main.m

传统的卷积码和Turbo码直到今天仍有广泛的应用

clear;
FrameNum=10000;%码块数目
leng=128;%码块信息长的一半,即协议中的N
data=randint(1,FrameNum*leng*2,2);%产生随机数
L1=4;%用于估计编码器状态的迭代次数
niter=L1+8;%总的迭代次数
if leng==96
    index=1;
    CodeBlockSize=48*8;%编码后码块长度,单位是比特
    rate=0.5;%码率
elseif leng==128
    index=2;
    CodeBlockSize=48*8;
    rate=2/3;
elseif leng==144
    index=3;
    CodeBlockSize=48*8;
    rate=0.75;
elseif leng==192
    index=4;
    CodeBlockSize=96*8;
    rate=0.5;
elseif leng==288
    index=5;
    CodeBlockSize=96*8;
    rate=0.75;
elseif leng==384
    index=6;
    CodeBlockSize=144*8;
    rate=2/3;
elseif leng==432
    index=7;
    CodeBlockSize=144*8;
    rate=0.75;
end
EbN0=5;
x=zeros(1,CodeBlockSize*FrameNum);%x存放编码结果
ratio=zeros(length(EbN0),length(L1));%BER
FrameErrNum=zeros(length(EbN0),length(L1));%PER
%// encoding
for i=1:FrameNum
    x((i-1)*CodeBlockSize+1:i*CodeBlockSize)=CtcEncoder(data((i-1)*leng*2+1:i*leng*2),index);
end
%// modulation
[ModulateResult,nindex]=modulation(x,index);
snr=EbN0+1.25;%根据各个码的码率以及调制方式计算EbN0与snr之间的差值.1.25是第二种ctc的修正值
for i=1:length(EbN0)
    i
    %// adding noise
    NoiseSignal=awgn(ModulateResult,snr(i),'measured');
    %// demodulation
    DemoduResult=demodulation(NoiseSignal,nindex);
    %// multiplied by the reliability value of the channel
    en=10^(EbN0(i)/10);
    L_c=4*en*rate;%为了防止计算溢出,对于16-QAM调制,再乘一个因子(1/sqrt(10)),64-QAM乘以(1/sqrt(42))
    y=0.5*L_c*DemoduResult;
%CtcDecode存放译码结果
    CtcDecode=zeros(1,FrameNum*leng*2);
    for k=1:length(L1)
%迭代译码,统计BER和PER
        for j=1:FrameNum
            CtcDecode((j-1)*leng*2+1:j*leng*2)=CtcDecoder(y((j-1)*CodeBlockSize+1:j*CodeBlockSize),niter(k),index,L1(k));
            [num,frameratio]=biterr(CtcDecode((j-1)*leng*2+1:j*leng*2),data((j-1)*leng*2+1:j*leng*2));
            if num~=0
                FrameErrNum(i,k)=FrameErrNum(i,k)+1;
            end   
        end
        [num,ratio(i,k)]=biterr(data,CtcDecode);
        fid=fopen('FrameErrRatio.dat','a');
        fprintf(fid,'%d,%d:ber:%f,fer:%f\n',i,k,ratio(i,k),FrameErrNum(i,k)/FrameNum);
        fclose(fid);
    end
end