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DCF Interframe Space

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In the DCF protocol any station before getting into transmission business, it has to sense the status of wireless medium. If the medium is continuously idle for DCF Interframe Space (DIFS) duration then only it is allowed to transmit a frame. If the channel is found busy during the DIFS interval, the station defers its transmission.

DIFS duration can be calculated by the following method.

DIFS = SIFS + (2 * Slot time) [1]

Standard Slot time (us) DIFS (us)
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

References

  1. ^ "IEEE 802.11 Standard" (PDF).
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