The decision when to roam is soley dependant on client radio driver/supplicant,
using internal algorithms that look at RSSI, interference, and other factors. We
can use higher management frame data rates, ie bss-minrate 5.5, and "encourage"
clients to roam sooner (Ruckus Smart-Roam), but the final decision is up to the
client. Typically, update to latest radio drivers for (hopefully) best behavior.