Reliability Evaluation of Broadcast Protocols for FlexRay

Abstract

X-by-wire applications have extremely demanding reliability requirements that are increasingly being addressed through the adoption of distributed and fault-tolerant architectures. The development of these applications is facilitated by the availability of high level services such as agreement or reliable broadcast. Some dependable communication buses, e.g. TTP-C, already provide these services, whereas FlexRay does not.In this paper we present an approach to evaluate the reliability of a family of reliable broadcast protocols implemented both on top of FlexRay and on top of ordinary TDMA. In particular, we evaluate the impact of the acknowledgment policy on the reliability of these protocols. We express the reliability as the probability of violation of the agreement and validity properties of the protocol during a mission. For that, we develop an analytical model based on Discrete Time Markov Chains (DTMC) that considers a comprehensive set of faults (permanent, transient, omissive and asymmetric) affecting both nodes and channels, and their effects on the protocol execution. The structure of the model is quite flexible and easily adaptable to other TDMAbased protocols. In order to assess the sensitivity of the protocol to both internal and external factors, we carried out a large number of experiments considering several network configurations and fault rates. The results show that for FlexRay, the negative acknowledgment policy provides the same reliability as the positive acknowledgment policy. However, for TDMA-based protocols that lack FlexRay's ability to distinguish silence from the loss of a message, the negative acknowledgment policy leads to a lower reliability and its fitness for safety critical applications depends on the system configuration and environment conditions.

Multi-Variant Scheduling of Critical Time-Triggered Communication in Incremental Development Process: Application to FlexRay

“…They present a two-stage scheduling algorithm; in the first stage, the signals are packed into the frames and in the second, the schedule is created by a frame scheduling algorithm. The reliability of the broadcast FlexRay communication was studied by Souto et al [19].…”

Research of Message Scheduling for In-Vehicle FlexRay Network Static Segment Based on Next Fit Decreasing (NFD) Algorithm

“…They are static segment (ST), dynamic segment (DS), symbol window (SW), and network idle time (NIT). Among them, static segment transmits periodic messages using time division multiple access (TDMA) technology and suitable for high-confidence and security-critical communications [5][6][7]. The FlexRay static segment consists of multiple time slots with the same size.…”

“…Set l cur = l cur + 1 and repeat steps (4) and (5), loop until l cur = l H . (7). Take the maximum value of U when the corresponding message set and its corresponding frame payload length l best .…”

Reliability-based parameter design for FlexRay network in vehicles

“…Jovic et al 17 proposed a solution for testing the FlexRay bus communication, which can detect the errors in processing FlexRay information transmission among multiple ECUs. Do Souto et al 18 presented an approach to evaluating the reliability of FlexRay and time-division multiple access (TDMA) buses, such as reliable broadcast (RB). Chen and Leu 19 proposed a twolevel redundancy approach for a safety-critical FlexRay bus, which can use backup nodes, mirror tasks, and task migration to maintain a system operation when an ECU fails.…”