How to plot a constellation without symbol decision

[pv]

Hello to all,
I'm using the ofdm rx flowgraph from gr digital to receive a ofdm  
signal generated by the ofdm tx flowgraph. The transmission is made by  
an USRP Ettus Research N210 in a loopback setup. In the transmitter  
side, I make a quantization of the generated signal before  
transmitting it. At the receiver side, the ofdm frame equalizer block  
outputs the constellation already decided and I don't want that. I  
would like to see the constellation without symbol decision, in order  
to analyze the EVM with the quantization noise. Basically, I woul like  
to see something like the attached image.
I have already tried to explore the c++ code of the ofdm frame  
equalizer block  
(https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/ofdm_frame_equalizer_vcvc_impl.cc) in order to disable the decision_maker function but I'm not sure if that is the right thing to  
do.

PS -> the quantized constellation in the figure is not in real time  
with the simulation, that's why I can't use it.

Can anyone help me with this?

Best Regards,
Pedro


--
Pedro Viegas
DSP Engineer
Koala Tech
phone: +351 917 354 070
e-mail: pv@koalatech.pt

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