Today most, if not all, enterprise grade AP have settings for minimum RSSI values. Think of it this way - having one client on your WLAN that has a weak connection will introduce errors and retransmission impacting every client to a certain extent (it's a shared medium). In a deployment wherin you have multiple AP working together (on different channels) there's going to be overlap so you have a continuation of service. You may move around and be connected to WAP-B with an RSSI of -70 but be closer to WAP-A with an RSSI of -50. Your OS will try to hang on to that connection as long as it can by default since it's not scanning in the background for something better on a differing BSSID (the BSSID is the MAC, generally in a multi-AP environment you'll have a singular SSID and each AP has a unique BSSID).

With minimum RSSI implementations the AP will kick (deauth) clients that no longer meet the minimum RSSI level. This will force them to reconnect to and will go with the stronger BSSID being advertised with the same SSID. Still rudimentary but works rather well. I don't even notice roaming in my home anymore after tuning. It's very evident when you're on a network that has defaulted to auto and all of the channel selection and power output is up for grabs.

If you're looking at doing this with Ubiquiti they have docu and even point out the warts with simple RSSI tuning. Trolling the forums before doing a deployment is something you should do as this equipment isn't really something that will autoconfigure itself very well. I mean, it works - but clearly you can see in this thread that people who just expect it to work have bad things to say about it's effectiveness. What they don't understand is that a lot of those problems are self-inflicted.

Here's a link to the Ubiquiti RSSI guide: https://help.ubnt.com/hc/en-us/articles/221321728-UniFi-Unde...