alt Hacker News> or being thrown into a reconnect loop when the AP tries to get them to roam
The AP does not have visibility into what the client actually sees, and no, a coordinator that has knowledge what the APs see isn't that much better.
Imagine a situation with two APs and a client being in the middle of the two in a RF-impeded situation (i.e. your typical office building). AP1 may "hear" the client better (i.e. it gets a higher RSSI and SNR), but the client may reject it in favor of AP2 because the client sees a better signal coming from AP2 due to reflections, a powerful RF signal from a floor above interfering with the channel of AP1 or God knows what else.
RF is a weird world.
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I'm no RF expert, and we're not a big company. I wear many hats, from DBA to local WiFi expert. And while there are certainly limits to what can be achieved without dedicated experts, I want to stress how DECT in the very same scenario just delivers unwavering reliable operation without me ever giving a hoot about RF interference or 802.11k or r or any other implementation detail.
This has been a solved problem in the land mobile radio world for a number of decades.
You have a bunch base stations forming a logical channel with a single uplink frequency, and either a single downlink frequency on which every base station is precisely synchronised in frequency and time (simulcast), or multiple downlink frequencies (a multicast system).
A comparator selects, or votes, the highest quality signal from the base receivers based on either lowest noise or lowest BER, and then repeats that through all of the base transmitters simultaneously.
At the same time, in a multicast system, the mobile scans for and selects the base transmitter with either the highest RSSI or lowest BER.
How much money do you have? Nokia's Centralized RAN basically solves for cellphones by not choosing between AP1 and AP2. The device yells out a packet, both radios hear it, and the signals are combined in baseband processing. Wifi 8 doesn't quite do this, maybe 9's gonna have it. Or the patents run out and the telecom networks cooperate and everything gets a cell modem.
Often times the problem is that the client radios are much weaker than the APs radios.
Sometimes we forget that for the communication to be reliable, signal must flow both ways. Clients will happily connect to far away APs, but won't be reliably heard back.
Solution is to use more APs and lower their radio tx power. A lot of customers push back on the approach because they have only one gaming router monstrosity in their country home and it works perfectly, not understanding that their downtown office with 150 devices have nothing in common.