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Basic access protocol features – Siemens IEEE802.11 User Manual

Page 31

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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.