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文档采用MATLAB发布，仿真没有跑完。

CCSDS标准的LDPC编译码仿真

本脚本完成了CCSDS标准(o1)版本中适用于深空通信任务的LDPC编译码过程的仿真，同时给出了在信息位长度为1024，码率为1/2时的误码率仿真结果

  撰写人：***

  最后修改日期：2015-03-07

  软件版本：MATLAB(R) 2014a

和之前版本（LDPC_Simulation.m）对比，本程序添加功能包括

完成了校验矩阵构造（ccsdscheckmatrix.m）
通过校验矩阵构造（准循环）生成矩阵（ccsdsgeneratematrix.m）
按照ccsds所述，对编码后数据进行截取，完成符合ccsds文档的ldpc编译码仿真

程序修改包括

之前文件夹内的译码函数均不能对全0项进行正确的处理
问题将得到合适的修正,同时优化了输出显示

初始设置

清空工作区，数据，关闭所有窗口

clc;clear all;close all;

仿真参数设置

EbN0_dB = 1;                             % EbN0_dB 误码率范围，向量;

FRAMES_NUM = 1;                          % FRAMES_NUM 最大仿真帧数目;

MAX_ITER_NUM = 30;                       % MAX_ITER_NUM 算法最大迭代次数;

MAX_ERROR_FRAME = 200;                   % MAX_ERROR_FRAME 仿真最大错误帧数目;

bitError = zeros(1,length(EbN0_dB));     % bitError 误码数目统计，向量;

BER = bitError;                          % BER 误码率，向量;

frameError = bitError;                   % frameError 误帧数目;

iterNumTotal = zeros(1,length(EbN0_dB)); % iterNumTotal 总迭代次数统计，向量;

INFO_LENGTH = 1024;                      % INFO_LENGTH 信息位长度

RATE = 1/2;                              % RATE 码率

SIZE_M = 512;                            % M矩阵大小（参考CCSDS文档）

打开（新建）文件，保存运行数据

FILE_NAME = ['LDPC_CCSDS_' datestr(now,'yyyymmdd') '.txt'];

fid = fopen(FILE_NAME,'at+');

fprintf(fid,'日期 %s\n',datestr(now,'yyyymmdd'));

fprintf(fid,'%s\n','CCSDS的LDPC标准中section3中的码，06年版');

fprintf(fid,'信息位长度 = %d, ',INFO_LENGTH);

fprintf(fid,'码率 = %d, ',RATE);

H为校验矩阵；G为生成矩阵。通过调用函数实现

H = ccsdscheckmatrix(SIZE_M,RATE);

G = ccsdsgeneratematrix(H,SIZE_M,RATE);

译码准备

[r_mark,c_mark] = find(H~=0);

HColNum = sum(H);

HRowNum = cell(1,size(H,1));

for rowH = 1:size(H,1)

    HRowNum{rowH} = find(r_mark==rowH);

end

误码率仿真

在不同EbN0下，对误码率进行仿真

for nEbN0 = 1:length(EbN0_dB)

多帧取统计平均

    for nF=1:FRAMES_NUM

编码过程

        message = randi([0 1],1,INFO_LENGTH);

        encodeData = mod(message*G,2);

调制

        transmitSignal = 2*encodeData - 1;   %映射 0—-1； 1—+1

        transmitSignalPower = sqrt(var(transmitSignal));

        transmitSignal = transmitSignal/transmitSignalPower;%归一化

AWGN 信道，SNR和EbN0换算关系

        SNR_dB = EbN0_dB((nEbN0)) + 10*log10(2)+10*log10(RATE);

        SNR = 10^(SNR_dB/10);

        noise = randn(1,length(transmitSignal));

        noise = noise/sqrt(SNR);     %SNR换算，加噪声

        receiveSignal = transmitSignal + noise;

根据CCSDS文档实际上有M个符号没有被传送，此处取其值为0，做仿真上的等效

        receiveSignal(end-1*SIZE_M+1:end-0*SIZE_M) = 0;

译码，可调用不同的函数

        [iterNum,recoverData] = ...

            ldpcdecoderllr(H,HRowNum,HColNum,receiveSignal,SNR,MAX_ITER_NUM);

            %ldpcdecoderbp1(H,HRowNum,HColNum,receiveSignal,SNR,MAX_ITER_NUM);

            %ldpcdecoderminsum(H,HRowNum,HColNum,receiveSignal,SNR,MAX_ITER_NUM);

        % 文件输出

        if(nEbN0==1 && nF==1)

            fprintf(fid,'译码程序为ldpcdecoderllr\n');

            fprintf(fid,'最大迭代次数 = %d, ',MAX_ITER_NUM);

            fprintf(fid,'\n-------------------------------\n');

            fprintf(fid,'EbN0\t 总帧数\t 误帧数\t 误比特数\t 平均迭代次数\t 误比特率\t 误帧率\n');

            % MATLAB的readtable笨笨的不认识中文，所以打一行给他看

            fprintf(fid,'EbN0\t T_Frame\t E_Frames\t E_Bits\t A_IterNums\t BER\t FER\n');

        end

误比特数，误帧数，迭代次数统计

        bitError(nEbN0) = bitError(nEbN0) + ...

            sum(abs(message - recoverData(1:length(message))));

        frameError(nEbN0) = frameError(nEbN0) + ...

            (sum(abs(encodeData - recoverData(1:length(encodeData))))~=0);

        iterNumTotal(nEbN0) = iterNumTotal(nEbN0) + iterNum;

停止条件和文件输出

         if ( frameError(nEbN0)>=MAX_ERROR_FRAME || nF==FRAMES_NUM)

            BER(nEbN0) = bitError(nEbN0)/nF/length(message);

            fprintf(fid,'%3.2g\t %5d\t %4d\t ',EbN0_dB(nEbN0),nF,frameError(nEbN0));

            fprintf(fid,'%8d\t %8.6g\t ',bitError(nEbN0),iterNumTotal(nEbN0)/nF);

            fprintf(fid,'%e\t %e\n',BER(nEbN0),frameError(nEbN0)/nF);

             break;

         end

         if (mod(nf,100)==0)

            BER(nEbN0) = bitError(nEbN0)/nF/320;

            fprintf(fid,'\n-------------------------------\n');

            fprintf('Eb/No = %e \n',EbN0_dB(nEbN0));

            fprintf('总帧数 = %d, ',nF);

            fprintf('误帧数 = %d, ',frameError(nEbN0));

            fprintf('误比特数 = %d, ',bitError(nEbN0));

            fprintf('最大迭代次数 = %d, ',MAX_ITER_NUM);

            fprintf('平均迭代次数 = %e, ',iterNumTotal(nEbN0)/nF);

            fprintf('误码率 = %g, ',BER(nEbN0));

            fprintf('误帧率 = %g \n',frameError(nEbN0)/nF);

         end

end

end

仿真结果

通过编码后实际误码率对比图，不要看下面的图，图没有仿真出来的，太慢了

fclose(fid);

readtable(FILE_NAME,'HeaderLines',6,'Delimiter','\t')

semilogy(EbN0_dB,BER,'r');

xlabel('Eb/N0(dB)'); ylabel('BER');

grid on;

ans = 

    EbN0    T_Frame    E_Frames    E_Bits    A_IterNums    BER    FER

    ____    _______    ________    ______    __________    ___    ___

    1       1          0           0         27            0      0

Published with MATLAB® R2014a

=MAX_ERROR_FRAME || nF==FRAMES_NUM)
BER(nEbN0) = bitError(nEbN0)/nF/length(message);
fprintf(fid,'%3.2g\t %5d\t %4d\t ',EbN0_dB(nEbN0),nF,frameError(nEbN0));
fprintf(fid,'%8d\t %8.6g\t ',bitError(nEbN0),iterNumTotal(nEbN0)/nF);
fprintf(fid,'%e\t %e\n',BER(nEbN0),frameError(nEbN0)/nF);
break;
end
if (mod(nf,100)==0)
BER(nEbN0) = bitError(nEbN0)/nF/320;
fprintf(fid,'\nREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASHREPLACE_WITH_DASH_DASH-\n');
fprintf('Eb/No = %e \n',EbN0_dB(nEbN0));
fprintf('总帧数 = %d, ',nF);
fprintf('误帧数 = %d, ',frameError(nEbN0));
fprintf('误比特数 = %d, ',bitError(nEbN0));
fprintf('最大迭代次数 = %d, ',MAX_ITER_NUM);
fprintf('平均迭代次数 = %e, ',iterNumTotal(nEbN0)/nF);
fprintf('误码率 = %g, ',BER(nEbN0));
fprintf('误帧率 = %g \n',frameError(nEbN0)/nF);
end
end
end

%% 仿真结果
%%
% 通过编码后实际误码率对比图，不要看下面的图，图没有仿真出来的，太慢了
fclose(fid);
readtable(FILE_NAME,'HeaderLines',6,'Delimiter','\t')
semilogy(EbN0_dB,BER,'r');
xlabel('Eb/N0(dB)'); ylabel('BER');
grid on;
##### SOURCE END #####
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