[Make-wifi-fast] [Cerowrt-devel] closing up my make-wifi-fast lab

Bob McMahon bob.mcmahon at broadcom.com
Mon Sep 3 15:30:13 EDT 2018

Agreed that incentives are non trivial.   I found this article about bike
share redistribution interesting:

New York's bike share system pays rider to make it run better


On Thu, Aug 30, 2018 at 1:36 PM bkil <bkil.hu+Aq at gmail.com> wrote:

> 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 <bob.mcmahon at broadcom.com>
> wrote:
> >
> > 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 <bkil.hu+Aq at gmail.com> 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-radio-chip-transmits-and-receives-wireless-signals-at-once
> >> http://fullduplex.rice.edu/research/
> >>
> >> On Mon, Aug 27, 2018 at 9:46 PM Jonathan Morton <chromatix99 at gmail.com>
> wrote:
> >>>
> >>> > On 27 Aug, 2018, at 10:11 pm, Bob McMahon <bob.mcmahon at broadcom.com>
> wrote:
> >>> >
> >>> > I guess my question is can a WiFi transmitting device rely on
> primarily energy detect and mostly ignore the EDCA probability game and
> rather search for (or predict) unused spectrum per a time interval such
> that its digital signal has enough power per its observed SNR?   Then
> detect "collisions" (or, "superposition cases" per the RX not having
> sufficient SINR) via inserting silent gaps in its TX used to sample ED,
> i.e. run energy detect throughout the entire transmission?  Or better, no
> silent gaps, rather detect if 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 simpler than having to realize centralized
> (or even distributed) media access algorithms a la, TDM, EDCA with ED,
> token buses, token rings, etc. and not require media access coordination by
> things like APs.
> >>>
> >>> The software might be simpler, but the hardware would need to be
> overspecified to the point of making it unreasonably expensive for consumer
> devices.
> >>>
> >>> Radio hardware generally has a significant TX/RX turnaround time,
> required for the RX deafening circuits to disengage.  Without those
> deafening circuits, the receivers would be damaged by the comparatively
> vast TX power in the antenna.
> >>>
> >>> So in practice, it's easier to measure SNR at the receiver, or
> indirectly by observing packet loss by dint of missing acknowledgements
> returned to the transmitter.
> >>>
> >>>  - Jonathan Morton
> >>>
> >>> _______________________________________________
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> >>
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