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

[bkil]

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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