Kooperative Peer-to-Peer-basierte Verkehrsinformationssysteme

This thesis deals with cooperative traffic information systems, which support the driver of a car in selecting a route, based on traffic information collected by other cars. System participants contribute measurements of the traffic situation in their vicinity (e. g., current traffic flow speed) and use the measurements made by other drivers to find the fastest route to their destination with regard to the current conditions. Such systems help avoid traffic jams, highly congested roads, place of accidents and other unexpected deterioration. The communication pattern of the discussed application is quite challenging: continuously updated data (i. e., description of the current traffic conditions) are to be made available to multiple participants spread over relatively large geographical areas. Cooperative traffic information systems have primarily been discussed in the context of direct, ad-hoc communication between cars. We formally show in this thesis that a very special communication properties of the discussed application do not fit into the constrained capacity offered by mobile ad-hoc networks. Consequently, this work proposes an alternative design, based on a peer-to-peer paradigm and cellular networks, to efficiently distribute traffic information. Since the data maintained in a cooperative traffic information system have a very specific structure, it is particularly profitable—in terms of bandwidth consumption and latency— to tailor the system to this specific application domain instead of re-using generic peer-topeer approaches. In our work we shall point out the limitations of generic P2P networks when it comes to the exchange of dynamic traffic related data. Then we will present Peerto-Peer-based cooperative Traffic Information System: PeerTIS. That is an adjusted generic peer-to-peer overlay, which accounts for the special properties of the discussed application. In addition to a detailed description of such adjustments, we will also provide evaluation showing the technical feasibility of the peer-to-peer-based traffic information system. Although PeerTIS is a step forward towards an efficient implementation of a working intervehicular application, it still possesses some limitations. In particular, the unfair load distribution among the participants of PeerTIS might undermine the idea of cooperative sys-