Fairness and Stability Analysis of Congestion Control Schemes in Vehicular Ad-hoc Networks

TL;DR

This paper analyzes the stability and fairness of congestion control algorithms in vehicular ad-hoc networks, highlighting trade-offs and proposing solutions to unfairness issues through simulation-based evaluation.

Contribution

It provides stability conditions, evaluates fairness and stability of algorithms, and introduces a method to resolve unfairness in congestion control for vehicular networks.

Findings

Stability verified across various road densities.

Fairness naturally achieved by some algorithms.

A method to mitigate unfairness improves performance.

Abstract

Cooperative vehicle safety (CVS) systems operate based on broadcast of vehicle position and safety information to neighboring cars. The communication medium of CVS is a vehicular ad-hoc network. One of the main challenges in large scale deployment of CVS systems is the issue of scalability. To address the scalability problem, several congestion control methods have been proposed and are currently under field study. These algorithms adapt transmission rate and power based on network measures such as channel busy ratio. We examine two such algorithms and study their dynamic behavior in time and space to evaluate stability (in time) and fairness (in space) properties of these algorithms. We present stability conditions and evaluate stability and fairness of the algorithms through simulation experiments. Results show that there is a trade-off between fast convergence, temporal stability and spatial fairness. The proper ranges of parameters for achieving stability are presented for the discussed algorithms. Stability is verified for all typical road density cases. Fairness is shown to be naturally achieved for some algorithms, while under the same conditions other algorithms may suffer from unfairness issues. A method for resolving unfairness is introduced and evaluated through simulations.