Is Simple Framer and Simple Correllator blocks will synchronize my data?

GNU Radio
1

Hi all,
I am working on QPSK Transceiver I have done all the synchronization at
receiver except frame delays means frame synchronization is lift. there
are
some delays in my recieved data at start I have some garbage values this
delay is due to filters because filters produce one output sample for N
input samples (N filter Taps). I want to remove this delay so please any
one guide me can simple framer and simple correlator will be used for
this
purpose? I am currently trying to design my own out of tree blocks for
frame synchronization but if the these two blocks(simple framer and
simple
correlator ) are suitable for this purpose or some modification is
required
in its code so that I can use it for my purpose.

any help will be much appreciated and may your help will solve my many
problems of this transciever please help me if YOU CAN.

Regards ,
Irfan U.

2

Hi Irfan,

you can’t remove a filter delay.

If all of your sync is working, the packet encoder/decoder is probably
what you want to use – although I think I remember you’ve tried that
before…?
In any case, to get rid of transients, prepend a preamble to your
signal. As for the simple_* blocks, I don’t think they work well over
lossy channels (the packet decoder will allow some slack w.r.t. bit
errors).

Cheers,
M

3

On Tue, May 27, 2014 at 3:51 AM, Martin B.
[email protected]wrote:

Cheers,
M

Irfan,

Also check out the correlate_access_code blocks. There are a few
different
versions of these for different purposes. The tag version might be
useful:

http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1correlate__access__code__tag__bb.html

And a brand new version that was just checked in last week
(documentation
on the web isn’t updated for this since it’s not in a release yet)
called
correlate_access_code_ff_ts that takes floats in, finds the access code,
and produces a tagged stream out. What this means is that the block
strips
off the access code and creates a stream of just the payload with a tag
to
mark the start of the payload where the tag holds the payload’s length.
It
uses floats because it expects soft decisions and was designed to work
with
FEC.

Tom