Extended Interframe space (EIFS) is used in IEEE 802.11 based WLANs.
If a previously received frame contains an error then a station has to defer EIFS duration instead of DIFS before transmitting a frame.
It should have the opportunity to return an Acknowledgment frame; the EIFS ensures the transmission of the Ack can proceed without interference from those not able to decode the frame.
EIFS = Transmission time of Ack frame at lowest phy mandatory rate + SIFS + DIFS[1]
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