ch_17 wireless 02new

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1、无线通信:第二讲Ø概述Ø蜂窝移动通的结构ØGSM移动通信系统ØCDMA数字移动通信系统Ø公用移动通信网的数据业务Ø第三代(3G)移动通信系统综述Ø3G移动通信系统的无线传输技术(RTT)Ø第三代(3G)移动通信系统的核心网参考书:李伟章,现代通信网概论,人民邮电出版社,2003111/9/2006WirelessCommunicationsLecture02PDFcreatedwithpdfFactorytrialversionwww.pdffactory.comCDMA数字移动通信系统ØCDMA的基本原理

2、ØCDMA的多址码技术ØIS-95无线信道结构ØIS-95系统的逻辑信道划分ØIS-95系统通信控制过程ØCDMA技术的主要优点211/9/2006WirelessCommunicationsLecture02PDFcreatedwithpdfFactorytrialversionwww.pdffactory.comFDMA与TDMA的缺点•信道数量是固定有限的•处理频率的干扰ü来自同一频道ü来自相邻频道•切换时的困难311/9/2006WirelessCommunicationsLecture02PDFc

3、reatedwithpdfFactorytrialversionwww.pdffactory.comCo-ChannelInterference•Co-ChannelInterference415237415isafunctionofQ=D/R2637452637•WhenQgoesup,co-4152674152channelinterference6374126374goesdown1526341526•NotethatCo-Channel3741563741Interferencecomesfrom2

4、637152636directions.415237415st6374•OKtocountonly1Tier2637nd156andignore2Tier4•Signal-to-Interference,RDS/Igreaterthan18dbfor7-cellreuse.411/9/2006WirelessCommunicationsLecture02PDFcreatedwithpdfFactorytrialversionwww.pdffactory.comCo-ChannelInterferenceDR

5、NormalCaseofCo-ChannelInterferenceinanOmnidirectionalAntennaSystemD-RRWorstCase511/9/2006WirelessCommunicationsLecture02PDFcreatedwithpdfFactorytrialversionwww.pdffactory.comDirectionalAntennaSystem1200Divideacellinto3sectorsusingdirectionalantenna1526syst

6、ems.74153741CellAreceivesinterference2637fromthe2leftshaded52634152cells,butnotviceversa.7156374S/Iismuchbetterthan263718dB,reducingco-channel15264152interference.3741Samecaseifusing60degree6374beamdirectionalantenna611/9/2006WirelessCommunicationsLecture0

7、2PDFcreatedwithpdfFactorytrialversionwww.pdffactory.comAdjacentChannelInterferenceNear-End-to-Far-EndInterferenceNearendMSwillinterferetheFarEndMS,ifthereisnotenoughbandseparation.S/I=(D1/D2)-4=(10/.25)-4=-64dB,Aminimumseparationof4channelsisneededtosatisf

8、yanisolationcriterionof64dB.711/9/2006WirelessCommunicationsLecture02PDFcreatedwithpdfFactorytrialversionwww.pdffactory.comMultipleAccessSchemes811/9/2006WirelessCommunicationsLecture02PDFcreatedwithpdfFactor