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The international standard IEEE 802.11 was developed recently in recognition of the increased demand for wireless local area networks. Its medium access control mechanism is described according to a variant of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme. Although collisions cannot always be prevented, randomised exponential backoff rules are used in the retransmission scheme to minimise the likelihood of repeated collisions. More precisely, the backoff procedure involves a uniform probabilistic choice of an integer-valued delay from an interval, where the size of the interval grows exponentially with regard to the number of retransmissions of the current data packet. We model the two-way handshake mechanism of the IEEE 802.11 standard with a fixed network topology using probabilistic timed automata, a formal description mechanism in which both …