PROBLEM WITH USRP1 (A newer problem)

For a TX RX path, the following is being setup:

TX: Vector Source → Packet Encoder → DPSK modulator → USRP Sink

RX: USRP Source → DPSK demodulator → Packet Decoder --? WX GUI Scope
Sink

Something interesting happens, and that is, the output on the scope
displays
NOTHING!

Note that the setup is working fine without the packet encoder and
decoder
(i.e. what we transmit is being received and correctly displayed in the
WXGUI Scope Sink).

Also, if we remove the USRP sinks and the source, and just connect the
modulator output to the demodulator input, everything is working fine.

We have also tried to play around with the .grc file provided on the
reply
to a question, on the following link:
http://www.ruby-forum.com/topic/3956225

We tried to introduce a channel model instead of the USRPs in our
system,
and we think that the problem is in the frequency offset. When frequency
offset of the channel model is zero, everything is safe. When it is
increased a little, the scope displays nothing.

If you really think that the problem is in the frequency offset, please
let
us know how to combat that problem!

Any kind of help is appreciated in advance!

Best,
Huzaifa

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We tried to introduce a channel model instead of the USRPs in our system,
and we think that the problem is in the frequency offset. When frequency
offset of the channel model is zero, everything is safe. When it is
increased a little, the scope displays nothing.

If you really think that the problem is in the frequency offset, please let
us know how to combat that problem!

Have you observed the received spectrum? Is there an offset?

http://gnuradio.org/redmine/projects/gnuradio/wiki/FAQ#I-have-two-USRPs-and-when-I-transmit-on-one-and-receive-on-the-other-at-the-same-frequency-I-get-an-offset

Also, you can just increase the symbol rate. So, despite the frequency
shift, your signal still makes it into the demodulator’s passband.

-Josh