Formal Analysis of MAC in IEEE 802.11p with Probabilistic Model Checking

Abstract

In vehicular ad-hoc network, Media AccessControl (MAC) is one of the technologies which determinewhether the information is transferred reliably and timely or not. It is also a key to the quality of service of self organizationnetworks. Some behaviors of the MAC protocol can be estimatedby experiment and simulation. But the main drawback of thesemethods is that the estimation can not be accurate to support theenough confidence. In this paper, we complete the preciseanalysis of the MAC protocol by probabilistic model checking. First, based on the nature of MAC, its dynamic behavior isabstracted into a probabilistic timed automata which candescribe non-deterministic, continuous time and the probabilityselection of MAC. Then we calculate the probability of the datasent successfully and the probability of the backoff counterreaching the maximum value. The analysis result shows that theprobability of conflict in 802.11p is much smaller than the 802.11standard. Therefore the waiting time in 802.11p is significantlyreduced and in the case of fast-moving, the data can be senttimely. Further we calculate the maximum expect conflictnumber under the different values of maximum backoff and thelongest time to complete the data transmission. The result showsthat when the value of maximum backoff increases, the numberof collisions that occurred in 802.11p tends to be stable, which isless than the 802.11 standard's collisions, and the average speedof the data transmission in 802.11p is as four times faster as the802.11 standard.