A Centralized TDMA based Scheduling Algorithm for Real-Time Communications in Vehicular Ad Hoc Networks

As wireless technologies inside smart cars are increasing, Vehicular Ad hoc NETworks (VANETs) are becoming a promising way to enhance driver and passenger safety by enabling each vehicle to provide a warning in real time when a critical event is predicted. These applications require reliable broadcast schemes with minimum access delay and transmission collisions, which thus increase the need for an efficient Medium Access Control (MAC) protocol. However, the design of an efficient MAC protocol in VANET networks is a challenging task due to the high speed of the nodes, the frequent changes in network topology and various QoS requirements. Motivated by this observation, in this paper we present a Centralized TDMA based MAC protocol named CTMAC for real-time communications in VANETs. In our solution, Road Side Units (RSUs) are used as central coordinators to schedule and maintain time slot assignment for the vehicles in their coverage areas. In this work, we will show how interference between vehicles in the overlapping regions can be avoided without using any complex spectrum mechanisms such as CDMA or OFDMA. The simulation results reveal that CTMAC significantly outperforms the VeMAC and ADHOC MAC protocols in terms of transmission collisions and the overhead required to create and maintain the TDMA schedules.