From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-x52d.google.com (mail-ed1-x52d.google.com [IPv6:2a00:1450:4864:20::52d]) (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 047473CB36 for ; Mon, 27 Aug 2018 03:39:21 -0400 (EDT) Received: by mail-ed1-x52d.google.com with SMTP id e19-v6so9758044edq.7 for ; Mon, 27 Aug 2018 00:39:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=KQKQNln9fj086EfqrNec2JNDP+oFOdwq1zjl2Y/zJaQ=; b=E3H6hfNNzC184w57iZrH5QKrMe7/bOJvvqM7z3FAnzpFO0wwCdZyS5HarIkS/rNgEK AVOeLdNqrM3RL8oOLNIqtJuVjIHitmc9NjqzNlfkPCvy/6tpYDH6S1AOYBlmIRWM0H+h KfRKZGPCiYYVgHS6X+du73baO2d2qosX3pHVA= 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=KQKQNln9fj086EfqrNec2JNDP+oFOdwq1zjl2Y/zJaQ=; b=taVBvevwbwEjZNfLAK9CvMkjSq2V5bfuoRX8Gys9K8kiJaxHw2BSx7vx97i+Oe+sit wM3mqj3aSNjssODPbb87yYehqFLI9DD6ncGHu1fdXegw7zfNRXrtE2RIdvgSRs18O1GT Jt90IIxYhOdd7fz9nAdCX11Ks2VhHNpE9V1jec6V/4A6TnU5A1q1WdZSIGfs93CozpDc HM4z2SoNf29bCsoBnZGh5pjFt08t6D1bT7DhGvTmq/dVrYlv43sHXSeOqk1SrUHU7P7s 5lWbYyillWU6JCKFoxZwqoVzm0H8QOIuuLYuZOQPqAsW1YAAlYSz8yYdP44CnDlHpB4v vyWQ== X-Gm-Message-State: APzg51BZJHD+R+yJK6mi59G456/xIGaAD5CErjmZKeTblXpZau8ndfp0 xg90hpDFwnIvLyadf97hTSz1d0XyCECNySC5cEb9sA== X-Google-Smtp-Source: ANB0VdYLqYOoFbOVygBG2oGMYV08jjVPqxDCcBPiJfU+k1opbMxTNaJn3qujhuppVarPwTBshQyV/lVE7cJYyMVwea0= X-Received: by 2002:a50:f5ae:: with SMTP id u43-v6mr15747596edm.75.1535355560991; Mon, 27 Aug 2018 00:39:20 -0700 (PDT) MIME-Version: 1.0 References: <1535286372.35121837@apps.rackspace.com> <2282D31E-CBEF-4B42-A6A6-4D6394EE0DF7@gmail.com> In-Reply-To: From: Bob McMahon Message-ID: To: luca.muscariello@gmail.com Cc: chromatix99@gmail.com, bloat-announce@lists.bufferbloat.net, Make-Wifi-fast , cerowrt-devel@lists.bufferbloat.net, dpreed@deepplum.com, bloat Content-Type: multipart/alternative; boundary="000000000000d1473e057465d2c4" X-Mailman-Approved-At: Mon, 30 Mar 2020 07:21:14 -0400 Subject: Re: [Cerowrt-devel] [Bloat] [Make-wifi-fast] closing up my make-wifi-fast lab X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Date: Mon, 27 Aug 2018 07:39:22 -0000 X-Original-Date: Mon, 27 Aug 2018 00:39:09 -0700 X-List-Received-Date: Mon, 27 Aug 2018 07:39:22 -0000 --000000000000d1473e057465d2c4 Content-Type: text/plain; charset="UTF-8" Hi Luca, What is non private spectrum defined as per "I don't yet see how a non private spectrum can be shared w/o LBT." Thanks, Bob On Mon, Aug 27, 2018 at 12:24 AM Luca Muscariello < luca.muscariello@gmail.com> wrote: > 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 >> > --000000000000d1473e057465d2c4 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Luca,

What is non private spectrum d= efined as per=C2=A0 "I don't yet see how a non private spectrum ca= n be shared=C2=A0 w/o LBT."

Thanks,
Bob




On= Mon, Aug 27, 2018 at 12:24 AM Luca Muscariello <luca.muscariello@gmail.com> wrote:
<= blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px= #ccc solid;padding-left:1ex">
Jonathan,
Not that giant handwaving though.
IEEE 802.11ax makes use = of "almost TDM" RTS/CTS and scheduling. The almost is necessary a= s it operates in 2.4/5Ghz bands.
Similar to what you describe, and is c= oming very soon in shipping products.=C2=A0

RTS/CT= S is still a LBT to create a window 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 the other hand, medium sharing is one thing, t= he 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 achieved
with careful radio planning = for spatial diversity or dynamic bean forming.

Whe= n you approach capacity with WiFi you only see beacon traffic and almost ze= ro throughput.=C2=A0
Cannot forget Mobile World Congress where yo= u can measure several thousands 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 AM 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

_______________________________________________
Bloat mailing list
Bloat@list= s.bufferbloat.net
https://lists.bufferbloat.net/listinfo/bloat
--000000000000d1473e057465d2c4--