Enabling UMTS 900 Mobile Broadband Services with Ditech Networks

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Enabling UMTS 900 Mobile Broadband Services with Ditech Networks

October 2007

Contents

Copyright © 2007 Ditech Networks2/14

Introduction...............................................................................................................................3

BackgroundonUMTS900............................................................................................................3

UMTS900EnablesAffordableMobileBroadbandServices...............................................................3

RecentUMTS900Developments..................................................................................................4

UMTS900HandsetAvailability.....................................................................................................4

TheChallengeswithUMTS900....................................................................................................4

SpectrumIssues..........................................................................................................................4

PossibleApproachesforClearing900MHzSpectrum.....................................................................4

2GUpgradeMethods–ProsandCons..........................................................................................5

3GAcceleratedMigration–ProsandCons....................................................................................6

TheDitechSolutionforUMTS900................................................................................................7

VQA™Overview.........................................................................................................................7

ResultsfromVQADeploymentinGSMNetwork.............................................................................8

CostComparison........................................................................................................................8

Conclusions...............................................................................................................................9

References................................................................................................................................10

Enabling UMTS 900 Mobile Broadband Services with Ditech


Copyright © 2007 Ditech Networks �/14

Introduction

ThispaperprovidesabackgroundtothebenefitsofdeployingUMTS-basedmobilebroadbandservicesintheGSM900MHz

bandandthecurrentUMTS900developmentsindifferentcountries.

Variousmethodsavailableforclearingspectrumintheoftencrowded900MHzbandandtheassociatedcostsarediscussed,as

wellashowtominimizedisruptiontoexistingGSMservices.Acomparisonthatquantifiesthecostsofthedifferentmethods

foratypicalWestEuropeancarrierisprovidedasasummary.

ThepaperalsointroducesDitech’snewVQA™solutionforUMTS900thatfreesupspectruminthe900MHzbandbyen-

ablingincreaseduseofGSM-HRandAMR-HRcodecswhilemaintainingacceptablevoicequality,withouttheneedforexpen-

sivenewBTSsiteconstructionorupgrades.Inaddition,theDitechsolutionemployscapabilitiesthatarealreadysupportedby

existinghandsets,thusitdoesnotrequireanycostlyhandsetsubsidies.

Background on UMTS 900

UMTS 900 Enables Affordable Mobile Broadband Services

UMTScarriersarecurrentlyrollingoutmobilebroadbanddataservicesbasedontheHighSpeedDownlinkPacketAccess(HS-

DPA)technologywhichcannowdeliverpeakdataratesofupto7.2Mbps.

ThecoverageoftheseservicesisunfortunatelylimitedinthestandardUMTS2100MHzband.Thisresultsinasignificant

reductionofthepracticaldataratesthatcanbedelivered,especiallyinsidelargebuildingsaswellasinruralareas.Onecost-

effectivewaytoaddressthisissueistodeploythemobilebroadbandservicesintheGSM900MHzbandinstead,wherethe

propagationcharacteristicsaremuchmorefavorablecomparedtotheregular2100MHzband.Thissolutionisreferredtoas

UMTS900.

Studiesshowthatthenumberofbasestationsitescanbereducedby60%[1],whichmayresultincostsavingsontheorder

of$2billioninlargenetworks,accordingtoanextensivestudypublishedrecentlybytheUKregulatorOfcomonUMTS900

andtheeffectsofreleasing900MHzspectrum[2].

Figure1::UMTScoverageat900MHzand2100MHz,respectively[3].


Copyright © 2007 Ditech Networks 4/14

Recent UMTS 900 Developments

Theuseofthe900MHzbandinEuropehasuntilnowbeenreservedexclusivelyforGSM.However,theEuropean

Commissionisnowproposingamoreflexibleapproachtothesefrequencies,whichwouldpermittheirusefor3G/

UMTSaswell.UMTS900equipmenthasrecentlybeentrialedinFinland,France,Portugal,andtheUKwithgood

results.NationalregulatorsinEuropearegenerallyexpectedtoconsiderandauthorizeUMTSHighSpeedPacketAc-

cess(HSPA)deploymentsinthe900MHzband.UMTS900hasalsobeenrecentlytrialedinAustralia.InNewZeeland,

VodafoneisplanningtogolivewithaUMTS900servicein2008[1].

Furthermore,theGSMAssociationhascalledonadministrationstoopenupthe900MHzbandto3Gworldwide[4].

UMTS 900 Handset Availability

ThefirstUMTS900handset,theNokia6121smart-phonewasrecentlyannouncedwithshipmentsstartinginQ32007

[1].AllleadingchipsetandhandsetvendorsareplanningforUMTS900,butinitialvolumesaredifficulttopredictand

maybelow,possiblylessthanafewmillionhandsetsproducedby2009,accordingtoanOvumreport[5].Also,UMTS

handsetsfortheadjacent850and1900MHzbandsarealreadycommerciallyavailableintheUS.

The Challenges with UMTS 900

Spectrum Issues

ItisclearthattherearealotofadvantageswithdeployingUMTSbroadbanddataservicesinthe900MHzband.

However,the900MHzspectrumisscarceandnationalregulatorshavealreadyallocatedmostofittoexistingGSM900

services.

Oneblockof2x5MHzisrequiredtoaccommodateasingleUMTSfrequencycarrier.TheUMTSForumsuggeststhe

followingso-called“sandwich”frequencyarrangementtominimizepossibleinterferencebetweenUMTS900witha5

MHzfrequencycarrierandexistingGSM900servicesusing200kHzcarriers[6]:

GSM UMTS GSM Figure2::SuggesteddeploymentofUMTSinthe900MHzband

Thismeansthatcarrierswillhavetofreeupaconsiderableamountoftheir900MHzspectrumthatisalreadyinuse

whileatthesametimeensuringthatthisdoesnotimpacttheirexistingGSMvoiceservices.

Possible Approaches for Clearing 900 MHz Spectrum

Therearebasicallytwopossibleapproachestofreeupspectruminthe900MHzbandaccordingtotheUKregulator

Ofcom[2]:

The“2GUpgrade”implements2GtechnologiesthatusetheremainingGSMspectrummoreefficientlytosupportthe

existingGSMusers,whilethe“3GAcceleratedMigration”movestheGSM900trafficontoanexistingUMTS2100

networkbyincreasing3Ghandsetsubsidies(assumingthecarrieroperatessuchanetwork):



Figure3::Strategiesforimplementing900MHzspectrumrelease[2]

Avariantofthe2GUpgradeisthemethodproposedbytheUMTSForumwheretheGSM900trafficishandedovertoa

GSM1800network(assumingthecarrieralreadyhasaGSM1800networkinoperation):

.

Figure4::LoadbalancingbetweenGSM900andGSM1800inordertore-farmpartofGSM900spectrumforUMTS900

deployment[6].

2G Upgrade Methods – Pros and Cons

2GUpgrademethodsincreasethecapacityoftheremainingGSMspectrumandincludesSynthesizedFrequencyHopping

(SFH),increaseduseoflowbit-rateGSM-HRandAMR-HRcodecs,andCellSplittingofmacrosites.

Synthesized Frequency Hopping

SFHisacost-effectiveandwell-provenmethodforincreasingGSMcapacityandspectrumefficiency.Though,itwillobvi-

ouslyonlyworkinnetworksthathavenotyetdeployedthisfrequencyhoppingmethod.

SFHrequiresnewertypesofbasestationsthatsupportthisfeature.Olderbasestationswillrequirecostlyhardware

upgrades(replacementofcavitycombinerswithhybridcombiners)aswellassoftwareupgradesthattogetheramountto

acostofabout$26,000persite,orabout$20-50millionforatypicalnetworkintheUK[2].Theactualcostmayvary

significantlydependingonexistingGSMtrafficloadsandnumberofbasestationsthatrequireupgrades.Also,SFHmust

beimplementedinwholeclustersofcellstogettherequiredcapacitygains.



GSM-HR and AMR-HR

Theusehalf-ratecodecssuchasGSMHalfRate(HR)andthenewerAdaptiveMultiRate(AMR-HR)versionallows

acarriertoincreasecapacityduringbusyhourandimprovetheutilizationofitsexistingGSMinfrastructurewith-

outtheneedfornewBTSsitesandcostlyhardwareupgrades.Half-ratecodecscanalsobeemployedlocallyona

call-by-callbasisdependingoncapacitydemands.

Whilehalf-ratecodecsaredeployedinmanynetworksandarefullysupportedbytheexistinginstalledbaseof

GSMhandsets,carrierstendtousethemverycautiouslyduetovoicequalityconcerns.Althoughthesecodecs

performquitewellinidealcleanspeechconditions,theyareoptimizedforthehumanvoice,andasaresult,

degradesignificantlyinthepresenceofbackgroundnoisecommoninbusystreets,crowdedplaces,andinside

vehiclessuchascars,buses,andtrains.Inaddition,non-linearacousticechoisoftencreatedbylow-endhand-

setsandhands-freekitssuchasBluetoothheadsets.Thistendstofurtherdegradetheuserexperienceofcalls

usinglowbit-ratecodecs.

Aswillbeexplainedlateron,GSM-HRandAMR-HRcanbecombinedwithadvancednetwork-basedvoicequality

enhancementsolutionsthatincludeAdaptiveNoiseCancellation(ANC),AcousticEchoCancellation(AEC),and

EnhancedVoiceIntelligibility(EVI)tomitigatethedegradationinvoicequalitycausedbytheuseofhalf-rateco-

decs.Thus,advancedvoiceprocessingsolutionscanenableGSMcarrierstomaintainanacceptablevoicequality

alsoduringconditionswithincreaseduseofHRandAMR-HRcodecs.

Cell Splitting of Macro Sites

CellsplittingofmacrositesisthetraditionalwaytoincreasecapacityinaGSMnetwork,andthereareno

particulartechnicalproblemsassociatedwiththismethod.Thedownsideisthatcellsplittingisaveryexpensive

andtime-consumingalternative,asitcantake6-12months,orevenlonger,toacquireanewsiteandobtainthe

necessarypermissions.Theconstructioncostistypicallyaround$200,000persitewithatypical20yearNetPres-

entValue(NPV)ofabout$500,000intheUK(thisisthetotalcostofbuildingandoperatingthesiteincluding

siterentsover20years)[2].

Micro-Cells and In-Building Solutions

TheOfcomstudyconsidersotherpotentialcapacitysolutionssuchasdeploymentofmicrocellsanddedicatedin-

buildingsystems,buttheUKregulatorconcludesthatthesesolutionshavepracticallimitationsthatmakethem

lesssuitableforaddressinglarge-scalecapacitydemands.

3G Accelerated Migration - Pros and Cons

The3GAcceleratedMigrationoptionassumesthatacarriercanmovethedisplacedGSM900trafficprimarilyto

itsUMTS2100network.Thisispossibleifthefollowingtwoconditionshold,theremustbeadequate3Gcover-

ageinareaswheretheGSMcapacityisconstrained,andtheremustbesufficient3Gcompatiblehandsetsinthe

subscriberbase.

However,UMTS2100isunlikelytoprovidethesamequalityofserviceinsidebuildingsthatGSM900coulddue

tothedifferentpropagationcharacteristicsofthetwobands.Thecostofacceleratingthemigrationto3Gusing

handsetsubsidieswilldependonthepercentageofusersthatalreadyhave3Genabledphonesaswellasthe

costof3Gphonesover2Gones.Ofcomassumesapremiumofabout$200for3Gphonescomparedto2G

ones,andestimatesthetotalcostofanaccelerated3Ghandsetmigrationto$200millionormoreinatypical

UKnetwork[2].Thus,the3GAcceleratedMigrationmethodcouldbearathercostlyalternative,especiallyifad-

ditionalsiteswillhavetobebuilttocompensateforpoorercoverageat2100MHz.



The Ditech Solution for UMTS 900

Ditech’ssolutionforUMTS900employsthecompany’saward-winningVoiceQualityAssurance(VQA™)to

increasetheuseofGSM-HRandAMR-HRforimprovedcapacitywhilemaintainingacceptablevoicequality,thus

enablingthedeploymentofUMTSintheGSM900MHzband

VQA™ Overview

VQAisacomprehensivesetofindustry-leadingvoiceprocessingalgorithmsincludingbi-directionalAdaptive

NoiseCancellation(ANC),AcousticEchoCancellation(AEC),andEnhancedVoiceIntelligibility(EVI)thattogether

mitigatetheproblemsofusinglowbit-ratecodecsinnoisyenvironmentscommoninmobilecalling.

Ditech’ssolutionistypicallydeployedonthestandardA-interfaceattheMobileSwitchingCenter(MSC)andis

abletoprocessandenhanceallcalltypesincludingmobile-to-mobileandmobile-to-PSTNcalls:

Figure5::Ditech’sSolutionatA-Interface

Thesolutionconsistsoftwosoftwarepackagesthataredeliveredononeofthreehardwareplatforms,wherethe

choiceofhardwareisbasedonnetworkinterfacerequirements:

• VoiceQualityAssurance(VQA™)–improvesthespeechqualitybyemployingbackgroundnoisecancellation,

speechenhancementforlowbitrateGSMcodecs,backgroundnoisecompensation,acousticechocontrol,voice

leveladjustment,andoptionalhybridechocancellation

• ExperienceIntelligence™(EXi)

o Quantifiesandcategorizesexternalimpairmentssuchasnoiseandechothatarepresentonlivecalls

o GeneratesacallqualityscorebasedupontheITU-TG.107E-modelstandard[7].

• Hardwareplatforms–dependentonnetworkconfiguration

o E1basedA-interface:QuadVoiceProcessor(QVP)

o STM1basedA-interface:BroadbandVoiceProcessor(BVP)

AcarriercangenerallydeploytheDitechsolutionintheentirenetworkinonly2-4monthswithaminimalimpact

onservices.TheVQAsolutionforUMTS900canpotentiallybedeployedonaBSC-by-BSCbasisinthoseareas

whereincreasedGSMcapacityisrequired.



Results from VQA Deployment in GSM Network

DitechrecentlyperformedanextensivenetworkauditonmillionsoflivecallsinalargeGSMnetworkinWestern

Europe.Figure6belowshowsthemeasuredcumulativequalitydistributionofcalls,wherealmost50%ofthe

half-ratecallsfallbelowaMOSof2.7(or54pointsontheRscale),accordingtotheITU-TG.107E-model.It

turnedoutthat30%ofthelivecallshadsignificantamountofbackgroundnoiseandabout10%hadobjection-

ableacousticechoasdefinedbytheITU-TG.131recommendation[8].Thus,theseimpairmentshadasignificant

impactoncustomerexperience:

Figure6::ImpactofVQAondeliveredHRandAMR-HRcallqualityat1%FERwith70%HRand30%AMR-capablehandsets

Ascanbeseenintheabovechart,VQAwasabletoremovealargeamountofthebackgroundnoiseandecho,

andasaresult,thenumberofunacceptablecallswasreducedtoonly10%.Thus,VQAwashighlyeffectivein

removingexternalimpairmentsthatwouldotherwisedegradealargepercentageoftheGSM-HRandAMR-HR

callstoanunacceptablequalitylevel.

Cost Comparison

Thissectioncomparesthedifferentmethodsandassociatedcostsforclearing900MHzspectrumdiscussedin

previoussections,assumingatypicalcarrierintheUK.

Thesecostsmayvarysignificantlyfromcarriertocarrierdependingontheamountof900MHzspectrumthat

needstobecleared,thecurrentandprojectedtrafficloadsinthe900,1800,and2100MHzbands,thenumber

ofGSM900,GSM1800,andUMTS2100basestationsites,thehardwareandsoftwarecapabilitiesofexisting

GSMbasestations,aswellascurrentandprojected3Ghandsetpenetrationnumbers.

Thefollowingtablesummarizesthecostsassociatedwiththedifferentalternatives.Thesecostsareonlyapproxi-

matebuttheyshouldatleastreflecttheorderofmagnitudeoftheexpensesrequiredforclearingnecessary900

MHzspectrumtodeployUMTS900inamaturenetworkinWesternEurope(costsforSFH,CellSplittingand

Accelerated3GHandsetMigrationbasedoninformationprovidedin[2]):



Method EstimatedTotal Cost

Estimated Costper Subscriber Assumptions and Comments

SFH ≥ $25 million ≥ $1.50 About 30% of base stationsneed hardware upgrades thatcost about $26,000 per site.Total cost including frequencyplanning and optimization isestimated to at least $25 millionfor an average capacitydemand scenario.

Method only works if SFH is notyet deployed.

Cell Splitting ≥ $200 million ≥ $10 At least 1,000 additional sitesrequired. Construction cost persite is $200,000 (total costsover 20 years estimated to$500,000 per site).

Accelerated 3G HandsetMigration

≥ $200 million > $10 Accelerate migration to UMTSby subsidizing1 million 3Ghandsets at a $200 premiumcompared to 2G phones.

Increased HR/AMR-HR usecombined with voice qualityenhancement solution suchas Ditech’s VQATM solution

< $15 million < $1.00 Increased use of HR/AMR-HRcombined with network-basedvoice quality enhancementsolution deployed in areaswhere increased GSM voicecapacity is required.

Table1::Approximatecostsforclearingspectruminthe900MHzbandforamatureWesternEuropeanGSMnetwork

Conclusions

TheabilitytodeployUMTSinthe900MHzbandprovidesmobilecarrierswithanopportunitytooffermoreaffordablebroad-

banddataserviceswithhigherdataratesandbettercoveragecomparedtodeploymentintheregular2100MHzband.

Re-farmingthe900MHzspectrumwithoutdisruptingcurrentGSMservicescanhoweverbeamajorchallenge.UMTS900

requiresatleastoneblockof2x5MHzspectrumin900MHzband.Thisisasignificantamountofspectrumthatneedsto

beclearedfromabandthatisalreadyheavilyusedbyGSM.

Therearebasicallytwoapproachestomitigatethisproblem.The“2GUpgrade”implements2Gtechnologiesthatusethe

remainingGSMspectrummoreefficiently.ThesetechnologiesincludeSynthesizedFrequencyHopping(SFH),HR/AMR-HRco-

decs,andCellSplitting,whilethe“3GAcceleratedMigration”movesGSM900voicetrafficontoanexisting3GUMTS2100

networkbyincreasing3Ghandsetsubsidies.



Eachoftheabovesolutionshasitsownsetofadvantagesanddisadvantagesandthemostsuitablesolutionmay

varyfromcarriertocarrierbasedoneachspecificsituation.

IncreasedusageofHRandAMR-HRcodecsisgenerallyaverycost-effectivemethod,provideditiscombinedwitha

voicequalityenhancementsolutiontomaintainacceptablequality.Thismethodimprovesutilizationoftheexisting

GSMinfrastructurewithouttheneedforexpensivenewBTSsiteconstructionorupgrades.Nordoesitrequireany

costlyhandsetsubsidiesasGSM-HRandAMR-HRcodecsarealreadysupportedbytheinstalledbaseofGSMhand-

sets.Also,carrierscaneasilydeploythesolutionlocallytodealwithcongestionine.g.busyurbanareas.

Ditech’sVQA™solutionforUMTS900enablesincreaseduseofHRandAMR-HRcodecsbyremovingexternal

impairmentssuchasbackgroundnoiseandacousticechothatotherwisetendtodegradethequalityoftheselow

bit-ratecodecstounacceptablelevels.Ditech’svoicequalityenhancementsolutioncanbequicklydeployedinan

entirenetworkwithin2-4monthswithoutcostlyupgradestoBTSsitesandwithminimaldisruptiontoexistingGSM

andUMTSservices.Finally,carriershavetheoptiontodeployVQAonlyinselectareasonaBSC-by-BSCbasisto

meetlocalcapacitydemands.

References

[1]GlobalmobileSuppliersAssociation(GSA),InformationPaper,September2007.

[2]ApplicationofSpectrumLiberalisationandTradingtotheMobileSector,OfficeofCommunications(Ofcom),UK,

September2007.

[3]HuaweicontributiontoUMTSForumWorkshop,June20,2007.

[4]GSMAssociationPressRelease,June25,2007.

[5]MarketStudyforUMTS900,Ovum,February,2007.

[6]DeploymentofUMTSin900MHzBand,UMTSForumWhitePaper,October2006.

[7]ITU-TRecommendationG.107(03/2005)TheE-model,acomputationalmodelforuseintransmissionplanning.

[8]ITU-TRecommendationG.131(11/2003)TalkerEchoandItsControl


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Copyright © 2007 Ditech Networks. All rights reserved. Experience Intelligence, Packet Voice Processor, and VQA are trademarks of Ditech Networks. All other brands are the property of their respective owners. Specifications may change without notice. This document was last revised 10/07.

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Enabling UMTS 900 Mobile Broadband Services with Ditech Networks