Energy conservation in wireless sensor networks -

Energyconservationinwirelesssensornetworks:AsurveyGiuseppeAnastasia,MarcoContib,*,MarioDiFrancescoa,*,AndreaPassarellabaDepartmentofInformationEngineering,UniversityofPisa,viaDiotisalvi1,56122Pisa,ItalybInstituteforInformaticsandTelematics(IIT),NationalResearchCouncil(CNR),viaG.Moruzzi1,56124Pisa,ItalyarticleinfoArticlehistory:Received26February2008Accepted30June2008AvailableonlinexxxxKeywords:WirelesssensornetworksSurveyEnergyefficiencyPowermanagementabstractInthelastyears,wirelesssensornetworks(WSNs)havegainedincreasingattentionfromboththeresearchcommunityandactualusers.Assensornodesaregenerallybattery-pow-ereddevices,thecriticalaspectstofaceconcernhowtoreducetheenergyconsumptionofnodes,sothatthenetworklifetimecanbeextendedtoreasonabletimes.Inthispaperwefirstbreakdowntheenergyconsumptionforthecomponentsofatypicalsensornode,anddiscussthemaindirectionstoenergyconservationinWSNs.Then,wepresentasystematicandcomprehensivetaxonomyoftheenergyconservationschemes,whicharesubse-quentlydiscussedindepth.Specialattentionhasbeendevotedtopromisingsolutionswhichhavenotyetobtainedawideattentionintheliterature,suchastechniquesforenergyefficientdataacquisition.FinallyweconcludethepaperwithinsightsforresearchdirectionsaboutenergyconservationinWSNs.2008ElsevierB.V.Allrightsreserved.1.IntroductionAwirelesssensornetworkconsistsofsensornodesde-ployedoverageographicalareaformonitoringphysicalphenomenaliketemperature,humidity,vibrations,seismicevents,andsoon[5].Typically,asensornodeisatinyde-vicethatincludesthreebasiccomponents:asensingsub-systemfordataacquisitionfromthephysicalsurroundingenvironment,aprocessingsubsystemforlocaldataprocessingandstorage,andawirelesscommunica-tionsubsystemfordatatransmission.Inaddition,apowersourcesuppliestheenergyneededbythedevicetoper-formtheprogrammedtask.Thispowersourceoftencon-sistsofabatterywithalimitedenergybudget.Inaddition,itcouldbeimpossibleorinconvenienttore-chargethebattery,becausenodesmaybedeployedinahostileorunpracticalenvironment.Ontheotherhand,thesensornetworkshouldhavealifetimelongenoughtofulfilltheapplicationrequirements.Inmanycasesalife-timeintheorderofseveralmonths,orevenyears,mayberequired.Therefore,thecrucialquestionis:‘‘howtoprolongthenetworklifetimetosuchalongtime?”Insomecasesitispossibletoscavengeenergyfromtheexternalenvironment[59](e.g.,byusingsolarcellsaspowersource).However,externalpowersupplysourcesoftenexhibitanon-continuousbehaviorsothatanenergybuffer(abattery)isneededaswell.Inanycase,energyisaverycriticalresourceandmustbeusedverysparingly.Therefore,energyconservationisakeyissueinthedesignofsystemsbasedonwirelesssensornetworks.InthispaperwewillrefermainlytothesensornetworkmodeldepictedinFig.1andconsistingofonesinknode(orbasestation)anda(large)numberofsensornodesde-ployedoveralargegeographicarea(sensingfield).Dataaretransferredfromsensornodestothesinkthroughamulti-hopcommunicationparadigm[5].Wewillconsiderfirstthecaseinwhichboththesinkandthesensornodesarestatic(staticsensornetwork).Then,wewillalsodis-cussenergyconservationschemesforsensornetworkswithmobileelementsinSection6,inwhichasparsesen-sornetworkarchitecture–wherecontinuousend-to-endpathsbetweensensornodesandthesinkmightnotbeavailable–willbeaccountedaswell.1570-8705/$-seefrontmatter2008ElsevierB.V.Allrightsreserved.doi:10.1016/j.adhoc.2008.06.003*Correspondingauthors.Tel.:[phone];fax:[phone](M.Conti).E-mailaddresses:[e-mail](G.Anastasi),[e-mail](M.Conti),[e-mail](M.DiFrancesco),[e-mail](A.Passarella).AdHocNetworksxxx(2008)xxx–xxxContentslistsavailableatScienceDirectAdHocNetworksjournalhomepage::G.Anastasietal.,Energyconservationinwirelesssensornetworks:Asurvey,AdHocNetw.(2008),doi:10.1016/j.adhoc.2008.06.003Experimentalmeasurementshaveshownthatgenerallydatatransmissionisveryexpensiveintermsofenergycon-sumption,whiledataprocessingconsumessignificantlyless[108].Theenergycostoftransmittingasinglebitofinformationisapproximatelythesameasthatneededforprocessingathousandoperationsinatypicalsensornode[103].Theenergyconsumptionofthesensingsubsystemdependsonthespecificsensortype.Inmanycasesitisnegligiblewithrespecttotheenergyconsumedbythepro-cessingand,aboveall,thecommunicationsubsystems.Inothercases,theenergyexpenditurefordatasensingmaybecomparableto,orevengreaterthan,theenergyneededfordatatransmission.Ingeneral,energy-savingtechniquesfocusontwosubsystems:thenetworkingsubsystem(i.e.,energymanagementistakenintoaccountintheopera-tionsofeachsinglenode,aswellasinthedesignofnet-workingprotocols),andthesensingsubsystem(i.e.,techniquesareusedtoreducetheamountorfrequencyofenergy-expensivesamples).Thelifetimeofasensornetworkcanbeextendedbyjointlyapplyingdifferenttechniques[10].Forexample,en-ergyefficientprotocolsareaimedatminimizingtheenergyconsumptionduringnetworkactivities.However,alargeamountofenergyisconsumedbynodecomponents(CPU,radio,etc.)eveniftheyareidle.Powermanagementsc