TCP Simulation Evaluations over Ad Hoc Wireless Networks(2)

IV.SIMULATIONSETUP

Weusedthens2[7]simulatortoperformourevaluation.Fig.2showsthescenariousedinoursimulations.Eachnodeis200metersapartfromitsclosestneighborsandthewirelessdatarateis2Mbps.Inthesimulator,theeffectivetransmissionrangeis250meterswhiletheinterferencerangeis550metersasrecommendedbytheIEEE802.11standard[2].Inallevaluations,thethroughputbwiscomputedasbw=seq 8

The Transmission Control Protocol (TCP) represents the most deployed transport protocol used in the Internet so far. This popularity motivates its presence in wireless networks, including ad hoc networks. These networks are very promising since they make i

isthemaximumsequencenumber(inbytes)transmittedandacknowledgedandstimeisthesimulatedtime.Wefocusourdiscussionsonshortchainofnodescontainingatmost7hops,becausethisisareasonablelimitfortoday’snetworks.The rstnodeisthesenderandthelastnodeisthereceiverofthepackets.Thesendertransferscontinuouslya le(in niteftp)tothereceiver.Forgeneratingten ows,weusedtenftpagentsatthesender.Atthereceiver,dependingonthe ownumber,weplacedoneortensinkreceiveragent.Duringtheeneryconsumptionanalyses,weusedanenergymodelthatcomputesenergyexpendituretotransmittedandreceivedpacketsonly.Energyspentinidlestateiscomputed.Inthisway,theenergyrelatedtoonlyTCPoperationsarebetterevaluated.Themeasuredenergyistheoneconsumedbythesender.sender nodenreceiver node

Fig.2.Chaintopology

Theparameterssettingsareasfollows.IEEE802.11istheMAClayerprotocol.AODVistheroutingprotocol.Theinitialenergyofnodesis1000joules,adynamic atareacomputedas(numberofhops*200m+100m)x(300m).Thewindowlimit(WL)fortheTCP avoursis3packets.Totakeintoaccountthehiddennodeproblem,wesimulated5and6hopsforthemeasurementsoftheenergyconsumptionandthethroughput.Unlessotherwisementioned,theotherparameterswerekeptasthedefaultofthesimulatorandallsimulationrunslasted300seconds.Forthesimulationswithlosses,auniformdistributionfunctionisusedaserrorpattern,and5%ofPacketErrorRate(PER)issimulated.

V.SIMULATIONRESULTS

A.EnergyConsumption

InthissectionweevaluatetheenergyconsumptionpatternforTCPwithvaryingpacketsizesand5hopsinFig.IV.Energyconsumptionisaveryimportantaspectforadhocnetworksasthenodesinplacearesupposedtobebatterypowered.Fig.3(a)andFig.3(b)depicttheresultsforpacketsizesof250,500,1000,and1460bytesunder1and10 ows,respectively.Ageneralconclusionfromtheseresults,isthatthelargerthepacketthelessenergyspent,asshowninbothFigs.ThisisintuitivebecausewithshortpacketsizeTCPsenderhastoperformmoreoperationstosendthewholedata.BothFigsalsoshowthatbyusingtheDelayedAcknowledgment(DA)optionthetwoTCP avourssavedsomeenergy.Fortheone owevaluation,TCPSACKwithoutDAspentupto16%paringTCPSACKwithTCPNewreno,wedidnotgetcleardistinctionbetweenbothperformances.InourexperimentswithDA,TCPNewrenoperformedslightlybetterthantheTCPSACKforshortpacketsizes.

The Transmission Control Protocol (TCP) represents the most deployed transport protocol used in the Internet so far. This popularity motivates its presence in wireless networks, including ad hoc networks. These networks are very promising since they make i

Energy Spent (joule *e-7/bits) Energy spent vs. Paket Size (1 flows) 20NewReno Sack NewReno DASack DA 16 12 8 0 200 400 600 800 1000 1200 1400 1600Paket Size (bytes)

(a)1 ow

Energy Spent (joule *e-7/bits) Energy spent vs. Paket Size (10 flows) 20NewReno Sack NewReno DASack DA 16 12 8 0 200 400 600 800 1000 1200 1400 1600Paket Size (bytes)

(b)10 ows

Fig.3.EnergyConsumption

B.EnergyConsumptionIncludingPacketErrorRateof5%

Owingtoobservetheenergyef ciencyofTCPNewrenoandTCPSACKoveranadhocnetworkincludinglosses,wesimulatedthesamenetworkthatisusedintheprevioussection.Thereisnocongestionbutonlyapacketerrorrateof5%.Figs.4(a)and4(b)illustratetheresultsforpacketsizesof250,500,1000,and1460bytesunder1and10 ows,respectively.Weobtainedthesamegeneralconclusionsthatwehadforthecasewithouterror.Yettheenergyconsumptionincreasedwiththepacketerrorconstraint.DAoptionreducedthespentenergyunderlossesaswell.Fig.4(b)showsthatTCPSACKwithDAperformed

The Transmission Control Protocol (TCP) represents the most deployed transport protocol used in the Internet so far. This popularity motivates its presence in wireless networks, including ad hoc networks. These networks are very promising since they make i

Energy Spent (joule *e-7/bits) Energy spent vs. Paket Size (1 flows / 5% error) 32 28 24 20 16 12 0 200 400 600 800 1000 1200 1400 1600Paket Size (bytes)NewReno Sack NewReno DASack DA

(a)1 owEnergy Spent (joule *e-7/bits) Energy spent vs. Paket Size (10 flows/ 5% error) 32 28 24 20 16 12 0 200 400 600 800 1000 1200 1400 1600Paket Size (bytes)NewReno Sack NewReno DASack DA

(b)10 ows

Fig.4.EnergyConsumptionwithPacketErrorRateof5%

paringFigs.4(a)and4(b)onecansaythatforsmallpacketsizesTCPNewrenooutperformedTCPSACKforthescenariowithone ow.Theoppositehappenedfortheten owscase.Forlargepacketsizeswedidnotnoticeanydifferencebetweenthetwo avours.Inshort,theonlyeffectiveconclusionfromtheseresultsisthatDAishelpfullforenergyconsumptionbene ts,evenfornoisyenvironments.

C.Retransmissions

Theideahereistoobservethetypicalbehavioroftheretransmissionsintheadhocnetworks.Forthat,wesimulated owswithpacketsizeof250,500,1000,and1460bytes.

The Transmission Control Protocol (TCP) represents the most deployed transport protocol used in the Internet so far. This popularity motivates its presence in wireless networks, including ad hoc networks. These networks are very promising since they make i

Asintheprevioussimulations,weconsideredtheDAoptionawell.ThescenarioisalsothechaintopologyofFig.2with5and6hops.TheresultsareshowninFigs.5and6,whichincludeevaluationsfor1or10 ows,respectively.

Number of Retransmissions Retransmissions vs. Paket Size (1 flow) 80 70 60 50 40 30 20 10 0 0 200 400 600 800 1000 1200 1400 1600

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