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Re: [Discuss-gnuradio] appending preamble with different power

From: Songsong Gee
Subject: Re: [Discuss-gnuradio] appending preamble with different power
Date: Fri, 24 Jun 2011 04:00:48 +0900

Ok. First of all, I'd like to run a code like below (pseudo):
for i = 1 to 200 // preamble duration
  amp = 32767
end for
amp = 100

Next, how many baseband samples are generated by DPSK or Frequency mod block for a single symbol input

Composed with Android (Galaxys)

2011. 6. 24. 오전 3:31에 "Nick Foster" <address@hidden>님이 작성:
> On Fri, 2011-06-24 at 01:17 +0900, Songsong Gee wrote:
>> Continueing with http://www.ruby-forum.com/topic/1983866,
>> I have planned to append a preamble before an actual signal and turn
>> RX on earlier than TX.
>> Then RX will receive a signal like below:
>> |---RX turn on------|---TX turn
>> on-----------------------------
>> (---trash signal---)(---preamble---)(---actual signal---)
>> And this signal is demodulated and stored into a sink file.
>> After that, I run a program that extracts an actual data only and
>> compare it to the original.
>> My concern is that this preamble should be assumed to be perfect i.e.
>> no errors
>> Of course, there isn't no error. However if I set an amplitude to
>> maximum value, it can be said to be no error.
> I don't understand what you mean here. You can find an "imperfect"
> preamble sequence using a correlator.
>> I have a pre-defined preamble sequence with length n (n = around
>> 100-200, can be changed)
>> Thus, I am trying to change amplitude of modulated signal for preamble
>> and actual signal
>> But I have problem with some quadrature modulation. Flow graphs are in
>> below:
>> http://dl.dropbox.com/u/11382666/for_gnuradio_mailinglist/M-DPSK.png
>> http://dl.dropbox.com/u/11382666/for_gnuradio_mailinglist/M-FSK.png
>> My question is that, how many samples after DPSK mod or frequency mod
>> block corresponds to each sample from file source?
> It's right there in the block, where it says "samples/symbol".
>> I have to solve this problem in order to figure out how many samples
>> are generated from preamble with length n.
>> If I know that information, I can set a duration for Multiply const
>> block having large value for preamble and normal value for actual
>> signal
> Why would you set the amplitude of the preamble differently than the
> actual data?
> --n
>> And second question is that, although I know that information, I don't
>> know how I can control value.
>> For example, preamble with length 200, then I want to set large value
>> for duration 200 * x (number of samples generated after DPSK,
>> Frequency mod), and after that I want to set normal value for
>> remaining duration.
>> Is it too complex for gnuradio-companion flow graph to make? And is
>> python hard coding possible?
>> --
>> Seokseong Jeon (aka Songsong Gee)
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> address@hidden
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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