Mobility and QoS oriented 802.11p MAC scheme for vehicle-to-infrastructure communications

Abstract

Vehicles in Intelligent Transportation System (ITS) can communicate with other vehicles or roadside unit (RSU) within a specific area. In ITS, different services have different requirements of Quality of Service (QoS). For delay-tolerant services, such as FTP and Email, a longtime fairness should be guaranteed, which means vehicles with different speeds should have the same chance to communicate with RSU. While for real-time services, such as voice and video, a low average delay should be achieved. Based on original DCF scheme, much modification work has been done to achieve better QoS for mixed services, but fail to consider the unfairness problem brought by mobility. In this paper, we study the performance of 802.11p MAC scheme under high- speed mobility conditions and build a Mixed-Service-Mobility model to analyze the interaction among different services. By adjusting the minimum contention window size of 802.11p MAC scheme according to different speeds, we succeed in providing a balance between the longtime fairness of delay-tolerant services and the average delay of real-time services. The proposed analytical model is validated against simulation results to demonstrate its accuracy and effectiveness.