PCF Interframe Space is one of the interframe space used in IEEE 802.11 based Wireless LANs

Wireless LAN

A wireless local area network links two or more devices using some wireless distribution method , and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network...

. PCF

Point Coordination Function

Point coordination function is a Media Access Control technique used in IEEE 802.11 based WLANs. It resides in a point coordinator also known as Access Point , to coordinate the communication within the network. The AP waits for PIFS duration rather than DIFS duration to grasp the channel...

 enabled access point wait for PIFS duration rather than DIFS to occupy the wireless medium. PIFS duration is less than DIFS and greater than SIFS (DIFS > PIFS > SIFS). Hence AP always has more priority to access the medium.

PIFS duration can be calculated as follows:

PIFS = SIFS + Slot time

Standard	Slot time (us)	PIFS (us)
IEEE 802.11b	20	30
IEEE 802.11a	9	25
IEEE 802.11g	9 or 20	19 or 30

See also

• DIFS
  DIFS
  In the DCF protocol, a station has to sense the status of the wireless medium before transmitting. If the medium is continuously idle for DCF Interframe Space duration, only then it is supposed to transmit a frame...
  
  
• SIFS
  Short Interframe Space
  Short Interframe Space , is the small time interval between the data frame and its acknowledgment. SIFS are found in IEEE 802.11 networks. They are used for the highest priority transmissions enabling stations with this type of information to access the radio link first...
  
  
• AIFS
• RIFS
  Reduced Interframe Space
  Reduced Interframe Space is one of the new feature introduced in IEEE 802.11n to improve its efficiency. It is used as an alternative for SIFS in some scenarios....
  
  
• EIFS
  Extended interframe space
  Extended Interframe space is used in IEEE 802.11 based WLANs. If previously received frame contains error then it has to defer EIFS duration instead of DIFS before transmitting a frame.This duration is calculated by the below method....
  
  
• Point Coordination Function
  Point Coordination Function
  Point coordination function is a Media Access Control technique used in IEEE 802.11 based WLANs. It resides in a point coordinator also known as Access Point , to coordinate the communication within the network. The AP waits for PIFS duration rather than DIFS duration to grasp the channel...