Broadcast reception rates and effects of priority access in 802.11-based vehicular ad-hoc networks

TLDR

VANETs primarily support vehicle safety applications, where broadcasts dominate in large‑scale deployments. The study seeks to quantify broadcast reception probability versus distance, evaluate priority access for urgent warnings, and assess how fading affects these outcomes. Simulations evaluate reception probabilities under two‑ray‑ground and Nakagami fading models in saturated environments, while IEEE 802.11e EDCA mechanisms are used to reduce channel access times and enhance reception rates. Priority access improves reception under the two‑ray‑ground model and also under Nakagami fading, though overall probabilities are lower; the work emphasizes that designing repetition or multi‑hop retransmission strategies is essential for safety‑critical applications.

Abstract

One key usage of VANET is to support vehicle safety applications. This use case is characterized by the prominence of broadcasts in scaled settings. In this context, we try to answer the following questions: i) what is the probability of reception of a broadcast message by another car depending on its distance to the sender, ii) how to give priority access and an improved reception rate for important warnings, e.g., sent out in an emergency situation, and iii) how are the above two results affected by signal strength fluctuations caused by radio channel fading? We quantify via simulation the probability of reception for the two-ray-ground propagation model as well as for the Nakagami distribution in saturated environments. By making use of some IEEE 802.11e EDCA mechanisms for priority access, we do not only quantify how channel access times can be reduced but also demonstrate how improved reception rates can be achieved. Our results show that the mechanisms for priority access are successful under the two-way-ground model. However, with a non-deterministic radio propagation model like Nakagami's distribution the benefit is still obvious but the general level of probability of reception is much smaller compared to two-ray-ground model. The results indicate that -- particularly for safety-critical and sensor network type of applications -- the proper design of repetition or multi-hop retransmission strategies represents an important aspect of future work for robustness and network stability of vehicular ad hoc networks.