function [n, Nd, valid, Zf] = timing_coarse(x, N, Ng, L, Zi)

if (~isfield(Zi, 'valid'))
    Zi = struct('valid', 1, 'n', 0, 'xp', [], 'p', 1.0);
end
Zf = Zi;
Zf.xp = [Zf.xp' x']';

n = Zf.n;
Nd = N;
valid = 0;

if (length(Zf.xp) < 3*N+Ng)
    return
end

RCWIN_ROLLOFF = 0.125;
[rcwin Nt wng] = txwin_eval(N, Ng, RCWIN_ROLLOFF);

% RC Windowing at TX
% Calculate merged CP'
% -----------------------------------------------
% | CP |    :    :    | CP |    :    :    | CP |     
% ----------------------------------------------------> nt
%        x0             x1             x2
%
% CP' = x0 * (1-w) + x2 * w

k = 1;
for nt=N+Ng:N+Ng+N-2,
    for d=1:3,
        Nd = N-2+d;
        x0 = Zf.xp(nt-Nd+1:nt-Nd+L);
        x1 = Zf.xp(nt+1:nt+L);
        x2 = Zf.xp(nt+Nd+1:nt+Nd+L);
        xcps = x0 .* (1-wng') + x2 .* (wng');
        n = 0.5*(abs(x1).^2 + abs(xcps).^2);
        c(k, d) = sum(abs(x1 .* conj(xcps)) - 1.0*n);
    end
    k = k + 1;
end
[v1, n1] = max(c);
[v2, n2] = max(v1);
Nd = N-2+n2;
n = mod(n1(n2)-1, N+Ng);

Zf.xp = Zf.xp(N+Ng+1:length(Zf.xp));
Zf.n = n;
valid = 1;
if (0)
    plot(d); grid;
    pause(0.01);
end