IP and Ethernet in Motor Vehicles

April 26, 2013 //By Hans-Werner Schaal, Vector Informatik
IP and Ethernet in Motor Vehicles
Until just a few years ago, the prevailing opinion was that Ethernet would never be used for in-vehicle applications, with the exception of diagnostic access. Soon, however, camera-based driver assistance systems will be the first applications to utilize Ethernet technology as a system network. This presents new challenges to automotive OEMs, suppliers and development tool producers, because the Internet Protocol and Ethernet represent a new network technology for motor vehicles. Nonetheless, many of the issues can already be solved.

After the debut of the CAN bus in the Mercedes S-Class in 1991, the LIN, MOST and FlexRay bus systems also became established in the motor vehicle. Today, CAN continues to be used in automotive network architectures in all domains (from powertrain to body). LIN bus technology is ideal for simple and cost-effective data exchange of noncritical signals in the convenience area. Where bandwidths and real-time requirements run into limitations, CAN is replaced by FlexRay or MOST – in cases where it is economically justifiable. In today's vehicles, one often finds all of the named bus systems, segmented and networked via gateways.

Motivation for Ethernet

Ethernet has long been an established standard technology in office communications, industrial engineering (ODVA standards, Ethernet/IP and ProfiNet) and in the aerospace industry (AFDX). In the automotive field, Ethernet had already proven itself in the vehicle for diagnostic access. In recent years, other use areas have increasingly been discussed in automotive research and development departments, because Ethernet’s scalable bandwidth and flexibility spoke strongly in its favor. Nonetheless, a suitable and economical wiring technology was lacking for the motor vehicle.

Currently, the main drivers for Ethernet usage in the vehicle are camera-based driver assistance systems. In camera applications in the vehicle, LVDS technology (Low Voltage Differential Signaling) has been used until now. The shielded cable that is generally used there does indeed assure electromagnetic compatibility, but it is expensive by industry measures, and it is very impractical to install in the motor vehicle. Most recently, a physical layer is available that offers full-duplex transmission at 100 Mbit/s on a CAN-like, two-wire cable (unshielded twisted pair), and in the opinion of various publications it is suitable for use in the motor vehicle [1], [2], [3].

Requirements of an IP development tool

First, known requirements of previous bus systems still apply to the development tool. Initially, what is required is a detailed protocol analysis with stimulation option that

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