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Wireless & Mobility · Foundational

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

The 802.11 medium access method in which stations sense the medium and back off randomly before transmitting.

Definition

Because wireless stations cannot detect collisions while transmitting, 802.11 avoids collisions using physical carrier sense (CCA), virtual carrier sense (NAV), interframe spaces, and random backoff. Positive acknowledgments confirm success. Wi-Fi is therefore half duplex and contention-based.

Exam tip

Wired Ethernet used CSMA/CD; Wi-Fi uses CSMA/CA.

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