Near-optimal Broadcast Scheduling of Dynamic Map in Cooperative Intelligent Transport Systems

Cooperative intelligent transport systems (C-ITS) enable fast communication among vehicles, infrastructure, and other road users. Via C-ITS, vehicles can acquire the real-time traffic information from various C-ITS stations, especially the information of the highly dynamic data in the local dynamic map (LDM). In the paper, we consider the message broadcast from the trustworthy roadside unit (RSU) to vehicles, where the messages have different popularity levels (i.e., how many vehicles request for this message), generation time of last-received corresponding messages, and priority towards each vehicle. Besides, the freshness of information of messages needs to be as fresh as possible. To explore the non-trivial order of transmission in time under the limited bandwidth, we formulate an optimization problem named ROAD to find an efficient transmission schedule and propose an approximation algorithm termed ABS. Experiment results manifest that ABS outperforms traditional approaches by 40%.