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%http://www.77cn.com.cnparingTCPSACKwithTCPNewreno,wedidnotgetcleardistinctionbetweenbothperformances.InourexperimentswithDA,TCPNewrenoperformedslightlybetterthantheTCPSACKforshortpacketsizes.