From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp73.iad3a.emailsrvr.com (smtp73.iad3a.emailsrvr.com [173.203.187.73]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id CDBD221F377 for ; Thu, 9 Oct 2014 07:25:22 -0700 (PDT) Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp18.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 39FAE280443; Thu, 9 Oct 2014 10:25:21 -0400 (EDT) X-Virus-Scanned: OK Received: from app52.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by smtp18.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 0F7C02805B5; Thu, 9 Oct 2014 10:25:21 -0400 (EDT) X-Sender-Id: dpreed@reed.com Received: from app52.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by 0.0.0.0:25 (trex/5.2.13); Thu, 09 Oct 2014 14:25:21 GMT Received: from reed.com (localhost.localdomain [127.0.0.1]) by app52.wa-webapps.iad3a (Postfix) with ESMTP id F231A38005D; Thu, 9 Oct 2014 10:25:20 -0400 (EDT) Received: by apps.rackspace.com (Authenticated sender: dpreed@reed.com, from: dpreed@reed.com) with HTTP; Thu, 9 Oct 2014 10:25:20 -0400 (EDT) Date: Thu, 9 Oct 2014 10:25:20 -0400 (EDT) From: dpreed@reed.com To: "Dave Taht" MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_20141009102520000000_85243" Importance: Normal X-Priority: 3 (Normal) X-Type: html In-Reply-To: References: X-Auth-ID: dpreed@reed.com Message-ID: <1412864720.98961528@apps.rackspace.com> X-Mailer: webmail7.0 Cc: "cerowrt-devel@lists.bufferbloat.net" Subject: Re: [Cerowrt-devel] wifi over narrow channels X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Oct 2014 14:25:52 -0000 ------=_20141009102520000000_85243 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =0AWideband is far better for scaling than narrowband, though. This may se= em counterintuitive, but narrowband systems are extremely inefficient. The= y appeal to 0/1 thinking intuitively, but in actual fact the wider the band= width the more sharing and the more scaling is possible (and not be "balkan= ization" or "exclusive channel negotiation").=0A =0ATwo Internets are far w= orse than a single Internet that combines both. That's because you have mo= re degrees of freedom in a single network than you can in two distinct netw= orks, by a combinatorial factor.=0A =0AThe analogy holds that one wide band= is far better than two disjoint bands in terms of scaling and adaptation. = The situation only gets better because of the physics of "multipath", which= creates more problems the more narrowband the signal, and when the signal = is a single frequency, multipath is disastrous.=0A =0AThe same is true if y= ou try to divide space into disjoint "channels" (as cellular tries to).=0A = =0ASo in the near term, narrowband wifi might be a short-term benefit, but = long-term it is 180 degress away from where you want to go.=0A =0A(the list= en-before-talk protocol in WiFi is pragmatic because it is built into hardw= are today, but terrible for wideband signals, because you can't shorten the= 4 usec. pre-transmit delay, and probably need to lengthen it, since 4 usec= . is about 1.25 km or 0.8 miles, and holds 40 bits at 10 Mb/s, or 4000 bit= s at 1 Gb/sec).=0A =0AEither for distance or for rate, the "Ethernet MAC+PH= Y" was designed for short "coax" or "hub" domains. Its not good for digital= wireless Internet, except for one thing: it is based on distributed contro= l that does not require any advance planning.=0A =0AIf you want to improve = open wireless, you have to a) go wide, b) maintain distributed control, c) = get rid of listen-before-talk to replace it with a mixture of co-channel de= coding and propagation negotiation. Then you can beat cellular trivially.= =0A =0AI wish I could attract investment away from the "short term" WiFi th= inking, but in the last 15 years, I've failed. Meanwhile WiFi also attract= s those people who want to add bufferbloat into the routers because they do= n't understand congestion control.=0A =0ASad.=0A=0A=0AOn Wednesday, October= 8, 2014 6:14pm, "Dave Taht" said:=0A=0A=0A=0A> https= ://www.usenix.org/system/files/conference/nsdi12/nsdi12-final142.pdf=0A> = =0A> I've had 5mhz channels working in the ath9k at various points in=0A> c= erowrt's lifetime. (using it for meshy stuff) After digesting most of=0A> t= he 802.11ac standard I do find myself wishing they'd gone towards=0A> narro= wer channels rather than wider.=0A> =0A> The netgear x4 defaults to a 160mh= z wide channel. :sigh:=0A> =0A> The above paper has some nifty ideas in it.= =0A> =0A> --=0A> Dave T=C3=A4ht=0A> =0A> https://www.bufferbloat.net/projec= ts/make-wifi-fast=0A> _______________________________________________=0A> C= erowrt-devel mailing list=0A> Cerowrt-devel@lists.bufferbloat.net=0A> https= ://lists.bufferbloat.net/listinfo/cerowrt-devel=0A> ------=_20141009102520000000_85243 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Wideband is far better for= scaling than narrowband, though.  This may seem counterintuitive, but= narrowband systems are extremely inefficient.  They appeal to 0/1 thi= nking intuitively, but in actual fact the wider the bandwidth the more shar= ing and the more scaling is possible (and not be "balkanization" or "exclus= ive channel negotiation").

=0A

 

=0A

Two Internets are far worse than a single Internet that combines both.=  That's because you have more degrees of freedom in a single network = than you can in two distinct networks, by a combinatorial factor.

=0A

 

=0A

The analogy holds that one wide= band is far better than two disjoint bands in terms of scaling and adaptat= ion. The situation only gets better because of the physics of "multipath", = which creates more problems the more narrowband the signal, and when the si= gnal is a single frequency, multipath is disastrous.

=0A

 

=0A

The same is true if you try to divide space = into disjoint "channels" (as cellular tries to).

=0A

&nb= sp;

=0A

So in the near term, narrowband wifi might be a = short-term benefit, but long-term it is 180 degress away from where you wan= t to go.

=0A

 

=0A

(the listen-b= efore-talk protocol in WiFi is pragmatic because it is built into hardware = today, but terrible for wideband signals, because you can't shorten the 4 u= sec. pre-transmit delay, and probably need to lengthen it, since 4 usec. is= about 1.25 km or 0.8 miles, and  holds 40 bits at 10 Mb/s, or 4000 bi= ts at 1 Gb/sec).

=0A

 

=0A

Eithe= r for distance or for rate, the "Ethernet MAC+PHY" was designed for short "= coax" or "hub" domains. Its not good for digital wireless Internet, except = for one thing: it is based on distributed control that does not require any= advance planning.

=0A

 

=0A

If = you want to improve open wireless, you have to a) go wide, b) maintain dist= ributed control, c) get rid of listen-before-talk to replace it with a mixt= ure of co-channel decoding and propagation negotiation.  Then you can = beat cellular trivially.

=0A

 

=0A

I wish I could attract investment away from the "short term" WiFi thinki= ng, but in the last 15 years, I've failed.  Meanwhile WiFi also attrac= ts those people who want to add bufferbloat into the routers because they d= on't understand congestion control.

=0A

 

=0A

Sad.

=0A=0A



On Wednesday, October 8, 2014= 6:14pm, "Dave Taht" <dave.taht@gmail.com> said:

=0A=0A

> https://www.usenix.= org/system/files/conference/nsdi12/nsdi12-final142.pdf
>
>= I've had 5mhz channels working in the ath9k at various points in
>= cerowrt's lifetime. (using it for meshy stuff) After digesting most of
> the 802.11ac standard I do find myself wishing they'd gone towards> narrower channels rather than wider.
>
> The netg= ear x4 defaults to a 160mhz wide channel. :sigh:
>
> The a= bove paper has some nifty ideas in it.
>
> --
> Da= ve T=C3=A4ht
>
> https://www.bufferbloat.net/projects/make= -wifi-fast
> _______________________________________________
&= gt; Cerowrt-devel mailing list
> Cerowrt-devel@lists.bufferbloat.ne= t
> https://lists.bufferbloat.net/listinfo/cerowrt-devel
> =

=0A ------=_20141009102520000000_85243--