MANETs稳定性路由的移动自适应策略研究Word文档格式.docx
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MANETs稳定性路由的移动自适应策略研究Word文档格式.docx
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AbstractThemotionofnodeleadstothereal-timechangesofthetopologyofmobileadhocnetworks,andincreasesthecomplexityofrouting.Theexistingstability-basedroutingalgorithmsalwaysfocusonhowtoestablishastableroute,whichhaveignoredtheadaptabilityoftheestablishedstableroutetothemotionsofnodes.Aimingatthisproblem,amobility-adaptivestrategyforstability-basedroutingisproposedfirstly.Thisstrategymainlycontainsthreekeytechnologies;
thebidirectionalevaluationofthestabilityparameterduringroutediscoveryprocess;
theasynchronousinformationandthelinkstabilityupdatewhennodechangesitsmotionstate;
Andthemulti-pathroutemaintenancebasedonlinkstability.Thenbasedonthemobility-adaptivestrategy,amobility-adaptivestability-basedonlinkroutingalgorithmisalsoproposed.Thesimulationresultsshowthattheproposedmobility-adaptivestrategyandstability-basedroutingalgorithmcanimprovetheroutingperformancesfurther,andadapttothedynamicmobileadhocnetworkenvironmentbetter.
Keywords:
Mobileadhocnetwork;
Stability-basedrouting;
Mobility-adaptive
1Introduction
MobileAdHocNetworksisthewirelessnetworkconsistsofmobileself-organizingnodes.Datacommunicationinthenetworkisachievedthroughthemulti-hoppathmadeupofasetofnodes.However,mobilityofnodeswillcausetheinterruptionoftransmissionpath,leadingtothedeclineofnetworkcommunicationperformance.
Tomeettherequirementsofapplication,researchersraisedalotofMANETsroutingalgorithmswhichsupportqualityofservice.Stability-orientedroutingalgorithmisimportantamongthem,aimingatimprovethestabilityandconstancyintheprocessofdatatransmission,reducingtheeffectonroutingcausedbynodemobility.InNSR,nodeswhoseneighborschangelesthasbetterstability,soalgorithmchoosestablenodestobuildroutesaccordingtothehistoricalinformationbetweenneighbornodes.Inthisalgorithm,allnodesinthenetworksetexchangecycleaccordingtothemovingspeed,throughthecycleexchange,eachnodecouldmaintainthenewestlistofneighborsandassessthestability,andrecordthestabilityofpathintheforwardprocessofRoutingRequest,destinationnodewillchoosethebestpathaccordingthestabilityofRREQrecords.Inthecaseofpathdisruption,NSRwillnotifythesourcenodetorebuildtheroute.[3]ProposedastableroutingalgorithminMANET.TheauthorutilizestheDopplershiftingcausedbymotionbetweennodestoachieveaDVvaluetoassessthestabilityoflinkaccordingtotherelationshipofrelativemotionbetweennodes.Inthisalgorithm,nodesneedtoexchangepacketsperiodicallytoobtaintheDopplerfrequencyshift;
routewillsearchthepathwithbetterstabilityasthealternativepathaccordingtodefinitionoflinkstability,destinationnodechoosethebestalternativepathtoresponse.,however,routemaintainstrategyisnotdesignedinthisalgorithm.In[5],authorobtainedthebestlinkwithincommunicationrangeofnodesbyderivingthelinkeffectivemodel,andachievedtheroutewithbetterstabilitybymodifyingtheforwardingrulesofRREQbasedonAODV,adoptedthemaintainstrategyofAODVinthecaseofroutinginterruption.[8]alsoobtainedtheaveragemaintaintimebyevaluatingtocontroltheforwardingofRREQpacketandbuildthestableroutebasedonAODV,utilizethelocalroutetomaintainorrebuildtheroutebysourcenodeafteraninterruption.[9-10]usetheeffectivelinktimeastheparameteroflinkstabilitytoestablishastableroute.In[9]routeestablishmentandmaintenanceofoperationisbasicallythesameasDSR[15],butchoosetheroutethroughtheLET、numberoflinkinterruptionandweighedaveragevalueofhops;
In[10],routeestablishmentisthesameasDSR,however,routerepairmechanismbasedonDSRwillbeimplementedifreplaceablerouteexistsintheprocessofroutemaintenance,orlocalrepairmechanismwillbeusedwithoutalternativeroute.
Tosummarizetheexistingstability-orientedroutingalgorithm,thereexistthreemainproblems:
First,calculationparametersandmethodselectedtoassessthestabilityofroutewillaffecttheaccuracyofevaluationresults.Forexample,[9]useGPSdatatoobtainLETand[7]usesignalstrengthtomeasurethestability.Secondly,inordertoassesstheparametersofroutestability,somealgorithmsneedtoexchangenodeinformationperiodically,suchas[2][7][8].Thisraisetwoproblem:
(1)determinationofexchangeperiod.ifcycleislong,itcannotreflectthenodemobilityintime;
ifthecycleisshort,networkoverheadwillbeincreased.
(2)networkresourceconsumption,increasetheprobabilityofpacketcollision;
Finally,lacksofnodeadaptabilityinestablishingastableroutewillleadtothelagofthisrouteinterruption.Forexample,alloftheroutingalgorithmsmentionedabovehavethisproblem.
Thispaperproposedamobileadaptivestrategyaccordingtotheproblemaboveofstability-orientedroutingalgorithms,anddesignamobileadaptiveroutingalgorithmbasedonthischaracteristic.Themainworkincludes:
(1)two-wayevaluationintheprocessofroutebuilding;
(2)asynchronousnoticeofthemobilityofnodesandLETupdating;
(3)definetheLETanddecidethemaintainstrategybasedonthezone.(4)analyzetheMASRandeffectofthemobileadaptivestrategyonroutingperformance.
2.CalculationofLET
WiththedevelopmentofGPS,mobileAdHocnetworknodeequippedwithGPSisnolongeranlongereconomicburden.NodescouldobtaintheaccuratelocationandmovementinformationwithGPS,[11]proposedthecalculationwayofLETbetweentwonodes.AsisshowninFigure1,wesetrasthetransmissionradiusoftwonodes,(vi,
i)asthetransmissionspeedand(vj,
)asthemovement,currentcoordinateas(xi,yi)and(xj,yj),andthecalculationformulaofLETisshownasfollows:
(1)
Figure1LETParameters
here
3.MobileAdaptiveTechnique
Mobileadaptivestrategyproposedinthispaperincludethreecriticaltechniques:
twowayevaluationofLET,asynchronousmobilenoticeandLETupdating,multi-pathmaintenancebasedoncriticalLETzone.
3.1TwoWayEvaluationofLET
IntheexistingalgorithmswhichutilizetheLETtobuildthestableroute,mobilityinformationofnodesisforwardingthroughRREQ,eachreceivernodecalculatetheLETofupstream,andrecordtheminimumLETofthepath.Inthediscussionofthispaper,weusetheminimumLETofthepathastheparameterstoevaluatethepathdurationtime,knownasrouteeffectivetime.DestinationnodechoosethepathwithmaxRETtoresponsetoRREQaftercomparinganumberofRET.RREQisonlyforwardedbyhopslongtheoppositepath,andestablisharelativelystableroutewhenreachthesourcenode.
However,eachnodeneedstomonitortheLETindownstreamlinktomakethemovementofadaptivenodestable,soweproposedatwo-wayevaluationofLETinroutingestablishmentbasedonthedirectionofRREQandRREP,thisstrategyincludestwoprocess:
EvaluationofforwardLETandreverseLET.ForwardLETevaluationmeanstoselecttheoptimalpathtoresponseRREPaccordingtotheminimumLET;
ReverseLETevaluationmeanstomakesurethatnodesfromtheselectedpathcouldobtaintheLETfromdownstream.
3.1.1LETforwardevaluation
AsisshowninFigure2,sourcenodebroadcastsRREQ,theRREQrecordthemobileinformationofnodeS,pathRETandpathinformation.NodeAobtainthemobileinformationofSafterreceivingtheRREQ,andcalculatetheupstreamLETaccordingthe
(1),andupdatetheRETzoneandmobileinformationzoneofRREQ,andcontinuetobroadcasttheupdatedRREQ.otherintermediatenoderepeattheoperationafterreceivetheRREQ.whenthedestinationnodeDreceivetheRREQ,itcalculatetheLETfromupstreamandupdatetheRET,andcachetheRREQ.
Figure2SamplePath
3.1.2LETReverseEvaluation
Figure2shows,destinationnodeDresponseRREP,RREPrecordthemobileinformationandcompletepathinformation{S->
A->
B->
C->
D}ofD,afternodeCreceivetheRREO,calculatetheLEToflink4accordingto
(1),andthensavethemobileinformationandLEToflink4fromdownstream,updatethemobileinformationzoneinRREPatlast,andforwardaccordingtopathinformation,otherforwardingnodesrepeatthesameoperationafterreceivingtheRREP,whensourcenodeSreceivetheRREP,calculateandsavetheLEToflink1fromdownstream,andachievetheoptimalavailablepath.
3.2AsynchronousMobileNoticeandLETUpdates
Intheexistingstability-orientedroutingalgorithms,researchersfocusonhowtobuildthestablerouteandneglecttheinfluenceofmobilityofnodesonroutestability,orutilizethetwo-wayinformationexchangetoobtainneighborsinformation.Stableroutecannotadapttothemobilityofnodesintheformerway,resultinginthedecreaseofroutingefficiency,andinformationexchangeneedtobesynchronizedinthesecondway,butit’sdifficulttodeterminetheexchangecycleifnodesmoveindifferentspeed.
Therefore,weproposedaasynchronousmobilenoticeLETupdatingstrategybasedonthefeaturesthatnodescouldobtainmobilestateofitselfthroughGPS.Thebasicideaofthismechanismis:
changesofnodesmobilestatustriggeritselftobroadcastnoticetoneighbors,andifthenodeisacompositionofaroute,itneedtobecalculatedagain、updatelinkLETofdownstream.Neighborbroadcastnoticerecordthelatestmobileinformationofnodes,afterneighborreceiveanotice,itwillre-evaluate
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- MANETs 稳定性 路由 移动 自适应 策略 研究