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1、兰州交通大学毕业设计(英文文献)ZigbeeWirelessSensorNetworkinEnvironmentalMonitoringApplicationsI.ZIGBEETECHNOLOGYZigbeeisawirelessstandardbasedonIEEE802.15.4thatwasdevelopedtoaddresstheuniqueneedsofmostwirelesssensingandcontrolapplications.Technologyislowcost,lowpower,alowdat
2、arate,highlyreliable,highlysecurewirelessnetworkingprotocoltargetedtowardsautomationandremotecontrolapplications.It’sdepictstwokeyperformancecharacteristics–wirelessradiorangeanddatatransmissionrateofthewirelessspectrum.Comparingtootherwirelessnetworkingprotoco
3、lssuchasBluetooth,Wi-Fi,UWBandsoon,showsexcellenttransmissionabilityinlowertransmissionrateandhighlycapacityofnetwork.A.ZigbeeFrameworkFrameworkismadeupofasetofblockscalledlayers.Eachlayerperformsaspecificsetofservicesforthelayerabove.AsshowninFig.1.TheIEEE802.
4、15.4standarddefinesthetwolowerlayers:thephysical(PHY)layerandthemediumaccesscontrol(MAC)layer.TheAlliancebuildsonthisfoundationbyprovidingthenetworkandsecuritylayerandtheframeworkfortheapplicationlayer.Fig.1FrameworkTheIEEE802.15.4hastwoPHYlayersthatoperateintw
5、oseparatefrequencyranges:868/915MHzand2.4GHz.Moreover,MACsub-layercontrolsaccesstotheradiochannelusingaCSMA-CAmechanism.Itsresponsibilitiesmayalsoincludetransmittingbeaconframes,synchronization,andprovidingareliabletransmissionmechanism.B.Zigbee’sTopologyThenet
6、worklayersupportsstar,tree,andmeshtopologies,asshowninFig.2.Inastartopology,thenetworkiscontrolledbyonesingledevicecalledcoordinator.Thecoordinator11兰州交通大学毕业设计(英文文献)isresponsibleforinitiatingandmaintainingthedevicesonthenetwork.Allotherdevices,knownasenddevices
7、,directlycommunicatewiththecoordinator.Inmeshandtreetopologies,thecoordinatorisresponsibleforstartingthenetworkandforchoosingcertainkeynetworkparameters,butthenetworkmaybeextendedthroughtheuseofrouters.Intreenetworks,routersmovedataandcontrolmessagesthroughthen
8、etworkusingahierarchicalroutingstrategy.Meshnetworksallowfullpeer-to-peercommunication.Fig.2MeshtopologiesFig.3isanetworkmodel,itshowsthatsupportsbothsingle-hopstartopologyc
