Zigbee无线传感器网络英文文献.docx
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Zigbee无线传感器网络英文文献
ZigbeeWirelessSensorNetworkinEnvironmentalMonitoringApplications
I.ZIGBEETECHNOLOGY
ZigbeeisawirelessstandardbasedonIEEE802.15.4thatwasdevelopedtoaddresstheuniqueneedsofmostwirelesssensingandcontrolapplications.Technologyislowcost,lowpower,alowdatarate,highlyreliable,highlysecurewirelessnetworkingprotocoltargetedtowardsautomationandremotecontrolapplications.It’sdepictstwokeyperformancecharacteristics–wirelessradiorangeanddatatransmissionrateofthewirelessspectrum.ComparingtootherwirelessnetworkingprotocolssuchasBluetooth,Wi-Fi,UWBandsoon,showsexcellenttransmissionabilityinlowertransmissionrateandhighlycapacityofnetwork.
A.ZigbeeFramework
Frameworkismadeupofasetofblockscalledlayers.Eachlayerperformsaspecificsetofservicesforthelayerabove.AsshowninFig.1.TheIEEE802.15.4standarddefinesthetwolowerlayers:
thephysical(PHY)layerandthemediumaccesscontrol(MAC)layer.TheAlliancebuildsonthisfoundationbyprovidingthenetworkandsecuritylayerandtheframeworkfortheapplicationlayer.
Fig.1Framework
TheIEEE802.15.4hastwoPHYlayersthatoperateintwoseparatefrequencyranges:
868/915MHzand2.4GHz.Moreover,MACsub-layercontrolsaccesstotheradiochannelusingaCSMA-CAmechanism.Itsresponsibilitiesmayalsoincludetransmittingbeaconframes,synchronization,andprovidingareliabletransmissionmechanism.
B.Zigbee’sTopology
Thenetworklayersupportsstar,tree,andmeshtopologies,asshowninFig.2.Inastartopology,thenetworkiscontrolledbyonesingledevicecalledcoordinator.Thecoordinatorisresponsibleforinitiatingandmaintainingthedevicesonthenetwork.Allotherdevices,knownasenddevices,directlycommunicatewiththecoordinator.Inmeshandtreetopologies,thecoordinatorisresponsibleforstartingthenetworkandforchoosingcertainkeynetworkparameters,butthenetworkmaybeextendedthroughtheuseofrouters.Intreenetworks,routersmovedataandcontrolmessagesthroughthenetworkusingahierarchicalroutingstrategy.Meshnetworksallowfullpeer-to-peercommunication.
Fig.2Meshtopologies
Fig.3isanetworkmodel,itshowsthatsupportsbothsingle-hopstartopologyconstructedwithonecoordinatorinthecenterandtheenddevices,andmeshtopology.Inthenetwork,theintelligentnodesarecomposedbyFullFunctionDevice(FFD)andReducedFunctionDevice(RFD).OnlytheFFNdefinesthefullfunctionalityandcanbecomeanetworkcoordinator.Coordinatormanagesthenetwork,itistosaythatcoordinatorcanstartanetworkandallowotherdevicestojoinorleaveit.Moreover,itcanprovidebindingandaddress-tableservices,andsavemessagesuntiltheycanbedelivered.
Fig.3Zigbeenetworkmodel
II.THEGREENHOUSEENVIRONMENTALMONITORING
SYSTEMDESIGN
Traditionalagricultureonlyusemachineryandequipmentwhichisolatingandnocommunicatingability.Andfarmershavetomonitorcrops’growthbythemselves.Evenifsomepeopleuseelectricaldevices,butmostofthemwererestrictedtosimplecommunicationbetweencontrolcomputerandenddeviceslikesensorsinsteadofwireconnection,whichcouldn’tbestrictlydefinedaswirelesssensornetwork.Therefore,bythroughusingsensornetworksand,agriculturecouldbecomemoreautomation,morenetworkingandsmarter.
Inthisproject,weshoulddeployfivekindsofsensorsinthegreenhousebasement.Bythroughthesedeployedsensors,theparameterssuchastemperatureinthegreenhouse,soiltemperature,dewpoint,humidityandlightintensitycanbedetectedrealtime.Itiskeytocollectdifferentparametersfromallkindsofsensors.Andinthegreenhouse,monitoringthevegetablesgrowingconditionsisthetopissue.Therefore,longerbatterylifeandlowerdatarateandlesscomplexityareveryimportant.Fromtheintroductionaboutabove,weknowthatmeettherequirementsforreliability,security,lowcostsandlowpower.
A.SystemOverview
TheoverviewofGreenhouseenvironmentalmonitoringsystem,whichismadeupbyonesinknode(coordinator),manysensornodes,workstationanddatabase.Motenodeandsensornodetogethercomposedofeachcollectingnode.Whensensorscollectparametersrealtime,suchastemperatureinthegreenhouse,soiltemperature,dewpoint,humidityandlightintensity,thesedatawillbeofferedtoA/Dconverter,thenbythroughquantizingandencodingbecomethedigitalsignalthatisabletotransmitbywirelesssensorcommunicatingnode.Eachwirelesssensorcommunicatingnodehasabilityoftransmitting,receivingfunction.
InthisWSN,sensornodesdeployedinthegreenhouse,whichcancollectrealtimedataandtransmitdatatosinknode(Coordinator)bythewayofmulti-hop.Sinknodecompletethetaskofdataanalysisanddatastorage.Meanwhile,sinknodeisconnectedwithGPRS/CDMAcanprovideremotecontrolanddatadownloadservice.Inthemonitoringandcontrollingroom,byrunninggreenhousemanagementsoftware,thesinknodecanperiodicallyreceivesthedatafromthewirelesssensornodesanddisplaysthemonmonitors.
B.NodeHardwareDesign
SensornodesarethebasicunitsofWSN.Thehardwareplatformismadeupsensornodescloselyrelatedtothespecificapplicationrequirements.Therefore,themostimportantworkisthenodesdesignwhichcanperfectimplementthefunctionofdetectingandtransmissionasaWSNnode,andperformitstechnologycharacteristics.Fig.4showstheuniversalstructureoftheWSNnodes.Powermoduleprovidesthenecessaryenergyforthesensornodes.Datacollectionmoduleisusedtoreceiveandconvertsignalsofsensors.Dataprocessingandcontrolmodule’sfunctionsarenodedevicecontrol,taskscheduling,andenergycomputingandsoon.Communicationmoduleisusedtosenddatabetweennodesandfrequencychosenandsoon.
Fig.4Universalstructureofthewsnnodes
Inthedatatransferunit,themoduleisembeddedtomatchtheMAClayerandtheNETlayeroftheprotocol.WechooseCC2430astheprotocolchips,whichintegratedtheCPU,RFtransceiver,netprotocolandtheRAMtogether.CC2430usesan8bitMCU(8051),andhas128KBprogrammableflashmemoryand8KBRAM.ItalsoincludesA/Dconverter,someTimers,AES128Coprocessor,WatchdogTimer,32KcrystalSleepmodeTimer,PoweronReset,BrownoutDetectionand21I/Os.Basedonthechips,manymodulesfortheprotocolareprovided.Andthetransferunitcouldbeeasilydesignedbasedonthemodules.
Asanexampleofasensorenddeviceintegratedtemperature,humidityandlight,thedesignisshowninFig.5.
Fig.5Thehardwaredesignofasensornode
TheSHT11isasinglechiprelativehumidityandtemperaturemultisensormodulecomprisingacalibrateddigitaloutput.Itcantestthesoiltemperatureandhumidity.TheDS18B20isadigitaltemperaturesensor,whichhas3pinsanddatapincanlinkMSP430directly.Itcandetecttemperatureingreenhouse.TheTCS320isadigitallightsensor.SHT11,DS18B20andTCS320arebothdigitalsensorswithsmallsizeandlowpowerconsumption.Othersensornodescanbeobtainedbychangingthesensors.
Thesensornodesarepoweredfromonboardbatteriesandthecoordinatoralsoallowstobepoweredfromanexternalpowersupplydeterminedbyajumper.
C.NodeSoftwareDesign
Theapplicationsystemconsistsofacoordinatorandseveralenddevices.Thegeneralstructureofthecodeineachisthesame,withaninitializationfollowedbyamainloop.
Thesoftwareflowofcoordinator,uponthecoordinatorbeingstarted,thefirstactionoftheapplicationistheinitializationofthehardware,liquidcrystal,stackandapplicationvariablesandopeningtheinterrupt.Thenanetworkwillbeformatted.Ifthisnethasbeenformattedsuccessfully,somenetworkinformation,suchasphysicaladdress,netID,channelnumberwillbeshownontheLCD.Thenprogramwillstepintoapplicationlayerandmonitorsignal.Ifthereisenddeviceorrouterwanttojoininthisnet,LCDwillshownthisinformation,andshowthephysicaladdressofapplyingnode,andthecoordinatorwillallocateanetaddresstothisnode.Ifthenodehasbeenjoinedinthisnetwork,thedatatransmittedbythisnodewillbereceivedbycoordinatorandshownintheLCD.
Thesoftwareflowofasensornode,aseachsensornodeisswitchedon,itscansallchannelsand,afterseeinganybeacons,checksthatthecoordinatoristheonethatitislookingfor.Itthenperformsasynchronizationandassociation.Onceassociationiscomplete,thesensornodeentersaregularloopofreadingitssensorsandputtingoutaframecontainingthesensordata.Ifsendingsuccessfully,enddevicewillstepintoidlestate;bycontrast,itwillcollectdataonceagainandsendtocoordinatoruntilsendingsuccessfully.
D.GreenhouseMonitoringSoftwareDesign
WeuseVBlanguagetobuildaninterfaceforthetestandthisgreenhousesensornetworksoftwarecanbeinstalledandlaunchedonanyWindows-basedoperatingsystem.Ithas4dialogboxselections:
settingcontrollingconditions,settingTimer,settingrelevantparametersandshowingcurrentstatus.Bysettingsomeparameters,itcanperformthefunctionsofcommunicatingwithport,datacollectionanddataviewing.
Zigbee无线传感器网络在环境监测中的应用
I.Zigbee技术
Zigbee是一种基于IEEE802.15.4的无线标准上被开发用来满足大多数无线传感和控制应用的独特需求。
Zigbee技术是低成本,低功耗,低数据速率,高可靠性,高度安全的无线网络协议实现自动化和远程控制应用的目标。
它描述了两个关键的性能特点—无线射频范围和无线频谱的数据传输速率。
相较于其他如蓝牙,Wi-Fi技术,超宽带等无线网络协议,Zigbee虽然传输速率慢但传输容量大的特点向我们展示了他出色的传输能力。
A、技术框架
Zigbee的框架是由一组层组成的。
上述层中每一层都要执行一组特定的服务任务。
图1所示。
在IEEE802.15.4标准定义了两个较低层:
物理层(PHY)和媒体接入控制(MAC)层。
Zigbee联盟建立在网络层和安全层及应用层框架提供的基础上。
图1技术框架
在IEEE802.15.4有两个PHY层,它们在两个不同的频率范围操作:
868/915兆赫和2.4GHz。
此外,MAC子层控制访问无线电频道使用的CSM