jens
2a04c6b44c
- added TX windowing - added RX git-svn-id: http://moon:8086/svn/matlab/trunk@3 801c6759-fa7c-4059-a304-17956f83a07c
127 lines
3.4 KiB
Matlab
127 lines
3.4 KiB
Matlab
% function ofdm_sync(x, nsym, ngrd)
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% Example: ofdm_sync(x, 1152, 128)
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function ofdm_rx(x, offset, nsym_soll, ngrd)
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% Init
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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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close all;
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do_evaluate = 1;
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alpha = 0.05;
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x = real(x);
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% Detection
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display('Sync detection');
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nsym_ist = nsym_soll;
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xi = zeros(ngrd, 1);
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range_max = 24;
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range_min = 4;
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range_forget = 0.5;
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range = range_max;
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err = 0;
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k = 0;
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kk = 1;
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remain = length(x);
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progress_ival = 1;
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progress_last = -1;
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nfft = nsym_soll-ngrd
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bin_c = fix(nfft*fc/fa)+1
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bin_f1 = fix(nfft*(fc+F1)/fa)+1
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bin_f2 = fix(nfft*(fc+F2)/fa)+1
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bin_f3 = fix(nfft*(fc+F3)/fa)+1
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k_fft = 3/sqrt(nfft);
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phi_c_last = 0;
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phi_f1_last = 0;
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phi_f2_last = 0;
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phi_f3_last = 0;
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while remain > 2*nsym_ist,
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xsym = x(offset+k*nsym_ist+1:offset+k*nsym_ist+nsym_ist+range);
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[xcor, imax, jmax, xi] = xcc(xsym, nsym_ist, ngrd, -range, range, -range, range, xi);
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remain = remain - (length(offset+k*nsym_ist+1:offset+k*nsym_ist+nsym_ist+range));
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err = -imax + jmax;
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offset = offset + imax;
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nsym_ist = max(round(nsym_ist + err), ngrd)
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sl_offset(kk) = offset;
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sl_err(kk) = err;
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sl_nsym_ist(kk) = nsym_ist;
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range = min(max(fix(range + abs(err) - range_forget), range_min), range_max);
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progress = round(100*(length(x)-remain)/length(x));
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if (progress ~= progress_last)
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progress_last = progress_last + progress_ival;
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progress = progress
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end;
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if (do_evaluate == 1)
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X0 = k_fft*fft(xsym(1:nsym_ist-ngrd), nfft);
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phi_c(kk) = (1-alpha)*phi_c_last + alpha*angle(X0(bin_c));
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phi_f1(kk) = (1-alpha)*phi_f1_last + alpha*angle(X0(bin_f1));
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phi_f2(kk) = (1-alpha)*phi_f2_last + alpha*angle(X0(bin_f2));
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phi_f3(kk) = (1-alpha)*phi_f3_last + alpha*angle(X0(bin_f3));
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phi_c_last = phi_c(kk);
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phi_f1_last = phi_f1(kk);
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phi_f2_last = phi_f2(kk);
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phi_f3_last = phi_f3(kk);
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%pause;
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end;
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k = k + 1;
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kk = kk + 1;
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end;
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% Result
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display('Results:');
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offset_stddev = sqrt(var(sl_offset))
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err_mean = mean(sl_err)
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nsym_ist_mean = mean(nsym_ist)
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% Diagrams
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figure;
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plot(1:length(sl_offset), sl_offset); title('offset'); legend('offset'); grid;
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figure;
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subplot(2,1,1)
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plot(1:length(sl_err), sl_err); title('error'); legend('error'); grid;
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subplot(2,1,2)
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plot(1:length(sl_nsym_ist), sl_nsym_ist, 1:length(sl_nsym_ist), nsym_soll*ones(size(sl_nsym_ist))); title('Tracking'); legend('nsym_{ist}', 'nsym_{soll}'); grid;
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figure
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plot(1:length(phi_c), phi_c, 1:length(phi_f1), phi_f1, 1:length(phi_f2), phi_f2, 1:length(phi_f3), phi_f3); grid; legend('phi_{c}', 'phi_{f1}', 'phi_{f2}', 'phi_{f3}'); title('Phase');
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% custom function
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% Correlation
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function [ccm, imax, jmax, xo] = xcc(x, Ns, Ng, i_low, i_high, j_low, j_high, xi)
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Nu = Ns - Ng;
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off = length(xi);
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xo = x(length(x)-off+1:length(x));
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xs = [xi' x']';
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ccm = 0;
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imax = 0;
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jmax = 0;
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for i_off=i_low:i_high,
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ii = off+i_off+1:off+Ng+i_off;
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xm_i = mean(xs(ii));
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xi = xs(ii)-xm_i;
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var_i = var(xi);
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for j_off=j_low:j_high,
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jj = off+Nu+j_off+1:off+Nu+Ng+j_off;
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xm_j = mean(xs(jj));
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xj = xs(jj) - xm_j;
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var_j = var(xj);
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cc = sum(xi.*xj)./sqrt(var_i*var_j);
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if (cc > ccm)
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imax = i_off;
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jmax = j_off;
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ccm = cc;
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end;
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end;
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end;
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