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CSMA/CA

Wi-Fi's listen-before-talk rule: wait until the air is quiet, then wait a random extra moment before sending.

Carrier-sense multiple access with collision avoidance makes a station sense the channel and back off a random time before transmitting, because a radio can't hear a collision while it sends.

Examples

  • Before sending a reading, the greenhouse node listens until the channel is quiet, then waits a random extra moment so it doesn't start at the same time as a neighbour.

  • A radio can't hear a collision while it is sending, so Wi-Fi avoids collisions with CSMA/CA rather than detecting them.

See also

hidden-node problem channel acknowledgement
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