Electrical Physical Layer Research Articles

Model-Based Simulation Framework for FlexRay Communication Systems

Automotive communication systems are complex distributed systems. The design of the electrical physical layer (EPL) is a challenging task. Many parameters affect the signal integrity on the analog bus and the combination of parameter variations can lead to effects (e.g., signal reflections) which degrade the signal and compromise the system reliability. Model-based simulations have been widely proposed as the solution for the design, testing and verification of FlexRay networks. This paper proposes a model-based framework for the design and evaluation of FlexRay communication systems. The framework includes the development of FlexRay system components, the design of different network topologies and the simulation and analysis of EPL. The proposed framework has been developed and possible applications have been figured out. Furthermore, the validation of the proposed approach has been addressed. The validation focuses on the accuracy of the simulations in representing the analog signal on the bus, as well as the accuracy in representing the network timing characteristics. The validation exhaustively explores the system design space, achieving a rigorous analysis of the approach reliability: simulations of 40 different network topologies and 1,264 frames have been evaluated, by comparing simulation results with hardware measurements. The results demonstrate that the proposed framework accurately represents the hardware behavior, and it can be an useful toll during the design and early verification of FlexRay communication networks. Due to the lack of a formal validation approach for the validation of the electrical physical layer, the validation is valuable for the FlexRay community.

Design and simulation of automotive communication networks: the challenges

In the last few years the amount of electronics inside cars has increased significantly. Current vehicles have implemented highly distributed electronic systems. The high number of Electronic Control Units (ECUs) and the high amount of data which must be exchanged require high bandwidth and reliable communication systems. Flexray is the communication protocol developed to fulfill these requirements. Due to its higher data rate and consequent bit length reduction, Flexray has more restrictive specifications than its precursor. One of the main goals of the communication network designers is on ensuring sufficient signal integrity at the analog bus. Behavioral simulations can be a useful tool for forecasting design problems and for supporting architecture decision. In this context, the paper explains the main reasons for analyzing the Electrical Physical Layer (EPL), lists the advantages of using behavioral simulations and provides a detailed overview of the challenges related to network design and verification. Moreover, it illustrates the impact of different aspects by way of dedicated use cases, such as topology decision and aging effects, on the signal integrity and therefore on communication quality and system robustness.

An Automated Model Based Design Flow for the Design of Robust FlexRay™ Networks

The enormous increase of vehicle functions realized through electronic components significantly impacts the communication within the vehicle network. More functions are requesting higher bandwidth; safety applications require a deterministic communication scheme to ensure reliable system performance even under harsh real world conditions. The new FlexRay vehicle communication standard addresses these requirements, with production networks already on the road. The high transmission rate introduces new challenges for network developers dealing with the implementation of the electrical physical layer as the dynamic behavior of the system cannot be predicted using manual calculations. The FlexRay physical layer working group has therefore established a simulation task force dealing with issues related to FlexRay's physical layer implementation. This task force has developed a virtual prototype based methodology to give network developers early verification of FlexRay physical layer implementations. Topology variants that depend on equipment in the vehicle can be investigated quickly with regard to their robustness under nominal and even worst case conditions. This paper introduces an automated, simulation-based methodology based on the guidelines and criteria defined in the FlexRay physical layer specification. In addition, this paper shows how close OEMs, IC vendors, conformance testers and software tool vendors must work together to define and realize a robust design methodology that is based on a virtual prototype implementation of the FlexRay network. BASICS OF FLEXRAY COMMUNICATION SYSTEMS When developers are dealing with In-Vehicle network implementations they have to ensure that both the software part as well as the electrical physical implementations is robust. The design and verification of both parts is usually very time-consuming. Sufficient testing is not possible using vehicle hardware prototypes since these are usually not available in the very early design stage when network concepts need to be evaluated in terms of their robustness. This paper shows how to design and verify the physical layer implementation of FlexRay systems through an automated and robust simulation based engineering method. The focus of this paper is on the verification methodology. Details about the FlexRay protocol and how to model them are comprehensively described in [4]. The FlexRay protocol and its electrical physical layer are specified in the FlexRay protocol and the Electrical Physical Layer (EPL) specification. These activities are standardized through the FlexRay consortium which is a society of all major automotive OEMs and their suppliers. Unlike the most popular CAN communication protocol, FlexRay is a time triggered communication protocol with a maximum transmission rate of 10 MBit/s. This is 10x higher than the theoretical transmission rate of CAN which is 1 MBit/s (in practical applications the transmission rate of CAN is usually below 1 MBit/s to ensure enough robustness). FlexRay allows arbitrary topology types like linear, star, or even hybrid as shown in figure 1. Figure 2 shows a possible future vehicle Figure 1: FlexRay topology (source FlexRay EPL) 2008-01-1031 An Automated Model Based Design Flow for the Design of Robust FlexRayTM Networks

Connector systems for Flexray networks application

The release of various Flexray Basic Specifications like the “Electrical Physical Layer Specification” gives us an advanced base for the development of Flexray network components. Tyco Electronics as a global supplier of passive electronic components and Flexray Consortium premium member was actively involved in the determination of Flexray specifications. This publication will show the new results of investigations and tests in the field of electrical connectors for Flexray automotive network applications.