,移動(dòng)通信發(fā)展和CDMA基本原理,2,移動(dòng)通信的發(fā)展,AMPS,TACS,其它,第一代80年代,模擬,模,擬,技,術(shù),GSM,第二代90年代,數(shù)字,需求驅(qū)動(dòng),數(shù),字,技,術(shù),語,音,業(yè),務(wù),第三代,IMT-2000,UMTS,WCDMA,CDMA,2000,需求驅(qū)動(dòng),寬,帶,業(yè),務(wù),TD-SCDMA,第三代移動(dòng)通信系統(tǒng),IMT-20002000年在2000M頻段實(shí)現(xiàn)2000K的數(shù)據(jù)通信IMT2000推薦的3種制式WCDMA歐洲CDMA2000美國TD-SCDMA中國3G對數(shù)據(jù)通信速率的要求室內(nèi)環(huán)境至少2Mbps室內(nèi)外步行環(huán)境至少384kbps室外車輛運(yùn)動(dòng)中至少144kbps,主流技術(shù)：WCDMACDMA2000TD-SCDMA,3G,3G的發(fā)展概況,3G的演進(jìn),移動(dòng)通信的發(fā)展,CDMA2000標(biāo)準(zhǔn)家族演進(jìn),CDMA20001xRel0,CDMA20001xRelA,CDMA20001xRelB,CDMA20001xRelC,19992000200220032004,2000,TIA/EIA-95-B,19951999,CDMA20001xRelD,CDMA2000HRPDRevA,“1xEV-DV”,“1xEV-DO”,CDMA2000HRPDRevB,2004,2006,CDMA20001X網(wǎng)絡(luò)結(jié)構(gòu),多徑環(huán)境,衰落示意圖,糾錯(cuò)編碼技術(shù),糾錯(cuò)編碼技術(shù)是在發(fā)射端按一定規(guī)則引入冗余信息，從而使得即使空中傳輸引入了誤碼，也能利用冗余信息將此錯(cuò)誤糾正回來的技術(shù)。,在通信系統(tǒng)中，為了減少突發(fā)干擾對連續(xù)數(shù)據(jù)造成的大面積差錯(cuò)，常采用交織來將突發(fā)干擾造成的連續(xù)差錯(cuò)化解為隨機(jī)獨(dú)立差錯(cuò)，使其適合于譯碼器的錯(cuò)誤糾正。,交織技術(shù),多址技術(shù),幾種流行的多址技術(shù)：FDMA頻分多址每個(gè)用戶使用不同的頻率一個(gè)信道對應(yīng)一個(gè)頻率TDMA時(shí)分多址每個(gè)用戶使用不同的時(shí)隙一個(gè)信道就是特定頻率的特定時(shí)隙CDMA碼分多址一個(gè)信道對應(yīng)一種獨(dú)特的碼序列。每個(gè)用戶使用相同的頻率，但采用不同的碼序列。,多址技術(shù)：多個(gè)獨(dú)立用戶同時(shí)使用傳輸介質(zhì)而互不影響。,擴(kuò)頻通信的定義,擴(kuò)展頻譜（SS:SpreadSpectrum)通信簡稱擴(kuò)頻通信。擴(kuò)頻通信技術(shù):在發(fā)端采用擴(kuò)頻碼調(diào)制，使信號所占的頻帶寬度遠(yuǎn)大于所傳信息必須的帶寬，在收端采用相同的擴(kuò)頻碼進(jìn)行相關(guān)解調(diào)來解擴(kuò)以恢復(fù)所傳信息數(shù)據(jù)。,結(jié)論：在信道容量C不變的情況下，信號頻帶寬度B與信噪比S/N完全可以互相交換，即可以通過增大傳輸系統(tǒng)的帶寬以在較低信噪比的條件下獲得比較滿意的傳輸質(zhì)量,擴(kuò)頻通信的理論基礎(chǔ),CDMA擴(kuò)頻原理,CDMA擴(kuò)頻原理,CDMA擴(kuò)頻原理,InterferenceSources,Long&ShortCodeSpreading,Encoding&Interleaving,Long&ShortCodeCorrelator,Decode&Deinterleaving,BasebandData,BasebandData,BackgroundNoise,ExternalInterference,OtherCellInterference,OtherUserNoise,384kbps,1152kbps,4.096mcps,4.096mcps,1152kbps,384kbps,CDMATransmitter,CDMAReceiver,5MHzBW,f,c,5MHzBW,f,c,390kHzBW,0,390kHzBW,0,5MHzBW,5MHzBW,-100dB/Hz,SpuriousSignals,CDMA擴(kuò)頻原理,CDMA擴(kuò)頻原理,擴(kuò)頻通信的特點(diǎn)和分類,隱蔽性和保密性好多個(gè)用戶可以同時(shí)占用相同頻帶,實(shí)現(xiàn)多址抗衰落、抗多徑干擾抗干擾能力強(qiáng),CDMA擴(kuò)頻碼的選擇,擴(kuò)頻碼速率：1.2288Mcps；擴(kuò)頻碼：前向?yàn)閃alsh碼和PN短碼，反向?yàn)镻N長碼。,擴(kuò)頻碼的使用是擴(kuò)頻通信的關(guān)鍵點(diǎn),Walsh碼的定義:,Walsh碼的定義,Walsh函數(shù)是一種非正弦波的完備正交函數(shù)系統(tǒng)，可用哈達(dá)瑪矩陣H通過遞推關(guān)系構(gòu)成。由于它僅有可能的取值是1和1（或0和1），比較適合于用來表達(dá)和處理數(shù)字信號。Walsh函數(shù)具有理想的互相關(guān)特性。在Walsh函數(shù)中，兩兩之間的互相關(guān)函數(shù)為“0”，亦即它們之間是正交的。,Code#230110100101101001100101101001011001101001011010011001011010010110(Code#23)1001011010010110011010010110100110010110100101100110100101101001Code#590110011010011001100110010110011010011001011001100110011010011001,正交與相關(guān)性,WALSHCODES#-64-ChipSequence-000000000000000000000000000000000000000000000000000000000000000001010101010101010101010101010101010101010101010101010101010101010120011001100110011001100110011001100110011001100110011001100110011301100110011001100110011001100110011001100110011001100110011001104000011110000111100001111000011110000111100001111000011110000111150101101001011010010110100101101001011010010110100101101001011010600111100001111000011110000111100001111000011110000111100001111007011010010110100101101001011010010110100101101001011010010110100180000000011111111000000001111111100000000111111110000000011111111901010101101010100101010110101010010101011010101001010101101010101000110011110011000011001111001100001100111100110000110011110011001101100110100110010110011010011001011001101001100101100110100110011200001111111100000000111111110000000011111111000000001111111100001301011010101001010101101010100101010110101010010101011010101001011400111100110000110011110011000011001111001100001100111100110000111501101001100101100110100110010110011010011001011001101001100101101600000000000000001111111111111111000000000000000011111111111111111701010101010101011010101010101010010101010101010110101010101010101800110011001100111100110011001100001100110011001111001100110011001901100110011001101001100110011001011001100110011010011001100110012000001111000011111111000011110000000011110000111111110000111100002101011010010110101010010110100101010110100101101010100101101001012200111100001111001100001111000011001111000011110011000011110000112301101001011010011001011010010110011010010110100110010110100101102400000000111111111111111100000000000000001111111111111111000000002501010101101010101010101001010101010101011010101010101010010101012600110011110011001100110000110011001100111100110011001100001100112701100110100110011001100101100110011001101001100110011001011001102800001111111100001111000000001111000011111111000011110000000011112901011010101001011010010101011010010110101010010110100101010110103000111100110000111100001100111100001111001100001111000011001111003101101001100101101001011001101001011010011001011010010110011010013200000000000000000000000000000000111111111111111111111111111111113301010101010101010101010101010101101010101010101010101010101010103400110011001100110011001100110011110011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