Abstract

This thesis reviews approaches towards Cooperative Adaptive Cruise Control (CACC), identifies important simulation parameters, and analyzes their correlation with metrics that describe the performance of the application in terms of safety, efficiency and channel utilization. This is achieved through simulation of realistic traffic and V2V communication by using recent ETSI ITS standards including different GeoNetworking message dissemination mechanisms. The results show, that an increasing traffic on the network channel has a negative effect on the safety of a platooning application, but it can be compensated by using more conservative configuration parameters. This impact is increasing slightly for lower vehicle spacing, stronger for longer platoons and drastically for lower beacon rates.

Abstract

Road throughput can be increased by driving at small inter-vehicle time gaps. The amplification of velocity disturbances in upstream direction, however, poses limitations to the minimum feasible time gap. This effect is covered by the notion of string stability. String-stable behavior is thus considered an essential requirement for the design of automatic distance control systems, which are needed to allow for safe driving at time gaps well below 1 s. Using wireless inter-vehicle communications to provide real-time information of the preceding vehicle, in addition to the information obtained by common Adaptive Cruise Control (ACC) sensors, appears to significantly decrease the feasible time gap, which is shown by practical experiments with a test fleet consisting of six passenger vehicles. The large-scale deployment of this system, known as Cooperative ACC (CACC), however, poses challenges with respect to the reliability of the wireless communication system. A solution for this scalability problem can be found in decreasing the transmission power and/or beaconing rate, or adapting the communications protocol. Although the main CACC objective is to increase road throughput, the first commercial application of CACC is foreseen to be in truck platooning, since short distance following is expected to yield significant fuel savings in this case.