QoS-assurance-and-mobility-based EDCA mechanism for vehicular network access

Because of the fixed parameters such as minimum contention window (CW), it cannot work well for enhanced distributed coordinated access (EDCA) mechanism in IEEE 802.11p with the changes of vehicles number and speeds. Consequently, the access performance such as throughput and fairness for all traffics deteriorate seriously, especially in high vehicles density. In addition, it cannot balance the Qos requirements between real-time traffics and delay-tolerant traffics. Therefore, two modified EDCA mechanisms are proposed. One named as QoS-assurance-based EDCA (QA-EDCA) can assure the real-time of two high priority traffics, and maximum the saturation of two low priority traffics. Another is called as QoS-assurance-and-mobility-based EDCA (QAM-EDCA). By adjusting minimum CW size according to vehicle speed and other network information, it offers the same functionality as QA-EDCA, and can also solve the unfairness problem for two low priority traffics to access channel due to different vehicle speed. Besides, an analytical model is built. The validity of proposed mechanisms and the accuracy of model are verified by simulation experiments.