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1、1452IEEEJOURNALONSELECTEDAREASINCOMMUNICATIONS,VOL.24,NO.8,AUGUST2006ATutorialonCross-LayerOptimizationinWirelessNetworksXiaojunLin,Member,IEEE,NessB.Shroff,SeniorMember,IEEE,andR.Srikant,Fellow,IEEETutorialPaperAbstract—Thistutorialpaperoverviewsrecentdevelopmen
2、tsindesignoftheprotocolstack.1Indeedthereareuniquechallengesoptimization-basedapproachesforresourceallocationproblemsinthewirelesscontextthatdonotallowadirectapplicationinwirelesssystems.WebeginbyoverviewingimportantresultsinofsuchtechniquesfromtheInternetsetting
3、.Inparticular,thetheareaofopportunistic(channel-aware)schedulingforcellular(single-hop)networks,whereeasilyimplementablemyopicpolicieswirelessmediumisaninherentlymultiaccessmediumwhereareshowntooptimizesystemperformance.Wethendescribekeythetransmissionsofusersint
4、erferewitheachotherandwherelessonslearnedandthemainobstaclesinextendingtheworkthechannelcapacityistime-varying(duetousermobility,togeneralresourceallocationproblemsformultihopwirelessmultipath,andshadowing).Thiscausesinterdependenciesnetworks.Towardsthisend,wesho
5、wthataclean-slateoptimiza-tion-basedapproachtothemultihopresourceallocationproblemacrossusersandnetworklayersthataresimplynotpresentnaturallyresultsina“looselycoupled”cross-layersolution.Thatintheirwirelinecounterparts.Inspiteofthesedifficulties,is,thealgorithmsob
6、tainedmaptodifferentlayers[transport,therehavebeensignificantrecentadvancesthatdemonstratenetwork,andmediumaccesscontrol/physical(MAC/PHY)]ofthethatwirelessresourcesacrossmultiplelayers(suchastime,protocolstack,andarecoupledthroughalimitedamountofinfor-mationbeing
7、passedbackandforth.Itturnsoutthattheoptimalfrequency,power,linkdatarates,andend-userdatarates),schedulingcomponentattheMAClayerisverycomplex,andthuscanbeincorporatedintoaunifiedoptimizationframework.needssimpler(potentiallyimperfect)distributedsolutions.WeInterest
8、ingly,aswillbedescribedindetailinSectionIII,thedemonstratehowtouseimperfectschedulinginthecross-layersolutionofsuchanoptimizationframeworkwillitselfexhibitfram
