Design and Evaluation of a Mobility-Adaptive Slotted ALOHA Protocol for Vehicular Communication Systems

Abstract

This paper presents a mobility-adaptive Slotted ALOHA (MA-SA) protocol designed for vehicular ad-hoc networks (VANETs) with dynamic topologies. Current MAC protocols for vehicular communications often suffer from decreased performance in high-mobility scenarios due to their inability to adapt to rapidly changing network conditions. We propose a novel approach that dynamically adjusts transmission parameters based on real-time mobility metrics. Our protocol incorporates a spatiotemporal correlation model that predicts vehicle movement patterns to optimize slot allocation. Through extensive simulations and a small-scale field trial, we demonstrate that MA-SA achieves up to 37% higher throughput and 42% lower packet collision rates compared to traditional Slotted ALOHA implementations under high-mobility conditions (120-150 km/h). Performance improvements are particularly significant in scenarios with heterogeneous vehicle speeds and dense traffic conditions. The protocol exhibits graceful degradation in extremely congested networks where relative mobility exceeds predictive capabilities. We provide a comprehensive mathematical framework for mobility prediction and slot allocation, including closed-form expressions for optimal backoff parameters as functions of vehicle density and relative speed. Our findings suggest that mobility-aware MAC protocols represent a promising direction for improving the reliability of safety-critical applications in intelligent transportation systems.