Ericsson Technology Review: Flexibility in 5G transport networks: the key to meeting the demand for connectivity
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1) 5G networks will need to be highly flexible to meet the increasing demands for connectivity as applications evolve and the number of connected devices grows exponentially. This will require tight integration between 5G radio, transport networks, and cloud infrastructures. 2) Transport networks will need to be flexible in order to provide connectivity between sites and individual terminals, as well as meet stringent requirements for capacity, synchronization, timing, delay, and jitter. They will also need to support network slicing to allow for customized network slices tailored to specific service and application needs. 3) Achieving the necessary flexibility will require new levels of programmability and abstraction across transport networks through software-defined networking and network functions virtualization principles. This will
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Ericsson Technology Review: Flexibility in 5G transport networks: the key to meeting the demand for connectivity
- 1. A FLEXIBLE TRANSPORT NETWORK â± OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 1 C H A R T I N G T H E F U T U R E O F I N N O V A T I O N V O L U M E 9 2 | # 8 â 2 0 1 5 FLEXIBILITYIN5G TRANSPORTNETWORKS: THEKEYTOMEETINGTHE DEMANDFORCONNECTIVITY ERICSSON TECHNOLOGY Fronthaul Backhaul Packet Packet Wireline access CWDM/DWDM dedicated fiber Access Aggreg Data cent BB IP IP IP
- 2. â± A FLEXIBLE TRANSPORT NETWORK 2 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 PETER ĂHLĂN BJĂRN SKUBIC AHMAD ROSTAMI KIM LARAQUI FABIO CAVALIERE BALĂZS VARGA NEIVA FONSECA LINDQVIST The more people have been able to achieve while on the move, the more dependent society has become on mobile broadband networks. As applications like self-driving vehicles and remotely operated machinery evolve, become more innovative, and more widespread, the level of performance that 5G networks need to deliver will inevitably rise. Keeping pace with ever- increasing demand calls for greater flexibility in all parts of the network, which in turn requires tight integration between 5G radio, transport networks, and cloud infrastructures. A d va n c e s i n t e c h n o l o g y and a shift in human behavior are influencing how 5G networks are shaping up. With 3G, things got faster, data volumes surpassed voice, new services were developed, and people started using mobile broadband. With 4G, mobile broadband soared. Todayâs networks provide advanced support for data. Building on this success, 5G aims to provide unlimited access to information and the ability to share data anywhere, anytime by anyone and anything. So, as we move deeper into the Networked Society, the connections that link things and people will become almost exclusively wireless. Serviceslikemobilebroadbandandmedia distributionwillcontinuetoevolveinlinewith ourgrowingglobaldependenceonconnectivity. Networkswillexperiencehugeincreasesintraffic andwillneedtoserviceanever-expandingnumber FLEXIBILITY IN 5G transport networksTHE KEY TO MEETING THE DEMAND FOR CONNECTIVITY
- 3. A FLEXIBLE TRANSPORT NETWORK â± OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 3 ofconnecteddevicesâbothmassivemtc (iot) andmission-criticalmtc.Thelattersetsstringent requirementsforperformancecharacteristicslike reliabilityandlatency. Thedigitalandmobiletransformationscurrently sweepingthroughindustriesworldwidearegiving risetoinnovativecross-sectorapplicationsthat aredemandingintermsofnetworkresources.And so,5Gnetworkswillnotonlyneedtomeetawide rangeofrequirementsderivedfromuserdemand anddevicedevelopment;theywillalsoneedto supportadvancedservicesâincludingthoseyetto bedeveloped. Limitlessinnovationinapplicationdevelopment, deviceevolution,andnetworktechnologyare shiftingfromamodelthatisoperatorsteeredto onethatisuserdriven.Flexibilityandoperational scalabilityarekeyenablersforrapidinnovation, shorttimetomarketfordeploymentofservices,and speedyadaptationtothechangingrequirementsof modernindustry. Howwillfuturenetworksevolve? Toensurethatnetworkswillbeabletocopewith thevariedlandscapeoffutureservices,avarietyof forumslikengmn,itu-r,and5g ppp areworking onthedefinitionofperformancetargetsfor5G systems [1]. Incomparisonwith2015levels,theperformance projectionsthatwillhavemostimpactontransport networksare: ăă 1000xmobiledatavolumepergeographicalarea, reachingtargetlevelsoftheorderofTbpspersqkm ăă 1000xthenumberofconnecteddevices,reachinga densityofoveramillionterminalspersqkm ăă 5ximprovementinend-to-endlatency,reachingtoas lowas5msâasisrequiredbythetactileinternet. However,themaximumlevelsofperformancewill notallapplyatthesametimeforeveryapplication orservice.Instead,5Gsystemswillbebuilttomeet arangeofperformancetargets,sothatdifferent serviceswithwidelyvaryingdemandscanbe deployedonasingleinfrastructure. Gettingnetworkstoprovidesuchdifferenttypes ofconnectivity,however,requiresflexibilityin systemarchitecture. Asidefrommeetingthestringentrequirements forcapacity,synchronization,timing,delay,and jitter,transportnetworkswillalsoneedtomeet highlyflexibleflowandconnectivitydemands betweensitesâandinsomecasesevenforindividual userterminals [2]. Emerging5Gradiocapabilitiesandthe convergenceofradioaccessandwireless backhaulhavetriggeredanuptakeoffixed wirelesstechnologiesasacomplementtofixed broadband [3].Withhybridaccess5Gnetworkswill beabletoprovidetheincreasedcapacityneededto handlepeaktrafficforresidentialusers.Assuch,5G radiowillincreasinglycomplementandoverlapwith traditionalfixed-broadbandaccesses. Termsandabbreviations 5g pppâ5G Infrastructure Public Private Partnership | apiâapplication programming interface | bbâbaseband | cpriâCommon Public Radio Interface | cwdmâcoarse wavelength division multiplexing | dwdmâdense wavelength division multiplexing | epcâEvolved Packet Core | ftthâfiber-to-the-home | mimoâmultiple-input, multiple-output | mplsâmulti-protocol label switching | mtcâmachine-type communication | nfvâNetwork Functions Virtualization | ngmnâNext Generation Mobile Networks | ng-pon2ânext-generation passive optical network | p routerâprovider router | pe routerâprovider edge router | pgwâpdn gateway | roadmâreconfigurable optical add/drop multiplexer | sdnâsoftware-defined networking | slaâService Level Agreement | ueâuser equipment
- 4. â± A FLEXIBLE TRANSPORT NETWORK 4 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 5G radio and deployment models Legacy and migration Services and flexibility Affordable and sustainable Technological advances Abstraction and programmability 5G transport Figure 1 Landscape for 5G transport
- 5. OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 5 The5Gtransportnetwork As5Gradio-accesstechnologiesdevelop,transport networkswillneedtoadapttoanewandchallenging landscape,asillustratedinFigureâŻ1. Services Theexpectationsfor5Gnetworksarehighâ providingsupportforamassiverangeofservices. Industrytransformation,digitalization,theglobal dependenceonmobilebroadband,mtc,theiot, andtheriseofinnovativeindustrialapplications allrequirenewservices,whichhasaconsiderable impactonthetransportnetwork.Forexample,anew radio-accessmodelthatsupportshighlyscalable videodistributionormassivemtc datauploading mightrequireadditionaltransportfacilitiesâsuchas ascalablewaytoprovidemulticasting. 5Gradio Howthe5Gradioisdeployeddeterminesthelevelof flexibilityneededinthetransportnetwork.Capacity, multi-siteandmulti-accessconnectivity,reliability, interference,inter-sitecoordination,andbandwidth requirementsintheradioenvironmentplacetough demandsontransportnetworks. In5G,traditionalmacronetworksmightbe densified,andcomplementedthroughtheaddition ofsmallcells.Highercapacityintheradiowillbe providedthroughadvancesinradiotechnology, likemulti-usermimoandbeamforming,aswellas theavailabilityofnewandwiderspectrumbands [4].Consequently,thecapacityofthe5Gradio environmentwillreachveryhighlevels,requiring transportnetworkstoadapt.Notonlywilltransport servealargenumberofradiosites,buteachsitewill supportmassivetrafficvolumes,whichmightbe highlyburstyduetothepeakrateavailablein5G. Forexample,aue thatisconnectedtoanumber ofsitessimultaneously,mayalsobeconnectedto severaldifferentaccesstechnologies.Thedevice maybeconnectedtoamacrooverlte,andtoa smallcellusinganew5Gradio-accesstechnology. Multi-siteandmulti-rat connectivityprovides greaterflexibilityintermsofhowuesconnectto thenetworkandhowe2e servicesaresetupacross radioandtransport.Forexample,allowingfor efficientloadbalancingofuesamongbasestations notonlyimprovesuserexperience,italsoimproves connectionperformance. Theimpactofinterferencemayfavordeployment modelswherecoordinationcanbehandledmore effectively.Insmall-celldeployments,uesare oftenwithinreachofanumberofbasestations, whichincreasesthelevelofinterference,andat timesrequiresradiocoordinationcapabilitiesfor mitigation.However,themethodusedforhandling interferencedependsonhowtransportconnectivity isdeployed.Inacentralizedbasebanddeployment, tightcoordinationfeatures,suchasjointprocessing, canbeimplemented.IntraditionalEthernetand ip-basedbackhaul,tightcoordinationrequireslow- latencylateralconnectionsbetweenparticipating basestations. Centralizedbasebandprocessingtendsto resultinloweroperationalcosts,whichmakes thisapproachinteresting.However,ittypically comesatthecostofhighcpri bandwidthsinthe transportnetwork.Thehighbandwidth,together withstringentdelayandjitterrequirements,makes dedicatedopticalconnectivityapreferredsolution forfronthaul. In5Gnetworks,thebandwidthrequirementsfor fronthaulcouldbeveryhigh.Thedemandwillbe createdby,forexample,antennasformu-mimo and beamformingâwhichcoulduseintheorderof100 antennaelementsateachlocation.Incombination withdensedeploymentsandwiderfrequency bands(inthe100MHzrange)traditionalcpri capacityrequirementscanquicklyreachlevelsof severalTbps.Anewsplitofran functionalityis underinvestigationtosatisfyrequirementsforcost- effectivedeploymentsandradioperformance,while keepingcapacityrequirementsontransportwithina manageablerange. Butsomeprimarynetworkingprinciplesremain valid,suchastimingandsynchronization.Defining newpacket-basedfronthaulandmidhaulinterfaces requirestheunderlyingnetworktoincludeprotocols andfunctionsfortime-sensitivetransportservices. Relatedstandardizationeffortsarecurrently underway [5].
- 6. â± A FLEXIBLE TRANSPORT NETWORK 6 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 Fronthaul Backhaul Packet Packet Wireline access CWDM/DWDM dedicated fiber Access Aggregation Core Data center Data center Data center Service edge BB IP IP IP IP Internet DWDM CWDM/ DWDM Figure 2 Main technology options to connect ran and transport infrastructure Abstractionandprogrammability Abstractingnetworkresourcesandfunctionality, aswellasmanagingserviceson-the-flythrough programmaticapisarethepillarsofsdn,andthe sourceofitspromisetoreducenetworkcomplexity, andincreaseflexibility. Withanewsplitintheran,somefunctionscan bedeployedongeneral-purposehardware,while others,thoseclosertotheairinterfacewithstrict real-timecharacteristics,shouldcontinuetobe deployedonspecializedhardware.Mostofthe functionsoftheepc willbedeployedassoftware âfollowingtheconceptofNetworkFunctions Virtualization(nfv).Deployingnetworkfunctions inthiswaymakesitpossibletobuildend-to-end networkslicesthatarecustomizedforspecific servicesandapplications.Eachlayerofthenetwork slice,includingthetransportlayer,willbedesigned tomeetaspecificsetofperformancecharacteristics. Thesignificanceofnetworkslicesisbest illustratedbycomparingapplicationswithdifferent requirements.Anetworkofsensors,forexample,
- 7. OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 7 requiresthecapabilitytocapturedatafromavast amountofdevices.Inthisinstance,theneedfor capacityandmobilityisnotsignificant.Media distribution,ontheotherhand,ischallengedby largecapacityrequirements(whichcanbeeased throughdistributedcaching),whereasthenetwork characteristicsforremote-controlapplications basedonreal-timevideoarehighbandwidthand lowlatency. Froma5G-transportperspective,thereisaneed toprovideefficientmethodsfornetworksharing, sothatapplicationsliketheseâeachwiththeir individualrequirements,includingmechanismsto satisfytrafficisolationandsla fulfillmentâcanbe supportedforseveralclients.Inaddition,distributed networkfunctionsneedtobeconnectedoverlinks thatfulfillsetperformancelevelsforbandwidth, delay,andavailability. Transportnetworkswillneedtoexhibitahigh degreeofflexibilitytosupportnewservices. Tothisend,keyfeaturesareabstractionand programmabilityinallaspectsofnetworkingânot justconnectivitybutalsostorageandprocessing. Legacy,migration,andnewtechnologies Themaintechnologiesthatcontributeto performanceenhancementandthenetwork segmentâaccess,aggregation,orcoreâtheyapply toareoutlinedinFigureâŻ2.5Gtransportwillbea mixoflegacyandnewtechnologies.Long-term, networkevolutionplanstendtoincludefiber-to- the-endpoint.Inpractice,however,providing small-cellconnectivityrequiresthatlocalconditions betakenintoconsideration,whichresultsinthe needforseveraltechnologiesâsuchascopper, wirelesslinks,self-backhauling,andfree-space optoâtobeincludedintheconnectivitysolution. Re-useofexistingfixedaccessinfrastructure [6]and systemswillbeimportant,andnewtechnologies andsystemsmayinturnprovidemoreefficientuse ofavailableinfrastructure.Forexample,additional capacitycanbeprovidedbyextendingtheuseof cwdm anddwdm closertotheaccesssegmentof thenetwork.Atthesametime,interworkingwith ip isessentialtoprovideend-to-endcontrol,andto ensurethatthefiberinfrastructureisusedefficiently. Existinginfrastructure, togetherwithoperator preferences,determines thenecessaryevolution steps,andhowthe migrationprocess fromlegacytodesired architectureshouldproceed. Thedesignof5Gtransportnetworkswillneedto continuetobeaffordableandsustainable,keeping thecostperbittransportedcontained.Handling legacyinasmartway,andintegratingsustainable advancesintechnologyintopacketandoptical networkswillhelptokeepalidoncosts. Programmablecontrolandmanagement Flexibilitythroughprogrammabilityisasignificant characteristicthatwillenable5Gtransportnetworks tosupportshorttimetomarketfornewservicesand efficientscaling. Programmabilitygearsupnetworks,sothey cantakeoninnovationsrapidly,andadaptto continuouslychangingnetworkrequirements.A coupleofcapabilitiesneedtobedeterminedto enableprogrammabilityfortransportnetworks: ăă therequireddegreeofflexibilityorabilityto reconfigure ăă thelayerorlayersthatneedtobeprogrammable. Determiningthesecapabilitiesisatrade-off betweenneedandgain;inotherwords,howdoes thebenefitofprogrammabilitycomparewiththe costofthetechnologyneededtoprovideit?A significantfactorfortransportprovidersinweighing upneedagainstgainishowtoaddresspacket- opticalintegration.Thisisbecauseextending programmabilitytotheopticallayernotonly providesgreaterflexibilityandeaseofprovisioning toallocatetransportbandwidth;italsosimplifies theprocessofoffloadingthepacketlayerthrough optical/routerbypass,aswellasprovidingimproved cross-layerresiliencemechanisms [7]. Thetelecomindustryhaslongsetitselftwo principaltargetsfortransportnetworks:efficient resourceutilization,anddynamicservice provisioningandscaling.Whilethesegoalsstill PROGRAMMABILITY IN 5G TRANSPORT NETWORKS WILL IMPROVE FLEXIBILITY
- 8. â± A FLEXIBLE TRANSPORT NETWORK 8 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 stand,theyneedtoberevisedcontinuallytomatch thechangingneedsofclientlayers.Theseneeds includetheshortreactiontimesdemandedby modernapplications,andthefactthatdifferent clientswillneedtointerfacewiththenetworkat differentlayers.Addconnectioncapabilitieslike bandwidthandlatencyintothemix,andtheneedfor networkprogrammabilitybecomesmoreevident. Sojusthowdoesincreasednetwork programmabilityhelpthetelecomindustrymeet thetargetsithassetforitself,giventheneedfor differentperformancecharacteristicsfordifferent applications? Efficientresourceutilization Transportprogrammabilityenablesnetwork operatorstoexploittrafficdynamicitytooptimize theutilizationofresourcesacrossdifferentsegments ofthenetwork. Aprogrammabletransportnetworkfacilitates thedivisionoftransportresourcesintomultiple (isolated)slices.Theseslicescanbeallocatedto differentclientsâenterprisesorserviceprovidersâ enablingefficientsharingofresources. Dynamicserviceprovisioningandscaling Beingabletoprovisionresourcesontheflyis particularlycrucialfordynamicservicechaining, whichinvolvesinterconnectingdistributed, virtualizednetworkfunctionsandultimately facilitatingdynamicservicecreation.Inparticular, establishingconnectionservicesacrossseveral networkingdomainshaslongbeenachallengeâ hereenhancedprogrammabilitycanmakesuch proceduresmoreefficient.Inmostcases,flow controlinthetransportdomainshouldbecarried outonaggregatedtraffictoavoiddetailedsteering forindividualuserswhenitisnotneeded. Aprogrammabletransportnetworkenables thecapacityallocatedtoaservicetobescaledup ordown,whenandwhereitisneededacrossthe networkâinotherwords,providingelasticservices. Centralizedordistributedcontrol Controlplaysanessentialroleinprogrammability. Networkcontrolcanbecentralizedordistributed, andnetworksareoperateddifferentlydependingon theapproachused. Centralizedcontrolâtheconceptusedinsdn âenablesshorterservicedevelopmentcycles andspeedierrolloutofnewcontrolfunctionality (implementationoccursonceinthecentralstack). Fornetworksbuiltwithadistributedcontrol plane,changesmustbemadeinmultipleâalready deployedâcontrolstacks(especiallyinmulti- providernetworks). Thetopicofsdn isbeingdiscussedinthetelecom industryasapromisingtoolsettofacilitatenetwork programmability.Insdn architecture,themain intelligenceofnetworkcontrolisdecoupledfrom dataplaneelementsandplacedintoalogically centralizedremotecontroller:thesdn controller (sdnc).Assuch,thesdncprovidesaprogrammatic api,whichexposesabstractednetworking infrastructurecapabilitiestohigherlayercontrol applicationsandservices,enablingthemto dynamicallyprogramnetworkresources. Theroleoftheapi insdn goesbeyondtraditional networkcontrol.Itallowsapplicationstobe deployedontopofthecontrolinfrastructure,which enablesresourcestobeautomaticallyoptimized acrossheterogeneousnetworkdomains,andnew end-to-endservicestobeinstantiatedeasily.The control/managementsystemneedstoprovide methodsforcontrollingresourcesandforexposing infrastructurecapabilitiesâusingtheright abstractionwiththelevelofdetailsuitableforhigher layerapplications. Tohighlightthispoint,inourresearchwechose toexemplifythecaseofresourceandservice orchestrationacrossmultiplenetworkdomainswith heterogeneoustypesofresources.Theresulting hierarchicalsdn-basedcontrolarchitecture,which orchestratesacrossthreedomainsâtransport,radio accessnetworks(rans),andcloudâisshownin FigureâŻ3.Amanagementfunction [8],whichcanbe partlyoverlapping,isincludedbutnotdiscussedin detailinthisarticle. sdn flavors Theimpactofupgradingthecontrolplaneofalegacy transportnetworktosdn dependsonanumber
- 9. A FLEXIBLE TRANSPORT NETWORK â± OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 9 Transport edge Network app 1 Network app n RAN controller Transport controller Orchestrator Integrated packet-optical transport Cloud controller Edge router Service edge PGW Transport edge Transport switching Transport switching Transport edge Packet microwave Fixed Enterprise IP IP IPBB BB Figure 3 Hierarchical sdn control architecture for multi- domain orchestration
- 10. â± A FLEXIBLE TRANSPORT NETWORK 10 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 Optical networks Implementation SDN controlled functions Node local functions Management controlled functions Low Legacy Legacy + CMPLS (Full) SDN High/moderate Low Features Node complexity Figure 4a Centralizing control functionality in the optical domain Packet networks Implementation SDN controlled functions Node local functions (protocol driven) Management system driven functions High Legacy Hybrid SDN Full SDN Moderate Low Features Node complexity Figure 4b Centralizing control functionality in the packet domain
- 11. A FLEXIBLE TRANSPORT NETWORK â± OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 11 ofaspects,butprimarilyonthedegreetowhich forwardingandcontrolfunctionsareintegratedin legacytransportnetworks. Inlegacyopticaltransportnetworks,mostcontrol functionsarealreadyseparatedfromthedataplane nodes.However,inpacket-switchedtransport nodes,thetwoplanesaretightlycoupled.Assuch, introducingafullycentralizedsdn controlplane(full sdn)ismorestraightforwardforopticaltransport thanpacketnetworks. Tointegratelegacyopticaltransportnetworks, asillustratedinFigureâŻ4a,thesdncneedstobe developedalongwithsuitableinterfaces,butitdoes notnecessarilyrequiredisruptivechangestothe opticalnodes. Whenappliedtopacketnetworks,thedisruption createdbysdn issignificant.Amorenatural approachforthepacketdomainwouldbeto centralizeselectedelementsofthecontrolfunctions. Theresultinghybrid-sdn alternativesareillustrated inFigureâŻ4b.Ideally,controloverservice-related functionsshouldbecentralizedwiththesdnc,while transport-relatedfunctionsshouldbeimplemented locallyonthenode. Thedecisionofwheretoplaceacontrol-plane functionorfeatureisoperatorspecific,depending onmanyfactors,liketheavailablefeatureset,and operationalpreferences. Inpacket-basedtransportnetworks,theconcept ofseparatingtransport-andservice-related functionsiswellestablished,whereaclearlogical differentiationismadebetweenserviceunaware transportnodesandservicenodesâsuchasp andpe routersinmpls networks.Onlyservicenodeshold servicestatesandrequireimplementationofservice- relatedfunctions.Suchseparationisafuture-proof conceptandonethatshouldremainintact.Any improvementsinthisareashouldfocusontransport servicefunctions,astheycausemostofthe challengesinbuildingandoperatingnetworksand maketheintroductionofnewserviceslengthyand costlyâespeciallyinmulti-vendorenvironments. Flexibletransportplane Severalfactorscontributetonetworkdynamicityâ theabilityofanetworktoadaptrapidlytochanging demand.Theintroductionof5Gradiotechnologies andthelaunchofnewservicesarethetwomain factorspushingtheneedfornetworkstobemore dynamic,andconsequentlytheneedforamore flexibletransportplane.Thereare,however,many otherfactorscontributingtonetworkdynamicity: ăă resourcedynamicity:on-the-flyadditionandremovalof connectivity,compute,andstorageresources ăă trafficdynamicity:responsivenesstofluctuatingtraffic patternsthatresultfromusermovement/migration,or variationsinuseractivity [9] ăă servicedynamicity:responsivenesstoserviceusage patternswithwidelyvaryingresourcerequirements ăă failuresandservicewindows:abilitytoreroutetraffic andminimizeimpactofdowntime ăă weatherconditions:managingtheeffect ofrainor fogonperformanceformicrowaveorfree-spaceopto networks. Expertopiniondiffersonhowaccessandtransport architectureswillevolvetomeetfuturemobile requirements,andinparticularhowtheywill providesupportforsmallcells.Legacynetworks typicallyconsistofseparatebranchesforfixed (residential/businessservices)andmobileaccess. Continueddensificationofmobilenetworksis likelytoresultintheuseofseveraldifferentsmall- celltransporttechnologiesâeachoneadaptedfor specificnetworkconditions. Inparticular,theadoptionofwirelessbackhaul/ fronthaultechnologies,suchasnlos,for provisioningconnectivitytonewsmall-cellsites,will becomemoreprevalent.Atthesametime,thefixed- accessinfrastructureanditswidespreadavailability willcontinuetobevaluableforprovidingsmall-cell connectivity,pushingtheneedforfixedandmobile networkconvergence. Howfixed/mobileconvergencemightevolve dependsonexistingfixedaccessinfrastructure. Manyoperatorshavebeenreluctanttoinvestin deepfibertechnologies,likeftth,duetothecosts associatedwithdeployment,andhaveinstead turnedtoalternativeslikecopper-baseddroplinks usingdsl orcat5/6.Thistypeofarchitectureor activeopticalnetworkreliesonthepresenceofa largenumberofdistributedactivenodes.
- 12. â± A FLEXIBLE TRANSPORT NETWORK 12 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 Converged transport platform Wireless Wireless a) b) Converged aggregation Common access solution Macro Outdoor Macro Outdoor Small cell transport Small cell transport Access system Business network Home network Business network Home network Indoor Indoor Device HouseholdIndoorsiteBusinessO utdoorsite M acro Centraloffice Edge Public Residential Business Public Residential Business Figure 5 Different architectural avenues with scenarios based on: (a) a converged transport platform (b) a common access solution FigureâŻ5illustratestwoevolutionscenariosforfixed/ mobileconvergence.Differentoptionsareavailable forprovidingconvergedaccessinfrastructure fortraditionalresidentialandbusinessaccess services,aswellasip-basedbackhauland cpri-basedfronthaul [6].Inthebottompart(b)of theillustration,theconnectivityneedsoftheran areservedthroughacommonaccesssolution. Here,thechallengeistodefineasystemthatcan simultaneouslymeetthecostpointsofresidential
- 13. A FLEXIBLE TRANSPORT NETWORK â± OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 13 accessandtheperformancerequirementsfor differentran deployments.Asillustratedinthe tophalf(a)ofFigureâŻ5,evolvingnetworksinthis mannerpavesthewayforaconvergedtransport platform(possiblyincludingsmall-cellfronthaul) undercommoncontrolbutwithasomewhatdiverse dataplane,subjecttorequirementsfordifferent segments.Inreality,manymorescenariosand combinationsexistthanareillustratedhere,andthe choiceofarchitecturalinfrastructuremodel,ran deploymentmodel,andtechnologyareallclosely interlinked.Inturn,thedecisionsmadefornetwork architectureandtechnologiesdeterminethedegree offlexibilitythattransportcanoffer,whetheritisat thepacketorwavelengthlevel. Inaconvergedscenario,onepossiblesolution istodeploynodescapableofprovidingcommon switchingofpacketandfronthaulâwhichtoday areseparatedomainsthatusedifferenttransport protocols(Ethernetandcpri)withtheirown specificrequirements.TomultiplexEthernetand cpri,switchingatwavelengthandpacketlayerscan becombined:thechallengeistomeetlatencyand jitterrequirementsfortime-sensitiveapplications. Deterministicdelayswitchingusingclientagnostic framesisanalternativetopacketforscenarios whereexistingdwdm/otn metroinfrastructure isusedsimultaneouslyforbackhaulandfronthaul applications. Foropticalinterfaces,fiberrichdeployments canbenefitfromrecentdevelopmentsofgrey100G and400Gopticalinterconnectioninterfaces.This isanactivefieldofresearch,andmanysolutions, standardizedandproprietary,arebeingexplored. Insome,modulationformatsarenativelydesigned todynamicallyadjustthebandwidthaccording toreal-timenetworkingneeds.Integrated photonictechnologiesarechangingtheoptical communicationsindustryoutlook,promising adramaticreductionofhardwarecost,power consumption,andfootprint,butalsoenabling flexibilityatlowercost.Multi-channeltransceivers andtunablelasersareamongthefirstapplications targetedbyintegratedphotonics,asdemonstrated bystandardizationactivityonng-pon2andG.metro. Alongthesametechnologicaltrend,Ericsson hasdefinedanewtypeofdeviceâanintegrated reconfigurableopticaladd-dropmultiplexertailored tothespecificneedsofradioaccess.Suchadevice wouldprovideflexibilityinthewavelengthlayerand wouldbeanorderofmagnitudesimplerandcheaper thanconventionalroadms. Conclusions Thefirst5Gnetworktrialsarealreadyongoingona smallscale,andcommercialsystemsareexpected in2020.Comparing5Gwithpreviousgenerations showsthatitisnotjustanewradio-access technologyâsomuchmoreisexpectedofit.5Gis shapinguptoprovidecost-effectiveandsustainable wirelessconnectivitytobillionsofthings,people, enterprises,applications,andplacesaroundthe world.Tomakethemostofthisbusinessopportunity anddeliverconnectivitytobillionsofdevices, thearchitectureof5Gsystemsâandtransportin particularâneedstobebuiltforflexibilitythrough programmability. Deliveringtherequiredlevelofflexibility,needs tighterintegrationbetween5Gradio,transport networks,andcloudinfrastructure.Thismust becarriedoutwithabackdropofsmall-cell deployment,convergenceofaccessandbackhaul, andmigrationoflegacyequipmentandtechnologies âwhilecontainingcosts. Whenitcomestoprogrammability,the expectationsplacedonsdn technologytodeliver areenormous.sdn alsobringsservicevelocity withit,aswellasameanstointegratetransport, radio,andclouddomains.However,adoptinga hybrid-sdn alternativemightbebesttomitigate thedisruptionsdn causeswhenappliedtopacket networks.Thisapproachenablescontroltobe centralizedforservicefunctionsanddistributedfor transportâgainingadegreeofflexibilitywithoutthe disruption. Tomeetcapacitydemands,increasingtheuseof dwdm closertoaccesswillbefeasiblewhenflexible opticsbecomemorecost-efficient.Inshort,themajor challengesfor5Gtransportareprogrammability, flexibility,andfindingtherightbalanceofpacket andopticaltechnologiestoprovidethecapacity demandedbytheNetworkedSociety.
- 14. â± A FLEXIBLE TRANSPORT NETWORK 14 ERICSSON TECHNOLOGY REVIEW â± OCTOBER 7, 2015 Peter ĂhlĂ©n â is a principal researcher within IP and transport, managing research efforts across network and cloud domains. His current research focuses on transport network solutions for 5G, and integrating heterogeneous technology domains â transport network, radio and cloud. He joined Ericsson in 2005, and has worked in a variety of technology areas such as 3G radio, HSPA fixed-wireless- access, fiber access, IP and optical networks. He holds a Ph.D. (2000) in photonics from the Royal Institute of Technology (KTH) in Stockholm, Sweden. Björn Skubic â is a senior researcher in IP and transport, and is currently managing activities in 5G transport. He joined Ericsson in 2008, and has worked in areas such as optical transport, energy efficiency and fixed access. He holds a Ph.D. in physics from Uppsala University, Sweden. Ahmad Rostami â is a senior researcher at Ericsson Research, where he manages activities in the area of programmable 5G transport networks and radio-transport-cloud orchestration. Before joining Ericsson in 2014, he worked at the Technical University of Berlin (TUB) as a senior researcher and lecturer. At the university, his areas of interest covered sdn as well as the design and performance evaluation of broadband communication networks. In 2010, he received a Ph.D. from the TUB Faculty of Electrical Engineering and Computer Science for his work on control of optical burst switched networks. Rostami holds an M.Sc. in electronic engineering from Tehran Polytechnic, Iran. theauthors References 1. 5G PPP, March 2015, 5G vision: the next generation of communication networks and services, available at: https://5g-ppp.eu/wp-content/ uploads/2015/02/5G-Vision-Brochure-v1. pdf#page=8 2. NGMN Alliance, February 2015, NGNM 5G White Paper, available at: https://www.ngmn.org/uploads/media/ NGMN_5G_White_Paper_V1_0.pdf 3. Ericsson Review, November 2014, Wireless backhaul in future heterogeneous networks, available at: http://www.ericsson.com/news/141114- wireless-backhaul-in-future-heterogeneous- networks_244099435_c 4. Ericsson Review, June 2014, 5G radio access, available at: http://www.ericsson.com/news/140618-5g-radio- access_244099437_c 5. IEEE, 802.1CM - Time-Sensitive Networking for Fronthaul 6. COMBO FP7 project: Convergence of fixed and Mobile Broadband access/aggregation networks, more information can be found on: http://www.ict-combo.eu 7. Ericsson Review, May 2014, IP-optical convergence: a complete solution, available at: http://www.ericsson.com/news/140528-er-ip- optical-convergence_244099437_c 8. Ericsson Review, Nov. 2014, Architecture evolution for automation and network programmability, available at: http://www.ericsson.com/news/141128-er- architecture-evolution_244099435_c 9. Ericsson, May 2015, Research Blog, Transport, Radio and Cloud Orchestration with SDN, available at: http://www.ericsson.com/research-blog/5g/ transport-radio-and-cloud-orchestration-with- sdn/
- 15. A FLEXIBLE TRANSPORT NETWORK â± OCTOBER 7, 2015 â± ERICSSON TECHNOLOGY REVIEW 15 Neiva Fonseca Lindqvist â is a senior researcher in ran transport solutions, with a particular interest in heterogeneous networks and the evolution to 5G. She joined Ericsson in 2011, working with fixed and mobile backhaul network architectures. Previously, she worked in research in the area of signal processing for broadband communication over copper access networks and held a postdoctoral position at the EITâ LTH Faculty of Engineering, Lund University, Sweden. Fonseca Lindqvist holds a Ph.D. in electrical engineering and telecommunication from the Federal University of Para (UFPA), BelĂ©m, Brazil. Kim Laraqui â is a principal researcher in mobile backhaul and fronthaul solutions for heterogeneous networks. He joined Ericsson in 2008 as a regional senior customer solution manager. Prior to this, he was a senior consultant on network solutions, design, deployment, and operations for mobile and fixed operators worldwide. He holds an M.Sc. in computer science and engineering from KTH Royal Institute of Technology, Stockholm, Sweden. Fabio Cavaliere â joined Ericsson Research in 2005. He is an expert in photonic systems and technologies, focusing on WDM metro solutions for aggregation and backhauling networks and ultra-high-speed optical transmission. He is the author of several publications, and is responsible for various patents and standardization contributions in the area of optical communications systems. He holds a D.Eng. in telecommunications engineering from the University of Pisa, Italy. BalĂĄzs Varga â joined Ericsson in 2010. He is an expert in multiservice networks at Ericsson Research. His focus is on packet evolution studies to integrate IP, Ethernet, and mpls technologies for converged mobile and fixed network architectures. Prior to joining Ericsson, Varga worked for Magyar Telekom on the enhancement of its broadband services portfolio and introduction of new broadband technologies. He has many years of experience in fixed and mobile telecommunication and also represents Ericsson in standardization. He holds a Ph.D. in telecommunication from the Budapest University of Technology and Economics, Hungary.
- 16. ⱠA FLEXIBLE TRANSPORT NETWORK 16 ERICSSON TECHNOLOGY REVIEW ⱠOCTOBER 7, 2015 ISSN 0014-0171 284 23-3260 | Uen © Ericsson AB 2015 Ericsson SE-164 83 Stockholm, Sweden Phone: + 46 10 719 0000