Tips for improving file transfer data loss

I’m looking for some tips on how to improve file transfer using two
USRP’s.
I understand the method I’m using might be fairly crude, but I’m just
starting out.

Problem is I’m dropping a lot of data out of the file (receiving missing
parts of a string and such). This gets really bad when one of the USRP’s
is
moving.

File Source > Packet Encoder > GMSK Mod > USRPB100 Sink

USRP B100 Source > Xlating FIR Filter (LP 100khz) > GMSK Demod > Packet
Decoder > File Sink.

I want to try and add some FEC, however, the only FEC blocks that ship
with
GNURadio say “This package is for continuous data, not packetized”. Any
FEC
tips would be nice.

Is there anything wrong/bad with this flow graph for sending files? Or
perhaps a better solution? I understand there could be a heap of
problems
not relating to GNURadio, but I’m sending the files in the middle of a
very
large (>1mile square) open field , with good line of sight.

Cheers,

Ken

On Tue, Apr 8, 2014 at 1:42 PM, Ken A. [email protected] wrote:

USRP B100 Source > Xlating FIR Filter (LP 100khz) > GMSK Demod > Packet

Cheers,

Ken

Ken,

There’s lots that can go wrong between the transmitter and receiver. As
you’ve already identified, there’s no FEC here, so nothing to fix an
error.
Even a single bit error in a packet will cause you to lose that packet
because of the CRC check.

At our latest hackfest, we worked (among other things) on two things:
our
new FEC system and gr-mac. The FEC API system will allow you to apply
FECs
to packetized data, and gr-mac has ARQ. See the notes from the event for
where things are:

http://gnuradio.org/redmine/projects/gnuradio/wiki/Hackfest1403-2

Tom

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