Re: [Discuss-gnuradio] QPSK demodulation using GRC constellation decoder not working

[Martin Braun]

You're not resolving the \pi/2 ambiguities. I guess that's what's wrong
here.

Cheers,
M

On 02/20/2016 03:33 PM, Damindra Bandara wrote:
> Hi,
> 
> I am trying to transmit and receive a file using Ettus USRP and GNU
> Radio Companion. The modulation scheme used is QPSK. I followed the "gnu
> radio tutorial 7:PSK Symbol recovery" . That worked fine and I was able
> to recover the file at the receiver end. That tutorial uses a out of
> tree module "my_qpsk_demod" as the QPSK demodulator. I am trying to
> replace the "my_qpsk_demod" with "constellation decoder" block. I did
> that as  shown in the attached figure. After I did this modification, I
> was not able to receive the file properly. 
> 
> When I observe the constellation plot after the costas loop, I can
> clearly see the four constellation. I really appreciate if you could
> help me to understand what I am doing wrong and get the code working. 
> 
> Thank you very much
> Damindra
> 
> -- 
> Damindra Savithri Bandara,
> PhD in Information Technology (Candidate)
> George Mason University,
> Fairfax,
> Virginia
> 
> 
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