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WirelesssensornetworkWikiPidia

Wirelesssensornetwork

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TypicalMultihopWirelessSensorNetworkArchitecture

Awirelesssensornetwork（WSN）isawirelessnetworkconsistingofspatiallydistributedautonomousdevicesusingsensorstocooperativelymonitorphysicalorenvironmentalconditions,suchastemperature,sound,vibration,pressure,motionorpollutants,atdifferentlocations.[1][2]Thedevelopmentofwirelesssensornetworkswasoriginallymotivatedbymilitaryapplicationssuchasbattlefieldsurveillance.However,wirelesssensornetworksarenowusedinmanyindustrialandcivilianapplicationareas,includingindustrialprocessmonitoringandcontrol,machinehealthmonitoring,environmentandhabitatmonitoring,healthcareapplications,homeautomation,andtrafficcontrol.[1][3]

Inadditiontooneormoresensors,eachnodeinasensornetworkistypicallyequippedwitharadiotransceiverorotherwirelesscommunicationsdevice,asmallmicrocontroller,andanenergysource,usuallyabattery.Theenvisagedsizeofasinglesensornodecanvaryfromshoebox-sizednodesdowntodevicesthesizeofgrainofdust,[1]althoughfunctioning'motes'ofgenuinemicroscopicdimensionshaveyettobecreated.Thecostofsensornodesissimilarlyvariable,rangingfromhundredsofpoundstoafewpence,dependingonthesizeofthesensornetworkandthecomplexityrequiredofindividualsensornodes.[1]Sizeandcostconstraintsonsensornodesresultincorrespondingconstraintsonresourcessuchasenergy,memory,computationalspeedandbandwidth.[1]

Asensornetworknormallyconstitutesawirelessad-hocnetwork,meaningthateachsensorsupportsamulti-hoproutingalgorithm（severalnodesmayforwarddatapacketstothebasestation）.

Incomputerscienceandtelecommunications,wirelesssensornetworksareanactiveresearchareawithnumerousworkshopsandconferencesarrangedeachyear.

Contents

[hide]

∙1Applications

o1.1Areamonitoring

o1.2Environmentalmonitoring

∙2Characteristics

∙3Platforms

o3.1Standards

o3.2Hardware

o3.3Software

▪3.3.1Operatingsystems

▪3.3.2Middleware

▪3.3.3Programminglanguages

▪3.3.4Algorithms

∙4Simulators

∙5Datavisualization

∙6Seealso

∙7References

∙8Furtherreading

o8.1Journals

∙9Externallinks

Applications

TheapplicationsforWSNsaremanyandvaried,buttypicallyinvolvesomekindofmonitoring,tracking,andcontrolling.SpecificapplicationsforWSNsincludehabitatmonitoring,objecttracking,nuclearreactorcontrol,firedetection,andtrafficmonitoring.Inatypicalapplication,aWSNisscatteredinaregionwhereitismeanttocollectdatathroughitssensornodes.

Areamonitoring

AreamonitoringisacommonapplicationofWSNs.Inareamonitoring,theWSNisdeployedoveraregionwheresomephenomenonistobemonitored.Forexample,alargequantityofsensornodescouldbedeployedoverabattlefieldtodetectenemyintrusioninsteadofusinglandmines.[4]Whenthesensorsdetecttheeventbeingmonitored（heat,pressure,sound,light,electro-magneticfield,vibration,etc）,theeventneedstobereportedtooneofthebasestations,whichcantakeappropriateaction（e.g.,sendamessageontheinternetortoasatellite）.Dependingontheexactapplication,differentobjectivefunctionswillrequiredifferentdata-propagationstrategies,dependingonthingssuchasneedforreal-timeresponse,redundancyofthedata（whichcanbetackledviadataaggregationtechniques）,needforsecurity,etc.

Environmentalmonitoring

AnumberofWSNdeploymentshavebeendoneinthepastinthecontextofenvironmentalmonitoring[5].Manyofthesehavebeenshortlived,oftenduetotheprototypicalnatureoftheprojects.Amorelong-liveddeploymentismonitoringthestateofpermafrostintheswissalps:

ThePermaSenseProject,PermaSenseLiveDataBrowser.

Characteristics

Thissectiondoesnotciteanyreferencesorsources.Pleasehelpimprovethisarticlebyaddingcitationstoreliablesources.Unverifiablematerialmaybechallengedandremoved.（August2006）

UniquecharacteristicsofaWSNinclude:

∙Limitedpowertheycanharvestorstore

∙Abilitytowithstandharshenvironmentalconditions

∙Abilitytocopewithnodefailures

∙Mobilityofnodes

∙Dynamicnetworktopology

∙Communicationfailures

∙Heterogeneityofnodes

∙Largescaleofdeployment

∙Unattendedoperation

Sensornodescanbeimaginedassmallcomputers,extremelybasicintermsoftheirinterfacesandtheircomponents.Theyusuallyconsistofaprocessingunitwithlimitedcomputationalpowerandlimitedmemory,sensors（includingspecificconditioningcircuitry）,acommunicationdevice（usuallyradiotransceiversoralternativelyoptical）,andapowersourceusuallyintheformofabattery.Otherpossibleinclusionsareenergyharvestingmodules,secondaryASICs,andpossiblysecondarycommunicationdevices（e.g.RS-232orUSB）.

ThebasestationsareoneormoredistinguishedcomponentsoftheWSNwithmuchmorecomputational,energyandcommunicationresources.Theyactasagatewaybetweensensornodesandtheenduser.

Platforms

Standards

Severalstandardsarecurrentlyeitherratifiedorunderdevelopmentforwirelesssensornetworks.ZigBeeisamesh-networkingstandardintendedforusessuchasembeddedsensing,medicaldatacollection,consumerdevicesliketelevisionremotecontrols,andhomeautomation.Zigbeeispromotedbyalargeconsortiumofindustryplayers.WirelessHARTisanextensionoftheHARTProtocolandisspecificallydesignedforIndustrialapplicationslikeProcessMonitoringandControl.WirelessHARTwasaddedtotheoverallHARTprotocolsuiteaspartoftheHART7Specification,whichwasapprovedbytheHARTCommunicationFoundationinJune2007[6].6LoWPAN[7]istheIETFstandardstrackspecificationfortheIP-to-MAC-LayermappingforIPv6onIEEE802.15.4.ISA100isanewstandardunderdevelopmentthatmakesuseof6lowpanandprovidesadditionalagreementsforindustrialcontrolapplications[citationneeded].ISA100isscheduledforcompletionin2009.ZigBee,WirelessHART,and6lowpan/ISA100allarebasedonthesameunderlyingradiostandard:

IEEE802.15.4-2006.

Hardware

Mainarticle:

sensornode

Themainchallengeistoproducelowcostandtinysensornodes.Withrespecttotheseobjectives,currentsensornodesaremainlyprototypes.MiniaturizationandlowcostareunderstoodtofollowfromrecentandfutureprogressinthefieldsofMEMSandNEMS.Someoftheexistingsensornodesaregivenbelow.Someofthenodesarestillinresearchstage.

Anoverviewofcommonlyusedsensornetworkplatforms,components,technologyandrelatedtopicsisavailableintheSNM-SensorNetworkMuseumtm.

Software

EnergyisthescarcestresourceofWSNnodes,anditdeterminesthelifetimeofWSNs.WSNsaremeanttobedeployedinlargenumbersinvariousenvironments,includingremoteandhostileregions,withad-hoccommunicationsaskey.Forthisreason,algorithmsandprotocolsneedtoaddressthefollowingissues:

∙Lifetimemaximization

∙Robustnessandfaulttolerance

∙Self-configuration

Someofthe"hot"topicsinWSNsoftwareresearchare:

∙Security

∙Mobility（whensensornodesorbasestationsaremoving）

∙Middleware:

thedesignofmiddle-levelprimitivesbetweenthesoftwareandthehardware

Operatingsystems

Operatingsystemsforwirelesssensornetworknodesaretypicallylesscomplexthangeneral-purposeoperatingsystemsbothbecauseofthespecialrequirementsofsensornetworkapplicationsandbecauseoftheresourceconstraintsinsensornetworkhardwareplatforms.Forexample,sensornetworkapplicationsareusuallynotinteractiveinthesamewayasapplicationsforPCs.Becauseofthis,theoperatingsystemdoesnotneedtoincludesupportforuserinterfaces.Furthermore,theresourceconstraintsintermsofmemoryandmemorymappinghardwaresupportmakemechanismssuchasvirtualmemoryeitherunnecessaryorimpossibletoimplement.

WirelesssensornetworkhardwareisnotdifferentfromtraditionalembeddedsystemsanditisthereforepossibletouseembeddedoperatingsystemssuchaseCosoruC/OSforsensornetworks.However,suchoperatingsystemsareoftendesignedwithreal-timeproperties.Unliketraditionalembeddedoperatingsystems,however,operatingsystemsspecificallytargetingsensornetworksoftendonothavereal-timesupport.

TinyOS[8]isperhapsthefirst[citationneeded]operatingsystemspecificallydesignedforwirelesssensornetworks.Unlikemostotheroperatingsystems,TinyOSisbasedonanevent-drivenprogrammingmodelinsteadofmultithreading.TinyOSprogramsarecomposedintoeventhandlersandtaskswithruntocompletion-semantics.Whenanexternaleventoccurs,suchasanincomingdatapacketorasensorreading,TinyOScallstheappropriateeventhandlertohandletheevent.EventhandlerscanposttasksthatarescheduledbytheTinyOSkernelsometimelater.BoththeTinyOSsystemandprogramswrittenforTinyOSarewritteninaspecialprogramminglanguagecallednesCwhichisanextensiontotheCprogramminglanguage.NesCisdesignedtodetectraceconditionsbetweentasksandeventhandlers.

TherearealsooperatingsystemsthatallowprogramminginC.ExamplesofsuchoperatingsystemsincludeContiki,[9]MANTIS,[10]BTnut,[11]SOS[12]andNano-RK.[13]Contikiisdesignedtosupportloadingmodulesoverthenetworkandsupportsrun-timeloadingofstandardELFfiles.[14]TheContikikernelisevent-dr