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

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

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Hmm, not sure I understand the distinction.   CTS per the AP informs those
other transmitters to stay quiet per the CTS NAV.  I may be
misunderstanding things.  Thanks for the continued discussions.  It helps
to better thoroughly understand the issues.

Bob

On Mon, Aug 27, 2018, 6:52 PM David Lang <david@lang.hm> wrote:

> On Mon, 27 Aug 2018, Bob McMahon wrote:
>
> > I thought that RTS/CTS would handle the case of hidden nodes, i.e. a
> device
> > that fails to successfully transmit can resort to RTS/CTS to get the
> > receiver to reserve time for it.  Also, lack of a RX ack seems ok to
> > trigger MAC level retransmits.
>
> the problem isn't getting the receiver to reserve time for it, it's
> getting the
> other transmitter(s) to not step on it when it transmits. Those other
> transmitters may belong to different people, sharing a channel with your
> system
> and nothing else.
>
> David Lang
>
> > It seems the LBT bug is the collision avoidance overheads when it isn't
> > needed, i.e. no other energy would cause the RX PHY to fail its decode
> and
> > the EDCA backoffs had no benefit, stochastic or otherwise.   Optimizing
> > that out is said to be not possible from local information only and per
> > "shared" spectrum.
> >
> > Bob
> >
> >
> > On Mon, Aug 27, 2018 at 3:33 PM David Lang <david@lang.hm> wrote:
> >
> >> On Mon, 27 Aug 2018, Jonathan Morton wrote:
> >>
> >>> 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.
> >>
> >> Also, there may be other transmitters that the recipient of the packets
> >> can hear
> >> that you cannot hear, so it's not possible to detect colliding
> >> transmissions
> >> directly in all cases.
> >>
> >> This is another trap that digital/wired people fall into that doesn't
> >> really
> >> apply in the analog/radio world.
> >>
> >> David Lang
> >>
> >
>

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