[Discuss-gnuradio] Correlation Estimator Block

[Mojtaba Mansour Abadi]

Hi Cinaed,

Thanks a lot for the complete reply. I appreciate it.

I will implement your suggestions and see what the output will be and let
you know.

Cheers.

Suppose someone asked you to implement your flow graph on a transmitter
and receiver separated by an air gap.
Where would you tap into the signal with the Correlation Estimator?
I would tap into the signal at the end of the receiver - at the virtual
source with the decoded signal - or the very end of the flow chart.
And you've already demonstrated the output of the flow graph is the same
as input, i.e., you can reliably transit and receive a BPSK signal.
Instead of trying to cram all these block into 1 flow graph, there's an
easier way.
Replace the entire flow graph with a Channel Model. Use a complex vector
equal to the sum of the data and preamble. Feed the complex vector into
a complex Stream to Tagged Stream block and then feed the tagged stream
into the Channel Model. Place the Correlation Estimator on the other
side of the Channel Model and you have something that begins to look like
<gnuradio_root>/share/gnuradio/examples/digital/pack
/example_corr_est.grc
Use your Constellation Object to configure the Modulate Vector for BPSK.
And after you've work out all the details of the Correlation Estimator,
you can graph it back onto the original flow graph.
-- Cinaed

Hi Everyone,
I am trying to benefit "Correlation Estimator" block to tag the preamble
of the transmit bit sequence in a QPSK-based system
Data + Preamble -> Constellation Modulator
AGC -> FLL Band-Edge -> Correlation Estimator -> Correlation Estimator
-> Polyphase Clock Sync -> CMA Equaliser -> Costas Loop
Constellation Decoder -> Differential Decoder -> Map -> Unpacked to

Packed

After I execute the flowgraph, for a few seconds everything works fine
and I receive the correct sequences. However, after a while, the
received bits are not correct and their pattern changes periodically.
When I bypass the "Correlation Estimator" block, everything works fine
and I receive the correct data.
I am confused. Is the correlation block suppose to deteriorate the
demodulation performance?
The flowgraph is attached to the email.
--
Regards,
Mansour.
https://www.linkedin.com/in/mojtaba-mansour-abadi-4311b451
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[Cinaed Simson]

There's an excellent example using BPSK in


<gnuradio_root>/share/gnuradio/examples/digital/packet/example_corr_est.grc

Also, you should be using a tagged stream and blocking tag propagation
at the Channel Model.

And since there are no taps in the Channel Model, you really don't need
CMA Equalizer, and the Costas Loop - or even the Polyphase Clock Sync.

Keep it simple until you understand how the above example works.

The first thing I would do is loose the Constellation Modulator at the
beginning.

But don't confuse me with someone who knows what they're doing - I'm
still wandering through the forest.

-- Cinaed

Hi Everyone,
I am trying to benefit "Correlation Estimator" block to tag the preamble
of the transmit bit sequence in a QPSK-based system
Data + Preamble -> Constellation Modulator
AGC -> FLL Band-Edge -> Correlation Estimator -> Correlation Estimator
-> Polyphase Clock Sync -> CMA Equaliser -> Costas Loop
Constellation Decoder -> Differential Decoder -> Map -> Unpacked to Packed
After I execute the flowgraph, for a few seconds everything works fine
and I receive the correct sequences. However, after a while, the
received bits are not correct and their pattern changes periodically.
When I bypass the "Correlation Estimator" block, everything works fine
and I receive the correct data.
I am confused. Is the correlation block suppose to deteriorate the
demodulation performance?
The flowgraph is attached to the email.
--
Regards,
Mansour.
https://www.linkedin.com/in/mojtaba-mansour-abadi-4311b451
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Discuss-gnuradio mailing list
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