From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-x22c.google.com (mail-qt0-x22c.google.com [IPv6:2607:f8b0:400d:c0d::22c]) (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 46F0C3CB35; Thu, 30 Aug 2018 16:36:51 -0400 (EDT) Received: by mail-qt0-x22c.google.com with SMTP id g44-v6so12151168qtb.12; Thu, 30 Aug 2018 13:36:51 -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:content-transfer-encoding; bh=oER4gfZRNOfpEjuouw5oO9H4dj5OHAyaa3CKnWx6GBE=; b=B0QvyRWe4YF1b+C7h41HNPrsKwbp57MQO+AoTLBYGeSnb1SiDguziAhjPbqkRZyQ6p KcUMgwzmg3V4m9X7/RiSObFgjEfo126a8mIlrVBW7/oA9HpaEBUff6DfzKFSui39wmcC KvYeuTC1kZX70MPyI/qaXA+eoWhE7mfNrLNScrPq5OvoyL68UWDxlxmol5o6yuYBauxz TV3Nx3d9xmMvv/adztwSyQ0zV3UQ/60KKXRCTktvFbBsaMUdv8Z5OYbZJNFACoJOBZVW 9LMWMMLItylTnV2KDoddYjvwHP6fDpK5y+JbNG8NDK3CAJ7lRbgNdl+luFClFeEmn14x PWkg== 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:content-transfer-encoding; bh=oER4gfZRNOfpEjuouw5oO9H4dj5OHAyaa3CKnWx6GBE=; b=OHrr7iK3Yb0gihvnga/7Kn7vdq/3gTI+c5cdwtle1WCuz/zh7PT3C9ewKbub/OwJe3 9bDpegboEmcvh3MQwKbw8lrRs1c93dNrT/dhaUwGlL5MKau3PYwQZtgRyAC8ZSToiEtN 0Jtq4TxupEvUk62xsF5QLvHWZWkUe31Kq17795vtSQsOk/UIhVtKv9QWyITLSwzbMR8B 8nppR2zJjzzI4JByryFgRE4+fQCpyLTkvsZjzRsj0BxG2egLzh51K0vCuiqIiwoXjYh1 v3DpXThOksmDvsEm/I53RCDyYBN6z3zcp5lOZ81jvCq2ZICdczj0Xqc+UsZgPuLHBmOV 8tIA== X-Gm-Message-State: APzg51DaOXZETqyKajsTkTBCz5qjaYSezremm+P4E3wldyIFAg/IDSOB m9mltpYuJ6Q4qhxBfrZzTf1QeKwYoDoGhBQZbXE= X-Google-Smtp-Source: ANB0VdYq2oLCViJUFzgH1u0EZu9DYyZfJf0iDJiPPd9RvSJJ9+9DoGwIUYMtvAJ8btwI8Fub7/qKK7lXqAHS8PqKP4g= X-Received: by 2002:a0c:af34:: with SMTP id i49-v6mr12863410qvc.125.1535661410738; Thu, 30 Aug 2018 13:36:50 -0700 (PDT) MIME-Version: 1.0 References: <1535286372.35121837@apps.rackspace.com> <2282D31E-CBEF-4B42-A6A6-4D6394EE0DF7@gmail.com> In-Reply-To: From: bkil Date: Thu, 30 Aug 2018 22:36:38 +0200 Message-ID: To: bob.mcmahon@broadcom.com Cc: chromatix99@gmail.com, bloat-announce@lists.bufferbloat.net, Make-Wifi-fast , dpreed@deepplum.com, cerowrt-devel@lists.bufferbloat.net, bloat@lists.bufferbloat.net Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Mailman-Approved-At: Thu, 06 Sep 2018 13:54:04 -0400 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: Thu, 30 Aug 2018 20:36:51 -0000 Yes, I've read that part in the past. These are very good rules of thumb, but there are many inefficiencies to cope with. Note that not all wireless users are "rude" on purpose. It's just that if you want to keep in touch with your relatives in the nearby town, you use the minimal needed power for the given circumstances that happens to be a large amount (point to point). 1a. Let's focus on a point to point link first. Omni antennas would trivially interfere with our own neighborhood as well while working a long link. However, because not everyone has roof access, space for a large aerial or money for an expensive one, using an omni would be considered a local optimum for many. 1b. Let's assume that we are a good citizen using more expensive highly directional antennae and we live at the perimeter. Considering that the reception angle of the most practical ones should be 10-20 degrees, this probably easily illuminates the perimeter of the neighboring town. That wouldn't be deadly interference from that distance, but it means that it's not scalable in the sense that not everyone living at the perimeter could communicate with their respective relative in the neighboring town. It would need a high level of sophistication to achieve that. It would be much more efficient and cost effective if these people cooperated and pooled in resources to build only a handful of well-placed high power transcievers that they digitally shared with each other using low power and inexpensive last mile access technologies. But as the old saying goes, "The common horse is worst shod." So it is cleanest if we simply pay for equipment and maintenance, and a new telco is born. Then as competition intensifies, the spectrum gets clogged up, etc. 1c If we aren't fortunate enough to live at the perimeter, we need to cooperate with hops towards the perimeter. It is energetically the most efficient to have directional links between each of them, but that requires 2-3 antennae at each node. The ones at the perimeter definitely need at least two. For one who lives at the perimeter and only communicates with the neighboring town, it is a local optimum to not purchase and operate two sets of antennae, cables, radios and other tools. Without incentives, taking this to the extreme creates a disconnected ring of perimeter around the town who point outwards. So in worst case, ones in the middle would again need to up their power again to work the distance. 2. To achieve hop optimization, have we reached a level of social sophistication and digital literacy where we can mesh with everything and anyone in sight? I feel that to be a stretch, but let's pretend that we have. Now the "feasible" part is still problematic. Let's stick with the above scenario of inter-town links or sparsely populated areas. If there is nobody to mesh with, we need to artificially deploy and maintain intermediate nodes for this purpose. Who will pay for this? If nobody, it is not feasible. See above point. The local optimum of each user is to not deploy intermediate nodes, and we have reached the tragedy of the commons again. And we didn't even consider "rude" users analogue to an uninvited guest who gobbles all your snacks when dropping by. These are only a minority, but they take plenty. Though UWB wasn't there yet in 1994, it's feasible today. Just imagine if a school deployed a 1GHz UWB transciever on UHF to stream their backups or research data all day over the air because it is less expensive (free) compared to cables. It would not be feasible to peer with any intermediate hop because nobody has such expensive and advanced hardware, so they'd happily operate a point to point link to the nearby town (or partner institution?). That would definitely spoil the fun for many along the route and no amount of LBT can fix that. Also they could have decide to use >100GHz instead, but there is no incentive if the whole spectrum is free, as higher frequencies propagate worse and equipment costs more. So all in all, without incentives, system spectral efficiency doesn't come naturally - you have to work for it. Hard. I'm not saying that we should give up, but it takes much more than a few sentences to come up with rules that really work in real life situations when scaled up. There are pro and contra in many methods of spectrum allocations, no doubt about that, but I don't feel that there exists one clear "best" method that we are purposefully neglecting. Of course at the same time, scalable unregulated alternatives do exist, but we were talking radio above: https://en.wikipedia.org/wiki/RONJA https://en.wikipedia.org/wiki/Modulated_ultrasound https://en.wikipedia.org/wiki/Sneakernet On Thu, Aug 30, 2018 at 9:17 PM Bob McMahon wrot= e: > > Minimizing power is rule #2 per Paul Banan. > > SOME KINDERGARTEN RULES (written in 1994) > > To take the fullest advantage of our new technology with its sharing > of a common resource requires that our smart transmitters and > receivers cooperate. This may sound complicated, but the rules to make > maximum effective use of the shared band are simple -- primarily a > matter of common decency in sharing resources. The rules are somewhat > similar to those you learned in kindergarten, assuming you lived in a > tough neighborhood. > > Rule #1. Keep away from the big bullies in the playground. (Avoid the > strongest signals.) > > Rule #2. Share your toys. (Minimize your transmitted power. Use the > shortest hop distances feasible. Minimize average power density per > Hertz.) > > Rule #3. If you have nothing to say, keep quiet. > > Rule #4. Don't pick on the big kids. (Don't step on strong signals. > You're going to get clobbered.) > > Rule #5. If you feel you absolutely must beat up somebody, be sure to > pick someone smaller than yourself. (Now this is a less obvious one, > as weak signals represent far away transmissions; so your signals will > likely be attenuated the same amount in the reverse direction and > probably not cause significant interference.) > > Rule #6. Don't get too close to your neighbor. Even the weakest > signals are very strong when they are shouted in your ear. > > Rule #7. Lastly, don't be a cry baby. (If you insist on using obsolete > technology that is highly sensitive to interfering signals, don't > expect much sympathy when you complain about interfering signals in a > shared band.) > > Bob > > > On Thu, Aug 30, 2018 at 12:12 PM bkil wrote: >> >> Full-duplex still needs some work, but there is definite progress: >> http://www.ti.rwth-aachen.de/~taghizadehmotlagh/FullDuplex_Survey.pdf >> https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/TR-1= .pdf >> https://sing.stanford.edu/fullduplex/ >> https://spectrum.ieee.org/tech-talk/telecom/wireless/new-full-duplex-rad= io-chip-transmits-and-receives-wireless-signals-at-once >> http://fullduplex.rice.edu/research/ >> >> On Mon, Aug 27, 2018 at 9:46 PM Jonathan Morton = wrote: >>> >>> > On 27 Aug, 2018, at 10:11 pm, Bob McMahon = wrote: >>> > >>> > I guess my question is can a WiFi transmitting device rely on primari= ly energy detect and mostly ignore the EDCA probability game and rather sea= rch for (or predict) unused spectrum per a time interval such that its digi= tal signal has enough power per its observed SNR? Then detect "collisions= " (or, "superposition cases" per the RX not having sufficient SINR) via ins= erting silent gaps in its TX used to sample ED, i.e. run energy detect thro= ughout the entire transmission? Or better, no silent gaps, rather detect i= f there is superimposed energy on it's own TX and predict a collision (i.e.= RX probably couldn't decode its signal) occurred? If doable, this seems s= impler than having to realize centralized (or even distributed) media acces= s algorithms a la, TDM, EDCA with ED, token buses, token rings, etc. and no= t require media access coordination by things like APs. >>> >>> The software might be simpler, but the hardware would need to be oversp= ecified to the point of making it unreasonably expensive for consumer devic= es. >>> >>> Radio hardware generally has a significant TX/RX turnaround time, requi= red for the RX deafening circuits to disengage. Without those deafening ci= rcuits, the receivers would be damaged by the comparatively vast TX power i= n the antenna. >>> >>> So in practice, it's easier to measure SNR at the receiver, or indirect= ly by observing packet loss by dint of missing acknowledgements returned to= the transmitter. >>> >>> - Jonathan Morton >>> >>> _______________________________________________ >>> Make-wifi-fast mailing list >>> Make-wifi-fast@lists.bufferbloat.net >>> https://lists.bufferbloat.net/listinfo/make-wifi-fast >> >> _______________________________________________ >> Make-wifi-fast mailing list >> Make-wifi-fast@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/make-wifi-fast