Re: [Discuss-gnuradio] 802.11 on USRP+GNURadio

[Greg Troxel]

  Looking at the archives, I understand that I can receive 1 Mbps
  probe/beacon packets with code developed by BBN. I use their code and
  see packets at 1 Mbps from different nodes.
  However, I don't know of a way to have the USRP as a destination for a
  flow using standard packet generation tools like Iperf. So I setup a

We wrote code to inject the packets (802.11 frames) into a modified
NetBSD tap device that was an 802.11 interface rather than ethernet, and
then were able to use tcpdump.  All of this code is on the
acert.ir.bbn.com server.  We didn't address all the interactions with
the 802.11 state machines in net80211 and the GNU Radio implementation.
So you should be able to port this to Linux, but it's non-trivial.

  UDP flow between a conventional 802.11bg AP and a Laptop. I capture
  the packets on air with the USRP and determine how many of the packets
  of this flow I am able to receive. But here, out of 1000 packets (1500
  bytes each) sent at 1 Mbps, the laptop is able to receive around 900
  packets but the USRP captures somewhere between 100 to 550 packets. I

If the laptop is only gettinng 900, that indicates something is wrong.
Are you sending these back to back as fast as you can?  I'd back off to
200 pps or something like that, and see what happens, and then gradually
increase the rate, watching CPU load.

  am wondering whether this makes sense. I thought that the BBN code
  would capture most of the packets provided the rate is 1 Mbps
  (disregarding probe packets from other APs). But this does not seem to
  happen..

We did get most packets given a reasonable load

  I use gnuradio-3.1.2 on Ubuntu Dapper with a 2 GHz Intel core duo
  processor and 2 GB RAM.

We had 1.6 GHz Pentium M with 2 GB RAM (Thinkpad T43), with NetBSD
current from summer 2006 (pre 4.0).