ldpc_demo.m

关于LDPC编译码的程序

clear all;
clc;

%%%%%%%%%%%% for total variable%%%%%%%%%%%%%%%%%
total_count = 0;
Count = 10;
loop = 0;
%%%%%%%%%%%%define dimension of the parity check matrix%%%%%%%%
rows=128;
cols=256;
h=gen_ldpc(rows,cols);%generates a 100 x 200 H matrix( the IG parity check matrix)
% load h.mat;
% h = check1;

[newh,rearranged_cols]=rearrange_cols(h);
% newh holds the rearranged version of H and rearranged_cols holds the
% rearrangement order of columns

%%%%%%%%%%%%Get A and B matrices %%%%%%%%%%%%%%%%
for i=1:rows
    for j=1:rows
        A(i,j)=newh(i,j);
    end
end
for i=1:rows
    for j=rows+1:cols
        B(i,j-rows)=newh(i,j);
    end
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
while loop < Count
    %%%%%%%%%%%%%%message bits%%%%%%%%%%%%%%%%%%%%%

    %generate message bits randomly
    %for j=1:10%simulate 1000 flame
    for i=1:cols-rows
        s(i)=round(rand);
    end
    %%%%%%%%%%%%%%%% for the test of writing C code.%%%%%%%%%%%%%%%%%%%
    %s(1) = 1; s(2) = 0; s(3) = 1;
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    if loop == 0
        s=s';
    end
    % make it a row vector
    %%%%%%% or load s from file %%%%type "help load" at matlab prompt for details

    %%%%%%%%%%%%%% get check bits %%%%%%%%%%%%%%%%
    d=mul_GF2(inv_GF2(A),B);
    c=mul_GF2(d,s);
    %%%%%%%%%%%%%%%%%form u'%%%%%%%%%%%%%  the info bits is at back of check bits.
    u1=c;
    for i=rows+1:cols
        u1(i)=s(i-rows);
    end
    %%%%%%%%%%%%%%% reorder u?to get the CW u %%%%%%%%%%%%%%%%%%%
    u=reorder_bits(u1,rearranged_cols);
    
    %%%%%%%%%%%%%%% Modulation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % assume the codeword c, the parity check matrix H and No are already loaded into the MATLAB memory
    tx_waveform=bpsk(u,1);  %amp= 1 , this is the modulator with bpsk.
    
    
    %%%%%%%%%%%%%% for the channel. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    No=7; % for setting the Eb/No(SNR).
%     rx_waveform=awgn(tx_waveform,No);    % add noise.
    
    
    %%%%%%%%%%%%% modified by lilei %%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    sigma = add_noise(tx_waveform, No, 1, 1);
    rx_waveform = tx_waveform + sigma * randn(1,length(tx_waveform));
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    
    
    scale(1:length(u))=1;  %No fading.
    %%%%%%%%%%%%% LDPC decoder %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    vhat=decode_ldpc(rx_waveform,No,1,h,scale); %since amp=1;
    % assume we have the rearranged_cols array output by the rearrange_cols( ) function already loaded into MATLAB memory
    uhat = extract_mesg(vhat,rearranged_cols);
    message = uhat';

    %%%%%%%%%%%%%%% u is the codeword to be transmitted %%%%%%%%%%%%%%%%%%%
    nerr=0;
    errmax=mod((s+uhat'),2);
    for i=1:(cols - rows)
        if(errmax(i)==1)
            nerr=nerr+1;
        end
    end
    %end
    total_count = total_count + nerr;
    loop = loop + 1;
    loop
end
% ber=nerr/(rows*10);
ber = total_count / ((cols - rows) * Count);
ber