
IEEE 802.11 MAC Protocol: CSMA/CA
802.11 sender
1 if sense channel idle for DIFS then
transmit entire frame (no CD)
2 if sense channel busy then
start random backoff time
timer counts down while channel idle
transmit when timer expires
if no ACK, increase random backoff
interval, repeat 2
802.11 receiver
- if frame received OK
return ACK after SIFS (ACK needed
due to hidden terminal problem)
sender
receiver
DIFS
data
SIFS
ACK
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