Acronym for Carrier Sense Multiple Access with Collision Avoidance

A network access protocol used in Apple's LocalTalk? networks and wireless network access methods. It is a variation of the CSMA/CD protocol used in Ethernet networks. As in CSMA/CD method, each device listens to the signal level to determine when the channel is idle. Unlike the CSMA/CD, it, then, waits for a random amount of time before trying to send a packet. After a while, the device senses the signal level again and if the channel is free, the packet is sent. If the channel is busy, the time interval before the next attempt is doubled. In some versions of the protocol the time interval between attempts is based on the device's position in the devices list.

The principal medium access method employed by IEEE 802.11 wireless LANs (WLANs). It is a ""listen before talk"" method of minimizing (but not eliminating) collisions caused by simultaneous transmission by multiple radios. IEEE 802.11 states the collision avoidance method rather than the collision detection that must be used, because the standard employs half-duplex radios—radios capable of transmission or reception—but not both simultaneously.