畢業(yè)論文外文翻譯Wi-Fi技術(shù)

2012屆本科畢業(yè)設(shè)計中英文翻譯學(xué)生姓名：所在院系：信息工程學(xué)院所學(xué)專業(yè)：信息工程導(dǎo)師姓名：完成時間：2010-05-10Wi-FistandsforWirelessFidelity,alsoknownasthe802.11bstandard.Itsbiggestadvantageisthehightransmissionspeedcanreach11Mbps,anothereffectivelongdistance,atthesametimecompatiblewiththeexistingvarietyof802.11DSSSequipment.AlongwithIntel'slaptopchipset,"Centrino"isrecognizedbymoreandmorepeople,thistechnologyhasbecomeatopicofconcerntoeveryone.However,sincetheendof2005,manymobilephonemanufacturers,especiallytheproductionofsmartphonesbasedbrandWi-Fibegantointroducetheirownproducts.Inshort:Wi-Fiwirelessnetworks.Wi-Fihasbeenwidelyusedinnotebookcomputers,mobilephones,PDAs,digitalcamerasandothermobiledevices.WithWi-Fi,nocablecanbelinkedintothenetwork.Moreandmoredevicesinstalledinthefactory,Wi-Fimodule,butalsomoreandmoreplacestoofferWi-Fisignalcoverage.Inthisway,theWi-Fiformedfromresearchtoequipmentproduction,fromnetworkaccesstonetworkservicesisahugeindustrialchain.In2007,thevalueofthenationalthewlanindustry,includingWi-Fiindustryisexpectedtoexceed100millionU.S.dollars.Forindividualusers,thepopularityofWi-Fi,itwillbealeapforwardinuserexperience.LaptopuserswillbeabletoanyonewithWi-FisignalcoveragefastaccesstotheInternetwithouttheneedtogolookingfornetworkcable,agrowingnumberofairports,hotels,publicplaces,offerWi-Fisignalcoverage.Inatimelymannerwithalaptopcomputertomeetings,donotworrydonothaveenoughnetworkcablejackintheconferenceroom.Athome,youcaneveninanycornerofthecoverageofwirelesssignals,withouthavingtoworryaboutthealignmentofthecableaffecttheoverallindoorappearance.Wi-Fiinhandhelddevicesarewidelyused,andsmartphonesispartofit.DifferentfromtheearlierBluetoothtechnologyusedinmobilephones,Wi-Fihasagreatercoverageandhighertransmissionrates,Wi-Fiphoneshasbecomeafashiontrendofthemobilecommunicationsindustry.Wi-Fibandsintheworldwithoutanytelecomoperatorlicensefreeband,WLANwirelessdevicesprovidesaworldwidecanbeused,thecostisextremelylowandveryhighdatabandwidthwirelessairinterface.UserscanbrowsethewebquicklyintheWi-Ficoveragearea,anytime,anywhereandreceivephonecalls.OtherWLAN-basedbroadbanddataapplicationssuchasstreamingmedia,onlinegamesandotherfunctionsmoreusershouldexpect.WithWi-Ficapability,long-distancecalls(includinginternationallongdistance),browsetheWeb,sendandreceivee-mail,musicdownloads,digitalphototransfer,willnolongerhavetoworryaboutslowandcostlyproblem.Wi-Fifliprangemorewidelyinthecountry,luxuryhotels,luxuryresidential,airportsandcoffeeshopsclassareahasWi-Fiinterface.Whenwewenttothetouristoffice,youcanuseourhandhelddevicesinsuchplacesandenjoysurfingtheweb.AWi-Ficonnectionpointnetworkmembersandstructureofthesite(Station),thenetworkofbasiccomponents.Thebasicserviceunit(BasicservicetheSet,BSS).Networkbasicserviceunit.Themostsimpleunitcanonlybecomposedbythetwosites.Thesitecanbedynamiclink(associate)tothebasicserviceunit.DistributionSystemDistributionSystem(DS).Thedistributionsystemusedtoconnectdifferentbasicserviceunit.Themediadistributionsystemmedium(Medium)logicandthebasicserviceunitiscompletelyseparate,eventhoughtheyphysicallymaybethesamemedia,forexample,thesameradiofrequencyband.Accesspoint(AcessPoint,AP).Accesspointthattheidentityoftheordinarysites,andaccesstothedistributionfunctionofthesystem.ExtendedServiceUnit(ExtendedServiceSetESS).Acombinationofthedistributionsystemandbasicservicesunit.Thiscombinationislogical,notphysical-thebasicserviceunitofmattermaybegeographicallyfarremovedfrom.Distributionsystemcanalsouseavarietyoftechniques.Mark(Portal)isalogicalcomposition.ForwirelessLANandwiredLANorothernetworklink.Herearethreekindsofmedia,thesiteuseswirelessmediadistributionsystemtousethemedia,andotherLANandwirelessLANintegrationtogethermedia.Physically,theymayoverlapeachother.TheIEEE802.11onlyresponsibleforaddressing(Addressing,)onthesiteusesthewirelessmedium.DistributionsystemsandotherLANaddressingarangeofwirelessLAN.TheIEEE802.11nospecificdefinitionofthedistributionsystem,butthedefinitionofthedistributionsystemshouldprovidetheservices(Service).TheentirewirelessLANdefinesninekindsofservice,fivekindsofservicesarepartofthetaskofdistributionsystems,respectively,joins(Association),theendconnection(Diassociation),distribution(Distribution,),integration(Integration),tore-connect.Fourkindsofservicesarethetasksofthesite,respectively,authentication(Authentication),theendoftheauthentication(Deauthentication),privacy(Privacy),MACdatatransmission(theMSDUdelivery).ThemaintechnicaladvantageoftheWi-FiFirstAradiowavecoverage,thecoverageofradiobasedonBluetoothtechnologyisverysmallradiusofonlyabout50feet,orabout15meters.Wi-Firadiusofuptoabout300feet,orabout100meters.AnewtypeofbyVivatocompanyrecentlylaunchedtheswitches,whichproductstocurrentWi-Fiwirelessnetwork300ft,closeto100mcommunicationdistanceexpandedtofourmiles,about6.5km.SecondAlthoughthequalityofwirelesscommunicationstransmittedbytheWi-FitechnologyisnotverygoodperformanceofdatasecuritythanBluetoothworse,thetransmissionqualitytobeimproved,butthetransferspeedisveryfast,youcanreach11Mbps,inlinewiththeneedsofpersonalandsocialinformation.Thirdmanufacturerstoenterthefieldisrelativelylowthreshold.Vendorssetup"hotspots"inairports,railwaystations,coffeeshops,librariesandotherpersonnelintensive,andhigh-speedlineInternetaccesstotheseplaces.Such"hotspots"toemitradiowavescanreachtensofmetersto100metersawayfromtheradiusoftheaccesspoint,aslongastheuserwillsupportwirelessLANnotebookorPDAtogettheregiontohigh-speedInternetaccess.Meansthatmanufacturersdonothaveexpensivenetworkcablingaccess,thussavingalotofcost.Wi-FimethodsoforganizingWi-FiisawirelessnetworkbytheAP(AccessPoint)andWirelessLAN.GenerallysetupawirelessnetworkequippedwithawirelesscardandtheAP,sowillbeabletowirelessmode,withbothwiredarchitecturetosharenetworkresources,erectioncostandcomplexityoftheprogramisfarlowerthanatraditionalwirednetwork.Ifonlyafewcomputers,peer-to-peernetwork,canalsobenottotheAP,onlyrequireeachcomputerisequippedwithawirelesscard.APisgenerallytranslatedas"wirelessaccesspoint",or"bridge".Itismainlyasabridgebetweentraditionalwiredlocalareanetworksandwirelesslocalareanetwork,aPCequippedwithawirelesscardcanbewiredlocalareanetworkorwideareanetworktoshareresourcesthroughtheAP,anditsworkingprincipleisequivalenttoabuilt-inwirelesstransmitterHUBorrouting,wirelessNICisresponsibleforreceivingthetransmittedsignalbytheAPclientpremiseequipment.WiththeAPasthewirednetworkHubingeneral,wirelessstationscanbequicklyandeasilyconnectedtothenetwork.Especiallyfortheuseofbroadband,Wi-Fievenmoreadvantages,cablebroadbandnetworks(ADSL,residentialLAN,etc.)tothehome,connectingtoanAP,theninstallawirelesscardinthecomputer.OrdinaryfamilieshaveanAPisenough,eventheneighborhoodoftheuser'sauthorization,youdonotneedtoaddportstoasharedInternet.Wi-Fiisthecomplementofhigh-speedwiredaccesstechnologiesAtpresent,thewiredaccesstechnologiesincludingEthernet,xDSL,etc.Wi-Fitechnologyasacomplementofhigh-speedwiredaccesstechnology,hastheadvantageofmobility,inexpensiveWi-Fitechnologyiswidelyusedinthefieldofneedawirelessextensionofwiredaccess,suchasthetemporaryvenue.Datarate,coverageandreliabilityofthedifference,Wi-Fitechnologyinbroadbandapplicationswillbeasacomplementofhigh-speedwiredaccesstechnologies.ThekeytechnologyisnodoubtdecidedtosupplementeffortsoftheWi-Fi.TheOFDM,MIMO(MultipleInputMultipleOutput)smartantennasandsoftwareradio,etc.,arebeginningtobeappliedtowirelesslocalareanetworkinordertoenhancetheperformanceofWi-Fi,suchas802.11nplanstouseMIMOandOFDMcombined,sothatthedataratehasdoubledandredoubled.Inaddition,theimprovementoftheantennaandtransmissiontechnologymakesthewirelessLANtransmissiondistanceisgreatlyincreasedandcanreachafewkilometers.Wi-Fiisthecomplementofcellularmobilecommunicationand3GSecondarypositioningoftheWi-Fitechnology----thecomplementofcellularmobilecommunication.Cellularmobilecommunicationcanprovideawidecoverage,highmobilityandthelowdatatransferrate,itcanusetheWi-Fihigh-speeddatatransmissioncharacteristicstocompensateforthedeficienciesoftheirowndatatransferrateislimited.Wi-Finotonlytheuseofcellularmobilecommunicationnetworkauthenticationandbillingmechanisms,andcharacteristicsofmulti-accessswitchingfunctioncanbecombinedwiththewidecoverageofcellularmobilecommunicationsnetwork.ThiscanbeachievedtheintegrationofWi-Fiandcellularmobilecommunications,cellularmobilecommunicationsoperatorsicingonthecake,tofurtherexpanditsbusinessvolume.Fortelecomoperators,Wi-Fitechnologypositioningisthecomplementofhigh-speedwiredaccesstechnology,willgraduallybecomethecomplementofcellularmobilecommunications.Ofcourse,Wi-Fiandcellularmobilecommunications,thereareasmallamountofcompetition.Ontheonehand,fortheWi-FiVoiceoverIPterminalhasenteredthemarket,partofthesubstitutioneffectonthecellularmobilecommunication.Ontheotherhand,withthedevelopmentofcellularmobilecommunicationtechnology,Wi-Fihotspotscommonapplicationmaybereplacedbycellularmobilecommunicationsystempart.Butingeneral,therelationshipofcoexistence,suchassomespecialoccasions,high-speeddatatransfermustbebymeansofWi-Fi,aircraftliketheBoeinginternalwirelessLANusingWi-Fi;whileonotheroccasionscanbemoreeconomical.liketoachievehigh-speedtrainswithinthewirelessLAN.Ithasahigheradvancedtechnology,strongbusinessskillsandawiderangeofapplications.ButtheWi-Ficanplayinspecificregionsandwithintheimportantcomplementaryrolefor3G,Wi-Fitechnologyand3Gtechnologythecombinationwillhavebroadprospectsfordevelopment.Wi-Fi技術(shù)Wi-Fi的全稱是WirelessFidelity，又叫802.11b標準。它的最大優(yōu)點就是傳輸速度較高，可以達到11Mbps，另外它的有效距離也很長，同時與已有的各種802.11DSSS設(shè)備兼容。伴隨著Intel公司提出的筆記本電腦芯片組?！把格Y”被越來越多的人認可，這一技術(shù)也逐漸成為了大家關(guān)注的話題。不過自2005年底開始，很多手機廠商，特別是以生產(chǎn)智能手機為主的品牌便開始將Wi-Fi引入自己的產(chǎn)品當(dāng)中。簡而言之：Wi-Fi就是無線網(wǎng)絡(luò)Wi-Fi已經(jīng)廣泛的應(yīng)用在了筆記本電腦，手機掌上電腦，數(shù)碼相機等移動終端上。有了Wi-Fi之后，不需要網(wǎng)線即可聯(lián)入網(wǎng)絡(luò)。越來越多的設(shè)備在出廠前安裝了Wi-Fi模塊，也有越來越多的場所提供了Wi-Fi信號覆蓋。這樣，Wi-Fi形成了一個從科研到設(shè)備生產(chǎn)、從網(wǎng)絡(luò)接入到網(wǎng)絡(luò)內(nèi)容服務(wù)等一個龐大的產(chǎn)業(yè)鏈。2007年，全國包括Wi-Fi在內(nèi)的wlan行業(yè)產(chǎn)業(yè)價值有望超億美元。對于個人用戶來說，Wi-Fi的普及，將是用戶體驗的一次飛躍。筆記本電腦用戶將可以任意一個具備Wi-Fi信號覆蓋的地方快速接入Internet而不需要再去尋找網(wǎng)線，越來越多的機場、酒店、公共場所都提供了Wi-Fi信號覆蓋。及時帶筆記本電腦開會，也不用擔(dān)心會議室沒有足夠的網(wǎng)線插口。而在家中，您更可以在任何一個角落都覆蓋無線信號，而不需要擔(dān)心網(wǎng)線的走線影響整體室內(nèi)美觀。Wi-Fi在掌上設(shè)備上應(yīng)用越來越廣泛，而智能手機就是其中一份子。與早前應(yīng)用于手機上的藍牙技術(shù)不同，Wi-Fi具有更大的覆蓋范圍和更高的傳輸速率，因此Wi-Fi手機成為了目前移動通信業(yè)界的時尚潮流。由于Wi-Fi的頻段在世界范圍內(nèi)是無需任何電信運營執(zhí)照的免費頻段，因此WLAN無線設(shè)備提供了一個世界范圍內(nèi)可以使用的，費用極其低廉且數(shù)據(jù)帶寬極高的無線空中接口。用戶可以在Wi-Fi覆蓋區(qū)域內(nèi)快速瀏覽網(wǎng)頁，隨時隨地接聽撥打電話。而其它一些基于WLAN的寬帶數(shù)據(jù)應(yīng)用，如流媒體、網(wǎng)絡(luò)游戲等功能更是值得用戶期待。有了Wi-Fi功能我們打長途電話(包括國際長途哦)，瀏覽網(wǎng)頁、收發(fā)電子郵件、音樂下載、數(shù)碼照片傳遞等，再無需擔(dān)心速度慢和花費高的問題?，F(xiàn)在Wi-Fi翻蓋范圍在國內(nèi)越來越廣泛了，高級賓館，豪華住宅區(qū)，飛機場以及咖啡廳之類的區(qū)域都有Wi-Fi接口。當(dāng)我們?nèi)ヂ糜危k公時，就可以在這些場所使用我們的掌上設(shè)備盡情網(wǎng)上沖浪了。一個Wi-Fi聯(lián)接點網(wǎng)絡(luò)成員和結(jié)構(gòu)站點(Station)，網(wǎng)絡(luò)最基本的組成部分。基本服務(wù)單元(BasicServiceSet,BSS)。網(wǎng)絡(luò)最基本的服務(wù)單元。最簡單的服務(wù)單元可以只由兩個站點組成。站點可以動態(tài)的聯(lián)結(jié)(associate)到基本服務(wù)單元中。分配系統(tǒng)(DistributionSystem,DS)分配系統(tǒng)用于連接不同的基本服務(wù)單元。分配系統(tǒng)使用的媒介(Medium)邏輯上和基本服務(wù)單元使用的媒介是截然分開的，盡管它們物理上可能會是同一個媒介，例如同一個無線頻段。接入點(AcessPoint,AP)接入點即有普通站點的身份，又有接入到分配系統(tǒng)的功能。擴展服務(wù)單元(ExtendedServiceSet,ESS)由分配系統(tǒng)和基本服務(wù)單元組合而成。這種組合是邏輯上，并非物理上的--不同的基本服務(wù)單元物有可能在地理位置相去甚遠。分配系統(tǒng)也可以使用各種各樣的技術(shù)。關(guān)口(Portal)也是一個邏輯成分。用于將無線局域網(wǎng)和有線局域網(wǎng)或其它網(wǎng)絡(luò)聯(lián)系起來。這兒有3種媒介，站點使用的無線的媒介，分配系統(tǒng)使用的媒介，以及和無線局域網(wǎng)集成一起的其它局域網(wǎng)使用的媒介。物理上它們可能互相重迭。IEEE802.11只負責(zé)在站點使用的無線的媒介上的尋址(Addressing)。分配系統(tǒng)和其它局域網(wǎng)的尋址不屬無線局域網(wǎng)的范圍。IEEE802.11沒有具體定義分配系統(tǒng)，只是定義了分配系統(tǒng)應(yīng)該提供的服務(wù)(Service)。整個無線局域網(wǎng)定義了9種服務(wù)，5種服務(wù)屬于分配系統(tǒng)的任務(wù)，分別為，聯(lián)接（Association),結(jié)束聯(lián)接(Diassociation),分配(Distribution),集成(Integration),再聯(lián)接(Reassociation)。4種服務(wù)屬于站點的任務(wù)，分別為，鑒權(quán)(Authentication),結(jié)束鑒權(quán)(Deauthentication),隱私(Privacy),MAC數(shù)據(jù)傳輸(MSDUdelivery)。Wi-Fi的主要技術(shù)優(yōu)勢1、無線電波的覆蓋范圍廣，基于藍牙技術(shù)的電波覆蓋范圍非常小，半徑大約只有50英尺左右，約合15米。而Wi-Fi的半徑則可達300英尺左右，約合100米。最近由Vivato公司推出的一款新型交換機，該款產(chǎn)品能夠把目前Wi-Fi無線網(wǎng)絡(luò)300英尺，接近100米的通信距離擴大到4英里，約6.5公里。2、雖然由Wi-Fi技術(shù)傳輸?shù)臒o線通信質(zhì)量不是很好，數(shù)據(jù)安全性能比藍牙差一些，傳輸質(zhì)量也有待改進，但傳輸速度非?？欤梢赃_到11Mbps，符合個人和社會信息化的需求。3、廠商進入該領(lǐng)域的門檻比較低。廠商只要在機場、車站、咖啡店、圖書館等人員較密集的地方設(shè)置“熱點”，并通過高速線路將因特網(wǎng)接入上述場所。這樣由于“熱點”所發(fā)射出的電波可以達到距接入點半徑數(shù)十米至100米的地方，用戶只要將支持無線LAN的筆記本電腦或PDA拿到該區(qū)域內(nèi)，即可高速接入因特網(wǎng)。也就是說廠商不用耗費資金來進行網(wǎng)絡(luò)布線接入，從而節(jié)省了大量的成本。Wi-Fi組建方法Wi-Fi是由AP（AccessPoint）和無線網(wǎng)卡組成的無線網(wǎng)絡(luò)。一般架設(shè)無線網(wǎng)絡(luò)的基本配備就是無線網(wǎng)卡及一臺AP，如此便能以無線的模式，