An extension to 802.11 specification developed by the IEEE for wireless LAN (WLAN) technology. 802.11r, also called Fast Basic Service Set (BSS) Transition, supports VoWi-Fi handoff between access points to enable VoIP roaming on a Wi-Fi network with 802.1X authentication.
See 802.11 for a complete overview of the 802.11x family of specifications.
See also "Introducing IEEE 802.11r" on Wi-FiPlanet.com.
Also see "How Wireless Networks Work" in the Did You Know... section of Webopedia.