Point Coordination Function (PCF) is a media access control (MAC) technique used in IEEE 802.11 based WLANs, including Wi-Fi.
[1] The PCF is located directly above the distributed coordination function (DCF), in the IEEE 802.11 MAC Architecture.
Since most APs have logical bus topologies (they are shared circuits) only one message can be processed at one time (it is a contention based system), and thus a media access control technique is required.
PCF seems to be implemented only in very few hardware devices as it is not part of the Wi-Fi Alliance's interoperability standard.
PCF enabled access point wait for PIFS duration rather than DIFS to occupy the wireless medium.