0.1%
Should be investigated
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RF Analysis Approaches PilotPollution
Estimated Active Set Size
Another useful measure of pilot pollution is by looking at the
estimated active set based on the scanner data. This plot is
obtained by modeling the network soft handoff parameterswithin Post process tool.
In order to see areas of excessive SHO candidates, the
estimated active set size is allowed to exceed maximum of 3.
This can be done in conjunction with the Pilot pollution
analysis.
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RF Analysis Approaches PilotPollution Estimated Active Set Size Example
na ys s pproac es e g or
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na ys s pproac es e g orList
Neighbor List Verification
The neighbor list could be verified and optimized using the
Neighbor List Verification tool within Actix.
Recommendations for Each Cell:
Retain: This indicates that those neighbors have been
confirmed from the drive survey data.
Add: Missing neighbors
Remove: These neighbors that were not measured but are
in the neighbor list.
Careful consideration is needed prior to removing neighbours
since the Actix results are drive route dependent.
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RF Analysis Approaches Neighbor List Neighbor List Verification
Example
009 576 Retain 018 82 14.2%
Retain 010 46 8.0%
Retain 016 31 5.4%
Retain 032 20 3.5%
Retain 011 18 3.1%
Add 130 17 3.0%
Retain 021 17 3.0%
Retain 008 12 2.1%
Retain 020 6 1.0%
Retain 012 5 0.9%
Retain 017 2 0.3%
Remove 053 0 0.0%
Remove 019 0 0.0%
Remove 034 0 0.0%
Remove 037 0 0.0%
Remove 013 0 0.0%
Remove 051 0 0.0%
70548 Ajman Central 25.41204 55.447
Nbr SCSample
Count%Latitude Longitude
Sample
CountActionSC Cell Site
RF A l i A h SHO
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RF Analysis Approaches SHO UE SHO Performance
The success rates for event 1a, 1b & 1c and canbe obtained from Post process tool
Number of Active Set Updates
Event Count
Event 1a - 328
Event 1b - 306
Event 1c - 64
Number of Active Set Update Completes
Event Count
Event 1a - 326
Event 1b - 305
Event 1c - 62
Soft-Handover Success Rate
Event Rate
Event 1a - 99.4
Event 1b - 99.7
Event 1c - 96.9
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RF Analysis Approaches DropCall
Drop Call Analysis - RF related issues :
Poor coverage (RSCP & Ec/Io)
High interference and hence poor Ec/Io
Poor uplink coverage (insufficient UE Tx power)
Poor dominance (best cell changes too frequently
resulting in too many SHO events)
Pilot pollution (too many cells present)
Missing neighbors
Fast change of RF conditions (e.g. turning a corner)
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RF Analysis Approaches DropCall Drop Call Analysis Example 1
Call Drop
RSCP & Ec/Io degradesBOTH for scanner and UE
Check for Coverage problems
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RF Analysis Approaches DropCall Drop Call Analysis Example 2
Call Drop
Ec/Io (and RSCP) degrades for UE ONLYwhile scanner shows no degradation
UE camp on new cell immediatelyafter drop, and UE did not
measure this cell before Drop
Check the Neighbor
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RF Analysis Approaches DropCall Drop Call Analysis Example 3
Call Drop
Too many and too quick changesof best server
UE to perform measurementsand SHO in time difficultly
PingPong Handover, need toimprove cell dominance
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RFOptimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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Antenna Adjustment Example RSCP Coverage before Adjustment
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Antenna Adjustment Example RSCP Coverage after
Adjustment
A t Adj t t E l
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Antenna Adjustment Example RSCP Distribution
CPICH RSCP Distribution
1.4
4%
20.3
1% 2
9.3
3%
30.2
7%
18.6
5%
0.0
2%
5.4
7%
25.9
8%
31.0
4%
37.4
8%
0.00%
5.00%
10.00%
15.00%
20.00%
25.00%
30.00%
35.00%
40.00%
-105
to-95
-95t
o-85
-85t
o-75
-75t
o-65
>-65
Before Adjustment After Adjustment
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Antenna Adjustment Example Down Tilt from 4 to 6 Result
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Antenna Adjustment Example Down Tilt from 4 to 8 Result
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Course Contents
Chapter 1 Optimization Phases
Chapter 2 RFOptimization Summary
Chapter 3 RF Analysis Approaches
Chapter 4 Antenna Adjustment Example
Chapter 5 Drop Call Analysis Example
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Drop Call Analysis Example Drop Call Distribution
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Drop Call Analysis Example
There are total 5 drop calls in the plot.
The example of drop call 1 is analyzed to show the
process of analysis in the following.
Drop call 1 occurred at an area of frequent change of
best server as shown by the scanner scrambling code
plot
Drop Call Analysis Example
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Drop Call Analysis Example CPICH RSCP and Ec/Io before the Call Drop
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Drop Call Analysis Example
Compare Ec/Io from both scanner and UE at the time of the
drop as shown in Figure. This clearly shows the UE Ec/Io to
drop to < -21 dB while the scanner remained above -11 dB.
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Drop Call Analysis Example Best server before and after the Call Drop
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Drop Call Analysis Example
Comparing the best servers from the UE and the scanner
at the time of drop:
Drop Call 1 (UE vs. scanner best server) shows that for the
scanner and UE SC008 is the best server prior to the drop.However, about 30 seconds before the drop, the scanner
selected SC018 as the best server while the UE continued
to have only SC009 in its active set resulting in the drop call.
Immediately after the drop, the UE camps on SC018.
Drop Call Analysis Example
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Drop Call Analysis Example UE Active Set and Monitor Set Before and After the Call
Drop
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Drop Call Analysis Example
Conclusion
Examining the UE Active and Monitored set, Figure does not
show SC018 to be measured by the UE prior to the drop.
This scenario resembles a missing neighbor problem
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Drop Call Analysis Example Solution:
Looking at drop call Figure clearly shows that at the location
of the drop, SC018 should not be the best server.
Cell SC018 clearly requires some down tilting to control its
interference into the area of Drop 1. To illustrate this,
RSCP coverage of SC018 shows clearly that the cells is
extending into a large area. E.g. around the location of drop
call, SC018 RSCP is > -75dBm.
Add the Missing Neighbors
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