On 03/16/2018 09:33 AM, guillaume.toc...@orange.com wrote: > Hello all, > > I want to make a flow graph for transmitting and receiving OFDM > modulated data. To be precise, I want to do a LTE-M "like" > transmission/reception, so I am trying to transmit data with a BW of > 1.08 MHz OFDM. > To do so, I use the following configuration : samp_rate = 1.92 MHz, fft > length = 128, number of sub carriers = 72 , cp = 32 > > I modified the tx_ofdm.grc example file > (/gnuradio/gr-digital/examples/ofdm/tx_ofdm.grc) > To summary, I change the occupied carriers : range(-36, -21) + > range(-20, -7) + range(-6, 0) + range(1, 7) + range(8, 21) + range(22, > 37),) ; pilot carriers and symbols unchanged ; double the sync words to > be equal to fft length. > > The problem is at the output of the "Tag debug" I have just those > messages : > INFO: Parser returned #f > INFO: Detected an invalid packet at item 1496 > ...... > INFO: Parser returned #f > INFO: Detected an invalid packet at item 681901 > > And the spectrum isn't "stable" at 1.08 MHz BW.
Are you going across the air? The most common cause for this is too much gain, and resulting distortions caused by large PAPR. If you've increased the number of carriers, PAPR also goes up (a bit). -- M > > > What am I doing wrong ? How the sync words are determine ? Should I add > pilot/symbol carriers ? > > > Best Regards and thanks by advance, > > Guillaume Tochou > > > > > _________________________________________________________________________________________________________________________ > > Ce message et ses pieces jointes peuvent contenir des informations > confidentielles ou privilegiees et ne doivent donc > pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu > ce message par erreur, veuillez le signaler > a l'expediteur et le detruire ainsi que les pieces jointes. Les messages > electroniques etant susceptibles d'alteration, > Orange decline toute responsabilite si ce message a ete altere, deforme ou > falsifie. Merci. > > This message and its attachments may contain confidential or privileged > information that may be protected by law; > they should not be distributed, used or copied without authorisation. > If you have received this email in error, please notify the sender and delete > this message and its attachments. > As emails may be altered, Orange is not liable for messages that have been > modified, changed or falsified. > Thank you. > > > > _______________________________________________ > 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
