Date: Wed, 27 Jul 2005 17:45:26 -0500 From: Sam Pierson <samuel.pierson@gmail.com> To: David Malone <dwmalone@maths.tcd.ie> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Atheros, hardware access layer, collisions Message-ID: <d9204e4c05072715452b4d9d9d@mail.gmail.com> In-Reply-To: <200507261513.aa10533@salmon.maths.tcd.ie> References: <d9204e4c05072520052082b27@mail.gmail.com> <200507261513.aa10533@salmon.maths.tcd.ie>
next in thread | previous in thread | raw e-mail | index | archive | help
On 7/26/05, David Malone <dwmalone@maths.tcd.ie> wrote:
> That's correct, but it probably takes a few microseconds for the
> carries sense to kick in (if there wasn't a delay there would
> be almost no need for the random backoff). That's why you'll
> also have to have your transmissions synchronised very closely.
> David.
Since my project is running in adhoc mode, I noticed that there is
a LOT of noise being generated by the two machines I want to use
in order to generate a collision. The noise is the adhoc beacon
being broadcast. Clearly they need to talk to each other, but I'd
really like to quiet down the channel so I can attempt this collision.
I found this in if_ath:
/* NB: the beacon interval is kept internally in TU's */
and this in /sys/contrib/dev/ath/ah_desc.h
=09HAL_TX_QUEUE_BEACON=09=3D 2,=09=09/* beacon xmit q */
=09HAL_TX_QUEUE_CAB=09=3D 3,=09=09/* "crap after beacon" xmit q */
and...
# cat ah.h | grep interval
* beacon interval (given in TU's) can also include flags
u_int32_t bs_intval; /* beacon interval+flags */
#define HAL_BEACON_PERIOD 0x0000ffff /* beacon interval period *=
/
I think the carrier sensing is kicking in because the channel is not quiet
due to the beacons. Do the tx q things matter? seems like the=20
hal_beacon_period would be the most important line, but I don't see how
that flag (if it is one) can be used.
-Sam
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?d9204e4c05072715452b4d9d9d>