VMAC

Abstract

The current Medium Access Control (MAC) protocol of the Wireless Access in vehicular ad hoc networks (VANET) is based on IEEE 802.11 Distributed Coordination Function (DCF) and Enhanced Distributed Channel Access (EDCA). Unfortunately, given the high demand for bandwidth, these protocols have drawbacks, one of them is a large number of transmission collisions. Time Division Multiple Access (TDMA) can be an alternative to solve this problem. However, it is not suitable in that it can be problematic because of rapid changes in the vehicular network topology such as highway. In this environment, unused slots result in a waste of bandwidth. In this thesis, we propose a novel hybrid MAC protocol, called Vehicular Medium Access Control (VMAC), for VANET that combines the strengths of CSMA and TDMA while complementing their weak points. Like CSMA, VMAC achieves high channel utilization under low contention by permitting random access and like TDMA, achieves high channel utilization under high contention by allocating time slots and reducing collisions. We evaluate VMAC through extensive NS-2 simulations.