Scheduling of Dynamic Participants in Real-Time Distributed Systems

Access to shared resources can be controlled by schedules or mutual exclusion. Such methods are not practical in an environment with dynamic participants, where nodes requiring access to shared resources can enter or leave the scene at any time. Current scheduling methods are usually centralized, demand that the system has a clear idea of when the resources are required and do not consider communication failures. Current implementations of distributed mutual exclusion use token- or permission-based methods. Dynamic participation amplifies the lost token problem in token-based approaches, while limited knowledge of the number of nodes makes obtaining quora and consensus in permission-based approaches impossible, rendering both mutual exclusion implementations impractical. This paper presents the CwoRIS protocol which enables short-term scheduling in real-time within an environment with dynamic participants. It motivates the need to support dynamic participants by means of a scenario for autonomous vehicle coordination in intersection crossing. The paper shows that the protocol is able to work in an environment with message loss and argues its correctness by showing mutual exclusion: there are no cases in which two nodes have access to the same resources at the same time.