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1WirelessMeshNetworksIssuesateachlayer指导老师：舒炎泰教授学生：刘春贵©2006TianjinUniversityComputerDepartmentOverviewofResearchTopicsPhysicalLayerMACLayerNetworkLayerTransportLayerApplicationLayerTianjinUniversityComputerDepartmentPhysicalLayer(PHY)WishlistPerformanceBandwidthRobustmodulationSensitivityShortpreambleFastswitchbetweenchannelsFastswitchfromTx/RxandbackExtrasMobility(potentiallyhigh-speed)LinkadaptationVariabletransmissionpowerMultiplechannelsLinkqualityfeedbackTianjinUniversityComputerDepartment在一个大的范围内实现高的传输率，需要新的宽带传输方案(除OFDM和UWB之外)；研究多天线系统，但复杂性和成本太高还不能被商业广泛接受；Frequency-agile技术仍处于早期阶段,在被商业接受之前还需要大量的研究努力；虽然已经建议的Adaptive/smart天线等的多天线系统,以及MIMO系统能增加容量和减轻由于衰退、通道干扰引起的损害，但对WMNs而言，开发这种技术是一个更具挑战的问题；为了更好的利用物理层提供的先进技术，尤其MAC层协议需要和物理层交互的工作。因此，设计物理层的一些组件时，应使高层能访问或控制它们。这就使得硬件的设计更具挑战性,同时,也触发低成本软件radio技术的创新。PHY-OpenResearchIssuesTianjinUniversityComputerDepartmentPHY-ModulationExistingmodulationsworkwell(OFDM,DSSS,etc.).UWBmaybeaninterestingalternativeforshortdistances(WPANs)SpreadspectrumsolutionsarepreferredastheytendtohavebetterreliabilityinthefaceofFading(veryimportantformobileapplications)Interference(moreofafactorthaninanyotherwirelesssystem)TianjinUniversityComputerDepartmentM,N,K,L的值不同会产生各种多天线系统；接收方有多个天线接受，发送方是单个通道(K=1,M=1以及或L>1或N>1)的设计已经被建议，接受方能够收到至少一个好信号的概率是很高的。PHY-MIMSTianjinUniversityComputerDepartmentPHY-SmartAntennasAdvantagesLowpowertransmissionsBatterynotabigconcerninmanyapplicationsEnablesbetterspatialreuseand,hence,increasednetworkcapacityBetterSNRBetterdataratesBetterdelaysBettererrorratesAdvantagesDisadvantagesSpecializedhardwareSpecializedMAC(difficulttodesi...