Adaptive TDMA and CSMA-Based MAC Protocols for Vehicular Ad Hoc Networks: A Survey

Abstract

Vehicle Ad Hoc Network (VANET) created between vehicles or between vehicles and centralized infrastructures is a dynamic network. Specifically, VANET can support many services such as safety, traffic management, and user-oriented services to improve transportation efficiency. Medium Access Control (MAC) protocol in VANETs not only responds the different requirements of these services but also improves the efficient broadcasting safety messages. One such protocol is to employ both TDMA and CSMA schemes in the Control CHannel (CCH), called a hybrid MAC protocol. A vehicle will send safety message without collision on the TDMA-based period during its reserved time slot and utilize the SCH resources on the CSMA-based period for the non-safety message. In addition, the TDMA-based period can be adjusted according to vehicle density. Hence, these systems can adapt themselves to various traffic conditions and improve the throughput for safety messages. In this survey, we compare different hybrid MAC protocols using dynamic TDMA-based periods as well as their benefits and limitations. Finally, we discuss some issues and promising future research which can be satisfied different QoS requirements and efficiently support both safety and non-safety services.