会计学线性分组码编码(biānmǎ)原理（7，4）线性分组码上例（7,4）码的监督(jiāndū)矩阵为：MPSK调制(tiáozhì)原理QPSK正交调制器原理图及信号矢量图（A方式(fāngshì)编码）4PSKπ/4系统（B方式编码）相干(xiānggān)解调经过低通滤波器LPF后输出(shūchū)分别为:将输入的数字(shùzì)序列分成组，每组独立进行编码，称为分组码。程序(chéngxù)流程图clearall;clc;m=2;n=7;x=4;M=2^m;EsN0dB=0:1:10;%信噪比的分贝值EsN0=10.^(EsN0dB/10);%分贝值转换Es=1;N0=10.^(-EsN0dB/10);sigma=sqrt(N0/2);error=zeros(1,length(EsN0dB));s_data=zeros(1,length(EsN0dB));fork=1:length(EsN0dB)error(k)=0;s_data(k)=0;MSG=(sign(randn(96000,x))+1)/2;%产生(chǎnshēng)均匀分布的伪随机序列作为信源ifn==7&x==4gxx=[1,0,0,0;0,1,0,0;0,0,1,0;0,0,0,1;1,1,1,0;1,1,0,1;1,0,1,1];gx=gxx';%gx为线性码的生成矩阵elseifn==7&x==3gxx=[1,0,0;0,1,0;0,0,1;1,0,1;1,1,1;1,1,0;0,1,1];gx=gxx';elsen==5&x==2gxx=[1,0;0,1;1,0;0,1;1,1];gx=gxx';endd=encode(MSG,n,x,'linear',gx);ds=reshape(d',m,(96000*n)/m);dataa=bin2dec(num2str(ds'));%num2str是数值(shùzí)转换成字符串s=sqrt(Es)*exp(j*2*pi/M*(dataa'));%加入信道噪声（复噪声）r=s+sigma(k)*(randn(1,length(dataa))+sqrt(-1)*randn(1,length(dataa)));fory=1:M%计算距离rd(y,:)=abs(r-sqrt(Es)*exp(j*2*pi/M*(y-1)));endfory=1:length(s)%判决距离最近的点dd(y)=find(rd(:,y)==min(rd(:,y)));endkk=dec2bin(dd-1);kb=double(kk)-48;zccmsg=reshape(kb',n,96000);ccmsg=zccmsg';d3=decode(ccmsg,n,x,'linear',gx);d33=reshape(d3,1,96000*x);MSGG=reshape(MSG,1,96000*x);error(k)=sum(d33-MSGG~=0);s_data(k)=s_data(k)+672000;endPe=error./s_data;semilogy(EsN0dB,Pe,'b');holdon;clearall;clc;M=4;Es=1;EsN0dB=0:1:10;EsN0=10.^(EsN0dB/10);%信噪比的分贝值N0=10.^(-EsN0dB/10);%分贝值转换sigma=sqrt(N0/2);error=zeros(1,length(EsN0dB));s_data=zeros(1,length(EsN0dB));fork=1:length(EsN0dB)error(k)=0;s_data(k)=0;d=ceil(rand(1,96000)*M);s=sqrt(Es)*exp(j*2*pi/M*(d-1));%调制成QPSK信号（复基带形式）r=s+sigma(k)*(randn(1,length(d))+j*randn(1,length(d)));form=1:Mrd(m,:)=abs(r-sqrt(Es)*exp(j*2*pi/M*(m-1)));endform=1:length(s)%判断(pànduàn)距离最近的点dd(m)=find(rd(:,m)==min(rd(:,m)));ifdd(m)~=d(m)error(k)=error(k)+1;endends_data(k)=s_data(k)+96000;endPe=error./s_data;semilogy(EsN0dB,Pe,'r');holdon;xlabel('Es/N0(dB)');ylabel(