As long as there isn't any other stuff on 2.4 GHz, it can indeed be beneficial.

But if there are any legacy 802.11 (especially pre-802.11n) or non-802.11 transmitters nearby, it can be catastrophic for throughput, both because you need protective measures when transmitting (so that older 802.11 versions can reliably detect your transmissions as occupying the carrier) and because some of them just don't cooperate well with 802.11 at all (e.g. Bluetooth, which will just happily transmit over 802.11 without any regard for CSMA/CA fairness at all).

Yes, 802.11ax added all the technology required to allow subchannel slicing in both the time and frequency domains.

Lets say you had a 5ghz 8x8 160mhz AP (maximum allowable by spec): if all you had were 1x1 20mhz clients, you could theoretically have 64 different clients concurrently communicating with the AP without any real problems.

2.4ghz does not have 160mhz channels, but allows up to 40mhz. Ignoring the fact that 2.4ghz is incredibly congested, and you will never achieve peak performance, you can still achieve a theoretical maximum (again, with 1x1 20mhz clients) of 16 concurrent clients.

That said, I'm more interested in 802.11be: MIMO across bands. Instead of hard disabling 2.4ghz (which I 100% recommend all people do: this cures all Wifi ills; and if you have a building that eats 5ghz, either move or spam APs), the AP will dynamically use 2.4ghz as a possible MIMO band.

Theoretical maximum configuration of 802.11be is 40+160+320 (one 40mhz 2.4ghz channel, one 160mhz 5ghz channel, 1 320mhz 6ghz channel), and 802.11be devices will simultaneously communicate across all of them; maximum MIMO configuration has also been increased to 16.

In other words, the future is an AP that looks like a hedgehog, and has 10gbit port.

> if you have a building that eats 5ghz, either move or spam APs

The insanity of moving just to get better wifi reception aside, do you mean move to North America where houses are built out of cardboard and sticks? Most other countries build walls out of solid materials and 5 GHz isn't getting through more than maybe one of those.

As for spamming APs, I really wish it were that simple. Apple devices cling to their AP until speeds drop to the dialup days and other platforms aren't much better. How did we figure out GSM roaming in the 90s but WiFi roaming is still a disaster 30 years later?

If you've set up many APs already, and find client devices sticking to them too strongly, this is a sign to turn down transmit power on the AP in question. Most ship set to "Max" which is terrible for SNR and spatial separation. Turning down transmit power will cause the client to switch sooner, non-intuitively providing more bandwidth due to better utilization of spatial separation.

The mere fact there is a single knob for 'transmit power', rather than the transmit power being automatically determined by the clients location relative to the AP, other AP's, and noise sources tells you a lot about the maturity of WiFi as a spec...

I've seen that work well in open areas where APs overlap significantly, but in places with walls where you walk from one bubble to another, it still usually takes to long for a device to figure out it should switch and then actually do it. I've never had a video call even stutter when moving between LTE cells, but on WiFi, calls sometimes drop outright, even when walking down a long hallway with many APs.

Use APs that are designed for group deployment.

Deploying Ubiquiti's APs in managed (as opposed to standalone) mode makes this easy; even iPhones will transparently be passed from one AP to the next. I agree, though, the OSX/iOS roaming preference tuning is a bit batshit; they also refuse to drop your house's Wifi as you're driving away and want to switch to LTE ASAP.

Commodity/consumer APs aren't designed for handoff.

Keep in mind just because you can't "see" the network doesn't mean it isn't causing low level interference.

Plus also 5GHz is more resilient than that. Even in a solid concrete new apartment building in London I'd see absolutely endless 5GHz networks.

OH!!! Now I understand why people say 5Ghz doesn't go though walls!

I knew other countries had heavily walls but didn't make that connection.

I quite like our cardboard walls though, they are trivial to repair and upgrade, and they rarely get damaged in real life, except if a Real Tough Guy punches one.