What is the purpose of CSMA/CA in wireless networks?

• A. Carrier Sense Multiple Access with Collision Avoidance; devices listen before transmitting and use acknowledgments to avoid collisions.
• B. Dedicated token-passing protocol used in wireless networks.
• C. Protocol for balancing authentication keys.
• D. A method of channel allocation using frequency hopping.

Answer: (A)

CSMA/CA aims to let devices share a wireless channel efficiently by listening before transmitting and using collision avoidance mechanisms. A device first checks if the channel is idle; if it is, it waits a short period and then transmits. If two devices might collide, backoff timers cause them to wait random durations before attempting again, reducing the chance of another collision. RTS/CTS handshaking can be used to further prevent collisions, especially when hidden nodes could cause problems. After a frame is received, the receiver sends an acknowledgment to confirm delivery; if no ACK is received, the sender assumes a failure and retries after a backoff. The purpose, then, is reliable delivery on a shared medium by minimizing collisions and providing feedback to trigger retransmissions. Other concepts like token-passing, channel hopping, or key management describe different mechanisms and are not what CSMA/CA is about.