Vehicle Networks - SN00.19-P-0001-08S
Model all (CAR)
Networking
A new generation of E/E (electrical/electronic) architecture for Mercedes-Benz is being introduced in the form of STAR3. The architecture has a hierarchical structure and uses the following bus systems:
- CAN FD
- CAN 2.0
- FlexRay
- MOST
- LIN
- Automotive Ethernet (100BASE-T1)
CAN FD (flexible data transfer rate)
Large volumes of data and incredible diagnostic communication speeds in vehicles are key characteristics of the automotive industry. For decades, CAN has been a reliable bus system that has established itself as the standard. However, the performance of the classic CAN bus is no longer sufficient to meet current data transfer rate requirements.
CAN FD raises the limits of the CAN bus regarding the data transfer rate. Depending on the network topology, CAN FD can achieve data throughput around six times as high as that of the classic CAN bus in practice.
This increased efficiency is attained by means of the data field being enlarged from 8 bytes to as many as 64 bytes and the data transfer rate being improved by up to 2 Mbit/s during the transfer of useful data. Consequently, CAN FD is capable of meeting requirements to process much larger quantities of data, saving time and money as a result.
Advantages:
- Higher baud rate in the data field
- Larger payload per message (up to 64 bytes)
- Improved fault protection
For CAN FD, it is possible to use the same baud rate as with the conventional CAN bus system (CAN FD "slow"), or to use the accelerated data transfer rate in the data field (CAN FD "fast").
CAN 2.0
CAN 2.0 is an electric bus system for transmitting data over two cables.
CAN 2.0 consists of a twisted two-core data line that connects all CAN subscribers together in a parallel connection. Only CAN 2.0B with a 29-bit identifier is used in the STAR3 model series, unlike the predecessor CAN versions, which were assigned 11-bit identifiers.
FlexRay
The suspension FlexRay is a quick, deterministic and fault-tolerant bus system. Signal transmissions are based not on events but on permanently defined time windows. As a result, the bus load operates within a certain specified framework and, in contrast to other bus systems, excessive bus loads can be avoided.
The time windows are divided into static and dynamic sections. In order to improve the interference resistance, the suspension FlexRay consists of a twisted two-core data line. Each connected control unit is able to transmit or receive data.
MOST
The MOST150 bus (Media Oriented System Transport) is used to transfer synchronous audio data between the head unit and the amplifier. The bandwidth of 150 Mbit/s is sufficient to transfer all audio channels for the sound system without delay and at very high quality.
LIN
The Local Interconnect Network (LIN), also known as LIN bus, is a serial communication system for the networking of sensors and actuators. LIN is used where the bandwidth and versatility of CAN are not required. Examples of typical applications include networking within the comfort and convenience electrical system of a motor vehicle. The LIN with a data transfer rate of 19.2 kbit/s is used in the STAR3 model series.
Automotive Ethernet
Ethernet is increasingly being used as a fast bus system for applications such as driver assistance and infotainment systems in vehicles. As a "switched" network, it consists of physical point-to-point connections (P2P) between individual control units and switch elements integrated in them.
At 100 Mbit/s, the data transfer rate is significantly higher than it is in traditional automotive buses such as the CAN bus. This technology enables the development of driver assistance systems in which large amounts of data, e.g. from camera or radar signals, can be transferred reliably and with sufficiently short latencies.