You could be running into the issue of frequency offset between the LO's of the two usrp devices. Try increasing the rate so the symbols are wider spectrally to make up for the offset. I believe that its the -r option.

Hope that helps,
-Josh

On 05/18/2010 06:54 PM, Fisheep wrote:

Hi,

I have currently set up a transmission between USRP1 and USRP2 with FLEX900.
And got the following results.

In gnuradio/gnuradio-example/python/digital/
Successful transmission (ok = True) when
   Tx (USRP1) : ./benchmark_tx2.py -f 900M --tx-amplitude=0.4 -m dbpsk2
   Rx (USRP2) : ./benchmark_rx2.py -f 900M -m dbpsk2 -e eth0
Fail (ok = False and lost lots of packets) when
   Tx (USRP2) : ./benchmark_tx2.py -f 900M --tx-amplitude=0.4 -m dbpsk2 -e
eth0
   Rx (USRP1) : ./benchmark_rx2.py -f 900M -m dbpsk2

In addition, if using the original modulation like dbpsk not dbpsk2, the
transmission also not work as expected.

also ref to the two discussions:
http://www.ruby-forum.com/topic/203035
http://www.ruby-forum.com/topic/202105

I successfully transmit packet from USRP1 to USRP2 with the following
parameter setting.
   Tx (USRP1) : benchmark_ofdm_new_tx.py -f 900M --tx-amplitude=0.4 -i 128
   Rx (USRP2) : benchmakr_ofdm_new_rx.py -f 900M -d 100
But the same problem as above, USRP1 can't receive correct packet from
USRP2.

Does anyone has any suggection about this problem, please let me known,
Thanks.

Sincerely,
Fisheep




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