Conventional Traffic and Travel Information (TTI) systems are based on a centralized structure: Sensors deployed at the roadside monitor the traffic and transmit the results to a central unit, which performs a situation analysis. TTI is made available to the drivers via broadcast service (e.g. TMC/RDS) or on demand via cellular phone. In contrast to this centralized approach, a decentralized, Self-Organizing Traffic Information System (SOTIS) based on Inter-Vehicle Communication (IVC) has many advantages: It requires no expensive infrastructure, can provide detailed information for the focal area with low delay and is available everywhere. In such an IVC based decentralized system, TTI is sensed by each individual vehicle. The information is analyzed, combined with TTI received from other vehicles and the results are distributed using recurring broadcast packets. In this paper, an adaptive broadcast scheme for efficient TTI distribution called Provoked Broadcast is presented. The algorithm favors the propagation of significant TTI changes within the self-organizing network. Nodes adapt their communication behavior to the local environment and avoid redundant transmissions. The performance of the proposed scheme is evaluated by using simulations of typical traffic scenarios. Compared to a strictly periodic broadcast, the new scheme decreases the average error of information available at an individual vehicle and still requires significantly less bandwidth.
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