Re: [Discuss-gnuradio] Tips for improving file transfer data loss

[Tom Rondeau]

On Tue, Apr 8, 2014 at 1:42 PM, Ken Adams <address@hidden> wrote:

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

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