ofdm1.m

matlab仿真ofdm系统以及误码率分析

function Ber=NoEqualizer(SNR)

% Initialize the parameters
NumLoop = 1000;
NumSubc = 128;
NumCP = 8;
SyncDelay = 0;

% Generate the random binary stream for transmit test
BitsTx = floor(rand(1,NumLoop*NumSubc)*2);

% Modulate (generates QAM symbols)
% input: BitsTx(1,NumLoop*NumSubc); output: SymQAM(NumLoop,NumSubc/2)
SymQAMtmp = reshape(BitsTx,2,NumLoop*NumSubc/2).';
SymQAMtmptmp = bi2de(SymQAMtmp,2,'left-msb');
%00->-1-i,01->-1+i,10->1-i,11->1+i
QAMTable = [-1-i -1+i 1-i 1+i];
SymQAM = QAMTable(SymQAMtmptmp+1);

% IFFT
% input: SymQAM(NumLoop,NumSubc/2); output: SymIFFT(NumSubc,NumLoop)
SymIFFT = zeros(NumSubc,NumLoop);
SymIFFTtmp = reshape(SymQAM,NumSubc/2,NumLoop);
SymIFFTtmptmp = zeros(NumSubc,NumLoop);
SymIFFTtmptmp(1,:) = real(SymIFFTtmp(1,:));
SymIFFTtmptmp(NumSubc/2+1,:) = imag(SymIFFTtmp(1,:));
SymIFFTtmptmp(2:NumSubc/2,:) = SymIFFTtmp(2:NumSubc/2,:);
SymIFFTtmptmp((NumSubc/2+2):NumSubc,:) = flipdim(conj(SymIFFTtmp(2:NumSubc/2,:)),1);
SymIFFT = ifft(SymIFFTtmptmp,NumSubc,1);

% Add cyclic prefix
% input: SymIFFT(NumSubc,NumLoop); output: SymCP(NumSubc + NumCP,NumLoop)
NumAddPrefix = NumSubc + NumCP;
SymCP = zeros(NumAddPrefix,NumLoop);
RowPrefix = (NumSubc - NumCP + 1):NumSubc;
SymCP = [SymIFFT(RowPrefix,:);SymIFFT];

% Go through the channel
% input: SymCP(NumSubc + NumCP,NumLoop); output: SymCh(1,(NumSubc + NumCP)*NumLoop)
SymCh = zeros(1,(NumSubc + NumCP)*NumLoop);
SymChtmp = SymCP(:).';
Ch = [1 1/2 1/4];
SymChtmptmp = filter(Ch,1,SymChtmp);
% Add the AWGN
snr = SNR + 10*log10(log2(2));
SymCh = awgn(SymChtmptmp,snr,'measured');


% remove guard intervals
% input: SymCh(1,(NumSubc + NumCP)*NumLoop); output: SymDeCP(NumSubc,NumLoop)
SymDeCP = zeros(NumSubc,NumLoop);
SymDeCPtmp = reshape(SymCh,NumSubc + NumCP,NumLoop);
SymDeCP = SymDeCPtmp((NumCP+1+SyncDelay):NumAddPrefix+SyncDelay,:);

% FFT
% input: SymDeCP(NumSubc,NumLoop); output: SymFFT(NumSubc,NumLoop)
SymFFT = fft(SymDeCP,NumSubc,1);

% Make decision(Include DeQAM)
% SymFFT(NumSubc,NumLoop); output: SymDec(NumSubc,NumLoop)
SymDec = zeros(NumSubc,NumLoop);
SymEqtmp(1,:) = SymFFT(1,:)+i*SymFFT(NumSubc/2+1,:);
SymEqtmp(2:NumSubc/2,:) = SymFFT(2:NumSubc/2,:);
for m = 1:NumLoop
    for n = 1:NumSubc/2
        Real = real(SymEqtmp(n,m));
        Imag = imag(SymEqtmp(n,m));
        if( abs((Real -1)) < abs((Real +1  )) )
            SymDec(2*n-1,m) = 1;
        else
            SymDec(2*n-1,m) = 0;
        end
        if( abs((Imag -1)) < abs((Imag +1  )) )
            SymDec(2*n,m) = 1;
        else
            SymDec(2*n,m) = 0;
        end
    end
end

% Bit Error
BitsRx = zeros(1,NumSubc*NumLoop);
BitsRx = SymDec(:).';
[Num,Ber] = symerr(BitsTx,BitsRx)