[Discuss-gnuradio] Implementing digital-bert with UHD

[dan . bar . mailinglist]

Hi,

I am currently new to the GNU Radio project and are currently trying to get the 
digital-bert scripts (gnuradio-examples) working with UHD (for my USRP N210).

At the beginning I have swapped the existing USRP sinks in 'benchmark_tx.py' 
and 'benchmark_rx.py' with the code below.
Therefore I changed some command line arguments (ip...IP address of the board, 
gain...Gain of the d'board).

def _setup_usrp(self, interp, freq, gain, ip):
       # Setup single usrp sink
       self._usrp = uhd.single_usrp_sink(
           device_addr="addr="+ip,
           io_type=uhd.io_type.COMPLEX_FLOAT32,
           num_channels=1,
       )

       # Tune to center frequency
       tr = self._usrp.set_center_freq(freq, 0)

       if not (tr):
           print "Failed to tune to center frequency!"
       else:
           print "Actual intermediate frequency:", n2s(tr.actual_inter_freq)

       # Set TX gain
       self._usrp.set_gain(gain, 0)
       print "Gain d'board:", n2s(self._usrp.get_gain()), "dB"

Afterward I executed the scripts and everything seems to work,
but the terminal output shows:

Freq. Offset:  -945 Hz  Timing Offset:   3.7 ppm  Estimated SNR:  6.8 dB  BER: 
0.182979
Freq. Offset: -1011 Hz  Timing Offset:   4.0 ppm  Estimated SNR:  6.8 dB  BER: 
0.182914
Freq. Offset: -1102 Hz  Timing Offset:   3.9 ppm  Estimated SNR:  6.9 dB  BER: 
0.18345
Freq. Offset: -3122 Hz  Timing Offset:   3.5 ppm  Estimated SNR:  7.0 dB  BER: 
0.183047
Freq. Offset:  -748 Hz  Timing Offset:   3.5 ppm  Estimated SNR:  6.9 dB  BER: 
0.184062

So the SNR and BER are quite bad and the values aren't changing, while 
modifying the signal energie (amplitude) for transmition.

Does have anybody an explanation or hint for this behavior? Or are there 
working scripts for UHD available?

Thanks,
Daniel