Dev Ramudit wrote:
Hello all,
Running the new ofdm benchmark code doesn't seem to be working
quite right. I only receive packets when I start the rx side while the
tx side is already running, and even then I receive:
on one:
$ python benchmark_ofdm_tx.py -f 907M
on the other:
$ python benchmark_ofdm_rx.py -f 907M
ok: False pktno: 69 n_rcvd: 1 n_right: 0
ok: False pktno: 79 n_rcvd: 2 n_right: 0
ok: False pktno: 83 n_rcvd: 3 n_right: 0
ok: False pktno: 97 n_rcvd: 4 n_right: 0
ok: False pktno: 111 n_rcvd: 5 n_right: 0
etc...
Restarting the tx side yields more received packets. However if the rx
side is ever started when the tx side is not running, nothing ever
gets received. Benchmark_loopback, the old benchmark_ofdm_* code and
the new and old digital benchmark_* programs all run perfectly with
these two computers/usrps. Any suggestions?
Thanks,
Dev Ramudit
Dev,
We're still working on this code. I don't have much time to work with
two USRPs where I am right now, so I've only been working in the
loopback case and not over the air. In loopback mode, things look good
under various SNRs, frequency offsets, and multipath conditions. There
is a problem with the reciever locking up under certain conditions
because of the peak detector. In loopback, this is with a low SNR, so no
signal would probably trigger this pretty quickly. We have a possible
solution for this, but I don't know when I'll have time to work on it.
The other things to look at is the transmit power, decimation rate, and
interpolation rates. Scale the power so you have enough signal strength
at the receiver but not so much that you start clipping (remember the
high peak to average power ratio in an OFDM signal). I think we found
~2000 for --tx-amp was ok.
Tom
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