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Problems with Zadoff-Chu auto correlation

Started by stan.maciej December 16, 2009
Hello,

I am currently studying the CAZAC sequences and I took a look at the
Zadoff-Chu sequence commonly used in LTE. When I perform a time-domain
autocorrelation on a 63 sample long Zadoff-Chu sequence with root 29, I get
a plot that does not correspond to the autocorrelation plots available in
the litterature (LTE The UMTS Long Term Evolution, from Theory to practice
by S. Sesia and all. p149). 
In my plot, the peakto second peak ratio approx 3, comparably to a ratio
of 10 in the litterature (my secondary peak are much higher).
This is the matlab code I am using to generate the autocorrelation:

cazac = zeros(63,1);
u = 29;
for n=0:62
    cazac(n+1) = exp(-1i*pi*u*(n+1)*n/63);
end
cazac(32) = 0;
corrB = xcorr(fft(cazac), fft(cazac));
 
corrB = corrB/max(corrB);
figure(1);
time = [-62:62];
plot(time, abs(corrB));
axis([-64 64 0 1]);

I would be grateful if somebody could take a quick look at this code and
point out what I am doing wrong. I really appreciate your help (I already
so much time on this).

Thanks,
Stan