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

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 QoS. For delay-tolerant services, a longtime fairness should be guaranteed, which means vehicles with different speeds should have the same chance to communicate with RSU. What´s more, the throughput is a key QoS metric for delay-tolerant services. While for real-time services, a low average delay should be achieved. In this paper, we build a Mixed-Service-Mobility (MSM) model to analyze the interaction among different services under high-speed mobility condition. By adjusting the minimum contention window size of 802.11p MAC dynamically, we succeed in providing a balance between the throughput of delay-tolerant services and the average delay of real-time services on the basis of ensuring the longtime fairness of delay-tolerant services. The proposed analytical model is validated to demonstrate its accuracy and effectiveness.