Slot Allocation Schemes for the FlexRay Static Segment

In recent years, the FlexRay communication protocol has been promoted as a de facto standard for in-vehicular communications. In the FlexRay protocol, the communication timeline is organized as a sequence of four segments, whereas the static segment defines a set of slots specifically designed for the transmission of synchronous messages. In this paper, we investigate the following problem: "how to allocate a minimum number of static slots to each FlexRay node, while guaranteeing that all synchronous messages will be transmitted before their deadlines". Unlike previous studies that use linear programming based techniques, we evaluate the number of allocated slots using traditional response time analysis (RTA) techniques. The use of RTA techniques allows us to consider the timing requirements imposed by the set of synchronous message streams. Unlike other approaches, the RTA-based technique proposed in this paper is able to deal with a) message stream sets where periods are not multiple of the FlexRay cycle duration and b) the generation of messages at the application layer that are not synchronized with the FlexRay cycle. The proposed allocation schemes may be integrated into an AUTOSAR environment as an RT-Middleware, allowing FlexRay real implementations to take full advantage of the proposed schemes.