Siemens IEEE802.11 - Manual (Page 31)

WLAN-IEEE802.11 Tutorial (Maximilian Riegel), 021018-wlan-tutorial.ppt Page 31 © Siemens, 2002
Basic Access Protocol Features
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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).
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Robust for interference.
– CSMA/CA + ACK for unicast frames, with MAC level
recovery.
– CSMA/CA for Broadcast frames.
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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.
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Includes fragmentation to cope with different PHY
characteristics.