Re: [Discuss-gnuradio] BER & SNR (was: Re: (no subject))

[Rafik ZITOUNI]

Marcus, 

You find attached my flow graph with  Tx and Rx. I know that it is not recommended to have TX and RX in the same flow graph but i did it just to obtain one view for my Tx and Rx. 

Thanks,  

2017-07-04 11:23 GMT+02:00 Marcus Müller <address@hidden>:

Dear Rafik,

I think we're approaching this from the wrong side: I don't think that I should be explaining why you get a good BER and SNR estimate, it is you who should explain why you're expecting something different, and then we can discuss! I'm not quite sure what I could be explaining at this point :)

Best regards,

Marcus

On 07/04/2017 11:20 AM, Rafik ZITOUNI wrote:

Thank you Marcus for your answer !

My BER and SNR are calculated and obtained using MPSK SNR Estimator Probe and Error Rate blocks. I obtained  two points, which rotate in the qt gui constellation sink despite the BER and SNR have been obtained as expected. Could you give me an explanation how it was possible to obtain a good snr and ber with a wrong constellation with  good SNR and BER?

I found the  presentation of Tom Rondeau useful, since he explained the function of the costas loop block.  https://static.squarespace.com/static/543ae9afe4b0c3b808d72acd/543aee1fe4b09162d08633fc/543aee1fe4b09162d0863402/1392309732018/mpsk.pdf


This morning I add a Costas loop after a Polyphase Clock Syncronisation block, and it s going well. You find attached a screenshot of my constellation for a DBPSK of my receiver/transmitter. I propose to add a grc to gnuradio/gr-digital for MPSK since grc is more easy to understand than python source code.

Now I am trying to send and receive data files such as videos or images (bmp). Do you have an example with a file exchange implemented in .py or grc?

Best,  

2017-07-04 9:44 GMT+02:00 Marcus Müller <address@hidden>:

Hi Rafik!

So, what's wrong with the BER and the SNR estimate?

Best regards,

Marcus

On 07/03/2017 11:29 PM, Rafik ZITOUNI wrote:

Dear all, 

I translate the /gr-digital/examples/narrowband/digital_bert_tx.py and the /gr-digital/examples/narrowband/digital_bert_rx.py python source codes to GRC flow graphs. The objective is to get more graphical possibilities with a GRC.  My flow graph gives a fine result of BER and SNR for DBPSK modulation. 

The problem is with the rotating points of my constellation. I think that the rotation of my view comes from a lack of frequency synchronization, but why I obtained a correct BER and SNR?

You find attached to this message a constellation view obtained by my flow graph. 

Please could you explain me this  result or give an advice to improve the obtained result? 

Regards, 

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Rafik

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Rafik

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Rafik