From: Robert Felten <robert.felten@googlemail.com>
To: ath9k-devel@lists.ath9k.org
Subject: [ath9k-devel] Hack ath9k driver for wifi time of flight measurement
Date: Tue, 10 May 2016 08:12:52 +0200 [thread overview]
Message-ID: <CANvZOfNgpQB+v43k_f+4tBJ4mp3L7L4JJDyTiGBYMC-9Eb4yww@mail.gmail.com> (raw)
In-Reply-To: <20160507071657.Horde.vV_XdMu1X1xp2UJdsSuvw9o@webmail.teco.edu>
Hi,
2016-05-07 9:16 GMT+02:00 <schnitzbauer@teco.edu>:
> ...
> 1. Detect the start of packets based on the increased signal strength
> that can be seen in the spectral scan samples.
Are you sure that this is possible? In my observation your spectral
sample stream get interrupted by an decoded frame.
The start of the frame is not visible and there is a small gap between
the last spectral sample and the start of the decoded frame.
If you merge the power information of the spectral samples and frame
it looks like http://imgur.com/xAWleMY
X-axis: subcarrier frequencies 1 per px, y-axis: time, 1 pixel =
115us, captured tl-wn722n with ath9k_htc v1.4
Not sure about the overlap at the end of the frame, probably my
tx_time calculation is not accurate enough.
> 2. Use two devices as receiver. One decodes the frames, the other
> captures spectral scan. Synchronize the captures based on the MAC
> timestamps produced by both chips.
Please share how it is possible to convince the hardware not to
decoded the frame and give only spectral samples instead.
> You may know this paper: dl.acm.org/ft_gateway.cfm?id=2000029 .
> Domenico Giustiniano did a busy loop within the driver code to solve
> the problem with unpredictable scheduling. He is currently working on
> a broadcom platform with a custom firmware
The full text paper is also available:
http://dl.acm.org/citation.cfm?id=2079306
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.381.1215&rep=rep1&type=pdf
> ...
Best,
Robert
prev parent reply other threads:[~2016-05-10 6:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 1:07 [ath9k-devel] Hack ath9k driver for wifi time of flight measurement 王峰
2016-05-07 7:16 ` schnitzbauer at teco.edu
2016-05-10 6:12 ` Robert Felten [this message]
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