《无线技术简介》PPT课件.ppt

IntroductiontoWirelessNetworks Chapter1 McGraw Hill Irwin 2007TheMcGraw HillCompanies AllRightsReserved Objectives ExaminewirelesstechnologyanditsapplicationsAssesswirelessnetworkingtechnologiesReviewwirelessnetworkapplicationsDiscusstheissuesandconstraintsofawirelessnetwork WhyChooseaWirelessLAN ChooseaWirelessLAN WheninstallinganewLANWhenextendinganexistingLANWhenreplacinganexistingwiredLAN ConsiderationsWhenInstallingaNewLAN WiredLANsMaybelessexpensiveMorereliableEasiertomanageandtroubleshoot WirelessLANs WLANs WheninstallingcableisnotpracticalNetworkistemporaryDynamicphysicalconfiguration ExtendingaWiredNetwork ToaddadditionalworkstationstothenetworkProvideusersawaytoaccesstheirworkstationawayfromtheirdesk IssueswithWirelessLANs MaterialsusedinconstructionofbuildingmayimpederadiofrequencycommunicationInterferencefromotherRFdevicesShapeoftheareawherewirelessaccessisdesired WiredSmallOffice HomeOffice AhomenetworkusingasharedInternetconnection WirelessSmallOffice HomeOffice AwirelessLANusingacablemodemorDSLbridgetoconnecttotheInternet WLANConnectedtoWiredNetwork Wirelessaccesspointsareoftenusedtoprovideaconnectiontoawirednetwork CostIssues AwirelessnetworkeliminatesthecostofcablerunsAwirelessnetworkeliminatesthecostofinstallingthecableAwirelessnetworkprovidesimmediateconnectionanywhereinthewirelessrangeofitsaccesspoints Scalability Scalabilityisthenetwork sabilitytochangeasneededtomeettheexpandingneedsofanorganizationorhomeWirelessnetworksaregenerallymorescalablethanawirednetworkawirelessworkstationonlyneedstobewithintherangeoftheaccesspoint Interoperability TheInternationalOrganizationforStandardization ISO developedtheOpenSystemsInterconnectionReferenceModel OSI tohelpensureallmanufacturer sequipmentwouldbeinteroperable ThephysicallayerPHYstandardsdefinethemediumThedatalinkMACstandardsdefinehowtocontrolaccesstothemedium Portability Forsoftware thecapabilityofasoftwareprogramtorunondifferentoperatingsystemsorhardwaremodelsForhardware adevice scapabilitytomovefromonestandards basednetworkingenvironmenttoanother IntegrationwithExistingNetworks StandardsprovidetheabilityforonetypeofnetworktobeintegratedintoanothertypeofnetworkWirelessnetworkingcanbeusedtoextendanexistingnetworktoareasthathaveeithernotbeencabledoraretoodifficultorcostlytocable IntegrationwithExistingNetworks Awirelessaccesspointcanbeusedtointegratewirelessdevicesintoanexistingwirednetwork TheWirelessNetworkingMarket MajorWirelessMarkets MobilepersonaldevicesWirelessnetworkingdevicesRFIDdevicesHealthandmedicalcaredevicesCommercialapplications MobilePersonalDevices AhandheldmobilePDAdevice PhotocourtesyofCasioComputerCompany LTD Amobiledevicethatincludeswirelesscommunicationscapabilities PhotocourtesyofFujitsuSiemensComputers ApocketPCmobiledeviceiscapableofmanycomputingfunctions PhotocourtesyofHewlett Packard WirelessNetworkAdapters NetworkadaptersprovidearadiolinktoawirelessnetworkaccesspointoranotherwirelessdeviceAlsocalledNetworkInterfaceCards NICs ANICforawirelessnetworkconnection PhotocourtesyofCiscoSystems Inc APCCardwirelessnetworkadapter PhotocourtesyofCiscoSystems Inc AccessPoints Accesspoints APs connectwirelessworkstationstowirednetworksortootherwirelessworkstations Awirelessaccesspoint PhotocourtesyofCiscoSystems Inc WirelessSwitches WLANswitchesreducetheamountofbroadcasttrafficpassedfromwirelessnetworksegmentstoawirednetwork WirelessPrintServers Printserversallowaprintertobeconnectedindependentlytoawirelessnetwork Astandalonewirelessprintserver PhotocourtesyofCiscoSystems Inc Aprinterinsertionmodulethatenablesawirelessnetworkconnection PhotocourtesyofHewlett Packard WirelessRouters Wirelessroutersprovidethefunctionsofanaccesspoint awirelessswitch andarouter Awirelessroutercansupportseveralwirelessworkstations aswellaswiredworkstations PhotocourtesyofCiscoSystems Inc WirelessBridges WirelessbridgesconnecttwoormoreLANs wiredorwireless AwirelessbridgeisusedtoconnectLANsintwoseparatebuildings PhotocourtesyofCiscoSystems Inc WirelessRepeaters WirelessrepeaterscanbeusedtoextendtherangeofaWLANbyrebroadcastingthesignalsitreceivesafterconditioningthemforincreasedstrengthandclarity AwirelessrepeaterisusedtoincreasethetransmissionrangeofaWLAN PhotocourtesyofBuffaloTechnology USA Inc Antennas Antennasareusedinwirelessnetworkstoreceiveandtransmitsignalsthroughtheair AnauxiliaryantennacanhelpovercomesignalstrengthissuesinaWLAN PhotocourtesyofD LinkSystems Inc VoiceOverIP VoIP VoiceOverIPallowstelephonesignalstobecarriedoverdatanetworksWirelessVoIPsupportsmobile orroaming usersTelephonesmustincludeanRFtransmitter receiver andantenna AwomanusingaBlackberryasawirelesstelephone PhotocourtesyofResearchinMotion Ltd RadioFrequencyIdentification RadioFrequencyIdentification RFID isanRF basedsystemthatcanretrieveandstoreinformationindevicescalledRFIDtags RFIDtransparentlabelsshowingtheirinternalcircuitry PhotocourtesyofTexasInstruments Inc RFIDs ActiveUsesaninternalpowersourceMaytransmitmoreinformation PassiveUsespowerfromtheincomingsignaltotransmititsinformation WirelessMedicalTelemetrySystem WirelessMedicalTelemetrySystems WMTS areusedtoreceiveortransmitinformationregardingthehealthorstatuspatientsAllowspatientstobetrackedoutsideofahospital TheWMTSsystemuseswirelesstechnologytomonitorpatients PersonalAreaNetworks PersonalAreaNetworks PANs mayusewirelesssensorsembeddedintobiomechanicaldevices suchasprosthesisarmsandlegs tocommunicatewithbody mountedorembeddedcontrollerdevicestocontrolandmonitorthemovementofartificiallimbs Awirelessreceiverembeddedinsidetheeyeballreceivesimagestransmittedbyamicro videocameratoprovidesighttoavision impairedperson ImagecourtesyoftheUniversityofSouthernCalifornia IndustrialandCommercialDevices Wirelesssensorsmonitorproductionlinesandsecuregoodswithinmanufacturing Awirelessmicrosensorcanbeembeddedinmanyindustrialappliances PhotocourtesyofMicroStrain Inc WirelessNetworkingIssuesandConstraints RFBandwidthAllocation TheFederalCommunicationsCommission FCC isresponsiblefortheallocation licensing registration andmanagementoftheRFbandsnotusedforgovernmentandmilitarypurposes RFBandLicensing TherearetwounlicensedbandsIndustrial Scientific andMedical ISM band2 4GHzto2 4835GHzUsedforcordlesstelephones babymonitors emergencyservicesradio andwirelessnetworkingUnlicensedNationalInformationInfrastructure UNII 4 9GHzto5 825GHzPrimarilyusedforwirelessnetworking RFInterference Radiofrequencyinterference RFI BroadcastsourcessuchasAM FMradio amateurradio remotecontrols wirelessphones microwaveovensElectromagneticinterference EMI Sourcesincludelightdimmers fluorescentlights TVs computerdisplays Security WirelessnetworkingtransmitsdatathrutheairwhichallowsforeasiereavesdroppingSecurityisanimportantconcernforcompaniesandusersthinkingaboutwirelessnetworking HealthandSafetyIssues ThehealtheffectsofRFdevicesonhumansisunknownSomesuggestthatRFradiationmaycausecancer Summary WhyChooseaWirelessLAN Theissuestobeconsideredwhenmakingadecisionbetweenawirelessandawirednetworkare cost easeofinstallation scalability andflexibility Wirelessnetworkingisawirereplacementtechnology Nonetworkiscompletelywireless evenaWLANmayrequiresomecablingtoconnectthegatewaytotheserviceprovider snetwork Awirelessnetworkeliminatesthecostofcablerunsbetweenthenetwork sworkstationsandperipheraldevicestotheInternetgateway Awirelessnetworkeliminatesthecostofinstallingthecable WhyChooseaWirelessLAN Thescalabilityofanetworkreferstothenetwork sabilitytochangeasneededtomeetexpandingneedsofanorganizationorhome Networkmodelsandstandardsprovidenetworkdesigners installers anduserswithacertainlevelofinteroperability Portabilityreferstoadevice scapabilitytomovefromonestandards basednetworkingenvironmenttoanother TheWirelessNetworkingMarket Mostwirelessdeviceshaveafairlylimitedandnarrowlydefinedapplication butmanycanbeadaptedtomeetotherapplications Themarketsforwirelessdevicesare mobilepersonaldevices wirelessnetworkingdevices RFIDdevices healthandmedicalcaredevices andcommercialapplications Today swirelesspersonaldevicesincludeenoughprocessingpowerandstoragetoreplacethelaptopandnotebookcomputersofnotsolongago ThegeneralclassesofWLANdevicesare NICsandnetworkadapters accesspoints WLANswitches printservers wirelessrouters wirelessbridges wirelessrepeaters andantennae TheWirelessNetworkingMarket RFIDsystemshavethecapabilitytoretrieveandstoreinformationindevicescalledRFIDt