Ethernet. Carrier-sense multiple access with collision avoidance In CSMA/CA collision avoidance is used to improve the performance of CSMA. If the transmission medium is sensed busy before transmission, then the transmission is deferred for a random interval. This random interval reduces the likelihood that two or more nodes waiting to transmit will simultaneously begin transmission upon termination of the detected transmission, thus reducing the incidence of collision. CSMA/CA is used by Wi-Fi. CSMA with Collision Resolution CSMA/CR uses priorities in the frame header to avoid collisions. It is used in the Controller Area Network. Virtual time CSMA VTCSMA is designed to avoid collision generated by nodes transmitting signals simultaneously, used mostly in hard real-time systems. It uses two clocks to prioritize messages based on their deadline. See also Local collision Remote collision References General Andrew S. Tanenbaum, Computer Networks. Prentice Hall, Upper Saddle River, NJ (2003). 892 pp. Media access control