Thank you for your reply! I ran the ./bbn_80211b_tap.py and then I used Ctrl-C to stop the bbn_80211b_tap.py. After that I ran ./bbn_80211b_tap.py again. However, I got the error as follows:
bbn_tap: created tap device gr1 usrp_open_interface:usb_claim_interface: failed interface 1 could not claim interface 1: Device or resource busy usrp_basic_tx: can't open tx interface Traceback (most recent call last): File "./bbn_80211b_tap.py", line 137, in <module> main () File "./bbn_80211b_tap.py", line 127, in main app = app_flow_graph(mac.rx_callback, options) File "./bbn_80211b_tap.py", line 63, in __init__ options.barker) File "/usr/local/src/BBN_02192009/adroitgrdevel/gr-bbn/src/examples/bbn_80211b_transmit_path.py", line 40, in __init__ self.u = usrp.sink_c() File "/usr/local/lib/python2.5/site-packages/gnuradio/usrp.py", line 214, in __init__ fpga_filename, firmware_filename) File "/usr/local/lib/python2.5/site-packages/gnuradio/usrp1.py", line 710, in sink_c return _usrp1.sink_c(*args) RuntimeError: can't open usrp1 bbn_tap: destroying tap device gr1 I guess that I did not stop the ./bbn_80211b_tap.py correctly at the first time. What should I do to avoid this kind of error? Thank you, Jane ________________________________ From: Doug Geiger <doug.gei...@gmail.com> To: Jane Chen <janechen_1...@yahoo.com> Cc: discuss-gnuradio@gnu.org Sent: Saturday, February 21, 2009 8:52:34 AM Subject: Re: [Discuss-gnuradio] Beacon frames of BBN 802.11 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Jane Chen wrote: > Hi all, > > > > I ran bbn_80211b_rx.py and got the information as follows: > > PKT: len=163, rssi=-18, src=00:15:aa:55:6C:82, time=13720, rate=1 Mbps > > PKT: len=163, rssi=-23, src=00:15:aa:55:6C:D2, time=21272, rate=1 Mbps > > ....... > > > > // > > According to the information of packets, I don't think I can know if > these packets are beacon frames or not because I don't know the subtype > of the frame. However, on the [Discuss-gnuradio] 802.11 on USRP+GNURadio > : "/Looking at the archives, I understand that I can receive 1 Mbps > probe/beacon packets with code developed by BBN",/ it seems I can know > if the packets are beacon frames. Can anyone tell me how to know if > these packets are beacon frames if it is possible? Thank you! > > > > Jane > The BBN 802.11 code can currently only deal with 1 and 2Mbps packets (i.e. using either DBPSK or DQPSK modulation and DSSS with length-11 Barker Code). Since most WiFi traffic these days tends to be at higher data rates (unless the client is far away from the access point, or something similar), beacon frames are typically the only traffic that you will see with those rates: so it may be safe to assume that those frames you are seeing are in fact beacons (or it may not, depending on what sorts of wifi devices you have around). If you get bbn_80211b_tap.py running you should be able to run either tcpdump or wireshark on the tap/tun interface it creates and you can get some more information about the packets. Doug - -- Doug Geiger Research Assistant Communications and Signal Processing Lab Oklahoma State University doug.gei...@gmail.com doug.gei...@ieee.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkmgMQ0ACgkQPJjTsCiwNz5RnQCdElxk5Ds26hffjBctWf8PdHz+ 03UAoIQPKAQYZlcGw+iYclOaPkZrq1mX =n65j -----END PGP SIGNATURE-----
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