A-ADHOC: An adaptive real-time distributed MAC protocol for Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANET) is the foundation of intelligent traffic system (ITS), and many MAC protocols for VANET are proposed, among which a reliable MAC protocol called ad hoc has aroused much attention. By investigating the details of ad hoc protocol, we have discovered several unsolved problems that might lead to a network failure. In this paper, we provide a quantitative analysis of the success probability for contending nodes and prove that an adaptive frame length is quite necessary. We propose adaptive-ADHOC (A-ad hoc) MAC protocol, which implements a robust mechanism supporting the adaptive frame length. Evaluation result shows that A-ad hoc can maintain a high contending success probability and obtain about 50% reduction of response time over original ad hoc protocol, while providing important enhancement on network robustness.