Network Validation for CDMA 2000 1X EV-DO …...9- Testing and analysis of IMT-2000 networks in the countries visited with hardware and software tools. Network Validation for CDMA

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NetworkValidationforCDMA20001XEV-DOTechnologyTechnicalHandbookReport

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InaccordancetotherequirementsoftheRequestforEngineering,wecarriedout

severalinformationandasksinPanama,China,Sweden,USA,Norway,Finland,Korea

andTaiwan.Theselocationsarehometoequipmentsuppliers,networkoperatorsor

productregionalrepresentatives.

Thetasksoutlinedforcomplianceweredefinedas:

1-Revision,testing,analysisandrecommendationofinitialterminalequipmentfor

useinthelocalIMT-2000network.Compilationofaccurateonthefield

informationontroublesomeequipment.

2-SecureavailabilityofterminalequipmenttosynchronizewiththenewIMT-2000

platform.

3-Interpretationandrecommendationofaproductreleaseinformationlistingthat

willbeabletointeractwiththemajorityofavailableterminals,particularlylow-

endsupplies,withoutaffectingGoS/QoS.

4-Cellulartestsandmeasurements.Performdatathroughputtestswithterminals

inworkingIMT-2000networks.SensitivityandPerformancemeasurements.

5-Revision,testing,analysisandrecommendationoftestingequipmenttobeused

forengineeringpurposesintheIMT-2000networkatterminallevel(level1,2,3)

andnetworklevel.

6-Conductlaboratorytestingandmeasurementsonnetworkequipment(including

antennas)andterminals.

7-PurchasingofsparepartsofkeycomponentsoftheIMT-2000network.

8-Pursuingadequatetrainingrelevanttothetechnologyandvendorforknow-how

transfertonetworkoperator.

7

9-TestingandanalysisofIMT-2000networksinthecountriesvisitedwithhardware

andsoftwaretools.


7

InmeetingswithmanufacturersofIMT-2000terminalswereheld,modelcompatibility

wasobservedandtechnicaltrainingreceivedbythemanufacturersofequipment.The

trainingincludedRFandprogrammingmattersoneachofthemanufacturer’splatforms

anddevices.Thistrainingwasconductedinlaboratoriesandonthefieldoncurrently

existingEricssonplatforms.Also,worksessionswithworldwidemobileterminals

manufacturerswereheldtoestablishthenetworkparameters.Thesenetwork

parametersincluded:

-NetworkdefinitionsforPRI,

-RFconfiguration,

-PRL,

-ERIdefinitions,

-NVRdefinitions,

-WAPdefinitions,

-andfunctionalitydescriptionofterminalstobereplicatedinthenetwork.

ExtensivetrainingandanalysisofexistingnetworksrunningEricssonCDMA1XEVDO

platformswasconductedtoreplicatethescenariosinthelocalnetwork.Sessionswith

networkengineerswereheldtogatherinformationregardingshortcomingsoftheir

networkswiththeintentiontoavoidtheseinthelocalnetworkimplementation.Specific

problemsinthelocalnetworkwerereviewedwithmanufacturerswiththeobjectiveof

8

correctingthem.Theseallowedtheteamtohavethelatestknow-howandbeableto

transferittothelocalnetworkoperator,whichisanoperatorresponsibility.

SoftwareinterfaceswerealsoanalyzedandbasicprogrammingtrainingonPSTfor

eachdevicewasconducted.

Withtestingequipmenttoberecommendedforpurchase,visitedIMT-2000networks

weretestedandanalyzedinordertoreplicateimplementationlocally.Network

problems,throughput,performance,latency,congestion,etc.wereobserved.

Koreademandedmostoftheresources,astwomajormanufacturersarelocatedinthis

country,andmanyothershaveassemblyplantstoo.Whilenoticeable,network

correlationtolocalimplementationwasnotexact(duetodifferentfrequencyallocations),

terminaltestingwasmandatory.

Alsotestedweremicrowavelinks,antennas,repeaters,filters,combiners,etc.askey

componentstotheIMT-2000networkunderdevelopmentfromimportantsuppliers

aroundtheworld,inordertopurchasespareequipmentforredundancymattersinthe

network.


8

Theinformationcollected,trainingreceived,equipment,spareparts,software,

hardwareandknow-howhasbeenforwardedtothelocaloperator,whichshouldbe

invaluablefortheoperatorśgrowthandcustomersatisfaction.Theobjectives

describedintheRFEweresuccessfullyachievedandexposedaccordinglyinaPFE.


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9

TableofContents

Introduction................................................................................................11

Objectives..................................................................................................12

Summary....................................................................................................13

ProjectOverview........................................................................................17

AbbreviationsandAcronyms.....................................................................18

DataGathering...........................................................................................20

NetworkAffiliation......................................................................................21

TerminalClients.........................................................................................22

ClientperOperator....................................................................................23

Technology................................................................................................24

FrequencyChannelAllocation...................................................................25

Workpackage1.........................................................................................25

Workpackage2.........................................................................................25

DataPerformance......................................................................................28

TestedandMethodology...........................................................................30

ExperimentalMethodology........................................................................32

BenchmarkingPerformance......................................................................33

PerformanceOptimizations........................................................................33

ApplicationLevelTechniques....................................................................34

SessionlayerTechniques..........................................................................37

TransportlayerTechniques.......................................................................39

LinklayerTechniques.................................................................................41

SummaryofResults...................................................................................43

Discussion..................................................................................................44

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RelatedWork..............................................................................................48

DigitalRevolutionandEvolution................................................................50

CDMA2000TakestheNextStep..............................................................51

ANetworkStructureDesignedforPacketizedCommunication................51

TheRadioAccessNetwork(RAN).............................................................52

TheCoreNetwork’sRoleintheCDMAInfrastructure................................53

ThePDSNdoesthefollowingactivities:....................................................53

TheAAAServer..........................................................................................54

TheHomeAgent........................................................................................54

DetectingandSolvingSomeCommonProblemsincdma20001X

Networks....................................................................................................54

ThroughputOptimization...........................................................................58

ThroughputOptimization...........................................................................60

NumericalResults......................................................................................62

CALCULATIONS........................................................................................64

RESULTS....................................................................................................65

CONCLUSIONS.........................................................................................66

REFERENCES............................................................................................70

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11

13

IntroductionTheprocessofmeasuringperformanceofnetworksin

productionandcomparethemagainstthefocus

infrastructureisknownas“networkvalidation”.Because

efficientuseofresourcesisakeydesignproblemforany

cellularnetwork,ingeneral,andcodedivisionmultiple

access(CDMA)networks,inparticular,wherethenumber

ofsimultaneouscallsthatcanbeadmittedinonecell

dependsonthenumberofsimultaneouscallsinmany

cellsinthenetwork,networkvalidationbecomesamust

performprocess.

Thefocusinfrastructureisusuallyaneworrecently

implementednetwork.Networkvalidationisnecessaryto

matchnetworkplanningandconfigurationto“sturdy”(or

immune)networks.Thesenetworksaregradeofservice

provenandinproduction.Theknow-howtransferredin

thisprocessisoneofthesinglemostimportantfactorsfor

networkfinetune-upandusedasaparametertovalidate

thenetworkdesignandimplementationbasedonthe

comparisonofperformanceagainstothernetworks.


12

Objectives

Theobjectivesofthisprojectweretogatherinformation,

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performtests,takemeasurements,runsimulations,

performaccuratebenchmarkofapplicationperformance

over

such

commercially

deployed

environments,

implementandcharacterizetheimpactofvarious

optimizationtechniquesacrossdifferentlayersofthe

protocolstack,quantifytheirinterdependenciesunder

realisticscenarios,issueresultsinproductionnetworksin

ordertovalidatetheimplementationofthelocalnetwork

asrequestedintheRFEdocumentation.Theresultsand

analysisconcludedinthisreportsaretobeusedfor

validationofthelocalnetwork.Thisreportdoesnot

comprehendthelocalnetworkvalidation,butprovidesthe

toolstoperformthistask.Theproductionnetworksin

considerationarelocatedindifferentcountriesthathave

embracedtheCDMA20001XEV-DOtechnology.

Oneofourgoalsistoobtainparameterstomaximizethe

throughputinthenetworkandprovideconsistentgrade-

of-service(GoS),i.e.,thecallblockingrate,forallthecells

inthenetworkwhileatthesametimemaintainingthe

quality-of-service(QoS),i.e.,theprobabilityoflossof

communicationquality,foralltheusers.

15


13

Summary

Toprovideafirmvalidationfoundationforthetechnical

andcommercialmeasuresthatwouldplayacriticalrolein

theoperationofthethird-generation–“3G”–network,

runningunderCDMA20001XEV-DO.

Itwasanticipatedthatthiswouldbeinthecontextof

comparisonwithERICSSONplatforms,butsincehas

judgedfundamentaltocomparetheERICSSON

technologywiththatoneofothersuppliersasamainissue

inthenetworkvalidation,greatcarehasbeentakento

considerthismatter.Bytakingthisopportunity,thework

playsavitalroleinsettingcriticalcomponentsofthe

network.

Thecloseassociationwithmajorkeyplayersinthe

industryattheoperatorlevelandimplementerlevel,and

theunbiasedpositionofthefirmtowardsanysupplier,isa

keymajoradvantage,particularlyimportantsinceitis

likelythatglobalinfluencecanaccidentallybiasmost

consultingfirms.

Thetasksperformedwererelatedtotheprocessof

validationofthenetworkinstallationforphaseIIperRFE.

ThevalidationprocesswasperformedinChina,Chile,

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USAandCanada.

EricssonIMT-2000,NortelNetworks,Lucent,Huawei,

Daxian,Samsung,LGandMotorolaoperatingplatforms

wereanalyzedinparticularwithemphasisonEricsson

platforms.

Ingeneralterms,theteamhadthepurposeofvalidating

networkimplementationbyconsideringseveralfactorslike:

•frequencyplanning,

•trunknetworkplanning,

•timeframe,

•propagation,

•channelcapacity,


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•noiseperformance,

•interference(frequencyreuse,co-channel,adjacent

channel,fromothersystems),

•intermodulation,

•blocking,

•BScontrolandsignaling,

•gradeofservice(GoS)inothernetworks

forlatercomparisontothelocalinstallationwiththe

intentionof:

-applyingcorrectionswherenecessary,

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-improvingnetworkefficiency,

-maximizeinvestmentusage.

Atproductionnetworklocations,thefollowingprocesses

wereconducted(notexclusive):

1-

AnalysisofPNsdistributionandgeneral

distributionofnoiseinthecarrierwave.

2-

EvaluationoftheGoSoftheaccesschanneland

GoSofthevoicechannelasasoleparameter.

3-

FERmeasurements.

4-

Handoffs,HardHand-offparameterswherethere

ismorethanonecarrierwave.

5-

Analysisofcallsdropped,on-netcompletedcalls,

off-netcompletedcalls,completionrate,

6-

RBSlocationanalysis,RFengineering,signal

strengthmeasurements,fadepathway

7-

Channelallocation,spectrumusage,channel

congestion.

InlocationswhereEricssonwasnotthetechnology

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supplier,benchmarkanalysiswithotherplatformswas

performed,morespecificallywithNortelNetworks

platformsinstalledonthosenetworks.Theperformance


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obtainedfromthesenetworkswereusedtovalidatethe

EricssonIMT-2000behavior.

Alsoanalyzedwerecellularbillingsystem,fraud(roaming

fraudwasparticularlyobserved)andfingerprinting

techniquesusedinthosenetworks.

TheinteractionwiththeSwitch/BSCwasobserved,

calibrationoftestequipmentconductedandalso

personnelperformancetomatchagainsttheservicelevels

reportedlocally.

Theprocessofvalidationdidrequiretravelingthrough

entirenetworkscoveragearea,performingmeasurements

includingparticularlytroublesomelocations.Theresults

weretoconcludeontheresultsonthefirstlistingofthis

document.

Systembalance,Loadbalance,interconnection,power

distributionsystems,protection,grounding,switchingat

alllevels(includinghierarchy),roamingservices,contents,

authentication,signalingandsynchronizationfactorswere

observedforvalidationofthelocalnetwork.Infrastructure

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likeframes,masts,poles,andcivilworkswerealso

observed.

Inconclusion,thedivisionperformedthesetasksinorder

tocomplywiththeRFE.Asaresult,aPFEinbeing

developed.

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ProjectOverview

Wirelesscellularnetworksarebeingupgradedworld-widetosupport2.5Gand3G

mobiledataservices.Forexample,CDMA2000andUMTSnetworksinEurope,and

CDMA1xRTTandCDMA2000networksintheUSAandAsiaarecurrentlybeing

deployedandtestedtoprovidewirelessdataservicesthatenableubiquitousmobile

accesstoIP-basedapplications.

CDMA20001xEV-DO(1XEvolutionData-Only)wirelesstechnologyintroducesanew

airinterfacewithapeakdatarateof2.4Mbpsandanaveragethroughputofabout600

Kbpsontheforwardlinkprovidingoperatorswithuptothreetimesmoredatacapacity

thancurrentCDMA20001Xnetworks.1xEV-DOisoptimizedforthebursty,high-speed,

broadbandaccesscharacteristicsoftheInternetdatamodel.Enhancementstothe

1xEV-DOstandard,referredasRevisionA,increasedataspeeds,reducelatencyand

provideQoSmechanismsmakingthestandardviableforrealtimeapplicationssuchas

VoIP.Alltheseconsiderationsweretakenintodecidingwhichnetworkstoanalyzefor

performance.SinceourcostumerwilloperateasanEV-DOenvironment,greatcare

wastakenintoobservingthedataprogressinCDMAnetworks.

Measurementstakeninthenetworksofwell-knowncarriersimpliedattimesagreements

withthosecarriersbutalso60%ofthenetworksanalyzedweredonewithoutsigning

anyagreement.Thiswasdonetomakerandommeasurementsofwell-knownoperators

andobservealltheproblemsandconstraintstheirnetworkshavewithoutbeingdirected

bythecarrieritselftowardstheirtroublelessinstallationsonly.

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Inmattersofourresults,itwasmeasuredthatnetworkssuchasVerizonWireless,MTC

MobilityandSprintPCSoccupyafirsttierinqualityperformance.AllTel,Western

Wireless,USCellular,MetroPCShaveminorproblems.

OurresultsalsoindicatedthatSmartcomPCS,Leap,ChinaUnicomhadatthetime

measurementswereperformedproblemswithnetworkthroughput.

Theresultsobtainedarevalidtobeusedfornetworkvalidation.


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AbbreviationsandAcronyms

AAA

Authentication,Authorization,andAccounting

AAL5

ATMAdaptationLayerType5

ANSI-41

AmericanNationalStandardInstitute

ATM

AsynchronousTransferMode

BSC

BaseStationController

BSS

BaseStationSub-system

BSSAP

BSSApplicationPart

BTS

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BaseTransmissionSystem

CDMA

Code-DivisionMultipleAccess

DHCP

DynamicHostConfigurationProtocol

DSC

DataSwitchingCenter

FA

ForeignAgent

FR

FrameRelay

FW

FireWall

GOS

GradeOfService

GRE

GenericRoutingEncapsulation

HA

HomeAgent

HDLC

High-levelDataLinkControl

HLR

HomeLocationRegister

IKE

InternetKeyExchange

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IOS4.0

Inter-operabilitySpecificationVersion4.0,alsoseeIS2001

IP

InternetProtocol

IPv4

IPVersion4

IPv6

IPVersion6

IPsec

IPSecurity

IS2001

InterimStandard2001:DefinesProtocolsforA1,A7,A9,A11-

InterfacesforCDMA

IS-41e

InterimStandard41:DefinesProtocolsforD-InterfaceforCDMA

IS-95

InterimStandard95:DefinesProtocolsforU-InterfaceforCDMA

IWF

Inter-WorkingFunction

LAC

LinkAccessControl

M3UA

MTP3UserAdaptation

MAC

MediumAccessControl

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MAP

MobileApplicationPart

MIP

MobileIP

MMSC

ShortMessageSwitchingCenter

MS

MobileStation

MSC

MobileSwitchingCenter

MSS

MobileServiceSubscriber

MTP-Adapt

MessageTransferPartAdapter

P.S0001

SpecificationforWirelessIPbasedprotocols

PCF

PacketControlFunction

PDSN

PacketDataServingNode

PL

PhysicalLayer

PPP

Point-to-PointProtocol

PSTN

26

PublicSwitchedTelephoneNetwork


19

RADIUS

RemoteAuthenticationDialInUserService

RAN

RadioAccessNetwork

SCCP

SignalingConnectionControlPart11

SCMG

SCCPManagement

SCTP

SCCPTransportProtocol

SMS

ShortMessageService

SS7

SignalingSystemNo.7

SSSAR

ServiceSpecificSegmentationandReassemblySub-layer

TCAP

TransactionCapabilitiesApplicationPart

TCP

TransmissionControlProtocol

UDP

27

UserDatagramProtocol

VLR

VisitorLocationRegister

1xRTT

1xchiprateof1.2288McpsforRadioTransmissionTechnology

1xRTTEV-DO

1xRTTEvolution-DataOnly

3xRTT

3xchiprateof1.2288McpsforRadioTransmissionTechnology

2G

2ndGenerationofMobiletelecommunication

2.5G

“2.5”GenerationofMobiletelecommunication

3G

3rdGenerationofMobiletelecommunication

3GPP

3rdGenerationPartnershipProject

3GPP2

3rdGenerationPartnershipProject2

AMPS

AdvancedMobilePhoneSystem

ARIB

TheAssociationofRadioIndustriesandBusinesses(Japan)

CDMA-HDR

CDMAHighDataRate

28

CDMA-MC

CDMAMultiCarrier

cdmaOne

CDMAfor2G

EDGE

EnhancedDataratesforGSMEvolution

ECDMA2000

CDMA2000forEDGE

FDD

FrequencyDivisionDuplex

GPRS

GeneralPacketRadioSystem

GSM

GlobalSystemforMobileCommunication

HSCSD

HighSpeedCircuitSwitchedData

IMT2000

InternationalMobileTelecommunicationsforthe2000s

IS136

InterimStandard136:DefinesProtocolsforTDMA(AMPS)

IS136B-HS

IS136BHighSpeed

IS-634b

InterimStandard634b:DefinesProtocolsforA-Interfacefor

CDMAone

29

PDC

PersonalDigitalCellular(Japan)

TDMA

TimeDivisionMultipleAccess

TIA

TelecommunicationsIndustryAssociation

UMTS

UniversalMobileTelecommunication/TelephoneSystem

UWC136

UniversalWirelessCommunicationsforIS136

W-CDMA

Wide-bandCDMA

CC

CallControl

MM

MobileManagement

P-H

PDSNtoHomeAgentInterface

R-P

RANtoPDSNInterface

SDU

SignalDataUnit

U

AirinterfacebetweenMSandBTS

NetworkValidationforCDMA20001XEV-DOTechnologyTechnicalHandbook

30

Report

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DataGathering

Datagatheringorminingfromnetworkmeasurementswasperformedasfollows:

Country

Locations

Operator

Notes

Santiago

Chile

Concepción

SmartComPCS

Valparaíso

ViñadelMar

Durham,WilmingtonNC.

Comscape

Phoenix,AZ.

Leap

Phoenix,AZ.

Alltel

Denver,CO.

Leap

NewYorkCity,NY.

Verizon

U.S.A.

31

NewYorkCity,NY.

SprintPCS

St.Louis,MO.

Verizon

Atlanta,GA.

MetroPCS

Atlanta,GA.

SprintPCS

LosÁngeles,CA.

SprintPCS

LosAngeles,CA.

WesternCellular

Stillwater,OK.

USCellular

Miami,FL.

SprintPCS

Miami,FL.

Verizon

FortLauderdale,FL.

MetroPCS

PortCharlotte-FortMyers,FL.

MetroPCS

WestPalmBeach,FL.

MetroPCS

Athens,GA

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MetroPCS

Monterrey-Salinas,CA.

MetroPCS

Altona

Bonnet

Grandview

Canadá

Morris

MTSMobility

Polonia

Rusell

Steinbach

Woodside

AnHui

Beijing

Henan

Henan

China

Jiangsu

ChinaUnicom

Liaoning

Shanghai

Sichuan

Yunnan


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Report

21

Table1-NetworksinProductionmeasured

NetworkAffiliation

Thefollowingserviceprovidersweremeasured:

Operator

Country

USCellular

UnitedStates

MetroPCS

UnitedStates

SprintPCS

UnitedStates

MTSMobility

Canada

SmartComPCS

Chile

ChinaUnicom

China

Comscape

UnitedStates

Leap

UnitedStates

VerizonWireless

UnitedStates

34

Table2-NetworkAffiliation


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TerminalClients

Thefollowingclientswereusedtoperformourmeasurementsandtesting.

Client

Model

Notes

Kyocera

2255

DataCapable,SMS

DataCapable,BREW2.0,

Kyocera

KE413/KX414Phamton

SMS

Kyocera

2235

DataCapable,SMS

Kyocera

S14

DataCapable,SMS

Audiovox

CDM8300

DataCapable,SMS,WAP

35

Audiovox

CDM9155

DataCapable,SMS,WAP

DataCapable,SMS,Push

Sanyo

PM-8200

ToTalk,MMS,WAP

Sanyo

SCP-8100

DataCapable,SMS,WAP

Data

Capable,

JAVA

Motorola

V720

enabled

Data

Capable,

BREW,

Motorola

T730

gpsOne

Samsung

SCH-N255

DataCapable,SMS

36

Data

Capable,

BREW,

Samsung

SCH-A610

gpsOne,SMS,MMS

DataCapable,gpsOne,

Samsung

SCH-A310

SMS

Data

Capable,

BREW,

LG

VX-4400

gpsOne,WAP2.0,SMS

Data

Capable,

BREW,

LG

VX-6000

gpsOne,WAP2.0,MMS,

SMS

Nokia

2270

37

SMS

Table3-ClientsDevices


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ClientperOperator

Client

Model

Operator

Kyocera

2255

Leap,ChinaUnicom

Kyocera

KE413/KX414Phamton

Leap

Kyocera

2235

SmartcomPCS

Kyocera

S14

MetroPCS,Leap

Audiovox

CDM-8300

Comscape

Audiovox

38

CDM-9155

AllTel

Sanyo

PM-8200

SprintPCS

Sanyo

SCP-8100

SprintPCS

Motorola

T730

MTS

Samsung

SCH-N255

WesternCellular

Samsung

SCH-A610

ChinaUnicom

Samsung

SCH-A310

VerizonWireless

LG

VX-4400

USCellular

LG

VX-6000

39

VerizonWireless

Smartcom

PCS,

Metro

Nokia

2270

PCS

Table4-Clientsusedatnetworks


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Technology

Protocol

Networks

Notes

IS-95A

Nonetested

-

IS-95B

Nonetested

-

All

networks

had

developedintoEV-DO.

40

IMT-2000

Nonealone

Someweredeveloping

intoEV-DV

MostnetworkswereEV-

IMT-20001XEV-DO

Some

DOenabled

AlthoughtherewereEV-

DVnetworksinoperation

IMT-20001XEV-DV

Nonetested

intheUS,didnottest

these.

Table5-TechnologyProtocols


25

FrequencyChannelAllocation

Frequency

Carrier

800

Verizon,SPRINTPCS,ChinaUnicom,

Smartcom,AllTel,Commnet

1800

41

Verizon,WesternWireless,Commnet

SPRINTPCS,ChinaUnicom,SmartCom

1900

PCS,Verizon,USCellular,MetroPCS,

Leap,MTSMobility,AllTel

2100

ChinaUnicom

Table6-FrequencyChannelAllocation

Workpackage1

Therentaloracquisitionofsophisticatedequipmentwasconsideredinorderto

measurethenetworksparameters.Itwasconsideredthatthekeytoolsto:

a)MeasureRFparameters

b)MeasureandTestsCallsperformance

ocallscompleted

ocallsdropped

ocallsfailed

ojitter

oecho

ointerference

onoise

c)PhaseNoise

Workpackage2

Extensivemeasurementspreparationswerealsoobservedfor:

a)MBS

b)MSC

42

c)BSC

d)BTS

e)BSS


26

f)SMSC

g)DSC

h)MSS

i)RAN

Forthesetasks,itwasestablishedthattheitemsonTable7-Measurement

Equipmentfortestingwerenecessary.

ItemNo.

Equipment

Model/System

Options/Notes

PortableSpectrumAgilentE443APSA

Withoptions226(Phase

LE1290

Analyzer

Noise

Measurement),

option

B78

(CDMA

43

2000),option204(1xEV-

DOMeasurement).

LE1315

TestDriveSet

E7477ACdma2000Supportfor850MHz,1.8

Network

DriveSystem

GHz

and

1.9

GHz,

Optimization

AgilentE6474A

1XRTT/SR1

Platform

Option

E6474A-740

(WAMS)

AllowstestingofMMS,

SMS,Video,WAP,HTTP,

FTP

LE1337

Wireless

BaseE7495A/B

OptionCDMA2000Tx

44

StationTestSet

CDMAovertheairtest

tool

NortelCDMAtestSW

PowerMeter

Interferenceanalysis

LE1501

LaptopComputer

Toshiba

SatelliteSerialports,CDRW,LAN

Centrino

Softwareincludin:

EDXPCSAnalyzer

LE1601

Software

Specializedsoftware

MarconiPlanet

MapInfo

IntegratedAnalyzerfor

LE1702

AnalizadorCDMA

NetTekAnalyzer

CDMA

Table7-MeasurementEquipmentfortesting

•ItemLE1290PortableSpectrumAnalyzer

45


27

Thisitem,theportablespectrumanalyzerAgilentE443APSAwiththeoptiontomeasure

phasenoise,andIMT-2000with1xEV-DOextension.Thisistheheartofthe

measurementconfigurationandthesinglemostpowerfultooltomeasurespectrum

usage.OurpreferenceforAgilentagainstotherbrandsreviewed(especiallyAndo)was

basedsolelyinacost-benefitanalysis.

•ItemLE1315CDMATestDriveSet

TheTestDriveSetisaspecializedtoolthatallowsengineerstoliterallydrivearoundthe

networkcoverage.ItallowstheengineerstoobtainRFcoverage,serviceperformance

anddatatestmeasurementsforwirelesscommunicationsnetworksthatusethe

advancedCDMA2000technology.ThesystemrunsonalaptopPCthatinterfaceswith

anAgilentdigitalreceiverand/oraCDMA2000mobilephone.Thesystemcancontrol

uptofourreceiversandfourphonessimultaneously.Thedrivetestsystemisaplatform

productwhichprovidesthefollowingfeatures:carry-aroundtesting,indoortesting,real-

timemappingaswellasmeasurementscapabilitiesinothertechnologiessuchasIS-

95,CDMA,TDMAandCDMA-2000.

TheengineeringteamchoseAgilentbecausethisisthebesttestdrivetoolinthemarket

forCDMA2000networks.

•ItemLE1337WirelessBaseStationSet

46

Thebasestationtestsetisthemostfunctionalone-boxtoolforwirelessandwireline

testavailabletoday,eliminatingtheneedfortechnicianstocarry,manage,andlearn

multipletesttools.Consolidatingthemostusedfrequentlyusedtoolsintoonebox

dramaticallyincreasesthetechnicianśproductivity.Thishelpsreducetheassetcosts,

trackingcosts,calibrationandmaintenancecosts,andtrainingcostsassociatedwith

learningthespecificsofseparateinstruments.

ItsupportsCDMAOneandCDMA2000Txanalysis.Itcontainsanantennatester(to

includeoneportandtwoportinsertionloss,returnloss,anddistancetofault

measurements),spectrumanalyzer,internalGPSreceiver,andasetofaccessories

(cables,attenuators,opens,shorts,etc.).

Theoptionincluded:

-PowerMeter

-CWandCDMAreverselinksignalgenerator

-CDMAovertheairtesttool

-NEMspecifictestsoftware(NortelCDMAtestSW)

-12VoltDCBiasOutput


28

-Interferenceanalysis

•ItemLE1501LaptopComputer

ToshibaSatellitewithserialportsrunningWindowsOSandToshibaSatelliterunning

Linux.BothmachineswerepoweredbyIntelPentiumIVCentrinochips,512MbRAM.

•ItemLE1601Software

DiversesoftwareusedasMapInfoandMarconiPlanet.

47

Planetusesthemostadvancedarchitectureanddesigncomponentsbasedon

MicrosoftNET.Itiseasycustomizableandallowstoworkwith3rdpartyvendors.

MapInfoisourpreferredmappingandcartographyapplication.

•ItemLE1702NetTekAnalyzer

TheNetTekAnalyzerisabasestationtransmitterandinterferenceanalyzer.The

TektronixNetTekanalyzerisarevolutionaryportablefieldtool.TheYBT250testmodule

tailorsthissystemforfasttroubleresolutionandeasytransmitterverificationofcellular,

DCS/PCSand3GbasestationsandNodeBs.

TheNetTekAnalyzerwiththeYBT250testmoduleisnotanexpensive,doeverything

solution:instead,theNetTektestmoduleisoptimizedtoperformtheday-to-dayRFand

demodulationmeasurementtasksthatoccupythemajorityofatechnician’stime.

DataPerformance

ForDataperformancemeasurementsandanalysis,IMT-2000ftp/webtraceswere

collectedoverthenetworksaboveoffering1Xservices.Theclientweredescribedas

mobilephoneterminalsinuseinthenetworksexamined.anyCDMA20003G-1X

FTP/WebtraceswerecollectedoverthemobilephonesdataconnectioninCDMA2000

3G-1XNetworkinthenetworksanalyzed.Theclientsusedareestablishedbeforeas

designatedterminals(Samsung,LG,Sanyo,Nokia,Kyocera,Motorola,Audiovox).Inall

cases,theterminalsweresetwithmaximumidealdownlinkrateof144Kbpsandthe

networkoperatingat1900Mhz.Forwebdownloadsweusedthestandardwebsites

hostedinourremoteLabintheUnitedStates.Inaddition,someCDMA20003G-1X

tracesloggedindatacentersinthecountriesoflocationofthenetworkswereusedbut

48

inthiscasewehavethesender(serverside)tcpdumptracescollected.Traffictcpdump

tracestakenoverhigherdata-rateCDMA2000EV-DOandmeasuredwhenavailable.


29

Wehaveconducteddetailedperformancestudiesofdifferentapplicationsover

commercialWWANnetworks.Weprimarilyfocusontheperformanceofwebbrowsing

applicationsintheseenvironments.Ourexperimentsshowthatallstandardweb

browsersoperatingintheirdefaultsettingssignificantlyunderutilizethelimited

resourcesoftheWWANwirelesslink.Thisissurprisinginthecontextofpriorwork,

whichshowedthatTCP,theunderlyingtransportprotocolusedbyHTTP,makes

efficientuseoftheWWANwirelesslink.Infact,theseresultsarealsore-confirmedby

ourexperiments.Weexplainthisperformancediscrepancybasedoninefficienciesin

sessionandapplicationlayers.Ourexperimentsshowthatsuitableoptimizations

implementedintheselayerscansignificantlyimproveapplicationperformanceover

WWANenvironments.Ourresultsalsodemonstratethatcollectivesuiteofoptimizations

appliedatdifferentlayersoftheprotocolstackinmanycasesimprovesend-userweb-

browsingexperiencebyatleastafactoroftwo.

TopreciselyquantifythecausesofpoorperformanceoverWWANs,wefirst

benchmarkedstandardwebbrowsers,protocols,andtechniqueswithrespecttotheir

performance.Throughourexperimentswehavemeasuredthedifferentcomponents

thatcontributetothelatenciesduringwebdownloadsforarangeofpopularwebsites

(rankedinwww.100hot.com).Subsequently,weexaminedalargenumberof

optimizationchoicesthatareavailableatdifferentlayersoftheprotocolstack.

49

SpecificallywestudythefollowingaspectsoftheseoptimizationsforWWANs:

•Applicationlayer

WequantifythebenefitsofusingschemeslikeHTTPpipelining,extendedhash-based

caching,deltaencodinganddynamiccontentcompressionoverWWAN.

•Sessionlayer

Westudytheimpactofmultiplesimultaneoustransportconnectionsastypicalin

standardwebbrowsers,examinetheimpactoftechniqueslikeDNS-Rewritingand

URLrewritingandofserver-side‘parse-and-push’.Transportlayer,Weevaluatethe

performanceofstandardTCP,arecentlyproposedandimplementedlink-adaptedTCP

variantsuitedforWWANenvironmentsandacustomizedUDPbasedsolution.

•Linklayer

Westudytheinteractionbetweenlink-layerretransmissions(ARQ)andforwarderror

correction(FEC)schemesusingtrace-basedsimulationsfordifferentapplicationsin

WWANenvironments.Toconductthisstudyweimplementedallnecessarytechniques

(includingthreedifferentproxies)forourWWANinfrastructure.

Theresultspresentedinthisprojectsummarizesourexperiencesandlessonslearnt

throughdeploymentandoperationofourWWANtestbedintheCDMAnetworks.The


30

followingweresomeofourinterestingobservations:(1)AlthoughTCPitselfisrelatively

efficienteveninWWANenvironments,thedefaultHTTPprotocolsignificantly

underutilizestheWWANwirelesslinks.(2)Appropriateapplicationlayerandsession

layermechanismsarenecessarytocorrectthesignificantmismatchbetweentransport

andapplicationperformance.(3)Proxybasedoptimizationsarecrucialtorealizemany

50

oftheperformancebenefitsoverWWAN.

•KeyContributions

oWehighlightthemaincontributionofthisworkasfollows:Wepresentthe

firstdetailedevaluationofapplicationperformanceovercommercialWWAN

environments.

oWeimplementandstudyawideselectionofoptimizationtechniquesat

differentlayersandtheircrosslayerinteractionsonapplicationperformance.

Inourexperiments,weplacedtheproxyinourlaboratoryandthenuseawell

provisionedIPSecVPNto‘backhaul’thetrafficfromthecellularprovider’snetwork.The

mobileclientconnectstothewebserversthroughthisproxy.Wepresentanexperiment

methodologybasedonvirtualwebhostingthatisessentialforperformingreproducible

andrepeatableexperimentsoverWWANenvironments.

TestedandMethodology

TheexperimentsreportedinthispaperhaveprimarilybeenperformedonCDMA-2000

1XEV-DObasedWWANnetworks,whicharewidelydeployedindifferentpartsofthe

world.TheSGSNactsasapacketswitchthatperformssignalingsimilartoamobile

switchingcenter(MSC)inCDMAnetworks,alongwithcellselection,routing,and

handoversbetweendifferentBaseSwitchingCenters(BSCs).ItalsocontrolstheMobile

Terminal(MT)’saccesstotheCDMAnetworkandroutespacketstotheappropriate

BSC.TheGGSNisthegatewaybetweenthemobilepacketroutingofCDMAandthe

fixedIProutingoftheInternet.Wehavealsoexperimentallyevaluatedapplication

performanceonthenextgeneration(3G)cellularnetworks,whicharecurrentlybeing

51

deployedindifferentpartsoftheworld.Wirelesslinksusingthese3Gtechnologieshave

higherdataratesthanexisting2.5Gtechnologies.Ourpreliminarystudyconducted

overtwodifferent3Gnetworks,CDMA2000andW-CDMAUMTS,arepresentedin

Section5.Theseresultsindicatethatourobservationsandevaluationspresentedinthis

paperapplyalsotothesehigherdatarate3Genvironments.

Inthissetup,amobileterminal(MT),e.g.alaptop,connectstotheWWANnetwork

throughamobiledevice–aPCMCIACDMA20001X.cardoraphone.Inordertouse

theWWANnetwork,theMTfirstattachesitselftotheGGSN(PDSNinCDMA2000)


31

throughasignalingprocedureandestablishesaPoint-to-PointProtocol(PPP)

connectionwiththeGGSN.TheMTisdynamicallyassignedanIPaddressandthe

WWANnetworkisresponsibleforswitchingdatabackandforthtothisIPaddressas

theMTmovesthroughthenetwork.

InourexperimentstheMT(ormobileclient)downloadedwebcontentovertheWWAN

linkfromdifferentcontentlocations:(1)directlyfromtherealwebservers,e.g.CNN,

Yahoo,and(2)virtuallyhostedweb-servers(explainedlaterinthissection)thatwere

locatedinourlaboratory.

Ineithercase,thedatafromthemobileclienttotheserverstraversethroughthecellular

service-provider’snetworkaswellasthepublicInternet,beforeitisfinally‘back-hauled’

toourlaboratory.Tostudythedifferentoptimizationtechniquesatdifferentlayersofthe

52

protocolstackandtheiroverallimpactonapplication(web)performance,our

experimentsrequiredustoimplementoptimizationspecificproxies.

Basedontheuseofproxies,ourexperimentscanbeclassifiedintothreemodes:

•NoProxyMode

Inthiscasetheclientdirectlyconnectedtotheserverandtheexperimentsdidnot

requireanyinterveningproxy.Theseoptimizationsaretheeasiesttodeploy.

•TransparentProxyMode

Thismodeisusedforthoseexperimentsheretheclientneednotbeawareofthe

existenceofaproxyandthecellularprovider’snetworktransparentlyguidestheclient’s

connectionsthroughaproxyasnecessary.Transparentproxysolutionsarealsoeasy

todeploy,sincetheyrequireochangesorconfigurationtobemadeinthemobileclients

themselves.

•ExplicitProxyMode

Thismodewasusedinexperimentswhichrequirethemobileclienttobeawareofthe

proxyinthenetwork(inthiscasecalledthe‘server-side’proxy).Thisrequireseither(a)

explicitbrowserconfigurationor(b)softwareupdatesatthemobileclienttoenableitto

interactwiththeserver-sideproxy.Thesoftwareupdateisa‘client-side’proxyand

hencewerefertothisapproachasadual-proxysolution.

Intheproxy-basedoptimizationstheproxyneedstobedeployedwithinthecellular

provider’snetwork.Sinceitwasnotpracticalforustoinstallourownequipmentinside

acommercialcellularnetwork,weinsteadplacedtheproxyinourlaboratoryandused

awellprovisionedIPSecVPNto‘backhaul’CDMAtraffictoitdirectlyfromthecellular

53

provider’snetwork.Thisensuredthatthepathbetweentheproxyandthecellular


32

provider’snetworkwasneverthebottleneck.Intheproxy-basedexperiments,the

mobileclientconnectstothewebserversthroughthisproxy.

ExperimentalMethodology

Weusevirtualwebhostingtoemulaterealwebdownloads.Virtualwebhostingisan

importantconstructtoperformrepeatablewebbrowsingexperimentsoverWWANlinks

involvingfast-changingwebsites.

Contentsofpopularwebsiteschangeveryfrequently(e.g.inCNNcontentchanges

withinminutes).Ifrealweb-downloadexperimentsweretobeconductedoverlow-

bandwidthWWANlinksinvolvingsuchweb-sites,thendifferentdownloadattemptsmay

noticesignificantdifferencesinthedownloadedcontentstructureandvolume.Thetotal

numberofdownloadsrequiredforeachwebsiteconsideredinthisworkwasmorethan

500(includingatleast20downloadsforeachconfiguration).Thistranslatestoa

durationofover1500minutestoperformtheexperiments,leavingsidesetuptimes,

transientnetworkcongestion,unavailablewirelesslinkconditions,etc.Henceitwould

nothavebeenfeasibleforustomakemeaningfulcomparisonsperformeddirectlyusing

realwebsites.Toavoidthisproblemweimplementedavirtualwebhostingsystemin

ourlaboratory,wherewereplicatedthecontentsofthepopularwebsitesintoasetof

webservers(inourlaboratory)withpublicdomainnames.Thusamobileclientcan

accessthevirtuallyhostedwebpagesusingWWANnetworksjustastheywouldfrom

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actualserversinarepeatableandreproduciblefashion.Asnapshotonthemain

webpageofapopularnewsweb-sitelikeCNNshowsthatithasmorethan100

embeddedobjects.Whilesomeoftheseobjectsmaybehostedonthemaincontent

servers,there’sarehostedbyCDNservers,e.g.Akamai.

Whenauserattemptstodownloadhttp://www.cnn.com,thebrowserfirstperformsa

DNSlookuptoresolvecnn.comanddownloadsthemainwebpage.Subsequentlyit

performsfurtherDNSlookupstoresolvetheCDNserversthatholdsomeofthe

embeddedobjectsinthatpage,andperformsappropriatedownloadsfortheseobjects.

DownloadsfrompopularwebsitessometimesinvolvesalargenumberofDNSlookups,

whichsignificantlyaffectthedownloadperformanceoverWWANlinks.Hence,inthe

virtualwebhostingsetup,itwasnecessarytofaithfullyreplicatethedistributedweb

contentanditsoverallstructure.Foreachserverintheoriginalwebsite,weassigneda

separatewebserverinourlaboratoryto“virtually”hostthecorrespondingcontent.The

domainnamesofthesevirtualweb-hostingserverswereconstructedfromtheiroriginal

domainnamesbypre-pendingWeb-page.


33

BenchmarkingPerformance

Ourexperimentalevaluationisfocusedontheweb-browsingperformanceoverWWAN

network.Wehaveexperimentedwithdifferentstandardweb-browsersavailable(e.g.

InternetExplorer6,Netscape7.0).Someotherwebbrowsersforhandhelddevices(e.g.

Blazer,PocketIE)mayhaveadditionalfeaturessuchasprogressiverenderingand

55

smartcaching.Whiletherearesomevariationsintheirimplementations,weobserved

thattheirbehaviorisroughlysimilar.Intheexperimentalresultsreportedinthispaper,

weusetheMozillabrowserversion1.4.InitsdefaultsettingMozillaopensupto8

simultaneousTCPconnectionsperweb-serverusingHTTP1.0andupto2TCP

connectionsusingHTTP/1.1.Mozillaalsosupportsproposedexperimentalfeaturesin

HTTP/1.1,e.g.pipelining.Duetoitsopensourcenature,itwaseasiertoalterthedefault

browsertosuitexperimentalneeds.

Theexperimentsreportedinthispaperwereperformedusingalaptopwitha1.4GHz

processorrunningLinux(kernel2.4.20)whichconnectstotheWWANCDMA2000

networkusinga‘3+1’CDMAphone.TheWWANoperatesinthe1.8-1.9GHzbandand

supportstheuseofCS-2codingschemeforForwardErrorCorrection(FEC).CS-2isa

‘goodcompromise’codingschemegivinganidealdownlinkdatarateof39.6Kbpsfor

a‘3+1’phone.(NotetheactualpayloadthroughputseenbytheRadioLinkControl–

RLClayerisslightlylowerthanthisvalue).Thereliability(retransmissions)offeredby

theRLClayerwaskeptenabled.Furthermore,wesawnoevidenceofnetworkresource

contention(CDMAtime-slots)inourWWANcell.Thisisperhapsduetothesmall

numberofCDMA-20001Xusersandgeneroustime-slotprovisioningbytheWWAN

operator.Inallourexperimentsthemobilehost(laptop)waskeptstationarytoavoid

linkvariations.MeasuredsignalqualityatthelocalFileSize(KB)FTP-throughput(Kbps).

Theseresultsindicatethattherearesignificantopportunitiesforoptimizingweb

browsingperformanceforWWANnetworks.

PerformanceOptimizations

56

Wehaveexaminedandcharacterizedtheperformanceofawideselectionof

optimizationtechniquesthathavebeenproposedatthedifferentlayersoftheprotocol

stack—application,session,transport,andlink.Asdiscussedsomeofthese

optimizationtechniquesreliedonatransparentorexplicitproxythatwaslocatedinour

laboratory.

Wewillquantifytherelativebenefitsobservedbyeachofthesetechniques,exceptfor

theexplicitdual-proxytechniquesinmostcases.Thedual-proxytechniquesworkswith

verydifferentassumptionsofdeploymentandhenceitisnotpossibletomakeafair


34

comparisonofthesetechniqueswiththeno-proxyorsingle-proxytechniques.Therefore,

wewillpresentthebenefitsofthedual-proxyschemesindividuallyandcommenton

theircombinedeffectsinthesummaryofresults.

ApplicationLevelTechniques

Weconsiderthreeapplication-leveloptimizationtechniques.First,weexaminecontent

compressionanditsimpactonwebdownloadperformance.Ourresultsshowthatweb

contentishighlycompressible,butthisdoesnottranslatetocommensuratebenefitsin

webdownloadperformanceoverWWAN.Next,weexaminethevariouschoices

availablethroughtheHTTPprotocol,e.g.HTTP/1.1withpersistentconnectionsand

HTTPrequestpipelining].Ourresultsshowthatthedefaultconfigurationparametersof

mostbrowsers(typicallychosentoworkwellinwirednetworksorwirelessLANs)

performpoorlyinWWANenvironments.

57

Finally,wealsoexploresomeadvancedtechniquesincludingdeltaencodingand

extendedcaching.

ØDynamicContentCompression

Thetotalsizeofcontentofmanywebpagesisquitelargerelativetothedownlinkdata

rateofWWANnetworks.Hence,contentcompressionisanaturalcandidatetofurther

reducedownloadlatencies.Wefirstexaminethe“compressibility”ofthedifferent

websites.Weclassifycontentintotwoparts—fixedfidelitycontent(includesallHTML,

CSS,JS,files)andvariablefidelitycontent(includesallimages).Forallfixedfidelity

dataweappliedlosslessdatacompression,usinggzipandforallvariablefidelitydata

weappliedlossdatacompression,byreducingthedepthlevelofimages.

Notethatotherformsofdatacompression,e.g.htmlreformatting,imageresizing,etc.

couldalsobeappliedhere.However,wedonotemploysuchtechniquesinourproxy,

sincetheyrequiresignificantknowledgeofthecontentsemantics.Weimplement

dynamiccontentcompressionusinganapplication-levelproxyoperatinginthe

transparentaswellastheexplicitdual-proxymode.WebsiteFixed-fidelityVariable-

Wepresenttheperformancebenefitsofcontentcompressionofwebdownload

latencies.Whenlosslesscompressionisused,theclientneededtoperforman

uncompressedoperation.(NotethattheextraCPUoverheadtouncompressed,saya

100KBdatafile,isoftheorderofafewmillisecondsformosthandhelddevicesandis

insignificant.)Wecanobservethatalthoughthecontentinthedifferentwebsitesare

verycompressible,thebenefitsofcompressiononapplicationperformancei.efullweb-

pagedownloadtimeisnotassubstantial(exceptforYahoo).


58

35

Wecanexplainthisapparentanomalousbehaviorbasedontheobjectsizedistribution

ofthewebpages.Wecanobservethatmostoftheobjectsinthewebpagesaresmall,

e.g.nearly60%oftheobjectsinCNNarelessthan1KB(typically1TCPsegmentfor

1400bytepayloadIPpackets).Anyamountofcompressionwouldclearlynotchange

thenumberofsegmentsbelowone.FurthermoreeachGETrequestforsuchsegments

willincuranoverheadofatleastoneWWANroundtriptime.Therefore,thetotal

overheadofissuingindividualGETrequestsforeachoftheseobjectsintheweb-page

sequentiallyovertheTCPconnectionsstartsdominatingtheoveralltransfertimeof

theseobjectsandhenceimprovementintheweb-pagedownloadlatencydueto

compressionwillbeminimalinthesecases.Incontrast,thedistributionofobjectsizes

intheYahoowebsiteisskewedtowardslargervalues(theaverageobjectsizeis3.8KB

inYahoo,asopposedto2.2KBand2.8KBforAmazonandCNNrespectively).Wecan

observeherethattheimpactofcontentcompressionissignificantlygreatersincethe

numberofobjectsinYahooweb-pagearerelativelyfew(hencereducedRTToverheads

ofissuingGETrequests)whiletheaverageimagesizelarge(therebyyieldinggreater

compressionfactorperimageobjectwheremostobjectsarelarge).Hencethe

improvementinresponsetimebyreductioninthepayloadofferedby

ØMechanismDescription

HTTP/1.0UseofseparateTCPconn.ForeachobjectdownloadedHTTP/1.1-def.Use

oftwo“persistent”TCPconn.todownloadallobjects.HTTP/1.1-PipeliningUseof2

“persistent”TCPconn.withsimultaneousGETsHTTP/1.1-Opt.Useof6“persistent”

TCPconn.compressingtheobjectsincaseofYahooisfargreaterthanthe

overheadofissuingindividualGETs–datacompressionhasasignificantlybetter

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impactondownloadlatenciesofsuchwebsites.

ØOptimizingHTTPusingPipelining

Manycurrentwebbrowserscontinuetousenon-persistentconnections(HTTP/1.0),

whichopens-upnewTCPconnectionforeveryobjectdownloaded.Incontrast,

HTTP/1.1initsdefaultmodeopenstwoTCPconnectionstoeachserverwhichareused

todownloadalltheobjectsfromthatserver.OurresultsshowthatHTTP/1.1-default

suffersfromsignificantunder-utilizationoftheWWANlink.Thereforewenowstudythe

impactoftheHTTP1.1-Pipeliningfeaturewhichisanexperimentaloptioninthestandard.

InTable5wesummarizethedifferentvariantsoftheHTTPprotocolthatwestudy.A

browserthatimplementsHTTPrequestpipeliningisallowedtoissuenewGETrequests

withoutwaitingfortheentireresponseofthepreviousones.Henceabrowsercanuse

thismechanismtoissuesimultaneousGETrequestsandensurethattheTCP

connectionarefullyutilizedfordatatransfer.ThisisincontrasttotheHTTP/1.1-default

(non-pipelined)whichissuesGETrequestssequentiallyovereachopenTCP


36

connection.Infact,itispreciselythis‘stop-and-go’GETbehaviorofHTTP/1.1-default

whichleadstosignificantofunder-utilizationoftheWWANlink.

InTable6wecanseethatHTTPPipeliningprovidesbetween35%to56%benefitfor

thedifferentwebsites.ThebenefitisparticularlyhighforlargewebsiteslikeCNNwith

manyobjectsintheirwebpage.Weexplainthisusingthedistributionofobjectsizes

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shownearlier.Mostoftheobjectsinthesepopularwebpageshavealargenumberof

smallobjects(e.g.CNNhasmorethan60%oftheobjectslessthan1KBinsize).The

defaultHTTP/1.1protocolgetseachofthesesmallobjectssequentiallyoveritstwoTCP

connections,andwaitsnumeroustimesbetweenthecompletionofeachGETrequest

andthebeginningofthenext.

Incontrast,pipeliningallowsmanyGETrequeststobeissuedsimultaneouslyythe

mobileclientandhencetheobjectsarefetchedwithoutanyinterveninggaps.TTP

pipeliningisanexperimentaltechniqueintheHTTP/1.1standardandwefoundthat,

unfortunately,mostbrowsersdonotenablethisfeaturebydefault.Additionally,our

experimentsshowthatthewebserversofmanypopularwebsitescurrentlydonot

respectthispipeliningfeature.Therefore,therealperformancebenefitsofthis

mechanismonwirelesswebbrowsingcanbequitelimited.Inalloursubsequent

experimentation,wewillignoreHTTP/1.1-pipeliningtechniqueforthisreasonandre-

visititinoursummaryofresults.Wewillstudytheimpactofasessionlayertechnique

inwhichwevarythenumberofsimultaneousTCPconnectionsandshowhowitcan

approximatethebehaviorofHTTPpipelining.

ØExtendedCachingandDeltaEncoding

Inthisexplicit,dual-proxybasedoptimization,weevaluatedextendedcontent-hash

basedcachinganddeltaencodingschemes.Inthisscheme,a‘client-proxy’software

wasinstalledinthemobiledevicewhichinteractedwiththe‘server-side’proxylocated

intheWWANinfrastructure.Intheextendedcachingscheme,theclientaswellasthe

serverproxyindexeswebobjectsbytheirSHA-1fingerprint,whichwecallContent

HashKey(CHK).Eachtimetheclientattemptstodownloadawebpage,itgetsaCHK

listofalltheobjectsinthewebpagefromtheserver-sideproxy.Usingthis

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information,

theclientmakesrequestforonlysingleinstanceofobjects,eveniftheypointtomultiple

URLs(sameresponsebutaliasedtomultipleURLs).Experimentshaveshownthatin

manydynamicallygeneratedwebsites(e.g.bbc.co.uk)suchaphenomenonis

commonplace(alsoknownasresponsealiasing).Hence,CHK-basedcachingisable

toeliminateredundantdatatransferoverWWAN,savediskspaceandalsoimprove

overallwebdownloadtimes.

Whenthedatabeingdownloadedisadifferentversionofthesameobjectpreviously

cached(i.e.sameURLbutdifferentCHK),adeltaencodingschemeisused.Delta

encodingisastandardtechniqueinwhichtheserver(inourcasetheserver-sideproxy)


37

sendsonlythedifferencesbetweenthenewandoldversionsofadocumenttotheclient.

Thistechniqueisveryusefulforwebsiteslikecnn.comandbbc.co.uk,wherethe

contentchangesincrementally,butfrequently(e.g.time-of-daystrings).Ourexperience

showsthattheuseofCHK-basedcachinganddelta-encodingonaverageimproves

realweb-browsingperformancebyabout3-6%insuchfast-changingweb-sites.Note

thatindividualbenefitsfromCHK-basedcachinganddeltaencodingdependslargely

onthetypeofweb-siteanditscontent.Ingeneraltheseareexpectedtovaryfordifferent

web-sites.Thefiguresreportedherearebenefitsuserscannominallyexpectforour

exampleweb-sitesduringrealweb-browsingsessions.

SessionlayerTechniques

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Thegoalofthesession-layeroptimizationsistomitigatethelink‘idletime’effects

incurredduringDNSlookupsandsomeotherfactorsduringwebdownloads.We

performedadetailedstudyoftheperformanceenhancementschemesfor:

(1)impactofmultiplesimultaneoustransportconnectionsastypicalinstandardweb

browsers,

(2)impactofDNSlook-upsonwebdownload,and,

(3)server‘parse-and-push’technique.WestudyURL-rewriting/DNSRewritingwiththe

transparentproxy,andParse-and-Pushschemeasanexplicitdual-proxyapproach.

ØVaryingNumberofTCPConnections

WeshowedthattheHTTPpipeliningfeaturehassignificantimpactonwebbrowsing

performanceinWWANmailTCPconnectionsforthewebbrowserwasvaried.

DownloadtimesnormalizedwithrespecttotheHTTP/1.1defaultoftwoTCPconnections.

(ThedefaultconnectionsettingsinWebbrowsersleadstosignificantunder-utilization

overWWAN.)environments.Unfortunately,thepipeliningfeatureisnotfaithfully

supportedbymanycommercialwebservers.Thereforewelookatanalternative

sessionlayertechniquewherewetreateachHTTPdownloadasasinglesessionand

optimallychoosethenumberofsimultaneousTCPconnectionsopenedbytheclientto

theserver.ThenormalizationwasdonewithrespecttoHTTP/1.1-default(two

connections).Inallthecases,wefoundthebestperformancewhen6connectionswere

used(wecallthisHTTP/1.1-Opt).ThedownloadlatencyforHTTP/1.1-Optreducedby

35-42%forthedifferentwebsites.ThenumberofparallelGEToperationsincreasewith

thenumberofconnections,thus,decreasingthetotal‘idletime’onthewirelesschannel.

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However,weobservenoadditionalbenefitsofincreasingthenumberofconnections

beyondsix,atwhichpointthedownloadperformanceislimitedbyotherinefficiencies

(e.g.DNSlookups,TCP3-wayhandshakeandslowstarteffects,etc.).Infact,the

performancedegradesduetoadverseinteractionsandoverheadfromtheTCP

connections.


38

TheoptimalnumberofTCPconnectionsthatminimizesdownloadlatencyisaproperty

ofthewirelessinterfaceandthenetwork.Ourresultsindicatethat6TCPconnections

providemaximumthroughputwhenusingaGRPSnetworkwithanidealdownlinkdata

rateof39.6Kbps.TheoptimalnumberofTCPconnectionscanvaryforaCDMA2000

3G-1Xnetworkwithanidealdownlinkdatarateof144KbpsorforaUMTS3Gnetwork

withmaximumdownlinkdata-rateof384Kbps,andwerecommendanempirical

configurationoftheoptimalsettingsinbrowsersbasedonsuchpropertiesoftheWWAN

network.IncreasingthenumberofsimultaneousTCPconnectionsisanaggressive

behavior.However,forbandwidth-depletedenvironmentslikeWWANenvironments,

suchabehaviorleadstosignificantimprovementintheuserexperience(i.e.forCNN

thedownloadlatencyreducesfrom196.3secondsto123.0seconds).

WecanobservethattheuseofHTTP/1.1-Opt(6connections)leadstosignificant

performancebenefitsforwebdownloads.Whiletheperformanceimprovementof

HTTP/1.1-OptissimilartothatofHTTP/1.1-Pipelining,itissomewhatlowerinsome

cases.ThisisbecauseHTTP/1.1-Optisonlyabletoapproximatethebehaviorof

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HTTP/1.1-PipeliningbycarefullychoosingthenumberofsimultaneousTCPconnections.

IncludesApp.Opts:FullCompression

Thegoalofboththeseoptimizations,intheWWANcontext,aresimilar—toreducethe

numberandoveralldurationofidletimesbetweensuccessiveGETrequestsovereach

TCPconnection.SincemostwebserverscurrentlydonotsupporttheHTTPpipelining

option,HTTP/1.1-OptisanalternativeapproximationthatmaybeusedbyWWANclients

torealizesimilarbenefits.

•URLRewriting/DNSRewriting

ThesearetwoalmostequivalenttechniquesthattransparentlyreducetheDNSlookup

andTCPconnectionsetupoverheadsatthemobileclient.IntheURLre-writing

technique,theproxyinthecellularprovider’snetworkinterceptstheGETrequestissued

bytheclientforawebpage,sayindex.html,andmakesappropriateserverrequestson

theclient’sbehalf.Onreceivingtheindex.htmlpage,theproxyparsesthecontents,

andidentifiesthenamesofallotherserversthatholdsdifferentembeddedobjectsand

replacesthemwithitsownIPaddresssimilartoschemesemployedbyContent

DistributionNetworks.Itthenrespondswiththismodifiedindex.htmltotheclient.The

clientnowdirectlycontactstheproxyusingthelatter’sIPaddressfortheseembedded

objectsthroughsubsequentGETrequests.Theproxyagain(pre-)fetchestheseobjects

fromtheotherserversandinturnservesthemtotheclient,muchlikeawebcaching

system.ThustheclientneedstoperformatmostoneDNSlookup.DNS-Rewriting

achievesthesameeffectasURLre-writing,butbyintelligentlymanipulatingDNS

queriesfromtheclient.ByrespondingtotheDNSquerieswithafixedIPaddress,the

65

DNSRewritingtechniqueimplicitlyforcestheclienttopointtoonesingle(proxy)server


39

sothatclientcanopenanoptimalnumberofTCPconnectionstherebyimprovingoverall

performance.Thus,wefindthatbothschemescanbenefitperformanceintwoways:

(1)byavoidingextraDNSLookups,and,

(2)byminimizingtheoverheadofopeningdistinctTCPconnectionstodifferentservers.

Toquantifythebenefitsoftheseschemes,weimplementedtheDNS-Rewriting/URL-

rewritingproxyandperformeddownloadexperimentsfordifferentwebsites.Wepresent

theresults.

Sincewewantedtoquantifytheadditionalbenefitsofthedifferentsessionlevel

techniques,weperformedtheapplication-leveloptimizations(notincludingHTTP/1.1-

pipeliningsinceitsprevalenceisstilllimitedincommercialwebservers)inallthese

experiments.Asnotedbefore,useofHTTP/1.1-Optitselfleadstosignificant

performancebenefits,i.e.between37-44%,whileeliminationoftheDNSlookup

overheadaddsanother5-9%improvementinthedownloadlatency.Thecombined

improvementsduetothesesessionlayertechniquesarebetween53-65%.

•Serverside

ParseandPush.Parse-and-pushisasession-level,explicit,dual-proxyschemewhere

theserver-sideproxylocatedattheotherendofthewirelesslinkintheWWANnetwork

attemptstospeculatively‘push’objectsWebsiteApp.+SessionOpts:1.1-Opt+DNS-

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b/URL-rDownloadtimeinseconds.Noneimpliesnotransportoptimizations,T1isTCP-

WWANandT2isUDP-CDMA.ImprovementswithrespecttoNone(firstcolumn)

towardstheclientthatitknowstheclientwillhavetodownload.Forexample,whenthe

clientmakesarequestfortheindex.htmlpage,theserver-sideproxywillbeginpushing

thevariousobjectsembeddedintheindex.htmlfileevenbeforetheclientmakesexplicit

GETrequestsforit.Parse-and-pushemulatesdeterministiccontentpushingtowards

themobileclient,whenthewirelessdownlinkwouldhavebeenotherwiseleftidle.While

supportingparseandpushmechanismrequiresexplicitclient-sidesoftwareupdate,

theschemehelpstoimproveoverallutilizationofthelink.Ourexperimentshaveshown

thatparse-and-pushcanprovideanadditionalbetween5%to12%improvementinthe

web-pagedownloadlatencyforpopularwebsites.

TransportlayerTechniques

Wenowexaminetwooptimizationtechniquesinthetransportlayerthathavebeen

proposedinrecentliterature.Thefirstoneisatransparent-proxysolutionthatattempts

tooptimizeTCPperformanceusinga‘transparent’proxylocatedinthecellular

provider’snetwork,werefertothistechniqueasTCPWWAN.Theotherisan‘explicit

dual-proxy’solutionwhichdefinesacustomprotocolbasedonUDP(wecallitUDP-

CDMA.)


40

WhileTCPisdesignedtooperateoverawide-rangeofnetworkandlinkconditions,the

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optimizedprotocolsstudiedinthissectionspecificallyleveragetheknowledgeofthe

underlyingWWANwirelesslinksandhenceachieveimprovedperformance.Dueto

spaceconstraintsweonlysummarizethekeyfeaturesofboththeseimplementations.

•TCPWWAN

TCPWWANdefinesatransparentproxy-basedsolutioninwhichtheproxyislocatedin

thecellularprovider’snetwork.Theproxyspecificallyaddressessomeofthemain

performanceproblemsofTCPforwebdownloadsoverWWANs.Forexample,instead

ofusingtheTCPslowstart,itusesapre-determinedvalueofthebandwidth-delay

productandperformsaggressiverecoveryduringpacketlossesandlinkstalls.Note

thatsuchaggressivebehaviorcanbeverydisruptiveifimplementedintheInternet.

However,TCP-WWANisimplementedonlywithinthecellularprovider’snetworkwhich

alreadyimplementappropriatebandwidthsharingmechanisms(forCDMA2000)

betweenusersatlowerlayeroftheprotocolstack.StandardTCPleadstolargequeue

build-upduetogenerousbufferprovisioninginWWANnetworks.Long-livedTCPflows

destinedtomobileclientsaccumulatesegmentsintheselargequeuescausingSender

TCPRTOinflationthatprolongsrecoveryduringloss.Furthermore,WWANlinkscanbe

subjectedtolink‘stalls’.Whensuchlinkstallsoccur,undeliveredTCPsegments

accumulateintheselargeWWANqueues,whicharethencorrectlyre-transmittedby

thereliablelinklayeronlinkrepair.However,thisresultsinsenderexperiencingsudden

‘delayspikes’thatcancausespurioustimeouts.NotethatTCP-WWANcanestimatethe

DownloadLatency(Norm.)FEC%Impactofdynamiclink-layerFECsonDownload

Latency

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WWANlinksonbulkdatadownloadsunderdifferentchannelconditions.(WWANtrace-

drivensimulations)availablebandwidthonthewirelesslinktosufficientlyregulatethe

flowofTCPsegmentstowardsthemobileclient.Itavoidsexcessqueuebuild-upinside

WWANnetworksandalsopreventsspurioustimeoutsshouldwirelesslinkstallsoccur.

WeimplementedaTCP-WWANproxyforanexperimentalevaluationofthistechnique

basedonthedescriptionofChakravorty,Katti,PrattandCrowcorft.

•CustomTransportProtocol

UDP-CDMA2000isanexplicitdual-proxybasedschemetoimprovethetransport

performanceofwebdownloads.ThisschemedefinesareliableprotocolusingUDPand

implementsordered,reliable,messagetransfer.Theprotocolisoptimizedspecifically

forCDMAnetworksbyleveragingitsknowledgeoftheCDMA2000wirelesslink.For


41

example,thisprotocolisawarethattheCDMA2000linklayersofferreliablein-order

datadelivery.HenceitusesaselectiverepeatwithNegativeAcknowledgementsfor

lossrecovery.UsingsuchspecificpropertiesandcharacteristicsofCDMA2000links,

thisprotocolrespondsefficientlyevenintheeventofcommonpatternsofpacketlosses.

Periodicmessagesaregeneratedeveryfewsecondswhichallowhoststodetect

seriouslinkstalls.Ifsuchalinkstallisdetected,theclientdisconnectsandre-attaches

totheCDMA2000network.Experiencehasshownthatthisactionoftenrepairsthe

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link

failures.

Anunawaretransportprotocol(e.g.standardTCP)willexperiencesevereback-offsand

failuresundersimilarcircumstances.UDP-CDMA2000,bydesign,alsoavoidsTCP’s

connectionsetupandslowstartdelays.WhileTCPhastooperateoverlinkswithwidely

varyingqualities,beingacustomsolutionUDP-CDMA2000canmakemanymore

assumptionsabouttheunderlyingnetwork.Forinstance,sinceCDMA2000networks

implementamechanismtosharebandwidthbetweenusers,thereisnoneedforthe

UDP-CDMA2000protocoltoimplementitsowncongestionavoidancemechanisms.

Instead,itemploysasimplecredit-basedflowcontrolscheme.Thecreditvalueisso

chosentoensurethatthewirelesslinkremainsfullyutilizedeventhoughthebuffer

occupancyinthecellularnetworkremainslow.Thisavoidsexcessqueueingthatsome

longlivedTCPflowscause.Wepresenttheadditionalperformancebenefitsofapplying

theabovetransport-leveloptimizations.WecanobservethatTCP-WWANachieves

between5-13%additionalbenefitsforthedifferentwebsites.UDP-CDMA2000

leveragesitsspecificknowledgeofthewirelesslinkcharacteristicstoimprovethe

downloadperformancefurther(between7-14%forthedifferentwebsites).

LinklayerTechniques

Wefinallypresentanevaluationoflink-layermechanismsandtheirimpactonuser

performance.WWANwirelesslinksusetwodifferentschemestoprovidereliability

acrossthewirelesslinksoverawiderangeofchannelnoiseconditions.Thefirstofthis

isadataencodingschemewithvariouslevelsofForwardErrorCorrection(FEC).For

example,CDMA2000networksusefourdifferentFECschemes(CS-1toCS-4).The

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choiceoftheappropriateencodingschemeismadestaticallybytheRadioLinkControl

(RLC)layer.MostcurrentCDMA2000WWANsmakeuseoftheCS-2scheme,which

allowsgooddataprotectioninmoderatetohighnoisyradioconditions.Thesecondone

isanAutomaticRepeatRequest(ARQ)schemethatworksaggressivelytorecoverany

datatransferlossesthroughre-transmissions.Sincere-transmissionsincurdelays,all

shorttermlinkoutagesarehiddenfromthehigherlayersandmanifestasincreased

delays.Thehigherlayerswilldetectlossesonlyfor


42

(1)deepfadingthatleadstoburstylosses,or

(2)cell-reselectionduetothecellupdateprocedurethatleadsto‘black-outs’(orlink

stalls).

WestudymechanismsthatwillallowtheRLCtodynamicallychoosetheencoding

schemesinconjunctionwiththeabilitytoenableordisableARQ,andtheimpactof

suchmechanismsonapplications.Performingactualexperimentationforallofthis

studywasdifficultsincewehadnocontrolontheencodingschemesusedbytheBase

Stationtotransmitdatatothemobileclient.Atthemobileclientweonlyhadtheflexibility

toenableordisableARQ,andtheabilitytodisableFECs.Inordertostudythetrade-

offsbetweenARQ-basedandvariableFEC-basedlinklayerreliabilityapproaches,in

somecaseswereliedontrace-basedsimulations(thetracesweregeneratedfrom

actualexperimentsonourtestbed).

Ourtracesweregeneratedasfollows:wesentastreamofUDPpacketsfromtheproxy

tothemobileclient.TheWWANwirelesslinkisthebottleneckinthissystem,and

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therefore,theseUDPpacketswillqueueatthebasestation.TheRLClayerwill

appropriatelyfragmenttheseUDP/IPpacketsintoblocksandpacethemouttothe

mobileclientattheratepermissiblebythewirelesslink.Togenerateourtraces,we

disableARQ.AdditionallywesettheRLClayeratthemobileclienttodeliverallpackets

uptotheIPlayer(includingpacketsinerror)1.TheRLCblocksaresub-dividedinto

slots,andwecaninferwhichslotsare1Blockswithcorruptedheaderscouldnotbe

correctlyinterpretedandhencewasnotdeliveredtotheupperlayerscorruptedover

thewirelesslink.WethenapplyvariouslevelsofFEC-basedencodingsandARQon

thesetracesandobservetheirperformanceontheapplications.Weconsidertwokinds

ofapplications:

(a)reliabledatatransferapplications(likeftpandwebtraffic),and,

(b)nonreliabledatatransferapplications(likestreamingmedia).

Forreliabledatatransferapplications,weassumethatthelinklayercandynamically

chooseanamountofFEC(includingnone)toapplyontheRLCdatablocks.Forease

ofexposition,weassumethattheFECisappliedatthegranularityofslots.Ifthereare

100slotstoablockandtheamountofFECappliedis5%,then5outofthese100slots

areusedtoredundantlyencodetheremaining95.Slotsthatarenotrecoveredafter

FECisapplied(duetohigherchannelerrorconditions)arerecoveredusingtheARQ

scheme.Forthenon-reliabledatatransferapplicationswecompletelydisableARQ.

HencedatathatcouldnotberecoveredafterFECisapplied,islost.

•ReliableDataTransferApplications

Weplotthenormalizeddatadownloadlatencyforreliabledatatransferforalargedata

filefordifferentchannelconditionsandamountofFEC(thedataisnormalizedwith


72

43

respecttotheexperimentwiththebestchannelconditionandnoFEC).Itiseasytosee

thatforeachdifferentchannelconditionthereisanoptimalvalueofFECthatleadsto

theleastdownloadlatency.Forexampleamoderatelypoorchannel,withanerrorrate

of0.9%ontheCDMA2000channel,5-6%FECistheoptimalchoicetominimize

downloadtimes.Bydoingso,thedatalatencyreducesbyabout21.9%.Inabetter

channel(saywith0.2%errorrate)thecorrespondingbenefitisabout5%.Theamount

ofrequiredFECforsuchoptimalperformanceincreaseswithincreaseinchannelerror

rates.Thisdatasuggeststhat,insteadofusingafixedvalueofFEC(e.g.CS-2inCDMA),

networksshouldimplementanRLCthatcancontinuouslymonitorthechannel

conditionsanddynamicallychoosetheamountofFECtobeappliedonreliabledata

transfersacrossthewirelesslinks.

•NonReliableDataTransferApplications

Animportantconsiderationfornon-reliabledatatransferapplicationslikemedia

streamingisthejitterexperiencedbythedatastream.Ourexperimentsindicatethat

useofARQschemesfordatarecoveryincursahighjitterontraffic—itcanvary

between600msto3secondsdependingonthenumberofre-transmissionsattempted.

Forsuchnon-reliabledataapplicationsweconsiderthescenariowhereARQis

completelydisabled.OnlyvariableamountsofFECisusedtorecoverfromlinklayer

losses.UseofFECincursconstantdelayoverheadsevenwhenthechannelislossfree.

Whilethiswoulddecreasethejitterbetweensuccessivedatapacketsinsuchmedia

streams,underpoorchannel(highnoise)conditionsitwouldalsoincurlosses.

WeshowhowthechoiceofFECimpactslossesexperiencedbyastreamingapplication.

WecanseethatevenalowamountofFECissufficienttoobtainalowloss

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performance

forstreamingapplications,whilemaintaininglowjitter.However,adisadvantageof

usingFECtohandlelossesisareductionindatathroughput.Forexample,whenthe

channelerrorrateis0.9%,5-6%FECisusefultoeliminatemostofthechannelerrors.

Nevertheless,thisalsoleadstoareductionofusefuldatabandwidthby5-6%.Thegains

ofsuchFEC-basedapproachesareincorrespondingreductioninjitter.

SummaryofResults

Intheprevioussections,wepresentedanumberofdifferentoptimizationtechniquesto

improvewebdownloadperformance.ApplicationandSessionLayeroptimizations

dominateperformanceimprovements,weassumeareasonablygoodwirelesslink,

(errorlessthan0.2%)wheredynamicFECsprovidealatencyimprovementofupto5%.

Thisvalueisderivedfromourtrace-basedsimulations.ThebenefitsofdynamicFECs

willincreasewithpoorerwirelesschannelconditionsanddecreasewithfurther


44

improvedchannelconditions.Wehaveexploredtwoclassesofoptimizations—those

thatrequirere-configurationorsoftwareupdateinthemobileclient,i.e.usesanexplicit

proxy,(calledClient-reconf.)andthosethathavenosuchrequirements(calledNo-

reconf.).WeplottherelativecontributionoftheNo-reconf.schemeswhenallofthem

areappliedsimultaneously.Theoptimizationsinclude,FullCompression,HTTP/1.1-Opt,

DNS-Rewriting/URL-rewriting,TCP-WWAN,anddynamicFECs.WebsiteNo-reconf.-I

No-reconf.-IIClient-reconf.

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Theimprovementprovidedbyallthetechniquesappliedsimultaneouslywerethesum

ofthesevalues,63.0%,whichbroughtthedownloadlatencyfrom76.4secondsto29.3

seconds.Ingeneral,wecanobservethatapplicationandsessionlayertechniques

dominateimprovementsinwebperformance.Theyleadto48-61%performance

improvementsforourexamplewebsites.Thusourworkdemonstratesthatthe

applicationandsessionlevelmechanismscurrentlydeployedforwebbrowsing

applicationsmakepooruseoftherelativelyefficientlowerlayers.Employing

appropriateoptimizationsattheselayerscanhelpbridgethisperformancegap

observedbetweentheupperandlowerlayers.

Notethattransportandlinklayersoptimizationstypicallyprovide5-10%additional

performanceimprovements,whichisstillsignificantforwebdownloadsoverWWAN

links.

WedistinguishbetweentwodifferentNo-reconf.solutions:Noreconf.-IusesHTTP/1.1-

OptwhileNoreconf.-IIusesHTTP/1.1-Pipelining.Notethatthesetwotechniquesare

interchangeablesincetheyhavethesamegoalwithsomewhatsimilareffect.Inboth

thesesolutionswealsoapplyalltheotherNo.reconf.solutionsatthedifferentlayers.

TheClientreconf.solutionincludesFullcompression,Deltaencodingandextended

caching,Parse-and-push,andUDP-CDMA2000.Aswewouldexpect,theClient-reconf.

solutionleveragesextrafunctionalitybetweentheclientandtheserver-sideproxyto

achievebetterperformancethantheNo-reconf.techniques.Additionallywecan

observethatbetweenthetwoNo-reconf.solutions,thepipeliningbasedtechnique

achievesbetterperformancethantheHTTP/1.1-Optbasedtechnique.Thisindicates

thatpipeliningisaverycrucialtechniquetoimproveperformanceandshouldbe

enabledbyallwebservers.

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Discussion

Theresultspresentedindicatethatoptimizationsatindividuallayersofprotocolstacks

arenecessarytoachievesignificantperformancebenefitsinCDMA2000environments.


45

Alsoquantifiesthespecificbenefitsofperformanceoptimizationsatthesedifferent

layers.Inthissectionwediscussthefollowingrelatedquestions:

-Aretheseoptimization-basedbenefitsspecificto2.5GCDMA2000based

WWANnetworksordoweexpectsimilarperformancebenefitsinthenext

generation(3G)networksaswell?Hencewefirstpresentapreliminarycase

studyof3Gnetworksanddemonstratethatourobservationsinthispaperwould

largelyextendtotheseenvironments.

-AreWWANenvironmentsaspecialcaseoflow-bandwidthhigh-latency

networks?Inparticularshouldweexpectthattheoptimizationsstudiedinthis

paperinthecontextofWWANswouldalsoleadtoequivalentperformance

improvementsinwireddial-upenvironments?Hencewenextpresentasimilar

studyforwebapplicationsrunoverwireddialupenvironmentstodemonstrate

thatWWANenvironmentshavesignificantlydifferentcharacteristicsand

performance.WepresenttheseresultsforFTPandwebthroughputs

respectivelyaswediscusslater.

-Finally,wewillconcludewithadiscussionoflimitationsofproxy-basedsolutions

andtheimplicationsofsuchlimitationsinthecontextoftheresultspresented.

•Implicationsin3GNetworks.

Toevaluatethepotentialimpactofourresultson3GWWANenvironments,we

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conductedexperimentsovertwodifferentcommercialclass3Gnetworks–CDMA2000

3G-1XnetworkandW-CDMAUMTS3Gnetwork.Intheseexperimentsweuseda

SamsungVGA1000handsetforconnectingtothe3G-1Xnetwork(maximumideal

downlinkdata-rateof144Kbps)whilefortheUMTS3Gexperimentsweuseda3G

PCMCIAdata-card(qualcommchipset)formeasuringFTPandwebthroughputs(ideal

UMTSdownlinkdata-rateof384Kbps).

Thegoalofourstudywastoexaminethepotentialbenefitsofoptimizationsto3G

networks.HencewepresenttheFTPthroughputsfordifferentfilesizesandthe

unoptimizedwebthroughputforthefourwebsitesandcomparethemwiththe

correspondingperformanceofourCDMA2000experiments.Wequantifytheunder-

performanceofthetwodatatransferprotocols—theunder-performance(in

percentage).


46

WecanobservethatCDMA2000and3G(bothCDMA20003G-1XandUMTS)networks

exhibitasignificantadditionalunder-performancebetweenFTPandWebthroughput.

ForinstancetheFTPthroughputinthe3G-1Xcasefora200KBfileisabout36%less

thantheidealdownlinkdatarateof144Kbps,whereasthewebdownloadof186.8KB

sizeCNNpageshowsasignificantlygreaterunder-performance.Wecanalsocontrast

theCDMA2000and3G-1X(under)performancewiththatofUMTS3GWWANthat

offersamaximumdownlinkdata-rateof384Kbps.WefindthatforthecaseofUMTS

3GWWANtheaveragewebdownloadthroughputof62.3Kbps(againdownloadingthe

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CNNweb-page)isfarbelowtheaverageFTPthroughputof156.8Kbpsfora200KB

filetransfer.

Notethatintheseexperimentswedonotapplyanyperformanceoptimizationsatany

layer.Theseresultsdemonstratethatperformancemismatchasseenover2.5GCDMA

2000WWANarealsopresentin3GWWANenvironments.Thus,eventhough3Goffers

higherdataratesthan2.5G,thehighandvariablelinklatencyinWWANimpacts

performanceofweb-basedapplicationsnegativelyleadingtopoorend-user

experience.Appropriateuseandchoiceofoptimizationsimplementedatthedifferent

layersoftheprotocolstackasshowninthispaperarenecessarytoimprove

performanceandoverallend-userexperience.Henceweexpectthebenefitsfromsuch

performanceoptimizationstoextendtothesehigherdata-rate3Genvironments.

WiredDial-upEnvironments.Wealsoexperimentallyinvestigatedperformanceofwired

(dial-up)environments.WeconductedexperimentsusingastandardV.9056Kbpsdial-

upmodem.FTPandWebDownloadthroughputsforCDMAWANandwireddial-up

links.Heredegradation(in%)withrespecttoidealdownlinkdatarate.(Nosignificant

mismatchseenbetweenTCPandHTTPinwireddial-uplinks.)Interestingtonoteinthat

thereexistsnosignificantmismatchbetweenFTPandwebthroughputsinthewired

dial-upscenarios.Theperformancedegradation(withrespecttotheidealdatarateof

56Kbps)ofa100KBFTPis19%,whilethatofalargewebsitelikeCNNis32%.Thisis

veryunlikethecharacteristicsexperiencedinWWANenvironments.Weattributethis

differencetothefollowingreasons.First,theRTTsfordial-upmodems(inthe100-150

msrangefor64bytepackets)isrelativelylowerincomparisontothesignificantlyhigher

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valuesencounteredinWWANlinks(nominallyinthe400mstofewsecondsrangefor

samepacketsize).Hencethe‘stop-and-go’behaviorofHTTPprotocolsindefault

settingsleadstogreaterunder-utilizationinWWANlinksthanitdoesindial-upwired

environments.Clearly,theoptimizationsstudiedinthispaperwillleadtoimprovement

indownloadperformanceoverdial-upmodemsaswell,buttheimpactofthese

techniquesaresignificantlyhigherinWWANs.Second,theRTTvariabilityondial-up

linksismarginalwhencomparedtothatofWWANlinks.Finally,lossesencounteredin

wireddial-uplinksarefewandfarinbetween(unlikeWWANenvironments).Hence

althoughthewireddial-upenvironmentshavelowbandwidths,theirimpactondata

transferapplicationsisrelativelybenign.Itallowsmodemstoimplementadditional


47

statefulpacketandconnectioncompressiontechniquesthataremoredifficultto

implementinWWANenvironments.

Trade-offsinProxyDeploymentsoverWWANs.Ourresultsdemonstratethatproxy-

basedsolutionsprovidessignificantperformancebenefitstotheend-userexperience

overWWANs.However,thepresenceofproxybreaksthe“end-to-end”propertiesofan

applicationandhassecurityandotherrelatedimplications.Forexample,ifthe

webpagecontentsaredigitallysignedbythecontentprovider,thenanyupdatese.g.

URL-rewritingorcontentcompression,willviolatethesecurityguaranteesoftheclient.

Partoftheproblemwouldbesolvedifthecontentsourceitselfimplementedsuchproxy

functionality.Evenmorerealistically,itmaybenecessarytoprovidetheclientswith

79

the

appropriatechoicetotrade-offperformanceagainstend-to-endguarantees.Thus,a

clientbrowsingnewsatCNNmayacceptsomesusceptibilitytoinsecuredataatthe

costofsignificantperformanceimprovementsindownloadlatencies.Thesameclient

maynotuseaproxy-basedsolutionwhendownloadingstock-quotesandinsteadprefer

therigidsecuritypropertiesofend-to-endencryption.

Theexplicitproxybasedsolutionsdefinecustomizedmechanismstoprovidethebest-

knownbenefitstoWWANclients.However,clientre-configurationoraclient-side

softwareupdateisanintrinsicrequirementofsuchschemes.Thisincreasesthe

deploymentoverheadofsuchschemeshigherthantheotherclassofschemes.

Inmanycasesitisexpensiveforcellularoperatorstoprovidesuchupdatestoexisting

clientequipment.Thepriceperformancetrade-offofthewirelesscellularoperatorswill

finallydeterminethedeploymentofsuchmechanismsinWWANenvironments.The

benefitsavailablefromusingsuchintermediaries(proxysolutions)arealsogenesisto

novelarchitecturalproposalsthatespouseuseofintermediariesintherealmsofnew

Internetfunctions.Someinterestingnewproposalsenvisagefunctionsfor

internetworking,transparentaddressextensionoralayerednamingarchitecture.

Addressingsuchissuesarenecessaryevenfortruemobileconvergence.Thus,

architecturesthatcombineperformanceissuestoaddresssuchtrade-offsusing

proxiesinWWANbenefitsthe‘mobileInternet’evolution.


48

RelatedWork

Researchershaveexaminedvariousoptimizationchoicesatthedifferentlayersofthe

80

protocolstackinthecontextofbothwired,wireless,andalsoforWWANenvironments.

However,muchofthepriorresearchhasfocussedmainlyonisolatedperformance

optimizations.PriorresearchinWWANshaveprimarilyfocussedonthefollowingthree

aspects:

(a)improvingTCPperformanceoverWWANs,

(b)passiveanalysisofTCPtraffictraces,and,

(c)cross-layerinteractionandoptimizationsofTCPwiththelink-layer.

OurworkdiffersfromallpriorworkinWWANsinseveralways.Inourstudy

(1)wequantifythecausesofpoorapplicationperformanceandexaminetheuser

experienceoverWWANs,

(2)wemeasurethedifferentcomponentsthatcontributetothelatenciesduringweb

downloadsforarangeofpopularwebsites,

(3)weusevirtualwebhostingasanimportantconstructtoperformrepeatableand

reproduciblewebbrowsingexperimentsoverWWANs,

(4)webenchmarkstandardwebbrowsers,protocols,andtechniqueswithrespectto

theirperformance,and,

(5)weimplementandstudyawideselectionofoptimizationtechniquesatdifferent

layersandtheircrosslayerinteractionsonapplicationperformance.

Atthelinklayer,TULIPdescribesatransportunawareARQmechanismtoimproveTCP

performance.A.ChokalingamandAyanogluexaminetheinteractionbetweenARQand

FEC-basedlinkrecoverymechanismsinthecontextofwirelessnetworksthrough

detailedsimulationsandisrelatedtoourdiscussion.A.GurtovandS.Floydindiscuss

comparativeaspectsofmodelingdifferentwirelesslinksfortransportprotocols.A.

81

KumarcompareperformanceofversionsofTCPoverwirelesslinks.H.Balakrishnan

useexplicitlossnotification(ELN),mostlyinthecontextofwirelessLANs,toimprove

theperformanceofapplicationslikeHTTP.Forthetransportlayernewmechanisms

havebeendefinedtoimprovetheperformanceofreliable(data)applicationsinwireless

LANenvironments.ExamplesofthisareSnoop,I-TCP,M-TCPetc.However,solutions

meantforwirelessLANsmaynotworkthatwelloverWWAN.

Meanwhile,researchershavealsodemonstratedthattheCDMA2000WWANlinklayer

andTCPdonotadverselyinteractwitheachother.ExperiencewithUMTS3Gnetworks

alsoshowthatTCPworkswellwithlink-layer(RLC)retransmissions.Similarly,linklayer

(RLP)retransmissionsinCDMA20003Glinksensurepacketlossprobabilityofless

than1%andthatalsominimizesanyimpact(andadverseinteractions)onTCP.While

ourresultsagreewiththeseaboveobservationsthattheWWANlink-layerisgenerally

well-tunedfortransportprotocolTCPtooperateoverWWANs,theend-result(i.e.user


49

experience)forTCP-basedapplicationslikewebbrowsingremains‘remarkably’

different.Ourworkalsodemonstratesthatemployingappropriateoptimizationsatthe

applicationandsessionlayers(asdescribedinthispaper)providessignificantbenefits

toactualuser(web)experience.

Inotherimportantworks,R.Ludwiget.al.examinetheperformanceofTCPoverCDMA

82

cellularlinksandsubsequentlyproposespecificlinklayermechanisms(e.g.framesize

adaptations)thatarenecessarytoimproveTCPperformanceinsuchenvironments.P.

Sinhaetal.introduceWTCPasoneofthefirstsolutiontoovercomeperformance

problemsseenforTCPoverCDPD-basedWWANlinks.Manyofthelink-related

performanceissues(highRTTs,linkstallsetc.)observedinCDPDbasedWWANsare

similartothatobservedinCDMA2000and3G-1XbasedWWANs.M.C.ChanandR.

RamjeeproposeACKRegulatorforimprovingTCPperformanceoverCDMA20003G-

1Xlinks.UnlikeGSM-basedCDMA2000,3G-1Xlinksexhibitmuchhigherrateand

delayvariationsandtransport-layeroptimizationslikeACKregulatorcanbeusedto

significantlybenefitTCPperformanceinsuchenvironments.IETFRFC3135andRFC

3481providefurtherdetailsofdifferentmechanismstoimproveTCPperformancein

differentwirelessenvironments.Researchhasalsoinvestigatedsomeperformance

issuesoverCDMA2000,e.g.,alarge-scalepassiveanalysisofend-to-endTCPflows

andsomepreliminarystudyofproxyperformanceincellularnetworks.Inarecentwork

T.Bonaldetal.inexaminetheperformanceofwirelessdatasystemsinthecontextof

dynamicinteractionofactiveflowsinmulti-cellscenarios.

Proxyandcachingbasedschemestoimprovewebperformance,similartotheones

wehaveexploredinthispaperforWWANenvironments,havebeenalreadyextensively

exploredinthepriorliteraturemostlyinthecontextofwired(includingdial-up)

environments,e.g.CacheDigests,response-aliasinginwebtransactionsetc.A

detaileddescriptionofcachingschemesispresented.Similarly,deltaencodingisalso

awell-knownandusefultechniquetoimproveHTTPperformance.WebExpressfrom

83

IBMdefinessomeapplicationleveltechniques,includingcaching,differencing,and

header-reductionmechanisms,andisrelatedtosomeofthetechniquesexplored.In

thecontextofWWANenvironments,Liljeberget.al.developedMowgliCommunication

ArchitecturethatusesapairofproxiestoemployacustomprotocoltailoredfortheGSM

wirelesslink.Theirsolutionissimilarto(UDP-CDMA2000).TheWirelessApplication

Protocolisanotherrelatedmechanismthatemployexplicitproxies(optionalbuthighly

recommended)toimprovewebexperienceofWWANusers.Theoptimizationchoices

discussedcanbeappliedinthecontextofWAP2.0,specificallyforimprovements

suggestedin“wirelessprofiled”TCPandHTTP.

CDMAhasseenincrementalimprovementsincapacitythroughoutthisperiod.Now

bothtypesofnetworksaremakingatransitiontothird-generation(3G)systemsaround

theglobe,offeringyetmorecapacityanddataservices.Thisdescriptiondescribesthe


50

originsofCDMAtechnologyandtheemergenceof3Gimplementationssuchas

cdma20001Xandcdma20001xEV-DO.Anoverviewofnetworktopologyisincluded,

withadetailedexplanationoftheroleofeachelementandinterfaceinthenetworkand

ofprotocoltestingtoaddressthechangingrequirementsofthenetwork.Weconcludes

withadiscussionofsomeofthetechnicalproblemsthatcanoccurinCDMAnetworks

andsomeproposedsolutions.

DigitalRevolutionandEvolution

84

Whenthemobilecommunicationsindustrybeganitstransitionfromfirst-generation

analogtechnologytosecond-generation(2G)digitalarchitecture,manufacturersand

operatorschosesides:inEurope,frequency-hoppingGSMarchitecturebecamealmost

universal,whileintheU.S.,partsofAsia,andelsewhere,spread-spectrumCDMA

technologytookalargeshareofthemarket.Becausespreadspectrumuseswideband,

noise-likesignals,theyarehardtodetect.Theyarealsodifficulttointerceptor

demodulate.Further,spreadspectrumsignalsarehardertojam(interferewith)than

narrowbandsignals.TheseLowProbabilityofIntercept(LPI)andantijam(AJ)features

arewhythemilitaryhasusedspreadspectrumforsomanyyears.Bothnetwork

implementations,GSMandCDMA,haveadvancedtokeeppacewithsubscribers’

demandsformorebandwidth,featuresandreliabilityatlowercost.cdmaOneHelps

2GMobileCommunicationsTakeOffTheTelecommunicationsIndustryAssociation

(TIA/EIA)IS-95CDMAstandardpublishedestablishedthegroundrulesforacomplete

end-to-enddigitalwirelesscommunicationssystem.Thecommercialnetworksystem

architecturebasedonthisstandardisknownascdmaOne.TIA/EIAIS-95andthe

subsequentIS-95Arevisionformthebasisformostofthecommercial2GCDMA-based

networksdeployedaroundtheworld.Fromthestandpointofvoiceservices,cdmaOne

technologyoffersimportantfeaturesformobilenetworkoperators:

•An8Xto10XincreaseinvoicecapacityincreasecomparedtoanalogAMPS

systems

•Simplifiednetworkplanning,withthesamefrequencyusedineverysectorofevery

cell

Theearly2GCDMAinfrastructureproveditseffectivenessindeliveringhigh-quality,

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low-lossvoicetraffictosubscribers.Butitdidn’ttakelongformobileuserstobegin

askingforbasicdataservices,suchasInternetandIntranetservices,multimedia

applicationsorhigh-speedbusinesstransactions,tosupplementthevoiceserviceson

theirhandsets.TheTIA/EIAIS-95Astandardansweredthisdemandwithitsdefinitionof

thewideband1.25MHzCDMAchannels,powercontrol,callprocessing,hand-offsand

registrationtechniquesforsystemoperation.TIA/EIAIS-95Abroughttruecircuit-

switcheddataservicestoCDMAsubscribers;however,thesewerelimitedtoa

maximumspeedof14.4Kbpsperuser.


51

AsecondroundofrevisionstotheoriginalspecificationproducedtheTIA/EIAIS-95B

standard.Thisnewdevelopmentgavesubscriberspacket-switcheddataservicesat

speedsupto64Kbpspersubscriberinadditiontotheexistingvoiceservices.Withthis

increaseddatarate,TIA/EIAIS-95B-compliantnetworksqualifyas2.5GCDMA

technology.

CDMA2000TakestheNextStep

Thetransitionto3Gnetworks,stillunderway,beganwithaprofusionofnewlyproposed

standards.SomeweredesignedtobuildonGSMinfrastructuresandothersemerged

directlyfromCDMAtechnology.UltimatelytheITUtookapositiononthematter,

defininganIMT-2000standardthatencompassedfivedifferentradiointerfaces

includingcdma2000.NotethatalloftheIMT-2000protocolsusespread-spectrum

techniques,whichhasimplicationsaboutnetworkinstallation,operationand

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maintenance.

TheITUdefinesa3Gnetworkasonethatdelivers,amongothercapabilities,improved

systemcapacityandspectrumefficiencyversus2Gsystems.Itsupportsdataservices

attransmissionratesofatleast144Kbpsinmobile(moving)environmentsandatleast

2Mbpsinfixed(indoor)environments.Thecdma2000architecturemeetsthese

objectivesandincludesseveralimplementationsthatanoperatorcanselecttobest

serveatransitionstrategybasedoncompetitiveconcerns,existinginfrastructures,cost,

andothervariables.

Amongtheseimplementationsarecdma20001Xandcdma20001xEV:

-cdma20001XdoublesthevoicecapacityofcdmaOnenetworks,delivering

peakdataratesof307Kbpspersubscriberinamobileenvironment.

-cdma20001xEVincludestwovariants,bothbackwardcompatiblewith

cdma20001XandcdmaOnetechnologies.

-dma20001xEV-DO(DataOnly),capableofdeliveringdatamultimediaservices

suchasMP3transfersandvideo-conferencingatpeakdataratesof2.4Mbps

persubscriberinamobileenvironment;

-cdma20001xEV-DV(DataVoice),capableofdeliveringintegratedvoiceand

simultaneousdatamultimediaservicesatpeakdataratesof3.09Mbpsper

subscriber.

ANetworkStructureDesignedforPacketizedCommunication

TheMobileStation(MS).Inacdma20001Xnetwork,themobilestation—the

subscriber’shandset—functionsasamobileIPclient.Themobilestationinteractswith

theAccessNetworktoobtainappropriateradioresourcesfortheexchangeofpackets,

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52

anditkeepstrackofthestatusofradioresources(e.g.active,stand-by,dormant).It

acceptsbufferpacketsfromthemobilehostwhenradioresourcesarenotinplaceor

areinsufficienttosupporttheflowtothenetwork.Uponpower-up,themobilestation

automaticallyregisterswiththeHomeLocationRegister(HLR)

inorderto:

•Authenticatethemobilefortheenvironmentoftheaccessednetwork

•ProvidetheHLRwiththemobile’scurrentlocation

•ProvidetheServingMobileSwitchingCentre(MSC-S)withthemobile’spermitted

featuresetaftersuccessfullyregisteringwiththeHLR,themobileisreadytoplace

voiceanddatacalls.Thesemaytakeeitheroftwoforms,circuit-switcheddata(CSD)

orpacket-switcheddata(PSD),dependingonthemobile’sowncompliance(orlack

thereof)withtheIS-2000standard.Thisdocumentdefinesprotocolsforseveral

criticalCDMAinterfacespertainingtopackettransmission,namelyA1,A7,A9,and

A11.

MobileStationsmustcomplywithIS-2000standardstoinitiateapacketdatasession

usingthe1xRTT1network.MobilestationshavingonlyIS-95capabilitiesarelimitedto

CSD,whileIS-2000terminalscanselecteitherthePSDorCSD.Parametersforwarded

bytheterminalovertheairlink(AL)tothenetworkwilldeterminethetypeofservice

requested.Circuit-switcheddatahasamaximumrateof19.2Kbpsandisdelivered

overtraditionalTDMcircuits.Thisserviceallowsuserstoselectthepointofattachment

intoadatanetworkusingordinarydialleddigits.Packet-switcheddataservicehasa

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maximumdatarateof144Kbps.ForeachdatasessionaPoint-to-PointProtocol(PPP)

sessioniscreatedbetweenthemobilestationandthePacketDataServingNode

(PDSN).IPaddressassignmentforeachmobilecanbeprovidedbyeitherthePDSNor

aDynamicHostConfigurationProtocol(DHCP)serverviaaHomeAgent(HA).

TheRadioAccessNetwork(RAN)

TheRadioAccessNetworkisthemobilesubscriber’sentrypointforcommunicating

eitherdataorvoicecontent.Itconsistsof:

-Theairlink

-Thecellsitetower/antennaandthecableconnectiontotheBaseStation

TransceiverSubsystem(Um)

-TheBaseStationTransceiverSubsystem(BTS)

-ThecommunicationspathfromtheBaseStationTransceiverSubsystemtothe

basestationcontroller(Abis)

-TheBaseStationController(BSC)

-ThePacketControlFunction(PCF)


53

TheRANhasanumberofresponsibilitiesthatimpactthenetwork’sdeliveryofpacket

servicesinparticular.TheRANmustmapthemobileclientidentifierreferencetoa

uniquelinklayeridentifierusedtocommunicatewiththePDSN,validatethemobile

stationforaccessservice,andmaintaintheestablishedtransmissionlinks.TheBase

StationTransceiverSubsystem(BTS)controlstheactivitiesoftheairlinkandactsas

theinterfacebetweenthenetworkandthemobile.RFresourcessuchasfrequency

assignments,sectorseparationandtransmitpowercontrolaremanagedattheBTS.In

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addition,theBTSmanagestheback-haulfromthecellsitetotheBaseStationController

(BSC)tominimizeanydelaysbetweenthesetwoelements.NormallyaBTSconnects

totheBSCthroughun-channelizedT1facilitiesordirectcablesinco-locatedequipment.

TheprotocolsusedwithinthisfacilityareproprietaryandarebasedonHigh-levelData

LinkControl(HDLC).

TheBaseStationController(BSC)routesvoice-andcircuit-switcheddatamessages

betweenthecellsitesandtheMSC.Italsobearsresponsibilityformobilitymanagement:

itcontrolsanddirectshandoffsfromonecellsitetoanotherasneeded.Itconnectsto

eachMTXusingchannelizedT1linesforvoiceandcircuitswitcheddata;andtoun-

channelizedT1linesforsignallingandcontrolmessagestothePDSNusingthe

10BaseTEthernetprotocol.ThePacketControlFunction(PCF)routesIPpacketdata

betweenthemobilestationwithinthecellsitesandthePacketDataServingNode

(PDSN).Duringpacketdatasessions,itwillassignavailablesupplementalchannelsas

neededtocomplywiththeservicesrequestedbythemobileandpaidforbythe

subscribers.Anetworkthatprovidesa“1xchiprateof1.2288McpsforRadio

TransmissionTechnology.”

ThePCFmaintainsa“reachable”stateforbetweentheRNandthemobilestation,

ensuringaconsistentlinkforpackets;bufferspacketsarrivingfromthePDSNwhen

radioresourcesarenotinplaceorinsufficienttosupporttheflowfromthePDSN;and

relayspacketsbetweentheMSandthePDSN.

TheCoreNetwork’sRoleintheCDMAInfrastructure

ThePacketDataServingNode/ForeignAgent(PDSN/FA)ThePDSN/FAisthegateway

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fromtheRANintothepublicand/orprivatepacketnetworks.InasimpleIPnetwork,the

PDSNactsasastandaloneNetworkAccessServer(NAS),whileinamobileIPnetwork

itcanbeconfiguredasaHomeAgent(HA)oraForeignAgent(FA).

ThePDSNdoesthefollowingactivities:


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-Managetheradio-packetinterfacebetweentheBSS(BaseStationSubsystem

=BTS+BSC)andtheIPnetworkbyestablishing,maintainingandterminating

linklayertothemobileclient

-TerminatethePPPsessioninitiatedbythesubscriber

-ProvideanIPaddressforthesubscriber(eitherfromaninternalpoolorthrough

aDHCPserverorthroughanAAAserver;seebelow)

-Performpacketroutingtoexternalpacketdatanetworksorpacketroutingtothe

HAwhichoptionallycanbeviasecuretunnels

-Collectandforwardpacketbillingdata

-Activelymanagesubscriberservicesbasedontheprofileinformationreceived

fromtheSCSserveroftheAAAserver

-Authenticateuserslocally,orforwardauthenticationrequeststotheAAAserver

TheAAAServer

TheAAA(Authentication,Authorization,andAccounting)serverisusedtoauthenticate

andauthorizeusersfornetworkaccessandtostoresubscriberusagestatisticsfor

billingandinvoicing.

TheHomeAgent

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TheHomeAgent(HA)supportsseamlessdataroamingintoothernetworksthatsupport

1xRTT.TheHAprovidesananchorIPaddressforthemobileandforwardsanymobile-

boundtraffictotheappropriatenetworkfordeliverytothehandset.Italsomaintains

userregistration,redirectspacketstothePDSNand(optionally)tunnelssecurelytothe

PDSN.Lastly,theHAsupportsdynamicassignmentofusersfromtheAAAand(again

optionally)assignsdynamichomeaddresses.

DetectingandSolvingSomeCommonProblemsincdma20001X

Networks

Allofthefeaturesandcapacitiesembodiedinthemodern3Gmobilenetworkmakefor

acomplexsystemwithmanymodes,nodes,elements,interfaces,andprotocols.

Problems,whentheyarise,mayhavetheiroriginsineitherhardwareorsoftware.As

mobileInternetconnectivitybecomescommon,thechallengeofmaintaining

uninterrupteddatatransactionswillrequirenew,morepowerfulmonitoringsolutions

andprocedures,amongotherthings.Inthissection,wewillexaminesomecommon

problemsthatcanoccurincdma20001Xnetworks.FailureinMobileInitiatedPacket

DataCallSet-upandMobileIPRegistrationinordertoobtainpacketdataservices,the


55

mobileperformsregistrationwiththeservingwirelessnetworkontheA1interfaceand

thenwiththepacketnetworkontheA10/A11interface.ThemobilesendsanOrigination

MessagetotheBSthatincludesthepacketdataserviceoption.Thisresultsin

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assignmentofthetrafficchannel,establishmentoftheA10connection,establishment

ofthelinklayer(PPP)andforthecasewhereMobileIPisusedbytheterminal,Mobile

IPregistrationwiththeservingpacketnetwork.Userdatatrafficcannowbepassed

overtheA10connectionencapsulatedwithinGREframes.

ThePCFperiodicallyre-registerswiththeselectedPDSNbysendingtheA11

RegistrationRequestmessagebeforetheA10connectionLifetimeexpires.A

successfulcallset-upscenarioisillustratedinFigure2.Thisstandardmessage

sequencechartoutlinesaseriesofsteps,summarizedinitems1-12tofollow.Notethat

thisexplanationbypassestheradioreception/transmissionactivitiesoftheBTS,

concentratinginsteadontheprotocolfunctionsthatbeginwiththeOriginationdialogue

betweenthemobileandtheBSC.

1.Toregisterforpacketdataservices,themobilesendsanOriginationMessage

overtheAccessChanneltotheBSS

2.TheBSacknowledgesthereceiptoftheOriginationMessage,returningaBase

StationAckOrdertothemobile

3.TheBSconstructsaCMServiceRequestmessageandsendsthemessageto

theMSC.

4.TheMSCsendsanAssignmentRequestmessagetotheBSSrequesting

assignmentofradioresources.NoterrestrialcircuitbetweentheMSCandthe

BSisassignedtothepacketdatacall.

5.TheBSandthemobileperformradioresourceset-upprocedures.

ThePCFrecognizesthatnoA10connectionassociatedwiththismobileis

availableandselectsaPDSNforthisdatacall.

6.ThePCFsendsanA11-RegistrationRequestmessagetotheselectedPDSN.

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7.TheA11-RegistrationRequestisvalidatedandthePDSNacceptsthe

connectionbyreturninganA11-RegistrationReplymessage.

BoththePDSNandthePCFcreateabindingrecordfortheA10connection.

8.AftertheradiolinkandA10connectionareset-up,theBSsendsanAssignment

CompletemessagetotheMSC

9.ThemobileandthePDSNestablishthelinklayer(PPP)connectionandthen

performtheMIPregistrationproceduresoverthelinklayer(PPP)connection.

10.AftercompletionofMIPregistration,themobilecansend/receivedataviaGRE

framingovertheA10connection.

11.ThePCFperiodicallysendsanA11-RegistrationRequestmessagefor

refreshingregistrationfortheA10connection.


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12.ForavalidatedA11-RegistrationRequest,thePDSNreturnsanA11-Registration

Replymessage.BoththePDSNandthePCFupdatetheA10connectionbinding

record.

Thisnecessarilycomplexprocesscanbethesourceofsomeproblemsthataffect

serviceandquality.Arigorousmonitoringschemeinvolvingsimultaneousobservation

oftheA1interfaceandtheA10/A11interfaceisthebestwaytodetectandcorrecterrors

early.Here,amulti-interfacecall-traceapplicationisespeciallyproductive,sinceitcan

traceandgroupalloftheproceduresrelatedtotheactivityofeachsinglesubscriberin

aCDMAnetwork,evenastheproceduresevolveovermultipleinterfaces.

Withinthecallset-upprocess,anerrorinanyelementorproceduralstepcaninhibitthe

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remainingsteps.Forexample,supposethattheMSCdoesnotrespondtotheCM

ServiceRequestmessage(Step3)sentbytheBSC/PCFovertheA1interface.Thisis

sometimescausedbyinternalMSCproblems.IfthispreventstheCMServiceRequest

fromreachingcompletion,theBSC/PCFcannotassignradioresourcestothemobile

station,inturnpreventingestablishmentoftheconnection.Theuserfindsitimpossible

tomakeadatacall—aserviceforwhichheorshehaspaidapremium.

Beforeaspecifictimerexpires,thePCFsendsperiodicallyA11-RegistrationRequest

message(Step11)torefreshtheregistrationfortheA10connection.Foravalidated

A11-RegistrationRequest,thePDSNreturnsanA11-RegistrationReplymessage(Step

12).Hereagain,internalproblemsinthePDSNcancauseittorespondlateornotatall.

Asaresulttheprocessofestablishingormaintainingtheconnectioncannotcontinue.

Theuserisonceagainunabletomakeadatacall.

Inbothcases,aprotocolanalyzerconnectedtotheA1andA10/A11interfacescan

helptrackdowntheproblem.Thecalltraceapplicationcandistinguishtheoriginof

messagesanddetectanyfailuretorespond.ThismakesiteasytopinpointtheMSC

andthePDSN,respectivelyintheseexamples.

ØInefficiencyinUserDataPacketTransmission

Frequentlyinacdma2000networktheTCPuser-planepacketshaveasmallWindow

Size.Thisimpliesthatend-to-endTCPconnectionsarenotstable.ThemoreTCP

packetslostinthenetworkandnotacknowledged,thesmallertheWindowSize,with

theresultthatmoreTCPconnectionsaredroppedandre-established.ThesmallTCP

WindowSizeisaby-productofthesoft-startmechanismbuiltintotheTCPprotocol.

Tocharacterizethisproblem,itisnecessarytocapturetheTCP/IPuserplanepackets

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flowingontheGREtunnelsontheA10interface.Protocolfilteringallowsthetoolto

homeinonjustthedataorinterest.Byapplyingdifferenttypesoffilteringwithincreasing


57

levelofdetails,itispossibleto“drilldown”andisolatetherootcauseoftheshrinking

TCPpacketWindowSize.RoutingLoopsofUserDataPacketsintheCoreNetwork

“Tunnelrouterloops”areanotherclassofcdma2000networkproblemsthatcan

degradethequalityofserviceforsubscribers.Theproblemiscausedby

misconfigurationinthePDSNrouters.ItcanbedetectedbyacquiringandanalyzingIP

trafficontheP-Hinterface.

Tounderstandtunnelrouterloops,imagineasubscribersurfingtheWeb(WWW)with

alaptopconnectedtoacdma2000handset.Packetsaddressedtogotoaspecific

HTTPproxyarerouted(afterpassingthroughthePCF)fromthePDSN/FA(Foreign

Agent)totheHomeAgent(HA)forde-tunneling.Withcertainincorrectinternalrouting

configurations,packetsdestinedforPort80WWWarenotde-tunnelledbytheHA.

Instead,theyaresentbackdownstreamtowardthePDSN/FA.Asaresult,multiple

packetstravelonthesamenetworksegmentwiththesamepacketID,wastingprecious

bandwidth—andnotreachingtheintendeddestination.Inaddition,foreachrepetitive

hopapackettakesbetweenthePDSN/FAandHAnodes,theIPTimeToLive(TTL)field

isdecremented.Ifthepacketisstuckinarouterloop,theTTLeventuallydecrements

allthewaytozeroandthepacketisdiscardedbythenetworknodes.“Lost”packets

mustberetransmitted,leadingtoexcessivepacketretransmissionoverheadand

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reducedthroughput.

Asintheearlierexamples,thesolutionistouseprotocolfilteringtocaptureIPpackets

onthePHinterface.Browsingthroughthecaptureddatabyapplyingincreasinglyfine

levelsoffiltering,itispossibletoseetherepeatingpacketsandresolvetheproblem.

ØDuplicationofIPtraffic

PDSNconfigurationproblemscangiverisetoothertypesofproblemsinadditionto

tunnelloops.OnecommonissueisassociatingthePDSNślogicalIPaddresseswith

morethanonephysicalMACaddress.Whenthisoccurs,morethanonehardwarecard

hasthesameIPaddress.AlltrafficsenttothatIPaddressgoestotwodifferent

hardwareentitiesandreceivesresponsesfromboth.Thiseffectivelydoublesthe

amountofIPtrafficassociatedwiththatsingleIPaddressonthatsegment.Onceagain,

protocolfilteringcapabilitiesarerequiredforeffectivetroubleshooting.

AprotocolanalyzershouldcaptureIPpacketstravellingtoaspecificIPdestination

addressviatheP-Hinterface.Browsingthroughthedataandusingfilteringto

successivelynarrowdowntheinquiry,thenatureoftheproblem(theduplicated

address)soonbecomesapparent.


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ØRoutingproblemsintheCoreNetwork

SometimesinternalproblemscancausePDSNrouterstogoofflineandcomeback

onlineafteraperiodoftime.Thiscanhappenfrequentlyandcontinuouslyina

cdma2000coredatanetwork.Whenarouterfirstcomesonlineitsroutingtablearenot

optimized.Ittakestimeforthebuilt-inOSPF(OpenShortestPathFirst)routingalgorithm

tolearnthebestwaytoroutepacketsdependingonadjacentavailablerouters.Until

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theroutingtablesareoptimized,therewillbedegradationinqualityofservice.By

capturingIPpacketsontheP-Hinterfacewithaprotocolanalyzerandapplyingfilters

ontheOSPFroutingmessages,changesindesignatedrouterandchangesin

neighboursofaroutercanbeeasilyidentified.Usingintelligentanddetailedfiltering

capabilityonOSPFmessagesandinformationelementswithinthesemessages

identifyingroutingproblemsonanIPnetworkbecomesaneasytask.

ThroughputOptimization

ØTrafficandMobilityModel

A.FeasibleStates

TheredoesnotexistamongresearchersaunanimousconsensusonwhethertheCDMA

systemcapacityisreverseorforwardlinklimited.However,themajorityoftheliterature

publishedonthesubjectisoftheformerview.Inlightofthis,inthispaperweconsider

thereverselinkcapacityonly.Consideramulti-cellCDMAnetworkwithspreadsignal

bandwidthofW,informationrateofRbits/s,voiceactivityfactorofA,andbackground

noisespectraldensityofNo.Toachievearequiredbiterrorratewemusthave(Eb/Io)

>=SforsomeconstantS.AssumingatotalofMcellswithnicallsincelli,thenumber

ofcallsineverycellmustsatisfy

ni+(MXj=1)nj_ji<=W/R/A(1/S–1/Eb/No)+1=ceff,

fori=1,...,M.(1)

whereji=Iji/njistheperuserinter-cellinterferencefactorfromcelljtocelli,andwhere

Ijidenotestherelativeaverageinterferenceofcelljtocelli.

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Asetofcallsn=(n1,...,nM)satisfyingtheaboveequationsissaidtobeafeasiblecall

configurationorafeasiblestate,i.e.,onethatsatisfiestheEb/Ioconstraint.Theright

handsideof(1)isaconstantwhichisdeterminedbysystemparametersandbythe

desiredmaximumbiterrorrate,andcanberegardedasthetotalnumberofeffective


59

channels,ceff,availabletothesystem.Denotebythesetoffeasiblestates.Definethe

setofblockingstatesforcellias

Bi={n2:(n1,...,ni+1,...,nM)62}.(2)

Ifanewcallorahandoffcallarrivestocelli,itisblockedifthecurrentstateofthenetwork,n,isinBi.Thecallblockingprobabilityforcelli,Bi,istheprobabilitythatn2

Bi.

B.MobilityModel

ThecallarrivalprocesstocelliisassumedtobeaPoissonprocesswithrate_i

independentofothercallarrivalprocesses.Thecalldwelltimeisarandomvariable

withexponentialdistributionhavingmean1/µ,anditisindependentofearlierarrival

times,calldurationsandelapsedtimesofotherusers.Attheendofadwelltimeacall

maystayinthesamecell,attemptahandofftoanadjacentcell,orleavethenetwork.

Letqijbetheprobabilitythatacallinprogressincelliaftercompletingitsdwelltime

goestocellj.Ifcellsiandjarenotadjacent,thenqij=0.Defineqiiastheprobability

thatacallinprogressincelliremainsincelliaftercompletingitsdwelltime.Inthis

caseanewdwelltimethatisindependentofthepreviousdwelltimebeginsimmediately.

Wedenotebyqitheprobabilitythatacallinprogressincellidepartsfrom

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thenetwork.Thismobilitymodelisattractivebecausewecaneasilydefinedifferent

mobilityscenariosbyvaryingthevaluesoftheseprobabilityparameters.Forexample,

ifqiisconstantforalli,thentheaveragedwelltimeofacallinthenetworkwillbe

constantregardlessofwherethecalloriginatesandwhatthevaluesofqiiandqijare.

Thusinthiscase,byvaryingqii’sandqij’swecanobtainlowandhighmobility

scenariosandcomparetheeffectofmobilityonnetworkattributes(e.g.,throughput).

LetAibethesetofcellsadjacenttocelli.Let_jibethehandoffrateoutofcelljoffered

tocelli._jiisthesumoftheproportionofnewcallsacceptedincelljthatgotocelli

andtheproportionofhandoffcallsacceptedfromcellsadjacenttocelljthatgotocell

i.

Thus_ji=_j(1-Bj)qji+(1-Bj)qjiXx2Aj_xj.(3)

Equation(3)canberewrittenas_ji=_(Bj,_j,qji)=(1-Bj)qji_j,(4)

where_j,thetotalofferedtraffictocellj,isgivenby

_j=_(v,_j,Aj)=_j+Xx2Aj

_xj,(5)


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andwherevdenotesthematrixwhosecomponentsarethehandoffrates_ijfori,j=

1,...M.Thetotalofferedtrafficcanbeobtainedfromafixedpointmodel,which

describestheofferedtrafficasafunctionofthehandoffratesandnewcallarrivalrates,

thehandoffratesasafunctionoftheblockingprobabilitiesandtheofferedtraffic,and

theblockingprobabilitiesasafunctionoftheofferedtraffic.Foragivensetofarrival

rates,weuseaniterativemethodtosolvethefixedpointequations.Wedefineaninitial

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valueforthehandoffrates.Wecalculatetheofferedtrafficbyaddingthegivenvalues

ofthearrivalratestothehandoffrates.Theblockingprobabilitiesarenowcalculated

usingtheofferedtraffic.Wethencalculatethenewvaluesofthehandoffratesand

repeat.

C.AdmissibleStates

Acallarrivingtocelliisacceptedifandonlyifthenewstateisafeasiblestate.Clearly

thisrequiresglobalstate,i.e.,thenumberofcallsinprogressinallthecellsofthe

network.Furthermore,tocomputetheblockingprobabilities,theprobabilityofeach

stateinthefeasibleregionneedstobecalculated.SincethecardinalityofisO(ceffM),

thecalculationoftheblockingprobabilitieshasacomputationalcomplexitythatis

exponentialinthenumberofcells.

Inordertosimplifythecalladmissionprocess,weconsideronlythosewhichrequire

localstate,i.e,thenumberofcallsinprogressinthecurrentcell.Tothisendwedefine

astatentobeadmissibleif

ni_Nifori=1,...,M,(6)

whereNiisaparameterwhichdenotesthemaximumnumberofcallsallowedtobe

admittedincelli.Clearlythesetofadmissiblestatesdenoted0isasubsetofthesetof

feasiblestates.Theblockingprobabilityforcelliisthengivenby

Bi=B(Ai,Ni)=ANi

i/Ni!NiPk=0

Aki/k!,(7)

whereAi=_i/µi=_i/µ(1-qii).Wenotethatthecomplexitytocalculatetheblocking

probabilitiesin(7)isO(M),andthebiterrorraterequirementisguaranteedsince0_.

ThroughputOptimization

101

Thethroughputofcelliconsistsoftwocomponents:thenewcallsthatareacceptedin

celliminustheforcedterminationduetohandofffailureofthehandoffcallsinto

celli.Hencethetotalthroughput,T,ofthenetworkisT(B,_,_)=MXi=1{_i(1-Bi)-Bi(_i

-_i)},=MXi=1{_i-Bi_i},(8)


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whereBisthevectorofblockingprobabilities,_isthevectoroftotalofferedtraffic,and

_isthevectorofcallarrivalrates.Weformulateaconstrainednonlinearoptimization

probleminordertomaximizethethroughputsubjecttoupperboundsontheblocking

probabilitiesandalowerboundonthesignalto-interferenceconstraintsin(1).Thegoal

istooptimizetheusageofnetworkresourcesandprovideconsistentgrade-ofservice

(GoS),i.e.,thecallblockingrate,forallthecellsinthenetworkwhileatthesametime

maintainingthequality-ofservice(QoS),i.e.,theprobabilityoflossofcommunication

quality,foralltheusers.Intheoptimizationproblemthearrivalratesandthemaximum

numberofcallsthatareallowedtobeadmittedinthecellsaretheindependent

variables.Thisisgiveninthefollowing

max

(_1,...,_M),(N1,...,NM)

T(B,_,_),subjecttoB(Ai,Ni)__,

Ni+MXj=1Nj_ji_ceff,

fori=1,...,M,(9)

Theoptimizationproblemin(9)isamixedintegerprogramming(MIP)problem.One

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techniquetosolvetheMIPproblemisbasedondividingtheproblemintoanumberof

smallerproblemsinamethodcalledbranchandbound.Branchandboundisa

systematicmethodforimplicitlyenumeratingallpossiblecombinationsoftheinteger

variablesinamodel.Thenumberofsubproblemsandbranchesrequiredcanbecome

extremelylarge.ByrelaxingtheintegervariablesNi,i=1,...,M,tocontinuousvariables,

theoptimizationin(9)issolvedusingaSequentialQuadraticProgramming(SQP)

method.Inthismethod,aQuadraticProgrammingsubproblemissolvedateach

iteration.Asolutiontothefixedpointequationsiscalculatediteratively.Anestimateof

theHessianoftheLagrangianisupdatedateachiterationusingtheBroyden-Fletcher-

Goldfarb-Shanno(BFGS)formula.Alinesearchisperformedusingameritfunction.The

QuadraticProgrammingsubproblemissolvedusinganactivesetstrategy.Inorderto

usetheSQPmethod,weneedtoevaluatethederivativesofTwithrespecttoNand_.

T(B,_,_)isanimplicitfunctionofN=(N1,...,NM)and_.Wecanobtainrelationsoftotal

andpartialderivativesofthethroughputbydifferentiatingthefixedpointequations.

Theserelationsaremanipulatedtoobtainasystemoflinearequationsinthederivatives

oftheofferedtrafficwithrespecttothenumberofcallsadmittedandthearrivalrates.

Wecalculatetheimpliedcost,i.e.,thederivativeofTwithrespecttotheimplicitvariable

N.ThecalculationoftheimpliedcostofTwithrespecttothenew-callarrivalratesis

givenintheAppendix.


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103

NumericalResults

Thebasestationsarelocatedatthecentersofahexagonalgridwhoseradiusis1732

meters.Basestation1islocatedatthecenter.Thebasestationsarenumbered

consecutivelyinaspiralpattern.TheCOST-231propagationmodelwithacarrier

frequencyof1800MHz,averagebasestationheightof30meters,andaveragemobile

heightof1.5metersisusedtodeterminethecoverageregion.Weassumethefollowing

fortheanalysis.Thepathlosscoefficientis4.Theshadowfadingstandarddeviationis

6dB.Theprocessinggainis21.1dB.Thebitenergytointerferenceratiothreshold,_,

is9.2dB.Theinterferencetobackgroundnoiseratiois10dB.Thevoiceactivityfactor

is0.375.Formoredetailsonthechoiceoftheseparametersreferto.Peruserinter-cell

interferencefactorsareevaluatednumericallybydividingthewholeareaintosmall

gridsofsize150mby150m.Theblockingprobabilitythreshold,_,issetto0.02.

Weconsiderthreemobilityscenarios:nomobility,lowmobility,andhighmobilityof

users.Thefollowingprobabilitiesarechosenforthenomobilitycase:qij=0,qii=0.3

andqi=0.7forallcellsiandj.Forthelowandhighmobilitycase,themobility

probabilityparametersaregiven.Inallthreecases,theprobabilitythatacallleavesthe

networkaftercompletingitsdwelltimeis0.7.Thus,theaveragedwelltimeofacallin

thenetworkisconstantregardlessofwherethecalloriginatesandthemobilityscenario

used.

Inthefollowing,wecompareourresultstoacalladmissioncontrolalgorithmwherethe

maximumnumberofcallsthatcanbeadmittedineachcellisthesame,i.e.,N1=N2

=

104

...=NM=N(irrespectiveofthecallarrivalrateprofileinthenetwork).Wealsooptimize

therevenueforthisalgorithmsubjecttoalowerboundonthebitenergytointerference

ratio.Inthesequel,theoptimizedalgorithmisreferredtoasa

traditionalcalladmissioncontrol(CAC)algorithm.Notethat

LOWMOBILITYPROBABILITIES.

kAikqijqiiqi

30.0200.2400.700

40.0150.2400.700

50.0120.2400.700

60.0100.2400.700

HIGHMOBILITYPROBABILITIES

kAikqijqiiqi

30.1000.0000.700

40.0750.0000.700


63

50.0600.0000.700

60.0500.0000.700

•kAikisthenumberofcellsadjacenttocelli.

•qijistheprobabilityacallincelligoestocellj.

•qiiistheprobabilityacallincellistaysincelli.

•qiistheprobabilityacallincellileavesthenetwork.Thisalgorithmwillbeoptimal

inthesenseof(9)inthecaseofequalcallarrivalrates,equalmobilityprobabilities

105

forallthecells,andanetworkwithalargenumberofcells(inwhichedgeeffects

canbeignored).

Wechoosethecallarrivalratestobeequalto_callsperunittimeforallcellsexcept

thoseinGroupA(i.e.,cells5,13,14,and23)andGroupB(i.e.,cells2,8,9,and19).

ForGroupsAandBthecallarrivalratesareequalto5_callsperunittime.Thetotal

offeredtrafficpercell(thesumofthecallarrivalrateandthehandoffrate)isshownin

bracketsforthenomobility,lowmobility,andhighmobilitycases.Themaximum

numberofcallsthatcanbeadmittedineachcell,calculatedfromequation(9),isshown

inparenthesesinthesamefigures.ForthetraditionalCACalgorithmwiththesame

blockingprobabilitythreshold,systemparameters,andthebitenergytointerference

ratiorequirement,themaximumnumberofcallsthatcouldbeadmittedineachcell

wouldbe18.Inouralgorithmforthenomobilitycase,itcanbeseenthatforthecells

belongingtoGroupsAandBthemaximumnumberofcallsadmittedhasincreased

from18to22-24,whileforallothercellsithasdecreasedfrom18to7-9.Itcanbeseen

thatouralgorithmtradesoffthecallsinthecellswithlowarrivalrateforthecallsinthe

cellswithhigharrivalrate.Asthemobilitymodelchangesfromnomobilitytohigh

mobility,thehandoffratesincreasethusincreasingthetotalofferedtrafficpercell.For

thehighmobilitycase,themaximumnumberofcallsadmittednowrangesfrom20to

23forcellsbelongingtoGroupsAandB,andfrom7to11forallothercells.

ThethroughputofeachcellresultingfromouralgorithmandthetraditionalCAC

algorithmforthenomobility,lowmobility,andhighmobilitycasesaregiveninFigures

4,5,and6,respectively.Inthesefigures,thecircleandstaratthetwoendsofavertical

106

barindicatesthethroughput.Totalofferedtrafficandmaximumnumberofcallsallowed

tobeadmittedpercellforthetwenty-sevencellCDMAnetworkwithnomobilityofusers,

thetraditionalCACalgorithmandouralgorithm,respectively,forthecellwhoseidis

shownonthehorizontalaxis.ThetraditionalCACalgorithmhasatotalnetwork

throughputequalto96.03,99.08,and102.43callsperunittimeforthenomobility,low

mobility,andhighmobilitycases,respectively.Ouroptimizationincreasesthe

throughputforthenetworkto127.02,131.40,and136.52callsperunittimefortheno

mobility,lowmobility,andhighmobilitycases,respectively,whichisa32%increasein

throughputoverthetraditionalCACalgorithmforthesameguaranteedblocking


64

probabilitythresholdof0.02.Thevalueof_calculatedfrom(9)increasesfrom1.65(in

thetraditionalCACalgorithm)to2.19callsperunittime(inouroptimization)fortheno

mobilitycase,from1.70to2.27callsperunittimeforthelowmobilitycase,andfrom

1.75to2.37callsperunittimeforthehighmobilitycase.Duetoitscalltrade-offs

betweenlowandhightrafficcells,thisalgorithmisabletobetteraccommodatethe

unequalcallarrivalratesinthenetworkandachievehigherthroughputinallthecells

forthesameguaranteedGoS.

CALCULATIONS

CalculationoftheImpliedCostw.r.t._

Inwhatfollowswedeterminetheimpliedcostofthethroughputwithrespecttothenew-

107

callarrivalrates.Thetotalderivativeofthethroughputfunctionwithrespecttoanew-

callarrivalrateisgivenby

dT(B,_,_)d_k=1+MXi=1_@T(B,_,_)@Bi

dB(Ai,Ni)d_k+@T(B,_,_)@_i

d_(v,_i,Ai)

d_k_.(10)

Thepartialderivativesneededare@T(B,_,_)@Bi

=-_i,(11)and

@T(B,_,_)@_i=-Bi.(12)

ThenwegetdB(Ai,Ni)

d_k=@B(Ai,Ni)@Ai@Ai@_i

d_(v,_i,Ai)d_k

Totalofferedtrafficandmaximumnumberofcallsallowedtobeadmittedpercellfor

thetwenty-sevencellCDMAnetworkwithhighmobilityofusers.Maximumthroughput

ineverycellforthenetwork.

Thetotalderivativeneededin(13)and(10)canbeobtainedfrom(5)asfollows

d_(v,_i,Ai)d_k=Xx2Ai

@_(v,_i,Ai)@_xi

d_(Bx,_x,qxi)d_k+@_(v,_i,Ai)

@_k,(14)

where@_(v,_i,Ai)

@_k

=I{i=k}.From(5)weget@_(v,_i,Ai)@_xi

=I{x2Ai}.Finally,from(4),thederivativeofthehandoffratewithrespecttothecallarrival

108

rateisgivenby

d_(Bx,_x,qxi)d_k


65

=@_(Bx,_x,qxi)

@Bx

dB(Ax,Nx)

d_k+@_(Bx,_x,qxi)

@_xd_(v,_x,Ax)d_k.

Thepartialderivativesneededin(15)areobtainedasfollows

@_(Bx,_x,qxi)@Bx

=-qxi_x,(16)

@_(Bx,_x,qxi)@_x

=(1-Bx)qxi.(17)

Thesetofsimultaneouslinearequationscanbesolvedandtheresultssubstitutedback

in(10)alongwithequations(11)and(12).Thiscompletesthederivationoftheimplied

costandthevaluesofthederivativesofthethroughputwithrespecttothecallarrival

rates.Impliedcostscapturetheeffectofincreasesinthecallarrivalrateinonecellon

thethroughputoftheentirenetwork.

RESULTS

Theoptimizationofnetworkthroughputwasoneofthemainresultsthatpresentedin

thisproject.

-Somemobileoperatorshaveaddressedtheproblemofjointlycontrollingthedata

ratesandtransmitpowersoftheusers,soastomaximizethethroughput.They

109

formulateaclassicaloptimizationproblem,modelingtheconstraintsarisingfromthe

dataraterequirementsandpowerbudgets.

-Othersformulatethethroughputmaximizationproblemintermsofthespreadinggains

andtransmitpowersoftheusers,andsolveitusinganonlinearprogrammingapproach.

-Othersinvestigatethemaximumthroughputthatcanbeachievedthroughjointrate

andpoweradaptationinamulti-rateCDMAsystem.Theyassumeconventional

matchedfilterdetectionwithperfectchannelinformationandaninstantaneousBER

constraint.Theyrestricttheirattentiontomulticodeormultipleprocessinggainschemes.

Also,somecompaniesworksolutionsforthroughputoptimizationofdatatrafficfora

powerconstrainedvoice/dataCDMAsystembyschedulingofdatausers.Itwasfound

thatunderagivenreceivedpowerbudgetandtheconstraintsoftransmissionpowers,

thethroughputofdatatrafficismaximizedbyselectingsimultaneousdatausersand

allocatingpowersaccordingtothedescendingorderoftheirreceivedpower


66

capabilities,whichisdefinedastheproductbetweenthetransmissionpowerlimitand

thechannelgain.Inthispaper,weformulateaconstrainedoptimizationproblemthat

maximizesthenetworkthroughputsubjecttoupperboundsonthecallblocking

probabilitiesandalowerboundonthebitenergytointerferenceratio.Wecalculatethe

impliedcosts,whicharethederivativesofthethroughputfunction,andcapturethe

effectofincreasesinthecallarrivalratesinonecellonthethroughputoftheentire

network.Wealsotakemobilityofusersintoaccountanddifferentiatebetweenthe

110

blockingofnewcallsandtheblockingofhandoffcalls.Theblockingprobabilitiesare

givenbythefixedpointmodel,whichdescribestheblockingprobabilitiesasafunction

ofthetotalofferedtraffic,thetotalofferedtrafficasafunctionofthecallarrivalrates

andthehandoffrates,andthehandoffratesasafunctionoftheblockingprobabilities

andthetotalofferedtraffic.Weobtainrelationsofthetotalandpartialderivativesofthe

blockingprobabilitiesbydifferentiatingthefixedpointrelations.Thesearethenused

alongwiththeimpliedcostsinthesolutiontoourthroughputoptimizationproblem.

CONCLUSIONS

Weconductedadetailedcomparativeperformancestudyofawideselectionof

optimizationschoicesapplicableforWWANs.Oursisthefirstsignificantstudytohave

attemptedtoaddressimportantquestionslike:Whydowebusersexperiencepoor

performanceoverWWANs?EventhoughTCPisrelativelywell-tunedtoperform

efficientlyintheseenvironments,whyistheperformanceofHTTPapplications

significantlyworse?WhilepriorstudieshaveexaminedtheproblemsofTCPinWWAN

environments,wearenotawareofanypriorresearchthatpresentsadetailedevaluation

ofapplicationperformance.Ourperformancestudyalsoprovidesimportantinsightsin

understandingwhatoptimizationchoicescanyieldhowmuchbenefit.Theperformance

optimizationsappliedateachindividuallayerstudiedinthispaper,leveragewell-

adaptedandoptimizedlowerlayers.Thisavoidsanyinefficientcross-layerdesign

includingadverseinter-layerinteractions.

Thefollowingaresomeofourimportantobservations:SevereMismatchbetweenTCP

andHTTP:ThereisasignificantmismatchintheperformanceofdefaultHTTP

111

protocols

anditsunderlyingtransportmechanismTCPinWWAN.Unlikethewired(e.g.dial-up)

environments,wefindthatstandardwebbrowsersdonotexploitthemeagreresources

oftheWWANlinks.Theachievedthroughputissometimes70%lowerthantheideal

downlinkdatarate.

ApplicationsandSessionLayersDominateBenefits:Significantbenefitstoend-user

experiencecanberealized(about48-61%improvements)bysuitableoptimizations

implementedattheapplicationandsessionlayers.UseofProxyBeneficial:Proxy-


67

basedsolutionsaremosteffectiveinimprovingapplicationperformancethannon-proxy

basedapproaches.

Ourperformancestudyhasbroadimplications.Theadditionalbenefitsresultingfrom

usingHTTPpipelininghighlightstheneedtomitigatetheimpactofhighandvariable

WWANlinklatencybyimplementingthisfeatureinallcommercialclasswebservers

andstandardwebbrowsers.Henceappropriatesupportfromwebservervendors,

contentprovidersandbrowserdesignerswillgoalongwayinthesuccessofthenext

generation‘mobile’Internet.Wefindthatacollectivesuiteofperformanceoptimizations

implementedusingproxiesatdifferentlayersinmanycasescanreducetheresponse

timebyatleastafactoroftwo.Thisispossiblebecausetheproxiesarespecifically

awareofthecharacteristicsoftheWWANenvironmentandhencemakesmore

‘intelligent’decisionstoadapttheperformanceofdatadeliverymechanisms.Such

awarenessoflinkcharacteristicsiscrucialforimprovingtheoverallenduser-

112

experience.Thiscanimplyanyoneofthefollowingtwothings:

(1)Proxy-basedsolutionsshouldnotberestrictivelyviewedasashort-termsolution.

Instead,cellularoperatorsshoulddesign,implementanddeploysuchproxysolutions

withintheirnetworkandend-usersshouldbegiventhechoicetousesuchproxies,thus,

tradingoffsecuritywithperformance.Suchanapproachmaybeacceptableincertain

scenarios.

(2)Theintelligenceoftheproxiesshouldbeimplementedinthewebservers,content

providers,aswellasthewebbrowsers.Suchanapproachwillmaintain“end-toend”

nessoftheprotocols,however,willrequiresignificantcollaborativeeffortbetweenall

thesediversevendorsofdifferentapplications.

Otherthanperformance,itisimportanttoconsiderthetrade-offsbetweenthecostand

theeaseofdeploymentassociatedwithsuchproxyinstallations.Aspreviously

discussedinourstudy,transparentproxiesaretheeasiesttodeploysincetheyrequire

nochangesorconfigurationtothemobileclients.However,fromaperformance

perspective,dual-proxybasedsolutionsseemstoprovidethemostsignificantbenefits.

Unfortunately,suchanapproachrequireseitherareconfigurationorasoftwareupdate

inthemobileclient.Thisincreasesitsdeploymentoverhead.Inmanycasesitis

expensiveforthecellularoperatorstoprovidesuchupdatestotheexistingclient

equipment.

Webelievethatafurtherdetailedcharacterizationoftheseenvironmentswillbevery

useful.Ourhopeisthatotherswillalsoperformsimilarstudiesofactualuserexperience

overotherwirelessenvironments(e.g.W-CDMAUMTSandCDMA2000)sothat

extensivebenchmarkscouldbeobtainedandeventuallyleadtoadoptionofa“bestof

bothworlds”solution.

113


68

CDMAinfrastructureiswidespreadandsuretoformthebasisforbroadpenetrationof

CDMAnetworks.Cdma2000andother3Gtechnologiesbringtelecommunicationsinto

thepacketswitcheddomain,addingahostofnewservicesandnetworkcomplexities

intheprocess.Troubleshootingactivitiesnowrequireanunderstandingofboth

traditional“telecom”conceptsrelatedtothecircuit-switcheddomainandnew“datacom”

conceptsrelatedtothepacketswitched-domain.Networkoperationandmaintenance

personnelmustrefinetheirprocessestomeetcomplexnewtroubleshootingchallenges.

TheserangefrommisconfigurationproblemstoduplicatedIPaddressesandmore.

Protocolanalysistoolscanplayabiggerrolethaneverinkeepinganetworkrunning

efficiently.Featuressuchasmulti-interfacecalltracingandprotocolfilteringwillbecome

criticaltothejobofmaintenance.

Wehaveinvestigatedthenetworkperformancebydeterminingthethroughputthatthe

networkcanachieveforagivennetworktopologyandcallarrivalrateprofile.We

formulatedaconstrainedoptimizationproblemthatmaximizesthenetworkthroughput

subjecttoupperboundsontheblockingprobabilitiesandalowerboundonthebit

energytointerference.Totalofferedtrafficandmaximumnumberofcallsallowedtobe

admittedpercellforthetwenty-sevencellCDMAnetworkwithlowmobilityofuser’s

ratio.Theblockingprobabilitiesaregivenbythefixedpointmodel.Weobtained

relationsofthetotalandpartialderivativesoftheblockingprobabilitiesbydifferentiating

114

thefixedpointrelations.Theyareusedinthesolutiontotheoptimizationproblemwhich

yieldsthemaximumnetworkthroughputaswellasthemaximumnumberofcallsthat

shouldbeadmittedineachcellforthenetworktoguaranteeagivengrade-of-service

andquality-of-servicerequirements.Forunequalcallarrivalrates,ouroptimization

algorithmachieveda32%increaseinthroughputoverthetraditionalCACalgorithm.

115


116

70

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75

APPENDIX1:Results

QUALITYVOICECALLS

Quality

No.

F

Dropped

Incomplete

Echo

Jitter

Noise

Factor

Sprint

1900

18

5

29

16

41

0.96

Verizon

1900

125

35

8

31

21

47

0.92

Wireless

MetroPCS

1900

51

10

40

44

67

0.72

Leap

1900

55

12

48

20

81

0.70

USCellular

1900

126

43

8

39

29

62

0.80

MTSMobility

1900

26

9

25

18

52

0.90

AllTel

1900

39

8

32

22

48

0.86

Comscape

1900

57

127

11

41

34

79

0.69

Smartcom

1900

78

34

76

55

103

0.58

PCS

China

1900

71

46

81

51

98

0.60

Unicom

ANALYSISPERFORMEDON1000CALLS.Whenmorethanonenetworkforsame

carrierbeinganalyzed,bestresultsaretakenintoaccountintoabovetable.Worst

128

resultsareformeasurementsagainstlocalnetworkdifferentlyandresultscan’tbe

compared.


76

DATATHROUGHPUT

Throughput

Throughput

10<,<64Kb

>64Kbps

Incomplete

<10Kbps

Droppe

Quality

No.

F

ps

connection

d

Factor

Broad

Middle

Narrow

Sprint

1900

129

46

120

430

450

81

0.78

Verizon

1900

81

167

230

603

97

0.88

Wireless

MetroPCS

1900

92

231

571

198

167

0.62

Leap

1900

130

103

255

560

185

181

0.67

USCellular

1900

108

278

671

51

162

0.75

MTSMobility

1900

79

199

302

499

92

0.82

AllTel

1900

82

131

208

355

437

148

0.76

Comscape

1900

99

251

454

295

179

0.62

Smartcom

1900

267

334

615

51

303

0.43

PCS

China

1900

256

132

246

431

323

298

0.55

Unicom

ANALYSISPERFORMEDIN1000CONNECTIONS.NON-CONNECTIONSDONOT

COUNTTOWARDSPERFORMANCEMEASUREMENTS.Whenmorethanonenetwork

forsamecarrierbeinganalyzed,bestresultsaretakenintoaccountintoabovetable.


77

Worstresultsareformeasurementsagainstlocalnetworkdifferentlyandresultscantbe

compared.

RFMBSTerminal

Handoff

RFStrength

Channel

Terminal

No.

F

MBS

Coverage

Noise

133

Efficienc

GoS

Efficiency

Sensitivity

y

Sprint

1900

0.31

0.76

0.98

-0.70

1.01

0.99

Verizon

1900

0.23

0.77

0.96

-0.75

1.00

0.98

Wireless

MetroPCS

1900

0.27

134

0.72

0.88

-0.92

0.99

0.95

Leap

1900

0.21

0.71

0.87

-0.81

0.96

0.95

USCellular

1900

0.23

0.71

0.86

-0.77

0.98

0.92

MTSMobility

1900

0.30

0.75

135

0.91

-0.78

0.97

0.97

AllTel

1900

0.31

0.70

0.93

-0.92

0.99

0.98

Comscape

1900

0.32

0.77

0.89

-0.97

1.01

0.91

Smartcom

1900

0.33

0.71

0.89

136

-1.07

0.98

0.88

PCS

China

1900

0.36

0.73

0.90

-1.04

0.97

0.87

Unicom

RESULTSFROMDIFFERENTMEASUREMENTSTAKENONTHEFIELD.


78


79

OVERALLNETWORKPERFORMANCE

Network

Evaluation

PerformanceRank

SprintPCS

Excellent

137

1

Verizon

Excellent

2

Wireless

MTSMobility

Excellent

3

AllTel

Good

4

USCellular

Good

5

MetroPCS

Good

6

Leap

Good

7

Comscape

Poor

8

ChinaUnicom

Poor

138

9

SmartcomPCS

Poor

10


80

APPENDIX2:Plots

DroppedCallsComparison

90

d80

san70

uo60

50

erth40

p30

edp20

po10

Dr

0

tin

r

on

S

ap

139

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

140

C

tcom

na

M

ar

hi

Sm

C

Network

IncompleteCallsComparison

d50

45

sanu40

oh35

30

ert25

20

teple15

p10

m

5

co

0

In

tin

141

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

142

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network


81

EchoCallsComparison

90

d80

san70

uo60

50

erth40

p30

edo20

143

h10

Ec

0

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

144

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network

NoisedCallsComparison

120

d

100

sanuo80

h

60

erTp40

145

ised

20

No

0

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

146

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network


82

JitteredCallsComparison

60

d

50

147

sanuo40

hT30

erp20

ed10

tterJi0

S

S

rint

C

lTel

C

Sp

rizon

Leap

elular

obility

Al

scape

P

nicom

Ve

etroP

m

om

M

148

SCU

TSM

Co

M

artc

hinaU

Sm

C

Network

QualityFactorVoiceCallComparison

1.2

1

r

0.8

acto

0.6

alityF0.4

Qu0.2

0

tin

r

on

S

ap

la

149

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

150

tcom

na

M

ar

hi

Sm

C

Network


83

DataThroughputIncompleteConnections

Comparison

er

300

spns250

pt

200

ectionttem

n

A150

o

and

teC

100

151

lep

50

m

Thous

co

0

In

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

152

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network

DataThroughputLessthan10Kbps

400

d350

sanu300

153

oh250

erT200

spn150

100

ectionn50

Co

0

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

154

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network


84


155

85

DataThroughputbetween10and64Kbps

800

d700

sanu600

o

500

erth400

spn300

ectio200

nn100

Co

0

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

156

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

157

C

Network

DataThroughputEquivalenttoBroadband

700

d

600

sanuo500

erth400

sp300

n

200

ectionn100

Co

0

tin

r

on

S

ap

la

y

el

e

S

ilit

158

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

159

Sm

C

Network


86

DataConnectionsDroppedperthousand

350

d300

san250

uo200

erthp150

edp100

po50

Dr

0

tin

r

on

S

ap

la

y

el

e

160

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

161

ar

hi

Sm

C

Network

DataThroughputQualityFactor

1

0.9

0.8

r0.7

acto0.6

0.5

0.4

alityF0.3

Qu0.2

0.1

0

tin

r

on

S

ap

la

y

el

162

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

163

M

ar

hi

Sm

C

Network


87

HandoffMBSSensitivity

0.4

0.35

0.3

0.25

0.2

sitivityn

Se0.15

0.1

0.05

0

ap

y

el

e

Sprint

164

ilit

Verizon

AllT

scap

PCS

Unicom

MetroPCS

Le

USCellular

Com

MTSMob

Smartcom

China

Network


88

RFStrengthCoverageFactor(log)

1

tin

r

on

S

ap

la

165

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

166

tcom

na

M

ar

hi

Sm

C

(log)

ctor

Fa

0.1

Network


89

TerminalEfficiency(Compatibility)

1

0.98

0.96

0.94

0.92

ctor

0.9

Fa0.88

0.86

167

0.84

0.82

0.8

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

168

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network


90

SystemNoise(udB)

10

ise

No

1

169

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

scap

ni

et

170

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network


91

ChannelEfficiency(SpectrumEfficiency)

1.02

1.01

1

r0.99

acto0.98

cyF0.97

ficien0.96

171

Ef0.95

0.94

0.93

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

AllT

PC

com

Ver

ro

172

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network


92

GradeofServiceFactor

1

0.98

0.96

0.94

173

0.92

S

0.9

Go0.88

0.86

0.84

0.82

0.8

tin

r

on

S

ap

la

y

el

e

S

ilit

Spr

iz

PC

Le

luel

ob

174

AllT

PC

com

Ver

ro

scap

ni

et

om

U

M

SCU

TSM

C

tcom

na

M

ar

hi

Sm

C

Network

175


93

MeasurementsatUSCellularNetworkin800MHz


94

176


95


96

177


97


98

178


99


179

Report

100

AreaCoverageProfile(VerizonWireless)

180


101

MariajoséVacaRivas,MBA(MasterinBusinessAdministration)Universitédu

QuébecáMontréal-UQAM-Canadá.MAE(MagisterenAdministraciónde

EmpresasmenciónenNegociosInternacionales)ESPAE-ESPOL.Ingenieraen

ElectricidadespecializaciónElectrónicaESPOL.DocenteeInvestigadora

PosgradoUniversidadTecnológicaEmpresarialdeGuayaquil-UTEG.

ConsultoradeProyectosTecnológicos.

181

TableofContents

Content 2

182

Documents

Network Validation for CDMA 2000 1X EV-DO …...9- Testing and analysis of IMT-2000 networks in the countries visited with hardware and software tools. Network Validation for CDMA