The-software-radio-architecture(英文)

TheSohareRadioArchitectureAscommunicationstechnologycontinuesitsrapidtransitionfromanalogtodigital,morefunctionsofcontemporaryradiosystemsareimplementedinsoftware,leadingtowardthesoftwareradio.Whatdistinguishessoftwareradioarchitectures?Whatnewcapabilitiesaremoreeconomicallyaccessibleinsoftwareradiosthandigitalradios?Whatarethepitfalls?Andtheprognosis?JoeMitolaJOEMITOLAisaconsultingscientistwithTheMITRECopration.SPWisaregisteredtrade-markoftheAltaGroup.TMS320isaregisteredtrademarkofTexasIustruments,Inc.MatlabisarrzisteredtrademarkofTheMath-WorksInc.SPOXisaregisteredtrademarkofSpectrumMicrosystem.COSSAPisaregisteredtrademarkofSYNOPSIS,Inc.MatcadisaregisteredtrademarkofMathsop,Inc.earepoisedonthethresh-oldofanotherrevolutioninradiosystemsengineering.Throughoutthe‘70sand’80sradiosystemsmigratedfromanalogtodigitalinalmostevevrespectfromsystemcontroltosourceandchan-nelcodingtohardwaretechnology.Andnowthesoftwareradiorevolutionextendsthesehorizonsbyliberatingradio-basedselvicesfromchronicdepen-dencyonhard-wiredcharacteristics,includingfrequencyband,channelbandwidth,andchannelcoding.Thisliberationisaccomplishedthroughacombinationoftechniquesthatincludesmulti-bandantennasandRFconversion;widebandAnalogtoDigital(AID)andDigitaltoAnalog(DIA)conversion(AIDIAconversion);andtheimple-mentationofIF,baseband,andbitstreampro-cessingfunctionsingeneral-purposeprogrammableprocessors.Theresultingsoftware-definedradio(or“softwareradio”)inpartextendstheevolu-tionofprogrammablehardware,increasingflexi-bilityviaincreasedprogrammability.And,inpart,itrepresentsanidealthatmayneverbefullyimplementedbutthatneverthelesssimplifiesandilluminatestradeoffsinradioarchitecturesthatseektobalancestandardscompatibility,technol-ogyinsertion,andthecompellingeconomicsoftoday’shighlycompetitivemarketplaces.RadioArchitectureEvolutionOfthemanypossibledefinitionsofarchitecture,theonethatbestrelatessystems,technologyandeconomicsisbestsuitedtothisdiscussion.Weshallthereforedefine“architecture”asthecomprehen-sive,consistentsetoffunctions,componentsanddesignrulesaccordingtowhichsystemsofinterestmaybeorganized,designed,andconstructed.Aspecificarchitectureentailsapartitioningoffunctionsandcomponentssuchthatfunctionsareassignedtocomponentsandinterfacesamongcom-ponentscorrespondtointerfacesamongfunctions.Whensuchfunctionsandinterfacesaredefinedinformaldesignrulesviaapublicforum,theresult-ingarchitecturesarecalled“open.”Thefulleco-nomicbenefitsofopenarchitecturesrequiretheexistenceofalargecommercialbasewhichsome-timesfailstoemergeinspiteofopenness.Assys-temcomplexityincreases,architecturebecomesmorecriticalbecauseofitspowertoeithersimplifyandfacilitatesystemdevelopment(a“powerful”architecture)ortocomplicatedevelopmentandimpedeprogress(a“weak’architecture).Radioarchitecturesmaybeplottedinthephasespaceofnetworkorganizationversuschanneldatarate,asshowninFig.1.Thesearchitectureshaveevolvedfromearlypoint-to-pointandrelativelychaoticpeernetworks(e.g.,citizensbandandpush-to-talkmobilemilitaryradionetworks)towardmorehierarchicalstructureswithimprovedser-vicequality.Inaddition,channeldataratescontinuetoincreasethroughmultiplexingandspectrumspreading.Inamultiple-hierarchyapplication,asingleradiounit,typicallyamobileterminal,par-ticipatesinmorethanonenetworkhierarchy.Asoftwareradioterminal,forexample,couldoperateinaGSMnetwork,anAMPSnetwork,andafuturesatellitemobilenetwork.Multibandmulti-modemilitaryradiosandfuturePersonalCom-municationsSystems(PCS)thatseamlesslyintegratemultimediaservicesacrosssuchdiverseaccessmodesrepresentthehighendofthatevo-lutionandthefocusofthisdiscussion.Thecom-plexityoffunctions,componentsanddesignrulesofthesearchitecturescontinuestoincreasewitheachgeneration,asshowninTable1.Inparticular,futureseamlessmultimodenetworkswillrequireradioterminalsandbasestationswithagileRFhands,channelaccessmodes,datarates,BitErrorRates(BERs),power,andfunctionali-ty.Softwareradioshaveemergedtoincreasequalityofservicethroughsuchagility.Atthesametime,softwareradioarchitecturessimplifyhard-warecomponenttradeoffsandprovidenewwaysofmanagingthecomplexityofrapidlyemergingstandards.TheCanonicalSoftwareRadioArchitectureThecomponentsofthecanonicalsoftwareradioconsistofapowersupply,anantenna,amulti-bandRFconverter,andasinglechipcontaining26--.0163-6804/95/$04.0019950IEEEIEEECommunicationsMagazineMay1995AnalogEarlydigitalmicrowavei!\AnalogMobileCellular~Radio(MCR)/Spreadspectrum(CDMNFH)~1TDMAMU(Futureseamlessmutttimodemultimedianetworks-.7Transmitandreceive,channelselect,squelch(discreteanalogbaseband)standardmodulations(AM,FM),IPower,antenna,packagingChannelallocations,powerIlmits.~~~Transmitorreceiveprotectedmodes,BERcontrolAnalog+signalingandcontrdAnalog+quadraturemodems+ForwardErrorControl(FEC)Analog+digitalmodems+embeddedcontrolprocessorsCodesynchronization,codeAnalog+earlydigitalmanagement,BERcontrol+de-/spreadingdevices+peernetworkprotocols+embeddedcontrolprocessorsAnalog+earlydigital+analogAnalog+analogMCR+spreadMCR+spreadspectrum+diversityspectrum+multibeamantennas+directivi