clear;
clc;
SNR=10; % 信噪比
%fl=128; % 设置FFT长度
Ns=6; %设置一个祯结构中OFDM信号的个数
para=128;%设置并行传输的子载波个数
sr=250000; %符号速率
br=sr.*2;% 每个子载波的比特率
gl=32; %保护时隙的长度
fl=para;
Signal=rand(1,para*Ns*2)>0.5;%产生0,1 随即序列,符号数为para*Ns*2
for i=1:para
for j=1:Ns*2
SigPara(i,j)=Signal(i*j);%串并变换
end
end
%QPSK调制,将数据分为两个通道
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); %频域数据变时域
y=ifft(x);
ich2=real(y);
qch2=imag(y);
%插入保护间隔
ich3=[ich2(fl-gl+1:fl,:);ich2];
qch3=[qch2(fl-gl+1:fl,:);qch2];
%并串变换
ich4=reshape(ich3,1,(fl+gl)*Ns);
qch4=reshape(qch3,1,(fl+gl)*Ns);
%形成复数发射数据
TrData=ich4+qch4.*sqrt(-1);
%接收机
%加入高斯白噪声
BerSnrTable = zeros(20,3);
for snr=0:19; % = SNR + 10*log10(log2(2));
BerSnrTable(snr+1,1) = snr;
ReData = awgn(TrData,snr,'measured');
end;
%ReData=awgn(TrData,SNR,'measured');
ReData = channel(ReData,SNR);
%接收端
%移去保护间隔
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);
%符号抽样判决
ReSig=ReSig>0.5;
figure(1);
subplot(2,1,1),stem(ReData(1:10)),grid minor;
title('经过信道的信号');
xlabel('x'),ylabel('y');
subplot(2,1,2),stem(TrData(1:10)),grid;
title('经过QAM的未经过信道的信号')
figure(2);
subplot(2,1,1),stem(ReSig(1:100)),grid minor;
title('接收到的信号');
xlabel('x'),ylabel('y');
subplot(2,1,2),stem(Signal(1:100)),grid;
title('原始信号')
%figure(3);
%subplot(1,1,1),plot(ReData(1:100),TrData(1:100)),grid minor;
%title('resignal');
%xlabel('x'),ylabel('y');
%figure(4);
%subplot(1,1,1),plot(ReSig(1:100),Signal(1:100)),grid minor;
%title('resignal');
%xlabel('x'),ylabel('y');
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