Preventing unfairness in the ETSI distributed congestion control

The European Telecommunications Standards Institute (ETSI) framework imposes requirements on the exchange of periodic safety messages between components of intelligent transportation systems. First and foremost among these is the fair allocation of, and access to, wireless channels. The decentralized congestion control (DCC) algorithm has been standardized by ETSI to this end. However, DCC has a serious fairness problem, i.e., the beacon throughput can diverge by a factor of 100 or more, even among vehicles that are close together. In this letter, we demonstrate how the fairness problem manifests itself and propose a remedy so that DCC satisfies the fairness requirement.