Location-aided routing (LAR) in mobile ad hoc networks

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WirelessNetworks6(2000)307–321307

Location-AidedRouting(LAR)inmobileadhocnetworks∗

Young-BaeKoandNitinH.Vaidya

DepartmentofComputerScience,TexasA&MUniversity,CollegeStation,TX77843-3112,USA

Amobileadhocnetworkconsistsofwirelesshoststhatmaymoveoften.Movementofhostsresultsinachangeinroutes,requiringsomemechanismfordeterminingnewroutes.Severalroutingprotocolshavealreadybeenproposedforadhocnetworks.Thispapersuggestsanapproachtoutilizelocationinformation(forinstance,obtainedusingtheglobalpositioningsystem)toimproveperformanceofroutingprotocolsforadhocnetworks.Byusinglocationinformation,theproposedLocation-AidedRouting(LAR)protocolslimitthesearchforanewroutetoasmaller“requestzone”oftheadhocnetwork.Thisresultsinasignificantreductioninthenumberofroutingmessages.Wepresenttwoalgorithmstodeterminetherequestzone,andalsosuggestpotentialoptimizationstoouralgorithms.

1.Introduction

Mobileadhocnetworksconsistofwirelessmobilehosts

thatcommunicatewitheachother,intheabsenceofa

fixedinfrastructure.1RoutesbetweentwohostsinaMo-

bileAdhocNETwork(MANET)mayconsistofhops

throughotherhostsinthenetwork[7].Hostmobilitycan

causefrequentunpredictabletopologychanges.Therefore,

thetaskoffindingandmaintainingroutesinMANETis

nontrivial.Manyprotocolshavebeenproposedformo-

bileadhocnetworks,withthegoalofachievingefficient

routing[6,9,11,13,16,18–20,23,28,30,31,33,35].Theseal-

gorithmsdifferintheapproachusedforsearchinga

newrouteand/ormodifyingaknownroute,whenhosts

move.

Inthispaper,wesuggestanapproachtodecreaseover-

headofroutediscoverybyutilizinglocationinformation

formobilehosts.Suchlocationinformationmaybeob-

tainedusingtheglobalpositioningsystem(GPS)[10,29].

Wedemonstratehowlocationinformationmaybeused

bymeansoftwoLocation-AidedRouting(LAR)proto-

cols[19,20,22]forroutediscovery.TheLARprotocolsuse

locationinformation(whichmaybeoutofdate,bythetime

itisused)toreducethesearchspaceforadesiredroute.

Limitingthesearchspaceresultsinfewerroutediscovery

messages.

Thispaperisorganizedasfollows.Section2discusses

somerelatedwork.Insection3,wedescribeproposed

approachforusinglocationinformationforroutediscov-

eryinMANET.Performanceevaluationofourprotocols

ispresentedinsection4,andseveraloptimizationstoour

basicapproacharedescribedinsection5.Finally,section6

presentsconclusions.

∗ResearchreportedissupportedinpartbyTexasAdvancedTechnologyProgramgrants010115-248and009741-052-C,andNationalScienceFoundationgrantCDA-9529442.1Wewillusethetermshostandnodeinterchangeably.2.Relatedwork

Designofroutingprotocolsisacrucialprobleminmo-

bileadhocnetworks[5,32],andseveralroutingalgorithms

havebeendeveloped(e.g.,[6,9,11,13,16,18–20,23,28,30,

31,33,35]).Onedesirablequalitativepropertyofarouting

protocolisthatitshouldadapttothetrafficpatterns[7].

JohnsonandMaltz[17,18]pointoutthatconventionalrout-

ingprotocolsareinsufficientforadhocnetworks,sincethe

amountofroutingrelatedtrafficmaywastealargepor-

tionofthewirelessbandwidth,especiallyforprotocolsthat

useperiodicupdatesofroutingtables.Theyproposedus-

ingDynamicSourceRouting(DSR),whichisbasedon

on-demandroutediscovery.Anumberofprotocolopti-

mizationsarealsoproposedtoreducetheroutediscov-

eryoverhead.PerkinsandRoyer[31]presenttheAODV

(AdhocOndemandDistanceVectorrouting)protocolthat

alsousesademand-drivenrouteestablishmentprocedure.

TORA(Temporally-OrderedRoutingAlgorithm)[27,28]is

designedtominimizereactiontotopologicalchangesby

localizingrouting-relatedmessagestoasmallsetofnodes

nearthechange.HassandPearlman[13]attempttocom-

bineproactiveandreactiveapproachesintheZoneRout-

ingProtocol(ZRP),byinitiatingroutediscoveryphaseon-

demand,butlimitingthescopeoftheproactiveprocedure

onlytotheinitiator’slocalneighborhood.Recentpapers

presentcomparativeperformanceevaluationofseveralrout-

ingprotocols[4,8].

ThepreviousMANETroutingalgorithmsdonottake

intoaccountthephysicallocationofadestinationnode.In

thispaper,weproposetwoalgorithmstoreduceroutedis-

coveryoverheadusinglocationinformation.Similarideas

havebeenappliedtodevelopselectivepagingforcellu-

larPCS(PersonalCommunicationService)networks[1].

Inselectivepaging,thesystempagesaselectedsubsetof

cellsclosetothelastreportedlocationofamobilehost.

Thisallowsthelocationtrackingcosttobedecreased.We

proposeandevaluateananalogousapproachforrouting

inMANET.InasurveyofpotentialapplicationsofGPS,

©J.C.BaltzerAG,SciencePublishers308Y.-B.Ko,N.H.Vaidya/Location-AidedRouting(LAR)inmobileadhocnetworks

DommetyandJain[10]brieflysuggestuseoflocationinfor-

mationinadhocnetworks,thoughtheydonotelaborateon

howtheinformationmaybeused.Otherresearchershave

alsosuggestedthatlocationinformationshouldbeusedto

improve(qualitativelyorquantitatively)performanceofa

mobilecomputingsystem[34,36].Metricom’sRicochetis

apacketradiosystemusinglocationinformationforthe

routingpurpose[24].TheMetricomnetworkinfrastructure

consistsoffixedbasestationswhosepreciselocationisde-

terminedusingaGPSreceiveratthetimeofinstallation.

Metricomusesageographicallybasedroutingschemeto