awgntest.m

加性高斯白噪声信道下

% This is a program to test OFDM on AWGN
clc
N=256;
NL=10;
KL=4*N*NL;
% ep=0.2;
% epgj=0.198;
 SNR_dB = 0:2:20;

% theo_pb=BPSK_err(SNR_dB);

   for l=1:length(SNR_dB),
    num_of_err=0;
    num_of_err0=0;
      num_of_err2=0;
    snr=10^(SNR_dB(l)/10);
        
     sgma=sqrt(4/(N*snr)); % noise standard deviation
        
       for i=1:NL    
       input=rand(1,4*N);    %输入的二进制数据序列

        for i=1:4*N
              if input(i)>0.5
                 input(i)=1;
               else 
                  input(i)=0;
              end
        end
%     end
% end 

for n=1:N
for ic=1:4 
    qam_input(ic)=input((n-1)*4+ic);  %qam的输入 
end
   qam_out(n)=qam16(qam_input);     %qam的输出
end
inputqam=qam_out;
for n=1:N
noise(n)=normrnd(0,sgma)+normrnd(0,sgma)*sqrt(-1);    %输入的随机噪声
end
transa=ifft(inputqam,N);
receb=transa+noise;
zk=fft(receb,N);
ofdmout2=zk

ij=1;
for i=0:N-1  
output2=de_qam16(ofdmout2(i+1));
outqam2(ij:ij+3)=output2;
ij=ij+4;
end

inx=input;
outy2=outqam2;

       
     for iy=1:4*N
         if inx(iy) ~= outy2(iy)
            num_of_err2=num_of_err2+1;
        end
     end
     
  end

 
    ber2(l)=num_of_err2/KL;
end
% figure(1)
 semilogy(SNR_dB,ber2,'k-o')
 axis([0,20,1e-6,1])
grid on
end