[MATLAB project combat] LDPC-BP channel coding

除了Turbo码之外, Gallger于 1960Low-density checksums proposed in (Low Density ParityCheck,LDPC)The code can also approach the Shannon world.This section describes binaryLDPCcode simulation

different symbol lengthsWER变化情况：
从图中可以看出,Code length is an influenceLDPCan important factor in code performance,LDPCThe decoding performance of the code is significantly improved with the increase of the code length.码长为1024The code is longer than the code length512The encoding has a performance of approx0.5dB的提高

主程序：

clc;clear all;
SNRdB=0:0.25:3; %SNR in dB
k=512/4;
n=1024/4; % 码长
niter= 60;% Maximum iteration at this time
nb_err = zeros(1,length(SNRdB));
nb_code = zeros(1,length(SNRdB));
nb_err_max= 100 ;
nb_code_max= 1e4;
H= gen_h(n,6,3);% 产生H
[Hs,H]=gen_Hs(H); % into a system code
Q= Hs(:,1:k)'; % generate a matrixQ

for s= 1:length(SNRdB)
    sigma = 10^(-SNRdB(s)/20);% Its square is the noise power
    while nb_err(s)<nb_err_max && nb_code(s)<nb_code_max
        nb_code(s) = nb_code(s)+1;
        b = rand(1,k)<0.5;
        c=[b,rem(b*Q,2)];% System code encoding
        x=(-1).^c;% BPSK modulation
        noise = sigma * randn(1,length(x));
        y = x+noise;
        lam_ch= 2*y/sigma^2;%soft demodulation
        hat_c= msa(lam_ch,niter,H);
        err = any(hat_c~=c); %cis the transmit codeword,hat_cis a hard judgment
        if err
            nb_err(s)= nb_err(s)+err;
            disp([nb_err;nb_code])
        end
    end
end

WER= nb_err./nb_code;
EbN0dB= SNRdB+10*log10(n/k/2);%化成Eb/N0,参考式(1)
figure(1)
semilogy(EbN0dB, WER,'o-','LineWidth',2)
xlabel('Eb/N0')
ylabel('WER')
grid on;
hold on

SNRdB=0:0.25:3; %SNR in dB
k=512/2;
n=1024/2; % 码长
niter= 60;% Maximum iteration at this time
nb_err = zeros(1,length(SNRdB));
nb_code = zeros(1,length(SNRdB));
nb_err_max= 100 ;
nb_code_max= 1e4;
H= gen_h(n,6,3);% 产生H
[Hs,H]=gen_Hs(H); % into a system code
Q= Hs(:,1:k)'; % generate a matrixQ

for s= 1:length(SNRdB)
    sigma = 10^(-SNRdB(s)/20);% Its square is the noise power
    while nb_err(s)<nb_err_max && nb_code(s)<nb_code_max
        nb_code(s) = nb_code(s)+1;
        b = rand(1,k)<0.5;
        c=[b,rem(b*Q,2)];% System code encoding
        x=(-1).^c;% BPSK modulation
        noise = sigma * randn(1,length(x));
        y = x+noise;
        lam_ch= 2*y/sigma^2;%soft demodulation
        hat_c= msa(lam_ch,niter,H);
        err = any(hat_c~=c); %cis the transmit codeword,hat_cis a hard judgment
        if err
            nb_err(s)= nb_err(s)+err;
            disp([nb_err;nb_code])
        end
    end
end

WER= nb_err./nb_code;
EbN0dB= SNRdB+10*log10(n/k/2);%化成Eb/N0,参考式(1)
figure(1)
semilogy(EbN0dB, WER,'s-','LineWidth',2)
xlabel('Eb/N0')
ylabel('WER')
grid on;
hold on

SNRdB=0:0.25:3; %SNR in dB
k=512;
n=1024; % 码长
niter= 60;%Maximum iteration at this time
nb_err = zeros(1,length(SNRdB));
nb_code = zeros(1,length(SNRdB));
nb_err_max= 100 ;
nb_code_max= 1e4;
H= gen_h(n,6,3);%产生H
[Hs,H]=gen_Hs(H); %into a system code
Q= Hs(:,1:k)'; %generate a matrixQ

for s= 1:length(SNRdB)
    sigma = 10^(-SNRdB(s)/20);%Its square is the noise power
    while nb_err(s)<nb_err_max && nb_code(s)<nb_code_max
        nb_code(s) = nb_code(s)+1;
        b = rand(1,k)<0.5;
        c=[b,rem(b*Q,2)];%System code encoding
        x=(-1).^c;%BPSK modulation
        noise = sigma * randn(1,length(x));
        y = x+noise;
        lam_ch= 2*y/sigma^2;%soft demodulation
        hat_c= msa(lam_ch,niter,H);
        err = any(hat_c~=c); %cis the transmit codeword,hat_cis a hard judgment
        if err
            nb_err(s)= nb_err(s)+err;
            disp([nb_err;nb_code])
        end
    end
end

WER= nb_err./nb_code;
EbN0dB= SNRdB+10*log10(n/k/2);%化成Eb/N0,参考式(1)
figure(1)
semilogy(EbN0dB, WER,'^-','LineWidth',2)
xlabel('Eb/N0')
ylabel('WER')
grid on;

legend('n=256','n=512','n=1024')

代码链接（包括word文档）：https://download.csdn.net/download/qq_45047246/86268695