1、CDMA課堂之移動(dòng)通信發(fā)展和CDMA基本原理2移動(dòng)通信的發(fā)展AMPSTACS其它第一代 80年代模擬模擬技術(shù)GSMCDMA IS95第二代 90年代數(shù)字需求驅(qū)動(dòng)數(shù)字技術(shù)語(yǔ)音業(yè)務(wù)第三代 IMT-2000UMTSWCDMACDMA2000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-2000 2000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(guó) TD-SCDMA 中國(guó)3G對(duì)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)： WCDMA CDMA2000 T

2、D-SCDMA 3G3G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)CDMA20001xRel 0CDMA20001xRel ACDMA20001xRel BCDMA20001xRel C 1999 2000 2002 2003 2004CDMA2000HRPDRev 0 2000IS-95-ATIA/EIA-95-B1995 1999CDMA20001xRel DCDMA2000 HRPDRev A“1xEV-DV”“1xEV-DO”CDMA2000 HRPDRev B 2004 2006 CDMA2000 1X 網(wǎng)絡(luò)結(jié)構(gòu)時(shí)間接收信號(hào)強(qiáng)度發(fā)射信號(hào)多徑環(huán)境距離(m)接收功率(

3、dBm)102030-20-40-60慢衰落快衰落衰落示意圖無糾錯(cuò)編碼： BER10-1 10-2不能滿足通信需要卷積編碼： BER10-3滿足語(yǔ)音通信需要Turbo 碼： BER10-6滿足數(shù)據(jù)通信需要糾錯(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(duì)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)FrequencyTimePowerFrequencyTimePowerFrequencyTimePowerFDM

4、ATDMACDMA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(duì)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(duì)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:Spread Spectrum)通信簡(jiǎn)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(hào)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)。理論基礎(chǔ)Shanon公式 C=B*log2(1+S/N

5、)C：信道容量，單位b/s B：信號(hào)頻帶寬度，單位HzS：信號(hào)平均功率，單位WN：噪聲平均功率，單位W結(jié)論：在信道容量C不變的情況下，信號(hào)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)1.25 MHz30 KHzPower is “Spread” Over a Larger BandwidthCDMA擴(kuò)頻原理Many code channels are individually“spread” and then added together tocreate a “composite signal”CDMA擴(kuò)

6、頻原理UNWANTED POWERFROM OTHER SOURCESUsing the “right” mathematicalsequences any Code Channelcan be extracted from the receivedcomposite signalCDMA擴(kuò)頻原理Interference SourcesLong & Short CodeSpreadingEncoding &InterleavingLong & Short CodeCorrelatorDecode &DeinterleavingBasebandDataBasebandDataBackground

7、 NoiseExternal InterferenceOther Cell InterferenceOther User Noise384 kbps1152 kbps4.096 mcps4.096 mcps1152 kbps384 kbpsCDMA TransmitterCDMA Receiver5 MHz BW fc5 MHz BW fc390 kHz BW0390 kHz BW05 MHz BW fc5 MHz BW fcfc-100 dB/Hz fcSpurious Signals 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

8、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(zhǎng)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(hào)。 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 #23 011010010110100110010110100101100110100101101001100

9、1011010010110(Code #23) 1001011010010110011010010110100110010110100101100110100101101001 Code #59 0110011010011001100110010110011010011001011001100110011010011001PARALLELXOR: all 0s相關(guān)性: 100%(100% match)ORTHOGONALXOR: half 0s, half 1s相關(guān)性: 0%(50% match, 50% no-match)ANTI-PARALLELXOR: all 1s相關(guān)性: 100%(1

10、00% no-match)#23#23(#23)#23#23#59正交與相關(guān)性WALSH CODES # - 64-Chip Sequence - 0 0000000000000000000000000000000000000000000000000000000000000000 1 0101010101010101010101010101010101010101010101010101010101010101 2 0011001100110011001100110011001100110011001100110011001100110011 3 01100110011001100110011

11、00110011001100110011001100110011001100110 4 0000111100001111000011110000111100001111000011110000111100001111 5 0101101001011010010110100101101001011010010110100101101001011010 6 0011110000111100001111000011110000111100001111000011110000111100 7 0110100101101001011010010110100101101001011010010110100

12、101101001 8 0000000011111111000000001111111100000000111111110000000011111111 9 010101011010101001010101101010100101010110101010010101011010101010 001100111100110000110011110011000011001111001100001100111100110011 011001101001100101100110100110010110011010011001011001101001100112 00001111111100000000

13、1111111100000000111111110000000011111111000013 010110101010010101011010101001010101101010100101010110101010010114 001111001100001100111100110000110011110011000011001111001100001115 011010011001011001101001100101100110100110010110011010011001011016 0000000000000000111111111111111100000000000000001111

14、11111111111117 010101010101010110101010101010100101010101010101101010101010101018 001100110011001111001100110011000011001100110011110011001100110019 011001100110011010011001100110010110011001100110100110011001100120 000011110000111111110000111100000000111100001111111100001111000021 01011010010110101

15、0100101101001010101101001011010101001011010010122 001111000011110011000011110000110011110000111100110000111100001123 011010010110100110010110100101100110100101101001100101101001011024 000000001111111111111111000000000000000011111111111111110000000025 0101010110101010101010100101010101010101101010101

16、01010100101010126 001100111100110011001100001100110011001111001100110011000011001127 011001101001100110011001011001100110011010011001100110010110011028 000011111111000011110000000011110000111111110000111100000000111129 010110101010010110100101010110100101101010100101101001010101101030 00111100110000

17、1111000011001111000011110011000011110000110011110031 011010011001011010010110011010010110100110010110100101100110100132 000000000000000000000000000000001111111111111111111111111111111133 010101010101010101010101010101011010101010101010101010101010101034 0011001100110011001100110011001111001100110011

18、00110011001100110035 011001100110011001100110011001101001100110011001100110011001100136 000011110000111100001111000011111111000011110000111100001111000037 010110100101101001011010010110101010010110100101101001011010010138 001111000011110000111100001111001100001111000011110000111100001139 01101001011

19、0100101101001011010011001011010010110100101101001011040 000000001111111100000000111111111111111100000000111111110000000041 010101011010101001010101101010101010101001010101101010100101010142 001100111100110000110011110011001100110000110011110011000011001143 0110011010011001011001101001100110011001011

20、00110100110010110011044 000011111111000000001111111100001111000000001111111100000000111145 010110101010010101011010101001011010010101011010101001010101101046 001111001100001100111100110000111100001100111100110000110011110047 011010011001011001101001100101101001011001101001100101100110100148 00000000

21、0000000011111111111111111111111111111111000000000000000049 010101010101010110101010101010101010101010101010010101010101010150 001100110011001111001100110011001100110011001100001100110011001151 011001100110011010011001100110011001100110011001011001100110011052 0000111100001111111100001111000011110000

22、11110000000011110000111153 010110100101101010100101101001011010010110100101010110100101101054 001111000011110011000011110000111100001111000011001111000011110055 011010010110100110010110100101101001011010010110011010010110100156 000000001111111111111111000000001111111100000000000000001111111157 01010

23、1011010101010101010010101011010101001010101010101011010101058 001100111100110011001100001100111100110000110011001100111100110059 011001101001100110011001011001101001100101100110011001101001100160 000011111111000011110000000011111111000000001111000011111111000061 010110101010010110100101010110101010010101011010010110101010010162 001111001100001111000011001111001100001100111100001111001100001163 0110100110010110100101100110100110010110011010010110100110010110Walsh碼 CDMA中:用64階Walsh函數(shù)進(jìn)行前向擴(kuò)頻，區(qū)分扇區(qū)內(nèi)前向碼分信道,反向做正交