Controller Area Network (CAN): Response time analysis with offsets

Abstract

Desynchronizing streams of frames through the means of offsets has today become common practice in automotive CAN networks. This is because this traffic shaping strategy is very beneficial in terms of reducing response times especially at high load levels. However, to the best of our knowledge, there is no result available in the literature that allows the response times of frames with offsets to be calculated for CAN. In this paper, we address this shortcoming of existing CAN schedulability analysis, and propose an extendible framework built upon the transaction model to derive worst-case response times (WCRT) on CAN. As will be shown in the experiments performed on realistic automotive networks, explicitly integrating offsets in the analysis permits a much tighter WCRT evaluation than with the classical synchronous analysis, which ultimately enables the designer to reduce resource over-provisioning.