Zigbee无线传感器网络英文文献与翻译.doc

Zigbee无线传感器网络英文文献与翻译.doc

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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检测中的应用

1.Zigbee技术

Zigbee是一种基于IEEEE802.15.4的无线标准上被开发用来满足大多数无线传感器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的框架是有一组层组成的。

上诉层中每一层都要执行一组特定的服务任务。

如图所示。

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