Siemens IEEE802.11 Instrukcja Użytkownika Strona 31

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WLAN-IEEE802.11 Tutorial (Maximilian Riegel), 021018-wlan-tutorial.ppt Page 31 © Siemens, 2002
Basic Access Protocol Features
n Use Distributed Coordination Function (DCF) for efficient
medium sharing without overlap restrictions.
Use CSMA with Collision Avoidance derivative.
Based on Carrier Sense function in PHY called Clear
Channel Assessment (CCA).
n Robust for interference.
CSMA/CA + ACK for unicast frames, with MAC level
recovery.
CSMA/CA for Broadcast frames.
n Parameterized use of RTS / CTS to provide a Virtual
Carrier Sense function to protect against Hidden Nodes.
Duration information is distributed by both transmitter and
receiver through separate RTS and CTS Control Frames.
n Includes fragmentation to cope with different PHY
characteristics.
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