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From:   b.K.il.h.u+tigbuh@gmail.com
Date:   Tue, 8 Feb 2022 19:12:33 +0100
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Subject: Re: [wireless-regdb] wireless-regdb: Update regulatory rules for the
 US on 6 GHz band
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Sorry to chime in like this. I haven't even read the linked
documentation, but whatever the final solution will be, I would prefer
if we committed the lowest, safe power levels while we are actively
researching, deciding and implementing a final solution. We can always
raise limits later on.

On Mon, Dec 20, 2021 at 10:02 PM Seth Forshee <sforshee@kernel.org> wrote:
>
> On Sat, Dec 18, 2021 at 04:34:13PM +0900, Sungbo Eo wrote:
> > On 2021-12-18 06:55, sforshee@kernel.org wrote:
> > > On Mon, Dec 13, 2021 at 09:19:50AM +0000, Asura Liu (asuliu) wrote:
> > > >  From 3db25ea674232fea6a5efca292f6ed3fd8eba7a2 Mon Sep 17 00:00:00 =
2001
> > > > From: Asura Liu <asuliu@cisco.com>
> > > > Date: Mon, 13 Dec 2021 16:46:28 +0800
> > > > Subject: [PATCH] wireless-regdb: Update regulatory rules for the US=
 on 6 GHz
> > > > band
> > > > MIME-Version: 1.0
> > > > Content-Type: text/plain; charset=3DUTF-8
> > > > Content-Transfer-Encoding: 8bit
> > > >
> > > > According to FCC 20-51, FCC adopts rules to unlicensed use of the 6=
 GHz band:
> > > > "59. Third, the Commission limits the low-power indoor access point=
s to lower power levels than the standard-power access points that operate =
under the control of an AFC. Consistent with the Commission's approach for =
the existing U-NII bands, the Commission specifies both a maximum power spe=
ctral density and an absolute maximum transmit power, both in terms of EIRP=
. Specifically, the Commission allows a maximum radiated power spectral den=
sity of 5 dBm per 1 megahertz and an absolute maximum radiated channel powe=
r of 30 dBm for the maximum permitted 320-megahertz channel (or 27 dBm for =
a 160-megahertz channel). In addition, to ensure that client devices remain=
 in close proximity to the indoor access points, the Commission limits thei=
r PSD and maximum transmit power to 6 dB below the power permitted for the =
access points."
> > > > See https://www.federalregister.gov/documents/2020/05/26/2020-11236=
/unlicensed-use-of-the-6-ghz-band
> > > >
> > > > And 47 CFR =C2=A7 15.407 describe this as following:
> > > > (a) (5) For an indoor access point operating in the 5.925-7.125 GHz=
 band, the maximum power spectral density must not exceed 5 dBm e.i.r.p. in=
 any 1-megahertz band. In addition, the maximum e.i.r.p. over the frequency=
 band of operation must not exceed 30 dBm.
> > > > (a) (8) For client devices operating under the control of an indoor=
 access point in the 5.925-7.125 GHz bands, the maximum power spectral dens=
ity must not exceed =E2=88=921 dBm e.i.r.p. in any 1-megahertz band, and th=
e maximum e.i.r.p. over the frequency band of operation must not exceed 24 =
dBm.
> > >
> > > Thanks for the patch. A couple of quick notes about the patch
> > > description. It's preferred to wrap lines in the body at around 75
> > > characters, and it's required that you include a Signed-off-by tag
> > > indicating your agreement to the DCO for your contribution (see
> > > CONTRIBUTING).
> > >
> > > Additional comments below.
> > >
> > > > ---
> > > > db.txt | 6 ++++++
> > > > 1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/db.txt b/db.txt
> > > > index b898799..c6ef9b6 100644
> > > > --- a/db.txt
> > > > +++ b/db.txt
> > > > @@ -1606,6 +1606,12 @@ country US: DFS-FCC
> > > >   # https://www.federalregister.gov/documents/2021/05/03/2021-08802=
/use-of-the-5850-5925-ghz-band
> > > >   # max. 33 dBm AP @ 20MHz, 36 dBm AP @ 40Mhz+, 6 dB less for clien=
ts
> > > >   (5850 - 5895 @ 40), (27), NO-OUTDOOR, AUTO-BW, NO-IR
> > > > + # 6ghz band
> > > > + # https://www.federalregister.gov/documents/2020/05/26/2020-11236=
/unlicensed-use-of-the-6-ghz-band
> > > > + # https://docs.fcc.gov/public/attachments/FCC-20-51A1_Rcd.pdf
> > > > + # max. 30 dBm AP @ 320MHz, 27 dBm AP @ 160MHz, 6 dB less for clie=
nts
> > > > + (5925 - 7125 @ 320), (30), NO-OUTDOOR, AUTO-BW
> > > > + (5925 - 7125 @ 320), (24), NO-OUTDOOR, AUTO-BW, NO-IR
> > >
> > > The kernel doesn't currently support multiple rules with different fl=
ags
> > > for the same range. This is an issue that's come up several times, bu=
t
> > > so far nothing has been done about it.
> > >
> > > Even ingoring that, I don't think these rules accomplish the intended
> > > purpose. There's nothing that would require a client device to use th=
e
> > > NO-IR rule, so they could end up using the higher power limit and
> > > transmitting before detecting transmission from an AP.
> > >
> > > I also suspect that we should be able to express the AFC requirement =
in
> > > the database before permitting AP operation in this range.
> > >
> > > Currently I think the best we're able to do is to use the lowest comm=
on
> > > denominator, which is the 24 dBm rule with NO-IR.
> > >
> > > Thanks,
> > > Seth
> >
> > Hi, sorry for intruding.
> >
> > I thought max EIRP rule for larger bandwidth also applies to smaller
> > bandwidth, that means we would use 24 dBm tx power with 20 MHz channel =
as
> > well. But the regulation limits PSD to -1 dBm/MHz and it leads to 12 dB=
m for
> > 20 MHz. Shouldn't we use 12 dBm rule to fit the smallest bandwidth?
> >
> > I still don't understand exactly how the rules work, my apologies if I =
am
> > mistaken.
>
> Before I respond, let me be upfront about my limitations. I'm not an RF
> engineer. My day job no longer has anything to do with wireless and has
> not for a number of years now. I haven't had time to really keep up with
> recent developments either, so my impressions are based on some light
> research and what I remember of information I rarely use nowadays.
>
> After doing a little bit of reading, I suspect that you are probably
> right (in principle at least, I didn't check the math). It seems there's
> been a movement towards specifying PSD so that larger bandwidths can
> effectively have a higher max EIRP than lower bandwitdths to overcome
> diminishing SNR with increasing bandwidth.
>
> That leaves us in the unfortunate position of needing to specify an EIRP
> suitable for a bandwidth of 20 MHz when larger bandwidths could be using
> a higher power limit. It seems like the Linux regulatory framework needs
> to evolve to support PSD limits. I don't currently have the time or the
> inclination to do this work though, and until someone does we're stuck
> with the status quo.
>
> Thanks,
> Seth
>
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