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Re: [Discuss-gnuradio] Setting up clock synchronization blocks
From: |
Martin Braun (CEL) |
Subject: |
Re: [Discuss-gnuradio] Setting up clock synchronization blocks |
Date: |
Thu, 21 Feb 2013 11:33:32 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Hi Nemanja,
I remember having some trouble with this, as well, but I can't quite
remember the details.
However, since you're using a pretty long preamble, have you tried
using that for sync? The problem with M&M is that the output of the
phase demodulator is quite 'soft', so accurate syncing is difficult in
any case. Using the preamble makes it much easier; if you start with an
oversampling rate of 4 you don't even need to do any polyphase-stuff.
MB
On Mon, Feb 18, 2013 at 05:23:04PM +0100, Nemanja Savic wrote:
> Hi guys,
>
>
> I am trying for quite some time to tweak M&M synchronizationi block, but the
> problem is I have a lot of single bit errors, and I suppose it shouldn't be
> like that because signal I am providing is almost ideal. Here are some
> important features of the communication itself:
>
>
> - data is encoded using differential manchester code
>
> - modulation scheme is FSK with frequency deviation of arround 75KHz
>
> - symbol rate is 19200 KBaud
>
>
> I suppose for this simple communication protocol, I should have much better
> results. Frame starts with preamble, followed by 160 symbols, which is 10
> bytes
> of data at the end. Preamble has following structure
> 10011001100110011001100110011010. The percentage of sucesfully received
> preamble is 1005, but then comes trouble.
>
>
> Setup is following: usrp1 with sample rate od 507937 Sps (I set 512KSps but
> device doesn't support this rate), then comes bandpass filter, followed by
> quadrature demodulator and bit slicer. Bit slicer is connected to correlate
> access code block which is connected to modified framer sink block.
>
>
> Here I provide output of my bit slicer (which I am proud of :)), and hope
> somebody of you guys can provide me advices based on your experience.
>
>
> Many regardsInline image 1
>
>
> --
> Nemanja Savić
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
--
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)
Dipl.-Ing. Martin Braun
Research Associate
Kaiserstraße 12
Building 05.01
76131 Karlsruhe
Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu
KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
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