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 <da...@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 <da...@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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