Re: [Discuss-gnuradio] How to calculate SNR?

[Tom Rondeau]

On Wed, Mar 26, 2014 at 8:46 AM, Azza Ben Mosbah
<address@hidden> wrote:
> Ok. Thank you. I will see that.
> A one more question please: the SNR, is it in dB? and why the output for the
> SNR block is complex?
>
> Azza

Azza,

Please try to be more specific with your questions. Notice that there
are two blocks that calculate the SNR of an MPSK signal. Which one are
you talking about? What output are you talking about?

The documentation for the mpsk_snr_est_cc block is found here:
http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1mpsk__snr__est__cc.html#details

It says that this block passes all incoming data on the input stream
to the output stream. You can get the SNR by using the snr() function
to return the current estimate. And notice that in the constructor,
there is an argument:
"after this many samples, a tag containing the SNR (key='snr') will be sent"

So a stream tag is issued every so many samples containing the value
of the SNR estimate.

The other block is the probe_mpsk_snr_est_c, which is a sink:
http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1probe__mpsk__snr__est__c.html

Again, this has an snr() function. Instead of stream tags, this block
emits a message every so many samples. So you can attach a block that
receives messages to get the SNR estimates.

Tom