Dhrubojyoti,

In ur program u have set the Bitrate rate to 2MB/s. It exceeds the
computing power of ur PC that is why u are getting "OOOO". These 'O' means
overflow i.e. USRP is producing data at faster rate than the ability of PC
to process
Try changing bitrate to 100-500 KB/s

-Adeel

On Sun, Jan 8, 2012 at 4:01 PM, Dhrubojyoti Roy
<dhrubojyoti....@gmail.com>wrote:

> Hi All,
>
> I´m new to GNUradio and have run into the basic problem of the receiver
> USRP device not being able to decode the senderś transmission. For our
> experiments, we used GNUradio (MAJOR_VERSION=3, API_COMPAT=5,
> MINOR_VERSION=1) and USRP N210 with XCVR2450 daughterboards, and the
> benchmark_tx/rx programs for both narrowband and ofdm. We used the
> following transmitter arguments and got the result below:
>
> *./benchmark_tx.py -f 2.4G -r 2M -M 10 -v
> *
> linux; GNU C++ version 4.5.2; Boost_104200; UHD_003.004.000-f2388c0
>
> >>> gr_fir_ccf: using SSE
>
> Modulator:
> bits per symbol:     4
> RRC roll-off factor: 0.35
> -- Opening a USRP2/N-Series device...
> -- Current recv frame size: 1472 bytes
> -- Current send frame size: 1472 bytes
>
> No gain specified.
> Setting gain to 17.500000 (from [0.000000, 35.000000])
>
> UHD Transmitter:
> Args:
> Freq:        2.4GHz
> Gain:        17.500000 dB
> Sample Rate: 1Msps
> Antenna:     None
> Subdev Sec:  None
>
> Modulator:
> bits per symbol:     4
> RRC roll-off factor: 0.35
> Tx amplitude     0.25
> modulation:      psk_mod
> bitrate:         2Mb/s
> samples/symbol:  2.0000
> Differential:    True
> ...........................................................(sending the
> data)
>
> We invoked the receiver as follows:
>
> *./benchmark_rx.py -f 2.4G -r 2M -v*
>
> linux; GNU C++ version 4.5.2; Boost_104200; UHD_003.004.000-f2388c0
>
> >>> gr_fir_ccf: using SSE
>
> Demodulator:
> bits per symbol:     4
> RRC roll-off factor: 0.35
> FLL bandwidth:       6.28e-02
> Timing bandwidth:    6.28e-02
> Phase bandwidth:     6.28e-02
> -- Opening a USRP2/N-Series device...
> -- Current recv frame size: 1472 bytes
> -- Current send frame size: 1472 bytes
>
> No gain specified.
> Setting gain to 49.500000 (from [0.000000, 99.000000])
>
> UHD Receiver:
> UHD Args:
> Freq:        2.4GHz
> Gain:        49.500000 dB
> Sample Rate: 1Msps
> Antenna:     None
> Spec:        None
>
> Demodulator:
> bits per symbol:     4
> RRC roll-off factor: 0.35
> FLL bandwidth:       6.28e-02
> Timing bandwidth:    6.28e-02
> Phase bandwidth:     6.28e-02
>
> Receive Path:
> modulation:      psk_demod
> bitrate:         2Mb/s
> samples/symbol:  2.0000
> Differential:    True
>
> At this point, even with the transmitter running, the receiver program
> pauses for about a minute before bursting into a string of ´O´s. We found
> that our transmission was being detected by the receiving USRP, using the
> uhd_fft.py program. However, an interesting observation was that our signal
> was detected at center frequency 2.401GHz (screenshot attached). We doubt
> if this is due to oscillator differences, since switching the transmitter
> and receiver devices also resulted in detection at the same 2.401GHz center
> frequency.
>
> We tried variations to the above programs by making the 
> *benchmark_rx.py*listen in th 2.401GHz frequency, other modulation schemes 
> such as qam,
> different transmission gains and also the OFDM benchmarks with similar
> variations, but there was no output on the receiver. Could it be possible
> that the receiver can detect but cannot decode the signal? Your valuable
> advice in this regard would be sincerely appreciated.
>
> Thanks and Regards,
> Dhrubojyoti.
>
> --
> Dhrubojyoti Roy
> 1655, North 4th Street, Apt-D
> Columbus, OH-43201
> Contact no.: +1-740-417-5890
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

Reply via email to