My Android phone regularly disconnects and (immediately) reconnects to wifi. That's not a huge issue for buffered video streaming, but is an issue for VOIP, SSH connections etc. Plus I use Tasker to trigger actions when disconnected from a specific SSID, so it means the screen changes whilst those actions trigger.
Android's "smart network switch" was already turned off for causing similar issues, and the fix in my case seems to have been to disable Power-save for Wireless connections
- Dial *#0011#
- Press the Menu button
- Choose Wifi
- Press the button to turn wifi powersave off
Wifi will disconnect while the new settings are being applied, and then will reconnect