analyzing discovery latency in mobile networks

Graduate Theses, Dissertations, and Problem Reports

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

ElectricalEngineering

VinodKulathumani,Ph.D,Chair

XinLi,Ph.D

YanfangYe,Ph.D

LaneDepartmentofComputerScienceandElectricalEngineering

Morgantown,WestVirginia

Keywords:neighbordiscovery,discoverylatency,disco,manet

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.

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.

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

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

Figure4.12TheDiscoveryLatencyfor50nodesandnodes’dutycycleis30%......................28

Figure4.13 TheDiscoveryLatencyfor50nodesandnodes’dutycycleis50%........................7

Figure4.16 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis10%....................18

Figure4.20 TheDiscoveryLatencyfor100nodesandnodes’dutycycleis100%..................25

Figure4.21 TheFailingLatencyfor50nodesandthemobilityofnodesis2-4m/s................26

Figure4.23TheFailingLatencyfor50nodesandthemobilityofnodesis7-15m/s..............28

Figure4.24 TheFailingLatencyfor50nodesandthemobilityofnodesis15-25m/s..............3

Figure4.27 TheFailingLatencyfor100nodesandthemobilityofnodesis7-15m/s............15

Figure4.28 TheFailingLatencyfor100nodesandthemobilityofnodesis15-25m/s..........18

Figure4.29 TheFailingLatencyfor50nodesandnodes’dutycycleis1%............................19

Figure4.30 TheFailingLatencyfor50nodesandnodes’dutycycleis10%...........................23

Figure4.33 TheFailingLatencyfor50nodesandnodes’dutycycleis50%............................3

Figure4.34 TheFailingLatencyfor50nodesandnodes’dutycycleis100%..........................7

ListofTables

Table3.1Examplesforapairofprimenumbersfor1%,10%,and20%dutycycle.................2

Table3.2Threedifferentcaseswhentwonodeshavea1%dutycycle.................................10

Table3.3Theexperimentparameters....................................................................................10

Table4.1Percentagesofundiscoveredneighbors’nodesforFigure4.19network...............16

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.

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,

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.

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.

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

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.

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

= 61866581

0.928%

(23,37) 10% 123

= 60851

= 0.07 7%

(7,47) 20% 17+147

= 54329

= 0.164 16.4%

Whenacounterisdivisiblebyoneofthenode’sprimenumbers,thenodewillturnonits

radioandbeaconsforafixedperiodtermedasslotduration.Furthermore,iftwoormorenodes

turnontheirradiosduringthesameperiod,thentheycanexchangebeaconsanddiscovereach

other.AsindicatedinTable3.1,thenodesdutycyclescannotbespecifiedwithfinegranularity,

especiallywithlargedutycycles.Terminologiesusedinourschemeisasfollows.

Definition1:Discovery

Itreferstotheprocessbywhichnodeslearnabouttheircurrentone-hopneighborsforthefirst

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.

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.

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.

Chapter4

Results

Inthischapter,weanalyzetheresultsofdiscoprotocolon50,and100networksizes.We

haveevaluatedthediscoverylatencyforvaryingdutycycles,mobilityspeedsandnetworksizes

inanetwork.Also,wehavestudiedfailinglatencyforvaryingdutycycles,mobilityspeedsand

networksizes.Theanalysisisbasedonthesimulationresultsobtainedfor10simulations.

4.1DiscoveryLatencyDiscoveryLatencyisafunctionofthenodes’dutycycles,aswellastheneighborcheck

4.1.1DifferentDutyCycles

Inthiscaseweareanalyzingthediscoverylatencybyvaryingthedutycyclekeepingthe

mobilityconstant.Figure4.1–Figure4.4areresultsfornetworksize50nodesandFigure4.5–

Figure4.8areresultsfornetworksize100nodes.Weseetwopatternsinourresults.

1. Discoverylatencyincreasesasthedutycyclevariesfrom1%to10%

Theprimenumberpairchosendoesnotresultindutycycleclosetothedesiredprime

number.Thisisseenwhenthedutycycleis10%.

2. Discoverylatencydecreasesasthedutycyclevariesfrom10%to100%

Figure4.1:Thediscoverylatencyfor50nodesnetworkandthemobilityofnodesis2-4m/s.

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%

Figure4.9:Thediscoverylatencyfora50nodesnetworkandnodes’dutycycleis1%.

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

Figure4.21:Thefailinglatencyfora50nodesnetworkandthemobilityofnodesis2-4m/s.

4.2.2DifferentMobilitySpeeds

Inthiscaseweareanalyzingthefailinglatencybyvaryingthemobilityspeedsofthenode

keepingthedutycycleconstant.Figure4.29–Figure4.34areresultsfornetworksize50nodes.

Weobservethatthefailinglatencyisnotaffectedbychangingthemobilityspeed.

Figure4.29:Thefailinglatencyfora50nodesnetworkandnodes’dutycycleis1%.

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).

Neighbordiscoveryhasbeenafundamentalprobleminthesensorsnetworks,wireless

networks,particularly, inmobilewirelessnetworks.ThisworkverifiesthatDiscoprotocolcan

handlelargenetworks.Analyzingbothdiscoveryandfailinglatenciesonthosenetworkswillgive

thenetworkdesigneraclearpicturebasedontheirneeds.

ResultshavebeenevaluatedthatDiscocanachieveenormousnumberofdiscoveriesover

ashortamountoftime(100sec),whilediscoverylatenciesonacertaindutycyclecanvarywith

differentmobilityspeeds;stilltheywereverysatisfying.

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