The IEEE 802.11 family of standards describe the DCF protocol, which controls access to the physical medium. A station must sense the status of the wireless medium before transmitting. If it finds that the medium is continuously idle for DCF Interframe Space (DIFS) duration, it is then permitted 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) [1]
| Standard | Slot time (µs) | DIFS (µs) |
|---|---|---|
| IEEE 802.11-1997 (FHSS) | 50 | 128 |
| IEEE 802.11-1997 (DSSS) | 20 | 50 |
| IEEE 802.11b | 20 | 50 |
| IEEE 802.11a | 9 | 34 |
| IEEE 802.11g | 9 or 20 | 28 or 50 |
| IEEE 802.11n (2.4 GHz) | 9 or 20 | 28 or 50 |
| IEEE 802.11n (5 GHz) | 9 | 34 |
| IEEE 802.11ac (5 GHz) | 9 | 34 |
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.
YouTube Encyclopedic
-
1/3Views:5 7469 54221 845
-
Csma Ca
-
Distributed Coordination Function DCF 7
-
Hidden Terminal Problem (CSMA/CA) RTS-CTS Mechanism
Transcription
See also
References
- ^ "IEEE 802.11 Standard"., 2016, Equation (10-6), page 1332.
This page was last edited on 26 June 2018, at 04:39