DIFS
Encyclopedia
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 (DIFS) duration, only then it is supposed to transmit a frame. If the channel is found busy during the DIFS interval, the station should defer its transmission.
DIFS duration can be calculated by the following method.
DIFS = SIFS + (2 * Slot time)
IEEE 802.11g is backward compatible with IEEE 802.11b. When these devices are associated with same AP all the timing parameters are changed to 802.11b.
Distributed Coordination Function
Distributed coordination function is the fundamental MAC technique of the IEEE 802.11 based WLAN standard. DCF employs a CSMA/CA with binary exponential backoff algorithm....
protocol, a station has to sense the status of the wireless medium before transmitting. If the medium is continuously idle for DCF Interframe Space (DIFS) duration, only then it is supposed to transmit a frame. If the channel is found busy during the DIFS interval, the station should defer its transmission.
DIFS duration can be calculated by the following method.
DIFS = SIFS + (2 * Slot time)
| Standard | Slot time (µs) | DIFS (µs) |
|---|---|---|
| IEEE 802.11b | 20 | 50 |
| IEEE 802.11a | 9 | 34 |
| IEEE 802.11g | 9 or 20 | 28 or 50 |
IEEE 802.11g is backward compatible with IEEE 802.11b. When these devices are associated with same AP all the timing parameters are changed to 802.11b.
See also
- SIFSShort Interframe SpaceShort 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...
- PIFSPCF Interframe SpacePCF 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...
- AIFS
- RIFSReduced Interframe SpaceReduced 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....
- EIFSExtended interframe spaceExtended 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....
- DCFDistributed Coordination FunctionDistributed coordination function is the fundamental MAC technique of the IEEE 802.11 based WLAN standard. DCF employs a CSMA/CA with binary exponential backoff algorithm....