Forum: GNU Radio difference b/w sample rate and symbols per second

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jason sam (Guest)
on 2014-06-26 11:07
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Hi,
I am bit confused b/w the two terms.I have read some material and i
got the following relationship b/w the two:
samples/second =samples/symbol * symbols/second
And i think in GRC samples per symbol is 1(plz correct if i am
wrong).So sample rate becomes equal to baud rate(symbols/second)??
Regards,
Ali
Martin Braun (Guest)
on 2014-07-01 11:19
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On 06/26/2014 11:06 AM, jason sam wrote:
> I am bit confused b/w the two terms.I have read some material and i
> got the following relationship b/w the two:
> samples/second =samples/symbol * symbols/second
> And i think in GRC samples per symbol is 1(plz correct if i am
> wrong).So sample rate becomes equal to baud rate(symbols/second)??

samples per symbol is whatever you set it to; common values are 2 and 4
(this also depends on the modulation used). Higher values are often used
for demo purposes.

M
jason sam (Guest)
on 2014-07-04 08:34
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Thanx Martin,but where in GRC we can set samples per symbol??I am new
to this so i don't know yet...

Ali
Marcus Müller (Guest)
on 2014-07-04 15:09
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Hi Ali,
as said several times: Sampling rate, samples per symbol etc are
concepts that are meaningful only for certain blocks, and thus there is
no sense in setting those globally.

Greetings,
Marcus
jason sam (Guest)
on 2014-07-04 17:39
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Yes Marcus,u are r right and i am also asking about such blocks like
the FM Mod block..In this block u have an option to set sample rate
but how can u set samples per symbol??
Marcus Müller (Guest)
on 2014-07-04 18:15
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Not at all, because for these blocks, symbols have no meaning.
jason sam (Guest)
on 2014-07-05 10:00
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Sorry for prolonging the discussion but I am a bit confused here.The
sensitivity parameter for Freq Mod block is defined as:

sensitivity = (pi * modulation_index) / samples_per_symbol
where,

modulation_index = deviation / (baud_rate / 2)

So what values should i plug in for samples_per_symbol and baud_rate
in the formulas?
Marcus Müller (Guest)
on 2014-07-05 16:01
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We might be talking about different blocks.
I'm referring to gr::analog::frequency_modulator_fc, where the
documentation only says[1]

radians/sample = amplitude * sensitivity

From what you paste as formulas this does not look like the general
frequency modulation, but like a digital modulation scheme, e.g. GMSK.

Anyway, we will not be able to tell you what you'll need to use as
parameters for your transmitter -- that is something that you, based on
your communication engineering skills, will need to decide yourself.

Sincerely,
Marcus Müller

[1]http://gnuradio.org/doc/doxygen/classgr_1_1analog_...
Vanush Vaswani (Guest)
on 2014-07-05 16:20
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You may refer to this example to see how to transmit 9.6kbps GFSK
signal through an AWGN channel.

https://www.youtube.com/watch?v=N1hR6VgWeow&featur...
jason sam (Guest)
on 2014-07-05 17:38
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ok thanx for the replies!
Dan CaJacob (Guest)
on 2014-07-05 20:02
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Also, see
http://gnuradio.org/redmine/projects/gnuradio/wiki...
where
some of my own questions have been answered.

Very Respectfully,

Dan CaJacob
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