[Discuss-gnuradio] problems with benchmark_ofdm and N210

[Morgan Redfield]

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