《专业英语》-Unit4教学材料

Lesson11BluetoothKeywordsbluetooth蓝牙destination目的地convenience方便technology技术exchange交换equipment设备standard标准frequency频率bandwidth带宽piconet微微网electronic电子的infrastructure基础设施下一页返回device设备application应用interface接口radio射频protocol协议spectrum谱license许可证numerous许多的simultaneously同时pave铺，铺满analogous相似的，相同frequencyhopping频率跳跃Lesson11BluetoothThebluetoothasshowninFig11-1Underthehelpofmoderntechnology,moreandmorepeoplebegintoworkinthehome(SOHO).Inthepast,variouswiresmadetheofficeconfused,sometimes,evenledtodanger.Butnow,weusebluetooth,asshowninFig11-2,thewiredisappeared,thewholeofficeworkinanefficientstatusasamachine.Whenweshuttleamongtheworkplace,thefamilyandotherdestinations,bluetoothhelpsusaccessimportantinformationandestablishpersonalconnection下一页上一页返回Lesson11BluetoothWhatisbluetoothtechnologyBluetoothtechnologysupportsshortcommunication(within10meters)asshowninFig11-3.Itcanrealizethewirelessinformationexchangeamongthemobilephone,wirelessheadsetsandotherrelatedequipmentIEEE802.15isthetechnicalstandard,theoperatingfrequencybandis2.4GHz,thebandwidthis1MB/s下一页上一页返回Lesson11BluetoothBluetoothtechnology,asshowninFig11-4,isauniversalradiointerfaceinthe2.45GHzfrequencybandthatenablesportableelectronicdevicestoconnectandcommunicatewirelesslyviashortrange,adhocnetworkEachunitcansimultaneouslycommunicatewithuptoseveralotherunitsperpiconet.Moreover,eachunitcansimultaneouslybelongtoseveralpiconets,asshowninFig11-5

下一页上一页返回Lesson11BluetoothWhatarethecharacteristicsofbluetoothtechnology1MB/ssymbolrateexploitsmaximumavailablechannelbandwidth;Fastfrequencyhoppingavoidsinterference;Adaptiveoutputpowerminimizesinterference;Shortdatapacketsmaximizeinterference;Fastacknowledgementallowslowcodingoverheadforlinks;Flexiblepackettypessupportwideapplicationrange;下一页上一页返回Lesson11BluetoothAirinterfacetailoredtominimizecurrentconsumption;CVSD(continuousvariableslopedeltamodulation)voicecodingenablesoperationathighbiterrorrates下一页上一页返回Lesson11BluetoothThebasictechnicalinformationandapplicationThebasictechnicalinformationasshowninFig11-6Baseduponasmall,highperformanceintegratedradiotransceiver,eachofwhichisallocatedaunique48bitaddressderivedfromtheIEEE802standard;Operateintheunrestricted2.45GHzISMfreeband,whichisavailablegloballyalthoughslightvariationoflocationandwidthofbandapply;下一页上一页返回Lesson11BluetoothRangesetat10mtooptimizefortargetmarketofmobileandbusinessuser;Grossdatarate1MB/swithsecondgenerationplanningtoincreaseto2MB/sOnetooneconnectionsallowmaximumdatatransferrateof721KB/s(3voicechannels);Usespacketswitchingprotocolbasedonfrequencyhopschemewith1,600hops/stoenablehighperformanceinnoisyradioenvironments.Theentireavailablefrequencyspectrumisusedwith79hopsof1MHzbandwidth,analogoustotheIEEE802.11standard;下一页上一页返回Lesson11BluetoothLowpowerconsumptionlongevityforbatterypowereddevicesDuringdatatransferthemaximumcurrentdrainis30mA.However，duringpausesoratlowerdataratesitwillbelower下一页上一页返回Lesson11BluetoothBluetoothtechnologyisfreeforallthepeople,theuseofbluetoothasshowninFig11-7andFig11-8.Itworksin2.4GHzbandwithoutlicensing,andcanbeusedinindustrial,technology,medicine(ISM).Theproductsintegratedthetechnology,frommobilephones,carstothemedicalequipment,moreover,theusersfromconsumers,industrialmarketstoenterprises,aretoonumeroustomentiononebyoneBluetoothisanimmediatetechnique,itdoesnotrequirearegularinfrastructure,andiseasytoinstallandsetup上一页返回Lesson12GPRSKeywordsGPRS通用分组无线服务技术message消息voice声音image图像information信息service服务switch转换packet包transmission传输下一页返回distribute分配channel信道sender发送者recipient接收者mobile手机compression压缩communication通信muter路由器termination终端Lesson12GPRSWeoftenusemobilestosendshortmessagesandsomeofthemcarryvoiceandimagesFurthermore,mobileinternetbrowsingisnotanewexperienceforus.Then,wewouldaskfromwhereandhowtheinformationistransported.Weusuallyhearoftheword“GPRS”,asshowninFig12-1,butwhatisit?Now,wewillgivetheintroductionaboutGPRS下一页上一页返回Lesson12GPRSWhatisGPRSNetworkstructureofGPRSasshowninFig12-2GPRS,GeneralPacketRadioService,isthemobiledataservicesusedbyGSMmobilephoneusersGPRSisaversionofupgratedGSMnetworkandoftendescribedas“2.5G”.ItusesthePRIIPswitchtechnology下一页上一页返回Lesson12GPRSInthepacketswitching,dataaredividedintounitswithasubgrouphead,andtheaddressflagindicatestowherethegroupisissued.Beforedatatransmission,thereisnoneedtodistributechannelandestablishaconnection.Whenastreamofmessagepackagearrives,accordingtotheinformationincludedintheheads,youcanfindausablechanneltosendthedata.Inthiswayoftransmission,thereisnofixedchanneloccupationbetweenthesenderandrecipient.Alluserssharethechannel,asshowninFig12-3

下一页上一页返回Lesson12GPRSGGSNandSGSNAsshowninFig12-4andFig12-5,GPRSincreasedSGSN,GGSNandotherfunctionsentitiesintheexistingGSMnetworkSGSN,servingGPRSsupportnode,providesservicesforMS,andcooperateswithMSC/VLR/EIRtocompletethemobilitymanagementfunction,forinstance,roaming,registration,switchesandauthentication.SGSNcompletesdataswitching,addresstranslation,encryptionandcompression下一页上一页返回Lesson12GPRSGGSN,gatewayGPRSsupportnode,isconsideredasgatewayorroutertoconnectGPRSandPSPDNadoptingX.25andX.75agreements,ofcourse,itcanconnectwithotherGPRSGGSNtogetherwithSGSNfinishtheroutingfunctionofGPRS下一页上一页返回Lesson12GPRSGPRSprotocol

UminterfaceistheairinterfaceofGSM.Therearefivecommunicationprotocols,includingphysicallayer,MAC(MediumAccessControl),LLC(LogicalLinkControl),SNDC(SubNetworkDependantConvergence)andnetworklayer下一页上一页返回Lesson12GPRSPhysicallayeristheRFinterfacepart.MACmainlydefinesanddistributestheGPRSlogicalchannels,sothatdifferentMScouldsharethesechannels.LLCisthewirelesslinkagreementbasedontheHDLC.LLRintheBSSisresponsiblefortheLLCframebetweenMSandSGSNSNDC,SubNetworkDependantConvergence,completesthepackageandgroupofdata,anddeterminesTCP/IPaddressandencryptionways.NetworklayerprovidesTCP/IPandL25protocols下一页上一页返回Lesson12GPRSEasytoplayaroundGPRSInserttheSIMcardwithGPRSfunctionintotheGPRSwirelessnetworkcard,thenconnecttothemobiletermination(notebookcomputerorPDA),atlast,wecansurfonthewirelessnetworkandreceiveordispatchshortmessages.Ofcourse,wecouldalsoconnectGPRSmobilephoneswithnotebookcomputerSATAbydataconnection,USBorinfraredportTherearesomanymobilephoneswithGPRSfunctions,inaddition,mostofthemhaveWAPIfyourphonedoesn’thave,nevermind,followme,it’ssimple上一页返回Lesson13WirelessLANKeywordswireless无线的environment环境management管理area区域BSS基本服务集ESS独立基本服务集portable手提式的approach接近point-to-point点对点traditional传统的下一页返回model模型cable电缆reliable可信的subscriber用户interference干扰loss损耗security安全distance距离noise噪声Lesson13WirelessLANAsshowninFig13-1,wirelessnetworksinourlivescanbeseeneverywhere.Forexample,afterweshoppedinthesupermarket,thecashierneededtoswipethepriceandcalculatehowmuchwemustpay.Infact,thatisonekindofwirelessnetwork.Generallyspeaking,wirelessLANisnotacablenetwork.WejustneedtoinstallPCcardonthenotebookcomputerorPC,wecouldmovefreebutstillkeeppersistentconnectionswiththenetoverthewirelessnetworkcoveragearea.WirelessLANisnotusedtoreplacethecablenetworks,butasanextensionofwirednetworks下一页上一页返回Lesson13WirelessLANWirelessLANarchitectureAsshowninFig13-2,wirelessLAN（WirelessLocalAreaNetwork,usesthewirelesscommunicationstechnologytoconnectthecomputerequipments,makesupanetworkwhichcancommunicateeachotherandsharetheresources.Awirelesslocalareanetworkprovidesconnectivityovertheairwaveswithinalocalarea,suchasabuilding.下一页上一页返回Lesson13WirelessLANThedevicesarecapableoftransmittinginformationupto304.8mbetweencomputerswithinanopenenvironment.MostwirelessLANproductsofferSimpleNetworkManagementProtocol(SNMP)，asshowninFig13-3,tosupportnetworkmanagementthroughtheuseofSNMPbasedmanagementplatformsandapplications.下一页上一页返回Lesson13WirelessLANAsetofinterconnectBSSsandintegratedLANsformasingleESSStationswithinanESScancommunicatewitheachotherthroughAP.MobilestationsmaymovefromoneBSStoanothertransparentlyinLLCAnyentitythathasSTAfunctionalityprovidesaccesstotheDS.ThelogicalpointatwhichMACservicedataunits(MSDUs)fromanonIEEE802.11LANenterstheDSofanESS下一页上一页返回Lesson13WirelessLANTwomodelsofwirelessLANAsshowninFig13-4,IBSSisasetofstationsthatcommunicatewithoneanotherdirectly.Thereisnoconnectiontoawirednetwork,onlymobilestations.Itisshortlivednetwork.BSSincludesanaccesspoint(AP).ThecommunicationbetweenstationsmustgothroughAP.TheAPmayhaveconnectiontothewiredLAN.AllthestationscommunicatewiththeAP.TheAPprovidesthelocalrelayfunctionfortheBSSandactsasamasterduringtheconnectionfreeperiod.Moreover,theAPcanbufferthetrafficfromamobilestationwhichisinaverylowpowerstate下一页上一页返回Lesson13WirelessLANWirelessLANtechnologies

AsshowninFig13-5,thereareseveralwirelessLANspecificationsandstandardsthatyoucanchoose802.11isexpectedtocontinuebeingthepreferredstandardforsupportingwirelessLANapplications.Othertechnologies,suchasHiperLAN,HomeRFSWAP,andBluetooth,maybecomestrongercompetitorsto802.11inthefuture.下一页上一页返回Lesson13WirelessLANWirelessLANapplications

AsshowninFig13-6and13-7,wirelessnetworkingmakesitpossibletoplaceportablecomputersinthehandsofmobilefront-lineworkerssuchasdoctors,nurses,warehouseclerks,inspectors,claimsadjusters,realestateagents,andinsurancesalespeople.Thewirelesscomputerapproachusingacentralizeddatabaseissuperior下一页上一页返回Lesson13WirelessLANSomeproblemsOfcours