Signal-Oriented ECUs in a Centralized Service-Oriented Architecture: Scalability of the Layered Software Architecture

Scientific Conference (2022, June 01)

The industry is quickly moving away from a function/signal-oriented architecture towards Service-Oriented Architectures (SOA). To carry-over legacy signal-oriented ECUs during the transition phase, Volvo ... [more ▼]

The industry is quickly moving away from a function/signal-oriented architecture towards Service-Oriented Architectures (SOA). To carry-over legacy signal-oriented ECUs during the transition phase, Volvo Cars has developed a layered software (SW) architecture based on the concepts of "device proxys" (i.e., one per legacy ECU), signal real-time database and service interface. This architecture, executing on the central computer on the TSN backbone, provides a clear separation of concerns between its components with a reduced additional complexity. In this presentation, we will review the main challenges faced in the integration of signal-oriented ECUs into SOA, and present the solutions explored at Volvo with a focus on layered SW architecture in the centralized E/E architecture and its 3 core components: o Device Proxies o Signal DataBase o Service Interface We then report on the performances of this architecture in terms of latencies and conclude on the maximum number of signal-oriented frames and legacy ECUs that can be handled. The performance evaluation is conducted by simulation, with sensitivity analysis to identify the performance bottlenecks. The E/E architecture under study is a prototype TSN-based central computing architecture targeted at next-generation models. The main questions that will be discussed throughout the presentation are 1) how to efficiently handle signal to service conversion? 2) The performance and the scalability of the SW architecture proposed and 3) the suitability of SOME/IP as the SOA protocol. [less ▲]

QoS-Predictable SOA on TSN: Insights from a Case-Study

Scientific Conference (2021, February 09)

This work is about the design and configuration of service-oriented communication on top of Ethernet TSN. The first objective is to present takeaways from the design and implementation of the Renault E/E ... [more ▼]

This work is about the design and configuration of service-oriented communication on top of Ethernet TSN. The first objective is to present takeaways from the design and implementation of the Renault E/E Service-Oriented Architecture (SOA) called FACE. In particular, we discuss technological, design and configuration choices made for the SOA, such as how to segment messages (UDP with multiple events, TCP, SOME/IP TP), and the technical possibilities to shape the transmission of the packets on the Ethernet network. The second objective is to study how to ensure the Quality of Service (QoS) required by services. Indeed, services introduce specific challenges, be it only the sheer amount of traffic they generate and if there is a growing body of experiences in the use of TSN QoS mechanisms most of what has been learned so far is mostly about meeting the requirements of individual streams. Less is known for services that involve the transmission of several, possibly segmented, messages with more complex transmission patterns. We show on the FACE architecture how SOME/IP messages were mapped to TSN QoS mechanisms in a manual then automated manner so as to meet the individual requirements of the services in terms of timing, and the system’s requirements in terms of memory usage. [less ▲]

Early-stage Bottleneck Identification and Removal in TSN Networks

Scientific Conference (2020, February 12)

There has been a pivotal change in the design of E/E architectures, which is that OEM cannot assume anymore that the functions, and thus the communication requirements, are known in advance and fixed over ... [more ▼]

There has been a pivotal change in the design of E/E architectures, which is that OEM cannot assume anymore that the functions, and thus the communication requirements, are known in advance and fixed over time. It has become crucial for OEMs to be in the position to add further functions and services during the lifetime of the vehicle: OEMs need to design E/E architectures that are future-proof. We propose design space exploration algorithms, which, by answering a series of design questions and proposing solutions to the designers, help to improve an automotive E/E architecture in several dimensions: performance, costs, reliability and extensibility. We start by estimating the total "capacity" of a baseline architecture, then, by removing bottlenecks, we obtain an "enhanced capacity" architecture, which is then optimized in terms of costs and reliability. The architecture is then further optimized in terms of costs and reliability. The work is conducted on Volvo's prototype centralized and domain-based E/E architecture. [less ▲]

A Hybrid Machine Learning and Schedulability Method for the Verification of TSN Networks

in 15th IEEE International Workshop on Factory Communication Systems (WFCS2019) (2019, March)

Machine learning (ML), and supervised learning in particular, can be used to learn what makes it hard for a network to be feasible and try to predict whether a network configuration will be feasible ... [more ▼]

Machine learning (ML), and supervised learning in particular, can be used to learn what makes it hard for a network to be feasible and try to predict whether a network configuration will be feasible without executing a conventional schedulability analysis. A disadvantage of ML-based timing verification with respect to schedulability analysis is the possibility of "false positives": configurations deemed feasible while they are not. In this work, in order to minimize the rate of false positives, we propose the use of a measure of the uncertainty of the prediction to drop it when the uncertainty is too high, and rely instead on schedulability analysis. In this hybrid verification strategy, the clear-cut decisions are taken by ML, while the more difficult ones are taken by a conventional schedulability analysis. Importantly, the trade-off achieved between prediction accuracy and computing time can be controlled. We apply this hybrid verification method to Ethernet TSN networks and obtain, for instance in the case of priority scheduling with 8 traffic classes, a 99% prediction accuracy with a speedup factor of 5.7 with respect to conventional schedulability analysis and a reduction of 46% of the false positives compared to ML alone. [less ▲]

On the use of supervised machine learning for assessing schedulability: application to Ethernet TSN

in 27th International Conference on Real-Time Networks and Systems (RTNS 2019) (2019)

In this work, we ask if Machine Learning (ML) can provide a viable alternative to conventional schedulability analysis to determine whether a real-time Ethernet network meets a set of timing constraints ... [more ▼]

In this work, we ask if Machine Learning (ML) can provide a viable alternative to conventional schedulability analysis to determine whether a real-time Ethernet network meets a set of timing constraints. Otherwise said, can an algorithm learn what makes it difficult for a system to be feasible and predict whether a configuration will be feasible without executing a schedulability analysis? To get insights into this question, we apply a standard supervised ML technique, k-nearest neighbors (k-NN), and compare its accuracy and running times against precise and approximate schedulability analyses developed in Network-Calculus. The experiments consider different TSN scheduling solutions based on priority levels combined for one of them with traffic shaping. The results obtained on an automotive network topology suggest that k-NN is efficient at predicting the feasibility of realistic TSN networks, with an accuracy ranging from 91.8% to 95.9% depending on the exact TSN scheduling mechanism and a speedup of 190 over schedulability analysis for 10^6 configurations. Unlike schedulability analysis, ML leads however to a certain rate "false positives'' (i.e., configurations deemed feasible while they are not). Nonetheless ML-based feasibility assessment techniques offer new trade-offs between accuracy and computation time that are especially interesting in contexts such as design-space exploration where false positives can be tolerated during the exploration process. [less ▲]

Pre-shaping Bursty Transmissions under IEEE802.1Q as a Simple and Efficient QoS Mechanism

in Proc. WCX World Congress Experience (2018, April)

The automotive industry is swiftly moving towards Ethernet as the high-speed communication network for in-vehicle communication. There is nonetheless a need for protocols that go beyond what standard ... [more ▼]

The automotive industry is swiftly moving towards Ethernet as the high-speed communication network for in-vehicle communication. There is nonetheless a need for protocols that go beyond what standard Ethernet has to offer in order to provide additional QoS to demanding applications such as ADAS systems or audio/video streaming. The main protocols currently considered for that purpose are IEEE802.1Q, AVB with the Credit Based Shaper mechanism (IEEE802.1Qav) and TSN with its Time-Aware Shaper (IEEE802.1Qbv). AVB/CBS and TSN/TAS both provide efficient QoS mechanisms and they can be used in a combined manner, which offers many possibilities to the designer. Their use however requires dedicated hardware and software components, and clock synchronization in the case of TAS. Previous studies have also shown that the efficiency of these protocols depends much on the application at hand and the value of the configuration parameters. In this work, we explore the use of “pre-shaping” strategies under IEEE802.1Q for bursty traffic such as audio/video streams as a simple and efficient alternative to AVB/CBS and TSN/TAS. Pre-shaping means inserting on the sender side “well-chosen” pauses between successive frames of a transmission burst (e.g., as it happens when sending a camera frame), all the other characteristics of the traffic remaining unchanged. We show on an automotive case-study how the use of pre-shaping for audio/video streams leads to a drastic reduction of the communication latencies for the best-effort streams while enabling to meet the timing constraints for the rest of the traffic. We then discuss the limitations of the pre-shaping mechanism and future works needed to facilitate its adoption. [less ▲]

Pre-shaping Bursty Transmissions under IEEE802.1Q as a Simple and Efficient QoS Mechanism

in SAE International Journal of Passenger Cars - Electronic and Electrical Systems (2018), 11(3), 197-204

The automotive industry is swiftly moving towards Ethernet as the high-speed communication network for in-vehicle communication. There is nonetheless a need for protocols that go beyond what standard ... [more ▼]

The automotive industry is swiftly moving towards Ethernet as the high-speed communication network for in-vehicle communication. There is nonetheless a need for protocols that go beyond what standard Ethernet has to offer in order to provide additional QoS to demanding applications such as ADAS systems (Advanced Driver-Assistance Systems) or audio/video streaming. The main protocols currently considered for that purpose are IEEE802.1Q, AVB with the Credit Based Shaper mechanism (IEEE802.1Qav) and TSN with its Time-Aware Shaper (IEEE802.1Qbv). AVB/CBS and TSN/TAS both provide efficient QoS mechanisms and they can be used in a combined manner, which offers many possibilities to the designer. Their use however requires dedicated hardware and software components, and clock synchronization in the case of TAS. Previous studies have also shown that the efficiency of these protocols depends much on the application at hand and the value of the configuration parameters. In this work, we explore the use of “pre-shaping” strategies under IEEE802.1Q for bursty traffic such as audio/video streams as a simple and efficient alternative to AVB/CBS and TSN/TAS. Pre-shaping means inserting on the sender side “well-chosen” pauses between successive frames of a transmission burst (e.g., as it happens when sending a camera frame), all the other characteristics of the traffic remaining unchanged. We show on an automotive case-study how the use of pre-shaping for audio/video streams leads to a drastic reduction of the communication latencies for the best-effort streams while enabling meeting the timing constraints for the rest of the traffic. We then discuss the limitations of the pre-shaping mechanism and what is needed to facilitate its adoption. [less ▲]

Timing verification of real­time automotive Ethernet networks: what can we expect from simulation?

Scientific Conference (2016, January 28)

Switched Ethernet is a technology that is profoundly reshaping automotive communication architectures as it did in other application domains such as avionics with the use of AFDX backbones. Early stage ... [more ▼]

Switched Ethernet is a technology that is profoundly reshaping automotive communication architectures as it did in other application domains such as avionics with the use of AFDX backbones. Early stage timing verification of critical embedded networks typically relies on simulation and worst-case schedulability analysis. When the modeling power of schedulability analysis is not sufficient, there are typically two options: either make pessimistic assumptions or ignore what cannot be modeled. Both options are unsatisfactory because they are either inefficient in terms of resource usage or potentially unsafe. To overcome those issues, we believe it is a good practice to use simulation models, which can be more realistic, along with schedulability analysis. The two basic questions that we aim to study here is what can we expect from simulation, and how to use it properly? This empirical study explores these questions on realistic case-studies and provides methodological guidelines for the use of simulation in the design of switched Ethernet networks. A broader objective of the study is to compare the outcomes of schedulability analyses and simulation, and conclude about the scope of usability of simulation in the design of critical Ethernet networks. [less ▲]

Timing verification of real-time automotive Ethernet networks: what can we expect from simulation?

Scientific Conference (2015, May 23)

Switched Ethernet is a technology that may profoundly reshape automotive communication architectures as it did in other application domains such as avionics with the use of AFDX backbones. Ethernet is ... [more ▼]

Switched Ethernet is a technology that may profoundly reshape automotive communication architectures as it did in other application domains such as avionics with the use of AFDX backbones. Ethernet is meant in vehicles not only for the support of infotainment applications but also to transmit time-sensitive data used for the real-time control of the vehicle and ADAS functions. In such use-cases, the temporal behavior of the communication architecture must be carefully validated. Early stage timing verification of critical embedded networks typically relies on simulation and worst-case schedulability analysis, which basically consists in building a mathematical model of the worst possible situations that can be encountered at run-time. The two basic questions that we aim to study here is what can we expect from simulation? And how to use it properly? This empirical study explores these questions and provides methodological guidelines for the use of simulation in the design of switched Ethernet networks. A broader objective of the study is to compare the outcomes of schedulability analyses and simulation, and conclude about the scope of usability of simulation in the design of critical Ethernet networks. [less ▲]

Integrating end-system frame scheduling for more accurate AFDX timing analysis

Scientific Conference (2014, February 07)

Avionics systems distributed on AFDX networks are subject to stringent real-time constraints that require guaranteeing the Worst-Case Traversal Time (WCTT) on the network for each of the data flows. Over ... [more ▼]

Avionics systems distributed on AFDX networks are subject to stringent real-time constraints that require guaranteeing the Worst-Case Traversal Time (WCTT) on the network for each of the data flows. Over the last 10 years, since the initial use of Network Calculus in certification, important progresses have been made in AFDX timing verification. The maximum pessimism for the latencies is now known to range from 10 to 25% on realistic systems. Further progresses towards more accurate timing analysis can still be made by considering additional temporal information. In this paper, we show that integrating the knowledge of the scheduling of the frames that is done within an end-system in the timing analysis enables to dramatically reduce the WCTT bounds computed by Network Calculus. Indeed, in our experiments performed on a realistic configuration provided by Thales Avionics, this technique reduces the WCTT upper bound by 40% on average over all flows. The reason is that the scheduling of the frames shapes the outgoing traffic, reducing thus peaks of load on the outgoing traffic , which can be accounted for in the timing analysis. Importantly, because the scheduling of the frames within the end-systems is in the scope of the network supplier, unlike the scheduling of tasks done at the application level, the approach presented here does not imply major changes in the design process. [less ▲]