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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