analyzing discovery latency in mobile networks
TRANSCRIPT
Graduate Theses, Dissertations, and Problem Reports
2017
Analyzing discovery latency in mobile networks Analyzing discovery latency in mobile networks
Saud Alramzi
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ANALYZINGDISCOVERYLATENCYINMOBILENETWORKS
SaudAlramzi
ProblemReportsubmittedtothe
BenjaminM.StatlerCollegeofEngineeringandMineralResources
atWestVirginiaUniversity
inpartialfulfillmentoftherequirementsforthedegreeof
MastersofScience
in
ElectricalEngineering
VinodKulathumani,Ph.D,Chair
XinLi,Ph.D
YanfangYe,Ph.D
LaneDepartmentofComputerScienceandElectricalEngineering
Morgantown,WestVirginia
2017
Keywords:neighbordiscovery,discoverylatency,disco,manet
Copyright2017SaudAlramzi
ii
ABSTRACT
AnalyzingDiscoveryLatencyinMobileNetworks
SaudAlramzi
Duty cycle is important in wireless sensor andmobile ad-hoc networks (MANETs) to
extendtheirlifetime.Dutycyclinginwirelessnetworksletsthenodeswakeupwithinfrequent
fixedperiods,basedonpre-determinedparameters.Ontheotherhand,neighbordiscoveryis
theprocessbywhichnodeslearnabouttheneighbors.Nodescanuseradiocommunicationsto
discover other neighbors. Timely, neighbor discovery is crucial for routing. But, neighbor
discovery becomes more challenging in energy-constrained, mobile environment with duty
cyclednodeswhereanodemaynotknowwhetheranyneighborsarepresent,andwhatduty
cyclethoseneighborsmightoperateat.
Discoisanasynchronousneighbordiscoveryandrendezvousprotocolthatallowstwoor
more nodes to operate their radios at low duty cycles (1-2%). Disco obtains discovery and
communication during infrequent, opportunistic encounters without requiring a global
synchronizationinformation.Disconodespickapairofdissimilarprimenumbersuchthatthe
sumoftheirreciprocalisequaltothedesireddutycycle.Aglobalcounterincrementswithafixed
period.Ifoneofthenode’sprimenumbersisdivisiblebythecounter,thenodewillturnonits
radioforoneperiod.Thisprotocolensuresthattwonodeshavesomeoverlappingradioon-time
withintheboundaryoftheperiod,anddiscovereachotherdespiteoftheindependentsetof
dutycycle.
Inthisreport,weseektounderstandhowDiscoperformsinmobilenetworks.Weanalyze
theimpactofdifferentdutycycles,mobilityspeedsandnetworksizesondiscovery latency in
extrememobilenetworks.WealsoscrutinizehowfastDiscodiscoversthatnodeshavemoved
outoftheirneighborhood.WeuseNS3tosimulateDiscowithdifferent,dutycycles,mobility
speeds,andnetworksizes.
iii
Acknowledgements
First,IwouldwanttothankmycommitteechairandadvisorDr.VinodK.Kulathumanifor
constantsupport,providingmeanopportunitytoworkwithhimandguidingmethroughoutmy
Master’sprogram.Also,IwouldliketoextendmywarmacknowledgmentstobothDr.XinLiand
Dr. Yanfang Ye for taking their courses in Image Processing and Advanced Data Mining
respectively,andforbeingpartofmycommittee.
Inaddition,IwouldespeciallyliketothankmyfamilymembersandmylovelywifeMrs.
DalalKamal,forhergenerousandunfailingsupportandcontinuousencouragementthroughout
myyearsofstudyandthroughtheprocessofresearchingandwritingthisdissertation.
Furthermore, Iwould liketothankallmyfriendsfortheirsuggestionsandhelpingme
overcomeallthetoughtimesinMorgantown,especiallyMr.MrwanBenIdris,andMs.Sowmya
Devaraja.
Last but not least, I would want to thank all of the faculty members in the Lane
DepartmentofComputerScienceandElectricalEngineeringforsharingexpertise,andsincere
andvaluableguidanceandencouragementextendtome.
iv
TableofContents
Chapter1Introduction...........................................................................................1
1.1 Overview............................................................................................................................1
1.2 SummaryofContributions.................................................................................................4
1.3 Outline................................................................................................................................5
Chapter2ReviewofPriorwork..............................................................................6
2.1 BirthdayProtocol...............................................................................................................6
2.2 Quorum-basedProtocol.....................................................................................................6
2.3 U-ConnectProtocol............................................................................................................6
2.4 DiscoProtocol....................................................................................................................6
Chapter3DesignandImplementations.................................................................11
3.1 Design...............................................................................................................................11
3.2 ExperimentalSetup..........................................................................................................13
Chapter4Results.................................................................................................18
4.1 DiscoveryLatency.............................................................................................................18
4.1.1 DifferentDutyCycles............................................................................................18
4.1.2 DifferentMobilitySpeeds.....................................................................................18
4.2 FailingLatency..................................................................................................................20
4.2.1 DifferentDutyCycles............................................................................................20
4.2.2 DifferentMobilitySpeeds.....................................................................................23
Chapter5FutureWorkandConclusion................................................................28
5.1 FutureWork.....................................................................................................................18
5.2 Conclusion........................................................................................................................18
References................................................................................................................29
v
ListofFigures
Figure4.1 TheDiscoveryLatencyfor50nodesandthemobilityofnodesis2-4m/s.............3
Figure4.2 TheDiscoveryLatencyfor50nodesandthemobilityofnodesis3-7m/s.............7
Figure4.3 TheDiscoveryLatencyfor50nodesandthemobilityofnodesis7-15m/s...........8
Figure4.4 TheDiscoveryLatencyfor50nodesandthemobilityofnodesis15-25m/s.......15
Figure4.5 TheDiscoveryLatencyfor100nodesandthemobilityofnodesis2-4m/s.........18
Figure4.6 TheDiscoveryLatencyfor100nodesandthemobilityofnodesis3-7m/s.........19
Figure4.7 TheDiscoveryLatencyfor100nodesandthemobilityofnodesis7-15m/s.......23
Figure4.8 TheDiscoveryLatencyfor100nodesandthemobilityofnodesis15-25m/s.....24
Figure4.9 TheDiscoveryLatencyfor50nodesandnodes’dutycycleis1%........................25
Figure4.10 TheDiscoveryLatencyfor50nodesandnodes’dutycycleis10%......................26
Figure4.11 TheDiscoveryLatencyfor50nodesandnodes’dutycycleis20%......................27
Figure4.12TheDiscoveryLatencyfor50nodesandnodes’dutycycleis30%......................28
Figure4.13 TheDiscoveryLatencyfor50nodesandnodes’dutycycleis50%........................7
Figure4.14 TheDiscoveryLatencyfor50nodesandnodes’dutycycleis100%......................8
Figure4.15 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis1%......................15
Figure4.16 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis10%....................18
Figure4.17 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis20%....................19
Figure4.18 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis30%....................23
Figure4.19 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis50%....................24
Figure4.20 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis100%..................25
Figure4.21 TheFailingLatencyfor50nodesandthemobilityofnodesis2-4m/s................26
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Figure4.22 TheFailingLatencyfor50nodesandthemobilityofnodesis3-7m/s................27
Figure4.23TheFailingLatencyfor50nodesandthemobilityofnodesis7-15m/s..............28
Figure4.24 TheFailingLatencyfor50nodesandthemobilityofnodesis15-25m/s..............3
Figure4.25 TheFailingLatencyfor100nodesandthemobilityofnodesis2-4m/s................7
Figure4.26 TheFailingLatencyfor100nodesandthemobilityofnodesis3-7m/s................8
Figure4.27 TheFailingLatencyfor100nodesandthemobilityofnodesis7-15m/s............15
Figure4.28 TheFailingLatencyfor100nodesandthemobilityofnodesis15-25m/s..........18
Figure4.29 TheFailingLatencyfor50nodesandnodes’dutycycleis1%............................19
Figure4.30 TheFailingLatencyfor50nodesandnodes’dutycycleis10%...........................23
Figure4.31 TheFailingLatencyfor50nodesandnodes’dutycycleis20%...........................24
Figure4.32 TheFailingLatencyfor50nodesandnodes’dutycycleis30%...........................25
Figure4.33 TheFailingLatencyfor50nodesandnodes’dutycycleis50%............................3
Figure4.34 TheFailingLatencyfor50nodesandnodes’dutycycleis100%..........................7
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ListofTables
Table3.1Examplesforapairofprimenumbersfor1%,10%,and20%dutycycle.................2
Table3.2Threedifferentcaseswhentwonodeshavea1%dutycycle.................................10
Table3.3Theexperimentparameters....................................................................................10
Table4.1Percentagesofundiscoveredneighbors’nodesforFigure4.19network...............16
1
Chapter1
Introduction
1.1 OverviewDutycycleisimportantforwirelesssensorandmobilead-hocnetworks(MANETs).The
devicesintheMANETaretermedasnodes.Node’sdutycycledeterminesitsactivetime.A60%
dutycyclemeansthenodeisactivefor60%ofthetimebutofffor40%ofthetime.Byvarying
thedutycycleratio,wecanletthenodewakeupwithinfrequentfixedperiods.
Neighbordiscoveryinmobilenetworksistheprocessinwhichnodeslearnabouttheir
neighbors.Neighbordiscovery isdivided intotwoparts, the firstpart iswhennodesdiscover
their neighbors. The second part is when nodes discover their neighbors are no longer in
communicationrange.Neighbordiscoveryhasprovenchallengingbecauseofchangingtopology
andnoinformationregardingthewake-upschedulesoftheneighbornodes.Tominimizeenergy
consumption,thenodesusuallyapplyduty-cyclingtotheirradios,whichmeanstheyrepeatedly
switchontheirradiosandsleep.Asuccessfuldiscoverycantakeplaceifandonlyifoneradio
listensonthechannelatthesamepoint intimeatwhichanotheronesendsapacket.Asthe
clocksofthesedevicesarecompletelyunsynchronized,thepointintimewhentwodevicesmeet
forthefirsttimeisrandom.
Minimizingdiscoverylatencytimesisvitalforthesuccessofroutingprotocolsinmobile
networks.Thisincludesdiscoveringnewneighborsanddiscoveringthattheexistingneighbors
havefailedbecauseofnodemobility.Thelatencytodiscovernewneighborsisdiscoverylatency,
while the latency to discover that nodes havemoved out of communication range is failing
latency.Bothlatencieshavetobesmalltoensurescalablerouting,asexplainedbytherepair
timescalingwall.
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The repair timescalingwall [8]occursbecauseasnetworksize increases, theaverage
durationthatapathremainsconnecteddecreases,whiletheaveragedurationtorepairapath
remains constant. When the average path connectivity interval falls below the path repair
interval,thescalingwall isreached.Ithasbeenshownthatthepathrepair interval isroughly
equaltothelinkfailureestimationdelayinthesystem.Thus,fasterlinkdiscoveryiscriticalfor
extendingthescalabilityofroutingprotocolsforMANETs.
Asynchronousnetworksrefertonodesthathaveindependentdutycycles,andhaveno
informationaboutothernodesinthenetwork.Whendesireddutycycleisassignedtothenodes,
itisverydifficulttoachieveneighbordiscovery. Operatingaradioatlowdutycycleandensuring
thediscoverytobefast,reliable,andpredicableoverarangeofcommunicationisachallenge.
Asynchronous duty cycles are advantageous as they reduce collisions. The various neighbor
discoveryprotocolsareBirthdayprotocol,Quorum-basedprotocol,discoandsoon.Theresults
ofBirthdayprotocolandQuorum-basedprotocolhaveproblemswithasynchronousneighbor
discovery.[2,6]
Discoisanasynchronousneighbordiscoveryprotocolthatallowstwoormorenodesto
operatetheirradiosatlowdutycycles,andyetstilldiscoverandcommunicatewithoneanother
duringinfrequentperiodswithoutrequiringanypriorsynchronizationinformation[4].Indisco,
nodespickapairofprimenumbersuchthatthesumoftheirreciprocalsisequaltothedesired
dutycycle.Eachnodeincrementsalocalcounterwithaglobally-fixedperiod.Ifanode’slocal
countervalue isdivisiblebyoneof itsprimenumbers,thenodewill turnon itsradioforone
period.
In [4], the cumulative distribution of discovery latencies for disco is compared with
BirthdayandQuorumprotocolsoperatingat5%dutycycle.It’sproventhatDiscoachievesbetter
neighbor discovery than these protocols. Disco protocol is a practical solution to the
asynchronousneighbordiscovery,andrendezvousproblemthatworksbyschedulingradiowake
timesatmultiplesofprimenumbers,whichensuresdeterministicpairwisediscoveryandmimic
thediscovery latencies.The relationshipbetween slot length,beacon rate,discovery latency,
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discovery rate, and duty cycle has been analyzed. The disco protocol has been validated for
limitednetworksizesanddutycycles.
Theobjectiveofthisworkistovalidatethediscoprotocolinmobilenetworks,
forlargenetworksizesundervarieddutycycles.
1.2 SummaryofContributionsInthiswork,in-depthanalysishasbeendoneontheconceptofDiscoprotocol.SinceDisco
protocolwasonlyvalidatedon limiteddutycyclesandsmallnetworkssizes, theresultswere
basedon:
• WeimplementedandverifiedthatDiscoensuresdiscoveryinmobilenetworks.
• WeanalyzedbothdiscoveryandfailinglatenciesinmobilenetworksusingDisco
protocolusingnetworksimulator,ns3fornetworksizes50,and100nodesunder
differentnodespeeds,dutycycles,anddensities.
• Wecomparebothdiscoveryandfailinglatenciesinnetworkswithfixedmobilityspeed
versusvariousdutycycles.
• Wecomparebothdiscoveryandfailinglatenciesinnetworkswithfixeddutycycle
versusvariousmobilityspeeds.
1.3 OutlineThe rest of our reportwill be organized as follows. In chapter 2,we discuss in detail
regarding the neighbor discovery and neighbor discovery protocols, in particular about disco
protocol.Wepresentthedesignaspectsofthediscoprotocolinchapter3.Inchapter4wehave
briefedtheimplementationdetailsformobilenetworks.Wehaveanalyzedneighbordiscovery
protocolformobilenetworksbypresentingthesimulationresultsobtainedbyns-3simulations
inchapter5.Inchapter6and7wepresentthefutureworkandconclusion.
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Chapter2
Background
Neighbordiscoveryhasbeenachallengeinbothsensorandwirelessnetworks.Inthese
networks,neighbordiscoveryandenergyefficiencyaresignificant.So,neighbordiscoveryisa
challenge inmobile networks. In this section, wewill discuss some of the existing neighbor
discoveryprotocolsandtheirconsequences.
The twoneighbordiscovery typesare synchronousandasynchronous. In synchronous
neighbordiscovery,nodesinthenetworkknowthewakeuppatternsoftheirneighbors.Onthe
other hand, in asynchronous neighbor discovery, nodes do not have any information on
neighbors’wake-upschedules[7].Inourwork,wewillexploremoreonasynchronousneighbor
discoveryprotocols.
2.1BirthdayProtocol“Birthday” protocol [2] proposed byMcGlynn and Borbash is a probabilistic protocol.
Birthdayprotocoluses random independent transmissions todiscoveradjacentnodes. In this
protocol,thenodeschoosetostayinastate(transmit,listenorenergysaving)foratimeslot.
Thus,thenodewhichwantstosharediscoverymessageshouldbeintransmitstateandnode
whichisintendedtoreceivethediscoverymessageshouldbelistenstate.Onlywhenthestates
overlapinthispattern,theneighborswillbesuccessfullydiscovered.Energysavingstateisan
idlestate.Althoughitisanefficientsaving-energyprotocolforstaticadhocnetworks,itdoesnot
providepredictablerendezvoustimesandexhibitsalongtailfordiscovery.Thisprotocolisnot
suitablefornetworkwithchangingtopology.
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2.2Quorum-basedProtocolQuorum-basedprotocol[6]proposedbyTsengetal.isapower-savingneighbordiscovery
protocolformulti-hopadhocnetwork.Inthisprotocol,acommondutycycleisusedbyallthe
nodes in the network. This ensures that nodes know the wake-up time of the node to
communicatewith.TheconceptoftheprotocolistoletnodessendbeaconsO(1/n)ofthebeacon
intervals.Thesequenceofbeaconintervalisdividedintosetsofcontinuous𝑛"where𝑛aglobal
parameterindicatingthedutycycle.
Ineachsetonintervals,the𝑛"intervalsarearrangedasa2-dimentional𝑛×𝑛arrayina
row-majormanner.Onthe𝑛×𝑛array,anodearbitrarilypicksonecolumnandonerowofentries
totransmitandreceive,respectively,atotalof2𝑛 − 1intervalsineachsetof𝑛"intervals.Since
𝑛isaglobalconstantparameter,allnodeshavethesamedutycycle,whichlimitstheflexibility
of theQuorumprotocol.Thus,Quorum-basedprotocol lacksasynchronousdutycycles in the
network.
2.3U-ConnectProtocolU-Connectprotocol[1],proposedbyKandhalu,Lakshmanan,andRajkumarisaneighbor
discoveryprotocol thatachievesneighbordiscoveryatminimalwithsavingenergycosts, ina
symmetric/asymmetricasynchronousduty-cycledneighbordiscovery.Thedesignisasfollows,
eachnodepicksaprimenumberpandstaysactivefor1everypslots,andnodeswilldiscover
oneanother.Theyalsoexcludethecaseifprimeis2.
2.4DiscoProtocolDiscoisanasynchronousneighbordiscoveryandrendezvousprotocolthatallowsnodes
discovereachotheratlowdutycycle[4].Discoensuresdeterministicpairwisediscoverywithout
requiringglobalcoordinationofdutycycles.
ThisapproachisadoptedfromSunZi’stwo-milleniaoldChineseRemainderTheoremand
ensuresdiscoveryinboundedtime,evenifnodesindependentlychoosetheirprimenumbers.
TheChineseRemainderTheoremrequiresco-primestoguaranteeasolutiontothesimultaneous
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congruencies[5].Theprotocolisasstated,eachnodeselectsapairofprimenumbers,suchthat
the desired duty cyclewill be the sum of their reciprocals. Each nodewill stay active if the
counter/timerisdivisiblebyoneofitsprimes.
Inthisprotocol,symmetric(allnodesusesamedutycycle)andasymmetric(nodesuse
differentdutycycle)primepairswereconsidered.Resultshaveshownthatasymmetricprime
pairsdramatically reducethediscovery latency,by30-50%.Discoprotocolachievesdiscovery
fasterthantheotherneighbordiscoveryprotocolsforasynchronousdutycycles,allowsnodesto
independentlyselecttheirowndutycycle.Hence,theprotocoloffersaprovableupperboundon
discoverylatency,andperformsbetterthanexpectedinpractice.
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Chapter3
DesignandExperimentalsetup
Discoalgorithmrandomlychoosesapairofprimenumberfornodessuchthatthesumof
theirreciprocalsisequaltothedesireddutycycle.Inthissection,wewillillustratein-depthabout
theDiscoalgorithm.
3.1Design
ChoosingPrimes
Itismoreefficienttochooseprimessuchthat,thereciprocalofoneoftheprimeisclose
tothedutycycle,whiletheotherprimenumberisrelativelylarge.Itisensuredthatsumofthose
reciprocalswillbeclosetothedesireddutycycle.This isbecausewhenoneofthereciprocal
node’s prime number is close to the desired duty cycle, its wake-up schedule will be more
efficient.For instance,consideranetworkof1%dutycycle(as intable3.1),nodecanchoose
primepairsof(139,479),(131,457),andsoon.Thefirstpair’sdutycyclewillgetclosetoa0.93%,
whichiscloseto1%.Asamatteroffact,anodecannotchooseasamepairofprimes(i.e.anode
chooses211and211).Table3.1demonstratesthecalculationofnodesprimenumberandits
desireddutycyclecalculation.
Table3.1:Examplesofapairofprimenumbersfor1%,10%and20%dutycycle.
Nodepairofprimes Desireddutycycle Sumofthereciprocal Node’sdutycycle
(139,479) 1% 1139
+1479
= 61866581
0.928%
(23,37) 10% 123
+137
= 60851
= 0.07 7%
(7,47) 20% 17+147
= 54329
= 0.164 16.4%
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Whenacounterisdivisiblebyoneofthenode’sprimenumbers,thenodewillturnonits
radioandbeaconsforafixedperiodtermedasslotduration.Furthermore,iftwoormorenodes
turnontheirradiosduringthesameperiod,thentheycanexchangebeaconsanddiscovereach
other.AsindicatedinTable3.1,thenodesdutycyclescannotbespecifiedwithfinegranularity,
especiallywithlargedutycycles.Terminologiesusedinourschemeisasfollows.
Definition1:Discovery
Itreferstotheprocessbywhichnodeslearnabouttheircurrentone-hopneighborsforthefirst
time.
Definition2:DiscoveryLatency(DL)
Discovery latency will be the time taken by the node to first discover once they become
neighbors.Itreferstothedelaybetweenthetimetwonodesareincommunicationrange(𝑇4),
tothetimewhentheyfirstdiscovereachother(𝑇567).
𝐷𝑖𝑠𝑐𝑜𝑣𝑒𝑟𝑦𝐿𝑎𝑡𝑒𝑛𝑐𝑦, 𝐷𝐿 = 𝑇567 −𝑇4
where,𝑇567 indicateswhentwonodes’radiosareoverlappingwhiletheyareinneighborhood.
Definition3:FailingLatency(FL)
Failinglatencyisobservedonlyamongstthenodesthathavebeendiscoveredalready.Itrefers
tothedelaybetweenthetimetwonodesarenotincommunicationrange(𝑇E),tothetimewhen
thetwonodeshavealreadylearnedabouteachother’swake-uppatterns(𝑇56F).
𝐹𝑎𝑖𝑙𝑖𝑛𝑔𝐿𝑎𝑡𝑒𝑛𝑐𝑦, 𝐹𝐿 = 𝑇56F −𝑇E
where,𝑇56F indicatesthatwhentwonodesshouldbeactiveinthesameperiodbuttheyarenot
neighbors.Table2showstheequationsofbothdiscoveryandfailinglatencies.
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ChoosingPrimes
Theprimenumberschosenwillcontrolthewake-uptimeofthenodesradio.Choosing
pairprimesisquitechallenging.Let’sconsideraninstanceonhowweconsidertheprimes.For
simplicityconsider2nodes.Letthedesireddutycycleforthenodesbe1%.Thepossibleprime
pairsforthe2nodesareasindicatedinTable3.2.Table3.2:Threedifferentcaseswhentwonodeshavea1%dutycycle.
Case Node1primes Node2primes 1stdiscovery(slotnumber)
1 (211,223) (199,229) 41989thslot
2 (131,383) (139,457) 18209thslot
3 (131,479) (131,487) 131stslot
Incase1,theprime-pairsfornode-1is(211,223)andfornode-2itis(199,229).Further
calculationsontheoverlappingwakeuptimesforthesenodesindicatethatthe1stdiscoveryin
idealscenariohappensattimeslotnumber41989.Incase2,theprime-pairschosenfornode1
andnode2are(131,383)and(139,457)respectively.The1stdiscoverycanhappenmostlikelyif
nocollisionhappensatslotnumber18209.Furthermore,incase3,theprime-pairschosenare
(131,479)and(131,487)fornode1andnode2.Thisindicatesthatthe1stdiscoverycouldhappen
atslot131.Also,ifthe1stneighbordiscoveryfailsincase1andcase2,forthenextdiscoverythe
waittimewouldbelongerwhereasincase3,theneighbordiscoveryhappensmoreoften.
Choosingareciprocalofaprimenumberthatisclosetodutycyclewillensurediscovery.
Thatis,lowdiscoverytimesarepossibleifoneofthereciprocalofprimenumbersisveryclose
tothedesireddutycycle,whiletheotherprimenumberisalargernumber.Hence,it ismore
importanttorandomizethechoiceofprimenumberstoreducethechancethattwonodeshave
thesamepairofprimenumberwhenthedesireddutycycleisthesame.Sinceinournetwork
setupwehavedensityof10nodes,it’simportantweshouldchooseatleast5primesthatare
closetothereciprocalofthedesireddutycycle,andassignthemrandomlytothenodes.This
techniquewillensuremorediscoveriesmorethanthefirsttwopreviousinstances.
10
3.2Experimentalsetup
Inthissection,weprovidetheimplementationdetailsforneighbordiscoveryinmobile
networks. We have simulated and analyzed the results using a network simulator, NS-3 on
networksizesof50nodesand100nodes[3].
Parameters
Table3.3indicatestheparametersconsideredinourexperimentalsetup.Neighborcheck
ishowoftenthenodescheckforthisalreadydiscoveredneighbors.Thispairwiseneighborcheck
isdoneforevery10ms.Slotdurationindicatesthetimeslotthenodeisgoingtobeactiveonce
theirradioisturnedon.Theslotdurationis20ms.Table3.3:Theexperimentparameters.
Typeofparameters Parameters
NeighborCheck 10ms
SlotDuration 20ms
Density(neighborregioncapacity) 10nodes
MobilitySpeed(m/s) 2-43-77-1515-25
Dutycycle(%) 1,10,20,30,50,100
NetworkSize 50,100nodes
Densityofthenetworkindicatesthenumberofneighborsinitsone-hopcommunication
range.Wehaveconsideredittobeupto10nodes.Mobilityspeedindicatesthespeedwithwhich
thenodesmoveinthenetwork.Itisvariedasindicatedinthetable3.3.Dutycycleindicatesthe
activetimeofthenode.Itisvariedbetween1%and100%.100%dutycycleindicatesthenodes
areawakeforentiredurationand1%indicatesitsactivetimeisminimalandissleepingmostof
thetime.Thenetworksizeofthisexperimentsetupwillbeeither50or100nodes.
11
Chapter4
Results
Inthischapter,weanalyzetheresultsofdiscoprotocolon50,and100networksizes.We
haveevaluatedthediscoverylatencyforvaryingdutycycles,mobilityspeedsandnetworksizes
inanetwork.Also,wehavestudiedfailinglatencyforvaryingdutycycles,mobilityspeedsand
networksizes.Theanalysisisbasedonthesimulationresultsobtainedfor10simulations.
4.1DiscoveryLatencyDiscoveryLatencyisafunctionofthenodes’dutycycles,aswellastheneighborcheck
time.
4.1.1DifferentDutyCycles
Inthiscaseweareanalyzingthediscoverylatencybyvaryingthedutycyclekeepingthe
mobilityconstant.Figure4.1–Figure4.4areresultsfornetworksize50nodesandFigure4.5–
Figure4.8areresultsfornetworksize100nodes.Weseetwopatternsinourresults.
1. Discoverylatencyincreasesasthedutycyclevariesfrom1%to10%
Theprimenumberpairchosendoesnotresultindutycycleclosetothedesiredprime
number.Thisisseenwhenthedutycycleis10%.
2. Discoverylatencydecreasesasthedutycyclevariesfrom10%to100%
12
Figure4.1:Thediscoverylatencyfor50nodesnetworkandthemobilityofnodesis2-4m/s.
Figure4.2:Thediscoverylatencyfor50nodesnetworkandthemobilityofnodesis3-7m/s.
13
Figure4.3:Thediscoverylatencyfor50nodesnetworkandthemobilityofnodesis7-15m/s.
Figure4.4:Thediscoverylatencyfor50nodesnetworkandthemobilityofnodesis15-25m/s.
14
Figure4.5:Thediscoverylatencyfor100nodesnetworkandthemobilityofnodesis2-4m/s.
Figure4.6:Thediscoverylatencyfor100nodesnetworkandthemobilityofnodesis3-7m/s.
15
Figure4.7:Thediscoverylatencyfor100nodesnetworkandthemobilityofnodesis7-15m/s.
Figure4.8:Thediscoverylatencyfor100nodesnetworkandthemobilityofnodesis15-25m/s.
16
4.1.2DifferentMobilitySpeeds
Inthiscaseweareanalyzingthediscoverylatencybyvaryingthemobilityspeedsofthe
nodekeepingthedutycycleconstant.Figure4.9–Figure4.14areresultsfornetworksize50
nodesandFigure4.15–Figure4.20areresultsfornetworksize100nodes.Weobservethatthe
discoverylatencydecreasesasthemobilityofthenodesincreases.Weseethispatternbecause
whenthenodesaremovingwithslowerspeedtheyremainneighborsforlongertimethanwhen
theymovewithfasterspeed.
In order to ensure this, we have evaluated the percentage of nodes that have been
neighborsbutnotdiscovered.ThisTable4.1showsthatasthemobilityincreasesthepercentage
ofundiscoveredneighbors’increases.
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒𝑜𝑓𝑢𝑛𝑑𝑖𝑠𝑐𝑜𝑣𝑒𝑟𝑒𝑑𝑛𝑒𝑖𝑔ℎ𝑏𝑜𝑟𝑠, 𝑃𝑛 = 𝑁45Q
𝑁45Q + 𝑁R∗ 100
where,𝑁45Q->totalnumberofnodesthathavebeenneighborsbutneverdiscovered
𝑁R->totalnumberofnodesthathavebeendiscovered
Table4.1:Percentagesofundiscoveredneighbors’nodesforFigure4.9network.
𝑃4(2-4m/s) 8.568%
𝑃4(3-7m/s) 10.496%
𝑃4(7-15m/s) 12.790%
𝑃4(15-25m/s) 14.247%
17
Figure4.9:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis1%.
Figure4.10:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis10%.
18
Figure4.11:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis20%.
Figure4.12:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis30%.
19
Figure4.13:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis50%.
Figure4.14:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis100%.
20
Figure4.15:Thediscoverylatencyfora100nodesnetworkandnodes’dutycycleis1%.
Figure4.16:Thediscoverylatencyfora100nodesnetworkandnodes’dutycycleis10%.
21
Figure4.17:Thediscoverylatencyfora100nodesnetworkandnodes’dutycycleis20%.
Figure4.18:Thediscoverylatencyfora100nodesnetworkandnodes’dutycycleis30%.
22
Figure4.19:Thediscoverylatencyfora100nodesnetworkandnodes’dutycycleis50%.
Figure4.20:Thediscoverylatencyfora100nodesnetworkandnodes’dutycycleis100%.
23
4.2FailingLatencyFailinglatencyisobservedonlyamongstthenodesthathavebeendiscoveredalreadyandthey
havemovedoutofthecommunicationrangewhentheyhadtoexchangeinformation.
4.2.1DifferentDutyCycles
Inthiscaseweareanalyzingthefailing latencybyvaryingthedutycyclesofthenode
keepingthemobilityconstant.Figure4.21–Figure4.24areresultsfornetworksize50nodesand
Figure4.25–Figure4.29areresults fornetworksize100nodes.Weseetwopatterns inour
results.
1. Failinglatencyslightlyincreasesasthedutycyclevariesfrom1%to10%
Theprimenumberpairchosendoesnotresultindutycycleclosetothedesiredprime
number.Thisisseenwhenthedutycycleis10%.
2. Failinglatencydecreasesasthedutycyclevariesfrom10%to100%significantly
24
Figure4.21:Thefailinglatencyfora50nodesnetworkandthemobilityofnodesis2-4m/s.
Figure4.22:Thefailinglatencyfora50nodesnetworkandthemobilityofnodesis3-7m/s.
25
Figure4.23:Thefailinglatencyfora50nodesnetworkandthemobilityofnodesis7-15m/s.
Figure4.24:Thefailinglatencyfora50nodesnetworkandthemobilityofnodesis15-25m/s.
26
Figure4.25:Thefailinglatencyfora100nodesnetworkandthemobilityofnodesis2-4m/s.
Figure4.26:Thefailinglatencyfora100nodesnetworkandthemobilityofnodesis3-7m/s.
27
Figure4.27:Thefailinglatencyfora100nodesnetworkandthemobilityofnodesis7-15m/s.
Figure4.28:Thefailinglatencyfora100nodesnetworkandthemobilityofnodesis15-25m/s.
28
4.2.2DifferentMobilitySpeeds
Inthiscaseweareanalyzingthefailinglatencybyvaryingthemobilityspeedsofthenode
keepingthedutycycleconstant.Figure4.29–Figure4.34areresultsfornetworksize50nodes.
Weobservethatthefailinglatencyisnotaffectedbychangingthemobilityspeed.
Figure4.29:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis1%.
Figure4.30:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis10%.
29
Figure1.31:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis20%.
Figure4.32:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis30%.
30
Figure4.33:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis50%.
Figure4.34:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis100%.
31
Chapter5
FutureWorkandConclusion5.1FutureWork
In this work, we analyzed both discovery and failing latency in mobile networks for
networksizes50and100nodes.Infuture,wewouldliketoanalyzetheresultsfordiscoveryand
failing latency on larger networks (>1000 nodes). Bian et al. [9] presented a comprehensive
surveyaboutmostadvancedneighbordiscoveryprotocols inmobilesensingapplications.The
authors adopted two-level classification. At the higher level, neighbor discovery can be
categorizedintodirectandindirectapproaches.
Directneighbordiscoveryapproachmeanswhenanodediscoversanothernode,thetwo
nodesexchangetheirwakeupschedulesonly.While in indirectneighbordiscoveryapproach,
the technique uses a direct neighbor discovery approach as building blocks and exploit the
collaborationofdirectdiscoveredneighborstodiscovernewneighborsindirectly.Inotherwords,
whentwonodesdiscovereachother,theywillexchangewhattheirlistofnodeswhichhavebeen
discovered.Anextendapproachtomyimplementationsistoenableindirectneighbordiscovery
approach.
5.2Conclusion
After studying Disco; an asynchronous neighbor discovery and rendezvous protocol,
whichallowsnodestooperateatlowdutycycle,yettheydiscovereachotherregardlessofany
prior synchronization information. The Disco’s propose has not been yet tested on large
networks. Itmotivatesme to analyze this protocol on largemobile networks (50 nodes/100
nodes)usinganetworksimulator(NS-3).
32
Neighbordiscoveryhasbeenafundamentalprobleminthesensorsnetworks,wireless
networks,particularly, inmobilewirelessnetworks.ThisworkverifiesthatDiscoprotocolcan
handlelargenetworks.Analyzingbothdiscoveryandfailinglatenciesonthosenetworkswillgive
thenetworkdesigneraclearpicturebasedontheirneeds.
ResultshavebeenevaluatedthatDiscocanachieveenormousnumberofdiscoveriesover
ashortamountoftime(100sec),whilediscoverylatenciesonacertaindutycyclecanvarywith
differentmobilityspeeds;stilltheywereverysatisfying.
33
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