Thomas Kunz
Systems and Computer Engineering
169
802.11 MAC Layer
nPriorities
–defined through different inter frame spaces
–no guaranteed, hard priorities
–SIFS (Short Inter Frame Spacing)
nhighest priority, for ACK, CTS, polling response
–PIFS (PCF IFS)
nmedium priority, for time-bounded service using PCF
–DIFS (DCF, Distributed Coordination Function IFS)
nlowest priority, for asynchronous data service
t
medium busy
SIFS
PIFS
DIFS
DIFS
next frame
contention
direct access if
medium is free ³ DIFS