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] <
[email protected]> 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.
> >>
> >>
> >> _______________________________________________
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> >>
> >> discussion below:
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> >>
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> >>
> >> To start a new topic under GnuRadio, email [hidden email]
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> >> 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
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> >>
> >> --
> >> 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.
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> >>
> >>
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> >>
> >
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>
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--
Saulo Jorge bq
- "Beware of bugs in the above code; I have only proved it correct, not
tried it."
Donald Knuth.
--
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