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Wireless & Mobility · Advanced

Clear Channel Assessment (CCA)

The physical carrier-sense function that determines whether the medium is busy.

Definition

CCA uses signal detect (preamble detection, about -82 dBm for 20 MHz OFDM) and energy detect (about 20 dB higher, -62 dBm). If either indicates busy, the station defers. 802.11ax OBSS_PD adjusts thresholds for spatial reuse.

Exam tip

Signal detect threshold is far more sensitive than energy detect.

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