外文翻譯--空白頻段標(biāo)志著無線界.docVIP

/WhitespacesmarkedoffaswirelessarenaPosted:16Oct2008Whenthelong-awaitedDTVswitchoverintheUnitedStatesoccursnextFebruary,broadcasterswillrelinquishtheanalogchannelssomehaveheldformorethanhalfacentury.Consideringthepricesmobileoperatorspaidforbeachfrontspectrumabove700MHzearlierthisyear,theseunlicensedVHF/UHFchannelsknownaswhitespacesandscatteredthroughoutthe54MHzto698MHzregionoftheRFspectrumwouldeasilyhavepulledinbillionshadtheybeenauctioned.Buttheywerentandarangewarisragingoverhowtheyshouldbeused.Thefirstsquattersinthenewlyunlicensedchannelswilllikelybeahandfuloftechgiants,includingGoogle,Hewlett-Packard,MicrosoftandMotorola,whichhavejoinedwithpublic-interestgroupsandmediacompaniestocreatetheWirelessInnovationAlliance(WIA).SeveralRFcompanieswithlinkstoWIAmembersaretestingprototypeproductsknownaswhite-spacesdevices(WSDs)withtheU.S.FederalCommunicationsCommission(FCC).SuperiorUHFpropagationTransmissionsfromtheseWSDswouldenjoyUHFpropagationcharacteristicsfarsuperiortothoseofthenowovercrowded2.4GHzband.ApplicationsrangefromadatanetworkthatGooglesLarryPagehasdescribedasWi-Fionsteroidstoallsortsofvideo,tonetworksofhumblehouseholdobjectslikewashingmachines,toastersandlightbulbs,allcommunicatingwithoneanother.ThebravenewwirelessworldenvisionedbytheWIAcouldpossiblydisrupttheairwaveswithinterferenceandundoubtedlywillupsetthebroadcastersVHF/UHFmonopoly.Thebroadcastersarelivid,describingtheplanasunworkable.Andalthoughneithersideissayingso,itisnotdifficulttotranslatebroadbandintovideoandunlicensedintodollars.TheFCChasjustconcludeditsfieldtestingofWSDsubmittedbyMotorola,Philips,Adaptrum,SharedSpectrum,andSingaporesInstituteforInfocommResearch.Thetestresultswillalmostcertainlystartanotherroundofvituperationbetweenthetechsandthebroadcasters.Thereisquiteabitofwhitespaceoutthere,particularlyinruralareasoftheU.S.,accordingtotheNewFrontiersFoundation,amemberofWIA.Butthecontestedturfisinlargemediamarketswherethebroadcastersrakeinmostoftheirprofits.NewFrontiers,whichbelievesthesociallyproactiveuseofwhitespacescanhelpclosethedigitaldivide,hasestimatedthepercentageofunusedspectrumvariesfrom18percentinNewYorktomorethan60percentinlessdenselypopulatedareas,suchasWichita,Kansas.Thesefiguresarecontestedbythebroadcastlobby,ledbyMaximumServiceTV(MSTV),whichdescribesitselfastheengineeringarmoftheNationalAssociationofBroadcasters.DavidL.Donovan,presidentofMSTV,arguesthatyoucantjustadduptheDTVchannelsthatarenotlicensedinageographicarea,becausehigh-powerTVsignalscantravelmanymilesbeyondtheirlicensedregion.Moreimportant,hesaid,isthepresenceoflow-powerdeviceslicensedtooperateintheVHF/UHFbands.WirelessmicrophonessuchasthoseusedbysportscasterswhointerviewcoachesandplayersonthesidelinesofsportingeventscanbelicensedtooperatelegallyintheVHF/UHFbands(althoughmanymoreoperateunlicensed).BecausewirelessmicrophonesaremobileandtransmitatmuchlowerpowerthanDTVstations,theyrepresentatougherinterferenceproblemforWSDs.WIAisnottobedeterred.NotingthatmaximumWSDpowertransmissionhasbeenlimitedto100mW,WIAconsultantEdmundThomasisconfidenttheinterferenceproblemcanbesolvedbydeployingtherightsetoftechnologies.Atfirstglance,mostRFengineersmightthinkitundulycautioustofearthatlow-power(below100mW)useofpartofanunoccupied6MHzchannelcouldcauseproblemsforDTV,evenwiththelongerrangeofUHFsignals.RFengineershavebeensolvinginterferenceproblemsforyears,notablytheWi-Fi/Bluetoothcontentioninthe2.4GHzband.ButtheWIAhassetitscounterinterferencebarhigh.Twotechnologiesandpossiblyathirdwouldbeemployed:globalpositioningsystems,cognitiveradioandbeacons.Toguardagainstinterferencewithwirelessmikes,someWIAprototypesincludebeacontechnology.Whenabroadcastersetsupatasportingevent,forexample,itstechnicalteamwilldeployabeaconthatwillbroadcastatapowerthewhite-spacesdevicescaneasilysense.IncumbentsintheVHF/UHFspace,whichincludebroadcastersandwireless-microphoneinterestsledbyU.S.manufacturerShureInc.,havelaunchedaspiritedverbalattackonWSDs.InfectionanalogyMSTVandagroupofstationsaskedtheFCCwhyitwouldconsiderallowingmillionsandmillionsoftheseinterference-causingdevices,likegerms,tospreadthroughoutAmericawiththeabilitytoattacktheTVreceiversinpeopleshomes,apartments,hotelrooms,hospitalrooms,dormitories,etc.,withnowayfortheowneroftheTVset(thevictim)todeterminewhowascausingtheillnesstohisorherTVset?Thatsortofrhetoricmightnotimpressengineers,butithasinducednofewerthan70membersofCongresstosignastatementexpressingdeepconcernabouttheuseofwhitespacesforpersonalwirelessdevices.Itsnotthatthereisntcauseforconcern.Themostoftennotedtechnologytrapistheso-calledhidden-nodeproblem.Essentially,itisquitepossibleforaWSDtobeinapositionwhereitcannotsenseaDTVsignalwhileanearbyTVinanadjacentapartment,forexampleisreceivingthesignal.Thisismostlikelyinareasdensewithlargeconcreteandsteelstructures.Awireless-technologydeploymentwithaslargeamarketandpotentialpublicimpactasWSDswouldtypicallyattractalotofattentionfromtheIEEE.Inthepoliticalwrangleoverwhitespaces,however,itseemsasthoughnothingistypical.ExcludingmobileTheIEEEdoes,infact,haveaworkinggroupIEEEP802.22taskedwithdevelopingadetailedradiointerfacespecificationforacognitiveradiothatwouldshareairwaveswithTVtransmittersandwirelessmicrophonesintheUHFband.Thespecificationincludescognitive-radiotechniquestoavoidoratleastminimizeharmfulinterference.Atthegroupsverycreation,however,itsscopewaslimitedtofixedwirelessdevices,suchasthoseusedbywirelessInternetserviceproviders.MobiledeviceslikeWSDswerespecificallyexcluded.P802.22chairmanCarlR.StevensonhasnotroubledescribingWSDsandtheplanstodeploythemasill-conceived.IbelievethatwhattheWIAisproposingtodoisarecipefordisaster,saidStevenson,aseasonedRFengineerwithalonganddistinguishedcareerinbothindustryandstandardsgroups.TheUHFspectrumactuallypropagatestoowellforshort-rangedevices.Giventhisperspective,itshouldbenosurprisethatStevensonwasinstrumentalinlimiting802.22spurviewtofixeddevices.AsistypicalatIEEE,hisviewsarewellalignedwiththoseofthecompaniessponsoringhischairmanship.AlthoughmostIEEEchairsareemployeesofcompanieslargeenoughtohandletheexpensesequivalenttoasalary(Intelisagoodexample),someconsultantssupporttheirIEEEworkbyacquiringsponsors.Stevensontookthelatterroute.MSTV,ShureandQualcommallopponentsofWSDssponsorhisIEEEactivities.ThisiswithinIEEEguidelines,andsponsorshipdisclosuresaremadetotheIEEE.Stevensonsaysthereisnoconflictofinterestandthatnoneofhiscorporatesponsorshaveeverpressuredmeinanyway.Thebroadcasters,inparticular,broughtagreatdealofknowledgeandexpertiseinbroadcasttechnologytotheworkinggroup,hesaid.-TheoutcomeofFCCtestingisstilluncertain,butifthecommissionallowsWSDs,thelackofastandardwillprobablylimittheirdeploymenttoahandfulofcompanies.Unlessextraordinarymeasuresaretakentoleveltheplayingfield,thecompaniestestingprototypeswillhaveaverybigjumpontherestoftheRFcommunity.Single-stream11nchipsattackWi-FimainstreamAtherosCommunicationsInc.willtrytodrive802.11nintomainstreamWi-Fimarketswithanewlineofchipsusingastreamlinedversionofthespecification.TheAtherosAlignfamilyusesonlyasingleantennatotarget11gpricepoints.AnalystssaidtheyexpectotherWi-Fichipmakerstofollowsuitwiththeirownsingle-stream11nproducts.However,theyalsocautionedthatthe11nmarketmayfaceconfusionfromtheemergingdiversityofconfigurations.Todaymost802.11nproductsuse2x2MIMO(multipleinput,multipleoutput)antennastodeliverasmuchastentimesthethroughputofolder11gdevices.Howeveratnearlytwicethecost,the11ndevicescommandonlyaboutathirdthemarketshareof11g,despitethefacttheWi-FiAlliancebegancertifyingdraft11nproductsinJune2007.Inthesecondquarterof2008,revenuefordraft11nproductsaccountedfor21percentofthemarketcomparedto64percentfor802.11gand15percentformultimodeb/g/a,accordingtoVictoriaFodale,asenioranalystwithmarketwatcherIn-Stat.WehadOEMscomingtouswithplanstobuild2009-10deviceswithWi-Fi,buttheywantedtouse.11g,saidToddAntes,vicepresidentofmarketingatAtheros.Itwascleartousthenextlargeopportunityfor.11nwastomovelegacy.11gdesignsuptoamoreefficientstandard,headded.Bystrippingoutsupportformultipleradios,Atherosisbettingitcancreateanewclassofhighervolume11ndevicesthathittheestimated$3-5pricingof11gpartsbutdeliverbetterperformance.Theprice/valuepropositionisclear,butthereisthepotentialforconsumerconfusionregardingproductcompatibilitysincethe11nspecificationallowsforone,two,three,orevenfourspatialstreams,saidFodaleofIn-Stat.Indeed,Quantennarecentlybecamethelatestofseveralstartupstodebut11nchipswithaggressiveMIMOconfigurations,aimingatsupportforwholehomeWi-Fiandhighdefinitionvideo.AntessuggestedtheWi-FiAllianceisworkingonasolutiontoletusersmixandmatchdifferentvariantsof11n.The11nstandardismuchricherthana