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1、,CDMA课堂之移动通信发展 和CDMA基本原理,2,移动通信的发展,AMPS,TACS,其它,第一代 80年代,模拟,模,拟,技,术,GSM,第二代 90年代,数字,需求驱动,数,字,技,术,语,音,业,务,第三代,IMT-2000,UMTS,WCDMA,CDMA,2000,需求驱动,宽,带,业,务,TD- SCDMA,第三代移动通信系统,IMT-2000 2000年在2000M频段实现2000K的数据通信IMT2000推荐的3种制式WCDMA 欧洲 CDMA2000 美国 TD-SCDMA 中国3G对数据通信速率的要求 室内环境至少2Mbps 室内外步行环境至少384kbps 室外车辆运动
2、中至少144kbps,主流技术：WCDMACDMA2000TD-SCDMA,3G,3G的发展概况,3G的演进,移动通信的发展,CDMA2000标准家族演进,CDMA2000 1x Rel 0,CDMA2000 1x Rel A,CDMA2000 1x Rel B,CDMA2000 1x Rel C,1999 2000 2002 2003 2004,2000,TIA/EIA-95-B,1995 1999,CDMA2000 1x Rel D,CDMA2000 HRPD Rev A,“1xEV-DV”,“1xEV-DO”,CDMA2000 HRPD Rev B,2004,2006,CDMA2000
3、1X 网络结构,多径环境,衰落示意图,纠错编码技术,纠错编码技术是在发射端按一定规则引入冗余信息， 从而使得即使空中传输引入了误码，也能利用冗余 信息将此错误纠正回来的技术。,在通信系统中，为了减少突发干扰对连续数据造成的大面积差错，常采用交织 来将突发干扰造成的连续差错化解为随机独立差错，使其适合于译码器的错误纠正。,交织技术,多址技术,几种流行的多址技术： FDMA 频分多址 每个用户使用不同的频率 一个信道对应一个频率 TDMA 时分多址 每个用户使用不同的时隙 一个信道就是特定频率的特定时隙 CDMA 码分多址 一个信道对应一种独特的码序列。 每个用户使用相同的频率，但采用不同的码序列
4、。,多址技术：多个独立用户同时使用传输介质而互不影响。,扩频通信的定义,扩展频谱（SS:Spread Spectrum)通信简称扩频通信。扩频通信技术:在发端采用扩频码调制，使信号所占的频带宽度远大于所传信息必须的带宽，在收端采用相同的扩频码进行相关解调来解扩以恢复所传信息数据。,结论：在信道容量C不变的情况下，信号频带宽度B与信噪比S/N完全可以互相交换，即可以通过增大传输系统的带宽以在较低信噪比的条件下获得比较满意的传输质量,扩频通信的理论基础,CDMA扩频原理,CDMA扩频原理,CDMA扩频原理,Interference Sources,Long & Short Code Spreadi
5、ng,Encoding & Interleaving,Long & Short Code Correlator,Decode & Deinterleaving,Baseband Data,Baseband Data,Background Noise,External Interference,Other Cell Interference,Other User Noise,384 kbps,1152 kbps,4.096 mcps,4.096 mcps,1152 kbps,384 kbps,CDMA Transmitter,CDMA Receiver,5 MHz BW,f,c,5 MHz BW
6、,f,c,390 kHz BW,0,390 kHz BW,0,5 MHz BW,5 MHz BW,-100 dB/Hz,Spurious Signals,CDMA扩频原理,CDMA扩频原理,扩频通信的特点和分类,隐蔽性和保密性好 多个用户可以同时占用相同频带,实现多址 抗衰落、抗多径干扰 抗干扰能力强,CDMA扩频码的选择,扩频码速率：1.2288Mcps； 扩频码：前向为Walsh码和PN短码，反向为PN长码。,扩频码的使用是扩频通信的关键点,Walsh码的定义:,Walsh码的定义,Walsh函数是一种非正弦波的完备正交函数系统，可用哈达玛矩阵H通过递推关系构成。由于它仅有可能的取值是1和
7、1（或0和1），比较适合于用来表达和处理数字信号。Walsh函数具有理想的互相关特性。在Walsh函数中，两两之间的互相关函数为“0”，亦即它们之间是正交的。,Code #23 0110100101101001100101101001011001101001011010011001011010010110 (Code #23) 1001011010010110011010010110100110010110100101100110100101101001Code #59 01100110100110011001100101100110100110010110011001100110100110
8、01,正交与相关性,WALSH CODES# - 64-Chip Sequence -0 00000000000000000000000000000000000000000000000000000000000000001 01010101010101010101010101010101010101010101010101010101010101012 00110011001100110011001100110011001100110011001100110011001100113 011001100110011001100110011001100110011001100110011001100
9、11001104 00001111000011110000111100001111000011110000111100001111000011115 01011010010110100101101001011010010110100101101001011010010110106 00111100001111000011110000111100001111000011110000111100001111007 01101001011010010110100101101001011010010110100101101001011010018 000000001111111100000000111
10、11111000000001111111100000000111111119 0101010110101010010101011010101001010101101010100101010110101010 10 0011001111001100001100111100110000110011110011000011001111001100 11 0110011010011001011001101001100101100110100110010110011010011001 12 000011111111000000001111111100000000111111110000000011111
11、1110000 13 0101101010100101010110101010010101011010101001010101101010100101 14 0011110011000011001111001100001100111100110000110011110011000011 15 0110100110010110011010011001011001101001100101100110100110010110 16 0000000000000000111111111111111100000000000000001111111111111111 17 01010101010101011
12、01010101010101001010101010101011010101010101010 18 0011001100110011110011001100110000110011001100111100110011001100 19 0110011001100110100110011001100101100110011001101001100110011001 20 0000111100001111111100001111000000001111000011111111000011110000 21 010110100101101010100101101001010101101001011
13、0101010010110100101 22 0011110000111100110000111100001100111100001111001100001111000011 23 0110100101101001100101101001011001101001011010011001011010010110 24 0000000011111111111111110000000000000000111111111111111100000000 25 0101010110101010101010100101010101010101101010101010101001010101 26 00110
14、01111001100110011000011001100110011110011001100110000110011 27 0110011010011001100110010110011001100110100110011001100101100110 28 0000111111110000111100000000111100001111111100001111000000001111 29 0101101010100101101001010101101001011010101001011010010101011010 30 001111001100001111000011001111000
15、0111100110000111100001100111100 31 0110100110010110100101100110100101101001100101101001011001101001 32 0000000000000000000000000000000011111111111111111111111111111111 33 0101010101010101010101010101010110101010101010101010101010101010 34 0011001100110011001100110011001111001100110011001100110011001
16、100 35 0110011001100110011001100110011010011001100110011001100110011001 36 0000111100001111000011110000111111110000111100001111000011110000 37 0101101001011010010110100101101010100101101001011010010110100101 38 0011110000111100001111000011110011000011110000111100001111000011 39 011010010110100101101
17、0010110100110010110100101101001011010010110 40 0000000011111111000000001111111111111111000000001111111100000000 41 0101010110101010010101011010101010101010010101011010101001010101 42 0011001111001100001100111100110011001100001100111100110000110011 43 0110011010011001011001101001100110011001011001101
18、001100101100110 44 0000111111110000000011111111000011110000000011111111000000001111 45 0101101010100101010110101010010110100101010110101010010101011010 46 0011110011000011001111001100001111000011001111001100001100111100 47 0110100110010110011010011001011010010110011010011001011001101001 48 000000000
19、0000000111111111111111111111111111111110000000000000000 49 0101010101010101101010101010101010101010101010100101010101010101 50 0011001100110011110011001100110011001100110011000011001100110011 51 0110011001100110100110011001100110011001100110010110011001100110 52 0000111100001111111100001111000011110
20、000111100000000111100001111 53 0101101001011010101001011010010110100101101001010101101001011010 54 0011110000111100110000111100001111000011110000110011110000111100 55 0110100101101001100101101001011010010110100101100110100101101001 56 0000000011111111111111110000000011111111000000000000000011111111
21、57 0101010110101010101010100101010110101010010101010101010110101010 58 0011001111001100110011000011001111001100001100110011001111001100 59 0110011010011001100110010110011010011001011001100110011010011001 60 0000111111110000111100000000111111110000000011110000111111110000 61 0101101010100101101001010101101010100101010110100101101010100101 62 0011110011000011110000110011110011000011001111000011110011000011 63 0110100110010110100101100110100110010110011010010110100110010110,
