Re: [Discuss-gnuradio] Correlation Estimator Block

[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



On 05/24/2017 10:32 AM, Mojtaba Mansour Abadi wrote:
> Hi Everyone,
> 
> 
> I am trying to benefit "Correlation Estimator" block to tag the preamble
> of the transmit bit sequence in a QPSK-based system
> 
> 
> The modulation is done as:
> Data + Preamble -> Constellation Modulator
> 
> 
> The way I am doing the demodulation is:
> AGC -> FLL Band-Edge -> Correlation Estimator -> Correlation Estimator
> -> Polyphase Clock Sync -> CMA Equaliser -> Costas Loop
> 
> The hard decoding is done as:
> 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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