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www.apptrigger.com

White Paper

LTE What Voice Services?

White Paper

November 2009

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1 Introduction MuchhasbeenwrittenlatelyaboutincreasedbandwidthbenetsofLTEand

CommunicationServiceProviders(CSPs)planstodeploythetechnologyas

the4Gfoundation.ManyCSPshaveannouncedtheirLTEplansandsome

haveevenbegunlimitedLTEdatatrials.Forsuretheresacomingwaveof

networkupgradesandnewhandsetsthatwillcertainlytransformmobile

broadband.

CSPsconsideringthetransitiontoLTEdataarefacedwiththedecisionofwhetherto

alsoofferLTEvoiceservicesinordertobetterutilizethenewnetworkinfrastructure,

ordeployLTEdata-onlynetworks.Forthemostpart,itseemsthatthedesireis

theretotransitiontoLTEvoicesoonerratherthanlater.Thisstrategymakessense

asLTErequiresentirelynewradioaccesstechnology,fromantennastobasestation

controllerupgrades,andkeepingtworadioaccessnetworksgreatlyincreasesOPEX

whichmightbebestspreadacrossawidersegmentofofferings.

ItisthehowtodeliverLTEvoiceservicesthathascreatedconfusion.WhenLTEwas

originallyenvisioned,theconventionalthinkingwasthattheCSPsnetworkswould

havetransitionedtoIMSarchitecturesbythenandthereforevoiceonLTEwouldnaturallybebasedonVoIP.Therealityisthatasofthiswriting,thereareveryfewtrue

IMSproductionnetworksinplaceandthereforeCSPsmustreconcilehowtoquickly

deployLTEwiththerealitiesofnetworktransformationtimelinesandbudgets.

2 Options, options

Ofcoursethereareoptionsonhowtomoveforwardwithvoicedeliveryarchitectures.

Thebackdropofwhichisthegeneralagreementthatcurrent2Gand3Gnetworkswill

beinplaceforsometimetocome,andthereforeCSPsmusttakeintoaccountnotonlyhowtheirnetworkwillevolve,buthowtosupportroamingandhandoversacross

multipleCSPs.Inaddition,theexpectationisthatcurrent2G/3Gsubscriberswillbe

thersttomigrateto4GasCSPsprovideupgradeincentives,whichputsadditional

burdenofprovidingfeatureandserviceparityasparttheupgradeassubscriberswill

expecttheircurrentcallfeaturesetstobehavethesameoncetheyupgrade.

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Amongthemoststudiedoptionsforvoicedeliveryare:

DualModeHandsets.Having handsets that support both GSM and UMTS means that

subscribers are able to roam in-out of the national/international networks and ensure

service continuity when LTE networks are not yet fully built up.

3GPPIMS.The CSP may take this opportunity to upgrade the core network to IMS

architecture. Deployment of IMS-based LTE voice has been documented since IMS

Release 8. Moving to IMS has the obvious advantage of commoditizing a large portion of

the network, bringing with it all the benets discussed for several years now.

VoiceoverLTEGenericAccess.Another option that has been put forth is Voice over LTE

Generic Access (VoLGA), supported by a newly-formed industry consortium known as

the VoLGA Forum. VoLGA proposes utilizing the IMS-based LTE radio access network,

but maintains the circuit-switched network (either GSM or CDMA based) by introducing a

network element known as the VANC (VoLGA Access Network Controller). The VANC is

responsible for connecting the packet-switched LTE access network to the current circuit-

switched core network, ensuring that existing MSC are not changed. Of course this

ensures that theres minimal disruption to existing switching elements and current voice

applications may be delivered.

CircuitSwitchedFallback.Here the handset normally operates in 4G (LTE) mode when

accessing data services and idle, but switches to a 2G or 3G radio when it is informed of

an incoming call, or an outgoing call is placed. A mechanism to inform the handset via 4G

(IP data path) that a call is inbound does need to be formalized.

ProprietarySolutions.Other options do exist, such as upgradable IP-enabled MSCs, but

those tend to be tied to a specic vendor architecture.

Tobeclear,thesearchitectureoptionsaddresshowtomarrythepacket-switched

LTEradionetworkwiththeserviceoperatorcorenetworkforthepurposeof

deliveringvoice.WhatisnotimmediatelyapparentishowdoestheCSPdeliver

voiceapplications,suchasFindMe/FollowMe,VoiceVPN,CRBTandallthecritical

revenuegeneratingadd-onsthatsubscribersuseandwouldexpecttomigratetoLTE.

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3 Service Brokering

Regardlessofthearchitecturechosen,CSPswillbefacedwithapplicationdelivery

challengescreatedbythetransitioninLTEtopacketbasedvoice.Todaysvoice

servicesarepredominantlydeliveredviaServiceControlPoints(SCP)orIntelligent

Network(IN)ApplicationServersconnectedviaINprotocolssuchasINAPandCAMEL.

Thoseservicestendtobehighlystableandprotablebutalsohighlycustomized,

andthereforenoteasilymovedtoSIP-basedapplicationservers.CSPswillneedto

deliverthesesameservices(downtofeaturesetsandevenquirkybehavior)onLTE

subscriberstoensuremigratedusershavethesamelevelofserviceandexperience.

AsCSPsevolvetheirnetworksforLTEandothernetworks,theresultingnetworks

presenttremendouschallengesinvoiceservicesandapplicationdelivery.Realizing

this,theindustryhascomeforwardwithapurpose-builtnetworkelement:theService

Broker,asolutionspecicallydesignedtoovercomenetworkarchitecturechallenges

andensurevoiceservicedeliveryfromanynetworkdomaintoanyothernetwork

domain.

ServiceBrokersareplacedbetweentheapplicationlayerandthecontrollayer,and

assumeanddeliveranumberofrolesasneeded:theIMSIM-SSF,SCIM,reverse

IM-SSF,MediaResourceBroker(MRB),INtriggermanagementandsubscriberdata

management.Alltheseroleshavethecommonpurposeofdeliveringandextending

thereachofapplicationstoallnetworkdomainsoftheCSP.

LetstakealookathowServiceBrokermighttwithintwoofthemostpopular

networkproposals,IMSandVoLGA.

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4 LTE Voice over IMS

ServiceBrokersprovidethecapabilityofextendingcurrentvoiceservicesbyproviding

seamlesscall/sessioninterworkingbetweenthepacketswitchedLTEaccessnetwork,

andcircuit-switched3Gapplicationswithoutrequiringchangestoeither.Forthose

CSPsthathavexedlinenetworksaswell,theyarealsoabletoreutilizevoiceservices

whichmayhavebeenonlyofferedinthatnetworkdomaintonewwirelessLTE

subscribers.

Inthegureabove,LTEclientsareabletoaccessallapplicationstheypreviouslyused,

suchasPrePaid,CRBT,VoiceVPN,FindMe/FollowMe,etc,andthereforearenot

requiredtochangetheirsubscribedservices.Fromanetworkperspective,theService

BrokerenablestheIMSnetworktoseetheexistingapplicationsasnewSIP-based

applications,byprovidingtheinterworkingrequired.AsfarastheIMSnetworkis

concerned,theServiceBrokeristheSIPserver,whiletotheexistingSCPstheService

Brokerisanexisting3GMSC.

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5 LTE Voice over VoLGA

ThoseCSPsthatchoosetofollowanarchitecturebasedontheVoLGAforum

proposals,theServiceBrokerprovidestheinversebenet:allowingnext-genSIP-

basedapplicationstobeutilizedbytheexisting3Gnetwork.Italsobecomespossible

tobringforwardthoseapplicationsresidingonthexedlinenetworkaswell,further

enhancingtheservicedeliveryoptions.

6 Service Broker Functions

ServiceBrokersprovideotherfunctionalitythat,oncedeployed,canbeofadded

benettotheCSP.Amongthemostoftendeliveredfeaturesare:

IMSSCIM(nowrenamedtheIMSServiceBroker)

IN-INTriggerManagement

Real-TimeCharging

Protocol/CallFlowManagement

SubscriberDataManagementInteraction

MediaResourceBrokering

ServiceOrchestration

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TheServiceBrokersabilityofperformingorchestrationandcombinationofdiscrete

voiceapplicationsandservicesintonewcombinedofferings(voicemash-ups)

isparticularlyexciting.WiththiscapabilityCSPsareabletocreatenewrevenue

producingofferstosubscriberswheretheypreviouslywerenotavailable:CRBTand

PrePaid,FindMe/FollowMecombinedwithVoiceVPNs,etc.

ServiceBrokersalsoprovidethecapabilityofgeneratingRealTimeChargingevents,

eitherprogrammatically(viaanAPI)orautomaticallyaspartofservicedelivery.The

challengefacingCPSsisdeliveringnew,innovativeservicesthatseamlesslyintegrate

intoexistingbillingplatforms.Doingsooftenmeansnormalizingchargingevents

oreventransformingchargingeventsfromonetechnologytoanother,asisthecase

inINtoIMSmigration.BecausetheServiceBrokerisresponsiblefororchestrating

anddeliveringcombinationalservices,itisoftenthentheresponsibilityoftheService

Brokertogenerateachargingeventuponsuccessfulstart/completionofthose

enhancedservices.

7 Ignite Service Broker

AppTriggerintroduceditsServiceBrokersolution,theIgniteServiceBroker,to

meettheseneedsofprovidingefcientandcost-effectiveapplicationconnectivity

fortier1serviceprovidersworldwide.AppTriggersIgniteServiceBrokerresidesat

theapplicationlayerandsitsbetweentheapplicationlayerandthecorenetworkto

provideinterworkingandmanageconnectivitytotheevolvingnetwork.TheIgnite

ServiceBrokerisabletoconnectanyapplicationtoanyuserbyincorporatinga

numberofopenstandardAPIsandispurposebuilttodeliversignaling,mediaand

featureinterworkingbetweendisparatenetworksthatconvergedandconsolidated

applicationsrequire.

TheIgniteServiceBrokersolutionleveragesthesecapabilitiestoallowCSPsto

preservetheirinvestmentincurrentrevenue-producingvoiceapplicationsbyenabling

interworkingwithnext-generationnetworkbuild-outs.ThisenablesCSPstheability

tore-purposetodaysprotablelegacyvoiceapplicationswiththeirnewNGnetworkssuchasLTE,aswellastomaximizeinvestmentandreduceriskinthedeploymentof

newserviceswithlegacyIN/TDMnetworks.

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8 Conclusion

CSPsarecurrentlyspendingalotoftimeandenergyqualifyingLTEradioaccess

networktechnology,whichwillensurelivedeploymentsmaintainorexceedcurrent

mobilereliability.ThenextseveralquarterswillproveinterestingasCSPschoose

LTEvoicedeliveryarchitectures,muchofitinuencedbytimeandtheirownnetwork

designsrequirements.Carefulconsiderationofvoiceservicesandapplications

willensurehigh-valuecustomers(earlyLTEadopters)areabletoenjoythesame

voicefeaturesandservicestheyarecurrentlyusedto,ensuringtheyarepermanent

converts.ServiceBrokerswillplayacriticalroleinensuringCSPsareableto

immediatemigratecurrentvoicerevenueplatformsforthoseearlyLTEsubscribers.

Allstatements,specications,recommendations,andtechnicalandotherinformationcontainedinthisdocumentarecurrentasofthedateofpublicationandpresentedwithoutwarrantyofanykind,whether

expressedorimplied.AppTriggerreservestherighttorevisetheinformationinthedocumentatits

discretionwithoutnotice.AppTriggershallnotbeliableforerrorsoromissionsinthisdocument.AppTrigger

shallnotbeheldliablefordamagesofanykindresultingfromthefurnishingoruseofthisdocument.

AppTriggerproductspecicationsaresubjecttochangeatanytimewithoutadvancednotice.Allproductsor

servicesmentionedarethetrademark,servicemarks,registeredtrademarksorregisteredservicemarksof

theirrespectiveowners.2009AppTrigger,Inc.Allrightsreserved.

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2009Allrightsreserved.