Re: [Discuss-gnuradio] Problem with USRP!

[Marcus D. Leech]

> We just removed the throttle blocks and the same problem remains. Please let
> us know how to achieve symbol synchronization.
Well, you're using DPSK, but not using a differential encoder on the TX 
side, nor a differential decoder on the RX side.

> huzaifazafar108 wrote:
> > Dear John,
> >
> > Thank you for such a prompt reply. Okay, we will remove the throttle
> > blocks just now. But can you guide us how to achieve symbol
> > synchronization then?
> >
> > Best Regards,
> > Huzaifa
> >
> >
> >
> > John Malsbury wrote:
> > > You do not need to use throttles when using a UHD sink/source, because
> > > the device provides timing for the flowgraph.
> > >
> > > Remove the throttles and try again.  If you still see the failure I'd
> > > say you are not achieving symbol sync.
> > >
> > > -John
> > >
> > >
> > >
> > > On 04/08/2012 01:58 PM, Huzaifa Zafar wrote:
> > > > Dear all,
> > > >
> > > > I am working with 3 people on a project involving GNU Radio and USRP1.
> > > > We have tried to implement a simple point to point digital
> > > > communication system in GRC involving DQPSK modulation. Using a vector
> > > > source we are sending a finite stream of zeros and ones (the vector
> > > > source has Repeat set to yes). On the receiver side, what we receive
> > > > is really very strange: The same stream of zeros and ones, but with
> > > > extra zeros in between our actual data. For example, we send three
> > > > ones and three zeros, but what we receive is a one followed by seven
> > > > zeros, another one followed by seven zeros, another one followed by
> > > > seven zeros, and then a zero followed by seven zeros e.t.c. We tried
> > > > to experiment more by using the 'KEEP 1 in N' block and the
> > > > 'DECIMATING FIR FILTER', but things are not working out the way they
> > > > should.
> > > >
> > > > I am also attaching a snapshot of the .grc file for your reference.
> > > > Please tell us the reason why these extra zeros are present between
> > > > our data bits, and the way to combat this effect (remember that the
> > > > decimating fir filter and keep 1 in N block are not showing the
> > > > desired output). Any kind of help is appreciated in advance.
> > > >
> > > > --
> > > > Huzaifa Zafar
> > > >
> > > >
> > > > _______________________________________________
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> > > > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> > >
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--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org