From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-x22b.google.com (mail-qk0-x22b.google.com [IPv6:2607:f8b0:400d:c09::22b]) (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 24EDC3B29E; Mon, 27 Aug 2018 03:52:09 -0400 (EDT) Received: by mail-qk0-x22b.google.com with SMTP id 130-v6so9853619qkd.10; Mon, 27 Aug 2018 00:52:09 -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=1nNUvz7TdoR4nG5S0i7xQa1lXEVyRglcy2s8ASJvKjo=; b=JDeeEMsd1VeEDBw5ywb5gSVhmp9y9Ff2wdWNsFkBbLPLZtjkclJsN5y/tMS7jvhEoI gl8+TT92reOqHKkmBEkGEznuJWOBNuGjbJzAZM4pnsn+o0zEivZSz1B6S3/7x/LP9Bvo vZeky6m7e1qkQyRlUBnq8Qk/4BqDW5S/Ic+my/Go/hmNtCk/ruPBbhZt+vJSNu5svjwa s0Vzrzjj5vNt+YH+huL7Ut2Gn+fIwElYo9hOOfKp3Fsq729XNIH1b41XCF5gM6bsrLX6 PzGmlE2ltai2+v33JOMLTXCIRymGsWM4/dBu4BllJWDz6ICCCGtTWas6hzcyh1oyImgw +hiA== 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=1nNUvz7TdoR4nG5S0i7xQa1lXEVyRglcy2s8ASJvKjo=; b=rTzRtQPQEdG2kmm4wrElECJiuVDLqj2ayc/W2Jn9ossMM4HFb6ApAJpBxBAi5mqIIR jOIXjJOhNe+gHZ5RwKYyb2RG0ASuRP5rJ5ZEHMRGG56mb56yAnJRINCvrilT1LziQDwJ C33ie/aFk3UCT47+5BNYZF0A/job/TqFWoaoRYcremc963HASYTKhSPtnTKwqXFHf4fx 9ZXAkkBGOQhztgpSCSew5WWB2opfRU7I/pHlJsqReQVTa92xoq86aVbuakhrynkffmqu /vdbHVFM2VnGIaHlkaRaspMAgTx9Rt6IheA14+UpkaVL3RZ6iTO/PLhMxl53x2iFQ6YN 9E4A== X-Gm-Message-State: APzg51D6TtTVgPhWjlMLTmq0NIx5SdhvCaH/CsIE/zBPyF3uPEcEmNvu TF9Vw7bx4ySSnmser2ZZzud8fpIeDHurs4iDfp0= X-Google-Smtp-Source: ANB0VdbXsAiVvOOlpfduky5b6Ddfp8VobFaZD+LrevT+ToxBU0w9rryCRRR4NL2lymdIntHlG7hFy9Ox+5gIICEfy+I= X-Received: by 2002:a37:96c1:: with SMTP id y184-v6mr12072057qkd.236.1535356328679; Mon, 27 Aug 2018 00:52:08 -0700 (PDT) MIME-Version: 1.0 References: <1535286372.35121837@apps.rackspace.com> <2282D31E-CBEF-4B42-A6A6-4D6394EE0DF7@gmail.com> In-Reply-To: From: Luca Muscariello Date: Mon, 27 Aug 2018 09:51:57 +0200 Message-ID: To: bob.mcmahon@broadcom.com Cc: Jonathan Morton , 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="000000000000931eb505746600f1" Subject: Re: [Make-wifi-fast] [Bloat] [Cerowrt-devel] closing up my make-wifi-fast lab X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Aug 2018 07:52:09 -0000 --000000000000931eb505746600f1 Content-Type: text/plain; charset="UTF-8" Hi Bob, I meant licensed/unlicensed for private/non private. Luca On Mon, Aug 27, 2018 at 9:39 AM Bob McMahon wrote: > 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 >>> >> --000000000000931eb505746600f1 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Bob,

I meant licensed/unlicensed for= private/non private.

Luca

On Mon, Aug 27, 2018 at 9:39 AM Bob McM= ahon <bob.mcmahon@broadcom.c= om> wrote:
= Hi Luca,

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

Thanks,
Bob



<= /div>

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 necessa= ry as it operates in 2.4/5Ghz bands.
Similar to what you describe, and = is coming very soon in shipping products.=C2=A0

RT= S/CTS is still a LBT to create a window where TDM can be done.=C2=A0
<= div>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 thin= g, the other thing is capacity.=C2=A0
There is no way to efficien= tly 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 plann= ing for spatial diversity or dynamic bean forming.

When you approach capacity with WiFi you only see beacon traffic and almos= t zero throughput.=C2=A0
Cannot forget Mobile World Congress wher= e you can measure several thousands of SSIDs on 2.4=C2=A0
and sev= eral hundreds of SSID in 5GHz. But even LTE was very close to capacity.
=C2=A0
Dave,
Having air time fairness in open so= urce 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

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