Efficient handling of sporadic messages in FlexRay

Abstract

FlexRay is a high-bandwidth protocol that supports hard-deadline periodic and sporadic traffic in modern in-vehicle communication networks. The dynamic segment of FlexRay is used for transmitting hard deadline sporadic messages. In this paper, we describe an algorithm to minimize the duration of the dynamic segment in a FlexRay cycle, yielding better results than existing algorithms in the literature. The proposed algorithm consists of two phases. In the first phase, we assume that a sporadic message instance contends for service with only one instance of each higher-priority message. The lower bound provided by the first phase serves as the initial guess for the number of mini-slots used in the second phase, where an exact scheduling analysis is performed. In the second phase, a sporadic message may contend for service with multiple instances of each higher-priority message. This two-phase approach is efficient because the first phase has low overhead and its estimate greatly reduces the number of iterations needed in the second phase. We conducted experiments using the dataset provided in the literature as well as the SAE benchmark dataset. The experimental results demonstrate superior bandwidth minimization and computational efficiency compared to other algorithms.