A flexible and adaptive medium access control protocol for improving quality of service in vehicular ad-hoc networks

Abstract

Designing MAC (Medium Access Control) protocols for VANETs is a difficult task due to the inherently unstable nature of these networks when compared to traditional ad hoc networks (high node speed, position changes that lead to disconnections, signal losses, etc.). In recent years, several standardization efforts have been made by the IEEE in association with the scientific community in this area and they proposed the 1609.4 MAC protocol in the IEEE WAVE (Wireless Access in Vehicular Environments) stack. The aim of our work is to improve the quality of service and overall performances of this 1609.4 MAC protocol by proposing three mechanisms. First, we introduce an equity algorithm that aims to ensure more fairness between nodes. We also adapt the SCH (Service CHannel) interval to the network's needs with a dynamic SCH interval mechanism. Finally, we propose an emergency mechanism that aims to ensure the transmission of critical safety packets when dangerous events occur on the road. The results of our simulations show a significant improvement of the protocol's performances in terms of throughput, packet loss and critical packet delivery rates under several scenarios.