On Mon, Jun 6, 2011 at 8:33 PM, Morgan Redfield <redfie...@gmail.com> wrote:
> Hi Everyone, > > I've been playing around with GNURadio and a couple of USRPs lately, > but I've run into some problems. I'm using a modified version of the > benchmark_ofdm_tx.py and benchmark_ofdm_rx.py scripts. I updated them > to use uhd, and I'm using them with two N210s. Each N210 has a WBX > daughterboard, and they're placed about a meter apart right now. > > I'm attempting to send data from one USRP to the other, but using > tunnel.py or the benchmark_ofdm files doesn't seem to work. I never > receive any packets correctly. > > With the benchmark_ofdm files, if I start receiving before I start > transmitting then I just get TIMEOUTs. If I start transmitting before > I start receiving, I get the following: > > $ python benchmark_ofdm_rx.py -f 650M -v --rate=1M > Mac OS; GNU C++ version 4.0.1 (Apple Inc. build 5490); Boost_104601; > UHD_003.001.000-4eb4025 > > -- Opening a USRP2/N-Series device... > -- Current recv frame size: 1472 bytes > -- Current send frame size: 1472 bytes > -- mboard0 is MIMO master > >>> gr_fir_ccf: using SSE > >>> gr_fir_fff: using SSE > > OFDM Demodulator: > Modulation Type: bpsk > FFT length: 512 > Occupied Tones: 200 > CP length: 128 > ok: False pktno: 21611 n_rcvd: 1 n_right: 0 > ok: False pktno: 43626 n_rcvd: 2 n_right: 0 > ok: False pktno: 21611 n_rcvd: 3 n_right: 0 > ok: False pktno: 37548 n_rcvd: 4 n_right: 0 > ok: False pktno: 21909 n_rcvd: 5 n_right: 0 > ok: False pktno: 4473 n_rcvd: 6 n_right: 0 > ok: False pktno: 27253 n_rcvd: 7 n_right: 0 > ok: False pktno: 38378 n_rcvd: 8 n_right: 0 > ok: False pktno: 21909 n_rcvd: 9 n_right: 0 > ok: False pktno: 38486 n_rcvd: 10 n_right: 0 > ok: False pktno: 54634 n_rcvd: 11 n_right: 0 > ok: False pktno: 21909 n_rcvd: 12 n_right: 0 > ok: False pktno: 39158 n_rcvd: 13 n_right: 0 > ok: False pktno: 27237 n_rcvd: 14 n_right: 0 > ok: False pktno: 42410 n_rcvd: 15 n_right: 0 > ok: False pktno: 21909 n_rcvd: 16 n_right: 0 > ok: False pktno: 21994 n_rcvd: 17 n_right: 0 > ok: False pktno: 21652 n_rcvd: 18 n_right: 0 > ok: False pktno: 21097 n_rcvd: 19 n_right: 0 > ok: False pktno: 43626 n_rcvd: 20 n_right: 0 > ok: False pktno: 21909 n_rcvd: 21 n_right: 0 > TIMEOUT > TIMEOUT > > I think those timeouts at the end there are from when the transmitter > stopped transmitting data. It looks like I'm receiving a few packets > (far fewer than I should), and all the packets I do receive are not > correct. > > Does anyone have any idea what's causing this? > > Thanks > Morgan > TIMEOUTs occur when a preamble has been detected, but then the signal is lost. My thinking is that you are too far off frequency and so the received signal is outside the bandwidth of the receiver. Look at the signal in a FFT plot and see if you can adjust the transmitter's frequency to close the gap. Tom
_______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
