A Secure, Delay-Aware, and Environment-Adaptive TDMA-Based Multi-Hop Safety Framework for VANETs

Abstract

Vehicular Ad Hoc Networks (VANETs) have emerged as a key enabler for intelligent transportation systems by supporting real-time exchange of safety-critical information among vehicles. However, reliable, and low-latency dissemination of emergency messages remains a major challenge in highly dynamic and adverse environments, particularly under fog conditions where both driver visibility and wireless signal propagation are severely degraded. This paper presents a comprehensive framework for environment-aware, delay-optimized, and secure dissemination of event-driven safety messages in VANETs. The work focuses on minimizing broadcast channel delay during sudden braking events, enabling early warning dissemination for accident prevention, and supporting long-distance multi-hop propagation of safety messages. The proposed solution integrates a Fog-Aware TDMA-based broadcast mechanism with priority-driven scheduling to replace contention-based CSMA/CA access, thereby ensuring deterministic channel access and bounded latency. An event-driven architecture is designed to generate and prioritize Emergency Brake and Early Warning Messages, which are disseminated through intelligent multi-hop forwarding strategies that adapt to vehicle density, mobility, and fog-induced signal attenuation. A detailed system model, mathematical formulation, and algorithmic design are developed to capture vehicular dynamics, fog-aware channel Behavior, TDMA slot allocation, and end-to-end delay optimization. The framework is implemented and evaluated using an integrated NS-3 and SUMO simulation environment under varying traffic densities and fog intensities. Extensive results demonstrate significant improvements over conventional approaches in terms of end-to-end delay, packet delivery ratio, collision reduction, broadcast coverage time, and hop efficiency, consistently meeting the 100 ms safety requirement for time-critical applications.  Overall, this delivers an integrated, adaptive, and secure VANET communication framework that enhances road safety by ensuring timely and reliable dissemination of emergency messages in challenging environments. The proposed approach provides a strong foundation for future environment-aware MAC and routing protocols in next-generation intelligent transportation systems.