Serviceorientiertes Mehrkanal-Beaconing in Fahrzeug-Ad-hoc-Netzen

The interconnection of vehicles is an important topic concerning the enhancement of traffic safety and traffic efficiency. Therefore, vehicles exchange position and state information with each other to establish an awareness level for the calculation of collision probabilities with their neighbors. To recognize critical safety situations it is essential to receive information reliably. However, these systems are typically based on wireless ad-hoc networks that cannot guarantee reliable packet transmission. This is especially the case in situations where a high number of communication nodes exist. The aim of this work at hand is the definition of a beaconing algorithm that enables the establishment of a desired awareness level for critical safety situations especially in high density traffic scenarios. First, representative scenarios for collision detection and collision avoidance were specified and metrics for the evaluation of the beaconing algorithms were defined. Based on these metrics the performance of beaconing algorithms with different static periodical update rates was evaluated. It is presented that these kinds of beaconing algorithms cannot provide sufficient results with respect to the required constant information throughput in high density traffic situations. To provide a high awareness level for each vehicle in its individual situation in spite of an unreliable communication channel a service-oriented beaconing approach is defined in this work. It is based on a request/response communication scheme to compensate particular packet loss. Hereby, a broadcast and a unicast occurrence of the algorithm are defined accordingly to the corresponding representative scenarios. It is presented that the service-oriented beaconing approach provides a significant benefit with respect to the information throughput for low and middle traffic density situations. However, in high density situations the benefit of this approach is decreasing due to the increased communication overhead. This is a result of using one single communication channel. To achieve a high awareness level also in high density traffic situations, a significant modification was defined. Therefore, the usage of multiple communication channels was introduced to distribute the communication load over several channels. It is specified to send all service responses on a dedicated service channel to reduce the load on the control channel where the service requests are transmitted. After an extensive evaluation of the multi-channel utilization in vehicle ad-hoc networks using IEEE 802.11p it is shown that the multi-channel version of the service-oriented beaconing approach can achieve significant benefits concerning the information throughput for the collision detection and collision avoidance scenarios even in high density traffic situations.