Forum: GNU Radio a running problem with the USRP, i am confused!

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Bill S. (Guest)
on 2009-05-08 18:29
(Received via mailing list)
Hello,

I tried the DBPSK and DQPSK scheme with benchmark_tx.py and
benchmark_rx.py. I
found there is a problem with USRP. After having TX and RX rest for
20 mins, the communication between them are so good that the PDR
detected at the RX is almost 99%, but after those two USRPs run for a
while, say 10 mins, the communication quality deteriorates rapidly,
which means the synchronization was worsen. Does it mean USRP could not
keep on running for a long time or the USRP boards we are using have
been broken? I do not know the reason for this problem. Please let me
know what's wrong with the USRP. Thanks a lot!

Bill
Jason U. (Guest)
on 2009-05-08 20:36
(Received via mailing list)
> Does it mean USRP could not keep on running for
> a long time or the USRP boards we are using have been broken? I do not know
> the reason for this problem. Please let me know what's wrong with the USRP.
> Thanks a lot!

I believe there is an issue with the costas loop implementation in one
of the older mpsk_receiver implementations where the phase offset
correction gets clipped rather than rolled over (ie, -2pi->2pi).  If
the offset is small it may take awhile for this error to show up.  If
you use the verbose costas loop and see the phase correction going up
to 2pi or down to -2pi and not rolling over you may have this issue.

Jason
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