- improved TX

- added TX windowing - added RX git-svn-id: http://moon:8086/svn/matlab/trunk@3 801c6759-fa7c-4059-a304-17956f83a07c
2014-07-26 18:34:33 +00:00
parent d5d5df21f9
commit 2a04c6b44c
3 changed files with 371 additions and 73 deletions
@@ -0,0 +1,126 @@
+% function ofdm_sync(x, nsym, ngrd)
+% Example: ofdm_sync(x, 1152, 128)
+function ofdm_rx(x, offset, nsym_soll, ngrd)
+
+% Init
+fa = 48000;
+fc = fa/4;
+F1 = 750;
+F2 = 2250;
+F3 = 3000;
+close all;
+do_evaluate = 1;
+alpha = 0.05;
+
+x = real(x);
+% Detection
+display('Sync detection');
+nsym_ist = nsym_soll;
+xi = zeros(ngrd, 1);
+range_max = 24;
+range_min = 4;
+range_forget = 0.5;
+range = range_max;
+err = 0;
+k = 0;
+kk = 1;
+remain = length(x);
+progress_ival = 1;
+progress_last = -1;
+nfft = nsym_soll-ngrd
+
+bin_c = fix(nfft*fc/fa)+1
+bin_f1 = fix(nfft*(fc+F1)/fa)+1
+bin_f2 = fix(nfft*(fc+F2)/fa)+1
+bin_f3 = fix(nfft*(fc+F3)/fa)+1
+k_fft = 3/sqrt(nfft);
+
+phi_c_last = 0;
+phi_f1_last = 0;
+phi_f2_last = 0;
+phi_f3_last = 0;
+
+while remain > 2*nsym_ist,
+    xsym = x(offset+k*nsym_ist+1:offset+k*nsym_ist+nsym_ist+range);
+    [xcor, imax, jmax, xi] = xcc(xsym, nsym_ist, ngrd, -range, range, -range, range, xi);
+    remain = remain - (length(offset+k*nsym_ist+1:offset+k*nsym_ist+nsym_ist+range));
+    err = -imax + jmax;
+    offset = offset + imax;
+    nsym_ist = max(round(nsym_ist + err), ngrd)
+    sl_offset(kk) = offset;
+    sl_err(kk) = err;
+    sl_nsym_ist(kk) = nsym_ist;
+    range = min(max(fix(range + abs(err) - range_forget), range_min), range_max);
+    progress = round(100*(length(x)-remain)/length(x));
+    if (progress ~= progress_last)
+       progress_last = progress_last + progress_ival;
+       progress = progress
+    end;
+    if (do_evaluate == 1)
+      X0 = k_fft*fft(xsym(1:nsym_ist-ngrd), nfft);
+      phi_c(kk) = (1-alpha)*phi_c_last + alpha*angle(X0(bin_c));
+      phi_f1(kk) = (1-alpha)*phi_f1_last + alpha*angle(X0(bin_f1));
+      phi_f2(kk) = (1-alpha)*phi_f2_last + alpha*angle(X0(bin_f2));
+      phi_f3(kk) = (1-alpha)*phi_f3_last + alpha*angle(X0(bin_f3));
+      phi_c_last = phi_c(kk);
+      phi_f1_last = phi_f1(kk);
+      phi_f2_last = phi_f2(kk);
+      phi_f3_last = phi_f3(kk);
+      %pause;
+    end;  
+    k = k + 1;
+    kk = kk + 1;
+end;
+
+% Result
+display('Results:');
+
+offset_stddev = sqrt(var(sl_offset))
+err_mean = mean(sl_err)
+nsym_ist_mean = mean(nsym_ist)
+
+% Diagrams
+figure;
+plot(1:length(sl_offset), sl_offset); title('offset'); legend('offset'); grid;
+
+figure;
+subplot(2,1,1)
+plot(1:length(sl_err), sl_err); title('error'); legend('error'); grid;
+subplot(2,1,2)
+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;
+
+figure
+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');
+
+% custom function
+% Correlation
+function [ccm, imax, jmax, xo] = xcc(x, Ns, Ng, i_low, i_high, j_low, j_high, xi)
+
+Nu = Ns - Ng;
+off = length(xi);
+
+xo = x(length(x)-off+1:length(x));
+xs = [xi' x']';
+
+ccm = 0;
+imax = 0;
+jmax = 0;
+for i_off=i_low:i_high,
+    ii = off+i_off+1:off+Ng+i_off;
+    xm_i = mean(xs(ii));
+    xi = xs(ii)-xm_i;
+    var_i = var(xi);
+    for j_off=j_low:j_high,
+        jj = off+Nu+j_off+1:off+Nu+Ng+j_off;
+        xm_j = mean(xs(jj));
+        xj = xs(jj) - xm_j;
+        var_j = var(xj);
+        cc = sum(xi.*xj)./sqrt(var_i*var_j);
+        if (cc > ccm)
+            imax = i_off;
+            jmax = j_off;
+            ccm = cc;
+        end;    
+    end;
+end;
+