[Discuss-gnuradio] Re: Improvement to OFDM receiver synchronization code (ofdm_sync_pn)

[Dominik Auras]

Hi Kylie,

This has also been proposed by Minn et. al in their paper "On timing 
offset estimation for OFDM systems". They showed that this method also 
improves the variance of the estimator.

The modification is quite simple:
R(d) = 0.5 * sum over full window |r(d+m)|^2.

I think, normally the correlation power should always be less or equal 
to the signal power. But if you have very small powers near zero that 
can't be precisely described with your current operands' bitwidth, the 
calculated power value may become smaller which yields a ratio greater 
than 1.0.

However, we have never experienced such problems with our OFDM system 
except for offline debugging scenarios. Over the air, the presence of 
noise will probably avoid this problem.

Dominik