Ye-Qiong Song

Trends in Automotive Communication Systems

The use of networks for communications between the electronic control units (ECU) of a vehicle in production cars dates from the beginning of the 1990s. The specific requirements of the different car domains have led to the development of a large number of automotive networks such as Local Interconnect Network, J1850, CAN, TTP/C, FlexRay, media-oriented system transport, IDB1394, etc. This paper first introduces the context of in-vehicle embedded systems and, in particular, the requirements imposed on the communication systems. Then, a comprehensive review of the most widely used automotive networks, as well as the emerging ones, is given. Next, the current efforts of the automotive industry on middleware technologies, which may be of great help in mastering the heterogeneity, are reviewed. Finally, we highlight future trends in the development of automotive communication systems.

Worst-case deadline failure probability in real-time applications distributed over controller area network

Real-time applications distributed over the controller area network (CAN) are generally characterised by stringent temporal and dependability constraints. Our goal is to take account of transmission errors in the design of such applications because the consequences of such disturbances are potentially disastrous. In this study, the concept of worst-case deadline failure probability (WCDFP) is introduced. The motivation of the probabilistic approach is that, in practice, the number of errors occurring during a given time period can with difficulty be bounded. To evaluate the WCDFP, we propose, on the one hand, a method of computing for each message the tolerable threshold of transmission errors under which timing constraints are guaranteed to be met. On the other hand, we also suggest an error model enabling us to consider both error frequency and error gravity. Our error model follows a generalized Poisson process and its stochastic parameters have been derived. We then propose a numerically efficient algorithm to compute the probabilities and apply the analysis to an industrial case-study of the automotive field.

Switched Ethernet for real-time industrial communication: modelling and message buffering delay evaluation

Switched Ethernet is now considered as an attractive enabling technology for supporting factory communication needs. This paper deals with the modelling of an Ethernet switch and the performance evaluation of its real-time features. For multiple priority periodic and single priority aperiodic input traffic, methods for calculating respectively the worst case buffering delay and buffering delay probability distribution are given, allowing thus to estimate both hard real-time and soft real-time guarantees. Moreover for aperiodic traffic, Binomial input is compared to the Poisson one and we numerically showed that the Poisson case could be used as an approximation model to upper bounds of the buffering delay of the actual switch. This allowed us to further consider the priorities for buffering delay evaluation using classic results of M/G/1 queue.

Evaluation and improvement of response time bounds for real-time applications under non-pre-emptive Fixed Priority Scheduling

Real-time applications must be guaranteed with a bounded response time. The two main approaches for computing the upper bounds are worst-case schedulability analysis and Network Calculus, both of which are based on the analysis of a deterministic majoring trajectory. The first approach is issued from the results of Liu and Layland and gives what is called the worst-case response time for a given set of periodic tasks scheduled with fixed priority. The second approach, proposed by Cruz, gives an upper bound on delay for a set of (σ, ρ)-bounded message flows. Both approaches could be used to evaluate the end-to-end delay bound in the industrial switched Ethernet (the target application) in which the main traffic is periodic with or without jitters. However, the use of either the worst-case trajectory or (σ, ρ) trajectory produces overestimated delay bounds. Therefore, to minimize this overestimation, the paper proposes a comparative study of the delay bounds evaluated by both approaches for periodic (with or without jitters) arrival processes under Fixed Priority Scheduling. For this purpose, a relationship is given between jitter and the maximum burst size for an optimal transposition from the classical task model to the (σ, ρ)-constrained model. The paper also proposes a hybrid method to reduce the upper bound given Network Calculus for a multihop network. Numerical studies show the advantage of the method for reducing the estimation of the buffering requirement in each network element.

Analysis and simulation methods for performance evaluation of a multiple networked embedded architecture

This paper deals with the modeling and the validation of multiple networked embedded computer systems supporting in-vehicle applications. In this context, the authors developed a modular modeling and simulation technique. This approach allowed the development of reusable component models with clearly defined interfaces. The building of a whole application model is then obtained by the integration of these components, so that model construction and result analysis are made easy. In fact, thanks to the formal definition of components, interfaces, and composition rules, this step is automatically achieved. In the context of the CAROSSE project, we implemented this methodology in the Carosse-Perf tool. Herein, the authors detail the methodology together with its modeling principles and the resulting definition of basic components and interfaces. Finally, they apply it to a case study drawn from a PSA Peugeot-Citroen application.

Providing Real-Time Applications With Graceful Degradation of QoS and Fault Tolerance According to

The

(m, k)

(m, k)

-Firm Model

-firm model has recently drawn a lot of attention. It provides a flexible real-time system with graceful degradation of the quality of service (QoS), thus achieving the fault tolerance in case of system overload. In this paper, we focus on the distance-based priority (DBP) algorithm as it presents the interesting feature of dynamically assigning the priorities according to the systems current state (QoS-aware scheduling). However, DBP cannot readily be used for systems requiring a deterministic

Quantitative evaluation of the safety of X-by-Wire architecture subject to EMI perturbations

(m, k)

Medical and Home Automation Sensor Networks for Senior Citizens Telehomecare

-firm guarantee since the schedulability analysis was not done in the original proposition. In this paper, a sufficient schedulability condition is given to deterministically guarantee a set of periodic or sporadic activities (jobs) sharing a common non-preemptive server. This condition is applied to two case studies showing its practical usefulness for both bandwidth dimensioning of the communication system providing graceful degradation of QoS and the task scheduling in an in-vehicle embedded system allowing fault tolerance.