From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp113.iad3a.emailsrvr.com (smtp113.iad3a.emailsrvr.com [173.203.187.113]) (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 C82FA21FA07 for ; Tue, 4 Aug 2015 09:55:22 -0700 (PDT) Received: from smtp23.relay.iad3a.emailsrvr.com (localhost.localdomain [127.0.0.1]) by smtp23.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 02A4F280556; Tue, 4 Aug 2015 12:55:20 -0400 (EDT) Received: from app5.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by smtp23.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id DE5A82802D3; Tue, 4 Aug 2015 12:55:20 -0400 (EDT) X-Sender-Id: dpreed@reed.com Received: from app5.wa-webapps.iad3a (relay-webapps.rsapps.net [172.27.255.140]) by 0.0.0.0:25 (trex/5.4.2); Tue, 04 Aug 2015 16:55:20 GMT Received: from reed.com (localhost.localdomain [127.0.0.1]) by app5.wa-webapps.iad3a (Postfix) with ESMTP id CAA70180072; Tue, 4 Aug 2015 12:55:20 -0400 (EDT) Received: by apps.rackspace.com (Authenticated sender: dpreed@reed.com, from: dpreed@reed.com) with HTTP; Tue, 4 Aug 2015 12:55:20 -0400 (EDT) Date: Tue, 4 Aug 2015 12:55:20 -0400 (EDT) From: dpreed@reed.com To: "David Lang" MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_20150804125520000000_47182" Importance: Normal X-Priority: 3 (Normal) X-Type: html In-Reply-To: References: <356F5FEE-9FBD-4FF9-AC17-86A642D918A4@gmail.com> <5CC1DC90-DFAF-4A4D-8204-16CD4E20D6E3@gmx.de> <4D24A497-5784-493D-B409-F704804326A7@gmx.de> <1438361254.45977158@apps.rackspace.com> <1438616670.710822730@apps.rackspace.com> <1438645067.22797794@apps.rackspace.com> X-Auth-ID: dpreed@reed.com Message-ID: <1438707320.825823577@apps.rackspace.com> X-Mailer: webmail/11.5.5-RC Cc: Jonathan Morton , cerowrt-devel@lists.bufferbloat.net, make-wifi-fast@lists.bufferbloat.net Subject: Re: [Cerowrt-devel] [Make-wifi-fast] [tsvwg] Comments on draft-szigeti-tsvwg-ieee-802-11e 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: Tue, 04 Aug 2015 16:55:51 -0000 ------=_20150804125520000000_47182 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =0AOn Monday, August 3, 2015 8:13pm, "David Lang" said:=0A>= =0A=0A> That requires central coordination of the stations. Something we d= on't have in=0A> wifi. Wifi lives and dies with 'listen for a gap, try tran= smitting, and if you=0A> collide, backoff a random period'=0A=0A=0ACentral = coordination is not the only form of coordination... there are perfectly fi= ne decentralized coordination schemes that do better than LBT. Depends on y= our definition of 802.11, but I did point out that the MAC layer could be a= lot better, and internode coordination can be both decentralized and far m= ore power efficient, in principle. It's important to realize that the prepa= ration of an OFDM modulated waveform can be pipelined, so that a transmitte= r can have the physical waveform "built" (via DFT, etc.) while waiting for = its time to go. And the "collision resolution" can and should be an arbitr= ation process that starts before the current packet in the air is finished.= =0A=0AWhat prevents this is unnecessary "legacy compatibility" - making hig= h speed modulated packets suffer because there are still stupid 2 Mb/sec. 8= 02.11b devices on the 2.4 GHz band. There are ways to coexist with legacy = systems that are better than transmitting the prefix on the front of every = packet (you can transmit a fake 802.11b prefix that will lock out the 2.4 G= Hz competitors for a period of time when many "turbo" stations occupy the a= ir using better cooperating physical layer methods, as a conceptually trivi= al example).=0A ------=_20150804125520000000_47182 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

On Monday, August = 3, 2015 8:13pm, "David Lang" <david@lang.hm> said:

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> 

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> That requires central coordination of = the stations. Something we don't have in
> wifi. Wifi lives and die= s with 'listen for a gap, try transmitting, and if you
> collide, b= ackoff a random period'

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Cent= ral coordination is not the only form of coordination... there are perfectl= y fine decentralized coordination schemes that do better than LBT. Depends = on your definition of 802.11, but I did point out that the MAC layer could = be a lot better, and internode coordination can be both decentralized and f= ar more power efficient, in principle. It's important to realize that the p= reparation of an OFDM modulated waveform can be pipelined, so that a transm= itter can have the physical waveform "built" (via DFT, etc.) while waiting = for its time to go.  And the "collision resolution" can and should be = an arbitration process that starts before the current packet in the air is = finished.

What prevents this is unnecessary "legacy compatibilit= y" - making high speed modulated packets suffer because there are stil= l stupid 2 Mb/sec. 802.11b devices on the 2.4 GHz band.  There are way= s to coexist with legacy systems that are better than transmitting the pref= ix on the front of every packet (you can transmit a fake 802.11b prefix tha= t will lock out the 2.4 GHz competitors for a period of time when many "tur= bo" stations occupy the air using better cooperating physical layer methods= , as a conceptually trivial example).

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&n= bsp;

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