[throw0101a]

> only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions.

Not true with newer standards:

> Orthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user wireless transmission technology that divides a single Wi-Fi or cellular channel into smaller subcarriers called Resource Units (RUs), allowing multiple devices to transmit data simultaneously.

[…]

> Instead of one device occupying the entire channel (as in OFDM), OFDMA allows parallel transmissions. As a result, network congestion decreases significantly.

* https://www.netcomlearning.com/blog/what-is-ofdma

* https://airheads.hpe.com/blogs/antar1/2020/10/19/why-is-ofdm...

> In addition, the 802.11ax standard defines the smallest subchannel as a resource unit (RU), which includes at least 26 subcarriers and uniquely identifies a user. The resources of the entire channel are divided into small RUs with fixed sizes. In this mode, user data is carried on each RU. Therefore, on the total time-frequency resources, multiple users may simultaneously send data in each time segment, as shown in the following figure.

* https://info.support.huawei.com/info-finder/encyclopedia/en/...

* https://blogs.cisco.com/networking/wi-fi-6-ofdma-resource-un...

With a 26-Tone RU Type, nine devices can operate simultaneous in even a 20 MHz channel (eighteen in 40 MHz, etc); see Figures 2 and 3:

* https://www.mpirical.com/knowledge-base/wi-fi-6-and-ofdma

[timeinput]

OFDMA just makes the channels smaller. Sure there are now 10 transmitters on channel 5, but there's one transmitter on channel 5.1, one on 5.2, ... and each 'channel' has 1/10th the capacity of "channel 5".

[throw0101a]

> OFDMA just makes the channels smaller.

Yes, and? If a device only needs 26 tones, that's what will be assigned; if it needs 52 or 106, then that will assigned:

> RU allocations can happen with a combination of tones. For example – if there are three stations associated, then the AP can assign 106 tones to the first two users and 26 tones to the third user. The AP can also assign 52 tones to the third user. These RU allotment decisions are dynamically made by the AP based on the client’s traffic type and its available amount for transmission. The AP learns the client’s buffer status by using a periodic sounding mechanism.

* https://blogs.cisco.com/networking/wi-fi-6-ofdma-resource-un...

Scheduling is not static; Figure 4:

> In the first scheduling interval, the AP allocates the whole 20 MHz channel—a single, 242-tone RU—to Client 1. And in the third interval, it allocates two 106-tone RUs to Client 2 and Client 3.

* https://www.arista.com/assets/data/pdf/Whitepapers/WiFi-6.pd...

And can even be done on a per frame/PPDU basis:

* https://assets.ctfassets.net/wcxs9ap8i19s/2cAbZviv89ZKQZrXo9...

Why give one client more than it needs (when another client can also share the transmission time slot)? If it happens to need the entire x MHz channel, it may be given it (all the RU tones).