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From: Petko Bordjukov <bordjukov@gmail.com>
Date: Fri, 26 Jan 2024 12:46:23 +0200
Message-ID: <CAAgmp6vdK-bMJCnXUqhPPADRcd3sJXeFvuSOt5_7HCSV2dVKEQ@mail.gmail.com>
Subject: Re: WiF Transmit Power Control (TPC) Regulatory Requirements?
To: b.K.il.h.u+tigbuh@gmail.com
Cc: wireless-regdb <wireless-regdb@lists.infradead.org>, 
	linux-wireless <linux-wireless@vger.kernel.org>, thomas.huehn@hs-nordhausen.de
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Hi,

The only project I've heard of that implements such functionality is
https://github.com/thuehn/Minstrel-Blues.

On Thu, Jan 4, 2024 at 12:02=E2=80=AFPM <b.K.il.h.u+tigbuh@gmail.com> wrote=
:
>
> Ideally, TPC should be a fully automatic mechanism that reduces
> transmit power between the two points to as low of a level as possible
> while delivering the same quality of service. The purpose is to reduce
> the excess headroom in each link. I.e., if you could still link with
> 65Mb/s towards a given direction using 14dBmW, you should not transmit
> with 20dBmW.
>
> Some only set the AP TX power globally (i.e., same towards all of its
> connected clients at the moment) to tackle the hidden/exposed node
> problem, but again must do this adaptively and change this constantly
> without human intervention. There exist multiple advanced algorithms
> for this, some proprietary tuned for corporate deployment.
>
> Actually, if we accepted automatically retuning tx power with iw based
> on actual link stats of momentarily connected clients every 60s with
> cron, this could be added to OpenWrt pretty easily.
>
> > Class A devices control their transmit power within =C2=B13 dB and clas=
s B devices control their power within =C2=B19 dB.
>
> - https://www.litepoint.com/blog/wi-fi-6-ofdma/
> - https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3=
/b_RRM_White_Paper/tpc.html
>
> On Thu, Jan 4, 2024 at 10:42=E2=80=AFAM Johannes Berg <johannes@sipsoluti=
ons.net> wrote:
> >
> > On Thu, 2024-01-04 at 10:07 +0100, b.K.il.h.u+tigbuh@gmail.com wrote:
> > > You can find a wording in most such regulations that if TPC is not
> > > supported, the maximal TX power must be reduced by 3 dBmW. Hence in
> > > all such cases, the entries in db.txt contain 3 less than the maximum=
.
> > >
> > > If, on the other hand, you know of a country that specifies that
> > > devices lacking TPC may not use the band at all, all such band entrie=
s
> > > must be omitted (commented out along with a URL).
> >
> > Yeah, that's how we (currently) handle things.
> >
> > I'm not even sure what the requirements would be for "TPC" to be
> > implemented, tbh.
> >
> > > > As far as I know the kernel doesn't have facilities to support TPC =
or
> > > > transmit power control,
> >
> > Right. I have, however, heard the interpretation that the fact that we
> > have - even if nobody uses it - the "iw set txpower" command means that
> > we *do* have TPC ... Not really sure what to make of that though.
> >
> > > > nor does the wireless-regdb database.
> >
> > Correct. With the new regdb format we could add something that would
> > enable these ranges in the kernel only with some additional
> > requirements, but
> >   (a) we don't implement that now, and
> >   (b) I don't know what the requirements would actually be, e.g. would
> >       it be enough that the driver promises it implements "TPC" in some
> >       way? Or even the manual setting?
> >
> > > > And so
> > > > in the database we would either omit rules that require TPC, or inc=
lude
> > > > alternative rules (as specified by local regulations) not requiring=
 TPC.
> > > > Am I right?
> >
> > Right.
> >
> > johannes
>