On 06/01/2011 03:41 PM, Thomas Arcuri wrote:
Hello all,
Currently I am testing a modified version of tunnel.py, but I am
seeing some strange results. My modifications were essentially a
re-factoring to prepare for future additions, however somehow I was
able to receive a transmitted packet on the same USRP that transmitted it.
The USRP transmit/receive paths are set-up exactly the same as in the
original tunnel.py, the only difference is that I abstracted the
tun/tap layer a bit (in order to improve the MAC layer functionality).
I did not change the cs_mac loop and I am only using a single USRP
with the modified tunnel to flood PING requests. I am using only a
single antenna on a WBX d'board.
I know that I am receiving a transmitted packet because in
phy_rx_callback() I am using scapy to dump the packet and inspect its
contents. This doesn't happen consistently - I am flooding out PING
requests but only a relative few are "looped back" (for lack of a
better word).
Now, can anyone explain how this could possibly happen?
Thanks,
Tom
Put an antenna on the RX port, and you'll get much more consistent
results--that is, you'll receive *ALL* your packets. Even without an
antenna,
there's enough TX energy coupled into the RX port to receive data,
but not reliably. The receiver doesn't shut-down during transmit.
If you want that behaviour, you have to arrange for it yourself, but
muting the RX side when you transmit, or similar.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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