PSK demodulation : get exact point before deciding what is the closest constellation point

GNU Radio
1

Hi all !

I am dealing with PSK (BPSK, QPSK, 8PSK) modulation/demodulation ; in
demodulation, I would want to retrieve the exact point (vector) before
finding the closest constellation point.

Is there any way to get it with d?psk.py codes or whatever else ?

Thanks in advance for your help.

Chris

2

On Mon, Feb 22, 2010 at 12:03:28PM -0500, [email protected]
wrote:

Hi all !

I am dealing with PSK (BPSK, QPSK, 8PSK) modulation/demodulation ;
in demodulation, I would want to retrieve the exact point (vector)
before finding the closest constellation point.
K

Is there any way to get it with d?psk.py codes or whatever else ?

Thanks in advance for your help.

Chris

Chris,

If you look at the code
(gnuradio-core/src/python/gnuradio/blks2impl/dbpsk.py et al.), you’ll
see that you can enable logging (and get all the intermediate values
logged to files) or you could just wire in your own logging stuff
wired in by reaching into the hier_block and connecting away.

Eric

3

Thanks Eric !

I have a few questions more.

1- I’ve successfully retrieved the intermediate values by enabling
logging to files. Though, I’ve no idea about how I “could just wire in
your own logging stuff
wired in by reaching into the hier_block and connecting away”, as an
alternative way to reach the same results.

2- I am using USRP2 with an RFX2400 daughterboard. Datasheets indicate
17dBm for Transmit power, but I cannot find any information about
Receive power. Does anyone know Input power for RFX2400 ?

3- I have only one USRP2 and would like to use a loop-back cable to
connect the output to the input of the same USRP. So I would, for
example, run benchmark_tx and benchmark_rx in two different shells. Can
I do it without any worry ? I am asking the question because it seems
that many people always ran a such test with two USRP (one for Tx and
the second for Rx)

4- My last question refers to the error message “usrp2::tx_raw: FIXME:
short packet: 1 items (32 bytes)” received when I run benchmark_tx with
a modulation other than gmsk. This problem has been the subject of a
couple of posts such as this one :
OSDIR . But it
seems not to have been solved.

Thanks in advance for your help.

Chris

De: Eric B. [mailto:[email protected]]
Date: lun. 22/02/2010 13:20
À: Paring, Christophe
Cc: [email protected]
Objet : Re: [Discuss-gnuradio] PSK demodulation : get exact point before
deciding what is the closest constellation point

On Mon, Feb 22, 2010 at 12:03:28PM -0500, [email protected]
wrote:

Hi all !

I am dealing with PSK (BPSK, QPSK, 8PSK) modulation/demodulation ;
in demodulation, I would want to retrieve the exact point (vector)
before finding the closest constellation point.
K

Is there any way to get it with d?psk.py codes or whatever else ?

Thanks in advance for your help.

Chris

Chris,

If you look at the code
(gnuradio-core/src/python/gnuradio/blks2impl/dbpsk.py et al.), you’ll
see that you can enable logging (and get all the intermediate values
logged to files) or you could just wire in your own logging stuff
wired in by reaching into the hier_block and connecting away.

Eric

4

Thanks in advance for your help.

Eric

Thanks Eric !

I’ve successfully retrieved the intermediate values by enabling logging
to files. Though, I’ve no idea about how I “could just wire in your own
logging stuff wired in by reaching into the hier_block and connecting
away”, as an alternative way to reach the same results.

Chris

P.S. I posted this question in another message that is not smart at all.
Sorry, that is why I’m re-posting it in a better way (after have read
the article "How To Ask Questions The Smart Way
http://www.catb.org/~esr/faqs/smart-questions.html ").