Earlier quoted context omitted.
> only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions. That’s not correct. You and your neighbor can use the same channel at the same time. On your network, the transmissions of the other network appear will appear as noise. As long as the other devices are far enough away, however, your devices will still be able to make out their own…
This is a common misconception.. you and your neighbour can configure the same channel, you cannot successfully transmit at the same time on the same channel within range. Nor can you and your own AP successfully transmit at the same time on the same channel. When you and your neighbour _appear_ to be transmitting at the same time, each adapter is actually spending most of it's time waiting for a clear medium and for…
That's not correct. WiFi is "listen before talk." Radios listen to the channel, trying to decode preambles from other networks, before transmitting. In that process, they can detect other signals well below the threshold where they'll consider the medium in use (the CCA threshold). If you have an otherwise clean channel, the noise floor might be -95 dBm. Radios typically can decode the preambles 3-4 dB above the noise floor. Conventionally, the WiFi standards set the CCA threshold at -82 dBm. So the radio can "hear" a lot of signals that won't cause it to trigger collision avoidance. More recent standards allow using a CCA threshold as high as -62 dBM under certain circumstances to facilitate spatial reuse: https://arista.my.site.com/AristaCommunity/s/article/Spatial....
Also, what the Wifi standards do is less aggressive than what radios could do. The CCA thresholds are set to facilitate orderly use of the spectrum--they're not physical limits. To receive a transmission, you just need sufficient signal-to-noise ratio. An adjacent network transmission raises the noise floor, but if your radio is close enough to your AP, you might still have sufficient SNR.