ath10k: What will happens when radar is detected ?

ath10k: What will happens when radar is detected ?

[Cedric VONCKEN]

In 802.11ac standard, it is possible to dynamically reduce the channel
width used.
My question is:
	If I use a channel with 80 or 40 MHz width, what will happen if
I detect radar? 
		The ath10k card/driver reduces automatically the channel
width.

Cedric Voncken.

Re: ath10k: What will happens when radar is detected ?

[Michal Kazior]

On 23 March 2015 at 16:16, Cedric VONCKEN <cedric.voncken@acksys.fr> wrote:
> In 802.11ac standard, it is possible to dynamically reduce the channel
> width used.
> My question is:
>         If I use a channel with 80 or 40 MHz width, what will happen if
> I detect radar?
>                 The ath10k card/driver reduces automatically the channel
> width.

Currently entire chandef occupied will be marked as unavailable and AP
will stop/switch to a different non-overlapping chandef via CSA.

I guess it should be possible to implement what you suggest, i.e.
change only chandef width when radar is narrow and located at a
suitable part of the chandef. This would require hw to be capable of
detecting radar center freq and width accurately. I'm not sure if
QCA988X is capable of that although firmware interface seems to be
able to carry this kind of information already.

I wonder why would you want this behaviour in the first place?
Wouldn't this actually end up with having less bandwidth and lower
throughput (which is already penalized when radar detection is
active)?


Michał

RE: ath10k: What will happens when radar is detected ?

[voncken]

> -----Message d'origine-----
> De : Michal Kazior [mailto:michal.kazior@tieto.com]
> Envoyé : mardi 24 mars 2015 07:56
> À : Cedric VONCKEN
> Cc : linux-wireless
> Objet : Re: ath10k: What will happens when radar is detected ?
> 
> On 23 March 2015 at 16:16, Cedric VONCKEN <cedric.voncken@acksys.fr>
> wrote:
> > In 802.11ac standard, it is possible to dynamically reduce the channel
> > width used.
> > My question is:
> >         If I use a channel with 80 or 40 MHz width, what will happen
> > if I detect radar?
> >                 The ath10k card/driver reduces automatically the
> > channel width.
> 
> Currently entire chandef occupied will be marked as unavailable and AP
> will stop/switch to a different non-overlapping chandef via CSA.
Thanks for your answer.
> 
> I guess it should be possible to implement what you suggest, i.e.
> change only chandef width when radar is narrow and located at a suitable
> part of the chandef. This would require hw to be capable of detecting
> radar center freq and width accurately. I'm not sure if QCA988X is
> capable of that although firmware interface seems to be able to carry
> this kind of information already.
> 
> I wonder why would you want this behaviour in the first place?
> Wouldn't this actually end up with having less bandwidth and lower
> throughput (which is already penalized when radar detection is active)?
In an industrial environment we prefer to reduce the throughput but keep the link without gap. I think it can be a parameter in AP software for example.

Cédric