Performance Evaluation of IEEE 802.11p MAC Protocol for VANETs

With an increased emphasis on transportation safety requirements, Vehicular Ad-hoc Networks (VANETs) have emerged as the key underlying technology in the realization of Intelligent Transportation Systems (ITS). The IEEE-1609 set of standards for Wireless Access for Vehicular Environment (WAVE) specifies an architecture that includes new standards for vehicular communication, aimed at supporting applications for ITS. IEEE-802.11p standard forms the bottom layers of WAVE protocol stack and includes enhancements to the physical (PHY) and medium access control (MAC) layer protocols. The IEEE-802.11p MAC protocol is derived from distributed coordination function (DCF) of the IEEE-802.11, and also uses the IEEE-802.11e EDCA based quality-of-service (QoS) amendments. To meet the requirements of safety applications, it is important to for a VANET MAC protocol to reduce the medium access delay. Some of the issues that need to be addressed include prioritized access, unpredictable response and reliability. In this work, we have evaluated IEEE-802.11p MAC method by developing a VANET model using MATLAB simulations. We considered a highway scenario where time-critical packets are periodically broadcast in vehicle-to-vehicle communications and evaluated channel access delay and probability of channel access. We observed how quickly a node gets access to the network because transmission or communication would only be possible until a node get access to the network. A node must get access before the deadline expires because if it will not succeed in, then it will not be able to transmit critical information like accidents to its neighboring party