Reduced Interframe Space (RIFS) 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.

In some cases even the SIFS gap is not necessary between the consecutive MPDU transmissions from a given station. The value of RIFS is 2 microseconds and is much shorter the SIFS time.

See also

• SIFS - Short Interframe Space
  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...
  
  
• PIFS - PCF Interframe Space
  PCF Interframe Space
  PCF Interframe Space is one of the interframe space used in IEEE 802.11 based Wireless LANs. PCF 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 - DCF Interframe Space
  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...
  
  
• AIFS - Arbitration Interframe Space
• PCF - 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...