Civil Engineering Reference
In-Depth Information
Fig. 2.30
Logical versus physical network architecture
This chapter focuses on the physical network architecture or “physical layer”. Due
to the increasing complexity and size of automotive networks over the past years,
more rigorous exploration and analysis of the physical layer have become neces-
sary. In order to address this very challenging task, simulation-based methodologies
have proven to be the methods of choice. The technical necessity for simulation-
based methodologies is driven by the following issues typically encountered by the
network developer during the development process:
• Complexity (e.g. number of ECUs and wiring harness)
• Variety of vehicle platform variants
• Reproducibility of test conditions (e.g. worst case)
The complexity of modern in-vehicle networking systems makes it extremely diffi-
cult for developers to derive any a priori conclusions about the correct functionality
and robustness of the system before prototyping. This problem will be explained
by means of an example. Figure
2.30
depicts a networking system composed of
six ECUs that are connected through a high-speed CAN bus. If one of the ECUs
is transmitting a data stream to the other ECUs in the network, it is important for
the network developer to know what data have been sampled by each of the receiv-
ers. The reasons for problems during communication are particularly related to the
analog electrical signal behaviour between the different ECUs. Although CAN is a
digital communication protocol, the electrical behaviour along the bus and between
the ECUs is analog. This behaviour is significantly impacted by the following ele-
ments:
