DATA COMMUNICATION PRINCIPLES Interframe Spacing IFS Interframe Spacing

DATA COMMUNICATION PRINCIPLES : Interframe Spacing (IFS)

Interframe Spacing (IFS) Each packet transmitted using DCF obeys the IFS rules specified in the standard. The amount of IFS may have one of the four values depending on the following factors. When the packet is the single data packet generated in a station, or first of a series of data packets, then the IFS is some typical value, called DCF/IFS or DIFS. When the packet is a short priority packet, acknowledgement of a data packet or warning all stations of a reservation/confirmation of reservation, the IFS for such packets is shorter than DIFS and is accordingly called short IFS or SIFS. If a packet is to be transmitted by a delay-bound station during the time reserved for point coordination function (PCF), the IFS is again shorter than DIFS but larger than SIFS. This is called PCF/IFS or simply PIFS. If the PHY indicates to the MAC that a frame could not complete transmission or was in error, an extended IFS is used to allow for the recovery of the lost packet. This is basically DIFS with an extended value. It is called EIFS, or extended IFS. The probability of collision is reduced substantially due to the IFSs.

REFERENCES • Ahmad A. - Data Communication Principles. For Fixed and Wireless Networks • Cornelius T. Leondes - Database and Data Communication Network Systems, Three-Volume Set_. . -Academic Press