M2m4 SNR estimator off by 3 dB

GNU Radio
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On Wed, Aug 27, 2014 at 9:33 AM, Jared D. [email protected]
wrote:

It’s an easy fix, I just wanted to get verification and notify other users.

Thanks,
Jared.

Hi Jared,

I’d have to review the paper again, but I suspect you’re right. I was
using
this estimator just the other day and scratching my head about the
results.
I was on a plane, though, and was really focused on something else.

Thanks!

Tom

3

On Thu, Aug 28, 2014 at 7:04 AM, Tom R. [email protected] wrote:

  return 10.0*log10(2.0*sqrt(2*y1_2 - d_y2) /

with AWGN, measuring the signal and noise powers separately while

I’d have to review the paper again, but I suspect you’re right. I was
using this estimator just the other day and scratching my head about the
results. I was on a plane, though, and was really focused on something else.

Thanks!

Tom

Just tested this and it looks fine the way it is. Are you doing real or
complex signals? The estimators are designed to work with complex
numbers,
so that might be the difference you’re seeing. I just have a simple
simulation that I can switch between BPSK and QPSK (both complex
signals,
though). I use the MPSK measurement block and calculate the power of the
signal and noise separately and output that to a number sink. With the
current method, I see the same SNRs on both paths.

There is also the gr-digital/examples/snr_estimators.py example you can
explore to compare them.

Tom

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On Thu, Aug 28, 2014 at 10:46 AM, Jared D. [email protected]
wrote:

get 10 dB SNR. This seems consistent with the extra 2 x factor in the
flowgraph so I could compare with mine?

Thanks,
Jared.

Ah, I’ve found the mistake in my tests. I was averaging the signals at
the
wrong place. Threw together the flowgraph too quickly this morning.
(There’s actually a funny story here, but I don’t want to embarrass the
person; so I’ll take on the embarrassment myself for not double checking
things myself.)

This identified that I was making similar mistakes with the other
estimators – I would have forced them all to the same results and must
have based it on a bogus starting target. I’ll check in corrections
soon,
tomorrow hopefully. The skewness estimator is giving me trouble for
non-binary psk signals, though.

Tom