From: David Young <dyoung-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
To: "radiotap-sUITvd46vNxg9hUCZPvPmw@public.gmane.org"
<radiotap-sUITvd46vNxg9hUCZPvPmw@public.gmane.org>
Subject: Re: TSFT
Date: Sat, 17 Nov 2012 00:48:49 -0600 [thread overview]
Message-ID: <20121117064848.GO21779@pixotech.com> (raw)
In-Reply-To: <50A72E17.6070207-vp0mx6+5gkqFX2APIN6yfw@public.gmane.org>
On Fri, Nov 16, 2012 at 10:26:31PM -0800, Simon Barber wrote:
> This is the current definition of TSFT:
>
> "Value in microseconds of the MAC's 64-bit 802.11 Time
> Synchronization Function timer when the first bit of the MPDU
> arrived at the MAC. For received frames only."
>
> My experience with TSFT is with Atheros cards, which record the
> timestamp at the end of the frame, not the start.
Interesting. Is it consistent across the whole Atheros product line?
> Furthermore for DSSS/CCK the definition above is reasonable, but for
> OFDM and HT (802.11n) the SIGNAL field (part of the PLCP header, not
> part of the MPDU) is part of the first data symbol. It would be much
> clearer to change the definition to state that the timestamp is at
> the start of this first SIGNAL/data symbol. Any objections to doing
> this, or preference to change the reference point to a different
> part of the frame?
>
> In my wireshark patch I've added options to interpret TSFT as the
> start of end of the frame.
I think we need 1) a methodology for an author to identify their
device's reference point so that they can calibrate their driver to the
standard and/or 2) a radiotap datum that identifies the reference point
in use or 3) something entirely different.
Dave
--
David Young
dyoung-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org Urbana, IL (217) 721-9981
next prev parent reply other threads:[~2012-11-17 6:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-17 6:26 TSFT Simon Barber
[not found] ` <50A72E17.6070207-vp0mx6+5gkqFX2APIN6yfw@public.gmane.org>
2012-11-17 6:48 ` David Young [this message]
[not found] ` <20121117064848.GO21779-Gq8g4XVd89tWk0Htik3J/w@public.gmane.org>
2012-11-17 8:45 ` TSFT Johannes Berg
[not found] ` <1353141950.9543.3.camel-8Nb76shvtaUJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2012-11-17 17:46 ` TSFT David Young
[not found] ` <20121117174600.GQ21779-Gq8g4XVd89tWk0Htik3J/w@public.gmane.org>
2012-11-17 18:43 ` TSFT Johannes Berg
2012-11-17 18:56 ` TSFT Guy Harris
2012-11-17 23:26 ` TSFT Thomas Pedersen
2012-11-18 7:20 ` TSFT Simon Barber
[not found] ` <50A88C3D.5030809-vp0mx6+5gkqFX2APIN6yfw@public.gmane.org>
2012-11-18 11:07 ` TSFT Johannes Berg
[not found] ` <1353236845.9649.6.camel-8Nb76shvtaUJvtFkdXX2HixXY32XiHfO@public.gmane.org>
2012-11-20 22:43 ` TSFT Simon Barber
[not found] ` <50AC0791.3040005-vp0mx6+5gkqFX2APIN6yfw@public.gmane.org>
2012-11-21 10:42 ` TSFT Johannes Berg
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