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- auto compensate cyclic prefix

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git-svn-id: http://moon:8086/svn/matlab/trunk@25 801c6759-fa7c-4059-a304-17956f83a07c
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jens
2015-04-05 14:07:25 +00:00
parent 81650fd21b
commit bddaaee2d5
2 changed files with 29 additions and 10 deletions
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ofdm/fdet.m
+4 -5
View File
@@ -1,8 +1,7 @@
function [omega, err, dmod, omega_coarse, omega_est] = fdet(x, N, Ng, omega_min, omega_step, omega_max)
function [omega, err, dmod, omega_coarse, omega_est] = fdet(x, N, Ng, off, omega_min, omega_step, omega_max)
%
% Example: fdet_eval(1200, pi/4, -10, [1100 1350 1])
K = fix(length(x-Ng)/(N+Ng));
K = fix((length(x)-Ng)/(N+Ng))-1;
% Initial guess
omega_coarse = fdet_coarse(x, N, omega_min, omega_step, omega_max);
@@ -10,12 +9,12 @@ omega_coarse = fdet_coarse(x, N, omega_min, omega_step, omega_max);
phi_est = 0;
omega_est = omega_coarse;
off = 0;
for k=1:K
omega(k) = omega_est;
xp = x((k-1)*(N+Ng)+off+1:k*(N+Ng)+off);
x_est = exp(-j*(2*pi*omega_est*(0:N-1)' + phi_est));
dmod(k) = sum(xp(Ng+1:N+Ng).*x_est);
iq = xp(Ng+1:N+Ng).*x_est;
dmod(k) = sum(iq);
phi = angle(dmod(k));
omega_f = phi/N/(2*pi);
err(k) = omega_f;
ofdm/fdet_wav.m
+25 -5
View File
@@ -28,21 +28,41 @@ else
x = xwav.*exp(-j*(2*pi*fc/fs*(0:len-1)'));
end
fprintf('Perform frequency correction\n');
x = x.*exp(j*(2*pi*foff/fs*(0:len-1)'));
[omega, err, dmod, omega_coarse, omega_est] = fdet(x, N, Ng, omega_min, omega_step, omega_max);
% Remove cyclic prefix
fprintf('Perform CP calculation\n');
x0 = x(1:2*(N+Ng));
x1 = x(N+Ng+1:3*(N+Ng));
c = xcorr(x0, x1);
[v, ii] = max(abs(c));
cp_off = mod(ii, Ng+N)
% Detect CFO
fprintf('Perform frequency detection\n');
[omega, err, dmod, omega_coarse, omega_est] = fdet(x, N, Ng, cp_off, omega_min, omega_step, omega_max);
f_coarse = omega_coarse*fs
f_est = omega_est*fs
close all;
subplot(4,1,1)
plot(abs(c)); grid;
figure;
subplot(5,1,1)
plot(1:lge(omega), real(dmod)/N, 1:lge(omega), imag(dmod)/N, 1:lge(omega), abs(dmod)/N); grid; legend('Re', 'Im', 'abs()');
subplot(4,1,2)
subplot(5,1,2)
plot(1:lge(omega), err*fs, '-'); grid; legend('error');
subplot(4,1,3)
subplot(5,1,3)
plot(1:lge(omega), omega*fs); grid; legend('f');
subplot(4,1,4)
subplot(5,1,4)
plot(1:lge(omega), angle(dmod), '-', 1:lge(omega), diff(angle([0 dmod])), 'r-'); grid; legend('phi', 'dphi');
subplot(5,1,5)
plot(1:lge(omega), abs(dmod)/N - real(dmod)/N, '-'); grid; legend('diff');