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

Thu Nov 15 10:36:43 EST 2018

> Meant to comment on this earlier,  the AREDN amateur radio emergency mesh
group  ( https://www.arednmesh.org ) seems to be using 5mhz channels as an
option, for a few of the previously mentioned reasons.

Interestingly, their code is based out of OpenWRT, and they just recently
caught everything up to the 18.06.1 release, from the pre LEDE era.  What
it is, is a long distance backhaul/local area mesh comm system using
commercial equipment on amateur bands, for emergency use. Video, text,
audio, net access, etc.  They have pretty extensive networks in several
areas.

So, there's another user of the narrower channels.  I'd guess anyone
setting up homegrown mini ISP like systems similar to this would like the
option, to trade peak bandwidth for extended s/n and longer range.

--------- Forwarded message ----------
> From: Dave Taht <dave.taht at gmail.com>
> To: bkil.hu+Aq at gmail.com, Make-Wifi-fast <
> make-wifi-fast at lists.bufferbloat.net>, Ben Greear <greearb at candelatech.com
> >
> Cc:
> Bcc:
> Date: Mon, 8 Oct 2018 13:32:33 -0700
> Subject: Re: [Make-wifi-fast] [Bloat] Is 5/10MHz wifi bandwidth legal in
> 2.4GHz (half/quarter-clocking)?
> 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
> > _______________________________________________
> > Bloat mailing list
> > 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
>
>
>
>
> ---------- Forwarded message ----------
> From: bkil <bkil.hu+Aq at gmail.com>
> To: ryan at mounce.com.au
> Cc: bloat <bloat at lists.bufferbloat.net>, Make-Wifi-fast <
> make-wifi-fast at lists.bufferbloat.net>
> Bcc:
> Date: Tue, 9 Oct 2018 07:44:40 +0200
> Subject: Re: [Make-wifi-fast] [Bloat] Is 5/10MHz wifi bandwidth legal in
> 2.4GHz (half/quarter-clocking)?
> Yes, that was my conclusion as well. There exist spectral masks of
> maximal allowed side lobes, but if you are transmitting signals
> narrower than that, the side lobes will be much below the limit.
>
> Spectral density in Hungary and some other countries allows for
> 10mW/MHz, meaning twice the power density for narrow channels.
>
> There can exist a possibility for starvation if two narrow channels
> use the two sides of a wider channel in turn, similar to HT40, so a
> neighborly mechanism would be nice.
>
> On Tue, Oct 9, 2018 at 5:53 AM Ryan Mounce <ryan at mounce.com.au> wrote:
> >
> > I'm not aware of anywhere this would be illegal. Worst case you will
> > need to reduce power by 3/6dB (10/5MHz) if there is a power spectral
> > density limit in a given jurisdiction and max EIRP @ 20MHz is already
> > at that limit.
> >
> > On Tue, 9 Oct 2018 at 06:48, 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
> > > _______________________________________________
> > > Bloat mailing list
> > > Bloat at lists.bufferbloat.net
> > > https://lists.bufferbloat.net/listinfo/bloat
>
>
>
>
> ---------- Forwarded message ----------
> From: bkil <bkil.hu+Aq at gmail.com>
> To: Dave Taht <dave.taht at gmail.com>, bloat <bloat at lists.bufferbloat.net>
> Cc: Make-Wifi-fast <make-wifi-fast at lists.bufferbloat.net>,
> greearb at candelatech.com
> Bcc:
> Date: Tue, 9 Oct 2018 07:52:28 +0200
> Subject: Re: [Make-wifi-fast] [Bloat] Is 5/10MHz wifi bandwidth legal in
> 2.4GHz (half/quarter-clocking)?
> 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.
>
>
>
> _______________________________________________
> Make-wifi-fast mailing list
> Make-wifi-fast at lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/make-wifi-fast
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