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CCNA Wireless 640-722 Official Cert Guide by David Hucaby

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Collision Avoidance

The 802.3 and 802.11 standards differ when it comes to dealing with collisions. Wired devices can detect collisions in real time so that they can back off and wait a random time to try again. This is known as CSMA/CD (collision detection).

Wireless devices always operate in half-duplex mode, which prevents a client from receiving signals on a channel while it is transmitting. This means that a transmitting wireless client can’t detect when a collision occurs at all. Therefore, 802.11 devices must try to avoid collisions in the first place, resulting in the CSMA/CA (collision avoidance) scheme.

Wireless clients avoid collisions by backing off and waiting a random time before transmitting. If a client has a frame to transmit, ...

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