Scheduling in Real-Time Mobile Systems

To guarantee the safety and security of a real-time mobile system such as an intelligent transportation system, it is necessary to model and analyze its behaviors prior to actual development. In particular, the mobile objects in such systems must be isolated from each other so that they do not collide with each other. Since isolation means two or more mobile objects must not be located in the same place at the same time, a scheduling policy is required to control and coordinate the movement of such objects. However, traditional scheduling theories are based on task scheduling which is coarse-grained and cannot be directly used for fine-grained isolation controls. In this article, we first propose a fine-grained event-based formal model called a time dependency structure and use it to model and analyze real-time mobile systems. Next, an event-based schedule is defined and the composition of schedules is discussed. Then, we investigate the schedulability of isolation-that is, checking whether a given schedule ensures the isolation relationship among mobile objects or not. After that, we present an automation approach for scheduling generation to guarantee isolation controls in real-time mobile systems. Finally, case studies and simulation experiments demonstrate the usability and effectiveness of our approach.