Target Corporation has been performing some application & wireless testing on Zebra's TC70 Android 4.4.3 devices. One item we're working through is Android’s behavior of sticking to an AP too long, which is well documented:
https://supportforums.cisco.com/discussion/12543176/workaround-android-devices-do-not-roam-wifi
There have been some consumer apps that directly affect the wpa_supplicant behavior to roam more aggressively, but in our situation with Zebra writing a separate Fusion supplicant over the OS, we're not sure exactly what is all affecting the behavior. There’s also a library in the SDK called wifiWatchdog, which may impact this as well, but that seems to manage the cellular/wifi transition on first glance.
We're interested in this mechanism because roaming should start closer to -70 to -75 (not -85 to -90), for optimal mobility between access points and to prevent connectivity loss due to weak signal. We'd like to work with Zebra to determine if the Fusion supplicant can be adjusted to change the roaming behavior.