Dear Bastian, I missed one another thing.
`if(((d_count + o) % 64) == 0)` statement in https://github.com/bastibl/gr-ieee802-11/blob/master/lib/ofdm_sync_long.cc#L141 Is this because of a length of an OFDM signal being a multiple of 64, which is the number of subcarriers? (Except cyclic prefix) Regards, Jeon. 2015-05-09 22:32 GMT+09:00 Jeon <sjeon87+gnura...@gmail.com>: > Dear Marcus and Bastian, > > Thank you for your detailed answers. > > Also, thank you for useful usage of gist. :) > > Regards, > Jeon. > > > 2015-05-09 21:42 GMT+09:00 Bastian Bloessl <bloe...@ccs-labs.org>: > >> Hi, >> >> >> > On 09 May 2015, at 13:23, Marcus Müller <marcus.muel...@ettus.com> >> wrote: >> > >> > So, looking at this, it's taking the delayed input samples and copies >> them (offset-corrected) to the output, considering parts of the samples, >> > x = ignore, o = copy, starting at the frame start: >> > >> > oooooooo|xx¦oooooo|xx¦oooooo|... >> > 128 |16¦128-16|16¦128-16|… >> > >> >> Exactly, it’s to remove the cyclic prefix (remove the first 16 samples of >> every 80 samples). Unfortunately, the first 128 samples (the long training >> sequence) don’t fit into the same scheme. Therefore the special case here. >> >> Best, >> Bastian >> >> >> > >> > I'm not too familiar with 802.11p frames, but that looks like Basti's >> leaving out some pilots in between the data, probably only copying the >> preamble and data payload. But I could be wrong. >> > >> > Greetings, >> > Marcus >> > >> > [1] >> https://github.com/bastibl/gr-ieee802-11/blob/master/lib/ofdm_sync_long.cc#L128 >> > >> > On 05/09/2015 12:06 PM, Jeon wrote: >> >> I am looking gr-ieee802-11 module. >> >> >> >> a part of the source code is pasted here ( >> https://gist.github.com/gsongsong/3df4553fe96e2d62b83e) >> >> >> >> I have a question on the following statement: >> >> >> >> `if(rel >= 0 && (rel < 128 || ((rel - 128) % 80) > 15))` in `case >> COPY` >> >> `if(((d_count + o) % 64) == 0)` in `case RESET` >> >> >> >> I am wonder what do these numbers(128, 80, 15, 64) and modulo >> operation have logical meaning in IEEE 802.11p PHY frame? >> >> >> >> I've read 802.11 OFDM specification, thus I have knowledge about it, >> >> but I have no idea what are roles of these things in implementation. >> >> >> >> Regards, >> >> Jeon. >> >> >> >> >> >> _______________________________________________ >> >> 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 >> >> -- >> Dipl.-Inform. Bastian Bloessl >> Distributed Embedded Systems Group >> University of Paderborn, Germany >> http://www.ccs-labs.org/~bloessl/ >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > >
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