移动通信课件new

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1、Chapter2MobileRadioPropagationandChannelModelingandChannelModeling1HITCRC1Outline(目录)2.1Propertiesofradiopropagation22Freespacepropagation2.2Freespacepropagation2.3Transmissionmechanismofelectromagneticwave2.4PathTransmissionLoss2.5ShadowingFading26Mli2.6Multi-p

2、athfdihfading2.7Channelmodelingformulti-pathchannelHITCRC22HITCRC2Outline(目录)2.1Propertiesofradiopropagation22Freespacepropagation2.2Freespacepropagation2.3Transmissionmechanismofelectromagneticwave2.4PathTransmissionLoss2.5ShadowingFading26Mli2.6Multi-pathfdihf

3、ading2.7Channelmodelingformulti-pathchannelHITCRC33HITCRC3基站遮挡BlockingBasestation散射体大反射体(Scatterers)(()reflector)移动台Mobilestation电波衰减随着移由于基站与移动台之间由移动台周边散射物对动台到基站的距的建筑物等对电波的遮电波的反射，折射与散离增大而增加．挡与反射，到达移动台射，这些波的相互干涉周边的电波能量有缓慢使得接收功率产生瞬时的变动.的变动．大尺度衰落Largescalefading小尺度

4、衰落SmallscalefadingHITCRC44HITCRC4PropertiesofradiopropagationMultipathfading多径衰落约1mShadowing阴影衰落约100mPathloss路径传输损耗基站距离BasestationDistanceHITCRC55HITCRC5Outline(目录)2.1Propertiesofradiopropagation22Freespacepropagation2.2Freespacepropagation2.3Transmissionmechani

5、smofelectromagneticwave2.4PathTransmissionLoss2.5ShadowingFading26Mli2.6Multi-pathfdihfading2.7Channelmodelingformulti-pathchannelHITCRC66HITCRC6Freespacepropagation•Freespace，isauniformnon-lossinfinitespace.Inidealcondition,thespppaceisisotropic,,itselectriccon

6、ductivityyis0,,andbothofitsrelativepermittivityandrelativemagneticconductivityareequalto1.（所谓自由空间，严格来说应指真空。通常把均匀无损耗的无限大空间视为自由空间。该空间具有各向同性、电导率为零、相对介电系数和相对磁导率均恒为1的特点，这是一种理想情况。）•实际无线电波传播路径是不可能获得这种条件的。现实的电波传播媒质是有损耗的且是不均匀的，因而电波传播的过程中除有衰减外，还会出现折射、反射、散射和绕射现象。在研究移动通信电波传

7、播问题时，为了能提供一个比较各种传播情况的标准，并简化场强和传输损耗的计算方法，才引入了自由空间电波传播这一概念。7HITCRC7Freespacepropagation•AnisotropicantennainfreezdAd2spaceandradiatedpower(辐射r功率)P(W))P(W)，aspheresurfaceaspheresurfaceAntenna(球面面积)ofdistanced(m)Aperturefromradiatoris:r24dy•Thepowerfluxdensity(

8、功率密Second度)(poyntingvector,坡印廷矢Aperture量)2SPG/4dTT8HITCRC8Freespacepropagation•AfAntennaefffecti(ivearea(有效面积)2AG(/)4eR•ReceivedpowerReceivedpower222PSA(/PG4)