clear all;
close all;
 
SNR=10;  % 信噪比
fl=128;  % 設(shè)置FFT長(zhǎng)度
Ns=6;   %設(shè)置一個(gè)禎結(jié)構(gòu)中OFDM信號(hào)的個(gè)數(shù)
para=128;%設(shè)置并行傳輸?shù)淖虞d波個(gè)數(shù)
sr=250000; %符號(hào)速率
br=sr.*2;% 每個(gè)子載波的比特率
gl=32 %保護(hù)時(shí)隙的長(zhǎng)度

Sn=rand(1,para*Ns*2)>0.5;%產(chǎn)生0，1 隨即序列，符號(hào)數(shù)為para*Ns*2
for i=1:para
    for j=1:Ns*2
        SigPara(i,j)=Sn(i*j);%串并變換
    end
end
%QPSK調(diào)制，將數(shù)據(jù)分為兩個(gè)通道
for j=1:Ns
    ich(:,j)=SigPara(:,2*j-1);
    qch(:,j)=SigPara(:,2*j);
end
kmod=1./sqrt(2);
ich1=ich.*kmod;
qch1=qch.*kmod;
x=ich1+qch1.*sqrt(-1);  %ifft 頻域數(shù)據(jù)變時(shí)域
y=ifft(x);
ich2=real(y);
qch2=imag(y);
%插入保護(hù)間隔
ich3=[ich2(fl-gl+1:fl,:);ich2];
qch3=[qch2(fl-gl+1:fl,:);qch2];
%并串變換
ich4=reshape(ich3,1,(fl+gl)*Ns);
qch4=reshape(qch3,1,(fl+gl)*Ns);
%形成復(fù)數(shù)發(fā)射數(shù)據(jù)
TrData=ich4+qch4.*sqrt(-1);
%接收機(jī)
%加入高斯白噪聲
ReData=awgn(TrData,SNR,'measured');
%接收端
%移去保護(hù)間隔
idata=real(ReData);
qdata=imag(ReData);
idata1=reshape(idata,fl+gl,Ns);
qdata1=reshape(qdata,fl+gl,Ns);
idata2=idata1(gl+1:gl+fl,:);   
qdata2=qdata1(gl+1:gl+fl,:);       
%FFT
Rex=idata2+qdata2*sqrt(-1);
ry=fft(Rex);
ReIChan=real(ry);
ReQChan=imag(ry);
ReIchan=ReIChan/kmod;
ReQchan=ReQChan/kmod;
%QPSK逆映射
for j=1:Ns
    RePara(:,2*j-1)=ReIChan(:,j);
     RePara(:,2*j)=ReQChan(:,j);
end
ReSig=reshape(RePara,1,para*Ns*2);
%符號(hào)抽樣判決
ReSig=ReSig>0.5;
figure(1);
subplot(2,1,1),stem(Sn(1:20)),grid;
title('輸入信號(hào)圖形')
subplot(2,1,2),stem(ReSig(1:20)),grid minor;
title('恢復(fù)的信號(hào)圖形');
xlabel('x'),ylabel('y');
figure(2);
plot(abs(ReData));
title('加入高斯白噪聲時(shí)的圖形');