On IEEE 802.1x roaming

Hello, I'm using FreeRADIUS with Coova Chilli in proxy mode with IEEE 802.1Xauthentication (PEAP auth. method to be more specific). In my network there are 6 Access Point that use TKIP as security protocol. Now I need that the Supplicants can do "roaming" between the Access Points. The IEEE 802.1X asserts that can be used two mechanisms to obtain roaming : - PMK Caching - Pre Authentication I would to know how I could implement this mechanisms in my system. Are requested special configuration of FreeRADIUS or to implement roaming I must only configure the Access Point (If so, how I can do this)? Note that Access Point are all on the same subnet. Thanks for all Josh