From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-x229.google.com (mail-qt0-x229.google.com [IPv6:2607:f8b0:400d:c0d::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 0EAC33B29E; Mon, 27 Aug 2018 03:24:22 -0400 (EDT) Received: by mail-qt0-x229.google.com with SMTP id r37-v6so16934137qtc.0; Mon, 27 Aug 2018 00:24:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=akZsPwfhVn44krIBSc/6mE9mnDmEPp14JYjdifRPTyw=; b=N5RamOg0dlpm0Dj0faQBJ2654vQHIlhyr/MheYCmrB2KAbeo1XoeFIPsI+gXpGEOLa ZYSbBnB4I/YoGgqgMgUjX4vWOdsW6wBhOJT9yy3ZMU/KMXtV5gDjXkM/hpozo4iGSTEY FuVKuu85hLy6ujJ5uiqDqQ2EFzDXzNi5Ahczh4v/qT0Ee2iSUC/dnmvUU5OlYqTTP8Fs hqapqMzrFOB54/1aRYcDQBbWqlRN+HhM908z9mhsjc6rbHw3RxoMpBKvmfo2O4NpYJYU zhusyRX5pLFcn32HUBk8LDm1q4B+oAh+vRPcUEmQp5W9WjTtk+vhKWSjCv+fiOoaJ9YL Mq+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=akZsPwfhVn44krIBSc/6mE9mnDmEPp14JYjdifRPTyw=; b=qrrxiN/qe17JufOB0NPd8AvZjM2P+KroAERn74qPdyyjswVEYuL4bzNjZDgfsnH4lV 4/gK/2Qe0phxOTBwd62Pw9T2UXWz1/VI+b2v2RFlNxxadsRSwqr0T7H/TuqMTqke++pw ui6yLEW3Q8oCBCi254l9WoEE84UbaWoHvRp93TXrR78j0vY3AjFMPI0PHrg338srUgOa hotmDJWKoGAHXgcGJO3h1hpqxK2fhN9reAyj82doogrsSz7o1d7touQnDKhpYswLtBzb BydlR1ipPrhbI/Tw1YCzN1BJX6t5I6isBytjXg0/6KENc8Jf2XuIMFA0LxuT672mWbFe q+HQ== X-Gm-Message-State: APzg51BzMYGzy+iPoLGnYWcDmVe6qe+OEyQXMdhLfiRXxJ+fPLsQbTeJ 5GobpHLNap5xYAebPyTvf0vxVanvVkvXsY8aeVw= X-Google-Smtp-Source: ANB0Vdb9bNSnJEEM3rSRxkipQ7zI6ELnxizfIdoVpm0Xd1ykvKXNkxLAzW3FiqrPDLo6l+LnBRE076EbeoPwmNOVobA= X-Received: by 2002:ac8:31f5:: with SMTP id i50-v6mr12682163qte.323.1535354661587; Mon, 27 Aug 2018 00:24:21 -0700 (PDT) MIME-Version: 1.0 References: <1535286372.35121837@apps.rackspace.com> <2282D31E-CBEF-4B42-A6A6-4D6394EE0DF7@gmail.com> In-Reply-To: <2282D31E-CBEF-4B42-A6A6-4D6394EE0DF7@gmail.com> From: Luca Muscariello Date: Mon, 27 Aug 2018 09:24:10 +0200 Message-ID: To: Jonathan Morton Cc: bob.mcmahon@broadcom.com, bloat-announce@lists.bufferbloat.net, make-wifi-fast@lists.bufferbloat.net, cerowrt-devel@lists.bufferbloat.net, dpreed@deepplum.com, bloat Content-Type: multipart/alternative; boundary="0000000000003551410574659d2a" Subject: Re: [Bloat] [Make-wifi-fast] [Cerowrt-devel] closing up my make-wifi-fast lab X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Aug 2018 07:24:22 -0000 --0000000000003551410574659d2a Content-Type: text/plain; charset="UTF-8" Jonathan, Not that giant handwaving though. IEEE 802.11ax makes use of "almost TDM" RTS/CTS and scheduling. The almost is necessary as it operates in 2.4/5Ghz bands. Similar to what you describe, and is coming very soon in shipping products. RTS/CTS is still a LBT to create a window where TDM can be done. I don't yet see how a non private spectrum can be shared w/o LBT. On the other hand, medium sharing is one thing, the other thing is capacity. There is no way to efficiently share a medium if this is used close to its theoretical capacity. Capacity as #of stations per band including #SSID per band. Today scaling can be achieved with careful radio planning for spatial diversity or dynamic bean forming. When you approach capacity with WiFi you only see beacon traffic and almost zero throughput. Cannot forget Mobile World Congress where you can measure several thousands of SSIDs on 2.4 and several hundreds of SSID in 5GHz. But even LTE was very close to capacity. Dave, Having air time fairness in open source is a significant achievement. I don't see a failure. Luca On Mon, Aug 27, 2018 at 8:26 AM Jonathan Morton wrote: > > On 27 Aug, 2018, at 9:00 am, Bob McMahon > wrote: > > > > Curious to how LBT can be solved at the PHY level and if the potential > solution sets preserve the end to end principle. > > The usual alternatives include TDM, usually coordinated by a master device > (eg. the AP); full-duplex operation via diplexers and/or orthogonal coding; > and simply firing off a packet and retrying with exponential backoff if an > acknowledgement is not heard. > > TDM and diplexing are already used by both DOCSIS and LTE. They are > proven technology. However, in DOCSIS the diplexing is greatly simplified > by the use of a copper channel rather than airwaves, and in LTE the > diplexer is fitted only at the tower, not in each client - so the tower can > transmit and receive simultaneously, but an individual client cannot, but > this is still useful because there are many clients per tower. Effective > diplexers for wireless are expensive. > > Orthogonal coding is already used by GPS and, in a rather esoteric form, > by MIMO-grade wifi. IMHO it works rather better in GPS than in wifi. In > GPS, it allows all of the satellites in the constellation to transmit on > the standard frequency simultaneously, while still being individually > distinguishable. The data rate is very low, however, since each > satellite's signal inherently has a negative SNR (because there's a dozen > others shouting over it) - that's why it takes a full minute for a receiver > to get a fix from cold, because it simply takes that long to download the > ephemeris from the first satellite whose signal is found. > > A future version of wifi could reasonably use TDM, I think, but not > diplexing. The way this would work is that the AP assigns each station > (including itself) a series of time windows in which to transmit as much as > they like, and broadcasts this schedule along with its beacon. Also > scheduled would be windows in which the AP listens for new stations, > including possibly other nearby APs with which it may mutually coordinate > time. A mesh network could thus be constructed entirely out of mutually > coordinating APs if necessary. > > The above paragraph is obviously a giant handwave... > > - Jonathan Morton > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat > --0000000000003551410574659d2a Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Jonathan,

Not that giant han= dwaving though.
IEEE 802.11ax makes use of "almost TDM" RTS/= CTS and scheduling. The almost is necessary as it operates in 2.4/5Ghz band= s.
Similar to what you describe, and is coming very soon in shipping pr= oducts.=C2=A0

RTS/CTS is still a LBT to create a w= indow where TDM can be done.=C2=A0
I don't yet see how a non = private spectrum can be shared=C2=A0 w/o LBT.

On t= he other hand, medium sharing is one thing, the other thing is capacity.=C2= =A0
There is no way to efficiently share a medium if this is used= close to its theoretical capacity.=C2=A0

Capacity= as #of stations per band including #SSID per band. Today scaling can be ac= hieved
with careful radio planning for spatial diversity or dynam= ic bean forming.

When you approach capacity with W= iFi you only see beacon traffic and almost zero throughput.=C2=A0
Cannot forget Mobile World Congress where you can measure several thousand= s of SSIDs on 2.4=C2=A0
and several hundreds of SSID in 5GHz. But= even LTE was very close to capacity.
=C2=A0
Dave,
Having air time fairness in open source is a significant achievement.= I don't see a failure.

Luca

On Mon, Aug 27, 2018 at 8:26 A= M Jonathan Morton <chromatix99@= gmail.com> wrote:
> On = 27 Aug, 2018, at 9:00 am, Bob McMahon <bob.mcmahon@broadcom.com> wrote:
>
> Curious to how LBT can be solved at the PHY level and if the potential= solution sets preserve the end to end principle.

The usual alternatives include TDM, usually coordinated by a master device = (eg. the AP); full-duplex operation via diplexers and/or orthogonal coding;= and simply firing off a packet and retrying with exponential backoff if an= acknowledgement is not heard.

TDM and diplexing are already used by both DOCSIS and LTE.=C2=A0 They are p= roven technology.=C2=A0 However, in DOCSIS the diplexing is greatly simplif= ied by the use of a copper channel rather than airwaves, and in LTE the dip= lexer is fitted only at the tower, not in each client - so the tower can tr= ansmit and receive simultaneously, but an individual client cannot, but thi= s is still useful because there are many clients per tower.=C2=A0 Effective= diplexers for wireless are expensive.

Orthogonal coding is already used by GPS and, in a rather esoteric form, by= MIMO-grade wifi.=C2=A0 IMHO it works rather better in GPS than in wifi.=C2= =A0 In GPS, it allows all of the satellites in the constellation to transmi= t on the standard frequency simultaneously, while still being individually = distinguishable.=C2=A0 The data rate is very low, however, since each satel= lite's signal inherently has a negative SNR (because there's a doze= n others shouting over it) - that's why it takes a full minute for a re= ceiver to get a fix from cold, because it simply takes that long to downloa= d the ephemeris from the first satellite whose signal is found.

A future version of wifi could reasonably use TDM, I think, but not diplexi= ng.=C2=A0 The way this would work is that the AP assigns each station (incl= uding itself) a series of time windows in which to transmit as much as they= like, and broadcasts this schedule along with its beacon.=C2=A0 Also sched= uled would be windows in which the AP listens for new stations, including p= ossibly other nearby APs with which it may mutually coordinate time.=C2=A0 = A mesh network could thus be constructed entirely out of mutually coordinat= ing APs if necessary.

The above paragraph is obviously a giant handwave...

=C2=A0- Jonathan Morton

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