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WimRouwet
NXPSemiconductors,Austin,TX,UnitedStates
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1.Openradioaccessnetworkoverview1
TheOpenRadioAccessNetworksAlliance1 OnC-RAN,OpenvRAN,OpenRAN,xRAN,and TelecommunicationsInfrastructureProject7 Spectrum:enabling5G8 Traditionalbasestationarchitectures14 5Gbasestationarchitectures17 Functionalsplits20 CoordinatedMultipoint28
2.Systemcomponents,requirements,andinterfaces43 Next-GenerationRadioAccessNetworkoverviewand terminology43 Centralunit48 Distributedunit59 Radiounit76
Distributedunit/radiounitinterface,EnhancedCommon PublicRadioInterfaceprotocoloverview86
Initialaccess87
802.1CM91
Fronthaulgateway94
Cellsiterouter/gateway95
Formfactor,environmentalandpowerrequirements96
ASN.196
DiffServ97
References102
3.Hardwaresystemdimensioning103
Centralized/distributedunituse-casedimensioningfor throughput103
Use-casedimensioningforlatency108
Users/transmissiontimeinterval110
eCPRI,fronthaulbandwidthandlatency112
DistributedunitinternalIO115
Memorydimensioning117
HARQprocesscountdimensioning126
Radiounit127
References137 Furtherreading137
4.Hardwarearchitecturechoices139
Scalability139
Developmentcycle141
Datacenterarchitecture142
Cellsiteintegrated(CU/DU)solutions146 Radiounit154
Integratedsmallcell172
5.Systemsoftware183
6.User-planeapplicationcomponents215 GTPProtocol215 PDCPprotocol217 RLCProtocol220 MACprotocol222 eCPRIprotocoloverview223
Lowphysicallayer228 Digitalfront-end230 References234 Furtherreading235
7.WirelessschedulingandQualityofService optimizationtechniques237
Orthogonalfrequencydivisionmultipleaccess237
Basestationscheduleralgorithms242
Architecturalframeworkforthebasestationwirelessscheduler algorithm249
System-leveloptimization254
Softwareoptimizationtechniques257
References260
Furtherreading262
8.Synchronizationinopenradioaccessnetworks265
Understandingfrequency,time,syntonization,and synchronization265
Howdowegettime?269
O-RANsynchronization273
Cellularnetworksynchronizationrequirements290
SynchronizationinO-RAN292
O-RANnetwork-levelsynchronization292
O-RANsyncequipmentrequirements296
Syncsolutionimplementation298
Theeffectsoftimestampinglocationandresolution303
Unravelingthestandardsspaghetti305
Furtherreading306
9.Softwareperformance309
Packetprocessingcyclebudgetanalysis310
PhysicalLayercomplexityanalysis313
CentralProcessingUnitloadingsummary319
System-on-Chipperformancecounters319
Life-of-a-packetdoubledatarateutilizationanalysis320
Mitigationtechniques:whatiftheproductdoesnotmeet performancetargets?320
Developmentenvironmentoptimization321
Softwareoptimizationtechniques322 Reference327
10.Interoperabilityandtest329
Developmenttesting329
Systemtestsetup332
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Abouttheauthors
WimRouwet isadistinguishedmemberoftechnicalstaffatNXPSemiconductors.Hehas anMScinelectricalengineeringfromtheEindhovenUniversityofTechnologyinthe Netherlands.Hehadspentmorethan15yearsinMotorola,Freescale,andNXPinnetworkingandnetworkprocessing,wirelessalgorithmdevelopment,andsystemandmodemarchitectureroles.Hisfocusison3GPPLTEand5Gaswellas802.11processingstacksandtheir implementation.Inhisjob,hehasbeenresponsiblefor4Gand5Gstackdevelopment,small cells,andCRANimplementationsassociatedwithmanywirelessinfrastructureprojects.He hasledkeynext-generationR&Dprojectsincludingmultistandardmodemarchitecture,virtualization,5Gmacroandsmallcell,andclient-sideproducts.
ContributingAuthors
DavidSpencer isaproductlinemanagerforTimingSolutionsatSkyworksInc.,formerly SiliconLabsI&Adivision.Hehasadegreeinphysicsandanover30-yearcareerintechnologyspanningtechnicalwriting,hardwareandsoftwaredesign,applicationsengineering,and productmarketing.Forthepast15years,Davidhasfocusedonsynchronizationsolutions andisconsideredanexpertinbothphysicallayersynctechnologiesandIEEE1588packetbasedtiming,havingpresentedpapersatmultipleinternationalconferencessuchasWSTS andITSFandrepresentedvariouscompaniesintheITU-Tstandardsbody.Inhiscurrent role,Davidisresponsiblefordrivingthedefinitionandimplementationofhardwareand softwareenablingSynchronousEthernetandIEEE1588syncinawiderangeofsystems including5GRANnetworks.
VishwapathiRaoTadinada worksasadirectoroftestatNXPSemiconductorswherehehas toensurethequalityofnetworkingapplicationsandcustomersolutionproductlines.Hehas over20yearsofextensiveexperienceleadingproducttestingin4G,5G,Security, Networking,Cloud,SDN,NFV,andEmbeddedIndustry.Hehasseveralpresentationsat internationalconferencesandpapersonIoT,security,andvirtualization.HehasBScfrom KanpurUniversity,India.
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Preface
AcrosstheIoT,AutonomousDriving(ADAS),edgecompute,andserviceproviderecosystem, 5Gisunderstoodtonot “just” beaboutenablingafasterdataconnectiontotheend-user device.5Gevolvesbothexistingtechnologies(radioaccessandhomenetworks)whilelaying thefoundationfornewapplicationsacrossconsumerandindustrialautomationwiththe self-drivingcarbeingaprimeexample.
Eventhough5Gisverymuchhypedsince2016,infrastructurerollouthasonlystartedin 2019,withsubscriberdeviceshavingbecomeavailableinvolumestarting2020.Atthesame time,4G/LTEstandardswillcontinuetoevolveandaddmoresubscribers.
4Gand5G(projected)subscribergrowth(multiplepublicsources,indicatedwithdatapoints).
During2G,3G,and4Gnetworkrollouts,wirelessserviceprovidersandtheirsystemvendorsbuiltnetworksthat,althoughprovidingpredictableandhighperformance,areoften characterizedbytheircomplexity,inflexibility,andassociatedhighbarriertoentrance.
Likethewirelinenetworktransformationwhenmigratingfromcircuit-switchedtopacketswitched(PS)networksintheearly2000s,thewirelessnetworkismigratingfromthisproprietarynaturetoatrueopen-standardsapproachthatallows “out-of-the-box” thinkingand disruptivesolutionsinphysicalimplementationanddeployment.Consider,forexample,the costandexecutionrequirementsimposedbynewoperatorslikeRelianceJioinIndia,DISH intheUnitedStates,andRakuteninJapan,needingtosupportfastramp-up(quickprovisioning),ortheFacebookTerragraphproject,bringinghigh-speedconnectivityatafraction offiberdeploymentcostthroughtheuseofanunlicensed60GHzspectrum.
Therapidevolutionof5Gstandardscombinedwithaggressivedeploymentschedules andcosttargetsdrivesapushforRadioAccessNetwork(RAN)implementationsonstandard hardwareandsoftwareplatforms.Thistrendstartedwith4Gnetworkswhereupperlayer stacksareimplementedongeneralpurpose(GPP)computeplatformsandtheLinuxoperatingsystem(OS)andisincreasingwith5Gdeployments.Examplesincludethetrendto EthernetforfronthaulreplacingquasistandardssuchasCPRIaswellasrigorousstandardizationeffortsin3GPPtodefinestandardAPIsbetweendifferentcomponents.
Becauseofthistrend,systemvendorsaremovingincreasinglyaggressivelytoward SoftwareDefinedRadio(SDR)platformswheremost,ifnotall,oftheRANMACandPHY layersareimplementedinatruesoftwareenvironmentontheLinuxOS.Theexpectationis thatalthoughtheimplementationefficiencymaynotmatchthatofcustomhardwareand firmware,thisisoffsetbycostandflexibilityprovidedbySDRplatformsthroughtheuseof GPPmulticoredevicesandbroadsoftwareenablement.On-chipintegrationofhigh-speed (25 100Gbps)EthernethardwarereducestheneedforcustomI/Osolutionsandallowsfor reuseofdatacenterswitch/routingsolutionsforfronthaul.
ThetrendforSDRevenextendstotheremoteradiohead/radiounit(RU).Verylarge computerequirementsmakeitimpossibleforprogrammablecores(DSPs)toimplementdigitalfrontend(DFE)functionsasopposedtoASICimplementation.OptimizedvectorDSPs allowforasoftware-friendlyandflexibledeployment,whilenewchip-levelpartitioning,with on-chipdataconverterintegration,modernmemoryinterfaces,multi-chipintegration,and otherinnovativetechniques,enablethecostreductionrequiredformassiveMIMO deployment.
AT&T,ChinaMobile,DeutscheTelekom,NTTDOCOMO,andOrangejointlyannounced thecreationoftheOpen-RAN(O-RAN)AllianceinFebruary2018.PressreleasessaytheORANAllianceisaworldwide,carrier-ledefforttodrivenewlevelsofopennessintheRANof next-generationwirelesssystems.Butwhatdoesthismean?Itmeansthatthreewirelessnetworkingindustrytrendsarecomingtogetherintoa “perfectstorm” moment.First,networkingproductsinthewirelinespace(switches,routers,andsimilarequipment)havemoved fromproprietary,hardware-centricimplementationstoasoftware-centricimplementation thatexecutesongeneral-purpose,Armorx86hardware.Second,thewirelessinfrastructure vendorlandscapehasconsolidateddramatically.ConsiderNokia,whichhasbeenconsolidatingAlcatel,Lucent,Nokia,Nortel,Siemens,andmorecompanies.Wirelessoperators,who arethecustomersoftheseinfrastructurevendors,seeapotentialforanoligopolythat impliesreducedinnovationandincreasedpricingandvendordependency.
Lastly,thereisageopoliticalaspectthatworsensthecompetitivesituation.Therehas beenbroadcoverageonHuaweibeingbannedasaninfrastructurevendor,leadingHuawei customerstoreachouttofindalternativepathstoacquireequipment.
GiventhepromiseofO-RANtoopenupawholenewecosystemofhardwareandsoftwarevendors,thereisobviousexcitementintheindustryaroundtheconceptofasoftwarecentricecosystemofvendorsthatcanbemix-and-matchedtoimplementawirelessnetwork, especiallyifthisallowsthewirelessnetworktobecomposedoutofsystemsthatareoptimizedtothetaskathand sayrural,denseurban,industrial,orprivatenetworks.
Atthesametime,thereisalotofcatchinguptodo.Theinstitutionalizedknowledge fromthebigwirelesssystemsvendorstakesalongtimetocatchupto,insystems,hardware, andsoftwaredesign.Thisbookisajump-starttoengineerswhoaredevelopingO-RANhardwareandsoftwaresystemsandprovidesatop-downapproachtoO-RANsystemsdesign.We coverwirelessandsystemshistoryasanintroductionintowhywirelesssystemslooktheway theydotoday,beforeintroducingrelevantO-RANand3GPPstandards.Theremainderof thebookdiscusseshardwareandsoftwareaspectsofO-RANsystemdesign,including dimensioningandperformancetargets.Weincludereal-lifeexamplesofrelevantelements ofdetailedhardwareandsoftwaredesignwhereneededasaguidefordevelopers.Lastly, weshowafewpracticalexamplesofwhereO-RANdesignsplayinthemarketandhowthose examplesmaptohardwareandsoftwarearchitectures.
Thetargetaudienceincludeshardwareandsoftwareengineersaswellasproductmanagers andconsumersofO-RANproductswhoarelookingtounderstandbetterwhatO-RANis.
Thisbookisorganizedasfollows:
Chapter1, OpenRadioAccessNetworkOverview,givesanoverviewoftheO-RANstandardanditsoriginsandcoversrelatedtopicslike5Gandspectralavailabilityfor5Gdeployment.Thisprovidesabackgroundforadiscussionondeploymentoptions,whichdefines thehardwareandsoftwarearchitecture.
Chapter2, SystemComponents,Requirements,andInterfaces,outlinestherequirements andarchitectureofkeysystemcomponentssuchasthecentralunit(CU),distributedunit (DU)andRU.
Chapter3, HardwareSystemDimensioning,establisheskeyperformancemetricssuchas front/backhaulthroughputs,memoryrequirements,interconnectperformance,aswellas latencyandothermetrics.
Chapter4, HardwareArchitectureChoices,talksaboutthedifferenthardwareimplementationoptions,fromserver-baseddesignstomoreembeddedimplementationoptionsforCU/ DUaswellasoptionsforRUsystemdesign.Wediscusstheprosandconsofeacharchitectureapproach.
Chapter5, SystemSoftware,islikethehardwarearchitecturechoicebutmoresoftware centricinnature.WecoverOScomponentssuchasLinuxandDPDK/bbdevaswellas requiredsoftwaredrivers.
Chapter6, User-PlaneApplicationComponents,coversrelevantdetailsofthePhysicaland Layer2applicationstacks.Weoutlinefunctionsimplementedbythesestacks.Thisincludes 3GPPdefinedfunctionssuchasPDCP,RLC/MAC,andPHYandimplementation-specific partssuchasAirInterfaceScheduler,O-RANeCPRIfronthaul,andDFE.
Chapter7, WirelessSchedulingandQualityofServiceOptimizationTechniques ,delves deeperintothemostcomplexanddifferentiatingpieceoftheUser-Planestack:thewireless scheduleralgorithm.Weexplaincommonlyusedalgorithmsfortimeandfrequencydomain schedulingandoutlinethepotentialstructureofaschedulingalgorithmicframework.
Chapter8, SynchronizationinOpenRadioAccessNetworks,coversrequirementsaswell asimplementationonCU/DUandRUsidefortimeandfrequencysynchronizationincluding relevantstandardsandimplementationmethods.
Chapter9, SoftwarePerformance,discusseskeyperformancemetricsoftheO-RANsystems,suchasL1/L2algorithmicperformanceaswellasuserperformanceintermssuchas latency,throughput,andcapacity.
Chapter10, InteroperabilityandTest,establishesstandardssoftwaretechniquesforintegrationandtestbeforecovering3GPP/O-RANspecificsystemintegrationandtestaspects.
Chapter11, DifferentiationbyUseCase,showsafew “offthenormal” O-RANuse-cases/ implementationstogivethereaderinsightintowhatkindsofproductscanbeestablished withanO-RANsystemsarchitecture.ThesesystemsarediscussedaspracticalimplementationsthatshowcaseO-RANstrengthsofecosystem-baseddevelopmentandsoftware centricity.
Acronyms
3GPP Third-GenerationPartnershipProject
5GC 5GCore
5QI 5GQoSIdentifier
ACIA AllianceforConnectedIndustriesandAutomation
ACL AccessControlLists
ACLR AdjacentChannelLeakageRatio
ACPR AdjacentChannelPowerRatio
ADAS AdvancedDriver-AssistanceSystems
ADC AnalogtoDigitalConverter
AGC AutomaticGainControl
AM AcknowledgedMode
AMF AccessandMobilityManagementFunction
APD AnalogPreDistortion
API ApplicationProgrammingInterface
ARP AllocationandRetentionPriority
ARPU AverageRevenuePerUnit
ARQ AutomaticRepeatRequest
ASIC ApplicationSpecificIntegratedCircuit
ASN1 AbstractSyntaxNotation1
ATM AsynchronousTransferMode
AWGN AdditiveWhiteGaussianNoise
AxC AntennaContainer
BCCH BroadcastControlChannel
BCH BroadcastChannel
BE BestEffort
BER BitErrorRate
BFWA BroadbandFixedWirelessAccess
BLER BlockErrorRate
BPSK BinaryPhase-ShiftKeying
BD BufferDescriptor
BE BestEffort
BS BaseStation
BWP BandwidthPartitioning
CB CodeBlock
CCH CommonControlChannel
CF CrestFactor
CFR CrestFactorReduction
C-ITS CooperativeIntelligentTransportSystems
CLI CommandLineInterface
CoMP CooperativeMultipoint
COTS CommercialOff-The-Shelf
CP ControlPlane
CPI CertifiedProfessionalInstaller
CPU CentralProcessingUnit
CPRI CommonPublicRadioInterface
CRC CyclicRedundancyCheck
CSR CellSiteRouter
CU CentralUnit
D2D DevicetoDevice
DAC DigitaltoAnalogConverter
DAS DistributedAntennaSystem
dB Decibel
DC DualConnectivity
DCCH DedicatedControlChannel
DCI DownlinkControlInformation
DDC DigitalDownConversion
DDR DoubleDataRate
DFE DigitalFrontEnd
DFT DiscreteFourierTransform
DL Downlink
DLSCH DownlinkSharedChannel
DMRS DemodulationReferenceSignal
DPD DigitalPreDistortion
DPDK DataPlaneDevelopmentKit
DRB DataRadioBearer
DRX DiscontinuousReception
DSP DigitalSignalProcessing
DSS DynamicSpectrumSharing
DTCH DedicatedTransportChannel
DTX DiscontinuousTransmission
DU DistributedUnit
DUC DigitalUpConversion
DUT DeviceUnderTest
DVFS DynamicVoltageandFrequencyScaling
EBI EPSBearerID
eCPRI EnhancedCommonPublicRadioInterface
EIRP EffectiveIsotropicRadiatedPower
EMC ElectromagneticCompatibility
eNB EvolvedNodeBor4GBaseStation
EPC EnhancedPacketCore
eSIM ElectronicSubscriberIdentityModule
EMBB EnhancedMobileBroadband
ESMC EthernetSynchronizationMessagingChannel
FAPI FemtoAPI(ApplicationProgrammingInterface)
FCC FederalCommunicationsCommission
FEM FrontEndModule
FDD FrequencyDivisionDuplexing
FFT FastFourierTransform
FGW FemtoGateway
FHGW FronthaulGateway
FIFO FirstIn FirstOut
FPGA FieldProgrammableGateArray
FR FrequencyRange
FWA FixedWirelessAccess
GBR GuaranteedBitRate
GFBR GuaranteedFlowBitRate
GNSS GlobalNavigationbySatelliteSystems
GPP General-PurposeProcessor
GPRS GeneralPacketRadioServices
GPS GlobalPositioningSystem
GSM GlobalSystemforMobilecommunication
GTP GPRSTunnelingProtocol
GTP-C GPRSTunnelingProtocol Control
GTP-U GPRSTunnelingProtocol User
GTPS GigaTransactionsPerSecond
GW Gateway
gNB gNodeBorNextGenerationNodeBor5GBaseStation
HAAT HeightAboveAverageTerrain
HARQ HybridAutomaticRepeatRequest
HBM HighBandwidthMemory
HLS HigherLevelSplit
HNB HomeNodeB
HPF HighPriorityFronthaul
IBW InstantaneousBandWidth
IDFT InverseDiscreteFourierTransform
IPC InterProcessCommunication
IOT InternetofThings
IEEE InstituteofElectricalandElectronicsEngineers
IETF InternetEngineeringTaskForce
IFFT InverseFastFourierTransform
IP InternetProtocolorIngressProtection
IPSec InternetProtocolSecurity
ISA InstructionSetArchitecture
ISC IntegratedSmallCell
ITU InternationalTelecommunicationsUnion
LBRM LimitedBufferRateMatchin
LLR LogLikelihoodRadio
LLS LowerLevelSplit
LPF LowPriorityFronthaul
LTE LongTermEvolution
MAC MediumAccessControl
MEC MetroEdgeCompute
MeNB MastereNB
MFBR MaximumFlowBitRate
MIB MasterInformationBlock
MIMO MultipleInputMultipleOutput
MMU MemoryManagementUnit
MP ManagementPlane
MPF MediumPriorityFronthaul
MPLS MultiProtocolLabelSwitching
MPS MaximumPayloadSize
NAS NonAccessStratum
NEF NetworkExposureFunction
NF NoiseFigure
NFV NetworkFunctionVirtualization
NFVI NetworkFunctionVirtualizationInfrastructure
NIC NetworkInterfaceCard
NPF NetworkProcessorForum
NPU NetworkProcessorUnit
NR NewRadio
NRF NFRepositoryFunction
NSÀ NonStandalone
NSSF NetworkSliceSelectionFunction
NTP NetworkTimeProtocol
OAM OperationandMaintenance
OBSAI OpenBaseStationArchitectureInitiative
OBW OccupiedBandwidth
OFDM OrthogonalFrequencyDivisionMultiplexing
OFDMA OrthogonalFrequencyDivisionMultipleAccess
ONF OpenNetworkingFoundation
OSS OperationsSupportSystems
PA PowerAmplifier
PAPR PeaktoAveragePowerRatio
PCCH PagingControlChannel
PCF PolicyControlFunction
PDCCH PhysicalDownlinkControlChannel
PDCP PacketDataConvergenceProtocol
PDSCH PhysicalDownlinkSharedChannel
PH PowerHeadroom
PI PreemptionIndicator
PLL PhaseLockedLoop
PoE PoweroverEthernet
PRACH PhysicalRandomAccessChannel
PRB PhysicalResourceBlock
PSS PrimarySynchronizationSignal
PTP PrecisionTimeProtocol
PUCCH PhysicalUplinkControlChannel
PUSCH PhysicalUplinkSharedChannel
QAM QuadratureAmplitudeModulation
QFI QoSFlowId
QoS QualityofService
QPSK QuadraturePhaseShiftKeying
RACH RandomAccessChannel
RAN RadioAccessNetwork
RANAP RadioAccessNetworkApplicationPart
RAT RadioAccessTechnology
RB ResourceBlock
RE ResourceElement
RED RandomEarlyDiscard
RIBS RadioInterfaceBasedSynchronization
RIC RANIntelligentController
RF RadioFrequency
RFC RequestForComments
RLC RadioLinkControl
RMS RootMeanSquare
RNTI RadioNetworkTemporaryIdentifier
RoHC RobustHeaderCompression
RQA ReflectiveQoSAttribute
RRC RadioResourceControl
ROM ReadOnlyMemory
RRM RadioResourceManagement
RSU RoadsideUnit
RT Realtime
RTOS RealtimeOperatingSystem
rtPS real-timePollingService
RTT RoundTripTime
RU RadioUnit
SA Standalone
SAS SpectrumAllocationSystem
SCS SubcarrierSpacing
SDAP ServiceDataAdaptationProtocol
SDN SoftwareDefinedNetworking
SDoC SupplierDeclarationofConformity
SDU ServiceDataUnit
SeNB SlaveeNB
SFN SingleFrequencyNetwork
SIB SecondaryInformationBlock
SIM SubscribedIdentityModule
SIMD SingleInstructionMultipleData
SLA ServiceLevelAgreement
SMF SessionManagementFunction
SN SequenceNumber
SNR SignaltoNoiseRatio
SPS SemiPersistentScheduling
SRB SignalingRadioBearer
SRS SoundingReferenceSignal
SSB SynchronizationSignalBlock
SSE StreamingSignalingExtensions
SSS SecondarySynchronizationSignal
SUL SupplementaryUplink
SW Software
T-BC TelecomBoundaryClock
T-GM TelecomGrandMaster
T-TSC TelecomTimeSlaveClock
TAI InternationalAtomicTime
TB TransportBlock
TCM ThreeColorMarker
TCP TransmissionControlProtocol
TCXO TemperatureControlledOscillator
TIP TelecomInfrastructureProject
TDD TimeDivisionDuplex
TDM TimeDivisionMultiplexing
TEID TunnelEndpointIdentifier
TM TransparentMode
ToR TopofRack
TPC TransmitPowerControl
TRP TransmitReceivePoint
TSN TimeSensitiveNetworking
TTI TransmitTimeInterval
UAV UnmannedArialVehicle
UCI UplinkControlInformation
UE UserEquipment
UL Uplink
ULSCH UplinkSharedChannel
UM UnacknowledgedMode
UMA UnlicensedMobileAccess
UMTS UniversalMobileTelecommunicationSystem
UP UserPlane
UPF UserPlaneFunction
URLLC UltraReliableLowLatencyCommunication
UTC CoordinatedUniversalTime
V2I VehicletoInfrastructure
V2P VehicletoPedestrian
V2X VehicletoAnything
VCXO VoltageControlledOscillator
WCDMA WidebandCodeDivisionMultipleAccess
WG WorkingGroup
WiFi WirelessFidelity
WiMAX WirelessInteroperabilityforMicrowaveAccess
WRED WeightedRandomEarlyDiscard
Openradioaccessnetwork overview
ThischapterprovidesanintroductiontotheOpenRadioAccessNetworks(O-RAN)(withadash!) Allianceanditsgoalsandmaindeliveries.Wethendiscussrelatedstandardsbodiesaswellas5G spectralaspectsandashorthistoryof3GPPstandardsandtheirimplementationintermsofsystemsarchitecture.NotethatalthoughO-RANstandardscoverbothLong-TermEvolution(LTE) and5G/NRnetworks,weareusing5Gterminologythroughoutforsimplicityandeaseofreading.
TheOpenRadioAccessNetworksAlliance
FoundingmembersoftheO-RANAllianceareAT&T,ChinaMobile,DeutscheTelekomAG, NTTDOCOMOInc.andOrangebutbynowmembershiphasincreasedafterincludingthe
“Who’sWho” inthewirelessindustry.TheO-RANpublicwebsitecanbefoundatRef1
O-RANisdefinedfromtheonsettobe operator-driven ratherthansystemvendor-driven,to ensurethattheO-RANgoals(seenext)arenotinterferedwith.
ThestatedtargetofO-RANistobreaktheclosednatureofcurrentradioaccessnetwork (RAN)implementations.O-RANexplicitlyaimsspecificallyat3GPPnetworks,asopposedto 802.11(Wi-Fi)andotherwirelessstandards.Byopeningthe3GPPimplementation,O-RAN meanstodecouplehardwareandsoftwareimplementationsallowingvendors(hardware,software,andsystems)tofocusonprovidingcomponentsratherthancompletesolution.Aimisto followwhathappenedinwirelinesoftware-definednetworking(SDN)(thinkofswitches,routers, andfirewalls),whichhavemovedfromproprietary,hardware-centricimplementationstoa software-centricimplementationthatexecutesongeneral-purpose,Arm,RISC-V,orx86 hardware.
O-RANisorganizedintoworkinggroupsthatownspecifichardware,software,andsystemcomponents.Theseworkinggroupsareshownin Fig.1 1.
Notethatthecontributionsoftheseworkinggroupsare “live” andcontinuouslyupdated. Descriptionsandownershipaswearedescribingbelowarethereforeperdefinitioninflux. CheckouttheO-RANmemberwebsite(wherepartsofthesedescriptionsaretakenfrom)for thelatestupdates.
WorkingGroup1:UseCasesandOverallArchitectureWorkgroup WG1focusesonusecasesandsystem-levelrequirementsaswellasorganizingproofof conceptstoshowcaseO-RANproductstothewidermarket.Thisworkinggroupisoperatorled(AT&T,CMCC).
WorkingGroup2:Non-Real-TimeRICandA1InterfaceWorkgroup
1 OpenRadioAccessNetwork(O-RAN)SystemsArchitectureandDesign.DOI: https://doi.org/10.1016/B978-0-323-91923-4.00013-6 © 2022ElsevierInc.Allrightsreserved.
2OpenRadioAccessNetwork(O-RAN)SystemsArchitectureandDesign
WG1: Overall use-cases and architecture
Orchestra on & Automa on (eg ONAP): MANO, NMS
RAN Intelligent Controller (RIC) near-RT
Design Inventory Policy Configura on RAN Intelligent control (RIC) on-RT Applica ons Layer
3rd party APP Radio Connect Mgmt Mobility Mgmt QoS Mgmt Interference Mgmt Trained Model Radio-Network Informa on Base
between near-RT and O-CU / O-DU
NFVI Pla orms: Virtualiza on Layer and COTS Pla orm F1: between near-RT and O-CU / O-DU
O-DU: RLC/MAC/PHY-high Open Fronthaul Interface
O-RU: PHY-low/RF
FIGURE1–1 O-RANWorkingGroups. O-RAN,OpenRadioAccessNetworks.
WG2ownsthedefinitionofthenon-Real-Time(RT)RANIntelligentController(RIC)and theA1interface.Thenon-RTRICcontrolsradioresourcemanagement(RRM),higherlayer procedureoptimization,andRANpolicyoptimization,includingArtificialIntelligence(AI)/ MachineLearningmodelapplication.Communicationbetweenthenear-RTRICandthenonRTRICisdefinedbytheA1interface functionally,thisinterfacecarriespolicy-basedguidance ofnear-RTRICfunctions/usecasesandappropriatefeedback/inputdatainthereturnpath. Atitslowestlevel,non-RTRICconvertssystem goals(RANintent)andobservedparametersand counterstopoliciesthatguidetheRTRICtowardfulfillingthesystemgoals.Deliverablesinclude:
• A1interfacespecification
WorkingGroup3:Near-Real-timeRICandE2InterfaceWorkgroup
WG3ownsthenear-RTRICarchitectureandfunctionalities.Deliverablesinclude:
• E2interfacespecification.NotethattheE2interfaceis3GPP-defined.WG3providesa frameworkwithadefinedsubsetof3GPPmessages.
WorkingGroup4:OpenFronthaulInterfacesWorkgroup
WG4ownsthedefinitionoffronthaulinterfaces.Deliverablesinclude:
• Managementplane(MP)specification.ANETCONF/YANGbasedM-Planeisusedfor supportingthemanagementfeaturesincluding “start-up” installation,software management,configurationmanagement,performancemanagement,faultmanagement, andfilemanagementtowardtheO-RU.
• Control,userandsynchronizationplane(CP,UP,SP)specification.Thisspecifiesthe controlplane,userplane,andsynchronizationplaneprotocolsusedtolinkthe distributedunit(DU)withradiounit(RU)assumingafunctionalsplit7,coveringboth LTEand5G/NR.Notethatthecontrolplanerefersspecificallytoreal-timecontrol betweenO-DUandO-RUandnotthe3GPPControlPlane.
• Fronthaulinteroperabilitytestspecification.Thisspecifiestestscenariostobe implementedtoconfirminteroperabilitybetweenDUandRUimplementationsof differentvendors.ThisspecificationincludesseveralstandardizedInteroperabilityand Test(IoT)profiles.ThespecificationcoversM-PlaneandCU-Planes,includingtopics suchasbeamforming,compression,andlatency.
WorkingGroup5:OpenF1/W1/E1/X2/XnInterfaceWorkgroup
WG5ownsthedefinitionofmid/backhaulinterfaces,likehowWG4ownsthefronthaul interface.Deliverablesinclude:
• O1interfacespecification.TheO1interfacelinkstheDUwithcentralunit(CU)and ServiceManagementandOrchestration.Thisinterfacedefinesinitialization, configuration,andmanagementoftheDU,including “start-up” installation,software management,configurationmanagement,performancemanagement,faultmanagement, andfilemanagementtowardtheO-RU.LiketheWG4MPspecificationforRU,aYANG moduleisusedforDUdefinition.
• Mid/backhaulIoTspecification.
WorkingGroup6:CloudificationandOrchestrationWorkgroup
WG6addressesCloudificationandOrchest rationinO-RAN.WG6identifiesusecases thatdemonstratethebenefitsfromhardware/softwaredecoupling(cloudification), includingRIC,DU,CU,andRU.Italsodefin esdeploymentscenarios,requirements, andreferencedesignsforthecloudplat form,includingtheNetworkFunction VirtualizationInfrastructure(infrastructur e),VirtualizedInfrastructureManager(VIM) forcontainer/VMorchestration,andAcceleratorAbstractionLayers(AAL).
AcceleratorAbstractionLayersallowthedefinitionofhardwareacceleratedcomponents (e.g.,fronthaul,timing,GPRSTunnelingProtocol(GTP)/transport,high-PHY)withacommonsoftwareinterfacetothe(virtualized)hostsoftware.
