On Apr 2, 2010, at 9:08 PM, Phillip Walsh <[email protected]>
wrote:
Solved it:
Installed an old version, GnuRadio 3.1.1, I had on disk and the rev
4.3 USRP1s seem to work fine now on that.
Is this a known/common issue?
On Fri, Apr 2, 2010 at 2:44 PM, Phillip Walsh <[email protected]
> wrote:
I am absolutely stumped, any help with this would again be greatly
appreciated.
Last week I had a question trying to get USRP2 to work in my MAC
testbed. I decided not to worry about that for the time being and
borrowed 2 USRP1s from another research group to finish a project.
However, I am not unable to get benchmark_tx/rx.py or obviously
tunnel.py to work with these USRPs as I have hundreds of times
before with the other USRPs.
My first 2 USRP1 are Rev 4.5.
I have 4 RFX2400 Rev 30, tested all successfully on 4.5.
USRP1s in question are Rev 4.3.
GNU Radio 3.3.2
The Rev 4.3 transmits a waveform that appears on rev 4.5 FFT as a
good gmsk (tried dbpsk also) signal. I set the TX amplitude to 5000
and RX gain to 30, but have tried many many values. The rev 4.3
will not successfully decode the rev 4.5 signal either.
Literally when I swap the USRPs out with the exact same set up, it
works with rev 4.5 boxes. I have tested the usrp 4.3s including
FFT, siggen, etc. and everything else seems fine other than packet
decode and correct transmitting. I also tried RFX900's between
those two with no avail.
I've tried all the parameters I could think. Do I need to use a
specific older GR revision? Special decimation, interpolation,
samples/symbol, etc?
As a side note: the simple reliable MAC I have implemented which
includes RTS/CTS (w/ threshold), ACK, multi-hop, multiframe transmit
is working great (so far). I look forward to publishing it for the
community when I finish this project.
Regards,
Phil Walsh
Auburn University
It's likely that the new USRPs you're using have frequencies that are
too far apart from each other. This is a particular problem with the
higher frequency boards. Using usrp_fft.py, try to see what the
frequency offset is and compensate for it to some degree.
The older version of GNU Radio you got working I think did the
acquisition slightly differently and was able to handle the larger
frequency offset.
The new v2 code for the digital modulations in the Git tree should
correct this, too.
Tom
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