On the Design and Implementation of a Real-Time Testbed for Distributed TDMA-Based MAC Protocols in VANETs

Rapid development and deployment of vehicular ad-hoc networks (VANETs) require an efficient and scalable media access control (MAC) protocol to support high-priority safety applications. To meet the requirements, researchers have proposed many distributed TDMA-based MAC protocols for VANET in recent years. Despite the superior performance shown in the simulations, few of the proposed protocols have been evaluated in the real-world environment. However, according to the measurement-based works, the extremely unstable wireless communication of VANETs in the real world challenges the performance of the MAC protocols. Hence it may deteriorate if the protocol is implemented in real vehicles. In this paper, we design and implement a real-time testbed for distributed TDMA-based MAC protocols in VANETs. The testbed utilizes the collaboration of hardware (FPGA) and software (Linux) to handle the high-priority and low-priority tasks, and high-accuracy GPS receiver for time synchronization. Results of the measurements show that the transmission delay of the high-priority packets is bounded and the TDMA access is functional.