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;