Symbol synchronization in Packet Radio

GNU Radio
1

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.

Also it would be great for us if someone can tell me use of Access code
in
addition to Preamble in a transmitted packet.

Thanks in advance.

Regards,
Tarun

2

Quoting Tarun T. [email protected]:

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