data_generator.m

数字音频信号的调制与解调的源码程序.可保证声音信号怒失真输出

%测试文件，一次性生成数个data symbol，按标准方法调制，组装成待发送信号
%目的是快捷地调试解调模块，尤其是sync的部分
%原先worked的一组数据s_1 s_2 s_3，原封不动地保存

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%                                    定义参数                                   %
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n_data=4;              %本程序产生的数据symbol个数
Tu=2048;               %for MODE I
delta=504;             %Guard interval
Ts=2552;               %toatal length of a symbol
k=1536;                %number of carriers

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%  信号发生器，生成的数放在mass_prj里，注意，这也是以用来和解调结果比较的源信号 %
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mass_prj=binornd(1,0.5,[n_data,k*2]); %参数为0.5的二项分布伪随机数

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%                         QPSK mapping，结果放在QPSK_map里                      %
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%由于自然进化了行列操作，比原先的程序简单许多，运行效率也更高
QPSK_map=(1/(2^0.5))*((1-(mass_prj(:,1:k)*2))+i*(1-(mass_prj(:,k+1:2*k)*2)));

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%                  Frequency interleaving,结果放在Freq_inter里                  %
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%matrix_k是频率插值正变换矩阵，取自328目录下的interleaver.m
Freq_inter=QPSK_map*matrix_k;

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%                       Differentiation,结果放在Diff_mo里                       %              
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%注意，此段程序以前并未编写过
%用了累计积cumprod，使程序更简单
Diff_mo=[];
for i_nk=1:k
    Diff_mo=[Diff_mo,cumprod(Freq_inter(:,i_nk))];
end
 
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%                       OFDM Modulation，结果放在OFDM_mo里                      %
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%OFDM调制器输入端，1536个信号点，前768个和后768个互换位置
%再补上512个0，凑足2048个点，存为OFDM_in
OFDM_in=[Diff_mo(:,k/2+1:k),zeros(n_data,512),Diff_mo(:,1:k/2)];

%每行分别进行2048点的IFFT变换，结果仍是同维的复数矩阵
%当参数x是一个矩阵时，ifft(x)会对x的每一列分别进行ifft计算，而我需要的是每行分别
%进行ifft，因此采用了先转置，再转置回来的方法，注意 .'表示只转置而不求共轭
OFDM_out=(ifft(OFDM_in.')).';

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%              给OFDM_mo里面的数加上guard interval，成为OFDM_guard              %
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OFDM_guard=[OFDM_out(:,1545:2048),OFDM_out];

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%                            创造一帧数据，放在frame_1里                        %
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frame_1=[null,PRS];
for i_frame_1=1:n_data
frame_1=[frame_1,OFDM_guard(i_frame_1,:)];
end

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%                           原始数据和待发送数据帧的存储                        %
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save('imp data.mat','mass_prj','frame_1');