Time-predictable End-system Design for Real-Time Communication

Over the years, computing systems have not only increased their processing power but have also increased the total number of interconnected nodes. Nowadays, most computing systems found in industrial, automotive and aerospace application domains are distributed cyber-physical systems comprised of a plethora of networked platforms. Thus it is becoming a challenge to guarantee both timepredictable task execution and bounded end-to-end communication latency. To this end, different techniques are employed on the network and the processor. On the network, different protocols have been developed to achieve deterministic and temporally isolated communication. While on the processor, timepredictable execution can be guaranteed by employing different scheduling policies combined with static worst-case execution time analysis. This thesis explores the software and hardware solutions that extend an embedded system with mechanisms to provide precise and fault-tolerant clock synchronization, minimal end-to-end communication latency and synchronous task execution. These solutions potentially increase the system’s time-predictability and create an overall reliable time-triggered computing platform for safety-critical system research. Firstly, time-synchronization is established by exploring the IEEE 1588 Precise Time Protocol and developing a hardware unit. The design is experimentally verified and achieves nanosecond clock synchronization. The safety and security properties of the IEEE 1588 protocol are analyzed, and a fault-tolerant prototype design is proposed. The design enables reliable synchronization in
time-sensitive networking communication systems. The design is evaluated in simulation using synthetic benchmarks that demonstrate the design’s capability to tolerate multiple network failures and denial-of-service attacks Next, the time-triggered communication protocol TTEthernet is explored, and a time-analyzable network stack is presented. The design allows an embedded
platform to communicate and synchronize its time over TTEthernet networks. Based on the developed network stack, synchronization of real-time tasks with an underlying time-triggered communication layer is explored. An open-source
framework is presented for scheduling and executing synchronous distributed tasks. The framework is evaluated experimentally using a multi-rate synthetic application. The evaluation demonstrates minimal end-to-end communication latency as well as distributed task synchronization with minimal jitter. Finally, the evaluation is extended with an avionic benchmark application. The benchmark presents a longitudinal flight controller case study that is successfully distributed and scheduled using the proposed time-triggered framework. The benchmark is implemented in an experimental TTEthernet network with three nodes and successfully executes a flight scenario.