A Method for Scheduling Receiver Tasks Based on Maximum Allowed Execution Time Dichotomy Search

摘要

In designing and developing navigation receiver embedded software, the correct scheduling of navigation tasks is critical for ensuring that a receiver works in the right way. If a receiver's timing scheduling becomes abnormal, it may lead to timing conflicts of the multi-tasking navigation receiver, which may seriously influence the system's performance of real-time features and functionalities. This paper models the timing scheduling of navigation receivers by extracting all important timing parameters including the execution time, period, deadline and priority etc., and focusing on the execution time. The maximum execution time of a navigation task relies on the design and implementation algorithms and the computing capability of the processor. The execution time parameter can be properly adjusted in receiver software design or even in the phase of the receiver requirement changes. On the other hand, the other parameters (i.e., the period, deadline and priority) mainly depend on the receiver's technical requirements, and usually these parameters are set to constant values. In this research, a novel off-line method based on the maximum allowed execution time dichotomy optimization is proposed, and the equilibrium rule is proposed to apply to the multi-task maximum allowed execution time dichotomy search and an analysis of time series of those parameters obtained from real observations of receiver tasks was also conducted. Results indicate that the relative equilibrium is more suitable to the multi-task scheduling of receiver navigation, compared to the absolute equilibrium. The proposed method provides a fast off-line scheduling approach for the top level task design of navigation receivers, and remarkably improves the development efficiency of receiver embedded software.