Mateusz, the sync words are both for the Schmidl & Cox synchronization. Also, they're defined in the frequency domain, so you won't see the 'two identical parts here'. Rather, you skip every 2nd carrier.
Cheers, Martin On 03/17/2016 04:47 AM, Mateusz wrote: > Hey, I do my Bachelor Thesis on OFDM using GnuRadio. > > I am using the joint system created from tx_ofdm and rx_ofdm examples. > In simulation I try to use a bigger fft. So far I have managed to send > and receive for fft_len=128 and fft_len=256, BPSK modulation. I ask to > help me understand the creation of sync_words for bigger fft. > > I see the influence of the training sequences which I use on the quality > of transmission. Of course I have read that the synchronization is based > on "PN Sequence Correlation" and "Maximal Likelihood" papers. I suppose > that sync_word1 and sync_word2 are based on those algorithms > respectively. However I don't see "two identical parts of PN sequence" > like it was described in the Schmidl&Cox paper. > > I tried to use the sequences containing 0's where needed, and random > -1's and 1's elsewhere, but then the timing synchronization error > (missing trigger signal in sync_sc) occurs more often, than when I use > the replicas of original sync_words from the OFDM example. > > I attach the file with the training sequences which I have used. > > Regards, > Mateusz Loch > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
