MCT-2-wireless-channel.ppt

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1、电车难题（TheTrolleyProblem）“电车难题”是伦理学领域最为知名的思想实验之一，其内容大致是：一个疯子把五个无辜的人绑在电车轨道上。一辆失控的电车朝他们驶来，并且片刻后就要碾压到他们。幸运的是，你可以拉一个拉杆，让电车开到另一条轨道上。但是还有一个问题，那个疯子在那另一条轨道上也绑了一个人。考虑以上状况，你应该拉拉杆吗？WirelessCommunicationChannelsIntroductiontoWirelessCommunicationChannelsShannon’scommunicationchannelImpulseresponseof

2、wirelessfadingchannelsLarge-scaleandsmallscalepropagationmodelsLog-NormalshadowingchannelShort-termfadingchannelAutocorrelationfunctionsandpowerspectraldensitiesAssumption:WSSUSTimespreadingTimevariationsChannelclassificationChannelsimulationsShannon’sWirelessCommunicationSystemSourceS

3、ourceEncoderChannelEncoderMod-ulatorUserSourceDecoderChannelDecoderDemod-ulatorMessageSignalChannelcodewordEstimateofMessagesignalEstimateofchannelcodewordReceivedSignalModulatedTransmittedSignalWirelessChannelLargeandSmallScalePropagationModelsArea2Area1TransmitterLog-normalshadowingS

4、hort-termfadingWirelessCommunicationSystemv(t)noisen(t)u(t)r(t)Channel1...user1userMCo-ChannelInterference-InterferenceForwardChannelChannel1ChannelMTransmitterReceiverReverseChannelImpulseResponseCharacterizationt(t0)t0t2t(t2)t1t(t1)TimespreadingpropertyTimevariationspropertyImpulsere

5、sponse:Time-spreading:multipathandtime-variations:time-varyingenvironmentComplexlow-passrepresentationofimpulseresponseMultipathFadingComponentsBand-passrepresentationofimpulseresponse:Band-passRepresentationofImpulseResponseLow-passandband-passrepresentationofreceivedsignal:Representa

6、tionofAdditiveNoiseChannelLargescalepropagationmodels:T-RseparationdistancesarelargeMainpropagationmechanism:reflectionsAttenuationofsignalstrengthduetopowerlossalongdistancetraveled:shadowingDistributionofpowerlossindBs:Log-NormalLog-NormalshadowingmodelFluctuationsaroundaslowlyvaryin

7、gmeanLargeandSmallScalePropagationModelsLargeandSmallScalePropagationModelsSmallscalepropagation:T-RseparationdistancesaresmallHeavilypopulated,urbanareasMainpropagationmechanism:scatteringMultiplecopiesoftransmittedsignalarrivingatthetransmittedviadifferentpathsandatdifferenttime-de