Physical Carrier Sense in Vehicular Ad-Hoc Networks

Enhancing road safety using vehicle-to-vehicle communication has become an important goal for the automotive industry. A lot of effort has been put in the design of an efficient medium access control protocol, capable to function correctly even under heavy congestion. The solutions proposed so far focus on data rate or transmission power control. In this paper, we argue that the most important parameter for congestion control in vehicular ad hoc networks is the carrier sense threshold. We support this theory with analytical and simulation results and we demonstrate that the optimal threshold depends on the vehicular density. Furthermore, we propose an adaptive mechanism for physical carrier sense control and analyse its performance, showing an important increase in message reception probability.