- added CFO estimation

git-svn-id: http://moon:8086/svn/matlab/trunk@30 801c6759-fa7c-4059-a304-17956f83a07c

ofdm/cfo_coarse_fract.m

@@ -0,0 +1,23 @@
+function [domega_f, Zf] = cfo_coarse_fract(x, N, Ng, L, Nd, Zi)
+
+if (~isfield(Zi, 'valid'))
+    Zi = struct('valid', 1, 'n', 0, 'xp', [], 'p', 1.0);
+end
+Zf = Zi;
+domega_f = 0;
+
+Zf.xp = [Zf.xp' x']';
+
+if (length(Zf.xp) < 2*(N+Ng))
+    n = Zf.n;
+    return
+end
+
+x1 = Zf.xp(1:L);
+x2 = Zf.xp(Nd+1:Nd+L);
+c = sum(x1 .* conj(x2));
+
+domega_f = 1/(2*pi*N) * angle(c);
+
+Zf.xp = x;
+

ofdm/cfo_coarse_int.m

@@ -1,30 +1,102 @@
-function [omega_coarse, Xm] = fdet_coarse(x, N, Ng, omega_min, omega_step, omega_max)
+function [d_bin, valid, Zf] = cfo_coarse_int(x, N, carrier_pilot, bins_search, Zi)
 
-Xm = zeros(N,1);
+if (~isfield(Zi, 'valid'))
-
+    Zi = struct('valid', 1, 'Xm', zeros(N, 1), 'Xv', zeros(N, 1), 'Zk', [], 'd_bin', []);
-if 0
-    
-K = fix((length(x))/(N+Ng));
-
-for k=1:K,
-    xp = x((k-1)*(N+Ng)+1:k*(N+Ng));
-    Xm = 0.5*Xm + fft(xp(Ng+1:N+Ng), N);
 end
 
-Nmax = ceil(omega_max*N)+1
+alpha = 0.01;
-[v, ii] = max(abs(Xm(1:Nmax)))
+rho = 0.999;
+k_boost = 4;
+noise_eps = 1e-1;
 
-omega_coarse = (ii-1)/N;
+if 1
+    bin_pilots = c2i(N, carrier_pilot)-1;
+    bin_min = max(0, min(bin_pilots)-bins_search);
+    bin_max = min(N-1, max(bin_pilots)+bins_search);
     
+    Xk = zeros(N, 1);
+    valid = 0;
+    d_bin = Zi.d_bin;
+    Zk = fft(x, N);
+    if ~isempty(Zi.Zk)
+        Xk = Zk .* conj(Zi.Zk);
+        Zi.Xm = (1-alpha)*Zi.Xm + alpha*Xk;
+        Zi.Xv = Zi.Xv*rho;
+        Zi.Xv = max(Zi.Xm, Zi.Xv);
+        Xt = abs(Zi.Xv(bin_min+1:bin_max+1));
+
+        xnoise = noiseFloor(Xt, 4)+noise_eps;
+        bins = bin_min+find_bins(Xt, xnoise, k_boost, bins_search);
+        
+        if (~isempty(bins))
+            k = 1;
+            for b=1:length(bins)
+                bin_c = bins(b);
+                for n=1:length(bin_pilots)
+                    bin_p = bin_pilots(n);
+                    if (abs(bin_c - bin_p) < bins_search)
+                        d_bin = [d_bin (bin_c - bin_p)];
+                    end
+                end
+            end
+            h = zeros(length(bin_pilots), 1);
+            if length(d_bin) == length(bin_pilots)
+                valid = 1;
+                for k=1:length(d_bin)
+                    for b=1:length(d_bin)
+                        if d_bin(b) == d_bin(k)
+                            h(k) = h(k) + 1;
+                        end
+                    end
+                end
+            end
+        end
+        
+        if 1
+            plot(bin_min+(0:length(Xt)-1), abs(Xt), '-*', bin_min+(0:length(Xt)-1), xnoise, 'g-'); grid;
+            a = axis;
+            hold on;
+            if ~isempty(bins)
+                for b=1:length(bins)
+                    x = [bins(b) bins(b)];
+                    y = [a(3) a(4)];
+                    plot(x,y, 'r-');
+                end
+            end
+            hold off;
+            pause (0.01); 
+        end
+    end
+    Zi.Zk = Zk;
+
+end
+Zf = Zi;
+    
+function bins = find_bins(x, xnoise, kboost, bins_search)
+
+bins = [];
+for n=1:length(x)
+    if (x(n) > kboost*xnoise(n))
+        smin = max(1, n-bins_search);
+        smax = min(length(x), n+bins_search);
+        [v, nn] = max(x(smin:smax));
+        winner = nn + smin-2;
+        if isempty(find(bins == winner))
+            bins = [bins winner];  
+        end
+        n = min(length(x), n + bins_search);
+    end
+end
+bins = bins';
+
+function y = noiseFloor(x, kn)
+
+y(1) = x(1);
+for n=2:length(x)
+    if (x(n) < kn*y(n-1))
+        y(n) = 0.5*y(n-1) + 0.5*x(n);
     else
-    
+        y(n) = y(n-1);
-omega_range = (omega_min:omega_step:omega_max);
-
-for k=1:lge(omega_range)
-    x_est = exp(-j*(2*pi*omega_range(k)*(0:N-1)' + 0));
-    dmod(k) = sum(x(1:N).*x_est);
-end;
-[v maxk] = max(abs(dmod));
-omega_coarse = omega_range(maxk);
-
     end
+end
+