Deterministic Ethernet for Automotive Applications
While Automotive Ethernet is mostly used for diagnostics and data download today, new applications such as camera-vision systems and infotainment systems are emerging. In addition, there is a huge potential for Ethernet to also become the backbone network solution throughout the vehicle. This, in particular includes safety-related and safety-critical applications to enable piloted and autonomous driving which is a current major trend in automotive industry. To enable this, one possible evolution of Ethernet is Deterministic Ethernet.
While Ethernet provides Quality-of-Service (QoS), Deterministic Ethernet adds Guarantee-of-Service (GoS) in a sense that the communication service is guaranteed and robust even in presence of faulty components or after transient disturbances (like disturbances induced by electromagnetic interference). Furthermore, Deterministic Ethernet enables full control of the transmission and forwarding timing of selected Ethernet frames, typically frames for the highest critical applications. This control is achieved by the implementation of a system-wide clock synchronization protocol and pre-planning communication events for critical traffic.
Deterministic Ethernet solutions are available today for example from TTTech. TTTech’s version supports several standards including standard Ethernet (IEEE 802.3), Time-Triggered Ethernet (SAE AS6802) as well as AVB (Audio/Video Bridging) and the evolving TSN (Time Sensitive Networking). In particular the SAE AS6802 part of the solution has been developed to ensure correct clock-synchronization even in the presence of arbitrary single failures and to support standards such as DO 178, DO 254 and ISO 26262. The solution provides highest dependability properties and thanks to these it was also chosen as the on-board avionics network in the next generation of manned spacecraft Orion. Thus it can be said that using Deterministic Ethernet technology in the car provides basically a degree of astronaut safety for automotive passengers as well. Audi has already chosen Deterministic Ethernet for its next generation automated driving platform. To guarantee cost-effective Deterministic Ethernet solutions for the automotive market, NXP currently finalizes together with TTTech a first ASIC version of an automotive switch for Deterministic Ethernet.
Standardization of Automotive Ethernet is a key enabler to ensure interoperability of products from different vendors. Therefore some important elements of Deterministic Ethernet are the standards developed in the IEEE 802.1 and IEEE 802.3 working groups. The AVB standards and the ongoing TSN standards developed in the IEEE 802.1 and the automotive physical layer standards 100BASE-T1 and 1000BASE-T1 are of particular relevance.
AVB has enhanced Ethernet with first real-time capabilities. It is now possible to reserve bandwidth in the switches along a path through a network and end-to-end communication latencies can be calculated, provided the end systems also implement the AVB standards. Furthermore, AVB has also standardized IEEE 802.1AS, a clock synchronization protocol similar to IEEE 1588, which allows the nodes in the network to synchronize their local clocks. With TSN, the IEEE 802.1 standards further develop Ethernet’s real-time capabilities by standardizing a time-triggered communication as well as Ethernet frame preemption.
Other functionality that is currently being developed within the TSN working group covers the configuration of redundant paths in a network as well as the redundancy management of the frames that are being sent along these redundant paths. The AVB clock synchronization protocol itself is currently also being improved towards provision of multiple synchronized time bases as well as towards fault-tolerance.
The standardization of these elements will greatly contribute to the success of Deterministic Ethernet in the automotive industry.
About the author:
Wilfried Steiner is Corporate Scientist at TTTech Computertechnik AG and Leader of the research team TTTech Labs. He holds a degree of Doctor of Technical Sciences from the Vienna University of Technology, Austria. His research is focused on the development of algorithms and services that enable dependable communication in cyber-physical systems and applied formal methods.
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