jens
d5d5df21f9
git-svn-id: http://moon:8086/svn/matlab/trunk@2 801c6759-fa7c-4059-a304-17956f83a07c
107 lines
2.2 KiB
Matlab
107 lines
2.2 KiB
Matlab
% function ofdm_tx(N_data)
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function yv = ofdm_tx(N_data)
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j = sqrt(-1);
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WORK_BANDPASS = 1;
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do_evaluate = 0;
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% Params
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fa = 48000;
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fc = fa/4;
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F1 = 750;
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F2 = 2250;
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F3 = 3000;
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N_Carrier = 226;
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M_qam = 64;
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N_lp = 301;
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TSym = 21.3330E-3
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TGrd = 5.333E-3
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TFrm = TSym+TGrd
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NGrd = round(TGrd*fa)
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NSym = round(TSym*fa)
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NFrm = round(TFrm*fa)
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N_fft = NSym
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bin_c = fix(N_fft*fc/fa)+1;
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bin_f1 = fix(N_fft*(fc+F1)/fa)+1;
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bin_f2 = fix(N_fft*(fc+F2)/fa)+1;
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bin_f3 = fix(N_fft*(fc+F3)/fa)+1;
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% Source
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qlut = qamtable(M_qam);
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s = round(M_qam*rand(N_data,1)+0.5);
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% Band pass for transmission
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f_lp = N_Carrier*fa/N_fft
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hbp = cos(2*pi*(0:N_lp-1)*fc/fa).*sinc((-(N_lp-1)/2:(N_lp-1)/2)*f_lp/fa);
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hbp = hbp/sum(hbp.^2).*Hanning(N_lp)';
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hlp = sinc((-(N_lp-1)/2:(N_lp-1)/2)*f_lp/fa);
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hlp = hlp/sum(hlp.^2).*Hanning(N_lp)';
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t = 1;
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if (WORK_BANDPASS == 1)
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bin_range = N_fft/4-N_Carrier/2:N_fft/4+N_Carrier/2;
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else
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bin_range = 1:N_Carrier;
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end;
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N_bins = length(bin_range);
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for k=1:N_data/N_bins,
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% DC
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X = zeros(N_fft,1);
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X(1) = 0;
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for m=1:N_bins,
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% Data
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X(bin_range(m)) = qlut(s(t));
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t = t + 1;
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end;
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% Additional carrier
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if (WORK_BANDPASS == 1)
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X(bin_c) = 1.0;
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X(bin_f1) = 1.0 + j*1.0;
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X(bin_f2) = 1.0 - j*1.0;
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X(bin_f3) = -1.0 + j*1.0;
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end;
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% Make conj. symmetric in F => real in T
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X(N_fft:-1:N_fft/2+1) = conj(X(2:N_fft/2+1));
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% Modulate
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x = ifft(X);
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xgrd = x(NSym-NGrd+1:NSym);
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xt = [xgrd' x']';
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xv((k-1)*(NFrm)+1:k*(NFrm)) = xt;
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if (do_evaluate == 1)
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xf = fft(xt(NGrd+1:NSym+NGrd), N_fft);
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plot(xf, '+'); grid;
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pause;
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end;
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end;
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k_fft = 0.3333*sqrt(N_fft);
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% Pulse shape
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if (WORK_BANDPASS == 1)
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yv = real(filter(hbp,1,k_fft*xv));
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% yv = k_fft*xv;
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else
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yc = cos(2*pi*(0:length(xv)-1)*fc/fa);
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yF1 = 1.0/N_fft*cos(2*pi*(0:length(xv)-1)*F1/fa);
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yF2 = 1.0/N_fft*cos(2*pi*(0:length(xv)-1)*F2/fa);
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yF3 = 1.0/N_fft*cos(2*pi*(0:length(xv)-1)*F3/fa);
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yv = yc.*(0.025 + filter(hlp,1,k_fft*xv) + yF1 + yF2 + yF3);
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end;
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% Output
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close all;
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figure;
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freqz(hlp);
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wavwrite(yv,fa,16,'yv.wav') |