From mboxrd@z Thu Jan 1 00:00:00 1970 From: Date: Mon, 13 Jun 2016 06:24:26 -0000 Subject: No subject Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ath9k-devel@lists.ath9k.org seems to be effective. But I'm not sure. And sometimes, some phase measurement show large dispalcement along y-axis even they are captured within very short duration. Hence the question is, Is ath9k reports CSI with those unwanted linear phase offset removed? If it is not, should I look into Atheros CSI tool? As I look into it, it just captures CSI from the kernel and does not modify it. Or, Is CSI of Atheros different form that of Intel? I don't think so... The final goal of extracting true phase from CSI of ath9k is to determine angle of arrival (AoA) of signal. Regards, Jeon. [1]: http://pdcc.ntu.edu.sg/wands/Atheros/ "Atheros CSI Extraction Tool" [2] K. Qian, C. Wu, Z. Yang, Y. Liu, and Z. Zhou, =E2=80=9CPADS: Passive de= tection of moving targets with dynamic speed using PHY layer information,=E2=80=9D = in 2014 20th IEEE International Conference on Parallel and Distributed Systems (ICPADS), 2014, pp. 1=E2=80=938. [3] M. Kotaru, K. Joshi, D. Bharadia, and S. Katti, =E2=80=9CSpotFi: Decime= ter Level Localization Using WiFi,=E2=80=9D SIGCOMM Comput. Commun. Rev., vol. = 45, no. 4, pp. 269=E2=80=93282, Aug. 2015. [4] http://dhalperi.github.io/linux-80211n-csitool/ "Linux 802.11n CSI Tool" --001a113ff17008949005352bd33e Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Dear ath9k developers,

I am currently working with = Atheros CSI Extraction Tool [1] to get a true phase of each subcarrier.
=
- Background

[2], [3] and many other papers claim that phase inf= ormation from extracted CSI contains two components: true phase and unwante= d phase offset due to subcarrier and time delay.
i.e., measured_phase = =3D true_phase + time_delay * subcarrier_index + phase_offset_due_to_txrx_m= ismatch
This equation can be visualized as below:

http://i.imgur.com/rk9Hh1M.png

(Plea= se note that this figure is based on CSI tool for Intel 5300 NIC.)

I= t contains unwanted linear phase offset and constant phase offset. Since th= e true phase is relatively small, it seems that phase is monotonically incr= easing or decreasing in macro view due to the unwanted phase offsets. We ca= nnot see a tiny true phase currently.

To remove phase offset d= ue to subcarrier, the mentioned papers are attempting to remove it with lin= ear fitting ax + b,
where a =3D slope of the figure, b =3D average of me= asured phase, and x =3D subcarrier index.

After removing unwanted ph= ase offset components, the true phase is estimated.
This estimated true = phase seems steady and consistent across a time duration shorter than < = 100 - 1000 ms:

http://i.i= mgur.com/AO89vYV.png

Note that Y-axis scale is reduece from [-50= , 10] to [5, -3]

- My question

I want to extract and manipula= te CSI phase WITH ATH9K NIC.

After extracting CSI from my ath9k NIC = (AR9580 @ 2.4 GHz) with Atheros CSI extraction tool,
I've tried vari= ous fitting methods to eliminate unwanted components and stacked results fr= om nearly 100 packets:

ht= tp://i.imgur.com/5r9eYwO.png

From the result, in short, removing= only constant offset across subcarrier seems to be effective. But I'm = not sure.
And sometimes, some phase measurement show large dispal= cement along y-axis even they are captured within very short duration.
<= br>Hence the question is,
Is ath9k reports CSI with those unwante= d linear phase offset removed?
If it is not, should I look into A= theros CSI tool? As I look into it, it just captures CSI from the kernel an= d does not modify it.
Or, Is CSI of Atheros different form that o= f Intel? I don't think so...

The final goal of= extracting true phase from CSI of ath9k is to determine angle of arrival (= AoA) of signal.

Regards,
Jeon.

[1]: http://pdcc.ntu.edu.sg/wands/Atheros/ "= ;Atheros CSI Extraction Tool"
[2] K. Qian, C. Wu, Z. Yang, Y. Liu, = and Z. Zhou, =E2=80=9CPADS: Passive detection of moving targets with dynami= c speed using PHY layer information,=E2=80=9D in 2014 20th IEEE Internation= al Conference on Parallel and Distributed Systems (ICPADS), 2014, pp. 1=E2= =80=938.
[3] M. Kotaru, K. Joshi, D. Bharadia, and S. Katti, =E2=80=9CSp= otFi: Decimeter Level Localization Using WiFi,=E2=80=9D SIGCOMM Comput. Com= mun. Rev., vol. 45, no. 4, pp. 269=E2=80=93282, Aug. 2015.
[4] http://dhalperi.github= .io/linux-80211n-csitool/ "Linux 802.11n CSI Tool"
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