- improved TX and RX

git-svn-id: http://moon:8086/svn/matlab/trunk@5 801c6759-fa7c-4059-a304-17956f83a07c

ofdm/ofdm_rx.m

@@ -1,126 +1,23 @@
-% function ofdm_sync(x, nsym, ngrd)
+function ofdm_rx(x)
-% 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);
+CP_SIZE = 254;
-% Detection
+FFT_SIZE = 1024;
-display('Sync detection');
+fa = 48000;
-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
+k_fft = 2*sqrt(FFT_SIZE);
-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)
+Ns = (CP_SIZE + FFT_SIZE);
-plot(1:length(sl_err), sl_err); title('error'); legend('error'); grid;
+Nf = length(x)/Ns;
-subplot(2,1,2)
+for k=1:Nf
-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;
+    Xs = fft(x((k-1)*Ns+CP_SIZE+1:(k-1)*Ns+CP_SIZE+FFT_SIZE), FFT_SIZE)/k_fft;
-
+    mag = abs(Xs(1:FFT_SIZE/8));
-figure
+    phase = angle(Xs(1:FFT_SIZE/8));
-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');
+    subplot(2, 1, 1)
-
+    plot(fa*(0:lge(mag)-1)/FFT_SIZE, mag, '-*'); grid;
-% custom function
+    subplot(2, 1, 2)
-% Correlation
+    plot(fa*(0:lge(phase)-1)/FFT_SIZE, phase, '-*'); axis([0, fa*(lge(phase)-1)/FFT_SIZE, -pi, +pi]);grid;
-function [ccm, imax, jmax, xo] = xcc(x, Ns, Ng, i_low, i_high, j_low, j_high, xi)
+    pause (0.001);
-
+end
-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;
-

ofdm/ofdm_tx.m

@@ -2,12 +2,14 @@
 function [yv xv] = ofdm_tx(N_frames)
 
 close all;
-M_QAM = 4;
-RC_ROLLOFF = 0.1;
 
+WITH_RCWIN = 1;
 WITH_DATA = 1;
 WITH_FREQ_REF = 1;
-WITH_TIME_REF = 0;
+WITH_TIME_REF = 1;
+
+M_QAM = 16;
+RCWIN_ROLLOFF = 0.1;
 
 % Params
 fa = 48000;
@@ -80,11 +82,11 @@ Ts = Tu+Tg
 Ng = round(Tg*fa)
 Nu = round(Tu*fa)
 Ns = round(Ts*fa)
-N_fft = Nu
+N_fft = Nu;
 SubCarrierspacing_HZ = fa/N_fft
 
 % TX window
-[txwin Nt] = txwin_eval(Nu, Ng, RC_ROLLOFF);
+[rcwin Nt] = txwin_eval(Nu, Ng, RCWIN_ROLLOFF);
 
 % Source
 qlut = qamtable(M_QAM);
@@ -102,7 +104,8 @@ for k=1:N_frames
 		% Data
 		if WITH_DATA == 1
 	    	data_i = c2i(N_fft, ofdm_spec_occ.kmin:1:ofdm_spec_occ.kmax);
-	    	X(data_i) = 0.20*qlut(round(M_QAM*rand(1, length(data_i))+0.5));
+	    	sym = round(M_QAM*rand(1, length(data_i))+0.5);
+	    	X(data_i) = 0.20*qlut(sym);
     	end;
 %    	X(c2i(N_fft,65)) = 0.20*qlut(round(M_qam*rand(1, 1)+0.5));
 
@@ -117,13 +120,15 @@ for k=1:N_frames
 		    X(c2i(N_fft, ref_c)) = 0.20*ref_a.*(exp(2*pi*i*ref_p/1024));
 	    end;
 		    
-%	    X(1) = 0.2;
-
 	    % Modulate
 	    xu = k_fft*ifft(X, N_fft)';
-	    xs = [xu(Nu-Ng+1:Nu) xu xu(1:Nt)] .* txwin;
+        if WITH_RCWIN == 1
-	    xs(1:Nt) = xs(1:Nt) + xt(1:Nt);
+    	    xs = [xu(Nu-Ng+1:Nu) xu xu(1:Nt)] .* rcwin;
-	    xt = xs(Ng+Nu+1:Ng+Nu+Nt);
+            xs(1:Nt) = xs(1:Nt) + xt(1:Nt);
+            xt = xs(Ng+Nu+1:Ng+Nu+Nt);
+        else
+    	    xs = [xu(Nu-Ng+1:Nu) xu];
+        end;
 	    xv = [xv xs(1:Ng+Nu)];
         Xs = fft(xs(Ng+1:Ng+Nu), N_fft)/k_fft;
         plot(fa*(0:N_fft/8-1)/N_fft, abs(Xs(1:N_fft/8)), '-*'); grid;
@@ -132,16 +137,12 @@ for k=1:N_frames
 end;
 
 % Modulate on carrier
-yc = 0.5*exp(i*2*pi.*(0:length(xv)-1)*fc/fa) .* filter(hlp,1,xv);
+yc = 0.5*exp(i*2*pi.*(0:length(xv)-1)*fc/fa) .* xv; %filter(hlp,1,xv);
 yv = real(yc) + imag(yc);
 
-xv = xv';
+xv = conj(xv');
 yv = yv';
 
-% Output
-figure;
-freqz(hlp);
-
 wavwrite(0.9*yv,fa,16,'yv.wav')
 wavwrite(0.9*[real(xv) imag(xv)],fa,16,'xv.wav')