[Discuss-gnuradio] packet interarrival time

[Veljko Pejovic]

Hi,

I'm using two USRP2 with XCVR2450s, gnuradio 3.2.2 and Ubuntu 9.10.

I ran the benchmark_tx/rx example from gnuradio-examples/ofdm and
measured packet inter-arrival times at the receiver. I also modified
the sender to wait for some time (like 200ms) between individual
packets. I also set the msg queue size to one. In python code I'm
printing a bunch of time.time() values to keep the timeline of the
events.

What I observe is the following:
- inter-departure times are constant, the packet size and the bit rate
would of course influence the time spent sending, but that would still
be a relatively small value.
- at the receiver, most packets are received with the inter-arrival
time comparable to the inter-departure time at the sender, however,
occasionally I would see a huge lag between two consecutive packets
(almost a second).

I read the NSDI'09 paper
(http://portal.acm.org/citation.cfm?id=1558984) that talks about USRP1
performance, however, what I observe is way higher delay and it's
USRP2. Thus, I'm sure that there's something I can do to fix this
delay. Any hints?


Cheers,


Veljko