A Density-Based Congestion Avoidance Protocol for Strict Beaconing Requirements in VANETs

Accident prevention in roads and highways is one of the most important aspects of vehicular networks. In a Vehicular Ad Hoc Network (VANET), vehicles are equipped with a device that enables wireless communication between them. In VANETs, vehicles usually build network topology by periodic exchange of messages known as beacons. These messages should include the vehicle's position, speed and heading. Safety applications in VANETs define strict requirements to guarantee their proper functionality, among them, beacon transmission rates that can vary between 10 to 50 Hz. However, high beacon transmission rates can lead to a problem known as broadcast storm, which may impair correct operation of safety applications in high vehicle density scenarios. During a broadcast storm, numerous messages are transmitted simultaneously, which increases collisions and decreases packet delivery ratio. In this work, we propose a Density-based Congestion Avoidance Protocol (DCAP) to adapt beacon transmission rate in VANETs and minimize broadcast storm occurrence. Experimental results show that even in high vehicle density scenarios, DCAP improves on other protocols by 8% and 50% regarding packet delivery ratio, while still assuring coverage of approximately 100%.