Re: [Discuss-gnuradio] Tag preemption USRP sink

ha! "O"s in your output mean that the USRP source had to drop samples, because your computer was slower at processing them than the USRP was at producing them, filling up the buffers, until they were full to the brim and nothing more would fit.
Of course, reducing the CPU load in this scenario, e.g. by usage of more CPU-efficient filters, will reduce the number of dropped samples, and hence, will reduce the FER!

On 17.12.2015 15:14, Saulo Queiroz wrote:

Yes.    I forgot to mention that I used QPSK 1/2 in the experiments.      On 17 December 2015 at 14:01, Marcus Müller-3 [via GnuRadio] <  ml-node+s4n57342h55@n7.nabble.com> wrote:    

Hm, do you see "O"s on the output?    On 17.12.2015 15:39, Saulo Queiroz wrote:    

well, I tried again and, again, FFT behaved better.  In case someone else wanna give a try, flowgraphs are attached.      On 17 December 2015 at 12:34, Marcus Müller <[hidden email]  

<http:///user/SendEmail.jtp?type=node&node=57342&i=0>>  

wrote:    

Hm, that is an interesting result.    The point is that  the polyphase "magic" that allows decimation before  pushing samples through a FIR is mathematically 100% equivalent to  

doing  

the decimation after the FIR.  Nearly the same goes for (non-decimating) FIR vs FFT filter: whereas  

the  

FIR really just "pushes" the samples through convolution with the taps  

in  

time domain, the FFT filter just multiplies the frequency domain  representation of blocks of samples with the frequency domain  

equivalent to  

the taps, before transforming the result back to time domain. Should be  absolutely identical.    Now, the question is: if the filters were functionally actually 100%  identical, what would explain the different FER? Or are we comparing  

the  

Flowgraph pre-rectructuring with the flowgraph-post-restructuring,  

where  

other things have changed, too?    Best regards,  Marcus  On 17.12.2015 12:55, Saulo Queiroz wrote:    Hi    In my "through-the-air" tests with a couple of B210s the FFT filters  presented much lower  FER in comparison to the FIR filters at the Rx side. According to [1],  

the  

"FFT filters"  downsamples after filtering while FIR downsamples before filtering.    cheers    [1]  

http://www.trondeau.com/blog/2014/2/27/to-use-or-not-to-use-fft-filters.html  

  On 15 December 2015 at 19:06, Saulo Queiroz <[hidden email]  

<http:///user/SendEmail.jtp?type=node&node=57342&i=1>> <[hidden email]  <http:///user/SendEmail.jtp?type=node&node=57342&i=2>> wrote:  

    Many thanks Bastian!    I checked the loopback version and it seems to work very well.    I'll check over-the-air and report here!    On 15 December 2015 at 19:04, Bastian Bloessl <[hidden email]  

<http:///user/SendEmail.jtp?type=node&node=57342&i=3>> <[hidden email]  <http:///user/SendEmail.jtp?type=node&node=57342&i=4>>  

wrote:      Hi,    I replaced the Frequency Xlating FFT filters with FIR filters, used the  Low-Pass Filter Taps block to generate taps (since I can't get my head  around this notation), and removed the filter from the first  

conversion.  

  Now, it seems to work. At least it receives frames. If you still have  problems I can send you the flow graph.    Best,  Bastian        On 15 Dec 2015, at 10:05, Saulo Queiroz <[hidden email]  

<http:///user/SendEmail.jtp?type=node&node=57342&i=5>> <[hidden email]  <http:///user/SendEmail.jtp?type=node&node=57342&i=6>> wrote:  

  Each stream has been shiffted with the xlating block.  The intention is to "split" a 20 MHz wide analog channel into two of 10    MHz.    Each 10 MHz channel transmit its own ofdm frame.  I attached the flowgraph for more details.    thanks in advance.    On 15 December 2015 at 17:42, Martin Braun-2 [via GnuRadio] <[hidden    email]> wrote:    tP indicates you're using corrupt tagged streams, maybe your add block  is overlaying them? I'm also not entirely sure what you mean by  'simultaneous parallel transmissions'. Are they on different  frequencies? Are you mixing them together in baseband?    Cheers,  Martin      On 15.12.2015 04:10, Saulo Queiroz wrote:      Hi all,    I'm trying to Tx a same tagged stream simultaneously through two    analog    orthogonal channels.    The flow path of each stream copy is: resampling, adjust tag lenght    and    xlating FFT filter (with shifting). After this I take the output of    each    filter and put into and add block then to the USRP sink. I also do the  reverse process at the Rx side.  With some packets are successfuly receive but with so many losses. At  the Tx side I get many "tP". Any tip on how to set simultaneous    parallel    transmissions without this?    I'm using gr-ieee80211 (thanks Bastian and team :) that has worked  nicely with the single channel scenario.    thanks in advance    BR    --  Saulo Jorge bq  - "Beware of bugs in the above code; I have only proved it correct,    not    tried it."  Donald Knuth.      _______________________________________________  Discuss-gnuradio mailing list  [hidden email]https://lists.gnu.org/mailman/listinfo/discuss-gnuradio    _______________________________________________  Discuss-gnuradio mailing list  [hidden email]https://lists.gnu.org/mailman/listinfo/discuss-gnuradio      If you reply to this email, your message will be added to the    discussion below:      

http://gnuradio.4.n7.nabble.com/Tag-preemption-USRP-sink-tp57286p57297.html  

  To start a new topic under GnuRadio, email [hidden email]  To unsubscribe from GnuRadio, click here.  NAML        --  Saulo Jorge bq  - "Beware of bugs in the above code; I have only proved it correct, not    tried it."    Donald Knuth.     wifi_tx_rx_loopback.grc (134K) Download Attachment    View this message in context: Re: Tag preemption USRP sink  Sent from the GnuRadio mailing list archive at Nabble.com.  _______________________________________________  Discuss-gnuradio mailing [hidden email]  

<http:///user/SendEmail.jtp?type=node&node=57342&i=7>://  lists.gnu.org/mailman/listinfo/discuss-gnuradio  

  --  Dipl.-Inform. Bastian Bloessl  Distributed Embedded Systems Group  University of Paderborn, Germanyhttp://www.ccs-labs.org/~bloessl/     --  Saulo Jorge bq  - "Beware of bugs in the above code; I have only proved it correct, not  tried it."  Donald Knuth.          _______________________________________________  Discuss-gnuradio mailing [hidden email]  

<http:///user/SendEmail.jtp?type=node&node=57342&i=8>://  lists.gnu.org/mailman/listinfo/discuss-gnuradio  

      _______________________________________________  Discuss-gnuradio mailing list  [hidden email] <http:///user/SendEmail.jtp?type=node&node=57342&i=9>  https://lists.gnu.org/mailman/listinfo/discuss-gnuradio      

    _______________________________________________  Discuss-gnuradio mailing list  [hidden email] <http:///user/SendEmail.jtp?type=node&node=57342&i=10>  https://lists.gnu.org/mailman/listinfo/discuss-gnuradio      ------------------------------  If you reply to this email, your message will be added to the discussion  below:  http://gnuradio.4.n7.nabble.com/Tag-preemption-USRP-sink-tp57286p57342.html  To start a new topic under GnuRadio, email ml-node+s4n2h15@n7.nabble.com  To unsubscribe from GnuRadio, click here  <http://gnuradio.4.n7.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=2&code=c3NhdWxvam9yZ2VAZ21haWwuY29tfDJ8MTQyNzUwNTA3OQ==>  .  NAML  <http://gnuradio.4.n7.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml>    

_______________________________________________  Discuss-gnuradio mailing list  Discuss-gnuradio@gnu.org  https://lists.gnu.org/mailman/listinfo/discuss-gnuradio