Table Of ContentUlrich Türke
Efficient Methods for WCDMA Radio Network Planning
and Optimization
TEUBNER RESEARCH
Advanced Studies Mobile Research Center Bremen
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Ulrich Türke
Efficient Methods for
WCDMA Radio Network
Planning and Optimization
TEUBNER RESEARCH
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Dissertation Universität Bremen, 2007
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Preface
WhenjoiningSiemensin2001,Ialsoextendedmyresearchinteresttowardsradionet-
workplanningmethodologies.Thisareaofresearchbroughttogethermypersonalinterest
inmobilecommunicationsandinthedesignofefficientalgorithmsanddatastructures.
Between2001and2003,IparticipatedintheEUprojectMomentum,whichwastarget-
ingtheperformanceevaluationandoptimizationofUMTSradionetworks.Inthisproject
mymainfocuswasonMonte-Carlosnapshottechniques,shortlyafterIbroadenedmy
researchscopetowardsnetworkoptimizationtechniques.Bothconstitutethebasisofthis
thesis.LaterIgotthechancetobringintheideasandmethodsofmythesisintoaSiemens
internalplanningandoptimizationtool,thedevelopmentofwhichIguidedoverthelast
twoyears.
FirstofallIwouldliketothankProfessorDr.CarmelitaGörgforsupervisingthisthesis,
forherguidance,andherencouragement.Iverymuchappreciatethatshe-althoughI,
asanexternalPh.D.student,wasnotpartofherdepartmentattheUniversityofBremen
-wasalwaysveryopenfordiscussionsandprovidedmewithalargeamountofuseful
suggestionsoverthepastyears.Iwithoutadoubtgreatlybenefitedfromthis,bothinmy
scientificworkandpersonally.Iamalsodeeplygratefulforthecommentsandsuggestions
by Professor Dr. Thomas Kürner, who is also the second examiner of this thesis. The
discussionswithhimandhisadvice-inparticularinthelastphaseoftheworkonthis
thesis-wereofgreathelptome.IamdeeplyobligedtoHelmutMühlbauerforgivingme
thechancetoconductthisthesiswithinSiemens,forhisstrongfaithinmeandmywork,
andforstrengtheningmyviewoneconomicalaspectsandthepracticalrelevanceofmy
research.FurthermoreIamverygratefultoProfessorDr.RanjitPerera,whoparticipated
asaguestscientistintheEUprojectMomentum.Iverymuchappreciatedthelongand
fruitful discussions with him - not only on technical topics. Special thanks go to my
colleaguesMichaelKoonertandRichardSchelbformanydiscussions,andnotleastfor
proof-readingpartsofthisthesis.
UlrichTürke
Abstract
Theplanningofmobileradionetworksrequiresfastandaccuratemethodsfornetwork
performance evaluation. In this thesis novel methods for the performance analysis of
WCDMAnetworksaredevelopedanddiscussed.
Thestate-of-the-artapproachforevaluatingtheperformanceofWCDMAnetworksisthe
Monte-Carlosnapshotsimulation. However,currentsolutionsbasedonsnapshotsimu-
lationshavemajorweaknesseswithrespecttoaccuracy,simulationtime,andflexibility.
Inparticularthesizeofnetworksthatcanbeanalyzedinanacceptabletimeframewith
standardhardwareresourcesistypicallyverylimited.
Thenewsnapshotanalysismethoddevelopedinthisthesissignificantlyoutperformsthe
state-of-the-artmethods.Itallowsforadetailedanalysisofverylargenetworks(Nx1000
basestationsites)onastandardPCwithinrunningtimesacceptableforeverydayplan-
ning.Thisismainlyachievedbyahighlylinearmodelingofthesystemandbyareduction
ofthesizeofthesetsoflinearequationstobecalculatedineachsnapshot.Thedimension
reductionisachievedbytheapplicationofacellbasedtransmissionpowerandinterfer-
ence level calculation as opposed to the standard mobile based approach. Despite the
significantspeed-upachievedintheevaluationofasnapshot,theproposedapproachalso
allowsaveryaccurateandflexiblemodelingofsystemfeatures,e.g.withrespecttoRadio
ResourceManagement(RRM)andQualityofService(QoS).
Increasingtheperformanceofevaluatingasinglesnapshotisonlyoneapproachtoreduce
therunningtimeofthesnapshotanalysis. Besidesthis,alsothenumberofsnapshotsre-
quiredtoyieldacertainaccuracyofresultscanbereducedbymeansofvariancereduction
techniques. Intheareaofsnapshotsimulationsfornetworkplanning,variancereduction
techniqueshavealmostnotbeenconsideredyet.Inthisthesisconsiderableefforthasbeen
putintoevaluatingtheapplicabilityofvariancereductiontechniquesforcuttingdownthe
runningtimeofthesnapshotanalysis. Basedonthediscussionofseveralvariancere-
ductiontechniquesknownfromtheory,twovariancereductiontechniquesareidentified
andtailoredtoanapplicationineverydayplanning.Both,controlvariatesandcorrelated
sampling,areappliedtoexampleplanningscenarios. Considerablegainswithrespectto
thenumberofrequiredsnapshotstoyieldacertainaccuracyofresultsareobtainedfor
theproposedvariancereductionmethods.
viii Abstract
Whileprovidingveryaccurateresultsatahighlevelofdetail,forsomeapplicationsthe
snapshot simulation approach is too time consuming. In particular search based opti-
mizationtechniques,whichcomparealargenumberofdifferentnetworkconfigurations,
requiremethodswithmuchshorterrunningtimes,whileacceptingalossinlevelofdetail
andaccuracy. Targetingsuchareastheanalyticalmethodsdevelopedinthisthesiscan
beeffectivelyapplied. Basedonastaticmethodtwonovelextendedstatisticalmethods,
incorporatingshadowfadingstatistics,areproposed. Resultsarepresentedshowingsig-
nificantimprovementsinapproximatingtheresultsfromsnapshotsimulationsintermsof
relevantsystemparameters.Finally,theapplicationofthedevelopedmethodsinnetwork
optimizationisdiscussed. Twodifferentoptimizationmethodsaredeveloped. Thepre-
sentedresultsprovethevalueofthemethodsforanapplicationinnetworkoptimization.
Themajorityofthedevelopedmethodsiscurrentlysuccessfullyappliedinaradionet-
workplanningtool.
Contents
ListofAbbreviations xiii
ListofSymbols xvii
ListofFigures xxi
ListofTables xxv
1 Introduction 1
2 TheWCDMAAirInterface 5
2.1 UMTSNetworkArchitecture . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 UTRA-FDDProtocols . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.1 PhysicalLayer . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 DataLinkLayer . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.3 NetworkLayer . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.4 HighSpeedPacketAccessExtensions . . . . . . . . . . . . . . . 17
2.3 RadioResourceManagement . . . . . . . . . . . . . . . . . . . . . . . . 19
2.3.1 SoftHandover . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3.2 PowerControl . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.3.3 AdmissionControl . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3.4 CongestionControl . . . . . . . . . . . . . . . . . . . . . . . . . 23
3 ModelingtheWirelessTransmissionChannel 25
3.1 MacroPathLossPrediction. . . . . . . . . . . . . . . . . . . . . . . . . 26
3.1.1 BasicPropagationModels . . . . . . . . . . . . . . . . . . . . . 26
3.1.2 EmpiricalPredictionModels . . . . . . . . . . . . . . . . . . . . 28
3.1.3 ImprovedModels . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.2 ShadowFading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.2.1 ModelingofSpatialCorrelation . . . . . . . . . . . . . . . . . . 32
3.2.2 ModelingofLinkCorrelation . . . . . . . . . . . . . . . . . . . 33
3.2.3 ImplementationinSimulations . . . . . . . . . . . . . . . . . . . 34
3.3 FastFading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.4 AntennaModeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.5 SignalandInterferenceLevels . . . . . . . . . . . . . . . . . . . . . . . 39
x Contents
3.5.1 EffectiveInterferenceRaise . . . . . . . . . . . . . . . . . . . . 42
3.5.2 PowerControlHeadroom . . . . . . . . . . . . . . . . . . . . . 43
3.5.3 Soft-HandoverGain . . . . . . . . . . . . . . . . . . . . . . . . 43
4 Monte-CarloSnapshotAnalysis 45
4.1 TheMonte-CarloMethod . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.1.1 GeneralConcept . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.1.2 ConvergenceEstimation . . . . . . . . . . . . . . . . . . . . . . 47
4.2 SimpleAnalysisExample. . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.3 VarianceReductionTechniques. . . . . . . . . . . . . . . . . . . . . . . 55
4.3.1 ImportanceSampling . . . . . . . . . . . . . . . . . . . . . . . . 56
4.3.2 StratifiedSampling . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.3.3 ControlVariates . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.3.4 CorrelatedSampling . . . . . . . . . . . . . . . . . . . . . . . . 63
4.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5 SnapshotAnalysisforWCDMANetworkPerformanceEvaluation 67
5.1 BasicAnalysisLoop . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.2 SnapshotGeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.3 ModelingofDynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.4 SystemConstraintsandLimits . . . . . . . . . . . . . . . . . . . . . . . 71
5.5 CellBasedRadioPerformanceEvaluation . . . . . . . . . . . . . . . . . 73
5.5.1 UplinkEquations . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.5.2 DownlinkEquations . . . . . . . . . . . . . . . . . . . . . . . . 77
5.5.3 SoftHandover . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.5.4 IterativeSolution . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.6 ResourceScheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.6.1 QoSConcept . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.6.2 AnalysisAlgorithm. . . . . . . . . . . . . . . . . . . . . . . . . 83
5.6.3 ApplicationExample . . . . . . . . . . . . . . . . . . . . . . . 89
5.7 MethodExtensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.7.1 MultiCarrierAnalysis . . . . . . . . . . . . . . . . . . . . . . . 92
5.7.2 HSPAAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.8 ApplicationofVarianceReductionTechniques . . . . . . . . . . . . . . 93
5.8.1 ControlVariates . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.8.2 CorrelatedSampling . . . . . . . . . . . . . . . . . . . . . . . . 102
5.9 ValidationofResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
5.9.1 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6 AnalyticalPerformanceEvaluation 107
6.1 StaticLoadEstimation . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.1.1 AverageRequiredLinkPower . . . . . . . . . . . . . . . . . . . 108
Contents xi
6.1.2 CellAssignment . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.1.3 ServingProbability . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.1.4 CoverageProbability . . . . . . . . . . . . . . . . . . . . . . . . 111
6.1.5 CharacteristicCellPowerEquations . . . . . . . . . . . . . . . . 111
6.1.6 ApplicationExample:StaticLoadEstimation . . . . . . . . . . . 113
6.2 StatisticalLoadEstimation . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.2.1 ServingProbabilities . . . . . . . . . . . . . . . . . . . . . . . . 116
6.2.2 CoverageProbability . . . . . . . . . . . . . . . . . . . . . . . . 117
6.2.3 CharacteristicCellPowerEquations . . . . . . . . . . . . . . . . 118
6.2.4 ApplicationExample:StatisticalLoadEstimation . . . . . . . . . 119
6.3 ExtendedStatisticalLoadEstimation. . . . . . . . . . . . . . . . . . . . 120
6.3.1 AverageRequiredLinkPower . . . . . . . . . . . . . . . . . . . 120
6.3.2 CharacteristicCellPowerEquations . . . . . . . . . . . . . . . . 125
6.3.3 Application:ExtendedStatisticalLoadEstimation . . . . . . . . 126
6.4 EvaluationofPerPixelQuantities . . . . . . . . . . . . . . . . . . . . . 127
6.4.1 PilotRSCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
6.4.2 Soft-HandoverProbability . . . . . . . . . . . . . . . . . . . . . 130
6.4.3 PilotQuality . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.4.4 DownlinkConnectionPower . . . . . . . . . . . . . . . . . . . . 133
6.4.5 UplinkConnectionPower . . . . . . . . . . . . . . . . . . . . . 135
6.5 PracticalImplementation . . . . . . . . . . . . . . . . . . . . . . . . . . 135
6.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
7 AutomatedNetworkOptimization 137
7.1 OptimizationParametersandTargets . . . . . . . . . . . . . . . . . . . . 137
7.2 OptimizationbasedonFastHeuristic . . . . . . . . . . . . . . . . . . . 138
7.3 SearchBasedOptimization . . . . . . . . . . . . . . . . . . . . . . . . . 142
7.3.1 ABriefIntroductiontoLocalSearch. . . . . . . . . . . . . . . . 142
7.3.2 ApplicationofLocalSearchtoRadioNetworkPlanning . . . . . 145
7.3.3 AdvancedSearchAlgorithm . . . . . . . . . . . . . . . . . . . . 147
7.4 ApplicationExample . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
7.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
8 ConclusionsandOutlook 155
A GeneratingCorrelatedRandomVariables 157
Bibliography 159
