Packet Loss in Mobile Ad Hoc Networks(7)

Abstract — We investigate packet loss in mobile ad hoc networks via simulation. Ad-hoc on-demand distance vector (AODV) and destination-sequenced distance vector (DSDV) are chosen as representatives of the on-demand and proactive routing protocols respect

Fig.5.Packetlossdistributionforindividualhosts

anIDatthebeginningofthesimulationwithoutanybias).Thecurves uctuateoverthetime,likepulseswithrandompeaks.Fromthis gure,packetlossesatthesethreehostsseemtobeindependent.Theyhavedifferenthighestvalues(230,200,and150)anddifferentnumberofpeaks.Thepeaksarereachedatdifferenttimeslots.Theresulthelpsindimensioningpacketbufferforadhocnetworkroutingprotocols.Forexample,fromtheburstingpatternofpacketlossshowninthe gure,wecanconcludethatalargerbufferwillnothelpmuchinreducingpacketlossifthesizeis xed,becausepacketlossvariesalotfromonetimetothenext.Thisconclusionissupportedbytheexperimentconductedin[15],whichshowsthatincreasingthebuffersizefrom5-packetto64-packetdoesnotincreasethethroughputforDSDV.

Figure6showsthedistributionsofnetwork-widetotalpacketloss,congestion-relatedloss,andmobility-relatedloss.Everykindofpacketloss uctuatesoverthesimulationtime.Allexhibitburstingbehaviors.Themaximumnumbersfortotalpacketloss,congestion-relatedpacketloss,andmobility-relatedpacketlossareabout1000,400,and230respectively.

PacketlosscannotbedescribedbythetraditionalPoisson-basedmodel,whichiswidelyusedinnetworktraf cmodelling.ThePoissonframeworkcannotcapturetheburstinesspresentedin gure5and6.Wetend

to

7

work-widepacketlossdistribution

believethatpacketlossisself-similar.Figure6aand6bexhibitafractal-likepattern.Thispatternisillustratedin gure7.Figure7aand7cshowthenumbersoftotalpacketlossandcongestion-relatedpacketlosssampledevery100seconds,parisonsbetween7aand7b,7cand7dindicatesomeextentofsimilarity.

Weareworkingongettingalargetraf ctraces(morethan100,000seconds)sothattheobservationscalingrangecanspanmorethan3decades.Wehopetoobtainconvincingevidenceoffractal-likescalingforpacketlossinmobileadhocnetworks.

VI.CONCLUSIONS

AND

FUTUREWORK

Toourknowledge,thisworkisthe rstattempttowardsacomprehensiveinvestigationofpacketlossinmobileadhocnetworks.Thecontributionsofcongestionandmobilitytothetotalpacketlosshavebeenexamined.Theimpactsofhostmobility,communicationrequest,traf cload,traf ctype,andAODVandDSDVroutingprotocolshavebeenstudied.Thesimulationresultsin-dicate:

MobilityisthedominantcauseforAODV,whichisresponsibleformorethan60%oftotalpacketloss.ForDSDV,morethan50%oftotalpacketlossiscongestion-related.