Quality of Service in Fahrzeug-Fahrzeug-Netzen - dezentrale und schichtübergreifende Steuerung des Nachrichtenaufkommens
FacultiesFakultät für Ingenieurwissenschaften und Informatik
Co-operative vehicular safety systems (CVSS) are promising applications for future intelligent transportation systems. A co-operation between vehicles can be established, if information on the situation on and besides the road is distributed among the traffic participants. Therefore safety applications have stringent Quality of Service (QoS) requirements on the used information dissemination method. Most dissemination methods in Vehicular Ad Hoc Networks are based on broadcast messages. The broadcast pattern degrades the intended Medium Access Control mechanism of the IEEE 802.11p standard to a p-slotted CSMA. This leads to packet collisions and a decrease in message reception probability, as hidden terminals and synchronous transmissions cannot be prevented. Therefore a minimal effective throughput cannot be provided to co-operative safety system applications. This dissertation develops a decentralized Traffic Engineering concept to provide a minimum amount of effective throughput for CVSS. The main idea is the decentralized control of each single transmission with respect to the expected amount of traffic within the collision domain of each network node. This is realized using a cross-layer architecture to combine the aspects of single broadcasts and multi-hop data dissemination. As main requirement an algorithm is presented that estimates the number of necessary rebroadcasts of a message to ensure a reliable dissemination within a node’s collision domain. The main result using the presented QoS methods is a reduced and controlled overall number of transmitted broadcast messages with respect to a low collision probability. Thus the information dissemination is most effective as no further rebroadcasts are necessary to ensure reliability. As a second result the QoS mechanism has the ability to prioritize and limit resources of the applications. This ability enables to guarantee a minimal amount of resources and highest QoS for the important safety applications.
Subject HeadingsCar-to-Car-Kommunikation [GND]
Traffic engineering [LCSH]
Information dissemination [MeSH]