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

From: Colby Boyer
Subject: Re: [Discuss-gnuradio] appending preamble with different power
Date: Thu, 23 Jun 2011 11:14:13 -0700

I'm a bit confused. What exactly are you trying to do?

On Thu, Jun 23, 2011 at 9:17 AM, Songsong Gee <address@hidden> 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 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:

My question is that, how many samples after DPSK mod or frequency mod block corresponds to each sample from file source?
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

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)

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