From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-x12e.google.com (mail-lf1-x12e.google.com [IPv6:2a00:1450:4864:20::12e]) (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 2CB053B29E; Mon, 27 Aug 2018 02:26:36 -0400 (EDT) Received: by mail-lf1-x12e.google.com with SMTP id g9-v6so11044851lfh.1; Sun, 26 Aug 2018 23:26:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=MROADX34OpAZLu52BDPpnESyagYy+mTj+TkJXeR+EKU=; b=Xp5hgg/uDXyRkLwy73r65yU5D4vhOJk5G+HG/nF82xKbPrunIeng3E2cmOMV+sy6Xa cSsA/xr/n+9+lVyWlEfEfFEtL9qnRYQXir1LlAL1KX2nd6p+GosbDHJkBCLRhYaaJr7T 3nE6oT7QlFjAEqEefWSJR0doD5srA/dJ0aE2CQSI+l51pfVMS1JnlZoP1YlMjuf+GEPA TquPj0tsdsDksVk79m8zY0BoYF52OMr59Al/TG/nQKY1elUI/KILTu8wkf3nKvbOkgI5 tBr/F9KTbtM/annI/zy3YB+DYxrTED9+UAHFye6slapN/xfh9yYmNJznN7NxRoAM+AGd /8OQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=MROADX34OpAZLu52BDPpnESyagYy+mTj+TkJXeR+EKU=; b=IxMtgmIHlEL+b7+OF6DBDoZFe5bG9LthUi2DPtWhGUQxDR9VAwNGCU7gNvjr9x9lO3 2sHW+fgmr34xB9vBs/uOUaUc5r8ogBZRjEbp4llv90XLQ9ZyfMwp0MQOshd+GsolDbCR +it5dOOg7bkhvPobqn7d+RDmTWd09qHDhOrM+s8hIf8Xp2WuJ7+FgPUaeX3SZLrwAngM 7RuaxqU/1DoKIwEJ0fagv3Qok+VoF9rW26+OxVLiau6LmEiTQ6YgyzSjS34umePBO0d5 t9AQBcUsbKHmv7NOrdnd532zQKGux0kL3s5TNETff+Mnmvh4LWD9a5ccwu/kV7Z9OKRH VJtA== X-Gm-Message-State: APzg51BSGOldL7SnODGXL/rAui7FYlFxLBJ4iLfCYVxFzPqes4saZwrl mAayG91DptXKPJ67bDcdx9o= X-Google-Smtp-Source: ANB0VdZCq4J88GmguXSM+xOojeILvK9x4M3pt3zoB8uAoo7Kip3zbTDrJYe5D6BXpkixmmEdTCCnRw== X-Received: by 2002:a19:e307:: with SMTP id a7-v6mr7174887lfh.125.1535351194996; Sun, 26 Aug 2018 23:26:34 -0700 (PDT) Received: from jonathartonsmbp.lan (83-245-238-14-nat-p.elisa-mobile.fi. [83.245.238.14]) by smtp.gmail.com with ESMTPSA id h4-v6sm2671216lfj.69.2018.08.26.23.26.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 26 Aug 2018 23:26:34 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: Date: Mon, 27 Aug 2018 09:26:32 +0300 Cc: dpreed@deepplum.com, bloat-announce@lists.bufferbloat.net, Make-Wifi-fast , cerowrt-devel@lists.bufferbloat.net, bloat Content-Transfer-Encoding: quoted-printable Message-Id: <2282D31E-CBEF-4B42-A6A6-4D6394EE0DF7@gmail.com> References: <1535286372.35121837@apps.rackspace.com> To: Bob McMahon X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Make-wifi-fast] [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 06:26:36 -0000 > On 27 Aug, 2018, at 9:00 am, Bob McMahon = wrote: >=20 > 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