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! -- Alex, *Dreams can come true – just believe.*
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