附錄4****大學本科畢業設計（論文）外文翻譯課題名稱：年級專業：***級通信工程3班學生姓名：指導教師：ReviewofUMTS1.1UMTSNetworkArchitectureTheEuropean/Japanese3GstandardisreferredtoasUMTS.UMTSisoneofanumberofstandardsratifiedbytheITU-TundertheumbrellaofIMT-2000.Itiscurrentlythedominantstandard,withtheUSCDMA2000standardgainingground,particularlywithoperatorsthathavedeployedcdmaOneastheir2Gtechnology.Attimeofwriting,Japanisthemostadvancedintermsof3Gnetworkdeployment.Thethreeincumbentoperatorstherehaveimplementedthreedifferenttechnologies:J-PhoneisusingUMTS,KDDIhasaCDMA2000network,andthelargestoperatorNTTDoCoMoisusingasystembrandedasFOMA(FreedomofMultimediaAccess).FOMAisbasedontheoriginalUMTSproposal,priortoitsharmonizationandstandardization.TheUMTSstandardisspecifiedasamigrationfromthesecondgenerationGSMstandardtoUMTSviatheGeneralPacketRadioSystem(GPRS)andEnhancedDataforGlobalEvolution(EDGE),asshowninFigure.ThisisasoundrationalesinceasofApril2003,therewereover847MillionGSMsubscribersworldwide1,accountingfor68%oftheglobalcellularsubscriberfigures.TheemphasisisonkeepingasmuchoftheGSMnetworkaspossibletooperatewiththenewsystem.WearenowwellontheroadtowardsThirdGeneration(3G),wherethenetworkwillsupportalltraffictypes:voice,videoanddata,andweshouldseeaneventualexplosionintheservicesavailableonthemobiledevice.ThedrivingtechnologyforthisistheIPprotocol.Manycellularoperatorsarenowatapositionreferredtoas2.5G,withthedeploymentofGPRS,whichintroducesanIPbackboneintothemobilecorenetwork.Thediagrambelow,Figure2,showsanoverviewofthekeycomponentsinaGPRSnetwork,andhowitfitsintotheexistingGSMinfrastructure.TheinterfacebetweentheSGSNandGGSNisknownastheGninterfaceandusestheGPRStunnelingprotocol(GTP,discussedlater).Theprimaryreasonfortheintroductionofthisinfrastructureistoofferconnectionstoexternalpacketnetworks,suchastheInternetoracorporateIntranet.ThisbringstheIPprotocolintothenetworkasatransportbetweentheSGSNandGGSN.Thisallowsdataservicessuchasemailorwebbrowsingonthemobiledevice,withusersbeingchargedbasedonvolumeofdataratherthantimeconnected.Thedominantstandardfordeliveryof3GnetworksandservicesistheUniversalMobileTelecommunicationsSystem,orUMTS.ThefirstdeploymentofUMTSistheRelease’99architecture,shownbelowinFigure3.Inthisnetwork,themajorchangeisintheradioaccessnetwork(RAN)withtheintroductionofCDMAtechnologyfortheairinterface,andATMasatransportinthetransmissionpart.Thesechangeshavebeenintroducedprincipallytosupportthetransportofvoice,videoanddataservicesonthesamenetwork.Thecorenetworkremainsrelativelyunchanged,withprimarilysoftwareupgrades.However,theIPprotocolpushesfurtherintothenetworkwiththeRNCnowcommunicatingwiththe3GSGSNusingIP.ThenextevolutionstepistheRelease4architecture,Figure4.Here,theGSMcoreisreplacedwithanIPnetworkinfrastructurebasedaroundVoiceoverIPtechnology.TheMSCevolvesintotwoseparatecomponents:aMediaGateway(MGW)andanMSCServer(MSS).Thisessentiallybreaksaparttherolesofconnectionandconnectioncontrol.AnMSScanhandlemultipleMGWs,makingthenetworkmorescaleable.SincetherearenowanumberofIPcloudsinthe3Gnetwork,itmakessensetomergethesetogetherintooneIPorIP/ATMbackbone(itislikelybothoptionswillbeavailabletooperators.)ThisextendsIPrightacrossthewholenetwork,allthewaytotheBTS.ThisisreferredtoastheAll-IPnetwork,ortheRelease5architecture,asshowninFigure5.TheHLR/VLR/EIRaregeneralisedandreferredtoastheHLRSubsystem(HSS).Nowthelastremnantsoftraditionaltelecommunicationsswitchingareremoved,leavinganetworkoperatingcompletelyontheIPprotocol,andgeneralisedforthetransportofmanyservicetypes.Real-timeservicesaresupportedthroughtheintroductionofanewnetworkdomain,theIPMultimediaSubsystem(IMS).Currentlythe3GPPareworkingonRelease6,whichpurportstocoverallaspectsnotaddressedinfrozenreleases.SomecallUMTSRelease64GanditincludessuchissuesasinterworkingofhotspotradioaccesstechnologiessuchaswirelessLAN1.2UMTSFDDandTDDLikeanyCDMAsystem,UMTSneedsawidefrequencybandinwhichtooperatetoeffectivelyspreadsignals.Thedefiningcharacteristicofthesystemisthechiprate,whereachipisthewidthofonesymboloftheCDMAcode.UMTSusesachiprateof3.84Mchips/sandthisconvertstoarequiredspectrumcarrierof5MHzwide.Sincethisiswiderthanthe1.25MHzneededfortheexistingcdmaOnesystem,theUMTSairinterfaceistermed‘wideband’CDMA.ThereareactuallytworadiotechnologiesundertheUMTSumbrella:UMTSFDDandTDD.FDDstandsforFrequencyDivisionDuplex,andlikeGSM,separatestrafficintheuplinkanddownlinkbyplacingthematdifferentfrequencychannels.Thereforeanoperatormusthaveapairoffrequenciesallocatedtoallowthemtorunanetwork,hencetheterm‘pairedspectrum’.TDDorTimeDivisionDuplexrequiresonlyonefrequencychannel,anduplinkanddownlinktrafficareseparatedbysendingthematdifferenttimes.TheITU-Tspectrumusage,asshowninFigure6,forFDDis1920-980MHzforuplinktraffic,and2110-2170MHzfordownlink.Theminimumallocationanoperatorneedsistwopaired5MHzchannels,oneforuplinkandonefordownlink,ataseparationof190MHz.However,toprovidecomprehensivecoverageandservices,itisrecommendedthatanoperatorbegiventhreechannels.Consideringthespectrumallocation,thereare12pairedchannelsavailable,andmanycountrieshavenowcompletedthelicencingprocessforthisspectrum,allocatingbetweentwoandfourchannelsperlicence.Thishastendedtoworkoutacostlyprocessforoperators,sincetheregulatoryauthoritiesinsomecountries,notablyinEurope,haveauctionedtheselicencestothehighestbidder.Thishasresultedinspectrumfeesashighastensofbillionsofdollarsinsomecountries.TheTimeDivisionDuplex(TDD)system,whichneedsonlyone5MHzbandinwhichtooperate,oftenreferredtoasunpairedspectrum.ThedifferencesbetweenUMTSFDDandTDDareonlyevidentatthelowerlayers,particularlyontheradiointerface.Athigherlayers,thebulkoftheoperationofthetwosystemsisthesame.Asthenamesuggests,theTDDsystemseparatesuplinkanddownlinktrafficbyplacingthemindifferenttimeslots.Aswillbeseenlater,UMTSusesa10msframestructurewhichisdividedinto15equaltimeslots.TDDcanallocatethesetobeeitheruplinkordownlink,withoneormorebreakpointsbetweenthetwoinaframedefined.Inthisway,itiswellsuitedtopackettraffic,sincethisallowsgreatflexibilityindynamicallydimensioningforasymmetryintrafficflow.TheTDDsystemshouldnotreallybeconsideredasanindependentnetwork,butratherasasupplementforanFDDsystemtoprovidehotspotcoverageathigherdatarates.Itisratherunsuitableforlargescaledeploymentduetointerferencebetweensites,sinceaBTSmaybetryingtodetectaweaksignalfromaUE,whichisblockedoutbyarelativelystrongsignalatthesamefrequencyfromanearbyBTS.TDDisidealforindoorcoverageoversmallareas.SinceFDDisthemainaccesstechnologybeingdevelopedcurrently,theexplanationspresentedherewillfocuspurelyonthissystem.1.3UMTSBearerModelTheproceduresofamobiledeviceconnectingtoaUMTSnetworkcanbesplitintotwoareas:theaccessstratum(AS)andthenon-accessstratum(NAS).Theaccessstratuminvolvesallthelayersandsubsystemsthatoffergeneralservicestothenon-accessstratum.InUMTS,theaccessstratumconsistsofalloftheelementsintheradioaccessnetwork,includingtheunderlyingATMtransportnetwork,andthevariousmechanismssuchasthosetoprovidereliableinformationexchange.Allofthenon-accessstratumfunctionsarethosebetweenthemobiledeviceandthecorenetwork,forexample,mobilitymanagement.Figure7showsthearchitecturemodel.TheASinteractswiththeNASthroughtheuseofserviceaccesspoints(SAPs).UMTSradioaccessnetwork(UTRAN)providesthisseparationofNASandASfunctions,andallowsforASfunctionstobefullycontrolledandimplementedwithintheUTRAN.ThetwomajorUTRANinterfacesaretheUu,whichistheinterfacebetweenthemobiledevice,orUserEquipment(UE)andtheUTRAN,andtheIu,whichistheinterfacebetweentheUTRANandthecorenetwork.Bothoftheseinterfacescanbedividedintocontrolanduserplaneseachwithappropriateprotocolfunctions.ABearerServiceisalinkbetweentwopoints,whichisdefinedbyacertainsetofcharacteristics.InthecaseofUMTS,thebearerserviceisdeliveredusingradioaccessbearers.ARadioaccessbearer(RAB)isdefinedastheservicethattheaccessstratum(i.e.UTRAN)providestothenon-accessstratumfortransferofuserdatabetweentheUserEquipmentandCoreNetwork.ARABcanconsistofanumberofsubflows,whicharedatastreamstothecorenetworkwithintheRABthathavedifferentQoScharacteristics,suchasdifferentreliabilities.AcommonexampleofthisisdifferentclassesofbitswithdifferentbiterrorratescanberealisedasdifferentRABsubflows.RABsubflowsareestablishedandreleasedatthetimetheRABisestablishedandreleased,andaredeliveredtogetheroverthesametransportbearer.ARadioLinkisdefinedasalogicalassociationbetweenasingleUserEquipment(UE)andasingleUTRANaccesspoint,suchasanRNC.Itisphysicallycomprisedofoneormoreradiobearersandshouldnotbeconfusedwithradioaccessbearer.LookingwithintheUTRAN,thegeneralarchitecturemodelisasshowninFigure8below.NowshownaretheNodeBorBaseStation(BTS)andRadioNetworkController(RNC)components,andtheirrespectiveinternalinterfaces.TheUTRANissubdividedintoblocksreferredtoasRadioNetworkSubsystems(RNS),whereeachRNSconsistsofonecontrollingRNC(CRNC)andalltheBTSsunderitscontrol.UniquetoUMTSistheinterfacebetweenRNSs,theIurinterface,whichplaysakeyroleinhandoverprocedures.TheinterfacebetweentheBTSandRNCistheIubinterface.Allthe‘I’interfaces:Iu,IurandIub,currently3useATMasatransportlayer.InthecontextofATM,theBTSisseenasahostaccessinganATMnetwork,withinwhichtheRNCisanATMswitch.Therefore,theIubisaUNIinterface,whereastheIuandIurinterfacesareconsideredtobeNNI,asillustratedinFigure9.ThisdistinctionisbecausetheBTStoRNClinkisapoint-to-pointconnectioninthataBTSorRNCwillonlycommunicatewiththeRNCorBTSdirectlyconnectedtoit,andwillnotrequirecommunicationbeyondthatelementtoanothernetworkelement.Foreachuserconnectiontothecorenetwork,thereisonlyoneRNC,whichmaintainsthelinkbetweentheUEandcorenetworkdomain,ashighlightedinFigure10.ThisRNCisreferredtoastheservingRNCorSRNC.ThatSRNCplustheBTSsunderitscontrolisthenreferredtoastheSRNS.ThisisalogicaldefinitionwithreferencetothatUEonly.InanRNS,theRNCthatcontrolsaBTSisknownasthecontrollingRNCorCRNC.ThisiswithreferencetotheBTS,cellsunderitscontrolandallthecommonandsharedchannelswithin.AstheUEmoves,itmayperformasoftorhardhandovertoanothercell.Inthecaseofasofthandover,theSRNCwillactivatethenewconnectiontothenewBTS.ShouldthenewBTSbeunderthecontrolofanotherRNC,theSRNCwillalsoalertthisnewRNCtoactivateaconnectionalongtheIurinterface.TheUEnowhastwolinks,onedirectlytotheSRNC,andthesecond,throughthenewRNCalongtheIurinterface.Inthiscase,thisnewRNCislogicallyreferredtoasadriftRNCorDRNC,seeFigure10.ItisnotinvolvedinanyprocessingofthecallandmerelyrelaysittotheSRNCforconnectiontothecore.Insummary,SRNCandDRNCareusuallyassociatedwiththeUEandtheCRNCisassociatedwiththeBTS.SincethesearelogicalfunctionsitisnormalpracticethatasingleRNCiscapableofdealingwithallthesefunctions.AsituationmayarisewhereaUEisconnectedtoaBTSforwhichtheSRNCisnottheCRNCforthatBTS.Inthatsituation,thenetworkmayinvoketheServingRNCRelocationproceduretomovethecorenetworkconnection.ThisprocessisdescribedinSection3.通用移動通信系統的回顧1.1UMTS網絡架構歐洲/日本的3G標準，被稱為UMTS。UMTS是一個在IMT-2000保護傘下的ITU-T批準的許多標準之一。隨著美國的CDMA2000標準的發展，它是目前占主導地位的標準，特別是運營商將cdmaOne部署為他們的2G技術。在寫這本書時，日本是在3G網絡部署方面最先進的。三名現任運營商已經實施了三個不同的技術：J-PHONE使用UMTS，KDDI擁有CDMA2000網絡，最大的運營商NTTDoCoMo正在使用品牌的FOMA（自由多媒體接入）系統。FOMA是基于原來的UMTS協議，而且更加的協調和標準化。UMTS標準被定義為一個通過通用分組無線系統（GPRS）和全球演進的增強數據技術（EDGE）從第二代GSM標準到UNTS的遷移。這是一個廣泛應用的基本原理，因為自2003年4月起，全球有超過847萬GSM用戶，占全球的移動用戶數字的68％。重點是在保持盡可能多的GSM網絡與新系統的操作。我們現在在第三代(3G)的發展道路上，其中網絡將支持所有類型的流量：語音，視頻和數據，我們應該看到一個最終的爆炸在移動設備上的可用服務。此驅動技術是IP協議。現在，許多移動運營商在簡稱為2.5G的位置，伴隨GPRS的部署，即將IP骨干網引入到移動核心網。SGSN和GGSN之間的接口被稱為Gn接口和使用GPRS隧道協議（GTP的，稍后討論）。引進這種基礎設施的首要原因是提供連接到外部分組網絡如，Internet或企業Intranet。這使IP協議作為SGSN和GGSN之間的運輸工具應用到網絡。這使得數據服務，如移動設備上的電子郵件或瀏覽網頁，用戶被起訴基于數據流量，而不是時間連接基礎上的數據量。3G網絡和服務交付的主要標準是通用移動通信系統，或UMTS。首次部署的UMTS是發行'99架構。在這個網絡中，主要的變化是在無線接入網絡（RAN的）CDMA空中接口技術的引進，和在傳輸部分異步傳輸模式作為一種傳輸方式。這些變化已經引入，主要是為了支持在同一網絡上的語音，視頻和數據服務的運輸。核心網絡保持相對不變，主要是軟件升級。然而，隨著目前無線網絡控制器使用IP與3G的GPRS業務支持節點進行通信，IP協議進一步應用到網絡。未來的進化步驟是第4版架構。在這里，GSM的核心被以語音IP技術為基礎的IP網絡基礎設施取代。海安的發展分為兩個獨立部分：媒體網關（MGW）和MSC服務器（MSS）的。這基本上是打破外連接的作用和連接控制。一個MSS可以處理多個MGW，使網絡更具有擴展性。因為現在有一些在3G網絡的IP云，合并這些到一個IP或IP/ATM骨干網是很有意義的（它很可能會提供兩種選擇運營商）。這使IP權利拓展到整個網絡，一直到BTS(基站收發信臺)。這被稱為全IP網絡，或推出五架構，如圖五所示。在HLR/VLR/VLR/EIR被推廣和稱為HLR的子系統（HSS）。現在傳統的電信交換的最后殘余被刪除，留下完全基于IP協議的網絡運營，并推廣了許多服務類型的運輸。實時服務通過引入一個新的網絡域名得到支持，即IP多媒體子系統（IMS）。目前3GPP作用于第6版，意在包含冷凍版本沒有涵蓋所有方面。有些人稱UMTS第6版為4G和它包括熱點無線電接入技術，如無線局域網互聯互通的問題。1.2UMTS的FDD和TDD像任何CDMA系統，UMTS需要一個寬的頻帶，在這個頻帶上有效地傳播信號。該系統的特點是芯片的速度，芯片是一個符號的CDMA代碼的寬度。UMTS使用的芯片速率為3.84Mchips/秒，這轉換到所需的頻譜載波寬度為5MHz。由于這比現有的cdmaOne系統所需的1.25MHz帶寬要寬，UNTS空中接口被稱為“寬帶”CDMA.實際上在UMTS下有兩個無線電技術：UMTS軟盤驅動器和時分雙工。FDD代表頻分雙工，如GSM，通過把它們放置在不同的頻率信道分離為交通上行和下行。因此，一個運營商必須有一對頻率分配，使他們能夠運行網絡，即術語成對頻譜。TDD或時分雙工只需要一個頻率通道，上行和下行流量是在不同的時間分開發送。ITU-T的頻譜使用。對于FDD是1920-1980MHz的為上行流量，2110-2170MHz為下行的。運營商需要的最小分配是兩個成對5MHz的信道，一個用于上行，一個用于下行的，兩者相分離190MHz。然而，為了給客戶提供全面的覆蓋和服務，建議給予每個運營商三個信道。考慮到頻譜分配，有12對可用的渠道，現在許多國家都完成了這個頻譜的許可過程，每個許可證配置兩個到四個信道。這趨向給運營商造成一個昂貴的花費，因為一些國家的監管部門，特別是在歐洲，已經將這些許可證拍賣給出價最高的人。這就造成了頻譜費用在一些國家高達數十億美元。時分雙工（TDD）系統，只需要一個5MHz的帶寬在其中操作，通常被稱為非成對頻譜。UMTSFDD和TDD之間的差異只有在較低層明顯，特別是在無線接口。在更高的層次，兩個系統的運作大部分是相同的。正如它的名字表明，TDD系統通過把它們放置在不同的時間空擋分為上行流量和下行流量。正如我們以后可以看到的，UMTS使用一個分為15個相等的時隙的10ms幀結構。時分雙工可以分配這些為上行或下行，在一個確定的幀結構中這兩者間可以有一個或多個斷點。以這種方式，這是非常適合數據包通信的，因為這對于不對稱的通信流的動態標注可以有極大的靈活性。TDD系統真的不應該被視為一個獨立的網絡，而是作為一個FDD系統的補充，提供更高的數據傳輸率的熱點覆蓋。由于站點之間的干擾，它相當不合適用作大規模部署，因為一個基站可以嘗試從UE檢測微弱信號，這被來自鄰近基站的相同頻率的相對較強的信號阻止了。時分雙工對于小面積的室內覆蓋是理想的。由于FDD是目前正在發展的主要的接入技術，這里介紹的解釋將完全專注于這個系統。1.3UMTS承載模型移動設備連接到UMTS網絡的程序可以分成兩領域：接入層（AS）和非接入層（NAS）。接入層涉及所有提供普遍服務的非接入層和子系統階層。在UMTS接入層包括無線接入的所有元素網絡，包括潛在的ATM傳輸網絡，各種機制提供可靠的信息交換等。所有的非接入層功能都在移動設備和核心網絡之間，例如，移動性管理。圖7顯示了結構模型。AS通過使用服務接入點（SAPS）與NAS交互。UMTS無線接入網（UTRAN）提供NAS和AS功能的分離，并允許AS功能在UTRAN中被完全控制和實施。兩大UTRAN的接口是UU，這是移動設備之間的接口，或者用戶設備（UE）和UTRAN之間，Iu，這是UT