Siemens IEEE802.11 Manuel d'utilisateur télécharger pdf (Page 31)

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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Siemens IEEE802.11 Manuel d'utilisateur Page 31