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Re: [Discuss-gnuradio] Symbol synchronization in Packet Radio.
From: |
trondeau |
Subject: |
Re: [Discuss-gnuradio] Symbol synchronization in Packet Radio. |
Date: |
Thu, 14 Dec 2006 00:40:58 -0500 |
User-agent: |
Internet Messaging Program (IMP) 3.2.8 |
Quoting Tarun Tiwari <address@hidden>:
> Hi,
>
> Can somebody enlighten me about the symbol synchronization in Packet Radio
> example? I was wondering if someone can tell me which scheme is being used
> for it.
>
> It will be helpful if one can give me reference to the GNU Radio module
> where I can read the codes line by line to understand it. I need that for
> our project in MIMO systems. We guys at University of Texas, Dallas are
> trying to do some testing on GNU Radio for MIMO fading channels. So, I need
> to know how and when I should sample a recieved packet on different
> receivers.
>
We use a modified Mueller & Muller for I&Q data, which is located in
/lib/general/gr_clock_recovery_mm_cc.*
There is a reference to a paper that explains its implemention inside the code.
> Also it would be great for us if someone can tell me use of Access code in
> addition to Preamble in a transmitted packet.
The preamble is used for AGC and frequency/phase synchronization (Costas loops
in BPSK and QPSK) while the access code allows us to correlate with a packet
and understand where the MAC-layer frame begins. The default access code in the
current implementation is based on GSM access codes (I think).
> Thanks in advance.
>
> Regards,
> Tarun
>
Tom