[Discuss-gnuradio] Fwd: decode problem in benchmark--NCO?

[Adeel Anwar]

>>For BPSK, not using differential, is there any way to keep track of the rotating so as to understand exactly what happened to each bit? Only after understanding what happens to each bit in a single series of data, I can work on how to joint them correctly.

Other than differential decoding, another way to resolve phase-ambiguity is to send Unique-word (header) in the start. This unique-word will be complemented in BPSK if ther is phase-ambiguity in the received data.

http://ricesimulink.groups.et.byu.net/bpskcr.phtml

-Adeel

On Thu, Jul 18, 2013 at 8:05 PM, yeran <address@hidden> wrote:

Hi Nathan,

Thanks again for your reply!

You are right that I'm not using BPSK instead of DBPSK. Because I'm working on jointly decoding two series of data. Since DBPSK depends on the previous bit of the data, I don't know if I joint the two series how will the differential decoding works.

For BPSK, not using differential, is there any way to keep track of the rotating so as to understand exactly what happened to each bit? Only after understanding what happens to each bit in a single series of data, I can work on how to joint them correctly.

Now I'm trying to revise the C++ code in digital_constellation_receiver_cb.cc by writing the d_phase into a file. I'm guessing if I can combine this with the rx_time_recov.32fc, I will get an idea how the decision is made. You think it's a reasonable way to do experiment?

Also, if using DBPSK, do you know how does the joint decode work?

Thanks and look forward to your reply! :)

Ada

> Date: Wed, 17 Jul 2013 23:54:00 -0400
> Subject: Re: [Discuss-gnuradio] decode problem in benchmark--NCO?
> From: address@hidden
> To: address@hidden

>
> On Wed, Jul 17, 2013 at 11:35 PM, yeran <address@hidden> wrote:
> > Hi,
> >
> > I looked into the digital_constellation_receiver_cb.cc, and find out that
> > the NCO value is for derotating the current sample. But I still don't get
> > how the NCO is calculated, and where the d_phase is from and how it changes
> > with each bit.
>

> Grep is your friend. Look at the header where
> constellation_receiver_cb is defined. It inherits from control_loop.
> control_loop is found in gr-blocks, and has the advance_loop function
> that tracks phase error.

>
> >
> > Do you have any ideas on that?
> >
> > Thanks a lot!
> >
> > Ada
> >
>

> As Tom mentioned I think your problem is the fact that you are not
> using differential encoding, so your entire constellation is getting
> rotated occasionally.
>
> -Nathan

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