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@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@gmail.com> wrote:
> On 27 Aug, 2018, at 10:11 pm, Bob McMahon <bob.mcmahon@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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