The long preamble should be the 320-sample one. right?
*Best Regards,Isen I-Chun Chao* On Sat, Nov 29, 2014 at 6:39 AM, Bastian Bloessl <bloe...@ccs-labs.org> wrote: > > > On 2014-11-29 12:34, Isen I-Chun Chao wrote: > >> Okay, I got it. >> >> One more quick question. >> I have been pretty confused about what the sync long and sync short are, >> respectively, responsible for? >> > > Sync short is for frame detection and searches for the cyclic pattern of > the short preamble (autocorrelation). Once a (potential) frame is detected, > sync long correlates sync_length samples with the long preamble and > searches for peaks to align OFDM symbols. > > > >> Thanks. >> >> /Best Regards, >> Isen I-Chun Chao/ >> >> On Sat, Nov 29, 2014 at 6:29 AM, Bastian Bloessl <bloe...@ccs-labs.org >> <mailto:bloe...@ccs-labs.org>> wrote: >> >> >> >> On 2014-11-29 12:28, Isen I-Chun Chao wrote: >> >> Hi Bastian, >> Thanks for your reply. >> The peaks you mentioned is like the correlation result? >> >> >> Yes, exactly >> >> >> /Best Regards, >> Isen I-Chun Chao/ >> >> On Sat, Nov 29, 2014 at 6:21 AM, Bastian Bloessl >> <bloe...@ccs-labs.org <mailto:bloe...@ccs-labs.org> >> <mailto:bloe...@ccs-labs.org <mailto:bloe...@ccs-labs.org>>> >> wrote: >> >> Hi Isen, >> >> >> On 2014-11-29 07:01, Isen I-Chun Chao wrote: >> >> Hi, >> I am using gr-ieee-802-11 and putting a custom block, >> which is >> responsible for adding a 90-sample preamble at the head >> of incoming >> sample stream, right after the output of WiFi PHY Hier, >> as attached >> figure, generator.png. So the sample stream is changed >> as attached >> figure, adding_preamble.png. >> >> However, in the case of use of transceiver.grc, I can >> still >> successfully >> decode received data, which is keep printing out "Hello >> World!". >> >> Does anyone know why adding extra samples at the head of >> transmission >> samples does not affect the receiving results? Does it >> because >> somewhere >> in Rx side detect the OFDM preamble so the payload can >> be normally >> processed without being affecting by the extra samples >> placed before >> OFDM preamble? >> >> >> >> The sync long block does matched filtering with the long >> preamble >> and searches for peaks in a configurable window (sync length >> parameter). Looks like even if you add 90 symbols the peak >> that the >> block is looking for is still in the window. >> >> Best, >> Bastian >> >> >> >> -- >> Dipl.-Inform. Bastian Bloessl >> Distributed Embedded Systems >> University of Paderborn, Germany >> http://www.ccs-labs.org/~__bloessl/ <http://www.ccs-labs.org/~ >> bloessl/> >> >> >> > -- > Dipl.-Inform. Bastian Bloessl > Distributed Embedded Systems > University of Paderborn, Germany > http://www.ccs-labs.org/~bloessl/ >
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