Thank you for the response. I was afraid that might be the case :) The following workaround seems to work well (which seems to validate your hypothesis):
When a packet is _not_ being sent, the transmitter outputs a continuous stream of 0-valued samples to the USRP. When a packet _is_ being sent, modulate and sample as usual. Not the ideal solution, but it works. Thanks, Rich On Monday 26 March 2007, John Ackermann N8UR wrote: > Richard Alimi wrote: > > Hello All, > > > > I am currently having a problem with packet transmission similar to the > > one Tom Rondeau had mentioned in his February 14th 2006 post titled > > 'Dropped Packets.' However, there was no general resolution given there. > > > > When I run the dbpsk/dqpsk/gmsk transmitter/receiver under the > > gnuradio-examples directory (revision 4796), it always seems to drop the > > last packet, leading me to believe this hasn't been fully fixed. Using > > the --discontinuous option produces the same result. Even adding a > > time.sleep(1) before fg.wait() doesn't seem to fix it, as suggested by > > that post. > > I am dangerously jumping into a place that I don't understand, but I > have had a similar problem in a non-gnu-radio data system and it's > possible, I suppose, that something similar is going on here. > > The issue is the timing of the signal to turn the TX off versus the time > required to get the last data bit actually on the air. In the AX.25 > packet system in question, the application would unkey the transmitter > as soon as the last payload bit was sent. However, there was a > downstream scrambler that caused a delay of some number of bit times. > We had to set a parameter to keep the TX keyed for a few milliseconds > after the end of data in order to allow all the data in the scrambler to > make it out over the air. In the AX.25 protocol, that was the "txtail" > parameter. > > Again, I have no idea if this applies to your situation, but it caused > us some real head scratching until we figured out what was going on. > > John
pgpM1Q0dSQhFZ.pgp
Description: PGP signature
_______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
