Real-time server-based communication with CAN

This paper investigates the concept of share-driven scheduling of networks using servers with real-time properties. Share-driven scheduling provides fairness and bandwidth isolation between predictable as well as unpredictable streams of messages on the network. The need for this kind of scheduled real-time communication network is high in applications that have requirements on flexibility, both during development for assigning communication bandwidth to different applications, and during run-time to facilitate dynamic addition and removal of system components. We illustrate the share-driven scheduling concept by applying it to the popular controller area network (CAN). We propose a scheduling mechanism that we call simple server-scheduled CAN (S-3-CAN), for which we also present an associated timing analysis. Additionally, we present a variant of S'-CAN called periodic server-scheduled CAN (PS2-CAN), which for some network configurations gives lower worst-case response-times than S-3-CAN. Also for this improvement, a timing analysis is presented. Moreover, we use simulation to evaluate the timing performance of both S-3-CAN and PS2-CAN, comparing them with other scheduling mechanisms.