papers

PhD Thesis, Fernuniversität Hagen

Investigations into the usage of Ethernet in automo- biles is in progress in academia, the car industry and companies producing automotive electronic devices. The interest in Ethernet is motivated by the high bandwidth and scalability provided. It is a well experienced technology with support for the Internet Protocol (IP) suite. Ethernet as in-car network is expected to breakthrough in Advanced Driver Assistance Systems (ADAS) involving cameras and in the multimedia domain. Both the IEEE Audio Video Bridging (AVB) standard and Time-Triggered Ethernet (TTE) are promising candidates. This paper presents a simulation study aimed to investigate the behavior of these technologies when supporting ADAS and multimedia traffic on star-based networks under varying workload. The performance under different operating conditions is presented and discussed.

Real-time Ethernet is expected to become the core technology of future in-car communication networks. Following its current adoption in subsystems for info- and entertainment, broadband Ethernet promises new features in the core of up- coming car series. Its full potential will enfold when deploying Ethernet-based backbones that consolidate all automotive domains on a single physical layer at increased bandwidth but reduced complexity and cost. In such a backbone, traffic with a variety of real-time requirements and best-effort characteristics will share the same physical infrastructure. However, certain applications like online diagnosis, data- or firmware updates, and access to off-board backends will introduce bursty high traffic loads to the sensitive core of the cars communication network. In this work, we analyze the robustness against cross-traffic of real-time Ethernet protocols. Based on a realistic in-car scenario, we demonstrate that background cross-traffic can have significant impact on in-car backbone networks—even for real-time protocols with strict prioritization. By comparing the real-time approaches Ethernet AVBs asynchronous credit based shaping with the time-triggered and rate-constrained traffic classes of Time-triggered Ethernet (AS6802) we quantify how different media access policies suffer from low priority bursts of applications such as diagnosis, online updates or backend-based services. Our simulation study of a realistic in-car backbone design and traffic model reveals that in a realistic in-car network design, cross-traffic may increase end-to-end latency by more than 500% while the jitter can become 14 times higher than for a network without background tasks. We discuss ways to mitigate these degrading effects.