Performance Observations on MAC Protocols of VANETs in Intelligent Transportation System

In the vehicle communication system based on ADHOC network, besides fairness, QoS, hidden and exposed terminal problems, the MAC protocol must fulfill the requirement of practical applications. In order to decrease the transmission collisions in VANETs, a reliable and efficient medium access control (MAC) protocol is needed. Firstly, this paper introduces the applications, the characteristics of VANETs, and the difficulties of MAC protocols in VANETs. Secondly, based on different reactive routing protocols, various MAC protocols (wireless LAN and Adhoc MAC) applied to VANETs are theoretically compared and analyzed for sub-urban, urban, and freeway situations. A qualitative comparison of VANETs MAC protocols were given. Finally, the goals and the design essentials of transmission control in VANET are proposed.