Analytical study of the IEEE 802.11p EDCA mechanism

The Enhanced Distributed Channel Access (EDCA) mechanism has been adopted by media access control (MAC) layer of IEEE 802.11p to provide contention-based differentiated channel access for packets with different priorities. To analyze the performance of EDCA mechanism, the two-dimensional Markov chain model with the different contention windows(CW) and the internal collision and the frozen mechanism, has been proposed to calculate the normalized throughput and the time delay. The results show that the normalized throughput decreases and the time delay increases with the number of vehicles increasing; and the packets with higher priority have a larger numerical value of normalized throughput and lower time delay than the lower priority packets. The delay for high priority ACs satisfy their requirements, which verify that the IEEE 802.11p EDCA can provide effective service for the safety related time critical applications.