Till Steinbach

Tomorrow's In-Car Interconnect? A Competitive Evaluation of IEEE 802.1 AVB and Time-Triggered Ethernet (AS6802)

Ethernet-based in-car communication is currently a hot topic in the automotive industry. Soon Ethernet will start to oust MOST bus in its domain of info- and entertainment applications. However, the full benefit of a technologically integrated in-car network will only become rewarding with the deployment of an Ethernet-based backbone that integrates all automotive domains on a single layer at increased bandwidth, reduced complexity and cost, while opening car intelligence for future innovations. Such backbone must transport critical control data in real-time. Standard Ethernet requires extensions to comply with the strict timing requirements of driver assistance and safety applications while simultaneously supporting broadband multimedia traffic. In this paper, we compare IEEE 802.1 AVB and Time-triggered Ethernet, two competing real-time approaches. While the first fosters over- provisioning and prioritisation, the second is based on a coordinated time-division-multiple-access (TDMA) policy for media access. By simulating a realistic in-car backbone design and traffic model, we reveal the strengths and weaknesses of both protocols and point to the diverging characteristics of event- and time-triggered policies. Our results show that in this in-car network scenario both protocols are able to meet the rigid timing requirements, while each has its unique benefits and disadvantages.

Comparing time-triggered Ethernet with FlexRay: An evaluation of competing approaches to real-time for in-vehicle networks

FlexRay is considered the next generation state-of-the-art technology for in-car networks, while time-triggered Ethernet emerges with the promise to integrate real-time and best-effort traffic into one homogeneous backbone. This paper contributes a competitive analysis of FlexRay and time-triggered Ethernet. By showing that it is possible to transfer a fully utilized FlexRay system to a system based on time-triggered Ethernet, it is demonstrated that time-triggered Ethernet is a suitable replacement of current in-vehicle bus-systems. Further it is shown that a switched system has advantages in bandwidth utilization over a shared bus, when using group communication.

Extending IEEE 802.1 AVB with time-triggered scheduling: A simulation study of the coexistence of synchronous and asynchronous traffic

In-car networks based on Ethernet are expected to be the first choice for future applications in the domain of info-and entertainment. However, the full benefit of a technologically integrated in-car network will only become rewarding with an Ethernet-based backbone, unifying several automotive domains in a single infrastructure. Today, there is remarkable interest in the IEEE 802.1 Audio/Video Bridging (AVB) protocol suite, that provides end-to-end performance guarantees in Ethernet networks. But for the strict timing requirements of automotive control-traffic, these guarantees are too weak. An extension of Ethernet AVB with synchronous time-triggered traffic can overcome these limitations. In this paper, we investigate the coexistence of synchronous and asynchronous traffic by experimentally adding time-triggered messages to the credit-based shaper of AVB in a straightforward way. Based on simulations and analytical evaluations, we quantify the impact of such integration concepts for a reasonable design range. Our results demonstrate the feasibility of a shaping strategy with concurrent AVB and time-triggered message, but show a significant impact of the schedule design on the asynchronous AVB streams. Based on our findings, we provide recommendations for configurations that can improve end-to-end network performance for in-car applications by over 100%.

Simulative assessments of IEEE 802.1 Ethernet AVB and Time-Triggered Ethernet for Advanced Driver Assistance Systems and in-car infotainment

Investigations into the usage of Ethernet in automobiles 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.

A scalable communication infrastructure for smart grid applications using multicast over public networks

The transition to regenerative energy resources paves the path from a small number of large power plants to a grid of highly distributed, heterogeneous small generators. To establish a Smart Grid it requires a scalable machine-to-machine communication that allows to control and coordinate millions of energy producing and consuming devices. In this work we contribute a future deployment concept of a scalable communication infrastructure for Smart Grids. Our proposal is based on group communication utilizing hybrid multicast over public networks. We show by real-world measurements that our approach achieves high scalability while also limiting end-to-end communication delay.

Performance Analysis of Time-Triggered Ether-Networks Using Off-the-Shelf-Components

The performance analysis and validation of distributed real-time systems poses significant challenges due to high accuracy requirements at the measurement tools. A fully synchronized time-scale at ultrafine granularity is not easy to generate. Even though there are several analyzer tools for standard switched Ethernet, these tools cannot be applied in time-triggered networks, since they do not meet the requirements of synchronized packet generation. This paper introduces a low cost and lightweight approach to measure end-to-end latency of time-triggered Ethernet traffic with off-the-shelf components. By using standard computer hardware and a real-time Linux Kernel, it is shown that measurement can be achieved in a resolution of microseconds. Furthermore, a validation with an Ethernet performance analyzer and a mathematical framework is presented to check the given results.

Consumer-oriented integration of smart homes and smart grids: A case for multicast-enabled Home Gateways?

Smart Home automation is pushing into the consumer market for several years, while at the same time energy companies are working on the deployment of Smart Grids. Although, a key idea of the energy transition is to integrate small energy devices at the consumers site, the potential benefits of Smart Home technologies for Smart Grids remain unused at large until now. In this work we present a concept for consumer-oriented integration of Smart Home devices into Smart Grid applications using multicast-enabled Home Gateways. An evaluation using standard consumer hardware confirms general feasibility and performance of our approach. Further, we deployed a measurement testbed in the metropolitan area of Hamburg to analyze typical end-to-end Internet connectivity of consumer households.

Demo: Real-time Ethernet in-car backbones: First insights into an automotive prototype

The communication infrastructure of todays automobiles forms a complex composition of heterogeneously interconnected components. At the same time, demands for higher bandwidth and low-latency communication are emerging from chassis control, camera based driver assistance and infotainment that cannot be accommodated by established technologies. A new approach towards a flexible highly scalable network is real-time Ethernet. The RECBAR research project develops and evaluates concepts and technologies for next-generation in-car backbones. In this demo we show a prototype based on a 2014 Volkswagen Golf 7 series car additionally equipped with high-bandwidth sensors, such as HD cameras and 3D laser scanners. The car uses a backbone network utilising time-triggered real-time Ethernet for the deterministic transmission of messages with hard realtime as well as rate-limiting and best-effort frames for messages with relaxed timing requirements. On the physical layer the setup utilises the OPEN Alliance 100Mbit/s BroadR-Reach (OABR or 100 BASE-T1) in addition to 100BASE-TX.

Software stacks for mixed-critical applications: Consolidating IEEE 802.1 AVB and time-triggered ethernet in next-generation automotive electronics

Real-time Ethernet variants are expected to build the future communication infrastructure in cars. First camera based driver assistance functions will communicate using IEEE 802.1 AVBs credit-based shaping. But for the strict timing requirements of automotive control-traffic, AVBs current timing guarantees are insufficient. The upcoming IEEE 802.1Qbv standard proposes synchronous time-triggered traffic to overcome these limitations. This paper presents a low footprint microcontroller based communication architecture, that supports both traffic classes in parallel while using standard hardware components. It allows first realistic performance analyses of coexistent traffic shaping strategies in a software based implementation.

Design of TDMA-based in-car networks: Applying multiprocessor scheduling strategies on time-triggered switched ethernet communication

Real-time Ethernet variants gain importance for communication infrastructure of various time-critical domains, such as in-car networks. Synchronous time-triggered traffic guarantees strict timing but requires a detailed schedule for all participants. Designing these schedules by hand is extensive work and with increasing network size almost impossible. In this paper, we contribute a mapping of the time-triggered network scheduling problem into the domain of multiprocessor scheduling. This set of transformation rules allows us to apply established scheduling algorithms as well as new strategies to organise time-triggered switched networks. Experimental results from a prototype implementation of a scheduling framework based on this mapping show the feasibility of our concept. The framework demonstrates a multiple solver approach that uses algorithms with different optimality criteria in parallel.