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

[Bob McMahon <bob.mcmahon@broadcom.com>]

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ok thanks, that's helpful.  I guess I thought if astrophysicists can direct
image exoplanets
<https://www.space.com/30248-young-jupiter-smallest-directly-imaged-exoplanet.html>
a WiFi device should be able to detect superposition  - though, talk about
some giant hand waving! ;)

Bob

On Mon, Aug 27, 2018 at 12:45 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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