移動無線系統(tǒng)傳播環(huán)境建模的現(xiàn)代處理

1、移動無線系統(tǒng)傳播環(huán)境建模的現(xiàn)代處理作者:mick摘要：摘要：................................................................................................................................2傳播現(xiàn)象傳播現(xiàn)象.....................................................

2、.......................................................................3傳播模型傳播模型............................................................................................................................5宏蜂窩傳播模型宏蜂窩傳播模型.

3、...............................................................................................................6奧村（奧村（Okumura）等人的模型）等人的模型...................................................................................

4、....6ITU（CCIR）模型）模型..........................................................................................................7“透過角透過角“方法方法..................................................................................

5、.................................8愛立信模型愛立信模型9999.............................................................................................................10李氏模型李氏模型.....................................................

6、.....................................................................11COST231WalfischIkegami模型模型...............................................................................12ETF人工神經(jīng)網(wǎng)絡宏蜂窩模型人工神經(jīng)網(wǎng)絡宏蜂窩模型.................

7、...................................................................13微蜂窩傳播模型微蜂窩傳播模型..............................................................................................................14經(jīng)驗模型經(jīng)驗模型.................

8、.........................................................................................................15兩射線模型兩射線模型.......................................................................................................

9、...............16基于基于UTD和多鏡像理論的模型和多鏡像理論的模型...................................................................................17李氏微蜂窩模型李氏微蜂窩模型...............................................................................

10、...............................18室內(nèi)傳播模型室內(nèi)傳播模型..................................................................................................................20經(jīng)驗模型經(jīng)驗模型...................................................

11、.......................................................................20射線追蹤模型射線追蹤模型..................................................................................................................21時域有限差分模型時域有限差分模型...

12、.......................................................................................................22ETF人工神經(jīng)網(wǎng)絡模型人工神經(jīng)網(wǎng)絡模型................................................................................................

13、23結(jié)論結(jié)論..................................................................................................................................24對場強的精確估計是一件很復雜而又困難的任務。到目前為止，文獻中提出了多種不同的場強預測方法。本文對常用的預測模型進行歸納，基于本文作者的經(jīng)驗，介紹了一些提高其精確度

14、的有用的算法。應當注意在大多數(shù)情形下，所提出的模型預測的是本地的平均值（中值、平均、慢衰落），這些對進行無線系統(tǒng)設計的系統(tǒng)工程師而言更有價值。另一方面，時域彌散的模型則對設備生產(chǎn)商更有價值，這里不作介紹。Themainpropagationmechanismsoftheradiosignalaredescribed.Definitionssomebasicacteristicsofthepropagationmodelsaregiven

15、.Macrocellmicrocellindopropagationmodelsareconsideredindetailinthelatersections.Inthesesectionsanoverviewofpopularpredictionmodelsisgiven.Theiradvantagesdisadvantagesarediscussedinadditionsomepracticalimprovementsofthese

16、modelsalongwithsomenewmodelsaredescribed.本文介紹了電波傳播的主要傳播機理。給出了傳播模型的定義及一些基本的特性。在即后的幾節(jié)里詳細討論了宏蜂窩、微蜂窩以及室內(nèi)傳播模型。為此，對主要的預測模型進行了綜述，討論了其優(yōu)點及不足。此外，介紹了對這些模型的一些實用化改進以及一些新模型。PropagationPhenomena傳播現(xiàn)象傳播現(xiàn)象Propagationmechanismsareverycompl

17、exdiverse.Firstbecauseoftheseparationbetweenthereceiverthetransmitterattenuationofthesignalstrengthoccurs.Inadditionthesignalpropagatesbymeansofdiffractionscatteringreflectiontransmissionrefractionetc.傳播機制復雜而多變。首先，源于收發(fā)信機

18、的分離，信號的強度出現(xiàn)了傳播衰減。此外，信號通過繞射、散射、反射、透射、折射等方式進行傳播。Diffractionoccurswhenthedirectlineofsight(LoS)propagationbetweenthetransmitterthereceiverisobstructedbyanopaqueobstaclewhosedimensionsareconsiderablylargerthanthesignalwavele

19、ngth.Thediffractionoccursattheobstacleedgeswheretheradiowavesarescatteredasaresulttheyareadditionallyattenuated.ThediffractionmechanismallowsthereceptionofradiosignalswhentheLoSconditionsarenotsatisfied(NLoScase)whetheri

20、nurbanruralenvironments.當尺寸遠大于信號波長的（對電磁波）不透明的物體遮擋了收發(fā)信機之間的直達射線路徑時，會出現(xiàn)繞射現(xiàn)象。繞射出現(xiàn)在物體的邊緣，電磁波被散射開來，其結(jié)果導致額外的信號衰減。不管是在城市或農(nóng)村環(huán)境中，繞射機制使得在不滿足直達射線的條件下（無直達射線情形）也可以接收無線信號。Scatteringoccurswhenthepropagationpathcontainstheobstacleswhosed

21、imensionsarecomparabletothewavelength.Thenatureofthisphenomenonissimilartothediffractionexceptthattheradiowavesarescatteredinagreaternumberofdirections.Ofallthementionedeffectsscatteringisthemostdifficulttobepredicted.當傳

22、播路徑上有其尺寸可以和信號波長相比擬的（若干）物體時，出現(xiàn)散射現(xiàn)象。這一現(xiàn)象的特性類似于繞射，只是電磁波向更多的方向上散開。在前所提及的所有現(xiàn)象中，散射是最難預測的。Reflectionoccurswhentheradiowaveimpingestheobstaclewhosedimensionsareconsiderablylargerthanthewavelengthoftheincidentwave.Areflectedwavec