Coordinated Multichannel MAC Protocol for Vehicular Ad Hoc Networks

Vehicular ad hoc networks (VANETs) provide information and entertainment to drivers for safe and enjoyable driving. Wireless Access in Vehicular Environments (WAVE) is designed for VANETs to provide services efficiently. Since the control messages transmitted in WAVE are broadcast, the probability of collision increases by increasing the number of vehicle nodes. In this paper, we propose a coordinated multichannel medium access control (C-MAC) protocol for VANETs. The proposed C-MAC protocol provides contention-free broadcasting for safety messages by the coordination of roadside units (RSUs). An RSU schedules the broadcasting order of transmissions for safety messages. Contention-free broadcasting lowers the probability of collision and reduces the required time for transmissions of safety messages. An RSU may play the role of harvesting energy wirelessly to coordinated VANET terminals, which are gateways for Internet-of-things devices in the car. The contention interval for service channels is optimized to provide maximum throughput. The proposed C-MAC protocol is shown to enhance throughput and delay via analysis and simulation.