Analyzing Throughput and Delay Characteristics of Slotted ALOHA in Vehicular Networks Under Varying Traffic Conditions

Abstract

The proliferation of vehicular networks necessitates robust medium access control protocols capable of handling dynamic traffic loads and stringent delay constraints. This paper presents a rigorous analytical framework for evaluating the throughput and delay characteristics of Slotted ALOHA in vehicular environments, explicitly accounting for time-varying vehicle density, channel fading, and stochastic packet arrival patterns. By modeling the spatial distribution of vehicles as a non-homogeneous Poisson point process and incorporating Nakagami-$m$ fading channels, we derive closed-form expressions for steady-state throughput and end-to-end delay using a combination of stochastic geometry, Markov chain analysis, and queuing theory. The capture effect and interference statistics are characterized through moment-generating functions, enabling precise quantification of successful transmission probabilities under co-channel interference. Numerical results reveal that the maximum achievable throughput decays exponentially with increasing vehicle density beyond a critical threshold, while delay exhibits phase transitions from stable to unstable regimes as the arrival rate surpasses network capacity. Practical operational boundaries are identified, demonstrating that traditional Slotted ALOHA becomes inefficient at vehicle densities exceeding 0.25 transmitters per slot per coverage area. Fundamental limitations arise from the protocol’s inability to adapt to rapid topology changes and its susceptibility to cascading collisions under bursty traffic, particularly in urban scenarios with hidden terminals. These findings provide critical insights for designing enhanced random access schemes in next-generation vehicular communication systems.