Next Generation Wireless LANs by Perahia Eldad & Stacey Robert

Author:Perahia, Eldad & Stacey, Robert [Perahia, Eldad]
Language: eng
Format: azw3
Publisher: Cambridge University Press
Published: 2013-04-29T16:00:00+00:00

8.5.2 EIFS

Another mechanism used to protect against hidden nodes is the extended inter-frame space (EIFS). A station uses EIFS instead of DIFS to defer if a frame is detected but not correctly received, i.e. the MAC determines that the frame check sequence (FCS) is invalid. EIFS is defined as:

(8.3)

where ACKTxTime is the time required to transmit an ACK frame at the lowest mandatory PHY data rate. EIFS is intended to prevent a station from transmitting over the ACK of a hidden node when a station is unable to demodulate the data frame and thus correctly set its NAV. If during the EIFS defer a valid frame is received (for example, the ACK) then a DIFS defer is used following the actual frame instead of continuing with EIFS. EIFS usage is illustrated in Figure 8.12.

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