[Bloat] Is 5/10MHz wifi bandwidth legal in 2.4GHz (half/quarter-clocking)?

[bkil]

I wouldn't be surprised if we could patch this mode to another common
chipset other than Atheros.

I understand that this is not a standard mode in 2.4GHz if reading the
standard to the letter, but it is close enough. If it is legal to use
it, as lots of devices support it, it would still be a great choice
for certain point to (mult-)point links or mesh/IoT deployments and we
should "advertise" this capability better.

We could get 16 orthogonal channels instead of 4 (or 13 overlapping) -
so we do get more channels in the end.

Also we have lots of underutilized spectrum in 5GHz, we would need to
update regdb in most countries and handle additional channel numbers
to use this.
On Mon, Oct 8, 2018 at 10:32 PM Dave Taht <dave.taht at gmail.com> wrote:
>
> make-wifi-fast is better here.
>
> anyway there was a long debate about making the public access channels
> available to folk that needed it in the ath10k patchset, I think in
> the end ben greer decided to leave it out lacking getting anyone at
> the FCC to pay attention.
>
> the second question, regarding 5Mhz channels in general - I had tried
> that a lot (it has worked multiple times in ath9k's lifecycle) and I
> *liked it*, but as it was non standard never got around to depending
> on it existing on anything.
>
> We definitely need more channels, not less
>
> On Mon, Oct 8, 2018 at 1:18 PM bkil <bkil.hu+Aq at gmail.com> wrote:
> >
> > If this is not the right forum to discuss, could you please point me
> > in the right direction?
> >
> > After all, channel spacing is indeed 5MHz here. Although using a new
> > raster instead of the 20MHz channel center frequencies would allow
> > full utilization of the band (16 or 8 channels respectively), using
> > the standard set of 11 (13) channels is better than nothing.
> >
> > Is it a good idea to use HT instead of g for such links?
> >
> > =
> > Some background and links for those who do not know this mode:
> >
> > "the 2007 version of the IEEE 802.11 standard [1] specifies 5 and 10
> > MHz wide channels for use in the 4.9 GHz public safety bands"
> >
> > Although according to my reading of section 17.1, it applies to the
> > 5GHz bands as well:
> >
> > >> 17. Orthogonal frequency division multiplexing (OFDM) PHY specification
> > for the 5 GHz band
> > [...]
> > The OFDM system also provides a “half-clocked” operation using 10 MHz
> > channel spacings with data
> > communications capabilities of 3, 4.5, 6, 9, 12, 18, 24, and 27 Mb/s.
> > The support of transmitting and
> > receiving at data rates of 3, 6, and 12 Mb/s is mandatory when using
> > 10 MHz channel spacing. The half-
> > clocked operation doubles symbol times and clear channel assessment
> > (CCA) times when using 10 MHz
> > channel spacing. The regulatory requirements and information regarding
> > use of this OFDM system in
> > 4.9 GHz and 5 GHz bands is in Annex I and Annex J.<<
> >
> > They probably did not highlight 2.4GHz usage because of mixed-mode
> > (non-OFDM) crowding, although nowadays we could actually move this
> > band to OFDM-only as well.
> >
> > It is unfortunate that this allowance has disappeared in newer
> > versions of the standard. Was that intentional?
> >
> > Reasons why downclocking is advantageous (up to +9dB link budget):
> >
> > * longer GI = better protection against multipath fading;
> > * higher power density allowed (2x here) = better SNR;
> > * less chance for (adjacent-channel) interference;
> > * reduced TX & RX power consumption for idling and low load.
> >
> > I know that 802.11ah/af are here, but there exist literally millions
> > of devices potentially supporting this old and trusty mode, software
> > permit.
> >
> > Many Atheros chipsets support it, both old and new. OpenWrt has
> > debugfs patches applied to enable this, while Linux has some other
> > patches as well, although it is not user visible.
> >
> > If this is a legal and preferred mode, it would be nice if we could
> > unify access.
> >
> > https://openwrt.org/docs/guide-user/network/wifi/basic?s[]=chanbw
> > http://ccr.sigcomm.org/online/files/p135-chandra.pdf
> > https://kabru.eecs.umich.edu/papers/publications/2011/xyzhang_kgshin_mobicom11.pdf
> > https://www.etsi.org/deliver/etsi_en/300300_300399/300328/01.08.01_60/en_300328v010801p.pdf
> > https://www.cwnp.com/forums/posts?postNum=305220
> > https://forum.archive.openwrt.org/viewtopic.php?id=38590
> > https://forum.openwrt.org/t/5-mhz-bandwith-option/3615
> > _______________________________________________
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> > Bloat at lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
>
>
>
> --
>
> Dave Täht
> CTO, TekLibre, LLC
> http://www.teklibre.com
> Tel: 1-831-205-9740