CSMA/CA

networking

Stands for: Carrier Sense Multiple Access with Collision Avoidance

Wi-Fi's channel etiquette: a radio cannot hear a collision while it is transmitting, so stations work to avoid collisions up front with waits, random backoff, and per-frame acknowledgements.

IEEE 802.11 adopted collision avoidance because detection is physically off the table on radio: a transmitter drowns out its own receiver, and the hidden node problem means two stations can both be audible to the access point yet deaf to each other. So a station waits for the medium to go idle plus a spacing interval, counts down a random backoff, transmits, and treats a missing acknowledgement as a collision to retry. The optional RTS/CTS exchange reserves the air in advance, taming hidden nodes at the cost of overhead. The contrast with CSMA/CD is the classic exam question: Ethernet detected collisions after the fact, Wi-Fi spends effort so they mostly never happen.

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