An adaptive strategy to mitigate instability in the ETSI DCC: Experimental validation

Cooperative Intelligent Transport System (C-ITS) applications need a continuous exchange of information between road users and roadside infrastructures. In this regard European Telecommunications Standards Institute (ETSI) has standardized the Cooperative Awareness Basic Service where status messages named Cooperative Awareness Messages (CAMs) are constructed, managed and processed. With the regular exchange of CAM messages, vehicles and roadside units are constantly informed about each others position, dynamics and attributes. Due to this massive dissemination of messages, without properly congestion control, the functionality of both safety and traffic-management C-ITS applications can be compromised. In this paper we consider the ETSI Decentralized Congestion Control (DCC) mechanism and propose a new approach to cope with relative oscillation and unfairness problems. In the proposed solution vehicles adapt their behaviour and DCC decisions according to the surrounding road traffic conditions. DCC functionality and the presented solution have been then validated through an experimental, ITS G5-compliant testbed consisting of real world devices. The obtained results show an improvement in DCC performances, evaluated in terms of machine status and Channel Busy Ratio (CBR) oscillations.