cdma.rar_CDMARAKE_IS-95cdma_dscdma_rakeCDMA_匹配滤波CDMA资源-CSDN文库

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CDMA（码分多址）是一种无线通信技术，它通过使用独特的编码序列来区分不同的用户，使得多个用户可以在相同的频率上同时传输数据，从而提高了频谱效率。在IS-95标准中，CDMA被广泛应用于前向链路系统，也就是基站到移动设备的数据传输。在IS-95 CDMA系统中，前向链路仿真涵盖了几个关键的通信模块： 1. **扩频调制**：扩频调制是CDMA的核心技术之一。每个用户的信号会被一个长的伪随机码序列（PN序列）所扩频，使得信号在整个可用带宽内均匀分布。这种技术增强了抗干扰能力，并使得多个用户的信号能够在频域和时域上重叠而不会相互干扰。 2. **匹配滤波**：在接收端，匹配滤波器是用于提取特定用户信号的关键部件。它设计为与发送端的PN序列相匹配，以便最大程度地提高信号对噪声比（SNR），并减小多径衰落的影响。匹配滤波器能够优化接收性能，尤其是在多径传播环境下。 3. **RAKE接收**：RAKE接收机是CDMA系统中的另一重要组件，尤其在处理多径传播问题时。由于无线信号可以通过多个路径到达接收端，这些信号可能会因为不同路径长度而产生时间延迟，形成多个信号副本或“指”。RAKE接收机通过多个“指”进行接收，合并这些副本的能量，从而改善接收质量。在"IS-95_仿真源程序.doc"文件中，我们可以期待找到实现这些通信模块的源代码，这将有助于理解CDMA系统的具体工作原理和算法。通过这样的仿真，研究人员和工程师可以测试不同的系统参数，优化性能，以及分析在不同环境条件下的系统行为。 IS-95标准是CDMA技术的早期版本，后续的3G和4G标准如EV-DO和WCDMA在IS-95的基础上进行了改进和扩展，但基本的扩频、匹配滤波和RAKE接收等核心概念依然保留。这些基础知识对于理解现代无线通信系统至关重要，尤其是在设计和分析多用户共享频谱资源的场景下。

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IS-95_仿真源程序.doc 91KB

%main_IS95_forward.m

%此函数用于 IS-95 前向链路系统的仿真，包括扩

%频调制，匹配滤波，RAKE 接收等相关通信模块。

%仿真环境: 加性高斯白噪声信道.

%数据速率 = 9600 KBps

clear all

close all

clc

disp('--------------start-------------------');

global Zi Zq Zs show R Gi Gq

clear j;

show = 0;

SD = 0; % 选择软/硬判决接收

%-------------------主要的仿真参数设置------------------

BitRate = 9600;

ChipRate = 1228800;

N = 184;

MFType = 1; % 匹配滤波器类型--升余弦

R = 5;

%+++++++++++++++++++Viterbi 生成多项式++++++++++++++++++

G_Vit = [1 1 1 1 0 1 0 1 1; 1 0 1 1 1 0 0 0 1];

K = size(G_Vit, 2);

L = size(G_Vit, 1);

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%++++++++++++++++++++++Walsh 矩阵++++++++++++++++++++++++

WLen = 64;

Walsh = reshape([1;0]*ones(1, WLen/2), WLen , 1);

%Walsh = zeros(WLen ,1);

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%++++++++++++++++++扩频调制 PN 码的生成多项式++++++++++++++

%Gi = [ 1 0 1 0 0 0 1 1 1 0 1 0 0 0 0 1]';

%Gq = [ 1 0 0 1 1 1 0 0 0 1 1 1 1 0 0 1]';

Gi_ind = [15, 13, 9, 8, 7, 5, 0]';

Gq_ind = [15, 12, 11, 10, 6, 5, 4, 3, 0]';

Gi = zeros(16, 1);

Gi(16-Gi_ind) = ones(size(Gi_ind));

Zi = [zeros(length(Gi)-1, 1); 1];

% I 路信道 PN 码生成器的初始状态

Gq = zeros(16, 1);

Gq(16-Gq_ind) = ones(size(Gq_ind));

Zq = [zeros(length(Gq)-1, 1); 1];

% Q 路信道 PN 码生成器的初始状态

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%+++++++++++++++++++扰码生成多项式++++++++++++++++++++++

Gs_ind = [42, 35, 33, 31, 27, 26, 25, 22, 21, 19, 18, 17, 16, 10, 7, 6, 5, 3, 2, 1, 0]';

Gs = zeros(43, 1);

Gs(43-Gs_ind) = ones(size(Gs_ind));

Zs = [zeros(length(Gs)-1, 1); 1];

% 长序列生成器的初始状态

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%++++++++++++++++++++++AWGN 信道++++++++++++++++++++++++

EbEc = 10*log10(ChipRate/BitRate);

EbEcVit = 10*log10(L);

EbNo = [-2 : 0.5 : 6.5]; %仿真信噪比范围(dB)

% EbNo = [2 : 0.5 : 2.5];

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%------------------------------------------------------

%-------------------------主程序-------------------------

ErrorsB = []; ErrorsC = []; NN = [];

if (SD == 1)

fprintf('\n SOFT Decision Viterbi Decoder\n\n');

else

fprintf('\n HARD Decision Viterbi Decoder\n\n');

end

for i=1:length(EbNo)

fprintf('\nProcessing %1.1f (dB)', EbNo(i));

iter = 0; ErrB = 0; ErrC = 0;

while (ErrB <300) & (iter <150)

drawnow;

%++++++++++++++++++++++发射机+++++++++++++++++++++++

TxData = (randn(N, 1)>0);

% 速率为 19.2Kcps

[TxChips, Scrambler] = PacketBuilder(TxData, G_Vit, Gs);

% 速率为 1.2288Mcps

[x PN MF] = Modulator(TxChips, MFType, Walsh);

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%++++++++++++++++++++++++信道+++++++++++++++++++++++++++

noise = 1/sqrt(2)*sqrt(R/2)*( randn(size(x)) + j*randn(size(x)))*10^(-(EbNo(i) -

EbEc)/20);

r = x+noise;

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

%+++++++++++++++++++++++++接收机++++++++++++++++++++++++

RxSD = Demodulator(r, PN, MF, Walsh); %软判决，速率为 19.2 Kcps

RxHD = (RxSD>0); % 定义接收码片的硬判决

if (SD)

[RxData Metric]= ReceiverSD(RxSD, G_Vit, Scrambler); %软判决

else

[RxData Metric]= ReceiverHD(RxHD, G_Vit, Scrambler); %硬判决

end

%++++++++++++++++++++++++++++++++++++++++++++++++++++++

if(show)

subplot(311); plot(RxSD, '-o'); title('Soft Decisions');

subplot(312); plot(xor(TxChips, RxHD), '-o'); title('Chip Errors');

subplot(313); plot(xor(TxData, RxData), '-o');

title(['Data Bit Errors. Metric = ', num2str(Metric)]);

pause;

end

if(mod(iter, 50)==0)

fprintf('.');

save TempResults ErrB ErrC N iter

end

ErrB = ErrB + sum(xor(RxData, TxData));

ErrC = ErrC + sum(xor(RxHD, TxChips));

iter = iter+ 1;

end

ErrorsB = [ErrorsB; ErrB];

ErrorsC = [ErrorsC; ErrC];

NN = [NN; N*iter];

save SimData *

end

%+++++++++++++++++++++++++误码率计算++++++++++++++++++++++++

PerrB = ErrorsB./NN;

%PerrB1 = ErrorsB1./NN1;

PerrC = ErrorsC./NN;

Pbpsk= 1/2*erfc(sqrt(10.^(EbNo/10)));

PcVit= 1/2*erfc(sqrt(10.^((EbNo-EbEcVit)/10)));

Pc = 1/2*erfc(sqrt(10.^((EbNo-EbEc)/10)));

%+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

%%+++++++++++++++++++++++++性能仿真显示++++++++++++++++++++++

figure;

semilogy(EbNo(1:length(PerrB)), PerrB, 'b-*'); hold on;

% %semilogy(EbNo(1:length(PerrB1)), PerrB1, 'k-o'); hold on;

% semilogy(EbNo(1:length(PerrC)), PerrC, 'b-o'); grid on;

% semilogy(EbNo, Pbpsk, 'b-.^');

% %semilogy(EbNo, PcVit, 'k-.x'); ylabel('BER');

% semilogy(EbNo, Pc, 'b-.x');

xlabel('信噪比/dB');

ylabel('误码率');

grid on;

% legend('Pb of System (HD)', 'Pb of System (SD)', 'Pc before Viterbi of System',

% ... 'Pb of BPSK with no Viterbi (theory)', 'Pc on Receiver (theory)');

% legend('Pb of System', 'Pc before Viterbi of System', ...

%'Pb of BPSK with no Viterbi (theory)',

%'Pc before Viterbi (theory)', 'Pc on Receiver (theory)');

%+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

disp('--------------end-------------------');

%------------------------------------------------------

% ************************beginning of file*****************************

%PacketBuilder.m

function [ChipsOut, Scrambler] = PacketBuilder(DataBits, G, Gs);

%此函数用于产生 IS-95 前向链路系统的发送数据包

%+++++++++++++++++++++++variables++++++++++++++++++++++++++++

% DataBits 发送数据（二进制形式）

% G Viterbi 编码生成多项式

% Gs 长序列生成多项式（扰码生成多项式）

% ChipsOut 输入到调制器的码序列（二进制形式）

% Scrambler 扰码

%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

global Zs

K = size(G, 2);

L = size(G, 1);

N = 64*L*(length(DataBits)+K-1);% 码片数 (9.6 Kbps -> 1.288 Mbps)

chips = VitEnc(G, [DataBits; zeros(K-1,1)]);% Viterbi 编码

% 交织编码

INTERL = reshape(chips, 24, 16); % IN：列, OUT：行

chips = reshape(INTERL', length(chips), 1); %速率=19.2 KBps

% 产生扰码

[LongSeq Zs] = PNGen(Gs, Zs, N);

Scrambler = LongSeq(1:64:end);

ChipsOut = xor(chips, Scrambler);

%************************end of file***********************************

% ************************beginning of file*****************************

%VitEnc.m

function y = VitEnc(G, x);

% 此函数根据生成多项式进行 Viterbi 编码

%+++++++++++++++++++++++variables++++++++++++++++++++++++++++

% G 生成多项式的矩阵

% x 输入数据（二进制形式）

% y Viterbi 编码输出序列

%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

K = size(G, 1);

L = length(x);

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