On Sat, Mar 24, 2012 at 8:52 PM, Alex Zhang <address@hidden
> Hi Gurus,
> I just want to make sure how the current gnuradio ofdm exampel is
> doing synchronization.
> According to T. M. Schmidl and D. C. Cox, "Robust Frequency and
> Timing Synchonization for OFDM," IEEE Trans. Communications, vol. 45, no.
> 12, 1997.
> When, estimating the carrier frequency offset at the receiver, if the phase
> difference between the two halves of the 1st training symbol is guaranteed
> to be less than PI, then the frequency offset estimate can derived by
> Phi/(Pi*T). In this situation, the even PN sequencies of the second training
> symbol would not be needed. Otherwise, the actual frequency offset would be
> Phi/(Pi*T) + 2*z/T
> and the z can be estimated by some optimization algorithm, using both of
> the training symbols. Also, the paper mentioned that the odd frequencies of
> the second training symbol can be used to measure the sub-channels.
> However, I find that only one training symbol is generated to act as
> preamble at the ofdm transmitter. And on the receiver, it seems that only
> one preamble is used to estimate the timing peak and the frequency offset.
> Is the current implementation assuming that the frequency is less than PI?
> Or anything I missed?
> Looking forward to your input!
> Dreams can come true – just believe.