Performance analysis of slotted Aloha on a three lane motorway using measured vehicle positions

This paper evaluates the performance of the slotted Aloha protocol when used for vehicles sending data to a base station near the motorway. Several statistical models for the distribution of the vehicles on a three lane motorway are analyzed using real vehicle measurements. The measurements are split into three traffic conditions: queuing traffic with low speed, heavy traffic with small average headways, and light traffic. An appropriate model for the vehicle positions is used to calculate packet success probabilities using Rice distribution, capture effect and a single slope path loss model. The success probabilities are used to analyze the throughput and the delay when we use the slotted Aloha protocol for the uplink data stream under different traffic conditions. The results show that, due to the near-far effect, only the vehicles close to the base station have a significant throughput when the data load increases