电子科大无线传感器网络课件wsn_chapter_5_MAC

0UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksChapter5:MACProtocols1UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworks物理层数据链路层网络层传输层应用层能量分配移动管理应用优化无线传感器网络协议ApplicationLayerTransportLayerNetworkLayerLinkLayerPhysicalLayerPowerManagementPlaneMobilityManagementPlaneTaskManagementPlane2UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworks数据链路层（DL：DataLinkLayer）数据链路层的主要作用是通过校验、确认和反馈重发等手段将该原始的物理连接改造成无差错的数据链路其主要任务是加强物理层传输原始比特的功能，使之对网络层显现为一条无错线路。两个设备同时在网络的共享媒体(有线或无线)上发送信息时，会相互干扰而导致传输都无效因此对共享媒体的访问需要有效的管理3UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworks数据链路层的功能链路管理帧同步（帧定界）帧的透明传输流量控制差错控制寻址数据链路层协议:为实现数据链路控制功能而制定的规程或协议。4UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworks局域网数据链路层的两个子层由于局域网中传输介质的多样性，为了使数据链路层能更好地适应多种局域网标准，802将局域网的数据链路层拆成两个子层：逻辑链路控制LLC(LogicalLinkControl)子层媒体访问控制MAC(MediumAccessControl)子层。与接入到传输媒体有关的内容都放在MAC子层，而LLC子层则与传输介质无关，不管采用何种协议的局域网对LLC子层来说都是透明的无线传感网传输介质相对采用单一的射频，因而无需分层。WSN仍然是多点共享传输介质，必须提供相应机制来控制对传输介质的访问。5UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksObjectivesofMACProtocols控制设备允许访问物理层传输数据的方式和时间CollisionAvoidanceEnergyEfficiencyScalabilityLatencyFairnessThroughputBandwidthUtilization6UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksChallengesforMACinWSNs1.WSNArchitectureHighdensityofnodesIncreasedcollisionprobabilitySignalingoverheadshouldbeminimizedtopreventfurthercollisionsSophisticatedandsimplecollisionavoidanceprotocolsrequired7UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksChallengesforMACinWSNs2.LimitedEnergyResourcesConnectivityandtheperformanceofthenetworkisaffectedasnodesdieTransmittingandreceivingconsumesalmostsameenergyFrequentpowerup/downeatsupenergyNeedverylowpowerMACprotocolsMinimizesignalingoverheadAvoididlelisteningPreventfrequentradiostatechanges(active-sleep)8UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksPOWERCONSUMPTIONSENSOR05101520Power(mW)CPUTXRXIDLESLEEPRADIO9UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworks*IdleListening*Transmitter*ReceiverOBJECTIVE:Reduceenergyconsumption!!MajorSourcesofEnergyWasteCommontoallwirelessnetworks10UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksChallengesforMACinWSNs3.LimitedProcessingandMemoryCapabilitiesComplexalgorithmscannotbeimplementedConventionallayeredarchitecturemaynotbeappropriateCentralizedorlocalmanagementislimitedSimpleschedulingalgorithmsrequiredCross-layeroptimizationrequiredSelf-configurable,distributedprotocolsrequired11UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksChallengesforMACinWSNs4.LimitedPacketSizeUniquenodeIDisnotpracticalLimitedheaderspaceLocalIDsshouldbeusedforinter-nodecommunicationMACprotocoloverheadshouldbeminimized5.CheapEncoder/DecodersCheapnoderequirementpreventssophisticatedencoders/decoderstobeimplementedSimpleFECcodesrequiredforerrorcontrolChannelstatedependentMACcanbeusedtodecreaseerrorrate12UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksChallengesforMACinWSNs6.InaccurateClockCrystalsCheapnoderequirementpreventsexpensivecrystalstobeimplementedSynchronizationproblemsTDMA-basedschemesarenotpractical7.Event-basedNetworkingObserveddatadependsonphysicalphenomenonSpatialandtemporalcorrelationinthephysicalphenomenonshouldbeexploitedBOTTOMLINE:ExistingMACprotocolscannotbeusedforWSNs!!!13UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksOverviewofMACProtocolsforWSNs1.Contention(RANDOM/CSMA)-BasedMACProtocolsSleep-MAC,BMAC,T-MAC,X-MAX,CCMAC,etc…2.Reservation-Based(TDMABASED)MACProtocolsTRAMA,DMAC,FLAMA,etc…3.HYBRID(CSMA/TDMA)MACProtocolsZMAC,….14UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksMACProtocolsforWSN?-MAC(pickyourletter!)μ-MAC,AI-LMAC,B-MAC,Bit,BMA,CC-MAC,CMAC,Crankshaft,CSMA-MPS,CSMA/ARC,DMAC,E2-MAC,EMACs,f-MAC,FLAMA,Funneling-MAC,G-MAC,HMAC,LMAC,LPL…MMAC,MR-MAC,nanoMAC,O-MAC,PACT,PEDAMACS,PicoRadio,PMAC,PMAC,Q-MAC,Q-MAC,QMAC,RATEEST,RL-MAC,RMAC,RMAC,S-MAC,S-MAC/AL,SCP-MAC,SEESAW,Sift,SMACS,SS-TDMA,STEM,T-MAC,TA-MAC,TICER,TRAMA,U-MAC,WiseMAC,X-MAC,Z-MAC~koen/MACsoup/15UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksContention(Random)-BasedMACProtocolsChannelaccessthroughcarriersensemechanism.Providerobustnessandscalabilitytothenetwork.Collisionprobabilityincreaseswithincreasingnodedensity.16UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksIEEE802.11IEEE802.11,“WirelessLANmediumaccesscontrol(MAC)andphysicallayer(PHY)specifications,”1999OriginallydevelopedforWLANs17UniversityofElectronicScienceandTechnologyofChinaWirelessSensorNetworksREMINDERBASICKNOWLEDGEBASICCSMA/CA(FLOWCHART)(DistributedFoundationWirelessMediumAccessControl-DistributedCoordinatedFunctionCSMA/CA(DFWMAC-DCF)forIEEE802.11)18UniversityofElectronicScienceandTechno