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 > >
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