Re: [Discuss-gnuradio] Symbol synchronization in Packet Radio.

[trondeau]

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