Performance Analysis of the IEEE 802.11p EDCA for Vehicular Networks in Imperfect Channels

The IEEE 802.11p protocol was designed to support effective inter-vehicle communications for Intelligent Transportation Systems (ITS). The Medium Access Control (MAC) sub-layer in IEEE 802.11p employs Enhanced Distributed Channel Access (EDCA) mechanism in order to support differentiated Quality-of-Service (QoS) by introducing four Access Categories (ACs). Performance evaluation of 802.11p EDCA has attracted many research interests. However, most of the existing works assume perfect wireless channels that are error-free. In this paper, we propose a new analytical model based on a 3-D Markov chain and Queuing analysis to evaluate the IEEE 802.11p EDCA under imperfect channels with both saturated and unsaturated traffic. All influential factors of the 802.11p EDCA are considered, including the backoff counter freezing, AIFS defers, the internal collision, and finite MAC buffer sizes. The effectiveness and accuracy of the developed model have been validated through extensive ns-3 simulation experiments.