awg.m

模拟高斯信道

clear
clc
%=====================================================
% common settings
%=====================================================
ifftsize=256;                                  % equals to number of samples 
in a useful symbol.
numcarr=256;                                   % Number of transmission 
carriers
cp=64;                                         % Guard Interval(length of 
cyclic extension)=25% of ifftsize
guardtype=2;                                   % 1=zeroed signal; 2=cyclic 
extension; 3=half zero,half cyclic
frameguard=ifftsize+cp;                        % Guard Time between 
successive frames (one symbol period)
wordsize=2;
SNRindex=1;
numsymb=100;

%===============信源==================================
  N = 512*numsymb;   % bits
  source = randint(1,N);
  source = reshape(source,numsymb,512);

%=====================================================
  for SNR=0:2:20
    SNR_dB(SNRindex)=SNR;

    numofbiterror_idea=0;         %误比特率初值设为0；

    for kk=1:numsymb
    t1 = source(kk,:);
    t1 = mapping_ofdm_qpsk(t1);
    st1 = ifft(t1);
    st1 = [st1((length(st1)-cp+1):end) st1];

    rt1= st1;
    rt1= awgn(rt1,10^(SNR/10),'measured',1234,'linear');
    rt1= rt1(cp+1:cp+1+255);
    rt1=fft(rt1);       %变换到频域

    p1_idea=rt1;
    deofdm1_idea = demapping_ofdm_qpsk(p1_idea);

    for jj=1:512           %求误比特率
        if (deofdm1_idea(jj) ~= source(kk,jj))
            numofbiterror_idea = numofbiterror_idea+1;
        end
    end
    end
   BER1_idea(SNRindex)=numofbiterror_idea/N;

   SNRindex=SNRindex+1;

  end

   semilogy(SNR_dB,BER1_idea,'b-*');
   xlabel('SNR')
   ylabel('BER')
   legend('ideal awgn')
   grid on
   hold off;