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Re: [Discuss-gnuradio] FLL Band-Edge Detectors: Literature?

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] FLL Band-Edge Detectors: Literature?
Date: Mon, 1 Oct 2012 17:17:33 -0400

On Mon, Oct 1, 2012 at 12:00 PM, Nazmul Islam
<address@hidden> wrote:
> Hello,
> Frederic Harris's "Multirate Signal Processing: for communication systems"
> has a section on FLL band edge sync. I think that the GR-digital code was
> designed based on these algorithms. Tom or other GNUradio block designers
> can verify it.
> Thanks,
> Nazmul
> On Mon, Oct 1, 2012 at 11:40 AM, Martin Braun (CEL) <address@hidden>
> wrote:
>> Hi,
>> is there any literature that goes with the FLL synch blocks in
>> gr-digital? Ironically, Google always points me to the GR source files
>> when I search for 'fll band edge' related topics.
>> M


Yes, harris' book is the best to start with. There is another paper
from him called "Let's Assume the System is Synchronized" that also
goes over it. I'm not sure if he's published a paper that discusses
the specifics of the filter derivation, yet, though. It's based on the
derivative of the half cosine waveform of the  RRC filter rolloff. The
system behaves much better this way than just generating any random
band edge filter.

In theory, this should work for any signal using an RRC pulse shaping.
For specific constellations, you could use a Costas loop with a wider
lock in bandwidth to handle the frequency offset.

Oh, and I might be the only one who calls this the "FLL band edge
filter" specifically to point out that this is only one possible
implementation of an FLL for coarse frequency tracking. Other
algorithms are welcome :)


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